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  * $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 defined(CONFIG_CMD_NAND) && !defined(CFG_NAND_LEGACY)
  41
  42 #include<linux/mtd/mtd.h>
  43
  44 /*
  45  * NAND-SPL has no sofware ECC for now, so don't include nand_calculate_ecc(),
  46  * only nand_correct_data() is needed
  47  */
  48
  49 #ifndef CONFIG_NAND_SPL
  50 /*
  51  * Pre-calculated 256-way 1 byte column parity
  52  */
  53 static const u_char nand_ecc_precalc_table[] = {
  54         0x00, 0x55, 0x56, 0x03, 0x59, 0x0c, 0x0f, 0x5a, 0x5a, 0x0f, 0x0c, 0x59, 0x03, 0x56, 0x55, 0x00,
  55         0x65, 0x30, 0x33, 0x66, 0x3c, 0x69, 0x6a, 0x3f, 0x3f, 0x6a, 0x69, 0x3c, 0x66, 0x33, 0x30, 0x65,
  56         0x66, 0x33, 0x30, 0x65, 0x3f, 0x6a, 0x69, 0x3c, 0x3c, 0x69, 0x6a, 0x3f, 0x65, 0x30, 0x33, 0x66,
  57         0x03, 0x56, 0x55, 0x00, 0x5a, 0x0f, 0x0c, 0x59, 0x59, 0x0c, 0x0f, 0x5a, 0x00, 0x55, 0x56, 0x03,
  58         0x69, 0x3c, 0x3f, 0x6a, 0x30, 0x65, 0x66, 0x33, 0x33, 0x66, 0x65, 0x30, 0x6a, 0x3f, 0x3c, 0x69,
  59         0x0c, 0x59, 0x5a, 0x0f, 0x55, 0x00, 0x03, 0x56, 0x56, 0x03, 0x00, 0x55, 0x0f, 0x5a, 0x59, 0x0c,
  60         0x0f, 0x5a, 0x59, 0x0c, 0x56, 0x03, 0x00, 0x55, 0x55, 0x00, 0x03, 0x56, 0x0c, 0x59, 0x5a, 0x0f,
  61         0x6a, 0x3f, 0x3c, 0x69, 0x33, 0x66, 0x65, 0x30, 0x30, 0x65, 0x66, 0x33, 0x69, 0x3c, 0x3f, 0x6a,
  62         0x6a, 0x3f, 0x3c, 0x69, 0x33, 0x66, 0x65, 0x30, 0x30, 0x65, 0x66, 0x33, 0x69, 0x3c, 0x3f, 0x6a,
  63         0x0f, 0x5a, 0x59, 0x0c, 0x56, 0x03, 0x00, 0x55, 0x55, 0x00, 0x03, 0x56, 0x0c, 0x59, 0x5a, 0x0f,
  64         0x0c, 0x59, 0x5a, 0x0f, 0x55, 0x00, 0x03, 0x56, 0x56, 0x03, 0x00, 0x55, 0x0f, 0x5a, 0x59, 0x0c,
  65         0x69, 0x3c, 0x3f, 0x6a, 0x30, 0x65, 0x66, 0x33, 0x33, 0x66, 0x65, 0x30, 0x6a, 0x3f, 0x3c, 0x69,
  66         0x03, 0x56, 0x55, 0x00, 0x5a, 0x0f, 0x0c, 0x59, 0x59, 0x0c, 0x0f, 0x5a, 0x00, 0x55, 0x56, 0x03,
  67         0x66, 0x33, 0x30, 0x65, 0x3f, 0x6a, 0x69, 0x3c, 0x3c, 0x69, 0x6a, 0x3f, 0x65, 0x30, 0x33, 0x66,
  68         0x65, 0x30, 0x33, 0x66, 0x3c, 0x69, 0x6a, 0x3f, 0x3f, 0x6a, 0x69, 0x3c, 0x66, 0x33, 0x30, 0x65,
  69         0x00, 0x55, 0x56, 0x03, 0x59, 0x0c, 0x0f, 0x5a, 0x5a, 0x0f, 0x0c, 0x59, 0x03, 0x56, 0x55, 0x00
  70 };
  71
  72 /**
  73  * nand_calculate_ecc - [NAND Interface] Calculate 3-byte ECC for 256-byte block
  74  * @mtd:        MTD block structure
  75  * @dat:        raw data
  76  * @ecc_code:   buffer for ECC
  77  */
  78 int nand_calculate_ecc(struct mtd_info *mtd, const u_char *dat,
  79                        u_char *ecc_code)
  80 {
  81         uint8_t idx, reg1, reg2, reg3, tmp1, tmp2;
  82         int i;
  83
  84         /* Initialize variables */
  85         reg1 = reg2 = reg3 = 0;
  86
  87         /* Build up column parity */
  88         for(i = 0; i < 256; i++) {
  89                 /* Get CP0 - CP5 from table */
  90                 idx = nand_ecc_precalc_table[*dat++];
  91                 reg1 ^= (idx & 0x3f);
  92
  93                 /* All bit XOR = 1 ? */
  94                 if (idx & 0x40) {
  95                         reg3 ^= (uint8_t) i;
  96                         reg2 ^= ~((uint8_t) i);
  97                 }
  98         }
  99
 100         /* Create non-inverted ECC code from line parity */
 101         tmp1  = (reg3 & 0x80) >> 0; /* B7 -> B7 */
 102         tmp1 |= (reg2 & 0x80) >> 1; /* B7 -> B6 */
