src/flash/nand/ecc.c

   1 // SPDX-License-Identifier: GPL-2.0-or-later WITH eCos-exception-2.0
   2
   3 /*
   4  * This file contains an ECC algorithm from Toshiba that allows for detection
   5  * and correction of 1-bit errors in a 256 byte block of data.
   6  *
   7  * [ Extracted from the initial code found in some early Linux versions.
   8  *   The current Linux code is bigger while being faster, but this is of
   9  *   no real benefit when the bottleneck largely remains the JTAG link.  ]
  10  *
  11  * Copyright (C) 2000-2004 Steven J. Hill (sjhill at realitydiluted.com)
  12  *                         Toshiba America Electronics Components, Inc.
  13  *
  14  * Copyright (C) 2006 Thomas Gleixner <tglx at linutronix.de>
  15  */
  16
  17 #ifdef HAVE_CONFIG_H
  18 #include "config.h"
  19 #endif
  20
  21 #include "core.h"
  22
  23 /*
  24  * Pre-calculated 256-way 1 byte column parity
  25  */
  26 static const uint8_t nand_ecc_precalc_table[] = {
  27         0x00, 0x55, 0x56, 0x03, 0x59, 0x0c, 0x0f, 0x5a, 0x5a, 0x0f, 0x0c, 0x59, 0x03, 0x56, 0x55, 0x00,
  28         0x65, 0x30, 0x33, 0x66, 0x3c, 0x69, 0x6a, 0x3f, 0x3f, 0x6a, 0x69, 0x3c, 0x66, 0x33, 0x30, 0x65,
  29         0x66, 0x33, 0x30, 0x65, 0x3f, 0x6a, 0x69, 0x3c, 0x3c, 0x69, 0x6a, 0x3f, 0x65, 0x30, 0x33, 0x66,
  30         0x03, 0x56, 0x55, 0x00, 0x5a, 0x0f, 0x0c, 0x59, 0x59, 0x0c, 0x0f, 0x5a, 0x00, 0x55, 0x56, 0x03,
  31         0x69, 0x3c, 0x3f, 0x6a, 0x30, 0x65, 0x66, 0x33, 0x33, 0x66, 0x65, 0x30, 0x6a, 0x3f, 0x3c, 0x69,
  32         0x0c, 0x59, 0x5a, 0x0f, 0x55, 0x00, 0x03, 0x56, 0x56, 0x03, 0x00, 0x55, 0x0f, 0x5a, 0x59, 0x0c,
  33         0x0f, 0x5a, 0x59, 0x0c, 0x56, 0x03, 0x00, 0x55, 0x55, 0x00, 0x03, 0x56, 0x0c, 0x59, 0x5a, 0x0f,
  34         0x6a, 0x3f, 0x3c, 0x69, 0x33, 0x66, 0x65, 0x30, 0x30, 0x65, 0x66, 0x33, 0x69, 0x3c, 0x3f, 0x6a,
  35         0x6a, 0x3f, 0x3c, 0x69, 0x33, 0x66, 0x65, 0x30, 0x30, 0x65, 0x66, 0x33, 0x69, 0x3c, 0x3f, 0x6a,
  36         0x0f, 0x5a, 0x59, 0x0c, 0x56, 0x03, 0x00, 0x55, 0x55, 0x00, 0x03, 0x56, 0x0c, 0x59, 0x5a, 0x0f,
  37         0x0c, 0x59, 0x5a, 0x0f, 0x55, 0x00, 0x03, 0x56, 0x56, 0x03, 0x00, 0x55, 0x0f, 0x5a, 0x59, 0x0c,
  38         0x69, 0x3c, 0x3f, 0x6a, 0x30, 0x65, 0x66, 0x33, 0x33, 0x66, 0x65, 0x30, 0x6a, 0x3f, 0x3c, 0x69,
  39         0x03, 0x56, 0x55, 0x00, 0x5a, 0x0f, 0x0c, 0x59, 0x59, 0x0c, 0x0f, 0x5a, 0x00, 0x55, 0x56, 0x03,
  40         0x66, 0x33, 0x30, 0x65, 0x3f, 0x6a, 0x69, 0x3c, 0x3c, 0x69, 0x6a, 0x3f, 0x65, 0x30, 0x33, 0x66,
  41         0x65, 0x30, 0x33, 0x66, 0x3c, 0x69, 0x6a, 0x3f, 0x3f, 0x6a, 0x69, 0x3c, 0x66, 0x33, 0x30, 0x65,
  42         0x00, 0x55, 0x56, 0x03, 0x59, 0x0c, 0x0f, 0x5a, 0x5a, 0x0f, 0x0c, 0x59, 0x03, 0x56, 0x55, 0x00
  43 };
  44
  45 /*
  46  * nand_calculate_ecc - Calculate 3-byte ECC for 256-byte block
  47  */
  48 int nand_calculate_ecc(struct nand_device *nand, const uint8_t *dat, uint8_t *ecc_code)
  49 {
  50         uint8_t idx, reg1, reg2, reg3, tmp1, tmp2;
  51         int i;
  52
  53         /* Initialize variables */
  54         reg1 = reg2 = reg3 = 0;
  55
  56         /* Build up column parity */
  57         for (i = 0; i < 256; i++) {
  58                 /* Get CP0 - CP5 from table */
  59                 idx = nand_ecc_precalc_table[*dat++];
  60                 reg1 ^= (idx & 0x3f);
  61
  62                 /* All bit XOR = 1 ? */
  63                 if (idx & 0x40) {
