mtd: nand: Add page argument to write_page() etc.

[people/ms/u-boot.git] / drivers / mtd / nand / nand_base.c

/*
 *  drivers/mtd/nand.c
 *
 *  Overview:
 *   This is the generic MTD driver for NAND flash devices. It should be
 *   capable of working with almost all NAND chips currently available.
 *
 *      Additional technical information is available on
 *      http://www.linux-mtd.infradead.org/doc/nand.html
 *
 *  Copyright (C) 2000 Steven J. Hill (sjhill@realitydiluted.com)
 *                2002-2006 Thomas Gleixner (tglx@linutronix.de)
 *
 *  Credits:
 *      David Woodhouse for adding multichip support
 *
 *      Aleph One Ltd. and Toby Churchill Ltd. for supporting the
 *      rework for 2K page size chips
 *
 *  TODO:
 *      Enable cached programming for 2k page size chips
 *      Check, if mtd->ecctype should be set to MTD_ECC_HW
 *      if we have HW ECC support.
 *      BBT table is not serialized, has to be fixed
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License version 2 as
 * published by the Free Software Foundation.
 *
 */

#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
#include <common.h>
#include <malloc.h>
#include <watchdog.h>
#include <linux/err.h>
#include <linux/compat.h>
#include <linux/mtd/mtd.h>
#include <linux/mtd/nand.h>
#include <linux/mtd/nand_ecc.h>
#include <linux/mtd/nand_bch.h>
#ifdef CONFIG_MTD_PARTITIONS
#include <linux/mtd/partitions.h>
#endif
#include <asm/io.h>
#include <asm/errno.h>

static bool is_module_text_address(unsigned long addr) {return 0;}

/* Define default oob placement schemes for large and small page devices */
static struct nand_ecclayout nand_oob_8 = {
        .eccbytes = 3,
        .eccpos = {0, 1, 2},
        .oobfree = {
                {.offset = 3,
                 .length = 2},
                {.offset = 6,
                 .length = 2} }
};

static struct nand_ecclayout nand_oob_16 = {
        .eccbytes = 6,
        .eccpos = {0, 1, 2, 3, 6, 7},
        .oobfree = {
                {.offset = 8,
                 . length = 8} }
};

static struct nand_ecclayout nand_oob_64 = {
        .eccbytes = 24,
        .eccpos = {
                   40, 41, 42, 43, 44, 45, 46, 47,
                   48, 49, 50, 51, 52, 53, 54, 55,
                   56, 57, 58, 59, 60, 61, 62, 63},
        .oobfree = {
                {.offset = 2,
                 .length = 38} }
};

static struct nand_ecclayout nand_oob_128 = {
        .eccbytes = 48,
        .eccpos = {
                   80, 81, 82, 83, 84, 85, 86, 87,
                   88, 89, 90, 91, 92, 93, 94, 95,
                   96, 97, 98, 99, 100, 101, 102, 103,
                   104, 105, 106, 107, 108, 109, 110, 111,
                   112, 113, 114, 115, 116, 117, 118, 119,
                   120, 121, 122, 123, 124, 125, 126, 127},
        .oobfree = {
                {.offset = 2,
                 .length = 78} }
};

static int nand_get_device(struct mtd_info *mtd, int new_state);

static int nand_do_write_oob(struct mtd_info *mtd, loff_t to,
                             struct mtd_oob_ops *ops);

/*
 * For devices which display every fart in the system on a separate LED. Is
 * compiled away when LED support is disabled.
 */
DEFINE_LED_TRIGGER(nand_led_trigger);

static int check_offs_len(struct mtd_info *mtd,
                                        loff_t ofs, uint64_t len)
{
        struct nand_chip *chip = mtd_to_nand(mtd);
        int ret = 0;

        /* Start address must align on block boundary */
        if (ofs & ((1ULL << chip->phys_erase_shift) - 1)) {
                pr_debug("%s: unaligned address\n", __func__);
                ret = -EINVAL;
        }

        /* Length must align on block boundary */
        if (len & ((1ULL << chip->phys_erase_shift) - 1)) {
                pr_debug("%s: length not block aligned\n", __func__);
                ret = -EINVAL;
        }

        return ret;
}

/**
 * nand_release_device - [GENERIC] release chip
 * @mtd: MTD device structure
 *
 * Release chip lock and wake up anyone waiting on the device.
 */
static void nand_release_device(struct mtd_info *mtd)
{
        struct nand_chip *chip = mtd_to_nand(mtd);

        /* De-select the NAND device */
        chip->select_chip(mtd, -1);
}

/**
 * nand_read_byte - [DEFAULT] read one byte from the chip
 * @mtd: MTD device structure
 *
 * Default read function for 8bit buswidth
 */
uint8_t nand_read_byte(struct mtd_info *mtd)
{
        struct nand_chip *chip = mtd_to_nand(mtd);
        return readb(chip->IO_ADDR_R);
}

/**
 * nand_read_byte16 - [DEFAULT] read one byte endianness aware from the chip
 * @mtd: MTD device structure
 *
 * Default read function for 16bit buswidth with endianness conversion.
 *
 */
static uint8_t nand_read_byte16(struct mtd_info *mtd)
{
        struct nand_chip *chip = mtd_to_nand(mtd);
        return (uint8_t) cpu_to_le16(readw(chip->IO_ADDR_R));
}

/**
 * nand_read_word - [DEFAULT] read one word from the chip
 * @mtd: MTD device structure
 *
 * Default read function for 16bit buswidth without endianness conversion.
 */
static u16 nand_read_word(struct mtd_info *mtd)
{
        struct nand_chip *chip = mtd_to_nand(mtd);
        return readw(chip->IO_ADDR_R);
}

/**
 * nand_select_chip - [DEFAULT] control CE line
 * @mtd: MTD device structure
 * @chipnr: chipnumber to select, -1 for deselect
 *
 * Default select function for 1 chip devices.
 */
static void nand_select_chip(struct mtd_info *mtd, int chipnr)
{
        struct nand_chip *chip = mtd_to_nand(mtd);

        switch (chipnr) {
        case -1:
                chip->cmd_ctrl(mtd, NAND_CMD_NONE, 0 | NAND_CTRL_CHANGE);
                break;
        case 0:
                break;

        default:
                BUG();
        }
}

/**
 * nand_write_byte - [DEFAULT] write single byte to chip
 * @mtd: MTD device structure
 * @byte: value to write
 *
 * Default function to write a byte to I/O[7:0]
 */
static void nand_write_byte(struct mtd_info *mtd, uint8_t byte)
{
        struct nand_chip *chip = mtd_to_nand(mtd);

        chip->write_buf(mtd, &byte, 1);
}

/**
 * nand_write_byte16 - [DEFAULT] write single byte to a chip with width 16
 * @mtd: MTD device structure
 * @byte: value to write
 *
 * Default function to write a byte to I/O[7:0] on a 16-bit wide chip.
 */
static void nand_write_byte16(struct mtd_info *mtd, uint8_t byte)
{
        struct nand_chip *chip = mtd_to_nand(mtd);
        uint16_t word = byte;

        /*
         * It's not entirely clear what should happen to I/O[15:8] when writing
         * a byte. The ONFi spec (Revision 3.1; 2012-09-19, Section 2.16) reads:
         *
         *    When the host supports a 16-bit bus width, only data is
         *    transferred at the 16-bit width. All address and command line
         *    transfers shall use only the lower 8-bits of the data bus. During
         *    command transfers, the host may place any value on the upper
         *    8-bits of the data bus. During address transfers, the host shall
         *    set the upper 8-bits of the data bus to 00h.
         *
         * One user of the write_byte callback is nand_onfi_set_features. The
         * four parameters are specified to be written to I/O[7:0], but this is
         * neither an address nor a command transfer. Let's assume a 0 on the
         * upper I/O lines is OK.
         */
        chip->write_buf(mtd, (uint8_t *)&word, 2);
}

#if !defined(CONFIG_BLACKFIN)
static void iowrite8_rep(void *addr, const uint8_t *buf, int len)
{
        int i;

        for (i = 0; i < len; i++)
                writeb(buf[i], addr);
}
static void ioread8_rep(void *addr, uint8_t *buf, int len)
{
        int i;

        for (i = 0; i < len; i++)
                buf[i] = readb(addr);
}

static void ioread16_rep(void *addr, void *buf, int len)
{
        int i;
        u16 *p = (u16 *) buf;

        for (i = 0; i < len; i++)
                p[i] = readw(addr);
}

static void iowrite16_rep(void *addr, void *buf, int len)
{
        int i;
        u16 *p = (u16 *) buf;

        for (i = 0; i < len; i++)
                writew(p[i], addr);
}
#endif

/**
 * nand_write_buf - [DEFAULT] write buffer to chip
 * @mtd: MTD device structure
 * @buf: data buffer
 * @len: number of bytes to write
 *
 * Default write function for 8bit buswidth.
 */
void nand_write_buf(struct mtd_info *mtd, const uint8_t *buf, int len)
{
        struct nand_chip *chip = mtd_to_nand(mtd);

        iowrite8_rep(chip->IO_ADDR_W, buf, len);
}

/**
 * nand_read_buf - [DEFAULT] read chip data into buffer
 * @mtd: MTD device structure
 * @buf: buffer to store date
 * @len: number of bytes to read
 *
 * Default read function for 8bit buswidth.
 */
void nand_read_buf(struct mtd_info *mtd, uint8_t *buf, int len)
{
        struct nand_chip *chip = mtd_to_nand(mtd);

        ioread8_rep(chip->IO_ADDR_R, buf, len);
}

/**
 * nand_write_buf16 - [DEFAULT] write buffer to chip
 * @mtd: MTD device structure
 * @buf: data buffer
 * @len: number of bytes to write
 *
 * Default write function for 16bit buswidth.
 */
void nand_write_buf16(struct mtd_info *mtd, const uint8_t *buf, int len)
{
        struct nand_chip *chip = mtd_to_nand(mtd);
        u16 *p = (u16 *) buf;

        iowrite16_rep(chip->IO_ADDR_W, p, len >> 1);
}

/**
 * nand_read_buf16 - [DEFAULT] read chip data into buffer
 * @mtd: MTD device structure
 * @buf: buffer to store date
 * @len: number of bytes to read
 *
 * Default read function for 16bit buswidth.
 */
void nand_read_buf16(struct mtd_info *mtd, uint8_t *buf, int len)
{
        struct nand_chip *chip = mtd_to_nand(mtd);
        u16 *p = (u16 *) buf;

        ioread16_rep(chip->IO_ADDR_R, p, len >> 1);
}

/**
 * nand_block_bad - [DEFAULT] Read bad block marker from the chip
 * @mtd: MTD device structure
 * @ofs: offset from device start
 * @getchip: 0, if the chip is already selected
 *
 * Check, if the block is bad.
 */
static int nand_block_bad(struct mtd_info *mtd, loff_t ofs, int getchip)
{
        int page, chipnr, res = 0, i = 0;
        struct nand_chip *chip = mtd_to_nand(mtd);
        u16 bad;

        if (chip->bbt_options & NAND_BBT_SCANLASTPAGE)
                ofs += mtd->erasesize - mtd->writesize;

        page = (int)(ofs >> chip->page_shift) & chip->pagemask;

        if (getchip) {
                chipnr = (int)(ofs >> chip->chip_shift);

                nand_get_device(mtd, FL_READING);

                /* Select the NAND device */
                chip->select_chip(mtd, chipnr);
        }

        do {
                if (chip->options & NAND_BUSWIDTH_16) {
                        chip->cmdfunc(mtd, NAND_CMD_READOOB,
                                        chip->badblockpos & 0xFE, page);
                        bad = cpu_to_le16(chip->read_word(mtd));
                        if (chip->badblockpos & 0x1)
                                bad >>= 8;
                        else
                                bad &= 0xFF;
                } else {
                        chip->cmdfunc(mtd, NAND_CMD_READOOB, chip->badblockpos,
                                        page);
                        bad = chip->read_byte(mtd);
                }

                if (likely(chip->badblockbits == 8))
                        res = bad != 0xFF;
                else
                        res = hweight8(bad) < chip->badblockbits;
                ofs += mtd->writesize;
                page = (int)(ofs >> chip->page_shift) & chip->pagemask;
                i++;
        } while (!res && i < 2 && (chip->bbt_options & NAND_BBT_SCAN2NDPAGE));

        if (getchip) {
                chip->select_chip(mtd, -1);
                nand_release_device(mtd);
        }

        return res;
}

/**
 * nand_default_block_markbad - [DEFAULT] mark a block bad via bad block marker
 * @mtd: MTD device structure
 * @ofs: offset from device start
 *
 * This is the default implementation, which can be overridden by a hardware
 * specific driver. It provides the details for writing a bad block marker to a
 * block.
 */
static int nand_default_block_markbad(struct mtd_info *mtd, loff_t ofs)
{
        struct nand_chip *chip = mtd_to_nand(mtd);
        struct mtd_oob_ops ops;
        uint8_t buf[2] = { 0, 0 };
        int ret = 0, res, i = 0;

        memset(&ops, 0, sizeof(ops));
        ops.oobbuf = buf;
        ops.ooboffs = chip->badblockpos;
        if (chip->options & NAND_BUSWIDTH_16) {
                ops.ooboffs &= ~0x01;
                ops.len = ops.ooblen = 2;
        } else {
                ops.len = ops.ooblen = 1;
        }
        ops.mode = MTD_OPS_PLACE_OOB;

        /* Write to first/last page(s) if necessary */
        if (chip->bbt_options & NAND_BBT_SCANLASTPAGE)
                ofs += mtd->erasesize - mtd->writesize;
        do {
                res = nand_do_write_oob(mtd, ofs, &ops);
                if (!ret)
                        ret = res;

                i++;
                ofs += mtd->writesize;
        } while ((chip->bbt_options & NAND_BBT_SCAN2NDPAGE) && i < 2);

        return ret;
}

/**
 * nand_block_markbad_lowlevel - mark a block bad
 * @mtd: MTD device structure
 * @ofs: offset from device start
 *
 * This function performs the generic NAND bad block marking steps (i.e., bad
 * block table(s) and/or marker(s)). We only allow the hardware driver to
 * specify how to write bad block markers to OOB (chip->block_markbad).
 *
 * We try operations in the following order:
 *  (1) erase the affected block, to allow OOB marker to be written cleanly
 *  (2) write bad block marker to OOB area of affected block (unless flag
 *      NAND_BBT_NO_OOB_BBM is present)
 *  (3) update the BBT
 * Note that we retain the first error encountered in (2) or (3), finish the
 * procedures, and dump the error in the end.
*/
static int nand_block_markbad_lowlevel(struct mtd_info *mtd, loff_t ofs)
{
        struct nand_chip *chip = mtd_to_nand(mtd);
        int res, ret = 0;

        if (!(chip->bbt_options & NAND_BBT_NO_OOB_BBM)) {
                struct erase_info einfo;

                /* Attempt erase before marking OOB */
                memset(&einfo, 0, sizeof(einfo));
                einfo.mtd = mtd;
                einfo.addr = ofs;
                einfo.len = 1ULL << chip->phys_erase_shift;
                nand_erase_nand(mtd, &einfo, 0);

                /* Write bad block marker to OOB */
                nand_get_device(mtd, FL_WRITING);
                ret = chip->block_markbad(mtd, ofs);
                nand_release_device(mtd);
        }

        /* Mark block bad in BBT */
        if (chip->bbt) {
                res = nand_markbad_bbt(mtd, ofs);
                if (!ret)
                        ret = res;
        }

        if (!ret)
                mtd->ecc_stats.badblocks++;

        return ret;
}

/**
 * nand_check_wp - [GENERIC] check if the chip is write protected
 * @mtd: MTD device structure
 *
 * Check, if the device is write protected. The function expects, that the
 * device is already selected.
 */
static int nand_check_wp(struct mtd_info *mtd)
{
        struct nand_chip *chip = mtd_to_nand(mtd);

        /* Broken xD cards report WP despite being writable */
        if (chip->options & NAND_BROKEN_XD)
                return 0;

        /* Check the WP bit */
        chip->cmdfunc(mtd, NAND_CMD_STATUS, -1, -1);
        return (chip->read_byte(mtd) & NAND_STATUS_WP) ? 0 : 1;
}

/**
 * nand_block_isreserved - [GENERIC] Check if a block is marked reserved.
 * @mtd: MTD device structure
 * @ofs: offset from device start
 *
 * Check if the block is marked as reserved.
 */
static int nand_block_isreserved(struct mtd_info *mtd, loff_t ofs)
{
        struct nand_chip *chip = mtd_to_nand(mtd);

        if (!chip->bbt)
                return 0;
        /* Return info from the table */
        return nand_isreserved_bbt(mtd, ofs);
}

/**
 * nand_block_checkbad - [GENERIC] Check if a block is marked bad
 * @mtd: MTD device structure
 * @ofs: offset from device start
 * @getchip: 0, if the chip is already selected
 * @allowbbt: 1, if its allowed to access the bbt area
 *
 * Check, if the block is bad. Either by reading the bad block table or
 * calling of the scan function.
 */
static int nand_block_checkbad(struct mtd_info *mtd, loff_t ofs, int getchip,
                               int allowbbt)
{
        struct nand_chip *chip = mtd_to_nand(mtd);

        if (!(chip->options & NAND_SKIP_BBTSCAN) &&
            !(chip->options & NAND_BBT_SCANNED)) {
                chip->options |= NAND_BBT_SCANNED;
                chip->scan_bbt(mtd);
        }

        if (!chip->bbt)
                return chip->block_bad(mtd, ofs, getchip);

