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  * This file is free software; you can redistribute it and/or modify it
  13  * under the terms of the GNU General Public License as published by the
  14  * Free Software Foundation; either version 2 or (at your option) any
  15  * later version.
  16  *
  17  * This file is distributed in the hope that it will be useful, but WITHOUT
  18  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
  19  * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
  20  * for more details.
  21  *
  22  * You should have received a copy of the GNU General Public License along
  23  * with this file; if not, write to the Free Software Foundation, Inc.,
  24  * 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA.
  25  *
  26  * As a special exception, if other files instantiate templates or use
  27  * macros or inline functions from these files, or you compile these
  28  * files and link them with other works to produce a work based on these
  29  * files, these files do not by themselves cause the resulting work to be
  30  * covered by the GNU General Public License. However the source code for
  31  * these files must still be made available in accordance with section (3)
  32  * of the GNU General Public License.
  33  *
  34  * This exception does not invalidate any other reasons why a work based on
  35  * this file might be covered by the GNU General Public License.
  36  */
  37
  38 #include <common.h>
  39
  40 #include <asm/errno.h>
  41 #include <linux/mtd/mtd.h>
  42 #include <linux/mtd/nand_ecc.h>
  43
  44 /* The PPC4xx NDFC uses Smart Media (SMC) bytes order */
  45 #ifdef CONFIG_NAND_NDFC
  46 #define CONFIG_MTD_NAND_ECC_SMC
  47 #endif
  48
  49 /*
  50  * NAND-SPL has no sofware ECC for now, so don't include nand_calculate_ecc(),
  51  * only nand_correct_data() is needed
  52  */
  53
  54 #if !defined(CONFIG_NAND_SPL) || defined(CONFIG_SPL_NAND_SOFTECC)
  55 /*
  56  * Pre-calculated 256-way 1 byte column parity
  57  */
  58 static const u_char nand_ecc_precalc_table[] = {
  59         0x00, 0x55, 0x56, 0x03, 0x59, 0x0c, 0x0f, 0x5a, 0x5a, 0x0f, 0x0c, 0x59, 0x03, 0x56, 0x55, 0x00,
  60         0x65, 0x30, 0x33, 0x66, 0x3c, 0x69, 0x6a, 0x3f, 0x3f, 0x6a, 0x69, 0x3c, 0x66, 0x33, 0x30, 0x65,
  61         0x66, 0x33, 0x30, 0x65, 0x3f, 0x6a, 0x69, 0x3c, 0x3c, 0x69, 0x6a, 0x3f, 0x65, 0x30, 0x33, 0x66,
  62         0x03, 0x56, 0x55, 0x00, 0x5a, 0x0f, 0x0c, 0x59, 0x59, 0x0c, 0x0f, 0x5a, 0x00, 0x55, 0x56, 0x03,
  63         0x69, 0x3c, 0x3f, 0x6a, 0x30, 0x65, 0x66, 0x33, 0x33, 0x66, 0x65, 0x30, 0x6a, 0x3f, 0x3c, 0x69,
  64         0x0c, 0x59, 0x5a, 0x0f, 0x55, 0x00, 0x03, 0x56, 0x56, 0x03, 0x00, 0x55, 0x0f, 0x5a, 0x59, 0x0c,
  65         0x0f, 0x5a, 0x59, 0x0c, 0x56, 0x03, 0x00, 0x55, 0x55, 0x00, 0x03, 0x56, 0x0c, 0x59, 0x5a, 0x0f,
  66         0x6a, 0x3f, 0x3c, 0x69, 0x33, 0x66, 0x65, 0x30, 0x30, 0x65, 0x66, 0x33, 0x69, 0x3c, 0x3f, 0x6a,
  67         0x6a, 0x3f, 0x3c, 0x69, 0x33, 0x66, 0x65, 0x30, 0x30, 0x65, 0x66, 0x33, 0x69, 0x3c, 0x3f, 0x6a,
  68         0x0f, 0x5a, 0x59, 0x0c, 0x56, 0x03, 0x00, 0x55, 0x55, 0x00, 0x03, 0x56, 0x0c, 0x59, 0x5a, 0x0f,
  69         0x0c, 0x59, 0x5a, 0x0f, 0x55, 0x00, 0x03, 0x56, 0x56, 0x03, 0x00, 0x55, 0x0f, 0x5a, 0x59, 0x0c,
  70         0x69, 0x3c, 0x3f, 0x6a, 0x30, 0x65, 0x66, 0x33, 0x33, 0x66, 0x65, 0x30, 0x6a, 0x3f, 0x3c, 0x69,
  71         0x03, 0x56, 0x55, 0x00, 0x5a, 0x0f, 0x0c, 0x59, 0x59, 0x0c, 0x0f, 0x5a, 0x00, 0x55, 0x56, 0x03,
  72         0x66, 0x33, 0x30, 0x65, 0x3f, 0x6a, 0x69, 0x3c, 0x3c, 0x69, 0x6a, 0x3f, 0x65, 0x30, 0x33, 0x66,
  73         0x65, 0x30, 0x33, 0x66, 0x3c, 0x69, 0x6a, 0x3f, 0x3f, 0x6a, 0x69, 0x3c, 0x66, 0x33, 0x30, 0x65,
  74         0x00, 0x55, 0x56, 0x03, 0x59, 0x0c, 0x0f, 0x5a, 0x5a, 0x0f, 0x0c, 0x59, 0x03, 0x56, 0x55, 0x00
  75 };
  76
  77 /**
  78  * nand_calculate_ecc - [NAND Interface] Calculate 3-byte ECC for 256-byte block
  79  * @mtd:        MTD block structure
  80  * @dat:        raw data
  81  * @ecc_code:   buffer for ECC
  82  */
  83 int nand_calculate_ecc(struct mtd_info *mtd, const u_char *dat,
  84                        u_char *ecc_code)
  85 {
