drivers/mtd/nand/nand_ecc.c - kernel/common - 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 ([email protected])
  *                         Toshiba America Electronics Components, Inc.
  *
  * $Id: nand_ecc.c,v 1.14 2004/06/16 15:34:37 gleixner Exp $
  *
  * 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_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
  * @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)
 {
 	u_char idx, reg1, reg2, reg3;
 	int j;

 	/* 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++) {

 		/* Get CP0 - CP5 from table */
 		idx = nand_ecc_precalc_table[dat[j]];
 		reg1 ^= (idx & 0x3f);

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

 	/* Create non-inverted ECC code from line parity */
 	nand_trans_result(reg2, reg3, ecc_code);

 	/* Calculate final ECC code */
 	ecc_code[0] = ~ecc_code[0];
 	ecc_code[1] = ~ecc_code[1];
 	ecc_code[2] = ((~reg1) << 2) | 0x03;
 	return 0;
 }

 /**
  * 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)
 {
 	u_char a, b, c, d1, d2, d3, add, bit, i;

 	/* Do error detection */
 	d1 = calc_ecc[0] ^ read_ecc[0];
 	d2 = calc_ecc[1] ^ read_ecc[1];
 	d3 = calc_ecc[2] ^ read_ecc[2];

 	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;
 			}
 		}
 	}

 	/* Should never happen */
 	return -1;
 }

 EXPORT_SYMBOL(nand_calculate_ecc);
 EXPORT_SYMBOL(nand_correct_data);

 MODULE_LICENSE("GPL");
 MODULE_AUTHOR("Steven J. Hill <[email protected]>");
 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 ([email protected])
	* Toshiba America Electronics Components, Inc.
	*
	* $Id: nand_ecc.c,v 1.14 2004/06/16 15:34:37 gleixner Exp $
	*
	* 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_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
	* @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)
	{
	u_char idx, reg1, reg2, reg3;
	int j;

	/* 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++) {

	/* Get CP0 - CP5 from table */
	idx = nand_ecc_precalc_table[dat[j]];
	reg1 ^= (idx & 0x3f);

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

	/* Create non-inverted ECC code from line parity */
	nand_trans_result(reg2, reg3, ecc_code);

	/* Calculate final ECC code */
	ecc_code[0] = ~ecc_code[0];
	ecc_code[1] = ~ecc_code[1];
	ecc_code[2] = ((~reg1) << 2) \| 0x03;
	return 0;
	}

	/**
	* 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)
	{
	u_char a, b, c, d1, d2, d3, add, bit, i;

	/* Do error detection */
	d1 = calc_ecc[0] ^ read_ecc[0];
	d2 = calc_ecc[1] ^ read_ecc[1];
	d3 = calc_ecc[2] ^ read_ecc[2];

	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;
	}
	}
	}

	/* Should never happen */
	return -1;
	}

	EXPORT_SYMBOL(nand_calculate_ecc);
	EXPORT_SYMBOL(nand_correct_data);

	MODULE_LICENSE("GPL");
	MODULE_AUTHOR("Steven J. Hill <[email protected]>");
	MODULE_DESCRIPTION("Generic NAND ECC support");