/*
* 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");
