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819d6a32c3
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 <tglx@linutronix.de>
200 lines
6.7 KiB
C
200 lines
6.7 KiB
C
/*
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* This file contains an ECC algorithm from Toshiba that detects and
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* corrects 1 bit errors in a 256 byte block of data.
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*
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* drivers/mtd/nand/nand_ecc.c
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*
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* Copyright (C) 2000-2004 Steven J. Hill (sjhill@realitydiluted.com)
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* Toshiba America Electronics Components, Inc.
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*
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* Copyright (C) 2006 Thomas Gleixner <tglx@linutronix.de>
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*
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* $Id: nand_ecc.c,v 1.15 2005/11/07 11:14:30 gleixner Exp $
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*
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* This file is free software; you can redistribute it and/or modify it
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* under the terms of the GNU General Public License as published by the
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* Free Software Foundation; either version 2 or (at your option) any
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* later version.
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*
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* This file is distributed in the hope that it will be useful, but WITHOUT
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* ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
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* FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
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* for more details.
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*
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* You should have received a copy of the GNU General Public License along
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* with this file; if not, write to the Free Software Foundation, Inc.,
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* 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA.
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*
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* As a special exception, if other files instantiate templates or use
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* macros or inline functions from these files, or you compile these
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* files and link them with other works to produce a work based on these
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* files, these files do not by themselves cause the resulting work to be
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* covered by the GNU General Public License. However the source code for
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* these files must still be made available in accordance with section (3)
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* of the GNU General Public License.
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*
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* This exception does not invalidate any other reasons why a work based on
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* this file might be covered by the GNU General Public License.
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*/
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#include <linux/types.h>
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#include <linux/kernel.h>
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#include <linux/module.h>
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#include <linux/mtd/nand_ecc.h>
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/*
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* Pre-calculated 256-way 1 byte column parity
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*/
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static const u_char nand_ecc_precalc_table[] = {
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0x00, 0x55, 0x56, 0x03, 0x59, 0x0c, 0x0f, 0x5a, 0x5a, 0x0f, 0x0c, 0x59, 0x03, 0x56, 0x55, 0x00,
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0x65, 0x30, 0x33, 0x66, 0x3c, 0x69, 0x6a, 0x3f, 0x3f, 0x6a, 0x69, 0x3c, 0x66, 0x33, 0x30, 0x65,
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0x66, 0x33, 0x30, 0x65, 0x3f, 0x6a, 0x69, 0x3c, 0x3c, 0x69, 0x6a, 0x3f, 0x65, 0x30, 0x33, 0x66,
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0x03, 0x56, 0x55, 0x00, 0x5a, 0x0f, 0x0c, 0x59, 0x59, 0x0c, 0x0f, 0x5a, 0x00, 0x55, 0x56, 0x03,
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0x69, 0x3c, 0x3f, 0x6a, 0x30, 0x65, 0x66, 0x33, 0x33, 0x66, 0x65, 0x30, 0x6a, 0x3f, 0x3c, 0x69,
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0x0c, 0x59, 0x5a, 0x0f, 0x55, 0x00, 0x03, 0x56, 0x56, 0x03, 0x00, 0x55, 0x0f, 0x5a, 0x59, 0x0c,
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0x0f, 0x5a, 0x59, 0x0c, 0x56, 0x03, 0x00, 0x55, 0x55, 0x00, 0x03, 0x56, 0x0c, 0x59, 0x5a, 0x0f,
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0x6a, 0x3f, 0x3c, 0x69, 0x33, 0x66, 0x65, 0x30, 0x30, 0x65, 0x66, 0x33, 0x69, 0x3c, 0x3f, 0x6a,
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0x6a, 0x3f, 0x3c, 0x69, 0x33, 0x66, 0x65, 0x30, 0x30, 0x65, 0x66, 0x33, 0x69, 0x3c, 0x3f, 0x6a,
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0x0f, 0x5a, 0x59, 0x0c, 0x56, 0x03, 0x00, 0x55, 0x55, 0x00, 0x03, 0x56, 0x0c, 0x59, 0x5a, 0x0f,
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0x0c, 0x59, 0x5a, 0x0f, 0x55, 0x00, 0x03, 0x56, 0x56, 0x03, 0x00, 0x55, 0x0f, 0x5a, 0x59, 0x0c,
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0x69, 0x3c, 0x3f, 0x6a, 0x30, 0x65, 0x66, 0x33, 0x33, 0x66, 0x65, 0x30, 0x6a, 0x3f, 0x3c, 0x69,
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0x03, 0x56, 0x55, 0x00, 0x5a, 0x0f, 0x0c, 0x59, 0x59, 0x0c, 0x0f, 0x5a, 0x00, 0x55, 0x56, 0x03,
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0x66, 0x33, 0x30, 0x65, 0x3f, 0x6a, 0x69, 0x3c, 0x3c, 0x69, 0x6a, 0x3f, 0x65, 0x30, 0x33, 0x66,
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0x65, 0x30, 0x33, 0x66, 0x3c, 0x69, 0x6a, 0x3f, 0x3f, 0x6a, 0x69, 0x3c, 0x66, 0x33, 0x30, 0x65,
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0x00, 0x55, 0x56, 0x03, 0x59, 0x0c, 0x0f, 0x5a, 0x5a, 0x0f, 0x0c, 0x59, 0x03, 0x56, 0x55, 0x00
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};
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/**
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* nand_calculate_ecc - [NAND Interface] Calculate 3 byte ECC code
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* for 256 byte block
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* @mtd: MTD block structure
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* @dat: raw data
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* @ecc_code: buffer for ECC
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*/
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int nand_calculate_ecc(struct mtd_info *mtd, const u_char *dat,
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u_char *ecc_code)
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{
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uint8_t idx, reg1, reg2, reg3, tmp1, tmp2;
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int i;
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/* Initialize variables */
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reg1 = reg2 = reg3 = 0;
