[people/ms/u-boot.git] / common / cmd_i2c.c

/*
 * (C) Copyright 2009
 * Sergey Kubushyn, himself, ksi@koi8.net
 *
 * Changes for unified multibus/multiadapter I2C support.
 *
 * (C) Copyright 2001
 * Gerald Van Baren, Custom IDEAS, vanbaren@cideas.com.
 *
 * SPDX-License-Identifier:     GPL-2.0+
 */

/*
 * I2C Functions similar to the standard memory functions.
 *
 * There are several parameters in many of the commands that bear further
 * explanations:
 *
 * {i2c_chip} is the I2C chip address (the first byte sent on the bus).
 *   Each I2C chip on the bus has a unique address.  On the I2C data bus,
 *   the address is the upper seven bits and the LSB is the "read/write"
 *   bit.  Note that the {i2c_chip} address specified on the command
 *   line is not shifted up: e.g. a typical EEPROM memory chip may have
 *   an I2C address of 0x50, but the data put on the bus will be 0xA0
 *   for write and 0xA1 for read.  This "non shifted" address notation
 *   matches at least half of the data sheets :-/.
 *
 * {addr} is the address (or offset) within the chip.  Small memory
 *   chips have 8 bit addresses.  Large memory chips have 16 bit
 *   addresses.  Other memory chips have 9, 10, or 11 bit addresses.
 *   Many non-memory chips have multiple registers and {addr} is used
 *   as the register index.  Some non-memory chips have only one register
 *   and therefore don't need any {addr} parameter.
 *
 *   The default {addr} parameter is one byte (.1) which works well for
 *   memories and registers with 8 bits of address space.
 *
 *   You can specify the length of the {addr} field with the optional .0,
 *   .1, or .2 modifier (similar to the .b, .w, .l modifier).  If you are
 *   manipulating a single register device which doesn't use an address
 *   field, use "0.0" for the address and the ".0" length field will
 *   suppress the address in the I2C data stream.  This also works for
 *   successive reads using the I2C auto-incrementing memory pointer.
 *
 *   If you are manipulating a large memory with 2-byte addresses, use
 *   the .2 address modifier, e.g. 210.2 addresses location 528 (decimal).
 *
 *   Then there are the unfortunate memory chips that spill the most
 *   significant 1, 2, or 3 bits of address into the chip address byte.
 *   This effectively makes one chip (logically) look like 2, 4, or
 *   8 chips.  This is handled (awkwardly) by #defining
 *   CONFIG_SYS_I2C_EEPROM_ADDR_OVERFLOW and using the .1 modifier on the
 *   {addr} field (since .1 is the default, it doesn't actually have to
 *   be specified).  Examples: given a memory chip at I2C chip address
 *   0x50, the following would happen...
 *     i2c md 50 0 10   display 16 bytes starting at 0x000
 *                      On the bus: <S> A0 00 <E> <S> A1 <rd> ... <rd>
 *     i2c md 50 100 10 display 16 bytes starting at 0x100
 *                      On the bus: <S> A2 00 <E> <S> A3 <rd> ... <rd>
 *     i2c md 50 210 10 display 16 bytes starting at 0x210
 *                      On the bus: <S> A4 10 <E> <S> A5 <rd> ... <rd>
 *   This is awfully ugly.  It would be nice if someone would think up
 *   a better way of handling this.
 *
 * Adapted from cmd_mem.c which is copyright Wolfgang Denk (wd@denx.de).
 */

#include <common.h>
#include <bootretry.h>
#include <cli.h>
#include <command.h>
#include <edid.h>
#include <environment.h>
#include <i2c.h>
#include <malloc.h>
#include <asm/byteorder.h>
#include <linux/compiler.h>

DECLARE_GLOBAL_DATA_PTR;

/* Display values from last command.
 * Memory modify remembered values are different from display memory.
 */
static uchar    i2c_dp_last_chip;
static uint     i2c_dp_last_addr;
static uint     i2c_dp_last_alen;
static uint     i2c_dp_last_length = 0x10;

static uchar    i2c_mm_last_chip;
static uint     i2c_mm_last_addr;
static uint     i2c_mm_last_alen;

/* If only one I2C bus is present, the list of devices to ignore when
 * the probe command is issued is represented by a 1D array of addresses.
 * When multiple buses are present, the list is an array of bus-address
 * pairs.  The following macros take care of this */

#if defined(CONFIG_SYS_I2C_NOPROBES)
#if defined(CONFIG_SYS_I2C) || defined(CONFIG_I2C_MULTI_BUS)
static struct
{
        uchar   bus;
        uchar   addr;
} i2c_no_probes[] = CONFIG_SYS_I2C_NOPROBES;
#define GET_BUS_NUM     i2c_get_bus_num()
#define COMPARE_BUS(b,i)        (i2c_no_probes[(i)].bus == (b))
#define COMPARE_ADDR(a,i)       (i2c_no_probes[(i)].addr == (a))
#define NO_PROBE_ADDR(i)        i2c_no_probes[(i)].addr
#else           /* single bus */
static uchar i2c_no_probes[] = CONFIG_SYS_I2C_NOPROBES;
#define GET_BUS_NUM     0
#define COMPARE_BUS(b,i)        ((b) == 0)      /* Make compiler happy */
#define COMPARE_ADDR(a,i)       (i2c_no_probes[(i)] == (a))
#define NO_PROBE_ADDR(i)        i2c_no_probes[(i)]
#endif  /* defined(CONFIG_SYS_I2C) */
#endif

#define DISP_LINE_LEN   16

/**
 * i2c_init_board() - Board-specific I2C bus init
 *
 * This function is the default no-op implementation of I2C bus
 * initialization. This function can be overriden by board-specific
 * implementation if needed.
 */
__weak
void i2c_init_board(void)
{
}

/* TODO: Implement architecture-specific get/set functions */

/**
 * i2c_get_bus_speed() - Return I2C bus speed
 *
 * This function is the default implementation of function for retrieveing
 * the current I2C bus speed in Hz.
 *
 * A driver implementing runtime switching of I2C bus speed must override
 * this function to report the speed correctly. Simple or legacy drivers
 * can use this fallback.
 *
 * Returns I2C bus speed in Hz.
 */
#if !defined(CONFIG_SYS_I2C)
/*
 * TODO: Implement architecture-specific get/set functions
 * Should go away, if we switched completely to new multibus support
 */
__weak
unsigned int i2c_get_bus_speed(void)
{
        return CONFIG_SYS_I2C_SPEED;
}

