drivers/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  * $Id: nand_ecc.c,v 1.14 2004/06/16 15:34:37 gleixner Exp $
  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 #if (CONFIG_COMMANDS & CFG_CMD_NAND)
  41
  42 /*
  43  * Pre-calculated 256-way 1 byte column parity
  44  */
  45 static const u_char nand_ecc_precalc_table[] = {
  46         0x00, 0x55, 0x56, 0x03, 0x59, 0x0c, 0x0f, 0x5a, 0x5a, 0x0f, 0x0c, 0x59, 0x03, 0x56, 0x55, 0x00,
  47         0x65, 0x30, 0x33, 0x66, 0x3c, 0x69, 0x6a, 0x3f, 0x3f, 0x6a, 0x69, 0x3c, 0x66, 0x33, 0x30, 0x65,
  48         0x66, 0x33, 0x30, 0x65, 0x3f, 0x6a, 0x69, 0x3c, 0x3c, 0x69, 0x6a, 0x3f, 0x65, 0x30, 0x33, 0x66,
  49         0x03, 0x56, 0x55, 0x00, 0x5a, 0x0f, 0x0c, 0x59, 0x59, 0x0c, 0x0f, 0x5a, 0x00, 0x55, 0x56, 0x03,
  50         0x69, 0x3c, 0x3f, 0x6a, 0x30, 0x65, 0x66, 0x33, 0x33, 0x66, 0x65, 0x30, 0x6a, 0x3f, 0x3c, 0x69,
  51         0x0c, 0x59, 0x5a, 0x0f, 0x55, 0x00, 0x03, 0x56, 0x56, 0x03, 0x00, 0x55, 0x0f, 0x5a, 0x59, 0x0c,
  52         0x0f, 0x5a, 0x59, 0x0c, 0x56, 0x03, 0x00, 0x55, 0x55, 0x00, 0x03, 0x56, 0x0c, 0x59, 0x5a, 0x0f,
  53         0x6a, 0x3f, 0x3c, 0x69, 0x33, 0x66, 0x65, 0x30, 0x30, 0x65, 0x66, 0x33, 0x69, 0x3c, 0x3f, 0x6a,
  54         0x6a, 0x3f, 0x3c, 0x69, 0x33, 0x66, 0x65, 0x30, 0x30, 0x65, 0x66, 0x33, 0x69, 0x3c, 0x3f, 0x6a,
  55         0x0f, 0x5a, 0x59, 0x0c, 0x56, 0x03, 0x00, 0x55, 0x55, 0x00, 0x03, 0x56, 0x0c, 0x59, 0x5a, 0x0f,
  56         0x0c, 0x59, 0x5a, 0x0f, 0x55, 0x00, 0x03, 0x56, 0x56, 0x03, 0x00, 0x55, 0x0f, 0x5a, 0x59, 0x0c,
  57         0x69, 0x3c, 0x3f, 0x6a, 0x30, 0x65, 0x66, 0x33, 0x33, 0x66, 0x65, 0x30, 0x6a, 0x3f, 0x3c, 0x69,
  58         0x03, 0x56, 0x55, 0x00, 0x5a, 0x0f, 0x0c, 0x59, 0x59, 0x0c, 0x0f, 0x5a, 0x00, 0x55, 0x56, 0x03,
  59         0x66, 0x33, 0x30, 0x65, 0x3f, 0x6a, 0x69, 0x3c, 0x3c, 0x69, 0x6a, 0x3f, 0x65, 0x30, 0x33, 0x66,
  60         0x65, 0x30, 0x33, 0x66, 0x3c, 0x69, 0x6a, 0x3f, 0x3f, 0x6a, 0x69, 0x3c, 0x66, 0x33, 0x30, 0x65,
  61         0x00, 0x55, 0x56, 0x03, 0x59, 0x0c, 0x0f, 0x5a, 0x5a, 0x0f, 0x0c, 0x59, 0x03, 0x56, 0x55, 0x00
  62 };
  63
  64
  65 /**
  66  * nand_trans_result - [GENERIC] create non-inverted ECC
  67  * @reg2:       line parity reg 2
  68  * @reg3:       line parity reg 3
  69  * @ecc_code:   ecc
  70  *
  71  * Creates non-inverted ECC code from line parity
  72  */
  73 static void nand_trans_result(u_char reg2, u_char reg3,
  74         u_char *ecc_code)
  75 {
  76         u_char a, b, i, tmp1, tmp2;
  77
  78         /* Initialize variables */
  79         a = b = 0x80;
  80         tmp1 = tmp2 = 0;
  81
  82         /* Calculate first ECC byte */
  83         for (i = 0; i < 4; i++) {
  84                 if (reg3 & a)           /* LP15,13,11,9 --> ecc_code[0] */
  85                         tmp1 |= b;
  86                 b >>= 1;
  87                 if (reg2 & a)           /* LP14,12,10,8 --> ecc_code[0] */
  88                         tmp1 |= b;
  89                 b >>= 1;
  90                 a >>= 1;
  91         }
  92
  93         /* Calculate second ECC byte */
  94         b = 0x80;
  95         for (i = 0; i < 4; i++) {
  96                 if (reg3 & a)           /* LP7,5,3,1 --> ecc_code[1] */
  97                         tmp2 |= b;
  98                 b >>= 1;
  99                 if (reg2 & a)           /* LP6,4,2,0 --> ecc_code[1] */
 100                         tmp2 |= b;
 101                 b >>= 1;
 102                 a >>= 1;
 103         }
 104
 105         /* Store two of the ECC bytes */
 106         ecc_code[0] = tmp1;
 107         ecc_code[1] = tmp2;
 108 }
 109
 110 /**
 111  * nand_calculate_ecc - [NAND Interface] Calculate 3 byte ECC code for 256 byte block
 112  * @mtd:        MTD block structure
 113  * @dat:        raw data
 114  * @ecc_code:   buffer for ECC
 115  */
 116 int nand_calculate_ecc(struct mtd_info *mtd, const u_char *dat, u_char *ecc_code)
 117 {
 118         u_char idx, reg1, reg2, reg3;
 119         int j;
 120
 121         /* Initialize variables */
 122         reg1 = reg2 = reg3 = 0;
 123         ecc_code[0] = ecc_code[1] = ecc_code[2] = 0;
 124
 125         /* Build up column parity */
 126         for(j = 0; j < 256; j++) {
 127
 128                 /* Get CP0 - CP5 from table */
 129                 idx = nand_ecc_precalc_table[dat[j]];
 130                 reg1 ^= (idx & 0x3f);
 131
 132                 /* All bit XOR = 1 ? */
