| /* |
| * drivers/mtd/nand_ecc.c |
| * |
| * Copyright (C) 2000 Steven J. Hill (sjhill@cotw.com) |
| * Toshiba America Electronics Components, Inc. |
| * |
| * $Id: nand_ecc.c,v 1.6 2001/06/28 10:52:26 dwmw2 Exp $ |
| * |
| * This program is free software; you can redistribute it and/or modify |
| * it under the terms of the GNU General Public License version 2 as |
| * published by the Free Software Foundation. |
| * |
| * This file contains an ECC algorithm from Toshiba that detects and |
| * corrects 1 bit errors in a 256 byte block of data. |
| */ |
| |
| #include <linux/types.h> |
| #include <linux/kernel.h> |
| #include <linux/module.h> |
| |
| /* |
| * Pre-calculated 256-way 1 byte column parity |
| */ |
| static const u_char nand_ecc_precalc_table[] = { |
| 0x00, 0x55, 0x56, 0x03, 0x59, 0x0c, 0x0f, 0x5a, 0x5a, 0x0f, 0x0c, 0x59, 0x03, 0x56, 0x55, 0x00, |
| 0x65, 0x30, 0x33, 0x66, 0x3c, 0x69, 0x6a, 0x3f, 0x3f, 0x6a, 0x69, 0x3c, 0x66, 0x33, 0x30, 0x65, |
| 0x66, 0x33, 0x30, 0x65, 0x3f, 0x6a, 0x69, 0x3c, 0x3c, 0x69, 0x6a, 0x3f, 0x65, 0x30, 0x33, 0x66, |
| 0x03, 0x56, 0x55, 0x00, 0x5a, 0x0f, 0x0c, 0x59, 0x59, 0x0c, 0x0f, 0x5a, 0x00, 0x55, 0x56, 0x03, |
| 0x69, 0x3c, 0x3f, 0x6a, 0x30, 0x65, 0x66, 0x33, 0x33, 0x66, 0x65, 0x30, 0x6a, 0x3f, 0x3c, 0x69, |
| 0x0c, 0x59, 0x5a, 0x0f, 0x55, 0x00, 0x03, 0x56, 0x56, 0x03, 0x00, 0x55, 0x0f, 0x5a, 0x59, 0x0c, |
| 0x0f, 0x5a, 0x59, 0x0c, 0x56, 0x03, 0x00, 0x55, 0x55, 0x00, 0x03, 0x56, 0x0c, 0x59, 0x5a, 0x0f, |
| 0x6a, 0x3f, 0x3c, 0x69, 0x33, 0x66, 0x65, 0x30, 0x30, 0x65, 0x66, 0x33, 0x69, 0x3c, 0x3f, 0x6a, |
| 0x6a, 0x3f, 0x3c, 0x69, 0x33, 0x66, 0x65, 0x30, 0x30, 0x65, 0x66, 0x33, 0x69, 0x3c, 0x3f, 0x6a, |
| 0x0f, 0x5a, 0x59, 0x0c, 0x56, 0x03, 0x00, 0x55, 0x55, 0x00, 0x03, 0x56, 0x0c, 0x59, 0x5a, 0x0f, |
| 0x0c, 0x59, 0x5a, 0x0f, 0x55, 0x00, 0x03, 0x56, 0x56, 0x03, 0x00, 0x55, 0x0f, 0x5a, 0x59, 0x0c, |
| 0x69, 0x3c, 0x3f, 0x6a, 0x30, 0x65, 0x66, 0x33, 0x33, 0x66, 0x65, 0x30, 0x6a, 0x3f, 0x3c, 0x69, |
| 0x03, 0x56, 0x55, 0x00, 0x5a, 0x0f, 0x0c, 0x59, 0x59, 0x0c, 0x0f, 0x5a, 0x00, 0x55, 0x56, 0x03, |
| 0x66, 0x33, 0x30, 0x65, 0x3f, 0x6a, 0x69, 0x3c, 0x3c, 0x69, 0x6a, 0x3f, 0x65, 0x30, 0x33, 0x66, |
| 0x65, 0x30, 0x33, 0x66, 0x3c, 0x69, 0x6a, 0x3f, 0x3f, 0x6a, 0x69, 0x3c, 0x66, 0x33, 0x30, 0x65, |
| 0x00, 0x55, 0x56, 0x03, 0x59, 0x0c, 0x0f, 0x5a, 0x5a, 0x0f, 0x0c, 0x59, 0x03, 0x56, 0x55, 0x00 |
| }; |
| |
| |
| /* |
| * Creates non-inverted ECC code from line parity |
| */ |
| static void nand_trans_result(u_char reg2, u_char reg3, |
| u_char *ecc_code) |
| { |
| u_char a, b, i, tmp1, tmp2; |
| |
| /* Initialize variables */ |
| a = b = 0x80; |
| tmp1 = tmp2 = 0; |
| |
| /* Calculate first ECC byte */ |
| for (i = 0; i < 4; i++) { |
| if (reg3 & a) /* LP15,13,11,9 --> ecc_code[0] */ |
| tmp1 |= b; |
| b >>= 1; |
| if (reg2 & a) /* LP14,12,10,8 --> ecc_code[0] */ |
| tmp1 |= b; |
| b >>= 1; |
| a >>= 1; |
| } |
| |
| /* Calculate second ECC byte */ |
| b = 0x80; |