/**
 * i2c_set_bus_speed() - Configure I2C bus speed
 * @speed:      Newly set speed of the I2C bus in Hz
 *
 * This function is the default implementation of function for setting
 * the I2C bus speed in Hz.
 *
 * A driver implementing runtime switching of I2C bus speed must override
 * this function to report the speed correctly. Simple or legacy drivers
 * can use this fallback.
 *
 * Returns zero on success, negative value on error.
 */
__weak
int i2c_set_bus_speed(unsigned int speed)
{
        if (speed != CONFIG_SYS_I2C_SPEED)
                return -1;

        return 0;
}
#endif

/**
 * get_alen() - Small parser helper function to get address length
 *
 * Returns the address length.
 */
static uint get_alen(char *arg)
{
        int     j;
        int     alen;

        alen = 1;
        for (j = 0; j < 8; j++) {
                if (arg[j] == '.') {
                        alen = arg[j+1] - '0';
                        break;
                } else if (arg[j] == '\0')
                        break;
        }
        return alen;
}

/**
 * do_i2c_read() - Handle the "i2c read" command-line command
 * @cmdtp:      Command data struct pointer
 * @flag:       Command flag
 * @argc:       Command-line argument count
 * @argv:       Array of command-line arguments
 *
 * Returns zero on success, CMD_RET_USAGE in case of misuse and negative
 * on error.
 *
 * Syntax:
 *      i2c read {i2c_chip} {devaddr}{.0, .1, .2} {len} {memaddr}
 */
static int do_i2c_read ( cmd_tbl_t *cmdtp, int flag, int argc, char * const argv[])
{
        u_char  chip;
        uint    devaddr, alen, length;
        u_char  *memaddr;

        if (argc != 5)
                return CMD_RET_USAGE;

        /*
         * I2C chip address
         */
        chip = simple_strtoul(argv[1], NULL, 16);

        /*
         * I2C data address within the chip.  This can be 1 or
         * 2 bytes long.  Some day it might be 3 bytes long :-).
         */
        devaddr = simple_strtoul(argv[2], NULL, 16);
        alen = get_alen(argv[2]);
        if (alen > 3)
                return CMD_RET_USAGE;

        /*
         * Length is the number of objects, not number of bytes.
         */
        length = simple_strtoul(argv[3], NULL, 16);

        /*
         * memaddr is the address where to store things in memory
         */
        memaddr = (u_char *)simple_strtoul(argv[4], NULL, 16);

        if (i2c_read(chip, devaddr, alen, memaddr, length) != 0) {
                puts ("Error reading the chip.\n");
                return 1;
        }
        return 0;
}

static int do_i2c_write(cmd_tbl_t *cmdtp, int flag, int argc, char * const argv[])
{
        u_char  chip;
        uint    devaddr, alen, length;
        u_char  *memaddr;

        if (argc != 5)
                return cmd_usage(cmdtp);

        /*
         * memaddr is the address where to store things in memory
         */
        memaddr = (u_char *)simple_strtoul(argv[1], NULL, 16);

        /*
         * I2C chip address
         */
        chip = simple_strtoul(argv[2], NULL, 16);

        /*
         * I2C data address within the chip.  This can be 1 or
         * 2 bytes long.  Some day it might be 3 bytes long :-).
         */
        devaddr = simple_strtoul(argv[3], NULL, 16);
        alen = get_alen(argv[3]);
        if (alen > 3)
                return cmd_usage(cmdtp);

        /*
         * Length is the number of objects, not number of bytes.
         */
        length = simple_strtoul(argv[4], NULL, 16);

        while (length-- > 0) {
                if (i2c_write(chip, devaddr++, alen, memaddr++, 1) != 0) {
                        puts("Error writing to the chip.\n");
                        return 1;
                }
/*
 * No write delay with FRAM devices.
 */
#if !defined(CONFIG_SYS_I2C_FRAM)
                udelay(11000);
#endif
        }
        return 0;
}

/**
 * do_i2c_md() - Handle the "i2c md" command-line command
 * @cmdtp:      Command data struct pointer
 * @flag:       Command flag
 * @argc:       Command-line argument count
 * @argv:       Array of command-line arguments
 *
 * Returns zero on success, CMD_RET_USAGE in case of misuse and negative
 * on error.
 *
 * Syntax:
 *      i2c md {i2c_chip} {addr}{.0, .1, .2} {len}
 */
static int do_i2c_md ( cmd_tbl_t *cmdtp, int flag, int argc, char * const argv[])
{
        u_char  chip;
        uint    addr, alen, length;
        int     j, nbytes, linebytes;

        /* We use the last specified parameters, unless new ones are
         * entered.
         */
        chip   = i2c_dp_last_chip;
        addr   = i2c_dp_last_addr;
        alen   = i2c_dp_last_alen;
        length = i2c_dp_last_length;

        if (argc < 3)
                return CMD_RET_USAGE;

        if ((flag & CMD_FLAG_REPEAT) == 0) {
                /*
                 * New command specified.
                 */

                /*
                 * I2C chip address
                 */
                chip = simple_strtoul(argv[1], NULL, 16);

                /*
                 * I2C data address within the chip.  This can be 1 or
                 * 2 bytes long.  Some day it might be 3 bytes long :-).
                 */
                addr = simple_strtoul(argv[2], NULL, 16);
                alen = get_alen(argv[2]);
                if (alen > 3)
                        return CMD_RET_USAGE;

                /*
                 * If another parameter, it is the length to display.
                 * Length is the number of objects, not number of bytes.
                 */
                if (argc > 3)
                        length = simple_strtoul(argv[3], NULL, 16);
        }

        /*
         * Print the lines.
         *
         * We buffer all read data, so we can make sure data is read only
         * once.
         */
        nbytes = length;
        do {
                unsigned char   linebuf[DISP_LINE_LEN];
                unsigned char   *cp;

                linebytes = (nbytes > DISP_LINE_LEN) ? DISP_LINE_LEN : nbytes;

                if (i2c_read(chip, addr, alen, linebuf, linebytes) != 0)
                        puts ("Error reading the chip.\n");
                else {
                        printf("%04x:", addr);
                        cp = linebuf;
                        for (j=0; j<linebytes; j++) {
                                printf(" %02x", *cp++);
                                addr++;
                        }
                        puts ("    ");
                        cp = linebuf;
                        for (j=0; j<linebytes; j++) {
                                if ((*cp < 0x20) || (*cp > 0x7e))
                                        puts (".");
                                else
                                        printf("%c", *cp);
                                cp++;
                        }
                        putc ('\n');
                }
                nbytes -= linebytes;
        } while (nbytes > 0);

        i2c_dp_last_chip   = chip;
        i2c_dp_last_addr   = addr;
        i2c_dp_last_alen   = alen;
        i2c_dp_last_length = length;

        return 0;
}

/**
 * do_i2c_mw() - Handle the "i2c mw" command-line command
 * @cmdtp:      Command data struct pointer
 * @flag:       Command flag
 * @argc:       Command-line argument count
 * @argv:       Array of command-line arguments
 *
 * Returns zero on success, CMD_RET_USAGE in case of misuse and negative
 * on error.
 *
 * Syntax:
 *      i2c mw {i2c_chip} {addr}{.0, .1, .2} {data} [{count}]
 */
static int do_i2c_mw ( cmd_tbl_t *cmdtp, int flag, int argc, char * const argv[])
{
        uchar   chip;
        ulong   addr;
        uint    alen;
        uchar   byte;
        int     count;

        if ((argc < 4) || (argc > 5))
                return CMD_RET_USAGE;

