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 along
  25  * with this file; if not, write to the Free Software Foundation, Inc.,
  26  * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
  27  *
  28  * As a special exception, if other files instantiate templates or use
  29  * macros or inline functions from these files, or you compile these
  30  * files and link them with other works to produce a work based on these
  31  * files, these files do not by themselves cause the resulting work to be
  32  * covered by the GNU General Public License. However the source code for
  33  * these files must still be made available in accordance with section (3)
  34  * of the GNU General Public License.
  35  *
  36  * This exception does not invalidate any other reasons why a work based on
  37  * this file might be covered by the GNU General Public License.
  38  */
  39
  40 #ifdef HAVE_CONFIG_H
  41 #include "config.h"
  42 #endif
  43
  44 #include "core.h"
  45
  46 /*
  47  * Pre-calculated 256-way 1 byte column parity
  48  */
  49 static const uint8_t nand_ecc_precalc_table[] = {
  50         0x00, 0x55, 0x56, 0x03, 0x59, 0x0c, 0x0f, 0x5a, 0x5a, 0x0f, 0x0c, 0x59, 0x03, 0x56, 0x55, 0x00,
  51         0x65, 0x30, 0x33, 0x66, 0x3c, 0x69, 0x6a, 0x3f, 0x3f, 0x6a, 0x69, 0x3c, 0x66, 0x33, 0x30, 0x65,
  52         0x66, 0x33, 0x30, 0x65, 0x3f, 0x6a, 0x69, 0x3c, 0x3c, 0x69, 0x6a, 0x3f, 0x65, 0x30, 0x33, 0x66,
  53         0x03, 0x56, 0x55, 0x00, 0x5a, 0x0f, 0x0c, 0x59, 0x59, 0x0c, 0x0f, 0x5a, 0x00, 0x55, 0x56, 0x03,
  54         0x69, 0x3c, 0x3f, 0x6a, 0x30, 0x65, 0x66, 0x33, 0x33, 0x66, 0x65, 0x30, 0x6a, 0x3f, 0x3c, 0x69,
  55         0x0c, 0x59, 0x5a, 0x0f, 0x55, 0x00, 0x03, 0x56, 0x56, 0x03, 0x00, 0x55, 0x0f, 0x5a, 0x59, 0x0c,
  56         0x0f, 0x5a, 0x59, 0x0c, 0x56, 0x03, 0x00, 0x55, 0x55, 0x00, 0x03, 0x56, 0x0c, 0x59, 0x5a, 0x0f,
  57         0x6a, 0x3f, 0x3c, 0x69, 0x33, 0x66, 0x65, 0x30, 0x30, 0x65, 0x66, 0x33, 0x69, 0x3c, 0x3f, 0x6a,
  58         0x6a, 0x3f, 0x3c, 0x69, 0x33, 0x66, 0x65, 0x30, 0x30, 0x65, 0x66, 0x33, 0x69, 0x3c, 0x3f, 0x6a,
  59         0x0f, 0x5a, 0x59, 0x0c, 0x56, 0x03, 0x00, 0x55, 0x55, 0x00, 0x03, 0x56, 0x0c, 0x59, 0x5a, 0x0f,
  60         0x0c, 0x59, 0x5a, 0x0f, 0x55, 0x00, 0x03, 0x56, 0x56, 0x03, 0x00, 0x55, 0x0f, 0x5a, 0x59, 0x0c,
  61         0x69, 0x3c, 0x3f, 0x6a, 0x30, 0x65, 0x66, 0x33, 0x33, 0x66, 0x65, 0x30, 0x6a, 0x3f, 0x3c, 0x69,
  62         0x03, 0x56, 0x55, 0x00, 0x5a, 0x0f, 0x0c, 0x59, 0x59, 0x0c, 0x0f, 0x5a, 0x00, 0x55, 0x56, 0x03,
  63         0x66, 0x33, 0x30, 0x65, 0x3f, 0x6a, 0x69, 0x3c, 0x3c, 0x69, 0x6a, 0x3f, 0x65, 0x30, 0x33, 0x66,
  64         0x65, 0x30, 0x33, 0x66, 0x3c, 0x69, 0x6a, 0x3f, 0x3f, 0x6a, 0x69, 0x3c, 0x66, 0x33, 0x30, 0x65,
  65         0x00, 0x55, 0x56, 0x03, 0x59, 0x0c, 0x0f, 0x5a, 0x5a, 0x0f, 0x0c, 0x59, 0x03, 0x56, 0x55, 0x00
  66 };
  67
  68 /*
  69  * nand_calculate_ecc - Calculate 3-byte ECC for 256-byte block
  70  */
  71 int nand_calculate_ecc(struct nand_device *nand, const uint8_t *dat, uint8_t *ecc_code)
  72 {
  73         uint8_t idx, reg1, reg2, reg3, tmp1, tmp2;
  74         int i;
  75
  76         /* Initialize variables */
  77         reg1 = reg2 = reg3 = 0;
  78
  79         /* Build up column parity */
  80         for (i = 0; i < 256; i++) {
  81                 /* Get CP0 - CP5 from table */
  82                 idx = nand_ecc_precalc_table[*dat++];
  83                 reg1 ^= (idx & 0x3f);
  84
