535 lines
16 KiB
C
535 lines
16 KiB
C
/*
|
|
* This file contains an ECC algorithm that detects and corrects 1 bit
|
|
* errors in a 256 byte block of data.
|
|
*
|
|
* drivers/mtd/nand/nand_ecc.c
|
|
*
|
|
* Copyright © 2008 Koninklijke Philips Electronics NV.
|
|
* Author: Frans Meulenbroeks
|
|
*
|
|
* Completely replaces the previous ECC implementation which was written by:
|
|
* Steven J. Hill (sjhill@realitydiluted.com)
|
|
* Thomas Gleixner (tglx@linutronix.de)
|
|
*
|
|
* Information on how this algorithm works and how it was developed
|
|
* can be found in Documentation/mtd/nand_ecc.txt
|
|
*
|
|
* 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.
|
|
*
|
|
*/
|
|
|
|
/*
|
|
* The STANDALONE macro is useful when running the code outside the kernel
|
|
* e.g. when running the code in a testbed or a benchmark program.
|
|
* When STANDALONE is used, the module related macros are commented out
|
|
* as well as the linux include files.
|
|
* Instead a private definition of mtd_info is given to satisfy the compiler
|
|
* (the code does not use mtd_info, so the code does not care)
|
|
*/
|
|
#ifndef STANDALONE
|
|
#include <linux/types.h>
|
|
#include <linux/kernel.h>
|
|
#include <linux/module.h>
|
|
#include <linux/mtd/mtd.h>
|
|
#include <linux/mtd/nand.h>
|
|
#include <linux/mtd/nand_ecc.h>
|
|
#include <asm/byteorder.h>
|
|
#else
|
|
#include <stdint.h>
|
|
struct mtd_info;
|
|
#define EXPORT_SYMBOL(x) /* x */
|
|
|
|
#define MODULE_LICENSE(x) /* x */
|
|
#define MODULE_AUTHOR(x) /* x */
|
|
#define MODULE_DESCRIPTION(x) /* x */
|
|
|
|
#define printk printf
|
|
#define KERN_ERR ""
|
|
#endif
|
|
|
|
/*
|
|
* invparity is a 256 byte table that contains the odd parity
|
|
* for each byte. So if the number of bits in a byte is even,
|
|
* the array element is 1, and when the number of bits is odd
|
|
* the array eleemnt is 0.
|
|
*/
|
|
static const char invparity[256] = {
|
|
1, 0, 0, 1, 0, 1, 1, 0, 0, 1, 1, 0, 1, 0, 0, 1,
|
|
0, 1, 1, 0, 1, 0, 0, 1, 1, 0, 0, 1, 0, 1, 1, 0,
|
|
0, 1, 1, 0, 1, 0, 0, 1, 1, 0, 0, 1, 0, 1, 1, 0,
|
|
1, 0, 0, 1, 0, 1, 1, 0, 0, 1, 1, 0, 1, 0, 0, 1,
|
|
0, 1, 1, 0, 1, 0, 0, 1, 1, 0, 0, 1, 0, 1, 1, 0,
|
|
1, 0, 0, 1, 0, 1, 1, 0, 0, 1, 1, 0, 1, 0, 0, 1,
|
|
1, 0, 0, 1, 0, 1, 1, 0, 0, 1, 1, 0, 1, 0, 0, 1,
|
|
0, 1, 1, 0, 1, 0, 0, 1, 1, 0, 0, 1, 0, 1, 1, 0,
|
|
0, 1, 1, 0, 1, 0, 0, 1, 1, 0, 0, 1, 0, 1, 1, 0,
|
|
1, 0, 0, 1, 0, 1, 1, 0, 0, 1, 1, 0, 1, 0, 0, 1,
|
|
1, 0, 0, 1, 0, 1, 1, 0, 0, 1, 1, 0, 1, 0, 0, 1,
|
|
0, 1, 1, 0, 1, 0, 0, 1, 1, 0, 0, 1, 0, 1, 1, 0,
|
|
1, 0, 0, 1, 0, 1, 1, 0, 0, 1, 1, 0, 1, 0, 0, 1,
|
|
0, 1, 1, 0, 1, 0, 0, 1, 1, 0, 0, 1, 0, 1, 1, 0,
|
|
