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  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. #ifdef HAVE_CONFIG_H
  40. #include "config.h"
  41. #endif
  42. #include "core.h"
  43. /*
  44. * Pre-calculated 256-way 1 byte column parity
  45. */
  46. static const uint8_t nand_ecc_precalc_table[] = {
  47. 0x00, 0x55, 0x56, 0x03, 0x59, 0x0c, 0x0f, 0x5a, 0x5a, 0x0f, 0x0c, 0x59, 0x03, 0x56, 0x55, 0x00,
  48. 0x65, 0x30, 0x33, 0x66, 0x3c, 0x69, 0x6a, 0x3f, 0x3f, 0x6a, 0x69, 0x3c, 0x66, 0x33, 0x30, 0x65,
  49. 0x66, 0x33, 0x30, 0x65, 0x3f, 0x6a, 0x69, 0x3c, 0x3c, 0x69, 0x6a, 0x3f, 0x65, 0x30, 0x33, 0x66,
  50. 0x03, 0x56, 0x55, 0x00, 0x5a, 0x0f, 0x0c, 0x59, 0x59, 0x0c, 0x0f, 0x5a, 0x00, 0x55, 0x56, 0x03,
  51. 0x69, 0x3c, 0x3f, 0x6a, 0x30, 0x65, 0x66, 0x33, 0x33, 0x66, 0x65, 0x30, 0x6a, 0x3f, 0x3c, 0x69,
  52. 0x0c, 0x59, 0x5a, 0x0f, 0x55, 0x00, 0x03, 0x56, 0x56, 0x03, 0x00, 0x55, 0x0f, 0x5a, 0x59, 0x0c,
  53. 0x0f, 0x5a, 0x59, 0x0c, 0x56, 0x03, 0x00, 0x55, 0x55, 0x00, 0x03, 0x56, 0x0c, 0x59, 0x5a, 0x0f,
  54. 0x6a, 0x3f, 0x3c, 0x69, 0x33, 0x66, 0x65, 0x30, 0x30, 0x65, 0x66, 0x33, 0x69, 0x3c, 0x3f, 0x6a,
  55. 0x6a, 0x3f, 0x3c, 0x69, 0x33, 0x66, 0x65, 0x30, 0x30, 0x65, 0x66, 0x33, 0x69, 0x3c, 0x3f, 0x6a,
  56. 0x0f, 0x5a, 0x59, 0x0c, 0x56, 0x03, 0x00, 0x55, 0x55, 0x00, 0x03, 0x56, 0x0c, 0x59, 0x5a, 0x0f,
  57. 0x0c, 0x59, 0x5a, 0x0f, 0x55, 0x00, 0x03, 0x56, 0x56, 0x03, 0x00, 0x55, 0x0f, 0x5a, 0x59, 0x0c,
  58. 0x69, 0x3c, 0x3f, 0x6a, 0x30, 0x65, 0x66, 0x33, 0x33, 0x66, 0x65, 0x30, 0x6a, 0x3f, 0x3c, 0x69,
  59. 0x03, 0x56, 0x55, 0x00, 0x5a, 0x0f, 0x0c, 0x59, 0x59, 0x0c, 0x0f, 0x5a, 0x00, 0x55, 0x56, 0x03,
  60. 0x66, 0x33, 0x30, 0x65, 0x3f, 0x6a, 0x69, 0x3c, 0x3c, 0x69, 0x6a, 0x3f, 0x65, 0x30, 0x33, 0x66,
  61. 0x65, 0x30, 0x33, 0x66, 0x3c, 0x69, 0x6a, 0x3f, 0x3f, 0x6a, 0x69, 0x3c, 0x66, 0x33, 0x30, 0x65,
  62. 0x00, 0x55, 0x56, 0x03, 0x59, 0x0c, 0x0f, 0x5a, 0x5a, 0x0f, 0x0c, 0x59, 0x03, 0x56, 0x55, 0x00
  63. };
  64. /*
  65. * nand_calculate_ecc - Calculate 3-byte ECC for 256-byte block
  66. */
  67. int nand_calculate_ecc(struct nand_device *nand, const uint8_t *dat, uint8_t *ecc_code)
  68. {
  69. uint8_t idx, reg1, reg2, reg3, tmp1, tmp2;
  70. int i;
  71. /* Initialize variables */
  72. reg1 = reg2 = reg3 = 0;
  73. /* Build up column parity */
  74. for (i = 0; i < 256; i++) {
  75. /* Get CP0 - CP5 from table */
  76. idx = nand_ecc_precalc_table[*dat++];
  77. reg1 ^= (idx & 0x3f);
  78. /* All bit XOR = 1 ? */
  79. if (idx & 0x40) {
  80. reg3 ^= (uint8_t) i;
  81. reg2 ^= ~((uint8_t) i);
  82. }
  83. }
  84. /* Create non-inverted ECC code from line parity */