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/* Build up column parity */
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for(i = 0; i < 256; i++) {
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/* Get CP0 - CP5 from table */
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idx = nand_ecc_precalc_table[*dat++];
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reg1 ^= (idx & 0x3f);
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/* All bit XOR = 1 ? */
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if (idx & 0x40) {
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reg3 ^= (uint8_t) i;
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reg2 ^= ~((uint8_t) i);
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}
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}
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/* Create non-inverted ECC code from line parity */
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tmp1 = (reg3 & 0x80) >> 0; /* B7 -> B7 */
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tmp1 |= (reg2 & 0x80) >> 1; /* B7 -> B6 */
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tmp1 |= (reg3 & 0x40) >> 1; /* B6 -> B5 */
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tmp1 |= (reg2 & 0x40) >> 2; /* B6 -> B4 */
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tmp1 |= (reg3 & 0x20) >> 2; /* B5 -> B3 */
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tmp1 |= (reg2 & 0x20) >> 3; /* B5 -> B2 */
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tmp1 |= (reg3 & 0x10) >> 3; /* B4 -> B1 */
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tmp1 |= (reg2 & 0x10) >> 4; /* B4 -> B0 */
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tmp2 = (reg3 & 0x08) << 4; /* B3 -> B7 */
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tmp2 |= (reg2 & 0x08) << 3; /* B3 -> B6 */
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tmp2 |= (reg3 & 0x04) << 3; /* B2 -> B5 */
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tmp2 |= (reg2 & 0x04) << 2; /* B2 -> B4 */
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tmp2 |= (reg3 & 0x02) << 2; /* B1 -> B3 */
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tmp2 |= (reg2 & 0x02) << 1; /* B1 -> B2 */
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tmp2 |= (reg3 & 0x01) << 1; /* B0 -> B1 */
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tmp2 |= (reg2 & 0x01) << 0; /* B7 -> B0 */
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/* Calculate final ECC code */
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#ifdef CONFIG_NAND_ECC_SMC
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ecc_code[0] = ~tmp2;
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ecc_code[1] = ~tmp1;
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#else
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ecc_code[0] = ~tmp1;
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ecc_code[1] = ~tmp2;
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#endif
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ecc_code[2] = ((~reg1) << 2) | 0x03;
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return 0;
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}
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EXPORT_SYMBOL(nand_calculate_ecc);
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static inline int countbits(uint32_t byte)
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{
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int res = 0;
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for (;byte; byte >>= 1)
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res += byte & 0x01;
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return res;
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}
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/**
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* nand_correct_data - [NAND Interface] Detect and correct bit error(s)
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* @mtd: MTD block structure
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* @dat: raw data read from the chip
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* @read_ecc: ECC from the chip
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* @calc_ecc: the ECC calculated from raw data
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*
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* Detect and correct a 1 bit error for 256 byte block
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*/
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int nand_correct_data(struct mtd_info *mtd, u_char *dat,
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u_char *read_ecc, u_char *calc_ecc)
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{
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uint8_t s0, s1, s2;
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#ifdef CONFIG_NAND_ECC_SMC
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s0 = calc_ecc[0] ^ read_ecc[0];
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s1 = calc_ecc[1] ^ read_ecc[1];
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s2 = calc_ecc[2] ^ read_ecc[2];
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#else
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s1 = calc_ecc[0] ^ read_ecc[0];
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s0 = calc_ecc[1] ^ read_ecc[1];
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s2 = calc_ecc[2] ^ read_ecc[2];
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#endif
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if ((s0 | s1 | s2) == 0)
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return 0;
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/* Check for a single bit error */
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if( ((s0 ^ (s0 >> 1)) & 0x55) == 0x55 &&
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((s1 ^ (s1 >> 1)) & 0x55) == 0x55 &&
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((s2 ^ (s2 >> 1)) & 0x54) == 0x54) {
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uint32_t byteoffs, bitnum;
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byteoffs = (s1 << 0) & 0x80;
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byteoffs |= (s1 << 1) & 0x40;
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byteoffs |= (s1 << 2) & 0x20;
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byteoffs |= (s1 << 3) & 0x10;
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byteoffs |= (s0 >> 4) & 0x08;
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byteoffs |= (s0 >> 3) & 0x04;
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byteoffs |= (s0 >> 2) & 0x02;
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byteoffs |= (s0 >> 1) & 0x01;
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bitnum = (s2 >> 5) & 0x04;
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bitnum |= (s2 >> 4) & 0x02;
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bitnum |= (s2 >> 3) & 0x01;
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dat[byteoffs] ^= (1 << bitnum);
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return 1;
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}
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if(countbits(s0 | ((uint32_t)s1 << 8) | ((uint32_t)s2 <<16)) == 1)
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return 1;
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return -1;
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}
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EXPORT_SYMBOL(nand_correct_data);
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MODULE_LICENSE("GPL");
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MODULE_AUTHOR("Steven J. Hill <sjhill@realitydiluted.com>");
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MODULE_DESCRIPTION("Generic NAND ECC support");
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