drivers/mtd/nand/nand_ecc.c

   1 /*
   2  * This file contains an ECC algorithm from Toshiba that detects and
   3  * corrects 1 bit errors in a 256 byte block of data.
   4  *
   5  * drivers/mtd/nand/nand_ecc.c
   6  *
   7  * Copyright (C) 2000-2004 Steven J. Hill (sjhill@realitydiluted.com)
   8  *                         Toshiba America Electronics Components, Inc.
   9  *
  10  * Copyright (C) 2006 Thomas Gleixner <tglx@linutronix.de>
  11  *
  12  * SPDX-License-Identifier:     GPL-2.0+
  13  *
  14  * As a special exception, if other files instantiate templates or use
  15  * macros or inline functions from these files, or you compile these
  16  * files and link them with other works to produce a work based on these
  17  * files, these files do not by themselves cause the resulting work to be
  18  * covered by the GNU General Public License. However the source code for
  19  * these files must still be made available in accordance with section (3)
  20  * of the GNU General Public License.
  21  *
  22  * This exception does not invalidate any other reasons why a work based on
  23  * this file might be covered by the GNU General Public License.
  24  */
  25
  26 #include <common.h>
  27
  28 #include <asm/errno.h>
  29 #include <linux/mtd/mtd.h>
  30 #include <linux/mtd/nand_ecc.h>
  31
  32 /* The PPC4xx NDFC uses Smart Media (SMC) bytes order */
  33 #ifdef CONFIG_NAND_NDFC
  34 #define CONFIG_MTD_NAND_ECC_SMC
  35 #endif
  36
  37 /*
  38  * NAND-SPL has no sofware ECC for now, so don't include nand_calculate_ecc(),
  39  * only nand_correct_data() is needed
  40  */
  41
  42 #if !defined(CONFIG_NAND_SPL) || defined(CONFIG_SPL_NAND_SOFTECC)
  43 /*
  44  * Pre-calculated 256-way 1 byte column parity
  45  */
  46 static const u_char nand_ecc_precalc_table[] = {
  47         0x00, 0x55, 0x56, 0x03, 0x59, 0x0c, 0x0f, 0x5a, 0x5a, 0x0f, 0x0c, 0x59, 0x03, 0x56, 0x55, 0x00,
  48         0x65, 0x30, 0x33, 0x66, 0x3c, 0x69, 0x6a, 0x3f, 0x3f, 0x6a, 0x69, 0x3c, 0x66, 0x33, 0x30, 0x65,
  49         0x66, 0x33, 0x30, 0x65, 0x3f, 0x6a, 0x69, 0x3c, 0x3c, 0x69, 0x6a, 0x3f, 0x65, 0x30, 0x33, 0x66,
  50         0x03, 0x56, 0x55, 0x00, 0x5a, 0x0f, 0x0c, 0x59, 0x59, 0x0c, 0x0f, 0x5a, 0x00, 0x55, 0x56, 0x03,
  51         0x69, 0x3c, 0x3f, 0x6a, 0x30, 0x65, 0x66, 0x33, 0x33, 0x66, 0x65, 0x30, 0x6a, 0x3f, 0x3c, 0x69,
  52         0x0c, 0x59, 0x5a, 0x0f, 0x55, 0x00, 0x03, 0x56, 0x56, 0x03, 0x00, 0x55, 0x0f, 0x5a, 0x59, 0x0c,
  53         0x0f, 0x5a, 0x59, 0x0c, 0x56, 0x03, 0x00, 0x55, 0x55, 0x00, 0x03, 0x56, 0x0c, 0x59, 0x5a, 0x0f,
  54         0x6a, 0x3f, 0x3c, 0x69, 0x33, 0x66, 0x65, 0x30, 0x30, 0x65, 0x66, 0x33, 0x69, 0x3c, 0x3f, 0x6a,