 133                 if (idx & 0x40) {
 134                         reg3 ^= (u_char) j;
 135                         reg2 ^= ~((u_char) j);
 136                 }
 137         }
 138
 139         /* Create non-inverted ECC code from line parity */
 140         nand_trans_result(reg2, reg3, ecc_code);
 141
 142         /* Calculate final ECC code */
 143         ecc_code[0] = ~ecc_code[0];
 144         ecc_code[1] = ~ecc_code[1];
 145         ecc_code[2] = ((~reg1) << 2) | 0x03;
 146         return 0;
 147 }
 148
 149 /**
 150  * nand_correct_data - [NAND Interface] Detect and correct bit error(s)
 151  * @mtd:        MTD block structure
 152  * @dat:        raw data read from the chip
 153  * @read_ecc:   ECC from the chip
 154  * @calc_ecc:   the ECC calculated from raw data
 155  *
 156  * Detect and correct a 1 bit error for 256 byte block
 157  */
 158 int nand_correct_data(struct mtd_info *mtd, u_char *dat, u_char *read_ecc, u_char *calc_ecc)
 159 {
 160         u_char a, b, c, d1, d2, d3, add, bit, i;
 161
 162         /* Do error detection */
 163         d1 = calc_ecc[0] ^ read_ecc[0];
 164         d2 = calc_ecc[1] ^ read_ecc[1];
 165         d3 = calc_ecc[2] ^ read_ecc[2];
 166
 167         if ((d1 | d2 | d3) == 0) {
 168                 /* No errors */
 169                 return 0;
 170         }
 171         else {
 172                 a = (d1 ^ (d1 >> 1)) & 0x55;
 173                 b = (d2 ^ (d2 >> 1)) & 0x55;
 174                 c = (d3 ^ (d3 >> 1)) & 0x54;
 175
 176                 /* Found and will correct single bit error in the data */
 177                 if ((a == 0x55) && (b == 0x55) && (c == 0x54)) {
 178                         c = 0x80;
 179                         add = 0;
 180                         a = 0x80;
 181                         for (i=0; i<4; i++) {
 182                                 if (d1 & c)
 183                                         add |= a;
 184                                 c >>= 2;
 185                                 a >>= 1;
 186                         }
 187                         c = 0x80;
 188                         for (i=0; i<4; i++) {
 189                                 if (d2 & c)
 190                                         add |= a;
 191                                 c >>= 2;
 192                                 a >>= 1;
 193                         }
 194                         bit = 0;
 195                         b = 0x04;
 196                         c = 0x80;
 197                         for (i=0; i<3; i++) {
 198                                 if (d3 & c)
 199                                         bit |= b;
 200                                 c >>= 2;
 201                                 b >>= 1;
 202                         }
 203                         b = 0x01;
 204                         a = dat[add];
 205                         a ^= (b << bit);
 206                         dat[add] = a;
 207                         return 1;
 208                 } else {
 209                         i = 0;
 210                         while (d1) {
 211                                 if (d1 & 0x01)
 212                                         ++i;
 213                                 d1 >>= 1;
 214                         }
 215                         while (d2) {
 216                                 if (d2 & 0x01)
 217                                         ++i;
 218                                 d2 >>= 1;
 219                         }
 220                         while (d3) {
 221                                 if (d3 & 0x01)
 222                                         ++i;
 223                                 d3 >>= 1;
 224                         }
 225                         if (i == 1) {
 226                                 /* ECC Code Error Correction */
 227                                 read_ecc[0] = calc_ecc[0];
 228                                 read_ecc[1] = calc_ecc[1];
 229                                 read_ecc[2] = calc_ecc[2];
 230                                 return 2;
 231                         }
 232                         else {
 233                                 /* Uncorrectable Error */
 234                                 return -1;
 235                         }
 236                 }
 237         }
 238
 239         /* Should never happen */
 240         return -1;
 241 }
 242
 243 #endif  /* CONFIG_COMMANDS & CFG_CMD_NAND */