Nicolas Pitre nico at cam.org software ECC computation for NAND flash
git-svn-id: svn://svn.berlios.de/openocd/trunk@1445 b42882b7-edfa-0310-969c-e2dbd0fdcd60__archive__
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/*
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* This file contains an ECC algorithm from Toshiba that allows for detection
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* and correction of 1-bit errors in a 256 byte block of data.
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*
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* [ Extracted from the initial code found in some early Linux versions.
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* The current Linux code is bigger while being faster, but this is of
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* no real benefit when the bottleneck largely remains the JTAG link. ]
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*
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* Copyright (C) 2000-2004 Steven J. Hill (sjhill at 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 at linutronix.de>
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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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#ifdef HAVE_CONFIG_H
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#include "config.h"
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#endif
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#include "replacements.h"
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#include <inttypes.h>
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#include "nand.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 u8 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 - Calculate 3-byte ECC for 256-byte block
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*/
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int nand_calculate_ecc(struct nand_device_s *device, const u8 *dat, u8 *ecc_code)
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{
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u8 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 ^= (u8) i;
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reg2 ^= ~((u8) 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 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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