  85. tmp1 = (reg3 & 0x80) >> 0; /* B7 -> B7 */
  86. tmp1 |= (reg2 & 0x80) >> 1; /* B7 -> B6 */
  87. tmp1 |= (reg3 & 0x40) >> 1; /* B6 -> B5 */
  88. tmp1 |= (reg2 & 0x40) >> 2; /* B6 -> B4 */
  89. tmp1 |= (reg3 & 0x20) >> 2; /* B5 -> B3 */
  90. tmp1 |= (reg2 & 0x20) >> 3; /* B5 -> B2 */
  91. tmp1 |= (reg3 & 0x10) >> 3; /* B4 -> B1 */
  92. tmp1 |= (reg2 & 0x10) >> 4; /* B4 -> B0 */
  93. tmp2 = (reg3 & 0x08) << 4; /* B3 -> B7 */
  94. tmp2 |= (reg2 & 0x08) << 3; /* B3 -> B6 */
  95. tmp2 |= (reg3 & 0x04) << 3; /* B2 -> B5 */
  96. tmp2 |= (reg2 & 0x04) << 2; /* B2 -> B4 */
  97. tmp2 |= (reg3 & 0x02) << 2; /* B1 -> B3 */
  98. tmp2 |= (reg2 & 0x02) << 1; /* B1 -> B2 */
  99. tmp2 |= (reg3 & 0x01) << 1; /* B0 -> B1 */
  100. tmp2 |= (reg2 & 0x01) << 0; /* B7 -> B0 */
  101. /* Calculate final ECC code */
  102. #ifdef NAND_ECC_SMC
  103. ecc_code[0] = ~tmp2;
  104. ecc_code[1] = ~tmp1;
  105. #else
  106. ecc_code[0] = ~tmp1;
  107. ecc_code[1] = ~tmp2;
  108. #endif
  109. ecc_code[2] = ((~reg1) << 2) | 0x03;
  110. return 0;
  111. }
  112. static inline int countbits(uint32_t b)
  113. {
  114. int res = 0;
  115. for (; b; b >>= 1)
  116. res += b & 0x01;
  117. return res;
  118. }
  119. /**
  120. * nand_correct_data - Detect and correct a 1 bit error for 256 byte block
  121. */
  122. int nand_correct_data(struct nand_device *nand, u_char *dat,
  123. u_char *read_ecc, u_char *calc_ecc)
  124. {
  125. uint8_t s0, s1, s2;
  126. #ifdef NAND_ECC_SMC
  127. s0 = calc_ecc[0] ^ read_ecc[0];
  128. s1 = calc_ecc[1] ^ read_ecc[1];
  129. s2 = calc_ecc[2] ^ read_ecc[2];
  130. #else
  131. s1 = calc_ecc[0] ^ read_ecc[0];
  132. s0 = calc_ecc[1] ^ read_ecc[1];
  133. s2 = calc_ecc[2] ^ read_ecc[2];
  134. #endif
  135. if ((s0 | s1 | s2) == 0)
  136. return 0;
  137. /* Check for a single bit error */
  138. if (((s0 ^ (s0 >> 1)) & 0x55) == 0x55 &&
  139. ((s1 ^ (s1 >> 1)) & 0x55) == 0x55 &&
  140. ((s2 ^ (s2 >> 1)) & 0x54) == 0x54) {
  141. uint32_t byteoffs, bitnum;
  142. byteoffs = (s1 << 0) & 0x80;
  143. byteoffs |= (s1 << 1) & 0x40;
  144. byteoffs |= (s1 << 2) & 0x20;
  145. byteoffs |= (s1 << 3) & 0x10;
  146. byteoffs |= (s0 >> 4) & 0x08;
  147. byteoffs |= (s0 >> 3) & 0x04;
  148. byteoffs |= (s0 >> 2) & 0x02;
  149. byteoffs |= (s0 >> 1) & 0x01;
  150. bitnum = (s2 >> 5) & 0x04;
  151. bitnum |= (s2 >> 4) & 0x02;
  152. bitnum |= (s2 >> 3) & 0x01;
  153. dat[byteoffs] ^= (1 << bitnum);
  154. return 1;
  155. }
  156. if (countbits(s0 | ((uint32_t)s1 << 8) | ((uint32_t)s2 << 16)) == 1)
  157. return 1;
  158. return -1;
  159. }