        /*
         * Chip is always specified.
         */
        chip = simple_strtoul(argv[1], NULL, 16);

        /*
         * Address is always specified.
         */
        addr = simple_strtoul(argv[2], NULL, 16);
        alen = get_alen(argv[2]);
        if (alen > 3)
                return CMD_RET_USAGE;

        /*
         * Value to write is always specified.
         */
        byte = simple_strtoul(argv[3], NULL, 16);

        /*
         * Optional count
         */
        if (argc == 5)
                count = simple_strtoul(argv[4], NULL, 16);
        else
                count = 1;

        while (count-- > 0) {
                if (i2c_write(chip, addr++, alen, &byte, 1) != 0)
                        puts ("Error writing the chip.\n");
                /*
                 * Wait for the write to complete.  The write can take
                 * up to 10mSec (we allow a little more time).
                 */
/*
 * No write delay with FRAM devices.
 */
#if !defined(CONFIG_SYS_I2C_FRAM)
                udelay(11000);
#endif
        }

        return 0;
}

/**
 * do_i2c_crc() - Handle the "i2c crc32" command-line command
 * @cmdtp:      Command data struct pointer
 * @flag:       Command flag
 * @argc:       Command-line argument count
 * @argv:       Array of command-line arguments
 *
 * Calculate a CRC on memory
 *
 * Returns zero on success, CMD_RET_USAGE in case of misuse and negative
 * on error.
 *
 * Syntax:
 *      i2c crc32 {i2c_chip} {addr}{.0, .1, .2} {count}
 */
static int do_i2c_crc (cmd_tbl_t *cmdtp, int flag, int argc, char * const argv[])
{
        uchar   chip;
        ulong   addr;
        uint    alen;
        int     count;
        uchar   byte;
        ulong   crc;
        ulong   err;

        if (argc < 4)
                return CMD_RET_USAGE;

        /*
         * Chip is always specified.
         */
        chip = simple_strtoul(argv[1], NULL, 16);

        /*
         * Address is always specified.
         */
        addr = simple_strtoul(argv[2], NULL, 16);
        alen = get_alen(argv[2]);
        if (alen > 3)
                return CMD_RET_USAGE;

        /*
         * Count is always specified
         */
        count = simple_strtoul(argv[3], NULL, 16);

        printf ("CRC32 for %08lx ... %08lx ==> ", addr, addr + count - 1);
        /*
         * CRC a byte at a time.  This is going to be slooow, but hey, the
         * memories are small and slow too so hopefully nobody notices.
         */
        crc = 0;
        err = 0;
        while (count-- > 0) {
                if (i2c_read(chip, addr, alen, &byte, 1) != 0)
                        err++;
                crc = crc32 (crc, &byte, 1);
                addr++;
        }
        if (err > 0)
                puts ("Error reading the chip,\n");
        else
                printf ("%08lx\n", crc);

        return 0;
}

/**
 * mod_i2c_mem() - Handle the "i2c mm" and "i2c nm" command-line command
 * @cmdtp:      Command data struct pointer
 * @flag:       Command flag
 * @argc:       Command-line argument count
 * @argv:       Array of command-line arguments
 *
 * Modify memory.
 *
 * Returns zero on success, CMD_RET_USAGE in case of misuse and negative
 * on error.
 *
 * Syntax:
 *      i2c mm{.b, .w, .l} {i2c_chip} {addr}{.0, .1, .2}
 *      i2c nm{.b, .w, .l} {i2c_chip} {addr}{.0, .1, .2}
 */
static int
mod_i2c_mem(cmd_tbl_t *cmdtp, int incrflag, int flag, int argc, char * const argv[])
{
        uchar   chip;
        ulong   addr;
        uint    alen;
        ulong   data;
        int     size = 1;
        int     nbytes;

        if (argc != 3)
                return CMD_RET_USAGE;

        bootretry_reset_cmd_timeout();  /* got a good command to get here */
        /*
         * We use the last specified parameters, unless new ones are
         * entered.
         */
        chip = i2c_mm_last_chip;
        addr = i2c_mm_last_addr;
        alen = i2c_mm_last_alen;

        if ((flag & CMD_FLAG_REPEAT) == 0) {
                /*
                 * New command specified.  Check for a size specification.
                 * Defaults to byte if no or incorrect specification.
                 */
                size = cmd_get_data_size(argv[0], 1);

                /*
                 * Chip is always specified.
                 */
                chip = simple_strtoul(argv[1], NULL, 16);

                /*
                 * Address is always specified.
                 */
                addr = simple_strtoul(argv[2], NULL, 16);
                alen = get_alen(argv[2]);
                if (alen > 3)
                        return CMD_RET_USAGE;
        }

        /*
         * Print the address, followed by value.  Then accept input for
         * the next value.  A non-converted value exits.
         */
        do {
                printf("%08lx:", addr);
                if (i2c_read(chip, addr, alen, (uchar *)&data, size) != 0)
                        puts ("\nError reading the chip,\n");
                else {
                        data = cpu_to_be32(data);
                        if (size == 1)
                                printf(" %02lx", (data >> 24) & 0x000000FF);
                        else if (size == 2)
                                printf(" %04lx", (data >> 16) & 0x0000FFFF);
                        else
                                printf(" %08lx", data);
                }

                nbytes = cli_readline(" ? ");
                if (nbytes == 0) {
                        /*
                         * <CR> pressed as only input, don't modify current
                         * location and move to next.
                         */
                        if (incrflag)
                                addr += size;
                        nbytes = size;
                        /* good enough to not time out */
                        bootretry_reset_cmd_timeout();
                }
#ifdef CONFIG_BOOT_RETRY_TIME
                else if (nbytes == -2)
                        break;  /* timed out, exit the command  */
#endif
                else {
                        char *endp;