        /* Return info from the table */
        return nand_isbad_bbt(mtd, ofs, allowbbt);
}

/* Wait for the ready pin, after a command. The timeout is caught later. */
void nand_wait_ready(struct mtd_info *mtd)
{
        struct nand_chip *chip = mtd_to_nand(mtd);
        u32 timeo = (CONFIG_SYS_HZ * 20) / 1000;
        u32 time_start;

        time_start = get_timer(0);
        /* Wait until command is processed or timeout occurs */
        while (get_timer(time_start) < timeo) {
                if (chip->dev_ready)
                        if (chip->dev_ready(mtd))
                                break;
        }
}
EXPORT_SYMBOL_GPL(nand_wait_ready);

/**
 * nand_wait_status_ready - [GENERIC] Wait for the ready status after commands.
 * @mtd: MTD device structure
 * @timeo: Timeout in ms
 *
 * Wait for status ready (i.e. command done) or timeout.
 */
static void nand_wait_status_ready(struct mtd_info *mtd, unsigned long timeo)
{
        register struct nand_chip *chip = mtd_to_nand(mtd);
        u32 time_start;

        timeo = (CONFIG_SYS_HZ * timeo) / 1000;
        time_start = get_timer(0);
        while (get_timer(time_start) < timeo) {
                if ((chip->read_byte(mtd) & NAND_STATUS_READY))
                        break;
                WATCHDOG_RESET();
        }
};

/**
 * nand_command - [DEFAULT] Send command to NAND device
 * @mtd: MTD device structure
 * @command: the command to be sent
 * @column: the column address for this command, -1 if none
 * @page_addr: the page address for this command, -1 if none
 *
 * Send command to NAND device. This function is used for small page devices
 * (512 Bytes per page).
 */
static void nand_command(struct mtd_info *mtd, unsigned int command,
                         int column, int page_addr)
{
        register struct nand_chip *chip = mtd_to_nand(mtd);
        int ctrl = NAND_CTRL_CLE | NAND_CTRL_CHANGE;

        /* Write out the command to the device */
        if (command == NAND_CMD_SEQIN) {
                int readcmd;

                if (column >= mtd->writesize) {
                        /* OOB area */
                        column -= mtd->writesize;
                        readcmd = NAND_CMD_READOOB;
                } else if (column < 256) {
                        /* First 256 bytes --> READ0 */
                        readcmd = NAND_CMD_READ0;
                } else {
                        column -= 256;
                        readcmd = NAND_CMD_READ1;
                }
                chip->cmd_ctrl(mtd, readcmd, ctrl);
                ctrl &= ~NAND_CTRL_CHANGE;
        }
        chip->cmd_ctrl(mtd, command, ctrl);

        /* Address cycle, when necessary */
        ctrl = NAND_CTRL_ALE | NAND_CTRL_CHANGE;
        /* Serially input address */
        if (column != -1) {
                /* Adjust columns for 16 bit buswidth */
                if (chip->options & NAND_BUSWIDTH_16 &&
                                !nand_opcode_8bits(command))
                        column >>= 1;
                chip->cmd_ctrl(mtd, column, ctrl);
                ctrl &= ~NAND_CTRL_CHANGE;
        }
        if (page_addr != -1) {
                chip->cmd_ctrl(mtd, page_addr, ctrl);
                ctrl &= ~NAND_CTRL_CHANGE;
                chip->cmd_ctrl(mtd, page_addr >> 8, ctrl);
                /* One more address cycle for devices > 32MiB */
                if (chip->chipsize > (32 << 20))
                        chip->cmd_ctrl(mtd, page_addr >> 16, ctrl);
        }
        chip->cmd_ctrl(mtd, NAND_CMD_NONE, NAND_NCE | NAND_CTRL_CHANGE);

        /*
         * Program and erase have their own busy handlers status and sequential
         * in needs no delay
         */
        switch (command) {

        case NAND_CMD_PAGEPROG:
        case NAND_CMD_ERASE1:
        case NAND_CMD_ERASE2:
        case NAND_CMD_SEQIN:
        case NAND_CMD_STATUS:
                return;

        case NAND_CMD_RESET:
                if (chip->dev_ready)
                        break;
                udelay(chip->chip_delay);
                chip->cmd_ctrl(mtd, NAND_CMD_STATUS,
                               NAND_CTRL_CLE | NAND_CTRL_CHANGE);
                chip->cmd_ctrl(mtd,
                               NAND_CMD_NONE, NAND_NCE | NAND_CTRL_CHANGE);
                /* EZ-NAND can take upto 250ms as per ONFi v4.0 */
                nand_wait_status_ready(mtd, 250);
                return;

                /* This applies to read commands */
        default:
                /*
                 * If we don't have access to the busy pin, we apply the given
                 * command delay
                 */
                if (!chip->dev_ready) {
                        udelay(chip->chip_delay);
                        return;
                }
        }
        /*
         * Apply this short delay always to ensure that we do wait tWB in
         * any case on any machine.
         */
        ndelay(100);

        nand_wait_ready(mtd);
}

/**
 * nand_command_lp - [DEFAULT] Send command to NAND large page device
 * @mtd: MTD device structure
 * @command: the command to be sent
 * @column: the column address for this command, -1 if none
 * @page_addr: the page address for this command, -1 if none
 *
 * Send command to NAND device. This is the version for the new large page
 * devices. We don't have the separate regions as we have in the small page
 * devices. We must emulate NAND_CMD_READOOB to keep the code compatible.
 */
static void nand_command_lp(struct mtd_info *mtd, unsigned int command,
                            int column, int page_addr)
{
        register struct nand_chip *chip = mtd_to_nand(mtd);

        /* Emulate NAND_CMD_READOOB */
        if (command == NAND_CMD_READOOB) {
                column += mtd->writesize;
                command = NAND_CMD_READ0;
        }

        /* Command latch cycle */
        chip->cmd_ctrl(mtd, command, NAND_NCE | NAND_CLE | NAND_CTRL_CHANGE);

        if (column != -1 || page_addr != -1) {
                int ctrl = NAND_CTRL_CHANGE | NAND_NCE | NAND_ALE;

                /* Serially input address */
                if (column != -1) {
                        /* Adjust columns for 16 bit buswidth */
                        if (chip->options & NAND_BUSWIDTH_16 &&
                                        !nand_opcode_8bits(command))
                                column >>= 1;
                        chip->cmd_ctrl(mtd, column, ctrl);
                        ctrl &= ~NAND_CTRL_CHANGE;
                        chip->cmd_ctrl(mtd, column >> 8, ctrl);
                }
                if (page_addr != -1) {
                        chip->cmd_ctrl(mtd, page_addr, ctrl);
                        chip->cmd_ctrl(mtd, page_addr >> 8,
                                       NAND_NCE | NAND_ALE);
                        /* One more address cycle for devices > 128MiB */
                        if (chip->chipsize > (128 << 20))
                                chip->cmd_ctrl(mtd, page_addr >> 16,
                                               NAND_NCE | NAND_ALE);
                }
        }
        chip->cmd_ctrl(mtd, NAND_CMD_NONE, NAND_NCE | NAND_CTRL_CHANGE);

        /*
         * Program and erase have their own busy handlers status, sequential
         * in and status need no delay.
         */
        switch (command) {

        case NAND_CMD_CACHEDPROG:
        case NAND_CMD_PAGEPROG:
        case NAND_CMD_ERASE1:
        case NAND_CMD_ERASE2:
        case NAND_CMD_SEQIN:
        case NAND_CMD_RNDIN:
        case NAND_CMD_STATUS:
                return;

        case NAND_CMD_RESET:
                if (chip->dev_ready)
                        break;
                udelay(chip->chip_delay);
                chip->cmd_ctrl(mtd, NAND_CMD_STATUS,
                               NAND_NCE | NAND_CLE | NAND_CTRL_CHANGE);
                chip->cmd_ctrl(mtd, NAND_CMD_NONE,
                               NAND_NCE | NAND_CTRL_CHANGE);
                /* EZ-NAND can take upto 250ms as per ONFi v4.0 */
                nand_wait_status_ready(mtd, 250);
                return;

        case NAND_CMD_RNDOUT:
                /* No ready / busy check necessary */
                chip->cmd_ctrl(mtd, NAND_CMD_RNDOUTSTART,
                               NAND_NCE | NAND_CLE | NAND_CTRL_CHANGE);
                chip->cmd_ctrl(mtd, NAND_CMD_NONE,
                               NAND_NCE | NAND_CTRL_CHANGE);
                return;

        case NAND_CMD_READ0:
                chip->cmd_ctrl(mtd, NAND_CMD_READSTART,
                               NAND_NCE | NAND_CLE | NAND_CTRL_CHANGE);
                chip->cmd_ctrl(mtd, NAND_CMD_NONE,
                               NAND_NCE | NAND_CTRL_CHANGE);

                /* This applies to read commands */
        default:
                /*
                 * If we don't have access to the busy pin, we apply the given
                 * command delay.
                 */
                if (!chip->dev_ready) {
                        udelay(chip->chip_delay);
                        return;
                }
        }

        /*
         * Apply this short delay always to ensure that we do wait tWB in
         * any case on any machine.
         */
        ndelay(100);

        nand_wait_ready(mtd);
}

/**
 * panic_nand_get_device - [GENERIC] Get chip for selected access
 * @chip: the nand chip descriptor
 * @mtd: MTD device structure
 * @new_state: the state which is requested
 *
 * Used when in panic, no locks are taken.
 */
static void panic_nand_get_device(struct nand_chip *chip,
                      struct mtd_info *mtd, int new_state)
{
        /* Hardware controller shared among independent devices */
        chip->controller->active = chip;
        chip->state = new_state;
}

/**
 * nand_get_device - [GENERIC] Get chip for selected access
 * @mtd: MTD device structure
 * @new_state: the state which is requested
 *
 * Get the device and lock it for exclusive access
 */
static int
nand_get_device(struct mtd_info *mtd, int new_state)
{
        struct nand_chip *chip = mtd_to_nand(mtd);
        chip->state = new_state;
        return 0;
}

/**
 * panic_nand_wait - [GENERIC] wait until the command is done
 * @mtd: MTD device structure
 * @chip: NAND chip structure
 * @timeo: timeout
 *
 * Wait for command done. This is a helper function for nand_wait used when
 * we are in interrupt context. May happen when in panic and trying to write
 * an oops through mtdoops.
 */
static void panic_nand_wait(struct mtd_info *mtd, struct nand_chip *chip,
                            unsigned long timeo)
{
        int i;
        for (i = 0; i < timeo; i++) {
                if (chip->dev_ready) {
                        if (chip->dev_ready(mtd))
                                break;
                } else {
                        if (chip->read_byte(mtd) & NAND_STATUS_READY)
                                break;
                }
                mdelay(1);
        }
}

/**
 * nand_wait - [DEFAULT] wait until the command is done
 * @mtd: MTD device structure
 * @chip: NAND chip structure
 *
 * Wait for command done. This applies to erase and program only. Erase can
 * take up to 400ms and program up to 20ms according to general NAND and
 * SmartMedia specs.
 */
static int nand_wait(struct mtd_info *mtd, struct nand_chip *chip)
{

        int status, state = chip->state;
        unsigned long timeo = (state == FL_ERASING ? 400 : 20);

        led_trigger_event(nand_led_trigger, LED_FULL);

        /*
         * Apply this short delay always to ensure that we do wait tWB in any
         * case on any machine.
         */
        ndelay(100);

        chip->cmdfunc(mtd, NAND_CMD_STATUS, -1, -1);

        u32 timer = (CONFIG_SYS_HZ * timeo) / 1000;
        u32 time_start;
 
        time_start = get_timer(0);
        while (get_timer(time_start) < timer) {
                if (chip->dev_ready) {
                        if (chip->dev_ready(mtd))
                                break;
                } else {
                        if (chip->read_byte(mtd) & NAND_STATUS_READY)
                                break;
                }
        }
        led_trigger_event(nand_led_trigger, LED_OFF);

        status = (int)chip->read_byte(mtd);
        /* This can happen if in case of timeout or buggy dev_ready */
        WARN_ON(!(status & NAND_STATUS_READY));
        return status;
}

/**
 * nand_read_page_raw - [INTERN] read raw page data without ecc
 * @mtd: mtd info structure
 * @chip: nand chip info structure
 * @buf: buffer to store read data
 * @oob_required: caller requires OOB data read to chip->oob_poi
 * @page: page number to read
 *
 * Not for syndrome calculating ECC controllers, which use a special oob layout.
 */
static int nand_read_page_raw(struct mtd_info *mtd, struct nand_chip *chip,
                              uint8_t *buf, int oob_required, int page)
{
        chip->read_buf(mtd, buf, mtd->writesize);
        if (oob_required)
                chip->read_buf(mtd, chip->oob_poi, mtd->oobsize);
        return 0;
}

/**
 * nand_read_page_raw_syndrome - [INTERN] read raw page data without ecc
 * @mtd: mtd info structure
 * @chip: nand chip info structure
 * @buf: buffer to store read data
 * @oob_required: caller requires OOB data read to chip->oob_poi
 * @page: page number to read
 *
 * We need a special oob layout and handling even when OOB isn't used.
 */
static int nand_read_page_raw_syndrome(struct mtd_info *mtd,
                                       struct nand_chip *chip, uint8_t *buf,
                                       int oob_required, int page)
{
        int eccsize = chip->ecc.size;
        int eccbytes = chip->ecc.bytes;
        uint8_t *oob = chip->oob_poi;
        int steps, size;

        for (steps = chip->ecc.steps; steps > 0; steps--) {
                chip->read_buf(mtd, buf, eccsize);
                buf += eccsize;

                if (chip->ecc.prepad) {
                        chip->read_buf(mtd, oob, chip->ecc.prepad);
                        oob += chip->ecc.prepad;
                }

                chip->read_buf(mtd, oob, eccbytes);
                oob += eccbytes;

                if (chip->ecc.postpad) {
                        chip->read_buf(mtd, oob, chip->ecc.postpad);
                        oob += chip->ecc.postpad;
                }
        }

        size = mtd->oobsize - (oob - chip->oob_poi);
        if (size)
                chip->read_buf(mtd, oob, size);

        return 0;
}

/**
 * nand_read_page_swecc - [REPLACEABLE] software ECC based page read function
 * @mtd: mtd info structure
 * @chip: nand chip info structure
 * @buf: buffer to store read data
 * @oob_required: caller requires OOB data read to chip->oob_poi
 * @page: page number to read
 */
static int nand_read_page_swecc(struct mtd_info *mtd, struct nand_chip *chip,
                                uint8_t *buf, int oob_required, int page)
{
        int i, eccsize = chip->ecc.size;
        int eccbytes = chip->ecc.bytes;
        int eccsteps = chip->ecc.steps;
        uint8_t *p = buf;
        uint8_t *ecc_calc = chip->buffers->ecccalc;
        uint8_t *ecc_code = chip->buffers->ecccode;
        uint32_t *eccpos = chip->ecc.layout->eccpos;
        unsigned int max_bitflips = 0;

        chip->ecc.read_page_raw(mtd, chip, buf, 1, page);

        for (i = 0; eccsteps; eccsteps--, i += eccbytes, p += eccsize)
                chip->ecc.calculate(mtd, p, &ecc_calc[i]);

        for (i = 0; i < chip->ecc.total; i++)
                ecc_code[i] = chip->oob_poi[eccpos[i]];

        eccsteps = chip->ecc.steps;
        p = buf;

        for (i = 0 ; eccsteps; eccsteps--, i += eccbytes, p += eccsize) {
                int stat;

                stat = chip->ecc.correct(mtd, p, &ecc_code[i], &ecc_calc[i]);
                if (stat < 0) {
                        mtd->ecc_stats.failed++;
                } else {
                        mtd->ecc_stats.corrected += stat;
                        max_bitflips = max_t(unsigned int, max_bitflips, stat);
                }
        }
        return max_bitflips;
}

/**
 * nand_read_subpage - [REPLACEABLE] ECC based sub-page read function
 * @mtd: mtd info structure
 * @chip: nand chip info structure
 * @data_offs: offset of requested data within the page
 * @readlen: data length
 * @bufpoi: buffer to store read data
 * @page: page number to read
 */
static int nand_read_subpage(struct mtd_info *mtd, struct nand_chip *chip,
                        uint32_t data_offs, uint32_t readlen, uint8_t *bufpoi,
                        int page)
{
        int start_step, end_step, num_steps;
        uint32_t *eccpos = chip->ecc.layout->eccpos;
        uint8_t *p;
        int data_col_addr, i, gaps = 0;
        int datafrag_len, eccfrag_len, aligned_len, aligned_pos;
        int busw = (chip->options & NAND_BUSWIDTH_16) ? 2 : 1;
        int index;
        unsigned int max_bitflips = 0;

