src/flash/nand/ecc.c

   1 /*
   2  * This file contains an ECC algorithm from Toshiba that allows for detection
   3  * and correction of 1-bit errors in a 256 byte block of data.
   4  *
   5  * [ Extracted from the initial code found in some early Linux versions.
   6  *   The current Linux code is bigger while being faster, but this is of
   7  *   no real benefit when the bottleneck largely remains the JTAG link.  ]
   8  *
   9  * Copyright (C) 2000-2004 Steven J. Hill (sjhill at realitydiluted.com)
  10  *                         Toshiba America Electronics Components, Inc.
  11  *
  12  * Copyright (C) 2006 Thomas Gleixner <tglx at linutronix.de>
  13  *
  14  * This file is free software; you can redistribute it and/or modify it
  15  * under the terms of the GNU General Public License as published by the
  16  * Free Software Foundation; either version 2 or (at your option) any
  17  * later version.
  18  *
  19  * This file is distributed in the hope that it will be useful, but WITHOUT
  20  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
  21  * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
  22  * for more details.
  23  *
  24  * You should have received a copy of the GNU General Public License
  25  * along with this program.  If not, see <http://www.gnu.org/licenses/>.
  26  *
  27  * As a special exception, if other files instantiate templates or use
  28  * macros or inline functions from these files, or you compile these
  29  * files and link them with other works to produce a work based on these
  30  * files, these files do not by themselves cause the resulting work to be
  31  * covered by the GNU General Public License. However the source code for
  32  * these files must still be made available in accordance with section (3)
  33  * of the GNU General Public License.
  34  *
  35  * This exception does not invalidate any other reasons why a work based on
  36  * this file might be covered by the GNU General Public License.
  37  */
  38
  39 #ifdef HAVE_CONFIG_H
  40 #include "config.h"
  41 #endif
  42
  43 #include "core.h"
  44
  45 /*
  46  * Pre-calculated 256-way 1 byte column parity
  47  */
  48 static const uint8_t nand_ecc_precalc_table[] = {
  49         0x00, 0x55, 0x56, 0x03, 0x59, 0x0c, 0x0f, 0x5a, 0x5a, 0x0f, 0x0c, 0x59, 0x03, 0x56, 0x55, 0x00,
  50         0x65, 0x30, 0x33, 0x66, 0x3c, 0x69, 0x6a, 0x3f, 0x3f, 0x6a, 0x69, 0x3c, 0x66, 0x33, 0x30, 0x65,
  51         0x66, 0x33, 0x30, 0x65, 0x3f, 0x6a, 0x69, 0x3c, 0x3c, 0x69, 0x6a, 0x3f, 0x65, 0x30, 0x33, 0x66,
  52         0x03, 0x56, 0x55, 0x00, 0x5a, 0x0f, 0x0c, 0x59, 0x59, 0x0c, 0x0f, 0x5a, 0x00, 0x55, 0x56, 0x03,
  53         0x69, 0x3c, 0x3f, 0x6a, 0x30, 0x65, 0x66, 0x33, 0x33, 0x66, 0x65, 0x30, 0x6a, 0x3f, 0x3c, 0x69,
  54         0x0c, 0x59, 0x5a, 0x0f, 0x55, 0x00, 0x03, 0x56, 0x56, 0x03, 0x00, 0x55, 0x0f, 0x5a, 0x59, 0x0c,
  55         0x0f, 0x5a, 0x59, 0x0c, 0x56, 0x03, 0x00, 0x55, 0x55, 0x00, 0x03, 0x56, 0x0c, 0x59, 0x5a, 0x0f,
  56         0x6a, 0x3f, 0x3c, 0x69, 0x33, 0x66, 0x65, 0x30, 0x30, 0x65, 0x66, 0x33, 0x69, 0x3c, 0x3f, 0x6a,
  57         0x6a, 0x3f, 0x3c, 0x69, 0x33, 0x66, 0x65, 0x30, 0x30, 0x65, 0x66, 0x33, 0x69, 0x3c, 0x3f, 0x6a,
  58         0x0f, 0x5a, 0x59, 0x0c, 0x56, 0x03, 0x00, 0x55, 0x55, 0x00, 0x03, 0x56, 0x0c, 0x59, 0x5a, 0x0f,
  59         0x0c, 0x59, 0x5a, 0x0f, 0x55, 0x00, 0x03, 0x56, 0x56, 0x03, 0x00, 0x55, 0x0f, 0x5a, 0x59, 0x0c,
  60         0x69, 0x3c, 0x3f, 0x6a, 0x30, 0x65, 0x66, 0x33, 0x33, 0x66, 0x65, 0x30, 0x6a, 0x3f, 0x3c, 0x69,
  61         0x03, 0x56, 0x55, 0x00, 0x5a, 0x0f, 0x0c, 0x59, 0x59, 0x0c, 0x0f, 0x5a, 0x00, 0x55, 0x56, 0x03,
  62         0x66, 0x33, 0x30, 0x65, 0x3f, 0x6a, 0x69, 0x3c, 0x3c, 0x69, 0x6a, 0x3f, 0x65, 0x30, 0x33, 0x66,
  63         0x65, 0x30, 0x33, 0x66, 0x3c, 0x69, 0x6a, 0x3f, 0x3f, 0x6a, 0x69, 0x3c, 0x66, 0x33, 0x30, 0x65,
  64         0x00, 0x55, 0x56, 0x03, 0x59, 0x0c, 0x0f, 0x5a, 0x5a, 0x0f, 0x0c, 0x59, 0x03, 0x56, 0x55, 0x00
  65 };
  66
  67 /*
  68  * nand_calculate_ecc - Calculate 3-byte ECC for 256-byte block