| for (i = 0; i < 4; i++) { |
| if (reg3 & a) /* LP7,5,3,1 --> ecc_code[1] */ |
| tmp2 |= b; |
| b >>= 1; |
| if (reg2 & a) /* LP6,4,2,0 --> ecc_code[1] */ |
| tmp2 |= b; |
| b >>= 1; |
| a >>= 1; |
| } |
| |
| /* Store two of the ECC bytes */ |
| ecc_code[0] = tmp1; |
| ecc_code[1] = tmp2; |
| } |
| |
| /* |
| * Calculate 3 byte ECC code for 256 byte block |
| */ |
| void nand_calculate_ecc (const u_char *dat, u_char *ecc_code) |
| { |
| u_char idx, reg1, reg2, reg3; |
| int j; |
| |
| /* Initialize variables */ |
| reg1 = reg2 = reg3 = 0; |
| ecc_code[0] = ecc_code[1] = ecc_code[2] = 0; |
| |
| /* Build up column parity */ |
| for(j = 0; j < 256; j++) { |
| |
| /* Get CP0 - CP5 from table */ |
| idx = nand_ecc_precalc_table[dat[j]]; |
| reg1 ^= (idx & 0x3f); |
| |
| /* All bit XOR = 1 ? */ |
| if (idx & 0x40) { |
| reg3 ^= (u_char) j; |
| reg2 ^= ~((u_char) j); |
| } |
| } |
| |
| /* Create non-inverted ECC code from line parity */ |
| nand_trans_result(reg2, reg3, ecc_code); |
| |
| /* Calculate final ECC code */ |
| ecc_code[0] = ~ecc_code[0]; |
| ecc_code[1] = ~ecc_code[1]; |
| ecc_code[2] = ((~reg1) << 2) | 0x03; |
| } |
| |
| /* |
| * Detect and correct a 1 bit error for 256 byte block |
| */ |
| int nand_correct_data (u_char *dat, u_char *read_ecc, u_char *calc_ecc) |
| { |
| u_char a, b, c, d1, d2, d3, add, bit, i; |
| |
| /* Do error detection */ |
| d1 = calc_ecc[0] ^ read_ecc[0]; |
| d2 = calc_ecc[1] ^ read_ecc[1]; |
| d3 = calc_ecc[2] ^ read_ecc[2]; |
| |
| if ((d1 | d2 | d3) == 0) { |
| /* No errors */ |
| return 0; |
| } |
| else { |
| a = (d1 ^ (d1 >> 1)) & 0x55; |
| b = (d2 ^ (d2 >> 1)) & 0x55; |
| c = (d3 ^ (d3 >> 1)) & 0x54; |
| |
| /* Found and will correct single bit error in the data */ |
| if ((a == 0x55) && (b == 0x55) && (c == 0x54)) { |
| c = 0x80; |
| add = 0; |
| a = 0x80; |
| for (i=0; i<4; i++) { |
| if (d1 & c) |
| add |= a; |
| c >>= 2; |
| a >>= 1; |
| } |
| c = 0x80; |
| for (i=0; i<4; i++) { |
| if (d2 & c) |
| add |= a; |
| c >>= 2; |
| a >>= 1; |
| } |
| bit = 0; |
| b = 0x04; |
| c = 0x80; |
| for (i=0; i<3; i++) { |
| if (d3 & c) |
| bit |= b; |
| c >>= 2; |
| b >>= 1; |
| } |
| b = 0x01; |
| a = dat[add]; |
| a ^= (b << bit); |
| dat[add] = a; |
| return 1; |
| } |
| else { |
| i = 0; |
| while (d1) { |
| if (d1 & 0x01) |
| ++i; |
| d1 >>= 1; |
| } |
| while (d2) { |
| if (d2 & 0x01) |
| ++i; |
| d2 >>= 1; |
| } |
| while (d3) { |
| if (d3 & 0x01) |
| ++i; |
| d3 >>= 1; |
| } |
| if (i == 1) { |
| /* ECC Code Error Correction */ |
| read_ecc[0] = calc_ecc[0]; |
| read_ecc[1] = calc_ecc[1]; |
| read_ecc[2] = calc_ecc[2]; |
| return 2; |
| } |
| else { |
| /* Uncorrectable Error */ |
| return -1; |
| } |
| } |
| } |
| |
| /* Should never happen */ |
| return -1; |
| } |
| |
| EXPORT_SYMBOL(nand_calculate_ecc); |
| EXPORT_SYMBOL(nand_correct_data); |
| |
| MODULE_LICENSE("GPL"); |
| MODULE_AUTHOR("Steven J. Hill <sjhill@cotw.com>"); |
| MODULE_DESCRIPTION("Generic NAND ECC support"); |