  85                 /* All bit XOR = 1 ? */
  86                 if (idx & 0x40) {
  87                         reg3 ^= (uint8_t) i;
  88                         reg2 ^= ~((uint8_t) i);
  89                 }
  90         }
  91
  92         /* Create non-inverted ECC code from line parity */
  93         tmp1  = (reg3 & 0x80) >> 0; /* B7 -> B7 */
  94         tmp1 |= (reg2 & 0x80) >> 1; /* B7 -> B6 */
  95         tmp1 |= (reg3 & 0x40) >> 1; /* B6 -> B5 */
  96         tmp1 |= (reg2 & 0x40) >> 2; /* B6 -> B4 */
  97         tmp1 |= (reg3 & 0x20) >> 2; /* B5 -> B3 */
  98         tmp1 |= (reg2 & 0x20) >> 3; /* B5 -> B2 */
  99         tmp1 |= (reg3 & 0x10) >> 3; /* B4 -> B1 */
 100         tmp1 |= (reg2 & 0x10) >> 4; /* B4 -> B0 */
 101
 102         tmp2  = (reg3 & 0x08) << 4; /* B3 -> B7 */
 103         tmp2 |= (reg2 & 0x08) << 3; /* B3 -> B6 */
 104         tmp2 |= (reg3 & 0x04) << 3; /* B2 -> B5 */
 105         tmp2 |= (reg2 & 0x04) << 2; /* B2 -> B4 */
 106         tmp2 |= (reg3 & 0x02) << 2; /* B1 -> B3 */
 107         tmp2 |= (reg2 & 0x02) << 1; /* B1 -> B2 */
 108         tmp2 |= (reg3 & 0x01) << 1; /* B0 -> B1 */
 109         tmp2 |= (reg2 & 0x01) << 0; /* B7 -> B0 */
 110
 111         /* Calculate final ECC code */
 112 #ifdef NAND_ECC_SMC
 113         ecc_code[0] = ~tmp2;
 114         ecc_code[1] = ~tmp1;
 115 #else
 116         ecc_code[0] = ~tmp1;
 117         ecc_code[1] = ~tmp2;
 118 #endif
 119         ecc_code[2] = ((~reg1) << 2) | 0x03;
 120
 121         return 0;
 122 }
 123
 124 static inline int countbits(uint32_t b)
 125 {
 126         int res = 0;
 127
 128         for (; b; b >>= 1)
 129                 res += b & 0x01;
 130         return res;
 131 }
 132
 133 /**
 134  * nand_correct_data - Detect and correct a 1 bit error for 256 byte block
 135  */
 136 int nand_correct_data(struct nand_device *nand, u_char *dat,
 137                 u_char *read_ecc, u_char *calc_ecc)
 138 {
 139         uint8_t s0, s1, s2;
 140
 141 #ifdef NAND_ECC_SMC
 142         s0 = calc_ecc[0] ^ read_ecc[0];
 143         s1 = calc_ecc[1] ^ read_ecc[1];
 144         s2 = calc_ecc[2] ^ read_ecc[2];
 145 #else
 146         s1 = calc_ecc[0] ^ read_ecc[0];
 147         s0 = calc_ecc[1] ^ read_ecc[1];
 148         s2 = calc_ecc[2] ^ read_ecc[2];
 149 #endif
 150         if ((s0 | s1 | s2) == 0)
 151                 return 0;
 152
 153         /* Check for a single bit error */
 154         if (((s0 ^ (s0 >> 1)) & 0x55) == 0x55 &&
 155                         ((s1 ^ (s1 >> 1)) & 0x55) == 0x55 &&
 156                         ((s2 ^ (s2 >> 1)) & 0x54) == 0x54) {
 157
 158                 uint32_t byteoffs, bitnum;
 159
 160                 byteoffs = (s1 << 0) & 0x80;
 161                 byteoffs |= (s1 << 1) & 0x40;
 162                 byteoffs |= (s1 << 2) & 0x20;
 163                 byteoffs |= (s1 << 3) & 0x10;
 164
 165                 byteoffs |= (s0 >> 4) & 0x08;
 166                 byteoffs |= (s0 >> 3) & 0x04;
 167                 byteoffs |= (s0 >> 2) & 0x02;
 168                 byteoffs |= (s0 >> 1) & 0x01;
 169
 170                 bitnum = (s2 >> 5) & 0x04;
 171                 bitnum |= (s2 >> 4) & 0x02;
 172                 bitnum |= (s2 >> 3) & 0x01;
 173
 174                 dat[byteoffs] ^= (1 << bitnum);
 175
 176                 return 1;
 177         }
 178
 179         if (countbits(s0 | ((uint32_t)s1 << 8) | ((uint32_t)s2 << 16)) == 1)
 180                 return 1;
 181
 182         return -1;
 183 }