From 819d6a32c397534c819d3c72a3947b7e7e4bec4b Mon Sep 17 00:00:00 2001 From: Thomas Gleixner Date: Tue, 23 May 2006 11:32:45 +0200 Subject: [PATCH] [MTD] Improve software ECC calculation Unrolling the loops produces denser and much faster code. Add a config switch which allows to select the byte order of the resulting ecc code. The current Linux implementation has a byte swap versus the SmartMedia specification Signed-off-by: Thomas Gleixner --- drivers/mtd/nand/Kconfig | 8 ++ drivers/mtd/nand/nand_ecc.c | 222 ++++++++++++++---------------------- 2 files changed, 96 insertions(+), 134 deletions(-) diff --git a/drivers/mtd/nand/Kconfig b/drivers/mtd/nand/Kconfig index 2d0ebad55a..4d235b9126 100644 --- a/drivers/mtd/nand/Kconfig +++ b/drivers/mtd/nand/Kconfig @@ -23,6 +23,14 @@ config MTD_NAND_VERIFY_WRITE device thinks the write was successful, a bit could have been flipped accidentaly due to device wear or something else. +config MTD_NAND_ECC_SMC + bool "NAND ECC Smart Media byte order" + depends on MTD_NAND + default n + help + Software ECC according to the Smart Media Specification. + The original Linux implementation had byte 0 and 1 swapped. + config MTD_NAND_AUTCPU12 tristate "SmartMediaCard on autronix autcpu12 board" depends on MTD_NAND && ARCH_AUTCPU12 diff --git a/drivers/mtd/nand/nand_ecc.c b/drivers/mtd/nand/nand_ecc.c index 101892985b..2a163e4084 100644 --- a/drivers/mtd/nand/nand_ecc.c +++ b/drivers/mtd/nand/nand_ecc.c @@ -7,6 +7,8 @@ * Copyright (C) 2000-2004 Steven J. Hill (sjhill@realitydiluted.com) * Toshiba America Electronics Components, Inc. * + * Copyright (C) 2006 Thomas Gleixner + * * $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 @@ -63,87 +65,75 @@ static const u_char nand_ecc_precalc_table[] = { }; /** - * 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 + * 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) +int nand_calculate_ecc(struct mtd_info *mtd, const u_char *dat, + u_char *ecc_code) { - u_char idx, reg1, reg2, reg3; - int j; + uint8_t idx, reg1, reg2, reg3, tmp1, tmp2; + int i; /* 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++) { - + for(i = 0; i < 256; i++) { /* Get CP0 - CP5 from table */ - idx = nand_ecc_precalc_table[dat[j]]; + idx = nand_ecc_precalc_table[*dat++]; reg1 ^= (idx & 0x3f); /* All bit XOR = 1 ? */ if (idx & 0x40) { - reg3 ^= (u_char) j; - reg2 ^= ~((u_char) j); + reg3 ^= (uint8_t) i; + reg2 ^= ~((uint8_t) i); } } /* Create non-inverted ECC code from line parity */ - nand_trans_result(reg2, reg3, ecc_code); + 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 */ - ecc_code[0] = ~ecc_code[0]; - ecc_code[1] = ~ecc_code[1]; +#ifdef CONFIG_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) @@ -154,90 +144,54 @@ int nand_calculate_ecc(struct mtd_info *mtd, const u_char *dat, u_char *ecc_code * * 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) +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; + uint8_t s0, s1, s2; + +#ifdef CONFIG_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; - /* Do error detection */ - d1 = calc_ecc[0] ^ read_ecc[0]; - d2 = calc_ecc[1] ^ read_ecc[1]; - d3 = calc_ecc[2] ^ read_ecc[2]; + /* Check for a single bit error */ + if( ((s0 ^ (s0 >> 1)) & 0x55) == 0x55 && + ((s1 ^ (s1 >> 1)) & 0x55) == 0x55 && + ((s2 ^ (s2 >> 1)) & 0x54) == 0x54) { - 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; - } - } + 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; } - /* Should never happen */ + if(countbits(s0 | ((uint32_t)s1 << 8) | ((uint32_t)s2 <<16)) == 1) + return 1; + return -1; } - -EXPORT_SYMBOL(nand_calculate_ecc); EXPORT_SYMBOL(nand_correct_data); MODULE_LICENSE("GPL"); -- 2.39.5