        /* Column address within the page aligned to ECC size (256bytes) */
        start_step = data_offs / chip->ecc.size;
        end_step = (data_offs + readlen - 1) / chip->ecc.size;
        num_steps = end_step - start_step + 1;
        index = start_step * chip->ecc.bytes;

        /* Data size aligned to ECC ecc.size */
        datafrag_len = num_steps * chip->ecc.size;
        eccfrag_len = num_steps * chip->ecc.bytes;

        data_col_addr = start_step * chip->ecc.size;
        /* If we read not a page aligned data */
        if (data_col_addr != 0)
                chip->cmdfunc(mtd, NAND_CMD_RNDOUT, data_col_addr, -1);

        p = bufpoi + data_col_addr;
        chip->read_buf(mtd, p, datafrag_len);

        /* Calculate ECC */
        for (i = 0; i < eccfrag_len ; i += chip->ecc.bytes, p += chip->ecc.size)
                chip->ecc.calculate(mtd, p, &chip->buffers->ecccalc[i]);

        /*
         * The performance is faster if we position offsets according to
         * ecc.pos. Let's make sure that there are no gaps in ECC positions.
         */
        for (i = 0; i < eccfrag_len - 1; i++) {
                if (eccpos[i + index] + 1 != eccpos[i + index + 1]) {
                        gaps = 1;
                        break;
                }
        }
        if (gaps) {
                chip->cmdfunc(mtd, NAND_CMD_RNDOUT, mtd->writesize, -1);
                chip->read_buf(mtd, chip->oob_poi, mtd->oobsize);
        } else {
                /*
                 * Send the command to read the particular ECC bytes take care
                 * about buswidth alignment in read_buf.
                 */
                aligned_pos = eccpos[index] & ~(busw - 1);
                aligned_len = eccfrag_len;
                if (eccpos[index] & (busw - 1))
                        aligned_len++;
                if (eccpos[index + (num_steps * chip->ecc.bytes)] & (busw - 1))
                        aligned_len++;

                chip->cmdfunc(mtd, NAND_CMD_RNDOUT,
                                        mtd->writesize + aligned_pos, -1);
                chip->read_buf(mtd, &chip->oob_poi[aligned_pos], aligned_len);
        }

        for (i = 0; i < eccfrag_len; i++)
                chip->buffers->ecccode[i] = chip->oob_poi[eccpos[i + index]];

        p = bufpoi + data_col_addr;
        for (i = 0; i < eccfrag_len ; i += chip->ecc.bytes, p += chip->ecc.size) {
                int stat;

                stat = chip->ecc.correct(mtd, p,
                        &chip->buffers->ecccode[i], &chip->buffers->ecccalc[i]);
                if (stat < 0) {
                        mtd->ecc_stats.failed++;
                } else {
                        mtd->ecc_stats.corrected += stat;
                        max_bitflips = max_t(unsigned int, max_bitflips, stat);
                }
        }
        return max_bitflips;
}

/**
 * nand_read_page_hwecc - [REPLACEABLE] hardware ECC based page read function
 * @mtd: mtd info structure
 * @chip: nand chip info structure
 * @buf: buffer to store read data
 * @oob_required: caller requires OOB data read to chip->oob_poi
 * @page: page number to read
 *
 * Not for syndrome calculating ECC controllers which need a special oob layout.
 */
static int nand_read_page_hwecc(struct mtd_info *mtd, struct nand_chip *chip,
                                uint8_t *buf, int oob_required, int page)
{
        int i, eccsize = chip->ecc.size;
        int eccbytes = chip->ecc.bytes;
        int eccsteps = chip->ecc.steps;
        uint8_t *p = buf;
        uint8_t *ecc_calc = chip->buffers->ecccalc;
        uint8_t *ecc_code = chip->buffers->ecccode;
        uint32_t *eccpos = chip->ecc.layout->eccpos;
        unsigned int max_bitflips = 0;

        for (i = 0; eccsteps; eccsteps--, i += eccbytes, p += eccsize) {
                chip->ecc.hwctl(mtd, NAND_ECC_READ);
                chip->read_buf(mtd, p, eccsize);
                chip->ecc.calculate(mtd, p, &ecc_calc[i]);
        }
        chip->read_buf(mtd, chip->oob_poi, mtd->oobsize);

        for (i = 0; i < chip->ecc.total; i++)
                ecc_code[i] = chip->oob_poi[eccpos[i]];

        eccsteps = chip->ecc.steps;
        p = buf;

        for (i = 0 ; eccsteps; eccsteps--, i += eccbytes, p += eccsize) {
                int stat;

                stat = chip->ecc.correct(mtd, p, &ecc_code[i], &ecc_calc[i]);
                if (stat < 0) {
                        mtd->ecc_stats.failed++;
                } else {
                        mtd->ecc_stats.corrected += stat;
                        max_bitflips = max_t(unsigned int, max_bitflips, stat);
                }
        }
        return max_bitflips;
}

/**
 * nand_read_page_hwecc_oob_first - [REPLACEABLE] hw ecc, read oob first
 * @mtd: mtd info structure
 * @chip: nand chip info structure
 * @buf: buffer to store read data
 * @oob_required: caller requires OOB data read to chip->oob_poi
 * @page: page number to read
 *
 * Hardware ECC for large page chips, require OOB to be read first. For this
 * ECC mode, the write_page method is re-used from ECC_HW. These methods
 * read/write ECC from the OOB area, unlike the ECC_HW_SYNDROME support with
 * multiple ECC steps, follows the "infix ECC" scheme and reads/writes ECC from
 * the data area, by overwriting the NAND manufacturer bad block markings.
 */
static int nand_read_page_hwecc_oob_first(struct mtd_info *mtd,
        struct nand_chip *chip, uint8_t *buf, int oob_required, int page)
{
        int i, eccsize = chip->ecc.size;
        int eccbytes = chip->ecc.bytes;
        int eccsteps = chip->ecc.steps;
        uint8_t *p = buf;
        uint8_t *ecc_code = chip->buffers->ecccode;
        uint32_t *eccpos = chip->ecc.layout->eccpos;
        uint8_t *ecc_calc = chip->buffers->ecccalc;
        unsigned int max_bitflips = 0;

        /* Read the OOB area first */
        chip->cmdfunc(mtd, NAND_CMD_READOOB, 0, page);
        chip->read_buf(mtd, chip->oob_poi, mtd->oobsize);
        chip->cmdfunc(mtd, NAND_CMD_READ0, 0, page);

        for (i = 0; i < chip->ecc.total; i++)
                ecc_code[i] = chip->oob_poi[eccpos[i]];

        for (i = 0; eccsteps; eccsteps--, i += eccbytes, p += eccsize) {
                int stat;

                chip->ecc.hwctl(mtd, NAND_ECC_READ);
                chip->read_buf(mtd, p, eccsize);
                chip->ecc.calculate(mtd, p, &ecc_calc[i]);

                stat = chip->ecc.correct(mtd, p, &ecc_code[i], NULL);
                if (stat < 0) {
                        mtd->ecc_stats.failed++;
                } else {
                        mtd->ecc_stats.corrected += stat;
                        max_bitflips = max_t(unsigned int, max_bitflips, stat);
                }
        }
        return max_bitflips;
}

/**
 * nand_read_page_syndrome - [REPLACEABLE] hardware ECC syndrome based page read
 * @mtd: mtd info structure
 * @chip: nand chip info structure
 * @buf: buffer to store read data
 * @oob_required: caller requires OOB data read to chip->oob_poi
 * @page: page number to read
 *
 * The hw generator calculates the error syndrome automatically. Therefore we
 * need a special oob layout and handling.
 */
static int nand_read_page_syndrome(struct mtd_info *mtd, struct nand_chip *chip,
                                   uint8_t *buf, int oob_required, int page)
{
        int i, eccsize = chip->ecc.size;
        int eccbytes = chip->ecc.bytes;
        int eccsteps = chip->ecc.steps;
        uint8_t *p = buf;
        uint8_t *oob = chip->oob_poi;
        unsigned int max_bitflips = 0;

        for (i = 0; eccsteps; eccsteps--, i += eccbytes, p += eccsize) {
                int stat;

                chip->ecc.hwctl(mtd, NAND_ECC_READ);
                chip->read_buf(mtd, p, eccsize);

                if (chip->ecc.prepad) {
                        chip->read_buf(mtd, oob, chip->ecc.prepad);
                        oob += chip->ecc.prepad;
                }

                chip->ecc.hwctl(mtd, NAND_ECC_READSYN);
                chip->read_buf(mtd, oob, eccbytes);
                stat = chip->ecc.correct(mtd, p, oob, NULL);

                if (stat < 0) {
                        mtd->ecc_stats.failed++;
                } else {
                        mtd->ecc_stats.corrected += stat;
                        max_bitflips = max_t(unsigned int, max_bitflips, stat);
                }

                oob += eccbytes;

                if (chip->ecc.postpad) {
                        chip->read_buf(mtd, oob, chip->ecc.postpad);
                        oob += chip->ecc.postpad;
                }
        }

        /* Calculate remaining oob bytes */
        i = mtd->oobsize - (oob - chip->oob_poi);
        if (i)
                chip->read_buf(mtd, oob, i);

        return max_bitflips;
}

/**
 * nand_transfer_oob - [INTERN] Transfer oob to client buffer
 * @chip: nand chip structure
 * @oob: oob destination address
 * @ops: oob ops structure
 * @len: size of oob to transfer
 */
static uint8_t *nand_transfer_oob(struct nand_chip *chip, uint8_t *oob,
                                  struct mtd_oob_ops *ops, size_t len)
{
        switch (ops->mode) {

        case MTD_OPS_PLACE_OOB:
        case MTD_OPS_RAW:
                memcpy(oob, chip->oob_poi + ops->ooboffs, len);
                return oob + len;

        case MTD_OPS_AUTO_OOB: {
                struct nand_oobfree *free = chip->ecc.layout->oobfree;
                uint32_t boffs = 0, roffs = ops->ooboffs;
                size_t bytes = 0;

                for (; free->length && len; free++, len -= bytes) {
                        /* Read request not from offset 0? */
                        if (unlikely(roffs)) {
                                if (roffs >= free->length) {
                                        roffs -= free->length;
                                        continue;
                                }
                                boffs = free->offset + roffs;
                                bytes = min_t(size_t, len,
                                              (free->length - roffs));
                                roffs = 0;
                        } else {
                                bytes = min_t(size_t, len, free->length);
                                boffs = free->offset;
                        }
                        memcpy(oob, chip->oob_poi + boffs, bytes);
                        oob += bytes;
                }
                return oob;
        }
        default:
                BUG();
        }
        return NULL;
}

/**
 * nand_setup_read_retry - [INTERN] Set the READ RETRY mode
 * @mtd: MTD device structure
 * @retry_mode: the retry mode to use
 *
 * Some vendors supply a special command to shift the Vt threshold, to be used
 * when there are too many bitflips in a page (i.e., ECC error). After setting
 * a new threshold, the host should retry reading the page.
 */
static int nand_setup_read_retry(struct mtd_info *mtd, int retry_mode)
{
        struct nand_chip *chip = mtd_to_nand(mtd);

        pr_debug("setting READ RETRY mode %d\n", retry_mode);

        if (retry_mode >= chip->read_retries)
                return -EINVAL;

        if (!chip->setup_read_retry)
                return -EOPNOTSUPP;

        return chip->setup_read_retry(mtd, retry_mode);
}

/**
 * nand_do_read_ops - [INTERN] Read data with ECC
 * @mtd: MTD device structure
 * @from: offset to read from
 * @ops: oob ops structure
 *
 * Internal function. Called with chip held.
 */
static int nand_do_read_ops(struct mtd_info *mtd, loff_t from,
                            struct mtd_oob_ops *ops)
{
        int chipnr, page, realpage, col, bytes, aligned, oob_required;
        struct nand_chip *chip = mtd_to_nand(mtd);
        int ret = 0;
        uint32_t readlen = ops->len;
        uint32_t oobreadlen = ops->ooblen;
        uint32_t max_oobsize = ops->mode == MTD_OPS_AUTO_OOB ?
                mtd->oobavail : mtd->oobsize;

        uint8_t *bufpoi, *oob, *buf;
        int use_bufpoi;
        unsigned int max_bitflips = 0;
        int retry_mode = 0;
        bool ecc_fail = false;

        chipnr = (int)(from >> chip->chip_shift);
        chip->select_chip(mtd, chipnr);

        realpage = (int)(from >> chip->page_shift);
        page = realpage & chip->pagemask;

        col = (int)(from & (mtd->writesize - 1));

        buf = ops->datbuf;
        oob = ops->oobbuf;
        oob_required = oob ? 1 : 0;

        while (1) {
                unsigned int ecc_failures = mtd->ecc_stats.failed;

                WATCHDOG_RESET();
                bytes = min(mtd->writesize - col, readlen);
                aligned = (bytes == mtd->writesize);

                if (!aligned)
                        use_bufpoi = 1;
                else
                        use_bufpoi = 0;

                /* Is the current page in the buffer? */
                if (realpage != chip->pagebuf || oob) {
                        bufpoi = use_bufpoi ? chip->buffers->databuf : buf;

                        if (use_bufpoi && aligned)
                                pr_debug("%s: using read bounce buffer for buf@%p\n",
                                                 __func__, buf);

read_retry:
                        chip->cmdfunc(mtd, NAND_CMD_READ0, 0x00, page);

                        /*
                         * Now read the page into the buffer.  Absent an error,
                         * the read methods return max bitflips per ecc step.
                         */
                        if (unlikely(ops->mode == MTD_OPS_RAW))
                                ret = chip->ecc.read_page_raw(mtd, chip, bufpoi,
                                                              oob_required,
                                                              page);
                        else if (!aligned && NAND_HAS_SUBPAGE_READ(chip) &&
                                 !oob)
                                ret = chip->ecc.read_subpage(mtd, chip,
                                                        col, bytes, bufpoi,
                                                        page);
                        else
                                ret = chip->ecc.read_page(mtd, chip, bufpoi,
                                                          oob_required, page);
                        if (ret < 0) {
                                if (use_bufpoi)
                                        /* Invalidate page cache */
                                        chip->pagebuf = -1;
                                break;
                        }

                        max_bitflips = max_t(unsigned int, max_bitflips, ret);

                        /* Transfer not aligned data */
                        if (use_bufpoi) {
                                if (!NAND_HAS_SUBPAGE_READ(chip) && !oob &&
                                    !(mtd->ecc_stats.failed - ecc_failures) &&
                                    (ops->mode != MTD_OPS_RAW)) {
                                        chip->pagebuf = realpage;
                                        chip->pagebuf_bitflips = ret;
                                } else {
                                        /* Invalidate page cache */
                                        chip->pagebuf = -1;
                                }
                                memcpy(buf, chip->buffers->databuf + col, bytes);
                        }

                        if (unlikely(oob)) {
                                int toread = min(oobreadlen, max_oobsize);

                                if (toread) {
                                        oob = nand_transfer_oob(chip,
                                                oob, ops, toread);
                                        oobreadlen -= toread;
                                }
                        }

                        if (chip->options & NAND_NEED_READRDY) {
                                /* Apply delay or wait for ready/busy pin */
                                if (!chip->dev_ready)
                                        udelay(chip->chip_delay);
                                else
                                        nand_wait_ready(mtd);
                        }

                        if (mtd->ecc_stats.failed - ecc_failures) {
                                if (retry_mode + 1 < chip->read_retries) {
                                        retry_mode++;
                                        ret = nand_setup_read_retry(mtd,
                                                        retry_mode);
                                        if (ret < 0)
                                                break;

                                        /* Reset failures; retry */
                                        mtd->ecc_stats.failed = ecc_failures;
                                        goto read_retry;
                                } else {
                                        /* No more retry modes; real failure */
                                        ecc_fail = true;
                                }
                        }

                        buf += bytes;
                } else {
                        memcpy(buf, chip->buffers->databuf + col, bytes);
                        buf += bytes;
                        max_bitflips = max_t(unsigned int, max_bitflips,
                                             chip->pagebuf_bitflips);
                }

                readlen -= bytes;

                /* Reset to retry mode 0 */
                if (retry_mode) {
                        ret = nand_setup_read_retry(mtd, 0);
                        if (ret < 0)
                                break;
                        retry_mode = 0;
                }

                if (!readlen)
                        break;

                /* For subsequent reads align to page boundary */
                col = 0;
                /* Increment page address */
                realpage++;

                page = realpage & chip->pagemask;
                /* Check, if we cross a chip boundary */
                if (!page) {
                        chipnr++;
                        chip->select_chip(mtd, -1);
                        chip->select_chip(mtd, chipnr);
                }
        }
        chip->select_chip(mtd, -1);

        ops->retlen = ops->len - (size_t) readlen;
        if (oob)
                ops->oobretlen = ops->ooblen - oobreadlen;

        if (ret < 0)
                return ret;

        if (ecc_fail)
                return -EBADMSG;

        return max_bitflips;
}

/**
 * nand_read - [MTD Interface] MTD compatibility function for nand_do_read_ecc
 * @mtd: MTD device structure
 * @from: offset to read from
 * @len: number of bytes to read
 * @retlen: pointer to variable to store the number of read bytes
 * @buf: the databuffer to put data
 *
 * Get hold of the chip and call nand_do_read.
 */
static int nand_read(struct mtd_info *mtd, loff_t from, size_t len,
                     size_t *retlen, uint8_t *buf)
{
        struct mtd_oob_ops ops;
        int ret;

        nand_get_device(mtd, FL_READING);
        memset(&ops, 0, sizeof(ops));
        ops.len = len;
        ops.datbuf = buf;
        ops.mode = MTD_OPS_PLACE_OOB;
        ret = nand_do_read_ops(mtd, from, &ops);
        *retlen = ops.retlen;
        nand_release_device(mtd);
        return ret;
}

