drivers/mtd/nand/nand_ecc.c - kernel/panda - Git at Google

 /*
  * 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.
  *
  * Copyright (C) 2006 Thomas Gleixner <tglx@linutronix.de>
  *
  * 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_calculate_ecc - [NAND Interface] Calculate 3-byte ECC 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)
 {
 	uint8_t idx, reg1, reg2, reg3, tmp1, tmp2;
 	int i;

 	/* Initialize variables */
 	reg1 = reg2 = reg3 = 0;

 	/* Build up column parity */
 	for(i = 0; i < 256; i++) {
 		/* Get CP0 - CP5 from table */
 		idx = nand_ecc_precalc_table[*dat++];
 		reg1 ^= (idx & 0x3f);

 		/* All bit XOR = 1 ? */
 		if (idx & 0x40) {
 			reg3 ^= (uint8_t) i;
 			reg2 ^= ~((uint8_t) i);
 		}
 	}

 	/* Create non-inverted ECC code from line parity */
 	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 */
 #ifdef CONFIG_MTD_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)
  * @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)
 {
 	uint8_t s0, s1, s2;

 #ifdef CONFIG_MTD_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;

 	/* Check for a single bit error */
 	if( ((s0 ^ (s0 >> 1)) & 0x55) == 0x55 &&
 	    ((s1 ^ (s1 >> 1)) & 0x55) == 0x55 &&
 	    ((s2 ^ (s2 >> 1)) & 0x54) == 0x54) {

 		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;
 	}

 	if(countbits(s0 | ((uint32_t)s1 << 8) | ((uint32_t)s2 <<16)) == 1)
 		return 1;

 	return -EBADMSG;
 }
 EXPORT_SYMBOL(nand_correct_data);

 MODULE_LICENSE("GPL");
 MODULE_AUTHOR("Steven J. Hill <sjhill@realitydiluted.com>");
 MODULE_DESCRIPTION("Generic NAND ECC support");
	/*
	* 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.
	*
	* Copyright (C) 2006 Thomas Gleixner <tglx@linutronix.de>
	*
	* 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_calculate_ecc - [NAND Interface] Calculate 3-byte ECC 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)
	{
	uint8_t idx, reg1, reg2, reg3, tmp1, tmp2;
	int i;

	/* Initialize variables */
	reg1 = reg2 = reg3 = 0;

	/* Build up column parity */
	for(i = 0; i < 256; i++) {
	/* Get CP0 - CP5 from table */
	idx = nand_ecc_precalc_table[*dat++];
	reg1 ^= (idx & 0x3f);

	/* All bit XOR = 1 ? */
	if (idx & 0x40) {
	reg3 ^= (uint8_t) i;
	reg2 ^= ~((uint8_t) i);
	}
	}

	/* Create non-inverted ECC code from line parity */
	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 */
	#ifdef CONFIG_MTD_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)
	* @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)
	{
	uint8_t s0, s1, s2;

	#ifdef CONFIG_MTD_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;

	/* Check for a single bit error */
	if( ((s0 ^ (s0 >> 1)) & 0x55) == 0x55 &&
	((s1 ^ (s1 >> 1)) & 0x55) == 0x55 &&
	((s2 ^ (s2 >> 1)) & 0x54) == 0x54) {

	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;
	}

	if(countbits(s0 \| ((uint32_t)s1 << 8) \| ((uint32_t)s2 <<16)) == 1)
	return 1;

	return -EBADMSG;
	}
	EXPORT_SYMBOL(nand_correct_data);

	MODULE_LICENSE("GPL");
	MODULE_AUTHOR("Steven J. Hill <sjhill@realitydiluted.com>");
	MODULE_DESCRIPTION("Generic NAND ECC support");