diff options
Diffstat (limited to 'drivers/mtd/nand/nand_ecc.c')
| -rw-r--r-- | drivers/mtd/nand/nand_ecc.c | 250 |
1 files changed, 250 insertions, 0 deletions
diff --git a/drivers/mtd/nand/nand_ecc.c b/drivers/mtd/nand/nand_ecc.c new file mode 100644 index 00000000000..2e341b75437 --- /dev/null +++ b/drivers/mtd/nand/nand_ecc.c @@ -0,0 +1,250 @@ +/* + * 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 1.14 2004/06/16 15:34:37 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 <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_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 <sjhill@realitydiluted.com>"); +MODULE_DESCRIPTION("Generic NAND ECC support"); |