/**
 * nand_read_oob_std - [REPLACEABLE] the most common OOB data read function
 * @mtd: mtd info structure
 * @chip: nand chip info structure
 * @page: page number to read
 */
static int nand_read_oob_std(struct mtd_info *mtd, struct nand_chip *chip,
                             int page)
{
        chip->cmdfunc(mtd, NAND_CMD_READOOB, 0, page);
        chip->read_buf(mtd, chip->oob_poi, mtd->oobsize);
        return 0;
}

/**
 * nand_read_oob_syndrome - [REPLACEABLE] OOB data read function for HW ECC
 *                          with syndromes
 * @mtd: mtd info structure
 * @chip: nand chip info structure
 * @page: page number to read
 */
static int nand_read_oob_syndrome(struct mtd_info *mtd, struct nand_chip *chip,
                                  int page)
{
        int length = mtd->oobsize;
        int chunk = chip->ecc.bytes + chip->ecc.prepad + chip->ecc.postpad;
        int eccsize = chip->ecc.size;
        uint8_t *bufpoi = chip->oob_poi;
        int i, toread, sndrnd = 0, pos;

        chip->cmdfunc(mtd, NAND_CMD_READ0, chip->ecc.size, page);
        for (i = 0; i < chip->ecc.steps; i++) {
                if (sndrnd) {
                        pos = eccsize + i * (eccsize + chunk);
                        if (mtd->writesize > 512)
                                chip->cmdfunc(mtd, NAND_CMD_RNDOUT, pos, -1);
                        else
                                chip->cmdfunc(mtd, NAND_CMD_READ0, pos, page);
                } else
                        sndrnd = 1;
                toread = min_t(int, length, chunk);
                chip->read_buf(mtd, bufpoi, toread);
                bufpoi += toread;
                length -= toread;
        }
        if (length > 0)
                chip->read_buf(mtd, bufpoi, length);

        return 0;
}

/**
 * nand_write_oob_std - [REPLACEABLE] the most common OOB data write function
 * @mtd: mtd info structure
 * @chip: nand chip info structure
 * @page: page number to write
 */
static int nand_write_oob_std(struct mtd_info *mtd, struct nand_chip *chip,
                              int page)
{
        int status = 0;
        const uint8_t *buf = chip->oob_poi;
        int length = mtd->oobsize;

        chip->cmdfunc(mtd, NAND_CMD_SEQIN, mtd->writesize, page);
        chip->write_buf(mtd, buf, length);
        /* Send command to program the OOB data */
        chip->cmdfunc(mtd, NAND_CMD_PAGEPROG, -1, -1);

        status = chip->waitfunc(mtd, chip);

        return status & NAND_STATUS_FAIL ? -EIO : 0;
}

/**
 * nand_write_oob_syndrome - [REPLACEABLE] OOB data write function for HW ECC
 *                           with syndrome - only for large page flash
 * @mtd: mtd info structure
 * @chip: nand chip info structure
 * @page: page number to write
 */
static int nand_write_oob_syndrome(struct mtd_info *mtd,
                                   struct nand_chip *chip, int page)
{
        int chunk = chip->ecc.bytes + chip->ecc.prepad + chip->ecc.postpad;
        int eccsize = chip->ecc.size, length = mtd->oobsize;
        int i, len, pos, status = 0, sndcmd = 0, steps = chip->ecc.steps;
        const uint8_t *bufpoi = chip->oob_poi;

        /*
         * data-ecc-data-ecc ... ecc-oob
         * or
         * data-pad-ecc-pad-data-pad .... ecc-pad-oob
         */
        if (!chip->ecc.prepad && !chip->ecc.postpad) {
                pos = steps * (eccsize + chunk);
                steps = 0;
        } else
                pos = eccsize;

        chip->cmdfunc(mtd, NAND_CMD_SEQIN, pos, page);
        for (i = 0; i < steps; i++) {
                if (sndcmd) {
                        if (mtd->writesize <= 512) {
                                uint32_t fill = 0xFFFFFFFF;

                                len = eccsize;
                                while (len > 0) {
                                        int num = min_t(int, len, 4);
                                        chip->write_buf(mtd, (uint8_t *)&fill,
                                                        num);
                                        len -= num;
                                }
                        } else {
                                pos = eccsize + i * (eccsize + chunk);
                                chip->cmdfunc(mtd, NAND_CMD_RNDIN, pos, -1);
                        }
                } else
                        sndcmd = 1;
                len = min_t(int, length, chunk);
                chip->write_buf(mtd, bufpoi, len);
                bufpoi += len;
                length -= len;
        }
        if (length > 0)
                chip->write_buf(mtd, bufpoi, length);

        chip->cmdfunc(mtd, NAND_CMD_PAGEPROG, -1, -1);
        status = chip->waitfunc(mtd, chip);

        return status & NAND_STATUS_FAIL ? -EIO : 0;
}

/**
 * nand_do_read_oob - [INTERN] NAND read out-of-band
 * @mtd: MTD device structure
 * @from: offset to read from
 * @ops: oob operations description structure
 *
 * NAND read out-of-band data from the spare area.
 */
static int nand_do_read_oob(struct mtd_info *mtd, loff_t from,
                            struct mtd_oob_ops *ops)
{
        int page, realpage, chipnr;
        struct nand_chip *chip = mtd_to_nand(mtd);
        struct mtd_ecc_stats stats;
        int readlen = ops->ooblen;
        int len;
        uint8_t *buf = ops->oobbuf;
        int ret = 0;

        pr_debug("%s: from = 0x%08Lx, len = %i\n",
                        __func__, (unsigned long long)from, readlen);

        stats = mtd->ecc_stats;

        if (ops->mode == MTD_OPS_AUTO_OOB)
                len = chip->ecc.layout->oobavail;
        else
                len = mtd->oobsize;

        if (unlikely(ops->ooboffs >= len)) {
                pr_debug("%s: attempt to start read outside oob\n",
                                __func__);
                return -EINVAL;
        }

        /* Do not allow reads past end of device */
        if (unlikely(from >= mtd->size ||
                     ops->ooboffs + readlen > ((mtd->size >> chip->page_shift) -
                                        (from >> chip->page_shift)) * len)) {
                pr_debug("%s: attempt to read beyond end of device\n",
                                __func__);
                return -EINVAL;
        }

        chipnr = (int)(from >> chip->chip_shift);
        chip->select_chip(mtd, chipnr);

        /* Shift to get page */
        realpage = (int)(from >> chip->page_shift);
        page = realpage & chip->pagemask;

        while (1) {
                WATCHDOG_RESET();

                if (ops->mode == MTD_OPS_RAW)
                        ret = chip->ecc.read_oob_raw(mtd, chip, page);
                else
                        ret = chip->ecc.read_oob(mtd, chip, page);

                if (ret < 0)
                        break;

                len = min(len, readlen);
                buf = nand_transfer_oob(chip, buf, ops, len);

                if (chip->options & NAND_NEED_READRDY) {
                        /* Apply delay or wait for ready/busy pin */
                        if (!chip->dev_ready)
                                udelay(chip->chip_delay);
                        else
                                nand_wait_ready(mtd);
                }

                readlen -= len;
                if (!readlen)
                        break;

                /* Increment page address */
                realpage++;

                page = realpage & chip->pagemask;
                /* Check, if we cross a chip boundary */
                if (!page) {
                        chipnr++;
                        chip->select_chip(mtd, -1);
                        chip->select_chip(mtd, chipnr);
                }
        }
        chip->select_chip(mtd, -1);

        ops->oobretlen = ops->ooblen - readlen;

        if (ret < 0)
                return ret;

        if (mtd->ecc_stats.failed - stats.failed)
                return -EBADMSG;

        return  mtd->ecc_stats.corrected - stats.corrected ? -EUCLEAN : 0;
}

/**
 * nand_read_oob - [MTD Interface] NAND read data and/or out-of-band
 * @mtd: MTD device structure
 * @from: offset to read from
 * @ops: oob operation description structure
 *
 * NAND read data and/or out-of-band data.
 */
static int nand_read_oob(struct mtd_info *mtd, loff_t from,
                         struct mtd_oob_ops *ops)
{
        int ret = -ENOTSUPP;

        ops->retlen = 0;

        /* Do not allow reads past end of device */
        if (ops->datbuf && (from + ops->len) > mtd->size) {
                pr_debug("%s: attempt to read beyond end of device\n",
                                __func__);
                return -EINVAL;
        }

        nand_get_device(mtd, FL_READING);

        switch (ops->mode) {
        case MTD_OPS_PLACE_OOB:
        case MTD_OPS_AUTO_OOB:
        case MTD_OPS_RAW:
                break;

        default:
                goto out;
        }

        if (!ops->datbuf)
                ret = nand_do_read_oob(mtd, from, ops);
        else
                ret = nand_do_read_ops(mtd, from, ops);

out:
        nand_release_device(mtd);
        return ret;
}


/**
 * nand_write_page_raw - [INTERN] raw page write function
 * @mtd: mtd info structure
 * @chip: nand chip info structure
 * @buf: data buffer
 * @oob_required: must write chip->oob_poi to OOB
 * @page: page number to write
 *
 * Not for syndrome calculating ECC controllers, which use a special oob layout.
 */
static int nand_write_page_raw(struct mtd_info *mtd, struct nand_chip *chip,
                                const uint8_t *buf, int oob_required,
                                int page)
{
        chip->write_buf(mtd, buf, mtd->writesize);
        if (oob_required)
                chip->write_buf(mtd, chip->oob_poi, mtd->oobsize);

        return 0;
}

/**
 * nand_write_page_raw_syndrome - [INTERN] raw page write function
 * @mtd: mtd info structure
 * @chip: nand chip info structure
 * @buf: data buffer
 * @oob_required: must write chip->oob_poi to OOB
 *
 * We need a special oob layout and handling even when ECC isn't checked.
 */
static int nand_write_page_raw_syndrome(struct mtd_info *mtd,
                                        struct nand_chip *chip,
                                        const uint8_t *buf, int oob_required,
                                        int page)
{
        int eccsize = chip->ecc.size;
        int eccbytes = chip->ecc.bytes;
        uint8_t *oob = chip->oob_poi;
        int steps, size;

        for (steps = chip->ecc.steps; steps > 0; steps--) {
                chip->write_buf(mtd, buf, eccsize);
                buf += eccsize;

                if (chip->ecc.prepad) {
                        chip->write_buf(mtd, oob, chip->ecc.prepad);
                        oob += chip->ecc.prepad;
                }

                chip->write_buf(mtd, oob, eccbytes);
                oob += eccbytes;

                if (chip->ecc.postpad) {
                        chip->write_buf(mtd, oob, chip->ecc.postpad);
                        oob += chip->ecc.postpad;
                }
        }

        size = mtd->oobsize - (oob - chip->oob_poi);
        if (size)
                chip->write_buf(mtd, oob, size);

        return 0;
}
/**
 * nand_write_page_swecc - [REPLACEABLE] software ECC based page write function
 * @mtd: mtd info structure
 * @chip: nand chip info structure
 * @buf: data buffer
 * @oob_required: must write chip->oob_poi to OOB
 * @page: page number to write
 */
static int nand_write_page_swecc(struct mtd_info *mtd, struct nand_chip *chip,
                                  const uint8_t *buf, int oob_required,
                                  int page)
{
        int i, eccsize = chip->ecc.size;
        int eccbytes = chip->ecc.bytes;
        int eccsteps = chip->ecc.steps;
        uint8_t *ecc_calc = chip->buffers->ecccalc;
        const uint8_t *p = buf;
        uint32_t *eccpos = chip->ecc.layout->eccpos;

        /* Software ECC calculation */
        for (i = 0; eccsteps; eccsteps--, i += eccbytes, p += eccsize)
                chip->ecc.calculate(mtd, p, &ecc_calc[i]);

        for (i = 0; i < chip->ecc.total; i++)
                chip->oob_poi[eccpos[i]] = ecc_calc[i];

        return chip->ecc.write_page_raw(mtd, chip, buf, 1, page);
}

/**
 * nand_write_page_hwecc - [REPLACEABLE] hardware ECC based page write function
 * @mtd: mtd info structure
 * @chip: nand chip info structure
 * @buf: data buffer
 * @oob_required: must write chip->oob_poi to OOB
 * @page: page number to write
 */
static int nand_write_page_hwecc(struct mtd_info *mtd, struct nand_chip *chip,
                                  const uint8_t *buf, int oob_required,
                                  int page)
{
        int i, eccsize = chip->ecc.size;
        int eccbytes = chip->ecc.bytes;
        int eccsteps = chip->ecc.steps;
        uint8_t *ecc_calc = chip->buffers->ecccalc;
        const uint8_t *p = buf;
        uint32_t *eccpos = chip->ecc.layout->eccpos;

        for (i = 0; eccsteps; eccsteps--, i += eccbytes, p += eccsize) {
                chip->ecc.hwctl(mtd, NAND_ECC_WRITE);
                chip->write_buf(mtd, p, eccsize);
                chip->ecc.calculate(mtd, p, &ecc_calc[i]);
        }

        for (i = 0; i < chip->ecc.total; i++)
                chip->oob_poi[eccpos[i]] = ecc_calc[i];

        chip->write_buf(mtd, chip->oob_poi, mtd->oobsize);

        return 0;
}


/**
 * nand_write_subpage_hwecc - [REPLACEABLE] hardware ECC based subpage write
 * @mtd:        mtd info structure
 * @chip:       nand chip info structure
 * @offset:     column address of subpage within the page
 * @data_len:   data length
 * @buf:        data buffer
 * @oob_required: must write chip->oob_poi to OOB
 * @page: page number to write
 */
static int nand_write_subpage_hwecc(struct mtd_info *mtd,
                                struct nand_chip *chip, uint32_t offset,
                                uint32_t data_len, const uint8_t *buf,
                                int oob_required, int page)
{
        uint8_t *oob_buf  = chip->oob_poi;
        uint8_t *ecc_calc = chip->buffers->ecccalc;
        int ecc_size      = chip->ecc.size;
        int ecc_bytes     = chip->ecc.bytes;
        int ecc_steps     = chip->ecc.steps;
        uint32_t *eccpos  = chip->ecc.layout->eccpos;
        uint32_t start_step = offset / ecc_size;
        uint32_t end_step   = (offset + data_len - 1) / ecc_size;
        int oob_bytes       = mtd->oobsize / ecc_steps;
        int step, i;

        for (step = 0; step < ecc_steps; step++) {
                /* configure controller for WRITE access */
                chip->ecc.hwctl(mtd, NAND_ECC_WRITE);

                /* write data (untouched subpages already masked by 0xFF) */
                chip->write_buf(mtd, buf, ecc_size);

                /* mask ECC of un-touched subpages by padding 0xFF */
                if ((step < start_step) || (step > end_step))
                        memset(ecc_calc, 0xff, ecc_bytes);
                else
                        chip->ecc.calculate(mtd, buf, ecc_calc);

                /* mask OOB of un-touched subpages by padding 0xFF */
                /* if oob_required, preserve OOB metadata of written subpage */
                if (!oob_required || (step < start_step) || (step > end_step))
                        memset(oob_buf, 0xff, oob_bytes);

                buf += ecc_size;
                ecc_calc += ecc_bytes;
                oob_buf  += oob_bytes;
        }

        /* copy calculated ECC for whole page to chip->buffer->oob */
        /* this include masked-value(0xFF) for unwritten subpages */
        ecc_calc = chip->buffers->ecccalc;
        for (i = 0; i < chip->ecc.total; i++)
                chip->oob_poi[eccpos[i]] = ecc_calc[i];

        /* write OOB buffer to NAND device */
        chip->write_buf(mtd, chip->oob_poi, mtd->oobsize);

        return 0;
}


/**
 * nand_write_page_syndrome - [REPLACEABLE] hardware ECC syndrome based page write
 * @mtd: mtd info structure
 * @chip: nand chip info structure
 * @buf: data buffer
 * @oob_required: must write chip->oob_poi to OOB
 *
 * The hw generator calculates the error syndrome automatically. Therefore we
 * need a special oob layout and handling.
 */
static int nand_write_page_syndrome(struct mtd_info *mtd,
                                    struct nand_chip *chip,
                                    const uint8_t *buf, int oob_required,
                                    int page)
{
        int i, eccsize = chip->ecc.size;
        int eccbytes = chip->ecc.bytes;
        int eccsteps = chip->ecc.steps;
        const uint8_t *p = buf;
        uint8_t *oob = chip->oob_poi;

        for (i = 0; eccsteps; eccsteps--, i += eccbytes, p += eccsize) {

                chip->ecc.hwctl(mtd, NAND_ECC_WRITE);
                chip->write_buf(mtd, p, eccsize);

                if (chip->ecc.prepad) {
                        chip->write_buf(mtd, oob, chip->ecc.prepad);
                        oob += chip->ecc.prepad;
                }

                chip->ecc.calculate(mtd, p, oob);
                chip->write_buf(mtd, oob, eccbytes);
                oob += eccbytes;

                if (chip->ecc.postpad) {
                        chip->write_buf(mtd, oob, chip->ecc.postpad);
                        oob += chip->ecc.postpad;
                }
        }

