/* * 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. * * Copyright (C) 2006 Thomas Gleixner <tglx@linutronix.de> * * 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 <linux/types.h> #include <linux/kernel.h> #include <linux/module.h> #include <linux/mtd/nand_ecc.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 }; /** * nand_calculate_ecc - [NAND Interface] Calculate 3-byte ECC 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) { uint8_t idx, reg1, reg2, reg3, tmp1, tmp2; int i; /* Initialize variables */ reg1 = reg2 = reg3 = 0; /* Build up column parity */ for(i = 0; i < 256; i++) { /* Get CP0 - CP5 from table */ idx = nand_ecc_precalc_table[*dat++]; reg1 ^= (idx & 0x3f); /* All bit XOR = 1 ? */ if (idx & 0x40) { reg3 ^= (uint8_t) i; reg2 ^= ~((uint8_t) i); } } /* Create non-inverted ECC code from line parity */ tmp1 = (reg3 & 0x80) >> 0; /* B7 -> B7 */ tmp1 |= (reg2 & 0x80) >> 1; /* B7 -> B6 */ tmp1 |= (reg3 & 0x40) >> 1; /* B6 -> B5 */ tmp1 |= (reg2 & 0x40) >> 2; /* B6 -> B4 */ tmp1 |= (reg3 & 0x20) >> 2; /* B5 -> B3 */ tmp1 |= (reg2 & 0x20) >> 3; /* B5 -> B2 */ tmp1 |= (reg3 & 0x10) >> 3; /* B4 -> B1 */ tmp1 |= (reg2 & 0x10) >> 4; /* B4 -> B0 */ tmp2 = (reg3 & 0x08) << 4; /* B3 -> B7 */ tmp2 |= (reg2 & 0x08) << 3; /* B3 -> B6 */ tmp2 |= (reg3 & 0x04) << 3; /* B2 -> B5 */ tmp2 |= (reg2 & 0x04) << 2; /* B2 -> B4 */ tmp2 |= (reg3 & 0x02) << 2; /* B1 -> B3 */ tmp2 |= (reg2 & 0x02) << 1; /* B1 -> B2 */ tmp2 |= (reg3 & 0x01) << 1; /* B0 -> B1 */ tmp2 |= (reg2 & 0x01) << 0; /* B7 -> B0 */ /* Calculate final ECC code */ #ifdef CONFIG_MTD_NAND_ECC_SMC ecc_code[0] = ~tmp2; ecc_code[1] = ~tmp1; #else ecc_code[0] = ~tmp1; ecc_code[1] = ~tmp2; #endif ecc_code[2] = ((~reg1) << 2) | 0x03; return 0; } EXPORT_SYMBOL(nand_calculate_ecc); static inline int countbits(uint32_t byte) { int res = 0; for (;byte; byte >>= 1) res += byte & 0x01; return res; } /** * 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) { uint8_t s0, s1, s2; #ifdef CONFIG_MTD_NAND_ECC_SMC s0 = calc_ecc[0] ^ read_ecc[0]; s1 = calc_ecc[1] ^ read_ecc[1]; s2 = calc_ecc[2] ^ read_ecc[2]; #else s1 = calc_ecc[0] ^ read_ecc[0]; s0 = calc_ecc[1] ^ read_ecc[1]; s2 = calc_ecc[2] ^ read_ecc[2]; #endif if ((s0 | s1 | s2) == 0) return 0; /* Check for a single bit error */ if( ((s0 ^ (s0 >> 1)) & 0x55) == 0x55 && ((s1 ^ (s1 >> 1)) & 0x55) == 0x55 && ((s2 ^ (s2 >> 1)) & 0x54) == 0x54) { uint32_t byteoffs, bitnum; byteoffs = (s1 << 0) & 0x80; byteoffs |= (s1 << 1) & 0x40; byteoffs |= (s1 << 2) & 0x20; byteoffs |= (s1 << 3) & 0x10; byteoffs |= (s0 >> 4) & 0x08; byteoffs |= (s0 >> 3) & 0x04; byteoffs |= (s0 >> 2) & 0x02; byteoffs |= (s0 >> 1) & 0x01; bitnum = (s2 >> 5) & 0x04; bitnum |= (s2 >> 4) & 0x02; bitnum |= (s2 >> 3) & 0x01; dat[byteoffs] ^= (1 << bitnum); return 1; } if(countbits(s0 | ((uint32_t)s1 << 8) | ((uint32_t)s2 <<16)) == 1) return 1; return -EBADMSG; } EXPORT_SYMBOL(nand_correct_data); MODULE_LICENSE("GPL"); MODULE_AUTHOR("Steven J. Hill <sjhill@realitydiluted.com>"); MODULE_DESCRIPTION("Generic NAND ECC support");