 103         tmp1 |= (reg3 & 0x40) >> 1; /* B6 -> B5 */
 104         tmp1 |= (reg2 & 0x40) >> 2; /* B6 -> B4 */
 105         tmp1 |= (reg3 & 0x20) >> 2; /* B5 -> B3 */
 106         tmp1 |= (reg2 & 0x20) >> 3; /* B5 -> B2 */
 107         tmp1 |= (reg3 & 0x10) >> 3; /* B4 -> B1 */
 108         tmp1 |= (reg2 & 0x10) >> 4; /* B4 -> B0 */
 109
 110         tmp2  = (reg3 & 0x08) << 4; /* B3 -> B7 */
 111         tmp2 |= (reg2 & 0x08) << 3; /* B3 -> B6 */
 112         tmp2 |= (reg3 & 0x04) << 3; /* B2 -> B5 */
 113         tmp2 |= (reg2 & 0x04) << 2; /* B2 -> B4 */
 114         tmp2 |= (reg3 & 0x02) << 2; /* B1 -> B3 */
 115         tmp2 |= (reg2 & 0x02) << 1; /* B1 -> B2 */
 116         tmp2 |= (reg3 & 0x01) << 1; /* B0 -> B1 */
 117         tmp2 |= (reg2 & 0x01) << 0; /* B7 -> B0 */
 118
 119         /* Calculate final ECC code */
 120 #ifdef CONFIG_MTD_NAND_ECC_SMC
 121         ecc_code[0] = ~tmp2;
 122         ecc_code[1] = ~tmp1;
 123 #else
 124         ecc_code[0] = ~tmp1;
 125         ecc_code[1] = ~tmp2;
 126 #endif
 127         ecc_code[2] = ((~reg1) << 2) | 0x03;
 128
 129         return 0;
 130 }
 131 #endif /* CONFIG_NAND_SPL */
 132
 133 static inline int countbits(uint32_t byte)
 134 {
 135         int res = 0;
 136
 137         for (;byte; byte >>= 1)
 138                 res += byte & 0x01;
 139         return res;
 140 }
 141
 142 /**
 143  * nand_correct_data - [NAND Interface] Detect and correct bit error(s)
 144  * @mtd:        MTD block structure
 145  * @dat:        raw data read from the chip
 146  * @read_ecc:   ECC from the chip
 147  * @calc_ecc:   the ECC calculated from raw data
 148  *
 149  * Detect and correct a 1 bit error for 256 byte block
 150  */
 151 int nand_correct_data(struct mtd_info *mtd, u_char *dat,
 152                       u_char *read_ecc, u_char *calc_ecc)
 153 {
 154         uint8_t s0, s1, s2;
 155
 156 #ifdef CONFIG_MTD_NAND_ECC_SMC
 157         s0 = calc_ecc[0] ^ read_ecc[0];
 158         s1 = calc_ecc[1] ^ read_ecc[1];
 159         s2 = calc_ecc[2] ^ read_ecc[2];
 160 #else
 161         s1 = calc_ecc[0] ^ read_ecc[0];
 162         s0 = calc_ecc[1] ^ read_ecc[1];
 163         s2 = calc_ecc[2] ^ read_ecc[2];
 164 #endif
 165         if ((s0 | s1 | s2) == 0)
 166                 return 0;
 167
 168         /* Check for a single bit error */
 169         if( ((s0 ^ (s0 >> 1)) & 0x55) == 0x55 &&
 170             ((s1 ^ (s1 >> 1)) & 0x55) == 0x55 &&
 171             ((s2 ^ (s2 >> 1)) & 0x54) == 0x54) {
 172
 173                 uint32_t byteoffs, bitnum;
 174
 175                 byteoffs = (s1 << 0) & 0x80;
 176                 byteoffs |= (s1 << 1) & 0x40;
 177                 byteoffs |= (s1 << 2) & 0x20;
 178                 byteoffs |= (s1 << 3) & 0x10;
 179
 180                 byteoffs |= (s0 >> 4) & 0x08;
 181                 byteoffs |= (s0 >> 3) & 0x04;
 182                 byteoffs |= (s0 >> 2) & 0x02;
 183                 byteoffs |= (s0 >> 1) & 0x01;
 184
 185                 bitnum = (s2 >> 5) & 0x04;
 186                 bitnum |= (s2 >> 4) & 0x02;
 187                 bitnum |= (s2 >> 3) & 0x01;
 188
 189                 dat[byteoffs] ^= (1 << bitnum);
 190
 191                 return 1;
 192         }
 193
 194         if(countbits(s0 | ((uint32_t)s1 << 8) | ((uint32_t)s2 <<16)) == 1)
 195                 return 1;
 196
 197         return -1;
 198 }
 199
 200 #endif