  69  */
  70 int nand_calculate_ecc(struct nand_device *nand, const uint8_t *dat, uint8_t *ecc_code)
  71 {
  72         uint8_t idx, reg1, reg2, reg3, tmp1, tmp2;
  73         int i;
  74
  75         /* Initialize variables */
  76         reg1 = reg2 = reg3 = 0;
  77
  78         /* Build up column parity */
  79         for (i = 0; i < 256; i++) {
  80                 /* Get CP0 - CP5 from table */
  81                 idx = nand_ecc_precalc_table[*dat++];
  82                 reg1 ^= (idx & 0x3f);
  83
  84                 /* All bit XOR = 1 ? */
  85                 if (idx & 0x40) {
  86                         reg3 ^= (uint8_t) i;
  87                         reg2 ^= ~((uint8_t) i);
  88                 }
  89         }
  90
  91         /* Create non-inverted ECC code from line parity */
  92         tmp1  = (reg3 & 0x80) >> 0; /* B7 -> B7 */
  93         tmp1 |= (reg2 & 0x80) >> 1; /* B7 -> B6 */
  94         tmp1 |= (reg3 & 0x40) >> 1; /* B6 -> B5 */
  95         tmp1 |= (reg2 & 0x40) >> 2; /* B6 -> B4 */
  96         tmp1 |= (reg3 & 0x20) >> 2; /* B5 -> B3 */
  97         tmp1 |= (reg2 & 0x20) >> 3; /* B5 -> B2 */
  98         tmp1 |= (reg3 & 0x10) >> 3; /* B4 -> B1 */
  99         tmp1 |= (reg2 & 0x10) >> 4; /* B4 -> B0 */
 100
 101         tmp2  = (reg3 & 0x08) << 4; /* B3 -> B7 */
 102         tmp2 |= (reg2 & 0x08) << 3; /* B3 -> B6 */
 103         tmp2 |= (reg3 & 0x04) << 3; /* B2 -> B5 */
 104         tmp2 |= (reg2 & 0x04) << 2; /* B2 -> B4 */
 105         tmp2 |= (reg3 & 0x02) << 2; /* B1 -> B3 */
 106         tmp2 |= (reg2 & 0x02) << 1; /* B1 -> B2 */
 107         tmp2 |= (reg3 & 0x01) << 1; /* B0 -> B1 */
 108         tmp2 |= (reg2 & 0x01) << 0; /* B7 -> B0 */
 109
 110         /* Calculate final ECC code */
 111 #ifdef NAND_ECC_SMC
 112         ecc_code[0] = ~tmp2;
 113         ecc_code[1] = ~tmp1;
 114 #else
 115         ecc_code[0] = ~tmp1;
 116         ecc_code[1] = ~tmp2;
 117 #endif
 118         ecc_code[2] = ((~reg1) << 2) | 0x03;
 119
 120         return 0;
 121 }
 122
 123 static inline int countbits(uint32_t b)
 124 {
 125         int res = 0;
 126
 127         for (; b; b >>= 1)
 128                 res += b & 0x01;
 129         return res;
 130 }
 131
 132 /**
 133  * nand_correct_data - Detect and correct a 1 bit error for 256 byte block
 134  */
 135 int nand_correct_data(struct nand_device *nand, u_char *dat,
 136                 u_char *read_ecc, u_char *calc_ecc)
 137 {
 138         uint8_t s0, s1, s2;
 139
 140 #ifdef NAND_ECC_SMC
 141         s0 = calc_ecc[0] ^ read_ecc[0];
 142         s1 = calc_ecc[1] ^ read_ecc[1];
 143         s2 = calc_ecc[2] ^ read_ecc[2];
 144 #else
 145         s1 = calc_ecc[0] ^ read_ecc[0];
 146         s0 = calc_ecc[1] ^ read_ecc[1];
 147         s2 = calc_ecc[2] ^ read_ecc[2];
 148 #endif
 149         if ((s0 | s1 | s2) == 0)
 150                 return 0;
 151
 152         /* Check for a single bit error */
 153         if (((s0 ^ (s0 >> 1)) & 0x55) == 0x55 &&
 154                         ((s1 ^ (s1 >> 1)) & 0x55) == 0x55 &&
 155                         ((s2 ^ (s2 >> 1)) & 0x54) == 0x54) {
 156
 157                 uint32_t byteoffs, bitnum;
 158
 159                 byteoffs = (s1 << 0) & 0x80;
 160                 byteoffs |= (s1 << 1) & 0x40;
 161                 byteoffs |= (s1 << 2) & 0x20;
 162                 byteoffs |= (s1 << 3) & 0x10;
 163
 164                 byteoffs |= (s0 >> 4) & 0x08;
 165                 byteoffs |= (s0 >> 3) & 0x04;
 166                 byteoffs |= (s0 >> 2) & 0x02;
 167                 byteoffs |= (s0 >> 1) & 0x01;
 168
 169                 bitnum = (s2 >> 5) & 0x04;
 170                 bitnum |= (s2 >> 4) & 0x02;
 171                 bitnum |= (s2 >> 3) & 0x01;
 172
 173                 dat[byteoffs] ^= (1 << bitnum);
 174
 175                 return 1;
 176         }
 177
 178         if (countbits(s0 | ((uint32_t)s1 << 8) | ((uint32_t)s2 << 16)) == 1)
 179                 return 1;
 180
 181         return -1;
 182 }