        /* Calculate remaining oob bytes */
        i = mtd->oobsize - (oob - chip->oob_poi);
        if (i)
                chip->write_buf(mtd, oob, i);

        return 0;
}

/**
 * nand_write_page - [REPLACEABLE] write one page
 * @mtd: MTD device structure
 * @chip: NAND chip descriptor
 * @offset: address offset within the page
 * @data_len: length of actual data to be written
 * @buf: the data to write
 * @oob_required: must write chip->oob_poi to OOB
 * @page: page number to write
 * @cached: cached programming
 * @raw: use _raw version of write_page
 */
static int nand_write_page(struct mtd_info *mtd, struct nand_chip *chip,
                uint32_t offset, int data_len, const uint8_t *buf,
                int oob_required, int page, int cached, int raw)
{
        int status, subpage;

        if (!(chip->options & NAND_NO_SUBPAGE_WRITE) &&
                chip->ecc.write_subpage)
                subpage = offset || (data_len < mtd->writesize);
        else
                subpage = 0;

        chip->cmdfunc(mtd, NAND_CMD_SEQIN, 0x00, page);

        if (unlikely(raw))
                status = chip->ecc.write_page_raw(mtd, chip, buf,
                                                  oob_required, page);
        else if (subpage)
                status = chip->ecc.write_subpage(mtd, chip, offset, data_len,
                                                  buf, oob_required, page);
        else
                status = chip->ecc.write_page(mtd, chip, buf, oob_required,
                                              page);

        if (status < 0)
                return status;

        /*
         * Cached progamming disabled for now. Not sure if it's worth the
         * trouble. The speed gain is not very impressive. (2.3->2.6Mib/s).
         */
        cached = 0;

        if (!cached || !NAND_HAS_CACHEPROG(chip)) {

                chip->cmdfunc(mtd, NAND_CMD_PAGEPROG, -1, -1);
                status = chip->waitfunc(mtd, chip);
                /*
                 * See if operation failed and additional status checks are
                 * available.
                 */
                if ((status & NAND_STATUS_FAIL) && (chip->errstat))
                        status = chip->errstat(mtd, chip, FL_WRITING, status,
                                               page);

                if (status & NAND_STATUS_FAIL)
                        return -EIO;
        } else {
                chip->cmdfunc(mtd, NAND_CMD_CACHEDPROG, -1, -1);
                status = chip->waitfunc(mtd, chip);
        }

        return 0;
}

/**
 * nand_fill_oob - [INTERN] Transfer client buffer to oob
 * @mtd: MTD device structure
 * @oob: oob data buffer
 * @len: oob data write length
 * @ops: oob ops structure
 * @page: page number to write
 */
static uint8_t *nand_fill_oob(struct mtd_info *mtd, uint8_t *oob, size_t len,
                              struct mtd_oob_ops *ops)
{
        struct nand_chip *chip = mtd_to_nand(mtd);

        /*
         * Initialise to all 0xFF, to avoid the possibility of left over OOB
         * data from a previous OOB read.
         */
        memset(chip->oob_poi, 0xff, mtd->oobsize);

        switch (ops->mode) {

        case MTD_OPS_PLACE_OOB:
        case MTD_OPS_RAW:
                memcpy(chip->oob_poi + ops->ooboffs, oob, len);
                return oob + len;

        case MTD_OPS_AUTO_OOB: {
                struct nand_oobfree *free = chip->ecc.layout->oobfree;
                uint32_t boffs = 0, woffs = ops->ooboffs;
                size_t bytes = 0;

                for (; free->length && len; free++, len -= bytes) {
                        /* Write request not from offset 0? */
                        if (unlikely(woffs)) {
                                if (woffs >= free->length) {
                                        woffs -= free->length;
                                        continue;
                                }
                                boffs = free->offset + woffs;
                                bytes = min_t(size_t, len,
                                              (free->length - woffs));
                                woffs = 0;
                        } else {
                                bytes = min_t(size_t, len, free->length);
                                boffs = free->offset;
                        }
                        memcpy(chip->oob_poi + boffs, oob, bytes);
                        oob += bytes;
                }
                return oob;
        }
        default:
                BUG();
        }
        return NULL;
}

#define NOTALIGNED(x)   ((x & (chip->subpagesize - 1)) != 0)

/**
 * nand_do_write_ops - [INTERN] NAND write with ECC
 * @mtd: MTD device structure
 * @to: offset to write to
 * @ops: oob operations description structure
 *
 * NAND write with ECC.
 */
static int nand_do_write_ops(struct mtd_info *mtd, loff_t to,
                             struct mtd_oob_ops *ops)
{
        int chipnr, realpage, page, blockmask, column;
        struct nand_chip *chip = mtd_to_nand(mtd);
        uint32_t writelen = ops->len;

        uint32_t oobwritelen = ops->ooblen;
        uint32_t oobmaxlen = ops->mode == MTD_OPS_AUTO_OOB ?
                                mtd->oobavail : mtd->oobsize;

        uint8_t *oob = ops->oobbuf;
        uint8_t *buf = ops->datbuf;
        int ret;
        int oob_required = oob ? 1 : 0;

        ops->retlen = 0;
        if (!writelen)
                return 0;

        /* Reject writes, which are not page aligned */
        if (NOTALIGNED(to)) {
                pr_notice("%s: attempt to write non page aligned data\n",
                           __func__);
                return -EINVAL;
        }

        column = to & (mtd->writesize - 1);

        chipnr = (int)(to >> chip->chip_shift);
        chip->select_chip(mtd, chipnr);

        /* Check, if it is write protected */
        if (nand_check_wp(mtd)) {
                ret = -EIO;
                goto err_out;
        }

        realpage = (int)(to >> chip->page_shift);
        page = realpage & chip->pagemask;
        blockmask = (1 << (chip->phys_erase_shift - chip->page_shift)) - 1;

        /* Invalidate the page cache, when we write to the cached page */
        if (to <= ((loff_t)chip->pagebuf << chip->page_shift) &&
            ((loff_t)chip->pagebuf << chip->page_shift) < (to + ops->len))
                chip->pagebuf = -1;

        /* Don't allow multipage oob writes with offset */
        if (oob && ops->ooboffs && (ops->ooboffs + ops->ooblen > oobmaxlen)) {
                ret = -EINVAL;
                goto err_out;
        }

        while (1) {
                int bytes = mtd->writesize;
                int cached = writelen > bytes && page != blockmask;
                uint8_t *wbuf = buf;
                int use_bufpoi;
                int part_pagewr = (column || writelen < (mtd->writesize - 1));

                if (part_pagewr)
                        use_bufpoi = 1;
                else
                        use_bufpoi = 0;

                WATCHDOG_RESET();
                /* Partial page write?, or need to use bounce buffer */
                if (use_bufpoi) {
                        pr_debug("%s: using write bounce buffer for buf@%p\n",
                                         __func__, buf);
                        cached = 0;
                        if (part_pagewr)
                                bytes = min_t(int, bytes - column, writelen);
                        chip->pagebuf = -1;
                        memset(chip->buffers->databuf, 0xff, mtd->writesize);
                        memcpy(&chip->buffers->databuf[column], buf, bytes);
                        wbuf = chip->buffers->databuf;
                }

                if (unlikely(oob)) {
                        size_t len = min(oobwritelen, oobmaxlen);
                        oob = nand_fill_oob(mtd, oob, len, ops);
                        oobwritelen -= len;
                } else {
                        /* We still need to erase leftover OOB data */
                        memset(chip->oob_poi, 0xff, mtd->oobsize);
                }
                ret = chip->write_page(mtd, chip, column, bytes, wbuf,
                                        oob_required, page, cached,
                                        (ops->mode == MTD_OPS_RAW));
                if (ret)
                        break;

                writelen -= bytes;
                if (!writelen)
                        break;

                column = 0;
                buf += bytes;
                realpage++;

                page = realpage & chip->pagemask;
                /* Check, if we cross a chip boundary */
                if (!page) {
                        chipnr++;
                        chip->select_chip(mtd, -1);
                        chip->select_chip(mtd, chipnr);
                }
        }

        ops->retlen = ops->len - writelen;
        if (unlikely(oob))
                ops->oobretlen = ops->ooblen;

err_out:
        chip->select_chip(mtd, -1);
        return ret;
}

/**
 * panic_nand_write - [MTD Interface] NAND write with ECC
 * @mtd: MTD device structure
 * @to: offset to write to
 * @len: number of bytes to write
 * @retlen: pointer to variable to store the number of written bytes
 * @buf: the data to write
 *
 * NAND write with ECC. Used when performing writes in interrupt context, this
 * may for example be called by mtdoops when writing an oops while in panic.
 */
static int panic_nand_write(struct mtd_info *mtd, loff_t to, size_t len,
                            size_t *retlen, const uint8_t *buf)
{
        struct nand_chip *chip = mtd_to_nand(mtd);
        struct mtd_oob_ops ops;
        int ret;

        /* Wait for the device to get ready */
        panic_nand_wait(mtd, chip, 400);

        /* Grab the device */
        panic_nand_get_device(chip, mtd, FL_WRITING);

        memset(&ops, 0, sizeof(ops));
        ops.len = len;
        ops.datbuf = (uint8_t *)buf;
        ops.mode = MTD_OPS_PLACE_OOB;

        ret = nand_do_write_ops(mtd, to, &ops);

        *retlen = ops.retlen;
        return ret;
}

/**
 * nand_write - [MTD Interface] NAND write with ECC
 * @mtd: MTD device structure
 * @to: offset to write to
 * @len: number of bytes to write
 * @retlen: pointer to variable to store the number of written bytes
 * @buf: the data to write
 *
 * NAND write with ECC.
 */
static int nand_write(struct mtd_info *mtd, loff_t to, size_t len,
                          size_t *retlen, const uint8_t *buf)
{
        struct mtd_oob_ops ops;
        int ret;

        nand_get_device(mtd, FL_WRITING);
        memset(&ops, 0, sizeof(ops));
        ops.len = len;
        ops.datbuf = (uint8_t *)buf;
        ops.mode = MTD_OPS_PLACE_OOB;
        ret = nand_do_write_ops(mtd, to, &ops);
        *retlen = ops.retlen;
        nand_release_device(mtd);
        return ret;
}

/**
 * nand_do_write_oob - [MTD Interface] NAND write out-of-band
 * @mtd: MTD device structure
 * @to: offset to write to
 * @ops: oob operation description structure
 *
 * NAND write out-of-band.
 */
static int nand_do_write_oob(struct mtd_info *mtd, loff_t to,
                             struct mtd_oob_ops *ops)
{
        int chipnr, page, status, len;
        struct nand_chip *chip = mtd_to_nand(mtd);

        pr_debug("%s: to = 0x%08x, len = %i\n",
                         __func__, (unsigned int)to, (int)ops->ooblen);

        if (ops->mode == MTD_OPS_AUTO_OOB)
                len = chip->ecc.layout->oobavail;
        else
                len = mtd->oobsize;

        /* Do not allow write past end of page */
        if ((ops->ooboffs + ops->ooblen) > len) {
                pr_debug("%s: attempt to write past end of page\n",
                                __func__);
                return -EINVAL;
        }

        if (unlikely(ops->ooboffs >= len)) {
                pr_debug("%s: attempt to start write outside oob\n",
                                __func__);
                return -EINVAL;
        }

        /* Do not allow write past end of device */
        if (unlikely(to >= mtd->size ||
                     ops->ooboffs + ops->ooblen >
                        ((mtd->size >> chip->page_shift) -
                         (to >> chip->page_shift)) * len)) {
                pr_debug("%s: attempt to write beyond end of device\n",
                                __func__);
                return -EINVAL;
        }

        chipnr = (int)(to >> chip->chip_shift);
        chip->select_chip(mtd, chipnr);

        /* Shift to get page */
        page = (int)(to >> chip->page_shift);

        /*
         * Reset the chip. Some chips (like the Toshiba TC5832DC found in one
         * of my DiskOnChip 2000 test units) will clear the whole data page too
         * if we don't do this. I have no clue why, but I seem to have 'fixed'
         * it in the doc2000 driver in August 1999.  dwmw2.
         */
        chip->cmdfunc(mtd, NAND_CMD_RESET, -1, -1);

        /* Check, if it is write protected */
        if (nand_check_wp(mtd)) {
                chip->select_chip(mtd, -1);
                return -EROFS;
        }

        /* Invalidate the page cache, if we write to the cached page */
        if (page == chip->pagebuf)
                chip->pagebuf = -1;

        nand_fill_oob(mtd, ops->oobbuf, ops->ooblen, ops);

        if (ops->mode == MTD_OPS_RAW)
                status = chip->ecc.write_oob_raw(mtd, chip, page & chip->pagemask);
        else
                status = chip->ecc.write_oob(mtd, chip, page & chip->pagemask);

        chip->select_chip(mtd, -1);

        if (status)
                return status;

        ops->oobretlen = ops->ooblen;

        return 0;
}

/**
 * nand_write_oob - [MTD Interface] NAND write data and/or out-of-band
 * @mtd: MTD device structure
 * @to: offset to write to
 * @ops: oob operation description structure
 */
static int nand_write_oob(struct mtd_info *mtd, loff_t to,
                          struct mtd_oob_ops *ops)
{
        int ret = -ENOTSUPP;

        ops->retlen = 0;

        /* Do not allow writes past end of device */
        if (ops->datbuf && (to + ops->len) > mtd->size) {
                pr_debug("%s: attempt to write beyond end of device\n",
                                __func__);
                return -EINVAL;
        }

        nand_get_device(mtd, FL_WRITING);

        switch (ops->mode) {
        case MTD_OPS_PLACE_OOB:
        case MTD_OPS_AUTO_OOB:
        case MTD_OPS_RAW:
                break;

        default:
                goto out;
        }

        if (!ops->datbuf)
                ret = nand_do_write_oob(mtd, to, ops);
        else
                ret = nand_do_write_ops(mtd, to, ops);

out:
        nand_release_device(mtd);
        return ret;
}

/**
 * single_erase - [GENERIC] NAND standard block erase command function
 * @mtd: MTD device structure
 * @page: the page address of the block which will be erased
 *
 * Standard erase command for NAND chips. Returns NAND status.
 */
static int single_erase(struct mtd_info *mtd, int page)
{
        struct nand_chip *chip = mtd_to_nand(mtd);
        /* Send commands to erase a block */
        chip->cmdfunc(mtd, NAND_CMD_ERASE1, -1, page);
        chip->cmdfunc(mtd, NAND_CMD_ERASE2, -1, -1);

        return chip->waitfunc(mtd, chip);
}

/**
 * nand_erase - [MTD Interface] erase block(s)
 * @mtd: MTD device structure
 * @instr: erase instruction
 *
 * Erase one ore more blocks.
 */
static int nand_erase(struct mtd_info *mtd, struct erase_info *instr)
{
        return nand_erase_nand(mtd, instr, 0);
}

/**
 * nand_erase_nand - [INTERN] erase block(s)
 * @mtd: MTD device structure
 * @instr: erase instruction
 * @allowbbt: allow erasing the bbt area
 *
 * Erase one ore more blocks.
 */
int nand_erase_nand(struct mtd_info *mtd, struct erase_info *instr,
                    int allowbbt)
{
        int page, status, pages_per_block, ret, chipnr;
        struct nand_chip *chip = mtd_to_nand(mtd);
        loff_t len;

        pr_debug("%s: start = 0x%012llx, len = %llu\n",
                        __func__, (unsigned long long)instr->addr,
                        (unsigned long long)instr->len);

        if (check_offs_len(mtd, instr->addr, instr->len))
                return -EINVAL;

        /* Grab the lock and see if the device is available */
        nand_get_device(mtd, FL_ERASING);

        /* Shift to get first page */
        page = (int)(instr->addr >> chip->page_shift);
        chipnr = (int)(instr->addr >> chip->chip_shift);

        /* Calculate pages in each block */
        pages_per_block = 1 << (chip->phys_erase_shift - chip->page_shift);

        /* Select the NAND device */
        chip->select_chip(mtd, chipnr);

        /* Check, if it is write protected */
        if (nand_check_wp(mtd)) {
                pr_debug("%s: device is write protected!\n",
                                __func__);
                instr->state = MTD_ERASE_FAILED;
                goto erase_exit;
        }

        /* Loop through the pages */
        len = instr->len;

        instr->state = MTD_ERASING;

        while (len) {
                WATCHDOG_RESET();

