250 lines
7 KiB
C
250 lines
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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* $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_trans_result - [GENERIC] create non-inverted ECC
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* @reg2: line parity reg 2
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* @reg3: line parity reg 3
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* @ecc_code: ecc
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*
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* Creates non-inverted ECC code from line parity
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*/
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static void nand_trans_result(u_char reg2, u_char reg3,
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u_char *ecc_code)
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{
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u_char a, b, i, tmp1, tmp2;
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/* Initialize variables */
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a = b = 0x80;
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tmp1 = tmp2 = 0;
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/* Calculate first ECC byte */
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for (i = 0; i < 4; i++) {
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if (reg3 & a) /* LP15,13,11,9 --> ecc_code[0] */
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tmp1 |= b;
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b >>= 1;
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if (reg2 & a) /* LP14,12,10,8 --> ecc_code[0] */
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tmp1 |= b;
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b >>= 1;
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a >>= 1;
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}
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/* Calculate second ECC byte */
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b = 0x80;
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for (i = 0; i < 4; i++) {
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if (reg3 & a) /* LP7,5,3,1 --> ecc_code[1] */
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tmp2 |= b;
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b >>= 1;
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if (reg2 & a) /* LP6,4,2,0 --> ecc_code[1] */
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tmp2 |= b;
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b >>= 1;
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a >>= 1;
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}
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/* Store two of the ECC bytes */
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ecc_code[0] = tmp1;
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ecc_code[1] = tmp2;
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}
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/**
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* nand_calculate_ecc - [NAND Interface] Calculate 3 byte ECC code 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, u_char *ecc_code)
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{
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u_char idx, reg1, reg2, reg3;
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int j;
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/* Initialize variables */
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reg1 = reg2 = reg3 = 0;
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ecc_code[0] = ecc_code[1] = ecc_code[2] = 0;
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/* Build up column parity */
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for(j = 0; j < 256; j++) {
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/* Get CP0 - CP5 from table */
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idx = nand_ecc_precalc_table[dat[j]];
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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 ^= (u_char) j;
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reg2 ^= ~((u_char) j);
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}
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}
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/* Create non-inverted ECC code from line parity */
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nand_trans_result(reg2, reg3, ecc_code);
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/* Calculate final ECC code */
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ecc_code[0] = ~ecc_code[0];
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ecc_code[1] = ~ecc_code[1];
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ecc_code[2] = ((~reg1) << 2) | 0x03;
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return 0;
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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, u_char *read_ecc, u_char *calc_ecc)
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{
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u_char a, b, c, d1, d2, d3, add, bit, i;
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/* Do error detection */
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d1 = calc_ecc[0] ^ read_ecc[0];
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d2 = calc_ecc[1] ^ read_ecc[1];
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d3 = calc_ecc[2] ^ read_ecc[2];
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if ((d1 | d2 | d3) == 0) {
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/* No errors */
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return 0;
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}
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else {
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a = (d1 ^ (d1 >> 1)) & 0x55;
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b = (d2 ^ (d2 >> 1)) & 0x55;
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c = (d3 ^ (d3 >> 1)) & 0x54;
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/* Found and will correct single bit error in the data */
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if ((a == 0x55) && (b == 0x55) && (c == 0x54)) {
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c = 0x80;
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add = 0;
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a = 0x80;
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for (i=0; i<4; i++) {
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if (d1 & c)
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add |= a;
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c >>= 2;
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a >>= 1;
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}
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c = 0x80;
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for (i=0; i<4; i++) {
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if (d2 & c)
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add |= a;
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c >>= 2;
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a >>= 1;
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}
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bit = 0;
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b = 0x04;
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c = 0x80;
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for (i=0; i<3; i++) {
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if (d3 & c)
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bit |= b;
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c >>= 2;
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b >>= 1;
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}
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b = 0x01;
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a = dat[add];
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a ^= (b << bit);
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dat[add] = a;
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return 1;
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}
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else {
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i = 0;
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while (d1) {
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if (d1 & 0x01)
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++i;
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d1 >>= 1;
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}
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while (d2) {
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if (d2 & 0x01)
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++i;
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d2 >>= 1;
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}
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while (d3) {
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if (d3 & 0x01)
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++i;
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d3 >>= 1;
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}
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if (i == 1) {
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/* ECC Code Error Correction */
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read_ecc[0] = calc_ecc[0];
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read_ecc[1] = calc_ecc[1];
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read_ecc[2] = calc_ecc[2];
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return 2;
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}
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else {
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/* Uncorrectable Error */
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return -1;
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}
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}
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}
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/* Should never happen */
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return -1;
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}
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EXPORT_SYMBOL(nand_calculate_ecc);
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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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