  55         0x6a, 0x3f, 0x3c, 0x69, 0x33, 0x66, 0x65, 0x30, 0x30, 0x65, 0x66, 0x33, 0x69, 0x3c, 0x3f, 0x6a,
  56         0x0f, 0x5a, 0x59, 0x0c, 0x56, 0x03, 0x00, 0x55, 0x55, 0x00, 0x03, 0x56, 0x0c, 0x59, 0x5a, 0x0f,
  57         0x0c, 0x59, 0x5a, 0x0f, 0x55, 0x00, 0x03, 0x56, 0x56, 0x03, 0x00, 0x55, 0x0f, 0x5a, 0x59, 0x0c,
  58         0x69, 0x3c, 0x3f, 0x6a, 0x30, 0x65, 0x66, 0x33, 0x33, 0x66, 0x65, 0x30, 0x6a, 0x3f, 0x3c, 0x69,
  59         0x03, 0x56, 0x55, 0x00, 0x5a, 0x0f, 0x0c, 0x59, 0x59, 0x0c, 0x0f, 0x5a, 0x00, 0x55, 0x56, 0x03,
  60         0x66, 0x33, 0x30, 0x65, 0x3f, 0x6a, 0x69, 0x3c, 0x3c, 0x69, 0x6a, 0x3f, 0x65, 0x30, 0x33, 0x66,
  61         0x65, 0x30, 0x33, 0x66, 0x3c, 0x69, 0x6a, 0x3f, 0x3f, 0x6a, 0x69, 0x3c, 0x66, 0x33, 0x30, 0x65,
  62         0x00, 0x55, 0x56, 0x03, 0x59, 0x0c, 0x0f, 0x5a, 0x5a, 0x0f, 0x0c, 0x59, 0x03, 0x56, 0x55, 0x00
  63 };
  64
  65 /**
  66  * nand_calculate_ecc - [NAND Interface] Calculate 3-byte ECC for 256-byte block
  67  * @mtd:        MTD block structure
  68  * @dat:        raw data
  69  * @ecc_code:   buffer for ECC
  70  */
  71 int nand_calculate_ecc(struct mtd_info *mtd, const u_char *dat,
  72                        u_char *ecc_code)
  73 {
  74         uint8_t idx, reg1, reg2, reg3, tmp1, tmp2;
  75         int i;
  76
  77         /* Initialize variables */
  78         reg1 = reg2 = reg3 = 0;
  79
  80         /* Build up column parity */
  81         for(i = 0; i < 256; i++) {
  82                 /* Get CP0 - CP5 from table */
  83                 idx = nand_ecc_precalc_table[*dat++];
  84                 reg1 ^= (idx & 0x3f);
  85
  86                 /* All bit XOR = 1 ? */
  87                 if (idx & 0x40) {
  88                         reg3 ^= (uint8_t) i;
  89                         reg2 ^= ~((uint8_t) i);
  90                 }
  91         }
  92
  93         /* Create non-inverted ECC code from line parity */
  94         tmp1  = (reg3 & 0x80) >> 0; /* B7 -> B7 */
  95         tmp1 |= (reg2 & 0x80) >> 1; /* B7 -> B6 */
  96         tmp1 |= (reg3 & 0x40) >> 1; /* B6 -> B5 */
  97         tmp1 |= (reg2 & 0x40) >> 2; /* B6 -> B4 */
  98         tmp1 |= (reg3 & 0x20) >> 2; /* B5 -> B3 */
  99         tmp1 |= (reg2 & 0x20) >> 3; /* B5 -> B2 */
 100         tmp1 |= (reg3 & 0x10) >> 3; /* B4 -> B1 */
 101         tmp1 |= (reg2 & 0x10) >> 4; /* B4 -> B0 */
 102
 103         tmp2  = (reg3 & 0x08) << 4; /* B3 -> B7 */
 104         tmp2 |= (reg2 & 0x08) << 3; /* B3 -> B6 */
 105         tmp2 |= (reg3 & 0x04) << 3; /* B2 -> B5 */
 106         tmp2 |= (reg2 & 0x04) << 2; /* B2 -> B4 */
 107         tmp2 |= (reg3 & 0x02) << 2; /* B1 -> B3 */
 108         tmp2 |= (reg2 & 0x02) << 1; /* B1 -> B2 */