                /* Check if we have a bad block, we do not erase bad blocks! */
                if (!instr->scrub && nand_block_checkbad(mtd, ((loff_t) page) <<
                                        chip->page_shift, 0, allowbbt)) {
                        pr_warn("%s: attempt to erase a bad block at page 0x%08x\n",
                                    __func__, page);
                        instr->state = MTD_ERASE_FAILED;
                        goto erase_exit;
                }

                /*
                 * Invalidate the page cache, if we erase the block which
                 * contains the current cached page.
                 */
                if (page <= chip->pagebuf && chip->pagebuf <
                    (page + pages_per_block))
                        chip->pagebuf = -1;

                status = chip->erase(mtd, page & chip->pagemask);

                /*
                 * See if operation failed and additional status checks are
                 * available
                 */
                if ((status & NAND_STATUS_FAIL) && (chip->errstat))
                        status = chip->errstat(mtd, chip, FL_ERASING,
                                               status, page);

                /* See if block erase succeeded */
                if (status & NAND_STATUS_FAIL) {
                        pr_debug("%s: failed erase, page 0x%08x\n",
                                        __func__, page);
                        instr->state = MTD_ERASE_FAILED;
                        instr->fail_addr =
                                ((loff_t)page << chip->page_shift);
                        goto erase_exit;
                }

                /* Increment page address and decrement length */
                len -= (1ULL << chip->phys_erase_shift);
                page += pages_per_block;

                /* Check, if we cross a chip boundary */
                if (len && !(page & chip->pagemask)) {
                        chipnr++;
                        chip->select_chip(mtd, -1);
                        chip->select_chip(mtd, chipnr);
                }
        }
        instr->state = MTD_ERASE_DONE;

erase_exit:

        ret = instr->state == MTD_ERASE_DONE ? 0 : -EIO;

        /* Deselect and wake up anyone waiting on the device */
        chip->select_chip(mtd, -1);
        nand_release_device(mtd);

        /* Do call back function */
        if (!ret)
                mtd_erase_callback(instr);

        /* Return more or less happy */
        return ret;
}

/**
 * nand_sync - [MTD Interface] sync
 * @mtd: MTD device structure
 *
 * Sync is actually a wait for chip ready function.
 */
static void nand_sync(struct mtd_info *mtd)
{
        pr_debug("%s: called\n", __func__);

        /* Grab the lock and see if the device is available */
        nand_get_device(mtd, FL_SYNCING);
        /* Release it and go back */
        nand_release_device(mtd);
}

/**
 * nand_block_isbad - [MTD Interface] Check if block at offset is bad
 * @mtd: MTD device structure
 * @offs: offset relative to mtd start
 */
static int nand_block_isbad(struct mtd_info *mtd, loff_t offs)
{
        return nand_block_checkbad(mtd, offs, 1, 0);
}

/**
 * nand_block_markbad - [MTD Interface] Mark block at the given offset as bad
 * @mtd: MTD device structure
 * @ofs: offset relative to mtd start
 */
static int nand_block_markbad(struct mtd_info *mtd, loff_t ofs)
{
        int ret;

        ret = nand_block_isbad(mtd, ofs);
        if (ret) {
                /* If it was bad already, return success and do nothing */
                if (ret > 0)
                        return 0;
                return ret;
        }

        return nand_block_markbad_lowlevel(mtd, ofs);
}

/**
 * nand_onfi_set_features- [REPLACEABLE] set features for ONFI nand
 * @mtd: MTD device structure
 * @chip: nand chip info structure
 * @addr: feature address.
 * @subfeature_param: the subfeature parameters, a four bytes array.
 */
static int nand_onfi_set_features(struct mtd_info *mtd, struct nand_chip *chip,
                        int addr, uint8_t *subfeature_param)
{
        int status;
        int i;

#ifdef CONFIG_SYS_NAND_ONFI_DETECTION
        if (!chip->onfi_version ||
            !(le16_to_cpu(chip->onfi_params.opt_cmd)
              & ONFI_OPT_CMD_SET_GET_FEATURES))
                return -EINVAL;
#endif

        chip->cmdfunc(mtd, NAND_CMD_SET_FEATURES, addr, -1);
        for (i = 0; i < ONFI_SUBFEATURE_PARAM_LEN; ++i)
                chip->write_byte(mtd, subfeature_param[i]);

        status = chip->waitfunc(mtd, chip);
        if (status & NAND_STATUS_FAIL)
                return -EIO;
        return 0;
}

/**
 * nand_onfi_get_features- [REPLACEABLE] get features for ONFI nand
 * @mtd: MTD device structure
 * @chip: nand chip info structure
 * @addr: feature address.
 * @subfeature_param: the subfeature parameters, a four bytes array.
 */
static int nand_onfi_get_features(struct mtd_info *mtd, struct nand_chip *chip,
                        int addr, uint8_t *subfeature_param)
{
        int i;

#ifdef CONFIG_SYS_NAND_ONFI_DETECTION
        if (!chip->onfi_version ||
            !(le16_to_cpu(chip->onfi_params.opt_cmd)
              & ONFI_OPT_CMD_SET_GET_FEATURES))
                return -EINVAL;
#endif

        /* clear the sub feature parameters */
        memset(subfeature_param, 0, ONFI_SUBFEATURE_PARAM_LEN);

        chip->cmdfunc(mtd, NAND_CMD_GET_FEATURES, addr, -1);
        for (i = 0; i < ONFI_SUBFEATURE_PARAM_LEN; ++i)
                *subfeature_param++ = chip->read_byte(mtd);
        return 0;
}

/* Set default functions */
static void nand_set_defaults(struct nand_chip *chip, int busw)
{
        /* check for proper chip_delay setup, set 20us if not */
        if (!chip->chip_delay)
                chip->chip_delay = 20;

        /* check, if a user supplied command function given */
        if (chip->cmdfunc == NULL)
                chip->cmdfunc = nand_command;

        /* check, if a user supplied wait function given */
        if (chip->waitfunc == NULL)
                chip->waitfunc = nand_wait;

        if (!chip->select_chip)
                chip->select_chip = nand_select_chip;

        /* set for ONFI nand */
        if (!chip->onfi_set_features)
                chip->onfi_set_features = nand_onfi_set_features;
        if (!chip->onfi_get_features)
                chip->onfi_get_features = nand_onfi_get_features;

        /* If called twice, pointers that depend on busw may need to be reset */
        if (!chip->read_byte || chip->read_byte == nand_read_byte)
                chip->read_byte = busw ? nand_read_byte16 : nand_read_byte;
        if (!chip->read_word)
                chip->read_word = nand_read_word;
        if (!chip->block_bad)
                chip->block_bad = nand_block_bad;
        if (!chip->block_markbad)
                chip->block_markbad = nand_default_block_markbad;
        if (!chip->write_buf || chip->write_buf == nand_write_buf)
                chip->write_buf = busw ? nand_write_buf16 : nand_write_buf;
        if (!chip->write_byte || chip->write_byte == nand_write_byte)
                chip->write_byte = busw ? nand_write_byte16 : nand_write_byte;
        if (!chip->read_buf || chip->read_buf == nand_read_buf)
                chip->read_buf = busw ? nand_read_buf16 : nand_read_buf;
        if (!chip->scan_bbt)
                chip->scan_bbt = nand_default_bbt;

        if (!chip->controller) {
                chip->controller = &chip->hwcontrol;
                spin_lock_init(&chip->controller->lock);
                init_waitqueue_head(&chip->controller->wq);
        }

}

/* Sanitize ONFI strings so we can safely print them */
static void sanitize_string(char *s, size_t len)
{
        ssize_t i;

        /* Null terminate */
        s[len - 1] = 0;

        /* Remove non printable chars */
        for (i = 0; i < len - 1; i++) {
                if (s[i] < ' ' || s[i] > 127)
                        s[i] = '?';
        }

        /* Remove trailing spaces */
        strim(s);
}

static u16 onfi_crc16(u16 crc, u8 const *p, size_t len)
{
        int i;
        while (len--) {
                crc ^= *p++ << 8;
                for (i = 0; i < 8; i++)
                        crc = (crc << 1) ^ ((crc & 0x8000) ? 0x8005 : 0);
        }

        return crc;
}

#ifdef CONFIG_SYS_NAND_ONFI_DETECTION
/* Parse the Extended Parameter Page. */
static int nand_flash_detect_ext_param_page(struct mtd_info *mtd,
                struct nand_chip *chip, struct nand_onfi_params *p)
{
        struct onfi_ext_param_page *ep;
        struct onfi_ext_section *s;
        struct onfi_ext_ecc_info *ecc;
        uint8_t *cursor;
        int ret = -EINVAL;
        int len;
        int i;

        len = le16_to_cpu(p->ext_param_page_length) * 16;
        ep = kmalloc(len, GFP_KERNEL);
        if (!ep)
                return -ENOMEM;

        /* Send our own NAND_CMD_PARAM. */
        chip->cmdfunc(mtd, NAND_CMD_PARAM, 0, -1);

        /* Use the Change Read Column command to skip the ONFI param pages. */
        chip->cmdfunc(mtd, NAND_CMD_RNDOUT,
                        sizeof(*p) * p->num_of_param_pages , -1);

        /* Read out the Extended Parameter Page. */
        chip->read_buf(mtd, (uint8_t *)ep, len);
        if ((onfi_crc16(ONFI_CRC_BASE, ((uint8_t *)ep) + 2, len - 2)
                != le16_to_cpu(ep->crc))) {
                pr_debug("fail in the CRC.\n");
                goto ext_out;
        }

        /*
         * Check the signature.
         * Do not strictly follow the ONFI spec, maybe changed in future.
         */
        if (strncmp((char *)ep->sig, "EPPS", 4)) {
                pr_debug("The signature is invalid.\n");
                goto ext_out;
        }

        /* find the ECC section. */
        cursor = (uint8_t *)(ep + 1);
        for (i = 0; i < ONFI_EXT_SECTION_MAX; i++) {
                s = ep->sections + i;
                if (s->type == ONFI_SECTION_TYPE_2)
                        break;
                cursor += s->length * 16;
        }
        if (i == ONFI_EXT_SECTION_MAX) {
                pr_debug("We can not find the ECC section.\n");
                goto ext_out;
        }

        /* get the info we want. */
        ecc = (struct onfi_ext_ecc_info *)cursor;

        if (!ecc->codeword_size) {
                pr_debug("Invalid codeword size\n");
                goto ext_out;
        }

        chip->ecc_strength_ds = ecc->ecc_bits;
        chip->ecc_step_ds = 1 << ecc->codeword_size;
        ret = 0;

ext_out:
        kfree(ep);
        return ret;
}

static int nand_setup_read_retry_micron(struct mtd_info *mtd, int retry_mode)
{
        struct nand_chip *chip = mtd_to_nand(mtd);
        uint8_t feature[ONFI_SUBFEATURE_PARAM_LEN] = {retry_mode};

        return chip->onfi_set_features(mtd, chip, ONFI_FEATURE_ADDR_READ_RETRY,
                        feature);
}

/*
 * Configure chip properties from Micron vendor-specific ONFI table
 */
static void nand_onfi_detect_micron(struct nand_chip *chip,
                struct nand_onfi_params *p)
{
        struct nand_onfi_vendor_micron *micron = (void *)p->vendor;

        if (le16_to_cpu(p->vendor_revision) < 1)
                return;

        chip->read_retries = micron->read_retry_options;
        chip->setup_read_retry = nand_setup_read_retry_micron;
}

/*
 * Check if the NAND chip is ONFI compliant, returns 1 if it is, 0 otherwise.
 */
static int nand_flash_detect_onfi(struct mtd_info *mtd, struct nand_chip *chip,
                                        int *busw)
{
        struct nand_onfi_params *p = &chip->onfi_params;
        int i, j;
        int val;

        /* Try ONFI for unknown chip or LP */
        chip->cmdfunc(mtd, NAND_CMD_READID, 0x20, -1);
        if (chip->read_byte(mtd) != 'O' || chip->read_byte(mtd) != 'N' ||
                chip->read_byte(mtd) != 'F' || chip->read_byte(mtd) != 'I')
                return 0;

        chip->cmdfunc(mtd, NAND_CMD_PARAM, 0, -1);
        for (i = 0; i < 3; i++) {
                for (j = 0; j < sizeof(*p); j++)
                        ((uint8_t *)p)[j] = chip->read_byte(mtd);
                if (onfi_crc16(ONFI_CRC_BASE, (uint8_t *)p, 254) ==
                                le16_to_cpu(p->crc)) {
                        break;
                }
        }

        if (i == 3) {
                pr_err("Could not find valid ONFI parameter page; aborting\n");
                return 0;
        }

        /* Check version */
        val = le16_to_cpu(p->revision);
        if (val & (1 << 5))
                chip->onfi_version = 23;
        else if (val & (1 << 4))
                chip->onfi_version = 22;
        else if (val & (1 << 3))
                chip->onfi_version = 21;
        else if (val & (1 << 2))
                chip->onfi_version = 20;
        else if (val & (1 << 1))
                chip->onfi_version = 10;

        if (!chip->onfi_version) {
                pr_info("unsupported ONFI version: %d\n", val);
                return 0;
        }

        sanitize_string(p->manufacturer, sizeof(p->manufacturer));
        sanitize_string(p->model, sizeof(p->model));
        if (!mtd->name)
                mtd->name = p->model;

        mtd->writesize = le32_to_cpu(p->byte_per_page);

        /*
         * pages_per_block and blocks_per_lun may not be a power-of-2 size
         * (don't ask me who thought of this...). MTD assumes that these
         * dimensions will be power-of-2, so just truncate the remaining area.
         */
        mtd->erasesize = 1 << (fls(le32_to_cpu(p->pages_per_block)) - 1);
        mtd->erasesize *= mtd->writesize;

        mtd->oobsize = le16_to_cpu(p->spare_bytes_per_page);

        /* See erasesize comment */
        chip->chipsize = 1 << (fls(le32_to_cpu(p->blocks_per_lun)) - 1);
        chip->chipsize *= (uint64_t)mtd->erasesize * p->lun_count;
        chip->bits_per_cell = p->bits_per_cell;

        if (onfi_feature(chip) & ONFI_FEATURE_16_BIT_BUS)
                *busw = NAND_BUSWIDTH_16;
        else
                *busw = 0;

        if (p->ecc_bits != 0xff) {
                chip->ecc_strength_ds = p->ecc_bits;
                chip->ecc_step_ds = 512;
        } else if (chip->onfi_version >= 21 &&
                (onfi_feature(chip) & ONFI_FEATURE_EXT_PARAM_PAGE)) {

                /*
                 * The nand_flash_detect_ext_param_page() uses the
                 * Change Read Column command which maybe not supported
                 * by the chip->cmdfunc. So try to update the chip->cmdfunc
                 * now. We do not replace user supplied command function.
                 */
                if (mtd->writesize > 512 && chip->cmdfunc == nand_command)
                        chip->cmdfunc = nand_command_lp;

                /* The Extended Parameter Page is supported since ONFI 2.1. */
                if (nand_flash_detect_ext_param_page(mtd, chip, p))
                        pr_warn("Failed to detect ONFI extended param page\n");
        } else {
                pr_warn("Could not retrieve ONFI ECC requirements\n");
        }

        if (p->jedec_id == NAND_MFR_MICRON)
                nand_onfi_detect_micron(chip, p);

        return 1;
}
#else
static int nand_flash_detect_onfi(struct mtd_info *mtd, struct nand_chip *chip,
                                        int *busw)
{
        return 0;
}
#endif

/*
 * Check if the NAND chip is JEDEC compliant, returns 1 if it is, 0 otherwise.
 */
static int nand_flash_detect_jedec(struct mtd_info *mtd, struct nand_chip *chip,
                                        int *busw)
{
        struct nand_jedec_params *p = &chip->jedec_params;
        struct jedec_ecc_info *ecc;
        int val;
        int i, j;

        /* Try JEDEC for unknown chip or LP */
        chip->cmdfunc(mtd, NAND_CMD_READID, 0x40, -1);
        if (chip->read_byte(mtd) != 'J' || chip->read_byte(mtd) != 'E' ||
                chip->read_byte(mtd) != 'D' || chip->read_byte(mtd) != 'E' ||
                chip->read_byte(mtd) != 'C')
                return 0;

        chip->cmdfunc(mtd, NAND_CMD_PARAM, 0x40, -1);
        for (i = 0; i < 3; i++) {
                for (j = 0; j < sizeof(*p); j++)
                        ((uint8_t *)p)[j] = chip->read_byte(mtd);

                if (onfi_crc16(ONFI_CRC_BASE, (uint8_t *)p, 510) ==
                                le16_to_cpu(p->crc))
                        break;
        }

        if (i == 3) {
                pr_err("Could not find valid JEDEC parameter page; aborting\n");
                return 0;
        }

        /* Check version */
        val = le16_to_cpu(p->revision);
        if (val & (1 << 2))
                chip->jedec_version = 10;
        else if (val & (1 << 1))
                chip->jedec_version = 1; /* vendor specific version */

        if (!chip->jedec_version) {
                pr_info("unsupported JEDEC version: %d\n", val);
                return 0;
        }

        sanitize_string(p->manufacturer, sizeof(p->manufacturer));
        sanitize_string(p->model, sizeof(p->model));
        if (!mtd->name)
                mtd->name = p->model;

        mtd->writesize = le32_to_cpu(p->byte_per_page);