                        data = simple_strtoul(console_buffer, &endp, 16);
                        if (size == 1)
                                data = data << 24;
                        else if (size == 2)
                                data = data << 16;
                        data = be32_to_cpu(data);
                        nbytes = endp - console_buffer;
                        if (nbytes) {
                                /*
                                 * good enough to not time out
                                 */
                                bootretry_reset_cmd_timeout();
                                if (i2c_write(chip, addr, alen, (uchar *)&data, size) != 0)
                                        puts ("Error writing the chip.\n");
#ifdef CONFIG_SYS_EEPROM_PAGE_WRITE_DELAY_MS
                                udelay(CONFIG_SYS_EEPROM_PAGE_WRITE_DELAY_MS * 1000);
#endif
                                if (incrflag)
                                        addr += size;
                        }
                }
        } while (nbytes);

        i2c_mm_last_chip = chip;
        i2c_mm_last_addr = addr;
        i2c_mm_last_alen = alen;

        return 0;
}

/**
 * do_i2c_probe() - Handle the "i2c probe" command-line command
 * @cmdtp:      Command data struct pointer
 * @flag:       Command flag
 * @argc:       Command-line argument count
 * @argv:       Array of command-line arguments
 *
 * Returns zero on success, CMD_RET_USAGE in case of misuse and negative
 * on error.
 *
 * Syntax:
 *      i2c probe {addr}
 *
 * Returns zero (success) if one or more I2C devices was found
 */
static int do_i2c_probe (cmd_tbl_t *cmdtp, int flag, int argc, char * const argv[])
{
        int j;
        int addr = -1;
        int found = 0;
#if defined(CONFIG_SYS_I2C_NOPROBES)
        int k, skip;
        unsigned int bus = GET_BUS_NUM;
#endif  /* NOPROBES */

        if (argc == 2)
                addr = simple_strtol(argv[1], 0, 16);

        puts ("Valid chip addresses:");
        for (j = 0; j < 128; j++) {
                if ((0 <= addr) && (j != addr))
                        continue;

#if defined(CONFIG_SYS_I2C_NOPROBES)
                skip = 0;
                for (k = 0; k < ARRAY_SIZE(i2c_no_probes); k++) {
                        if (COMPARE_BUS(bus, k) && COMPARE_ADDR(j, k)) {
                                skip = 1;
                                break;
                        }
                }
                if (skip)
                        continue;
#endif
                if (i2c_probe(j) == 0) {
                        printf(" %02X", j);
                        found++;
                }
        }
        putc ('\n');

#if defined(CONFIG_SYS_I2C_NOPROBES)
        puts ("Excluded chip addresses:");
        for (k = 0; k < ARRAY_SIZE(i2c_no_probes); k++) {
                if (COMPARE_BUS(bus,k))
                        printf(" %02X", NO_PROBE_ADDR(k));
        }
        putc ('\n');
#endif

        return (0 == found);
}

/**
 * do_i2c_loop() - Handle the "i2c loop" command-line command
 * @cmdtp:      Command data struct pointer
 * @flag:       Command flag
 * @argc:       Command-line argument count
 * @argv:       Array of command-line arguments
 *
 * Returns zero on success, CMD_RET_USAGE in case of misuse and negative
 * on error.
 *
 * Syntax:
 *      i2c loop {i2c_chip} {addr}{.0, .1, .2} [{length}] [{delay}]
 *      {length} - Number of bytes to read
 *      {delay}  - A DECIMAL number and defaults to 1000 uSec
 */
static int do_i2c_loop(cmd_tbl_t *cmdtp, int flag, int argc, char * const argv[])
{
        u_char  chip;
        ulong   alen;
        uint    addr;
        uint    length;
        u_char  bytes[16];
        int     delay;

        if (argc < 3)
                return CMD_RET_USAGE;

        /*
         * Chip is always specified.
         */
        chip = simple_strtoul(argv[1], NULL, 16);

        /*
         * Address is always specified.
         */
        addr = simple_strtoul(argv[2], NULL, 16);
        alen = get_alen(argv[2]);
        if (alen > 3)
                return CMD_RET_USAGE;

        /*
         * Length is the number of objects, not number of bytes.
         */
        length = 1;
        length = simple_strtoul(argv[3], NULL, 16);
        if (length > sizeof(bytes))
                length = sizeof(bytes);

        /*
         * The delay time (uSec) is optional.
         */
        delay = 1000;
        if (argc > 3)
                delay = simple_strtoul(argv[4], NULL, 10);
        /*
         * Run the loop...
         */
        while (1) {
                if (i2c_read(chip, addr, alen, bytes, length) != 0)
                        puts ("Error reading the chip.\n");
                udelay(delay);
        }

        /* NOTREACHED */
        return 0;
}

/*
 * The SDRAM command is separately configured because many
 * (most?) embedded boards don't use SDRAM DIMMs.
 *
 * FIXME: Document and probably move elsewhere!
 */
#if defined(CONFIG_CMD_SDRAM)
static void print_ddr2_tcyc (u_char const b)
{
        printf ("%d.", (b >> 4) & 0x0F);
        switch (b & 0x0F) {
        case 0x0:
        case 0x1:
        case 0x2:
        case 0x3:
        case 0x4:
        case 0x5:
        case 0x6:
        case 0x7:
        case 0x8:
        case 0x9:
                printf ("%d ns\n", b & 0x0F);
                break;
        case 0xA:
                puts ("25 ns\n");
                break;
        case 0xB:
                puts ("33 ns\n");
                break;
        case 0xC:
                puts ("66 ns\n");
                break;
        case 0xD:
                puts ("75 ns\n");
                break;
        default:
                puts ("?? ns\n");
                break;
        }
}

static void decode_bits (u_char const b, char const *str[], int const do_once)
{
        u_char mask;

        for (mask = 0x80; mask != 0x00; mask >>= 1, ++str) {
                if (b & mask) {
                        puts (*str);
                        if (do_once)
                                return;
                }
        }
}

