/* * This file contains an ECC algorithm from Toshiba that detects and * corrects 1 bit errors in a 256 byte block of data. * * drivers/mtd/nand/nand_ecc.c * * Copyright (C) 2000-2004 Steven J. Hill (sjhill@realitydiluted.com) * Toshiba America Electronics Components, Inc. * * $Id: nand_ecc.c,v 1.15 2005/11/07 11:14:30 gleixner Exp $ * * This file is free software; you can redistribute it and/or modify it * under the terms of the GNU General Public License as published by the * Free Software Foundation; either version 2 or (at your option) any * later version. * * This file is distributed in the hope that it will be useful, but WITHOUT * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License * for more details. * * You should have received a copy of the GNU General Public License along * with this file; if not, write to the Free Software Foundation, Inc., * 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA. * * As a special exception, if other files instantiate templates or use * macros or inline functions from these files, or you compile these * files and link them with other works to produce a work based on these * files, these files do not by themselves cause the resulting work to be * covered by the GNU General Public License. However the source code for * these files must still be made available in accordance with section (3) * of the GNU General Public License. * * This exception does not invalidate any other reasons why a work based on * this file might be covered by the GNU General Public License. */ #include #include #include #include /* * 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 }; /** * nand_trans_result - [GENERIC] create non-inverted ECC * @reg2: line parity reg 2 * @reg3: line parity reg 3 * @ecc_code: ecc * * 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; } /** * nand_calculate_ecc - [NAND Interface] Calculate 3 byte ECC code for 256 byte block * @mtd: MTD block structure * @dat: raw data * @ecc_code: buffer for ECC */ int nand_calculate_ecc(struct mtd_info *mtd, 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; return 0; } /** * nand_correct_data - [NAND Interface] Detect and correct bit error(s) * @mtd: MTD block structure * @dat: raw data read from the chip * @read_ecc: ECC from the chip * @calc_ecc: the ECC calculated from raw data * * Detect and correct a 1 bit error for 256 byte block */ int nand_correct_data(struct mtd_info *mtd, 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 "); MODULE_DESCRIPTION("Generic NAND ECC support");