        /* Please reference to the comment for nand_flash_detect_onfi. */
        mtd->erasesize = 1 << (fls(le32_to_cpu(p->pages_per_block)) - 1);
        mtd->erasesize *= mtd->writesize;

        mtd->oobsize = le16_to_cpu(p->spare_bytes_per_page);

        /* Please reference to the comment for nand_flash_detect_onfi. */
        chip->chipsize = 1 << (fls(le32_to_cpu(p->blocks_per_lun)) - 1);
        chip->chipsize *= (uint64_t)mtd->erasesize * p->lun_count;
        chip->bits_per_cell = p->bits_per_cell;

        if (jedec_feature(chip) & JEDEC_FEATURE_16_BIT_BUS)
                *busw = NAND_BUSWIDTH_16;
        else
                *busw = 0;

        /* ECC info */
        ecc = &p->ecc_info[0];

        if (ecc->codeword_size >= 9) {
                chip->ecc_strength_ds = ecc->ecc_bits;
                chip->ecc_step_ds = 1 << ecc->codeword_size;
        } else {
                pr_warn("Invalid codeword size\n");
        }

        return 1;
}

/*
 * nand_id_has_period - Check if an ID string has a given wraparound period
 * @id_data: the ID string
 * @arrlen: the length of the @id_data array
 * @period: the period of repitition
 *
 * Check if an ID string is repeated within a given sequence of bytes at
 * specific repetition interval period (e.g., {0x20,0x01,0x7F,0x20} has a
 * period of 3). This is a helper function for nand_id_len(). Returns non-zero
 * if the repetition has a period of @period; otherwise, returns zero.
 */
static int nand_id_has_period(u8 *id_data, int arrlen, int period)
{
        int i, j;
        for (i = 0; i < period; i++)
                for (j = i + period; j < arrlen; j += period)
                        if (id_data[i] != id_data[j])
                                return 0;
        return 1;
}

/*
 * nand_id_len - Get the length of an ID string returned by CMD_READID
 * @id_data: the ID string
 * @arrlen: the length of the @id_data array

 * Returns the length of the ID string, according to known wraparound/trailing
 * zero patterns. If no pattern exists, returns the length of the array.
 */
static int nand_id_len(u8 *id_data, int arrlen)
{
        int last_nonzero, period;

        /* Find last non-zero byte */
        for (last_nonzero = arrlen - 1; last_nonzero >= 0; last_nonzero--)
                if (id_data[last_nonzero])
                        break;

        /* All zeros */
        if (last_nonzero < 0)
                return 0;

        /* Calculate wraparound period */
        for (period = 1; period < arrlen; period++)
                if (nand_id_has_period(id_data, arrlen, period))
                        break;

        /* There's a repeated pattern */
        if (period < arrlen)
                return period;

        /* There are trailing zeros */
        if (last_nonzero < arrlen - 1)
                return last_nonzero + 1;

        /* No pattern detected */
        return arrlen;
}

/* Extract the bits of per cell from the 3rd byte of the extended ID */
static int nand_get_bits_per_cell(u8 cellinfo)
{
        int bits;

        bits = cellinfo & NAND_CI_CELLTYPE_MSK;
        bits >>= NAND_CI_CELLTYPE_SHIFT;
        return bits + 1;
}

/*
 * Many new NAND share similar device ID codes, which represent the size of the
 * chip. The rest of the parameters must be decoded according to generic or
 * manufacturer-specific "extended ID" decoding patterns.
 */
static void nand_decode_ext_id(struct mtd_info *mtd, struct nand_chip *chip,
                                u8 id_data[8], int *busw)
{
        int extid, id_len;
        /* The 3rd id byte holds MLC / multichip data */
        chip->bits_per_cell = nand_get_bits_per_cell(id_data[2]);
        /* The 4th id byte is the important one */
        extid = id_data[3];

        id_len = nand_id_len(id_data, 8);

        /*
         * Field definitions are in the following datasheets:
         * Old style (4,5 byte ID): Samsung K9GAG08U0M (p.32)
         * New Samsung (6 byte ID): Samsung K9GAG08U0F (p.44)
         * Hynix MLC   (6 byte ID): Hynix H27UBG8T2B (p.22)
         *
         * Check for ID length, non-zero 6th byte, cell type, and Hynix/Samsung
         * ID to decide what to do.
         */
        if (id_len == 6 && id_data[0] == NAND_MFR_SAMSUNG &&
                        !nand_is_slc(chip) && id_data[5] != 0x00) {
                /* Calc pagesize */
                mtd->writesize = 2048 << (extid & 0x03);
                extid >>= 2;
                /* Calc oobsize */
                switch (((extid >> 2) & 0x04) | (extid & 0x03)) {
                case 1:
                        mtd->oobsize = 128;
                        break;
                case 2:
                        mtd->oobsize = 218;
                        break;
                case 3:
                        mtd->oobsize = 400;
                        break;
                case 4:
                        mtd->oobsize = 436;
                        break;
                case 5:
                        mtd->oobsize = 512;
                        break;
                case 6:
                        mtd->oobsize = 640;
                        break;
                case 7:
                default: /* Other cases are "reserved" (unknown) */
                        mtd->oobsize = 1024;
                        break;
                }
                extid >>= 2;
                /* Calc blocksize */
                mtd->erasesize = (128 * 1024) <<
                        (((extid >> 1) & 0x04) | (extid & 0x03));
                *busw = 0;
        } else if (id_len == 6 && id_data[0] == NAND_MFR_HYNIX &&
                        !nand_is_slc(chip)) {
                unsigned int tmp;

                /* Calc pagesize */
                mtd->writesize = 2048 << (extid & 0x03);
                extid >>= 2;
                /* Calc oobsize */
                switch (((extid >> 2) & 0x04) | (extid & 0x03)) {
                case 0:
                        mtd->oobsize = 128;
                        break;
                case 1:
                        mtd->oobsize = 224;
                        break;
                case 2:
                        mtd->oobsize = 448;
                        break;
                case 3:
                        mtd->oobsize = 64;
                        break;
                case 4:
                        mtd->oobsize = 32;
                        break;
                case 5:
                        mtd->oobsize = 16;
                        break;
                default:
                        mtd->oobsize = 640;
                        break;
                }
                extid >>= 2;
                /* Calc blocksize */
                tmp = ((extid >> 1) & 0x04) | (extid & 0x03);
                if (tmp < 0x03)
                        mtd->erasesize = (128 * 1024) << tmp;
                else if (tmp == 0x03)
                        mtd->erasesize = 768 * 1024;
                else
                        mtd->erasesize = (64 * 1024) << tmp;
                *busw = 0;
        } else {
                /* Calc pagesize */
                mtd->writesize = 1024 << (extid & 0x03);
                extid >>= 2;
                /* Calc oobsize */
                mtd->oobsize = (8 << (extid & 0x01)) *
                        (mtd->writesize >> 9);
                extid >>= 2;
                /* Calc blocksize. Blocksize is multiples of 64KiB */
                mtd->erasesize = (64 * 1024) << (extid & 0x03);
                extid >>= 2;
                /* Get buswidth information */
                *busw = (extid & 0x01) ? NAND_BUSWIDTH_16 : 0;

                /*
                 * Toshiba 24nm raw SLC (i.e., not BENAND) have 32B OOB per
                 * 512B page. For Toshiba SLC, we decode the 5th/6th byte as
                 * follows:
                 * - ID byte 6, bits[2:0]: 100b -> 43nm, 101b -> 32nm,
                 *                         110b -> 24nm
                 * - ID byte 5, bit[7]:    1 -> BENAND, 0 -> raw SLC
                 */
                if (id_len >= 6 && id_data[0] == NAND_MFR_TOSHIBA &&
                                nand_is_slc(chip) &&
                                (id_data[5] & 0x7) == 0x6 /* 24nm */ &&
                                !(id_data[4] & 0x80) /* !BENAND */) {
                        mtd->oobsize = 32 * mtd->writesize >> 9;
                }

        }
}

/*
 * Old devices have chip data hardcoded in the device ID table. nand_decode_id
 * decodes a matching ID table entry and assigns the MTD size parameters for
 * the chip.
 */
static void nand_decode_id(struct mtd_info *mtd, struct nand_chip *chip,
                                struct nand_flash_dev *type, u8 id_data[8],
                                int *busw)
{
        int maf_id = id_data[0];

        mtd->erasesize = type->erasesize;
        mtd->writesize = type->pagesize;
        mtd->oobsize = mtd->writesize / 32;
        *busw = type->options & NAND_BUSWIDTH_16;

        /* All legacy ID NAND are small-page, SLC */
        chip->bits_per_cell = 1;

        /*
         * Check for Spansion/AMD ID + repeating 5th, 6th byte since
         * some Spansion chips have erasesize that conflicts with size
         * listed in nand_ids table.
         * Data sheet (5 byte ID): Spansion S30ML-P ORNAND (p.39)
         */
        if (maf_id == NAND_MFR_AMD && id_data[4] != 0x00 && id_data[5] == 0x00
                        && id_data[6] == 0x00 && id_data[7] == 0x00
                        && mtd->writesize == 512) {
                mtd->erasesize = 128 * 1024;
                mtd->erasesize <<= ((id_data[3] & 0x03) << 1);
        }
}

/*
 * Set the bad block marker/indicator (BBM/BBI) patterns according to some
 * heuristic patterns using various detected parameters (e.g., manufacturer,
 * page size, cell-type information).
 */
static void nand_decode_bbm_options(struct mtd_info *mtd,
                                    struct nand_chip *chip, u8 id_data[8])
{
        int maf_id = id_data[0];

        /* Set the bad block position */
        if (mtd->writesize > 512 || (chip->options & NAND_BUSWIDTH_16))
                chip->badblockpos = NAND_LARGE_BADBLOCK_POS;
        else
                chip->badblockpos = NAND_SMALL_BADBLOCK_POS;

        /*
         * Bad block marker is stored in the last page of each block on Samsung
         * and Hynix MLC devices; stored in first two pages of each block on
         * Micron devices with 2KiB pages and on SLC Samsung, Hynix, Toshiba,
         * AMD/Spansion, and Macronix.  All others scan only the first page.
         */
        if (!nand_is_slc(chip) &&
                        (maf_id == NAND_MFR_SAMSUNG ||
                         maf_id == NAND_MFR_HYNIX))
                chip->bbt_options |= NAND_BBT_SCANLASTPAGE;
        else if ((nand_is_slc(chip) &&
                                (maf_id == NAND_MFR_SAMSUNG ||
                                 maf_id == NAND_MFR_HYNIX ||
                                 maf_id == NAND_MFR_TOSHIBA ||
                                 maf_id == NAND_MFR_AMD ||
                                 maf_id == NAND_MFR_MACRONIX)) ||
                        (mtd->writesize == 2048 &&
                         maf_id == NAND_MFR_MICRON))
                chip->bbt_options |= NAND_BBT_SCAN2NDPAGE;
}

static inline bool is_full_id_nand(struct nand_flash_dev *type)
{
        return type->id_len;
}

static bool find_full_id_nand(struct mtd_info *mtd, struct nand_chip *chip,
                   struct nand_flash_dev *type, u8 *id_data, int *busw)
{
        if (!strncmp((char *)type->id, (char *)id_data, type->id_len)) {
                mtd->writesize = type->pagesize;
                mtd->erasesize = type->erasesize;
                mtd->oobsize = type->oobsize;

                chip->bits_per_cell = nand_get_bits_per_cell(id_data[2]);
                chip->chipsize = (uint64_t)type->chipsize << 20;
                chip->options |= type->options;
                chip->ecc_strength_ds = NAND_ECC_STRENGTH(type);
                chip->ecc_step_ds = NAND_ECC_STEP(type);
                chip->onfi_timing_mode_default =
                                        type->onfi_timing_mode_default;

                *busw = type->options & NAND_BUSWIDTH_16;

                if (!mtd->name)
                        mtd->name = type->name;

                return true;
        }
        return false;
}

/*
 * Get the flash and manufacturer id and lookup if the type is supported.
 */
static struct nand_flash_dev *nand_get_flash_type(struct mtd_info *mtd,
                                                  struct nand_chip *chip,
                                                  int *maf_id, int *dev_id,
                                                  struct nand_flash_dev *type)
{
        int busw;
        int i, maf_idx;
        u8 id_data[8];

        /* Select the device */
        chip->select_chip(mtd, 0);

        /*
         * Reset the chip, required by some chips (e.g. Micron MT29FxGxxxxx)
         * after power-up.
         */
        chip->cmdfunc(mtd, NAND_CMD_RESET, -1, -1);

        /* Send the command for reading device ID */
        chip->cmdfunc(mtd, NAND_CMD_READID, 0x00, -1);

        /* Read manufacturer and device IDs */
        *maf_id = chip->read_byte(mtd);
        *dev_id = chip->read_byte(mtd);

        /*
         * Try again to make sure, as some systems the bus-hold or other
         * interface concerns can cause random data which looks like a
         * possibly credible NAND flash to appear. If the two results do
         * not match, ignore the device completely.
         */

        chip->cmdfunc(mtd, NAND_CMD_READID, 0x00, -1);

        /* Read entire ID string */
        for (i = 0; i < 8; i++)
                id_data[i] = chip->read_byte(mtd);

        if (id_data[0] != *maf_id || id_data[1] != *dev_id) {
                pr_info("second ID read did not match %02x,%02x against %02x,%02x\n",
                        *maf_id, *dev_id, id_data[0], id_data[1]);
                return ERR_PTR(-ENODEV);
        }

        if (!type)
                type = nand_flash_ids;

        for (; type->name != NULL; type++) {
                if (is_full_id_nand(type)) {
                        if (find_full_id_nand(mtd, chip, type, id_data, &busw))
                                goto ident_done;
                } else if (*dev_id == type->dev_id) {
                                break;
                }
        }

        chip->onfi_version = 0;
        if (!type->name || !type->pagesize) {
                /* Check if the chip is ONFI compliant */
                if (nand_flash_detect_onfi(mtd, chip, &busw))
                        goto ident_done;

                /* Check if the chip is JEDEC compliant */
                if (nand_flash_detect_jedec(mtd, chip, &busw))
                        goto ident_done;
        }

        if (!type->name)
                return ERR_PTR(-ENODEV);

        if (!mtd->name)
                mtd->name = type->name;

        chip->chipsize = (uint64_t)type->chipsize << 20;

        if (!type->pagesize && chip->init_size) {
                /* Set the pagesize, oobsize, erasesize by the driver */
                busw = chip->init_size(mtd, chip, id_data);
        } else if (!type->pagesize) {
                /* Decode parameters from extended ID */
                nand_decode_ext_id(mtd, chip, id_data, &busw);
        } else {
                nand_decode_id(mtd, chip, type, id_data, &busw);
        }
        /* Get chip options */
        chip->options |= type->options;

        /*
         * Check if chip is not a Samsung device. Do not clear the
         * options for chips which do not have an extended id.
         */
        if (*maf_id != NAND_MFR_SAMSUNG && !type->pagesize)
                chip->options &= ~NAND_SAMSUNG_LP_OPTIONS;
ident_done:

        /* Try to identify manufacturer */
        for (maf_idx = 0; nand_manuf_ids[maf_idx].id != 0x0; maf_idx++) {
                if (nand_manuf_ids[maf_idx].id == *maf_id)
                        break;
        }

        if (chip->options & NAND_BUSWIDTH_AUTO) {
                WARN_ON(chip->options & NAND_BUSWIDTH_16);
                chip->options |= busw;
                nand_set_defaults(chip, busw);
        } else if (busw != (chip->options & NAND_BUSWIDTH_16)) {
                /*
                 * Check, if buswidth is correct. Hardware drivers should set
                 * chip correct!
                 */
                pr_info("device found, Manufacturer ID: 0x%02x, Chip ID: 0x%02x\n",
                        *maf_id, *dev_id);
                pr_info("%s %s\n", nand_manuf_ids[maf_idx].name, mtd->name);
                pr_warn("bus width %d instead %d bit\n",
                           (chip->options & NAND_BUSWIDTH_16) ? 16 : 8,
                           busw ? 16 : 8);
                return ERR_PTR(-EINVAL);
        }

        nand_decode_bbm_options(mtd, chip, id_data);

        /* Calculate the address shift from the page size */
        chip->page_shift = ffs(mtd->writesize) - 1;
        /* Convert chipsize to number of pages per chip -1 */
        chip->pagemask = (chip->chipsize >> chip->page_shift) - 1;

        chip->bbt_erase_shift = chip->phys_erase_shift =
                ffs(mtd->erasesize) - 1;
        if (chip->chipsize & 0xffffffff)
                chip->chip_shift = ffs((unsigned)chip->chipsize) - 1;
        else {
                chip->chip_shift = ffs((unsigned)(chip->chipsize >> 32));
                chip->chip_shift += 32 - 1;
        }

        chip->badblockbits = 8;
        chip->erase = single_erase;