/*
 * Syntax:
 *      i2c sdram {i2c_chip}
 */
static int do_sdram (cmd_tbl_t * cmdtp, int flag, int argc, char * const argv[])
{
        enum { unknown, EDO, SDRAM, DDR2 } type;

        u_char  chip;
        u_char  data[128];
        u_char  cksum;
        int     j;

        static const char *decode_CAS_DDR2[] = {
                " TBD", " 6", " 5", " 4", " 3", " 2", " TBD", " TBD"
        };

        static const char *decode_CAS_default[] = {
                " TBD", " 7", " 6", " 5", " 4", " 3", " 2", " 1"
        };

        static const char *decode_CS_WE_default[] = {
                " TBD", " 6", " 5", " 4", " 3", " 2", " 1", " 0"
        };

        static const char *decode_byte21_default[] = {
                "  TBD (bit 7)\n",
                "  Redundant row address\n",
                "  Differential clock input\n",
                "  Registerd DQMB inputs\n",
                "  Buffered DQMB inputs\n",
                "  On-card PLL\n",
                "  Registered address/control lines\n",
                "  Buffered address/control lines\n"
        };

        static const char *decode_byte22_DDR2[] = {
                "  TBD (bit 7)\n",
                "  TBD (bit 6)\n",
                "  TBD (bit 5)\n",
                "  TBD (bit 4)\n",
                "  TBD (bit 3)\n",
                "  Supports partial array self refresh\n",
                "  Supports 50 ohm ODT\n",
                "  Supports weak driver\n"
        };

        static const char *decode_row_density_DDR2[] = {
                "512 MiB", "256 MiB", "128 MiB", "16 GiB",
                "8 GiB", "4 GiB", "2 GiB", "1 GiB"
        };

        static const char *decode_row_density_default[] = {
                "512 MiB", "256 MiB", "128 MiB", "64 MiB",
                "32 MiB", "16 MiB", "8 MiB", "4 MiB"
        };

        if (argc < 2)
                return CMD_RET_USAGE;

        /*
         * Chip is always specified.
         */
        chip = simple_strtoul (argv[1], NULL, 16);

        if (i2c_read (chip, 0, 1, data, sizeof (data)) != 0) {
                puts ("No SDRAM Serial Presence Detect found.\n");
                return 1;
        }

        cksum = 0;
        for (j = 0; j < 63; j++) {
                cksum += data[j];
        }
        if (cksum != data[63]) {
                printf ("WARNING: Configuration data checksum failure:\n"
                        "  is 0x%02x, calculated 0x%02x\n", data[63], cksum);
        }
        printf ("SPD data revision            %d.%d\n",
                (data[62] >> 4) & 0x0F, data[62] & 0x0F);
        printf ("Bytes used                   0x%02X\n", data[0]);
        printf ("Serial memory size           0x%02X\n", 1 << data[1]);

        puts ("Memory type                  ");
        switch (data[2]) {
        case 2:
                type = EDO;
                puts ("EDO\n");
                break;
        case 4:
                type = SDRAM;
                puts ("SDRAM\n");
                break;
        case 8:
                type = DDR2;
                puts ("DDR2\n");
                break;
        default:
                type = unknown;
                puts ("unknown\n");
                break;
        }

        puts ("Row address bits             ");
        if ((data[3] & 0x00F0) == 0)
                printf ("%d\n", data[3] & 0x0F);
        else
                printf ("%d/%d\n", data[3] & 0x0F, (data[3] >> 4) & 0x0F);

        puts ("Column address bits          ");
        if ((data[4] & 0x00F0) == 0)
                printf ("%d\n", data[4] & 0x0F);
        else
                printf ("%d/%d\n", data[4] & 0x0F, (data[4] >> 4) & 0x0F);

        switch (type) {
        case DDR2:
                printf ("Number of ranks              %d\n",
                        (data[5] & 0x07) + 1);
                break;
        default:
                printf ("Module rows                  %d\n", data[5]);
                break;
        }

        switch (type) {
        case DDR2:
                printf ("Module data width            %d bits\n", data[6]);
                break;
        default:
                printf ("Module data width            %d bits\n",
                        (data[7] << 8) | data[6]);
                break;
        }

        puts ("Interface signal levels      ");
        switch(data[8]) {
                case 0:  puts ("TTL 5.0 V\n");  break;
                case 1:  puts ("LVTTL\n");      break;
                case 2:  puts ("HSTL 1.5 V\n"); break;
                case 3:  puts ("SSTL 3.3 V\n"); break;
                case 4:  puts ("SSTL 2.5 V\n"); break;
                case 5:  puts ("SSTL 1.8 V\n"); break;
                default: puts ("unknown\n");    break;
        }

        switch (type) {
        case DDR2:
                printf ("SDRAM cycle time             ");
                print_ddr2_tcyc (data[9]);
                break;
        default:
                printf ("SDRAM cycle time             %d.%d ns\n",
                        (data[9] >> 4) & 0x0F, data[9] & 0x0F);
                break;
        }

        switch (type) {
        case DDR2:
                printf ("SDRAM access time            0.%d%d ns\n",
                        (data[10] >> 4) & 0x0F, data[10] & 0x0F);
                break;
        default:
                printf ("SDRAM access time            %d.%d ns\n",
                        (data[10] >> 4) & 0x0F, data[10] & 0x0F);
                break;
        }

        puts ("EDC configuration            ");
        switch (data[11]) {
                case 0:  puts ("None\n");       break;
                case 1:  puts ("Parity\n");     break;
                case 2:  puts ("ECC\n");        break;
                default: puts ("unknown\n");    break;
        }

        if ((data[12] & 0x80) == 0)
                puts ("No self refresh, rate        ");
        else
                puts ("Self refresh, rate           ");

        switch(data[12] & 0x7F) {
                case 0:  puts ("15.625 us\n");  break;
                case 1:  puts ("3.9 us\n");     break;
                case 2:  puts ("7.8 us\n");     break;
                case 3:  puts ("31.3 us\n");    break;
                case 4:  puts ("62.5 us\n");    break;
                case 5:  puts ("125 us\n");     break;
                default: puts ("unknown\n");    break;
        }

        switch (type) {
        case DDR2:
                printf ("SDRAM width (primary)        %d\n", data[13]);
                break;
        default:
                printf ("SDRAM width (primary)        %d\n", data[13] & 0x7F);
                if ((data[13] & 0x80) != 0) {
                        printf ("  (second bank)              %d\n",
                                2 * (data[13] & 0x7F));
                }
                break;
        }

        switch (type) {
        case DDR2:
                if (data[14] != 0)
                        printf ("EDC width                    %d\n", data[14]);
                break;
        default:
                if (data[14] != 0) {
                        printf ("EDC width                    %d\n",
                                data[14] & 0x7F);