  64                         reg3 ^= (uint8_t) i;
  65                         reg2 ^= ~((uint8_t) i);
  66                 }
  67         }
  68
  69         /* Create non-inverted ECC code from line parity */
  70         tmp1  = (reg3 & 0x80) >> 0; /* B7 -> B7 */
  71         tmp1 |= (reg2 & 0x80) >> 1; /* B7 -> B6 */
  72         tmp1 |= (reg3 & 0x40) >> 1; /* B6 -> B5 */
  73         tmp1 |= (reg2 & 0x40) >> 2; /* B6 -> B4 */
  74         tmp1 |= (reg3 & 0x20) >> 2; /* B5 -> B3 */
  75         tmp1 |= (reg2 & 0x20) >> 3; /* B5 -> B2 */
  76         tmp1 |= (reg3 & 0x10) >> 3; /* B4 -> B1 */
  77         tmp1 |= (reg2 & 0x10) >> 4; /* B4 -> B0 */
  78
  79         tmp2  = (reg3 & 0x08) << 4; /* B3 -> B7 */
  80         tmp2 |= (reg2 & 0x08) << 3; /* B3 -> B6 */
  81         tmp2 |= (reg3 & 0x04) << 3; /* B2 -> B5 */
  82         tmp2 |= (reg2 & 0x04) << 2; /* B2 -> B4 */
  83         tmp2 |= (reg3 & 0x02) << 2; /* B1 -> B3 */
  84         tmp2 |= (reg2 & 0x02) << 1; /* B1 -> B2 */
  85         tmp2 |= (reg3 & 0x01) << 1; /* B0 -> B1 */
  86         tmp2 |= (reg2 & 0x01) << 0; /* B7 -> B0 */
  87
  88         /* Calculate final ECC code */
  89 #ifdef NAND_ECC_SMC
  90         ecc_code[0] = ~tmp2;
  91         ecc_code[1] = ~tmp1;
  92 #else
  93         ecc_code[0] = ~tmp1;
  94         ecc_code[1] = ~tmp2;
  95 #endif
  96         ecc_code[2] = ((~reg1) << 2) | 0x03;
  97
  98         return 0;
  99 }
 100
 101 static inline int countbits(uint32_t b)
 102 {
 103         int res = 0;
 104
 105         for (; b; b >>= 1)
 106                 res += b & 0x01;
 107         return res;
 108 }
 109
 110 /**
 111  * nand_correct_data - Detect and correct a 1 bit error for 256 byte block
 112  */
 113 int nand_correct_data(struct nand_device *nand, u_char *dat,
 114                 u_char *read_ecc, u_char *calc_ecc)
 115 {
 116         uint8_t s0, s1, s2;
 117
 118 #ifdef NAND_ECC_SMC
 119         s0 = calc_ecc[0] ^ read_ecc[0];
 120         s1 = calc_ecc[1] ^ read_ecc[1];
 121         s2 = calc_ecc[2] ^ read_ecc[2];
 122 #else
 123         s1 = calc_ecc[0] ^ read_ecc[0];
 124         s0 = calc_ecc[1] ^ read_ecc[1];
 125         s2 = calc_ecc[2] ^ read_ecc[2];
 126 #endif
 127         if ((s0 | s1 | s2) == 0)
 128                 return 0;
 129
 130         /* Check for a single bit error */
 131         if (((s0 ^ (s0 >> 1)) & 0x55) == 0x55 &&
 132                         ((s1 ^ (s1 >> 1)) & 0x55) == 0x55 &&
 133                         ((s2 ^ (s2 >> 1)) & 0x54) == 0x54) {
 134
 135                 uint32_t byteoffs, bitnum;
 136
 137                 byteoffs = (s1 << 0) & 0x80;
 138                 byteoffs |= (s1 << 1) & 0x40;
 139                 byteoffs |= (s1 << 2) & 0x20;
 140                 byteoffs |= (s1 << 3) & 0x10;
 141
 142                 byteoffs |= (s0 >> 4) & 0x08;
 143                 byteoffs |= (s0 >> 3) & 0x04;
 144                 byteoffs |= (s0 >> 2) & 0x02;
 145                 byteoffs |= (s0 >> 1) & 0x01;
 146
 147                 bitnum = (s2 >> 5) & 0x04;
 148                 bitnum |= (s2 >> 4) & 0x02;
 149                 bitnum |= (s2 >> 3) & 0x01;
 150
 151                 dat[byteoffs] ^= (1 << bitnum);
 152
 153                 return 1;
 154         }
 155
 156         if (countbits(s0 | ((uint32_t)s1 << 8) | ((uint32_t)s2 << 16)) == 1)
 157                 return 1;
 158
 159         return -1;
 160 }