  86         uint8_t idx, reg1, reg2, reg3, tmp1, tmp2;
  87         int i;
  88
  89         /* Initialize variables */
  90         reg1 = reg2 = reg3 = 0;
  91
  92         /* Build up column parity */
  93         for(i = 0; i < 256; i++) {
  94                 /* Get CP0 - CP5 from table */
  95                 idx = nand_ecc_precalc_table[*dat++];
  96                 reg1 ^= (idx & 0x3f);
  97
  98                 /* All bit XOR = 1 ? */
  99                 if (idx & 0x40) {
 100                         reg3 ^= (uint8_t) i;
 101                         reg2 ^= ~((uint8_t) i);
 102                 }
 103         }
 104
 105         /* Create non-inverted ECC code from line parity */
 106         tmp1  = (reg3 & 0x80) >> 0; /* B7 -> B7 */
 107         tmp1 |= (reg2 & 0x80) >> 1; /* B7 -> B6 */
 108         tmp1 |= (reg3 & 0x40) >> 1; /* B6 -> B5 */
 109         tmp1 |= (reg2 & 0x40) >> 2; /* B6 -> B4 */
 110         tmp1 |= (reg3 & 0x20) >> 2; /* B5 -> B3 */
 111         tmp1 |= (reg2 & 0x20) >> 3; /* B5 -> B2 */
 112         tmp1 |= (reg3 & 0x10) >> 3; /* B4 -> B1 */
 113         tmp1 |= (reg2 & 0x10) >> 4; /* B4 -> B0 */
 114
 115         tmp2  = (reg3 & 0x08) << 4; /* B3 -> B7 */
 116         tmp2 |= (reg2 & 0x08) << 3; /* B3 -> B6 */
 117         tmp2 |= (reg3 & 0x04) << 3; /* B2 -> B5 */
 118         tmp2 |= (reg2 & 0x04) << 2; /* B2 -> B4 */
 119         tmp2 |= (reg3 & 0x02) << 2; /* B1 -> B3 */
 120         tmp2 |= (reg2 & 0x02) << 1; /* B1 -> B2 */
 121         tmp2 |= (reg3 & 0x01) << 1; /* B0 -> B1 */
 122         tmp2 |= (reg2 & 0x01) << 0; /* B7 -> B0 */
 123
 124         /* Calculate final ECC code */
 125 #ifdef CONFIG_MTD_NAND_ECC_SMC
 126         ecc_code[0] = ~tmp2;
 127         ecc_code[1] = ~tmp1;
 128 #else
 129         ecc_code[0] = ~tmp1;
 130         ecc_code[1] = ~tmp2;
 131 #endif
 132         ecc_code[2] = ((~reg1) << 2) | 0x03;
 133
 134         return 0;
 135 }
 136 #endif /* CONFIG_NAND_SPL */
 137
 138 static inline int countbits(uint32_t byte)
 139 {
 140         int res = 0;
 141
 142         for (;byte; byte >>= 1)
 143                 res += byte & 0x01;
 144         return res;
 145 }
 146
 147 /**
 148  * nand_correct_data - [NAND Interface] Detect and correct bit error(s)
 149  * @mtd:        MTD block structure
 150  * @dat:        raw data read from the chip
 151  * @read_ecc:   ECC from the chip
 152  * @calc_ecc:   the ECC calculated from raw data
 153  *
 154  * Detect and correct a 1 bit error for 256 byte block
 155  */
 156 int nand_correct_data(struct mtd_info *mtd, u_char *dat,
 157                       u_char *read_ecc, u_char *calc_ecc)
 158 {
 159         uint8_t s0, s1, s2;
 160
 161 #ifdef CONFIG_MTD_NAND_ECC_SMC
 162         s0 = calc_ecc[0] ^ read_ecc[0];
 163         s1 = calc_ecc[1] ^ read_ecc[1];
 164         s2 = calc_ecc[2] ^ read_ecc[2];
 165 #else
 166         s1 = calc_ecc[0] ^ read_ecc[0];
 167         s0 = calc_ecc[1] ^ read_ecc[1];
 168         s2 = calc_ecc[2] ^ read_ecc[2];
 169 #endif
 170         if ((s0 | s1 | s2) == 0)
 171                 return 0;
 172
 173         /* Check for a single bit error */
 174         if( ((s0 ^ (s0 >> 1)) & 0x55) == 0x55 &&
 175             ((s1 ^ (s1 >> 1)) & 0x55) == 0x55 &&
 176             ((s2 ^ (s2 >> 1)) & 0x54) == 0x54) {
 177
 178                 uint32_t byteoffs, bitnum;
 179
 180                 byteoffs = (s1 << 0) & 0x80;
 181                 byteoffs |= (s1 << 1) & 0x40;
 182                 byteoffs |= (s1 << 2) & 0x20;
 183                 byteoffs |= (s1 << 3) & 0x10;
 184
 185                 byteoffs |= (s0 >> 4) & 0x08;
 186                 byteoffs |= (s0 >> 3) & 0x04;
 187                 byteoffs |= (s0 >> 2) & 0x02;
 188                 byteoffs |= (s0 >> 1) & 0x01;
 189
 190                 bitnum = (s2 >> 5) & 0x04;
 191                 bitnum |= (s2 >> 4) & 0x02;
 192                 bitnum |= (s2 >> 3) & 0x01;
 193
 194                 dat[byteoffs] ^= (1 << bitnum);
 195
 196                 return 1;
 197         }
 198
 199         if(countbits(s0 | ((uint32_t)s1 << 8) | ((uint32_t)s2 <<16)) == 1)
 200                 return 1;
 201
 202         return -EBADMSG;
 203 }