                        if ((data[14] & 0x80) != 0) {
                                printf ("  (second bank)              %d\n",
                                        2 * (data[14] & 0x7F));
                        }
                }
                break;
        }

        if (DDR2 != type) {
                printf ("Min clock delay, back-to-back random column addresses "
                        "%d\n", data[15]);
        }

        puts ("Burst length(s)             ");
        if (data[16] & 0x80) puts (" Page");
        if (data[16] & 0x08) puts (" 8");
        if (data[16] & 0x04) puts (" 4");
        if (data[16] & 0x02) puts (" 2");
        if (data[16] & 0x01) puts (" 1");
        putc ('\n');
        printf ("Number of banks              %d\n", data[17]);

        switch (type) {
        case DDR2:
                puts ("CAS latency(s)              ");
                decode_bits (data[18], decode_CAS_DDR2, 0);
                putc ('\n');
                break;
        default:
                puts ("CAS latency(s)              ");
                decode_bits (data[18], decode_CAS_default, 0);
                putc ('\n');
                break;
        }

        if (DDR2 != type) {
                puts ("CS latency(s)               ");
                decode_bits (data[19], decode_CS_WE_default, 0);
                putc ('\n');
        }

        if (DDR2 != type) {
                puts ("WE latency(s)               ");
                decode_bits (data[20], decode_CS_WE_default, 0);
                putc ('\n');
        }

        switch (type) {
        case DDR2:
                puts ("Module attributes:\n");
                if (data[21] & 0x80)
                        puts ("  TBD (bit 7)\n");
                if (data[21] & 0x40)
                        puts ("  Analysis probe installed\n");
                if (data[21] & 0x20)
                        puts ("  TBD (bit 5)\n");
                if (data[21] & 0x10)
                        puts ("  FET switch external enable\n");
                printf ("  %d PLLs on DIMM\n", (data[21] >> 2) & 0x03);
                if (data[20] & 0x11) {
                        printf ("  %d active registers on DIMM\n",
                                (data[21] & 0x03) + 1);
                }
                break;
        default:
                puts ("Module attributes:\n");
                if (!data[21])
                        puts ("  (none)\n");
                else
                        decode_bits (data[21], decode_byte21_default, 0);
                break;
        }

        switch (type) {
        case DDR2:
                decode_bits (data[22], decode_byte22_DDR2, 0);
                break;
        default:
                puts ("Device attributes:\n");
                if (data[22] & 0x80) puts ("  TBD (bit 7)\n");
                if (data[22] & 0x40) puts ("  TBD (bit 6)\n");
                if (data[22] & 0x20) puts ("  Upper Vcc tolerance 5%\n");
                else                 puts ("  Upper Vcc tolerance 10%\n");
                if (data[22] & 0x10) puts ("  Lower Vcc tolerance 5%\n");
                else                 puts ("  Lower Vcc tolerance 10%\n");
                if (data[22] & 0x08) puts ("  Supports write1/read burst\n");
                if (data[22] & 0x04) puts ("  Supports precharge all\n");
                if (data[22] & 0x02) puts ("  Supports auto precharge\n");
                if (data[22] & 0x01) puts ("  Supports early RAS# precharge\n");
                break;
        }

        switch (type) {
        case DDR2:
                printf ("SDRAM cycle time (2nd highest CAS latency)        ");
                print_ddr2_tcyc (data[23]);
                break;
        default:
                printf ("SDRAM cycle time (2nd highest CAS latency)        %d."
                        "%d ns\n", (data[23] >> 4) & 0x0F, data[23] & 0x0F);
                break;
        }

        switch (type) {
        case DDR2:
                printf ("SDRAM access from clock (2nd highest CAS latency) 0."
                        "%d%d ns\n", (data[24] >> 4) & 0x0F, data[24] & 0x0F);
                break;
        default:
                printf ("SDRAM access from clock (2nd highest CAS latency) %d."
                        "%d ns\n", (data[24] >> 4) & 0x0F, data[24] & 0x0F);
                break;
        }

        switch (type) {
        case DDR2:
                printf ("SDRAM cycle time (3rd highest CAS latency)        ");
                print_ddr2_tcyc (data[25]);
                break;
        default:
                printf ("SDRAM cycle time (3rd highest CAS latency)        %d."
                        "%d ns\n", (data[25] >> 4) & 0x0F, data[25] & 0x0F);
                break;
        }

        switch (type) {
        case DDR2:
                printf ("SDRAM access from clock (3rd highest CAS latency) 0."
                        "%d%d ns\n", (data[26] >> 4) & 0x0F, data[26] & 0x0F);
                break;
        default:
                printf ("SDRAM access from clock (3rd highest CAS latency) %d."
                        "%d ns\n", (data[26] >> 4) & 0x0F, data[26] & 0x0F);
                break;
        }

        switch (type) {
        case DDR2:
                printf ("Minimum row precharge        %d.%02d ns\n",
                        (data[27] >> 2) & 0x3F, 25 * (data[27] & 0x03));
                break;
        default:
                printf ("Minimum row precharge        %d ns\n", data[27]);
                break;
        }

        switch (type) {
        case DDR2:
                printf ("Row active to row active min %d.%02d ns\n",
                        (data[28] >> 2) & 0x3F, 25 * (data[28] & 0x03));
                break;
        default:
                printf ("Row active to row active min %d ns\n", data[28]);
                break;
        }

        switch (type) {
        case DDR2:
                printf ("RAS to CAS delay min         %d.%02d ns\n",
                        (data[29] >> 2) & 0x3F, 25 * (data[29] & 0x03));
                break;
        default:
                printf ("RAS to CAS delay min         %d ns\n", data[29]);
                break;
        }

        printf ("Minimum RAS pulse width      %d ns\n", data[30]);

        switch (type) {
        case DDR2:
                puts ("Density of each row          ");
                decode_bits (data[31], decode_row_density_DDR2, 1);
                putc ('\n');
                break;
        default:
                puts ("Density of each row          ");
                decode_bits (data[31], decode_row_density_default, 1);
                putc ('\n');
                break;
        }

        switch (type) {
        case DDR2:
                puts ("Command and Address setup    ");
                if (data[32] >= 0xA0) {
                        printf ("1.%d%d ns\n",
                                ((data[32] >> 4) & 0x0F) - 10, data[32] & 0x0F);
                } else {
                        printf ("0.%d%d ns\n",
                                ((data[32] >> 4) & 0x0F), data[32] & 0x0F);
                }
                break;
        default:
                printf ("Command and Address setup    %c%d.%d ns\n",
                        (data[32] & 0x80) ? '-' : '+',
                        (data[32] >> 4) & 0x07, data[32] & 0x0F);
                break;
        }

        switch (type) {
        case DDR2:
                puts ("Command and Address hold     ");
                if (data[33] >= 0xA0) {
                        printf ("1.%d%d ns\n",
                                ((data[33] >> 4) & 0x0F) - 10, data[33] & 0x0F);
                } else {
                        printf ("0.%d%d ns\n",
                                ((data[33] >> 4) & 0x0F), data[33] & 0x0F);
                }
                break;
        default:
                printf ("Command and Address hold     %c%d.%d ns\n",
                        (data[33] & 0x80) ? '-' : '+',
                        (data[33] >> 4) & 0x07, data[33] & 0x0F);
                break;
        }

        switch (type) {
        case DDR2:
                printf ("Data signal input setup      0.%d%d ns\n",
                        (data[34] >> 4) & 0x0F, data[34] & 0x0F);
                break;
        default:
                printf ("Data signal input setup      %c%d.%d ns\n",
                        (data[34] & 0x80) ? '-' : '+',
                        (data[34] >> 4) & 0x07, data[34] & 0x0F);
                break;
        }