 109         tmp2 |= (reg3 & 0x01) << 1; /* B0 -> B1 */
 110         tmp2 |= (reg2 & 0x01) << 0; /* B7 -> B0 */
 111
 112         /* Calculate final ECC code */
 113 #ifdef CONFIG_MTD_NAND_ECC_SMC
 114         ecc_code[0] = ~tmp2;
 115         ecc_code[1] = ~tmp1;
 116 #else
 117         ecc_code[0] = ~tmp1;
 118         ecc_code[1] = ~tmp2;
 119 #endif
 120         ecc_code[2] = ((~reg1) << 2) | 0x03;
 121
 122         return 0;
 123 }
 124 #endif /* CONFIG_NAND_SPL */
 125
 126 static inline int countbits(uint32_t byte)
 127 {
 128         int res = 0;
 129
 130         for (;byte; byte >>= 1)
 131                 res += byte & 0x01;
 132         return res;
 133 }
 134
 135 /**
 136  * nand_correct_data - [NAND Interface] Detect and correct bit error(s)
 137  * @mtd:        MTD block structure
 138  * @dat:        raw data read from the chip
 139  * @read_ecc:   ECC from the chip
 140  * @calc_ecc:   the ECC calculated from raw data
 141  *
 142  * Detect and correct a 1 bit error for 256 byte block
 143  */
 144 int nand_correct_data(struct mtd_info *mtd, u_char *dat,
 145                       u_char *read_ecc, u_char *calc_ecc)
 146 {
 147         uint8_t s0, s1, s2;
 148
 149 #ifdef CONFIG_MTD_NAND_ECC_SMC
 150         s0 = calc_ecc[0] ^ read_ecc[0];
 151         s1 = calc_ecc[1] ^ read_ecc[1];
 152         s2 = calc_ecc[2] ^ read_ecc[2];
 153 #else
 154         s1 = calc_ecc[0] ^ read_ecc[0];
 155         s0 = calc_ecc[1] ^ read_ecc[1];
 156         s2 = calc_ecc[2] ^ read_ecc[2];
 157 #endif
 158         if ((s0 | s1 | s2) == 0)
 159                 return 0;
 160
 161         /* Check for a single bit error */
 162         if( ((s0 ^ (s0 >> 1)) & 0x55) == 0x55 &&
 163             ((s1 ^ (s1 >> 1)) & 0x55) == 0x55 &&
 164             ((s2 ^ (s2 >> 1)) & 0x54) == 0x54) {
 165
 166                 uint32_t byteoffs, bitnum;
 167
 168                 byteoffs = (s1 << 0) & 0x80;
 169                 byteoffs |= (s1 << 1) & 0x40;
 170                 byteoffs |= (s1 << 2) & 0x20;
 171                 byteoffs |= (s1 << 3) & 0x10;
 172
 173                 byteoffs |= (s0 >> 4) & 0x08;
 174                 byteoffs |= (s0 >> 3) & 0x04;
 175                 byteoffs |= (s0 >> 2) & 0x02;
 176                 byteoffs |= (s0 >> 1) & 0x01;
 177
 178                 bitnum = (s2 >> 5) & 0x04;
 179                 bitnum |= (s2 >> 4) & 0x02;
 180                 bitnum |= (s2 >> 3) & 0x01;
 181
 182                 dat[byteoffs] ^= (1 << bitnum);
 183
 184                 return 1;
 185         }
 186
 187         if(countbits(s0 | ((uint32_t)s1 << 8) | ((uint32_t)s2 <<16)) == 1)
 188                 return 1;
 189
 190         return -EBADMSG;
 191 }