        /* Do not replace user supplied command function! */
        if (mtd->writesize > 512 && chip->cmdfunc == nand_command)
                chip->cmdfunc = nand_command_lp;

        pr_info("device found, Manufacturer ID: 0x%02x, Chip ID: 0x%02x\n",
                *maf_id, *dev_id);

#ifdef CONFIG_SYS_NAND_ONFI_DETECTION
        if (chip->onfi_version)
                pr_info("%s %s\n", nand_manuf_ids[maf_idx].name,
                                chip->onfi_params.model);
        else if (chip->jedec_version)
                pr_info("%s %s\n", nand_manuf_ids[maf_idx].name,
                                chip->jedec_params.model);
        else
                pr_info("%s %s\n", nand_manuf_ids[maf_idx].name,
                                type->name);
#else
        if (chip->jedec_version)
                pr_info("%s %s\n", nand_manuf_ids[maf_idx].name,
                                chip->jedec_params.model);
        else
                pr_info("%s %s\n", nand_manuf_ids[maf_idx].name,
                                type->name);

        pr_info("%s %s\n", nand_manuf_ids[maf_idx].name,
                type->name);
#endif

        pr_info("%d MiB, %s, erase size: %d KiB, page size: %d, OOB size: %d\n",
                (int)(chip->chipsize >> 20), nand_is_slc(chip) ? "SLC" : "MLC",
                mtd->erasesize >> 10, mtd->writesize, mtd->oobsize);
        return type;
}

/**
 * nand_scan_ident - [NAND Interface] Scan for the NAND device
 * @mtd: MTD device structure
 * @maxchips: number of chips to scan for
 * @table: alternative NAND ID table
 *
 * This is the first phase of the normal nand_scan() function. It reads the
 * flash ID and sets up MTD fields accordingly.
 *
 * The mtd->owner field must be set to the module of the caller.
 */
int nand_scan_ident(struct mtd_info *mtd, int maxchips,
                    struct nand_flash_dev *table)
{
        int i, nand_maf_id, nand_dev_id;
        struct nand_chip *chip = mtd_to_nand(mtd);
        struct nand_flash_dev *type;

        /* Set the default functions */
        nand_set_defaults(chip, chip->options & NAND_BUSWIDTH_16);

        /* Read the flash type */
        type = nand_get_flash_type(mtd, chip, &nand_maf_id,
                                   &nand_dev_id, table);

        if (IS_ERR(type)) {
                if (!(chip->options & NAND_SCAN_SILENT_NODEV))
                        pr_warn("No NAND device found\n");
                chip->select_chip(mtd, -1);
                return PTR_ERR(type);
        }

        chip->select_chip(mtd, -1);

        /* Check for a chip array */
        for (i = 1; i < maxchips; i++) {
                chip->select_chip(mtd, i);
                /* See comment in nand_get_flash_type for reset */
                chip->cmdfunc(mtd, NAND_CMD_RESET, -1, -1);
                /* Send the command for reading device ID */
                chip->cmdfunc(mtd, NAND_CMD_READID, 0x00, -1);
                /* Read manufacturer and device IDs */
                if (nand_maf_id != chip->read_byte(mtd) ||
                    nand_dev_id != chip->read_byte(mtd)) {
                        chip->select_chip(mtd, -1);
                        break;
                }
                chip->select_chip(mtd, -1);
        }

#ifdef DEBUG
        if (i > 1)
                pr_info("%d chips detected\n", i);
#endif

        /* Store the number of chips and calc total size for mtd */
        chip->numchips = i;
        mtd->size = i * chip->chipsize;

        return 0;
}
EXPORT_SYMBOL(nand_scan_ident);

/*
 * Check if the chip configuration meet the datasheet requirements.

 * If our configuration corrects A bits per B bytes and the minimum
 * required correction level is X bits per Y bytes, then we must ensure
 * both of the following are true:
 *
 * (1) A / B >= X / Y
 * (2) A >= X
 *
 * Requirement (1) ensures we can correct for the required bitflip density.
 * Requirement (2) ensures we can correct even when all bitflips are clumped
 * in the same sector.
 */
static bool nand_ecc_strength_good(struct mtd_info *mtd)
{
        struct nand_chip *chip = mtd_to_nand(mtd);
        struct nand_ecc_ctrl *ecc = &chip->ecc;
        int corr, ds_corr;

        if (ecc->size == 0 || chip->ecc_step_ds == 0)
                /* Not enough information */
                return true;

        /*
         * We get the number of corrected bits per page to compare
         * the correction density.
         */
        corr = (mtd->writesize * ecc->strength) / ecc->size;
        ds_corr = (mtd->writesize * chip->ecc_strength_ds) / chip->ecc_step_ds;

        return corr >= ds_corr && ecc->strength >= chip->ecc_strength_ds;
}

/**
 * nand_scan_tail - [NAND Interface] Scan for the NAND device
 * @mtd: MTD device structure
 *
 * This is the second phase of the normal nand_scan() function. It fills out
 * all the uninitialized function pointers with the defaults and scans for a
 * bad block table if appropriate.
 */
int nand_scan_tail(struct mtd_info *mtd)
{
        int i;
        struct nand_chip *chip = mtd_to_nand(mtd);
        struct nand_ecc_ctrl *ecc = &chip->ecc;
        struct nand_buffers *nbuf;

        /* New bad blocks should be marked in OOB, flash-based BBT, or both */
        BUG_ON((chip->bbt_options & NAND_BBT_NO_OOB_BBM) &&
                        !(chip->bbt_options & NAND_BBT_USE_FLASH));

        if (!(chip->options & NAND_OWN_BUFFERS)) {
                nbuf = kzalloc(sizeof(struct nand_buffers), GFP_KERNEL);
                chip->buffers = nbuf;
        } else {
                if (!chip->buffers)
                        return -ENOMEM;
        }

        /* Set the internal oob buffer location, just after the page data */
        chip->oob_poi = chip->buffers->databuf + mtd->writesize;

        /*
         * If no default placement scheme is given, select an appropriate one.
         */
        if (!ecc->layout && (ecc->mode != NAND_ECC_SOFT_BCH)) {
                switch (mtd->oobsize) {
                case 8:
                        ecc->layout = &nand_oob_8;
                        break;
                case 16:
                        ecc->layout = &nand_oob_16;
                        break;
                case 64:
                        ecc->layout = &nand_oob_64;
                        break;
                case 128:
                        ecc->layout = &nand_oob_128;
                        break;
                default:
                        pr_warn("No oob scheme defined for oobsize %d\n",
                                   mtd->oobsize);
                        BUG();
                }
        }

        if (!chip->write_page)
                chip->write_page = nand_write_page;

        /*
         * Check ECC mode, default to software if 3byte/512byte hardware ECC is
         * selected and we have 256 byte pagesize fallback to software ECC
         */

        switch (ecc->mode) {
        case NAND_ECC_HW_OOB_FIRST:
                /* Similar to NAND_ECC_HW, but a separate read_page handle */
                if (!ecc->calculate || !ecc->correct || !ecc->hwctl) {
                        pr_warn("No ECC functions supplied; hardware ECC not possible\n");
                        BUG();
                }
                if (!ecc->read_page)
                        ecc->read_page = nand_read_page_hwecc_oob_first;

        case NAND_ECC_HW:
                /* Use standard hwecc read page function? */
                if (!ecc->read_page)
                        ecc->read_page = nand_read_page_hwecc;
                if (!ecc->write_page)
                        ecc->write_page = nand_write_page_hwecc;
                if (!ecc->read_page_raw)
                        ecc->read_page_raw = nand_read_page_raw;
                if (!ecc->write_page_raw)
                        ecc->write_page_raw = nand_write_page_raw;
                if (!ecc->read_oob)
                        ecc->read_oob = nand_read_oob_std;
                if (!ecc->write_oob)
                        ecc->write_oob = nand_write_oob_std;
                if (!ecc->read_subpage)
                        ecc->read_subpage = nand_read_subpage;
                if (!ecc->write_subpage)
                        ecc->write_subpage = nand_write_subpage_hwecc;

        case NAND_ECC_HW_SYNDROME:
                if ((!ecc->calculate || !ecc->correct || !ecc->hwctl) &&
                    (!ecc->read_page ||
                     ecc->read_page == nand_read_page_hwecc ||
                     !ecc->write_page ||
                     ecc->write_page == nand_write_page_hwecc)) {
                        pr_warn("No ECC functions supplied; hardware ECC not possible\n");
                        BUG();
                }
                /* Use standard syndrome read/write page function? */
                if (!ecc->read_page)
                        ecc->read_page = nand_read_page_syndrome;
                if (!ecc->write_page)
                        ecc->write_page = nand_write_page_syndrome;
                if (!ecc->read_page_raw)
                        ecc->read_page_raw = nand_read_page_raw_syndrome;
                if (!ecc->write_page_raw)
                        ecc->write_page_raw = nand_write_page_raw_syndrome;
                if (!ecc->read_oob)
                        ecc->read_oob = nand_read_oob_syndrome;
                if (!ecc->write_oob)
                        ecc->write_oob = nand_write_oob_syndrome;

                if (mtd->writesize >= ecc->size) {
                        if (!ecc->strength) {
                                pr_warn("Driver must set ecc.strength when using hardware ECC\n");
                                BUG();
                        }
                        break;
                }
                pr_warn("%d byte HW ECC not possible on %d byte page size, fallback to SW ECC\n",
                        ecc->size, mtd->writesize);
                ecc->mode = NAND_ECC_SOFT;

        case NAND_ECC_SOFT:
                ecc->calculate = nand_calculate_ecc;
                ecc->correct = nand_correct_data;
                ecc->read_page = nand_read_page_swecc;
                ecc->read_subpage = nand_read_subpage;
                ecc->write_page = nand_write_page_swecc;
                ecc->read_page_raw = nand_read_page_raw;
                ecc->write_page_raw = nand_write_page_raw;
                ecc->read_oob = nand_read_oob_std;
                ecc->write_oob = nand_write_oob_std;
                if (!ecc->size)
                        ecc->size = 256;
                ecc->bytes = 3;
                ecc->strength = 1;
                break;

        case NAND_ECC_SOFT_BCH:
                if (!mtd_nand_has_bch()) {
                        pr_warn("CONFIG_MTD_NAND_ECC_BCH not enabled\n");
                        BUG();
                }
                ecc->calculate = nand_bch_calculate_ecc;
                ecc->correct = nand_bch_correct_data;
                ecc->read_page = nand_read_page_swecc;
                ecc->read_subpage = nand_read_subpage;
                ecc->write_page = nand_write_page_swecc;
                ecc->read_page_raw = nand_read_page_raw;
                ecc->write_page_raw = nand_write_page_raw;
                ecc->read_oob = nand_read_oob_std;
                ecc->write_oob = nand_write_oob_std;
                /*
                 * Board driver should supply ecc.size and ecc.strength values
                 * to select how many bits are correctable. Otherwise, default
                 * to 4 bits for large page devices.
                 */
                if (!ecc->size && (mtd->oobsize >= 64)) {
                        ecc->size = 512;
                        ecc->strength = 4;
                }

                /* See nand_bch_init() for details. */
                ecc->bytes = DIV_ROUND_UP(
                                ecc->strength * fls(8 * ecc->size), 8);
                ecc->priv = nand_bch_init(mtd, ecc->size, ecc->bytes,
                                               &ecc->layout);
                if (!ecc->priv) {
                        pr_warn("BCH ECC initialization failed!\n");
                        BUG();
                }
                break;

        case NAND_ECC_NONE:
                pr_warn("NAND_ECC_NONE selected by board driver. This is not recommended!\n");
                ecc->read_page = nand_read_page_raw;
                ecc->write_page = nand_write_page_raw;
                ecc->read_oob = nand_read_oob_std;
                ecc->read_page_raw = nand_read_page_raw;
                ecc->write_page_raw = nand_write_page_raw;
                ecc->write_oob = nand_write_oob_std;
                ecc->size = mtd->writesize;
                ecc->bytes = 0;
                ecc->strength = 0;
                break;

        default:
                pr_warn("Invalid NAND_ECC_MODE %d\n", ecc->mode);
                BUG();
        }

        /* For many systems, the standard OOB write also works for raw */
        if (!ecc->read_oob_raw)
                ecc->read_oob_raw = ecc->read_oob;
        if (!ecc->write_oob_raw)
                ecc->write_oob_raw = ecc->write_oob;

        /*
         * The number of bytes available for a client to place data into
         * the out of band area.
         */
        ecc->layout->oobavail = 0;
        for (i = 0; ecc->layout->oobfree[i].length
                        && i < ARRAY_SIZE(ecc->layout->oobfree); i++)
                ecc->layout->oobavail += ecc->layout->oobfree[i].length;
        mtd->oobavail = ecc->layout->oobavail;

        /* ECC sanity check: warn if it's too weak */
        if (!nand_ecc_strength_good(mtd))
                pr_warn("WARNING: %s: the ECC used on your system is too weak compared to the one required by the NAND chip\n",
                        mtd->name);

        /*
         * Set the number of read / write steps for one page depending on ECC
         * mode.
         */
        ecc->steps = mtd->writesize / ecc->size;
        if (ecc->steps * ecc->size != mtd->writesize) {
                pr_warn("Invalid ECC parameters\n");
                BUG();
        }
        ecc->total = ecc->steps * ecc->bytes;

        /* Allow subpage writes up to ecc.steps. Not possible for MLC flash */
        if (!(chip->options & NAND_NO_SUBPAGE_WRITE) && nand_is_slc(chip)) {
                switch (ecc->steps) {
                case 2:
                        mtd->subpage_sft = 1;
                        break;
                case 4:
                case 8:
                case 16:
                        mtd->subpage_sft = 2;
                        break;
                }
        }
        chip->subpagesize = mtd->writesize >> mtd->subpage_sft;

        /* Initialize state */
        chip->state = FL_READY;

        /* Invalidate the pagebuffer reference */
        chip->pagebuf = -1;

        /* Large page NAND with SOFT_ECC should support subpage reads */
        switch (ecc->mode) {
        case NAND_ECC_SOFT:
        case NAND_ECC_SOFT_BCH:
                if (chip->page_shift > 9)
                        chip->options |= NAND_SUBPAGE_READ;
                break;

        default:
                break;
        }

        /* Fill in remaining MTD driver data */
        mtd->type = nand_is_slc(chip) ? MTD_NANDFLASH : MTD_MLCNANDFLASH;
        mtd->flags = (chip->options & NAND_ROM) ? MTD_CAP_ROM :
                                                MTD_CAP_NANDFLASH;
        mtd->_erase = nand_erase;
        mtd->_read = nand_read;
        mtd->_write = nand_write;
        mtd->_panic_write = panic_nand_write;
        mtd->_read_oob = nand_read_oob;
        mtd->_write_oob = nand_write_oob;
        mtd->_sync = nand_sync;
        mtd->_lock = NULL;
        mtd->_unlock = NULL;
        mtd->_block_isreserved = nand_block_isreserved;
        mtd->_block_isbad = nand_block_isbad;
        mtd->_block_markbad = nand_block_markbad;
        mtd->writebufsize = mtd->writesize;

        /* propagate ecc info to mtd_info */
        mtd->ecclayout = ecc->layout;
        mtd->ecc_strength = ecc->strength;
        mtd->ecc_step_size = ecc->size;
        /*
         * Initialize bitflip_threshold to its default prior scan_bbt() call.
         * scan_bbt() might invoke mtd_read(), thus bitflip_threshold must be
         * properly set.
         */
        if (!mtd->bitflip_threshold)
                mtd->bitflip_threshold = DIV_ROUND_UP(mtd->ecc_strength * 3, 4);

        return 0;
}
EXPORT_SYMBOL(nand_scan_tail);

/*
 * is_module_text_address() isn't exported, and it's mostly a pointless
 * test if this is a module _anyway_ -- they'd have to try _really_ hard
 * to call us from in-kernel code if the core NAND support is modular.
 */
#ifdef MODULE
#define caller_is_module() (1)
#else
#define caller_is_module() \
        is_module_text_address((unsigned long)__builtin_return_address(0))
#endif

/**
 * nand_scan - [NAND Interface] Scan for the NAND device
 * @mtd: MTD device structure
 * @maxchips: number of chips to scan for
 *
 * This fills out all the uninitialized function pointers with the defaults.
 * The flash ID is read and the mtd/chip structures are filled with the
 * appropriate values. The mtd->owner field must be set to the module of the
 * caller.
 */
int nand_scan(struct mtd_info *mtd, int maxchips)
{
        int ret;

        /* Many callers got this wrong, so check for it for a while... */
        if (!mtd->owner && caller_is_module()) {
                pr_crit("%s called with NULL mtd->owner!\n", __func__);
                BUG();
        }

        ret = nand_scan_ident(mtd, maxchips, NULL);
        if (!ret)
                ret = nand_scan_tail(mtd);
        return ret;
}
EXPORT_SYMBOL(nand_scan);

module_init(nand_base_init);
module_exit(nand_base_exit);

MODULE_LICENSE("GPL");
MODULE_AUTHOR("Steven J. Hill <sjhill@realitydiluted.com>");
MODULE_AUTHOR("Thomas Gleixner <tglx@linutronix.de>");
MODULE_DESCRIPTION("Generic NAND flash driver code");