        switch (type) {
        case DDR2:
                printf ("Data signal input hold       0.%d%d ns\n",
                        (data[35] >> 4) & 0x0F, data[35] & 0x0F);
                break;
        default:
                printf ("Data signal input hold       %c%d.%d ns\n",
                        (data[35] & 0x80) ? '-' : '+',
                        (data[35] >> 4) & 0x07, data[35] & 0x0F);
                break;
        }

        puts ("Manufacturer's JEDEC ID      ");
        for (j = 64; j <= 71; j++)
                printf ("%02X ", data[j]);
        putc ('\n');
        printf ("Manufacturing Location       %02X\n", data[72]);
        puts ("Manufacturer's Part Number   ");
        for (j = 73; j <= 90; j++)
                printf ("%02X ", data[j]);
        putc ('\n');
        printf ("Revision Code                %02X %02X\n", data[91], data[92]);
        printf ("Manufacturing Date           %02X %02X\n", data[93], data[94]);
        puts ("Assembly Serial Number       ");
        for (j = 95; j <= 98; j++)
                printf ("%02X ", data[j]);
        putc ('\n');

        if (DDR2 != type) {
                printf ("Speed rating                 PC%d\n",
                        data[126] == 0x66 ? 66 : data[126]);
        }
        return 0;
}
#endif

/*
 * Syntax:
 *      i2c edid {i2c_chip}
 */
#if defined(CONFIG_I2C_EDID)
int do_edid(cmd_tbl_t *cmdtp, int flag, int argc, char *const argv[])
{
        u_char chip;
        struct edid1_info edid;

        if (argc < 2) {
                cmd_usage(cmdtp);
                return 1;
        }

        chip = simple_strtoul(argv[1], NULL, 16);
        if (i2c_read(chip, 0, 1, (uchar *)&edid, sizeof(edid)) != 0) {
                puts("Error reading EDID content.\n");
                return 1;
        }

        if (edid_check_info(&edid)) {
                puts("Content isn't valid EDID.\n");
                return 1;
        }

        edid_print_info(&edid);
        return 0;

}
#endif /* CONFIG_I2C_EDID */

/**
 * do_i2c_show_bus() - Handle the "i2c bus" command-line command
 * @cmdtp:      Command data struct pointer
 * @flag:       Command flag
 * @argc:       Command-line argument count
 * @argv:       Array of command-line arguments
 *
 * Returns zero always.
 */
#if defined(CONFIG_SYS_I2C)
int do_i2c_show_bus(cmd_tbl_t *cmdtp, int flag, int argc, char * const argv[])
{
        int     i;
#ifndef CONFIG_SYS_I2C_DIRECT_BUS
        int     j;
#endif

        if (argc == 1) {
                /* show all busses */
                for (i = 0; i < CONFIG_SYS_NUM_I2C_BUSES; i++) {
                        printf("Bus %d:\t%s", i, I2C_ADAP_NR(i)->name);
#ifndef CONFIG_SYS_I2C_DIRECT_BUS
                        for (j = 0; j < CONFIG_SYS_I2C_MAX_HOPS; j++) {
                                if (i2c_bus[i].next_hop[j].chip == 0)
                                        break;
                                printf("->%s@0x%2x:%d",
                                       i2c_bus[i].next_hop[j].mux.name,
                                       i2c_bus[i].next_hop[j].chip,
                                       i2c_bus[i].next_hop[j].channel);
                        }
#endif
                        printf("\n");
                }
        } else {
                /* show specific bus */
                i = simple_strtoul(argv[1], NULL, 10);
                if (i >= CONFIG_SYS_NUM_I2C_BUSES) {
                        printf("Invalid bus %d\n", i);
                        return -1;
                }
                printf("Bus %d:\t%s", i, I2C_ADAP_NR(i)->name);
#ifndef CONFIG_SYS_I2C_DIRECT_BUS
                        for (j = 0; j < CONFIG_SYS_I2C_MAX_HOPS; j++) {
                                if (i2c_bus[i].next_hop[j].chip == 0)
                                        break;
                                printf("->%s@0x%2x:%d",
                                       i2c_bus[i].next_hop[j].mux.name,
                                       i2c_bus[i].next_hop[j].chip,
                                       i2c_bus[i].next_hop[j].channel);
                        }
#endif
                printf("\n");
        }

        return 0;
}
#endif

/**
 * do_i2c_bus_num() - Handle the "i2c dev" command-line command
 * @cmdtp:      Command data struct pointer
 * @flag:       Command flag
 * @argc:       Command-line argument count
 * @argv:       Array of command-line arguments
 *
 * Returns zero on success, CMD_RET_USAGE in case of misuse and negative
 * on error.
 */
#if defined(CONFIG_SYS_I2C) || defined(CONFIG_I2C_MULTI_BUS)
int do_i2c_bus_num(cmd_tbl_t *cmdtp, int flag, int argc, char * const argv[])
{
        int             ret = 0;
        unsigned int    bus_no;

        if (argc == 1)
                /* querying current setting */
                printf("Current bus is %d\n", i2c_get_bus_num());
        else {
                bus_no = simple_strtoul(argv[1], NULL, 10);
#if defined(CONFIG_SYS_I2C)
                if (bus_no >= CONFIG_SYS_NUM_I2C_BUSES) {
                        printf("Invalid bus %d\n", bus_no);
                        return -1;
                }
#endif
                printf("Setting bus to %d\n", bus_no);
                ret = i2c_set_bus_num(bus_no);
                if (ret)
                        printf("Failure changing bus number (%d)\n", ret);
        }
        return ret;
}
#endif  /* defined(CONFIG_SYS_I2C) */

/**
 * do_i2c_bus_speed() - Handle the "i2c speed" command-line command
 * @cmdtp:      Command data struct pointer
 * @flag:       Command flag
 * @argc:       Command-line argument count
 * @argv:       Array of command-line arguments
 *
 * Returns zero on success, CMD_RET_USAGE in case of misuse and negative
 * on error.
 */
static int do_i2c_bus_speed(cmd_tbl_t * cmdtp, int flag, int argc, char * const argv[])
{
        int speed, ret=0;

        if (argc == 1)
                /* querying current speed */
                printf("Current bus speed=%d\n", i2c_get_bus_speed());
        else {
                speed = simple_strtoul(argv[1], NULL, 10);
                printf("Setting bus speed to %d Hz\n", speed);
                ret = i2c_set_bus_speed(speed);
                if (ret)
                        printf("Failure changing bus speed (%d)\n", ret);
        }
        return ret;
}

/**
 * do_i2c_mm() - Handle the "i2c mm" command-line command
 * @cmdtp:      Command data struct pointer
 * @flag:       Command flag
 * @argc:       Command-line argument count
 * @argv:       Array of command-line arguments
 *
 * Returns zero on success, CMD_RET_USAGE in case of misuse and negative
 * on error.
 */
static int do_i2c_mm(cmd_tbl_t * cmdtp, int flag, int argc, char * const argv[])
{
        return mod_i2c_mem (cmdtp, 1, flag, argc, argv);
}

/**
 * do_i2c_nm() - Handle the "i2c nm" command-line command
 * @cmdtp:      Command data struct pointer
 * @flag:       Command flag
 * @argc:       Command-line argument count
 * @argv:       Array of command-line arguments
 *
 * Returns zero on success, CMD_RET_USAGE in case of misuse and negative
 * on error.
 */
static int do_i2c_nm(cmd_tbl_t * cmdtp, int flag, int argc, char * const argv[])
{
        return mod_i2c_mem (cmdtp, 0, flag, argc, argv);
}

/**
 * do_i2c_reset() - Handle the "i2c reset" command-line command
 * @cmdtp:      Command data struct pointer
 * @flag:       Command flag
 * @argc:       Command-line argument count
 * @argv:       Array of command-line arguments
 *
 * Returns zero always.
 */
static int do_i2c_reset(cmd_tbl_t * cmdtp, int flag, int argc, char * const argv[])
{
#if defined(CONFIG_SYS_I2C)
        i2c_init(I2C_ADAP->speed, I2C_ADAP->slaveaddr);
#else
        i2c_init(CONFIG_SYS_I2C_SPEED, CONFIG_SYS_I2C_SLAVE);
#endif
        return 0;
}

static cmd_tbl_t cmd_i2c_sub[] = {
#if defined(CONFIG_SYS_I2C)
        U_BOOT_CMD_MKENT(bus, 1, 1, do_i2c_show_bus, "", ""),
#endif
        U_BOOT_CMD_MKENT(crc32, 3, 1, do_i2c_crc, "", ""),
#if defined(CONFIG_SYS_I2C) || \
        defined(CONFIG_I2C_MULTI_BUS)
        U_BOOT_CMD_MKENT(dev, 1, 1, do_i2c_bus_num, "", ""),
#endif  /* CONFIG_I2C_MULTI_BUS */
#if defined(CONFIG_I2C_EDID)
        U_BOOT_CMD_MKENT(edid, 1, 1, do_edid, "", ""),
#endif  /* CONFIG_I2C_EDID */
        U_BOOT_CMD_MKENT(loop, 3, 1, do_i2c_loop, "", ""),
        U_BOOT_CMD_MKENT(md, 3, 1, do_i2c_md, "", ""),
        U_BOOT_CMD_MKENT(mm, 2, 1, do_i2c_mm, "", ""),
        U_BOOT_CMD_MKENT(mw, 3, 1, do_i2c_mw, "", ""),
        U_BOOT_CMD_MKENT(nm, 2, 1, do_i2c_nm, "", ""),
        U_BOOT_CMD_MKENT(probe, 0, 1, do_i2c_probe, "", ""),
        U_BOOT_CMD_MKENT(read, 5, 1, do_i2c_read, "", ""),
        U_BOOT_CMD_MKENT(write, 5, 0, do_i2c_write, "", ""),
        U_BOOT_CMD_MKENT(reset, 0, 1, do_i2c_reset, "", ""),
#if defined(CONFIG_CMD_SDRAM)
        U_BOOT_CMD_MKENT(sdram, 1, 1, do_sdram, "", ""),
#endif
        U_BOOT_CMD_MKENT(speed, 1, 1, do_i2c_bus_speed, "", ""),
};

#ifdef CONFIG_NEEDS_MANUAL_RELOC
void i2c_reloc(void) {
        fixup_cmdtable(cmd_i2c_sub, ARRAY_SIZE(cmd_i2c_sub));
}
#endif

/**
 * do_i2c() - Handle the "i2c" command-line command
 * @cmdtp:      Command data struct pointer
 * @flag:       Command flag
 * @argc:       Command-line argument count
 * @argv:       Array of command-line arguments
 *
 * Returns zero on success, CMD_RET_USAGE in case of misuse and negative
 * on error.
 */
static int do_i2c(cmd_tbl_t * cmdtp, int flag, int argc, char * const argv[])
{
        cmd_tbl_t *c;

        if (argc < 2)
                return CMD_RET_USAGE;

        /* Strip off leading 'i2c' command argument */
        argc--;
        argv++;

        c = find_cmd_tbl(argv[0], &cmd_i2c_sub[0], ARRAY_SIZE(cmd_i2c_sub));

        if (c)
                return c->cmd(cmdtp, flag, argc, argv);
        else
                return CMD_RET_USAGE;
}

/***************************************************/
#ifdef CONFIG_SYS_LONGHELP
static char i2c_help_text[] =
#if defined(CONFIG_SYS_I2C)
        "bus [muxtype:muxaddr:muxchannel] - show I2C bus info\n"
#endif
        "crc32 chip address[.0, .1, .2] count - compute CRC32 checksum\n"
#if defined(CONFIG_SYS_I2C) || \
        defined(CONFIG_I2C_MULTI_BUS)
        "i2c dev [dev] - show or set current I2C bus\n"
#endif  /* CONFIG_I2C_MULTI_BUS */
#if defined(CONFIG_I2C_EDID)
        "i2c edid chip - print EDID configuration information\n"
#endif  /* CONFIG_I2C_EDID */
        "i2c loop chip address[.0, .1, .2] [# of objects] - looping read of device\n"
        "i2c md chip address[.0, .1, .2] [# of objects] - read from I2C device\n"
        "i2c mm chip address[.0, .1, .2] - write to I2C device (auto-incrementing)\n"
        "i2c mw chip address[.0, .1, .2] value [count] - write to I2C device (fill)\n"
        "i2c nm chip address[.0, .1, .2] - write to I2C device (constant address)\n"
        "i2c probe [address] - test for and show device(s) on the I2C bus\n"
        "i2c read chip address[.0, .1, .2] length memaddress - read to memory \n"
        "i2c write memaddress chip address[.0, .1, .2] length - write memory to i2c\n"
        "i2c reset - re-init the I2C Controller\n"
#if defined(CONFIG_CMD_SDRAM)
        "i2c sdram chip - print SDRAM configuration information\n"
#endif
        "i2c speed [speed] - show or set I2C bus speed";
#endif

U_BOOT_CMD(
        i2c, 6, 1, do_i2c,
        "I2C sub-system",
        i2c_help_text
);