0, 1, 1, 0, 1, 0, 0, 1, 1, 0, 0, 1, 0, 1, 1, 0,
|
|
1, 0, 0, 1, 0, 1, 1, 0, 0, 1, 1, 0, 1, 0, 0, 1
|
|
};
|
|
|
|
/*
|
|
* bitsperbyte contains the number of bits per byte
|
|
* this is only used for testing and repairing parity
|
|
* (a precalculated value slightly improves performance)
|
|
*/
|
|
static const char bitsperbyte[256] = {
|
|
0, 1, 1, 2, 1, 2, 2, 3, 1, 2, 2, 3, 2, 3, 3, 4,
|
|
1, 2, 2, 3, 2, 3, 3, 4, 2, 3, 3, 4, 3, 4, 4, 5,
|
|
1, 2, 2, 3, 2, 3, 3, 4, 2, 3, 3, 4, 3, 4, 4, 5,
|
|
2, 3, 3, 4, 3, 4, 4, 5, 3, 4, 4, 5, 4, 5, 5, 6,
|
|
1, 2, 2, 3, 2, 3, 3, 4, 2, 3, 3, 4, 3, 4, 4, 5,
|
|
2, 3, 3, 4, 3, 4, 4, 5, 3, 4, 4, 5, 4, 5, 5, 6,
|
|
2, 3, 3, 4, 3, 4, 4, 5, 3, 4, 4, 5, 4, 5, 5, 6,
|
|
3, 4, 4, 5, 4, 5, 5, 6, 4, 5, 5, 6, 5, 6, 6, 7,
|
|
1, 2, 2, 3, 2, 3, 3, 4, 2, 3, 3, 4, 3, 4, 4, 5,
|
|
2, 3, 3, 4, 3, 4, 4, 5, 3, 4, 4, 5, 4, 5, 5, 6,
|
|
2, 3, 3, 4, 3, 4, 4, 5, 3, 4, 4, 5, 4, 5, 5, 6,
|
|
3, 4, 4, 5, 4, 5, 5, 6, 4, 5, 5, 6, 5, 6, 6, 7,
|
|
2, 3, 3, 4, 3, 4, 4, 5, 3, 4, 4, 5, 4, 5, 5, 6,
|
|
3, 4, 4, 5, 4, 5, 5, 6, 4, 5, 5, 6, 5, 6, 6, 7,
|
|
3, 4, 4, 5, 4, 5, 5, 6, 4, 5, 5, 6, 5, 6, 6, 7,
|
|
4, 5, 5, 6, 5, 6, 6, 7, 5, 6, 6, 7, 6, 7, 7, 8,
|
|
};
|
|
|
|
/*
|
|
* addressbits is a lookup table to filter out the bits from the xor-ed
|
|
* ECC data that identify the faulty location.
|
|
* this is only used for repairing parity
|
|
* see the comments in nand_correct_data for more details
|
|
*/
|
|
static const char addressbits[256] = {
|
|
0x00, 0x00, 0x01, 0x01, 0x00, 0x00, 0x01, 0x01,
|
|
0x02, 0x02, 0x03, 0x03, 0x02, 0x02, 0x03, 0x03,
|
|
0x00, 0x00, 0x01, 0x01, 0x00, 0x00, 0x01, 0x01,
|
|
0x02, 0x02, 0x03, 0x03, 0x02, 0x02, 0x03, 0x03,
|
|
0x04, 0x04, 0x05, 0x05, 0x04, 0x04, 0x05, 0x05,
|
|
0x06, 0x06, 0x07, 0x07, 0x06, 0x06, 0x07, 0x07,
|
|
0x04, 0x04, 0x05, 0x05, 0x04, 0x04, 0x05, 0x05,
|
|
0x06, 0x06, 0x07, 0x07, 0x06, 0x06, 0x07, 0x07,
|
|
0x00, 0x00, 0x01, 0x01, 0x00, 0x00, 0x01, 0x01,
|
|
0x02, 0x02, 0x03, 0x03, 0x02, 0x02, 0x03, 0x03,
|
|
0x00, 0x00, 0x01, 0x01, 0x00, 0x00, 0x01, 0x01,
|
|
0x02, 0x02, 0x03, 0x03, 0x02, 0x02, 0x03, 0x03,
|
|
0x04, 0x04, 0x05, 0x05, 0x04, 0x04, 0x05, 0x05,
|
|
0x06, 0x06, 0x07, 0x07, 0x06, 0x06, 0x07, 0x07,
|
|
0x04, 0x04, 0x05, 0x05, 0x04, 0x04, 0x05, 0x05,
|
|
0x06, 0x06, 0x07, 0x07, 0x06, 0x06, 0x07, 0x07,
|
|
0x08, 0x08, 0x09, 0x09, 0x08, 0x08, 0x09, 0x09,
|
|
0x0a, 0x0a, 0x0b, 0x0b, 0x0a, 0x0a, 0x0b, 0x0b,
|
|
0x08, 0x08, 0x09, 0x09, 0x08, 0x08, 0x09, 0x09,
|
|
0x0a, 0x0a, 0x0b, 0x0b, 0x0a, 0x0a, 0x0b, 0x0b,
|
|
0x0c, 0x0c, 0x0d, 0x0d, 0x0c, 0x0c, 0x0d, 0x0d,
|
|
0x0e, 0x0e, 0x0f, 0x0f, 0x0e, 0x0e, 0x0f, 0x0f,
|
|
0x0c, 0x0c, 0x0d, 0x0d, 0x0c, 0x0c, 0x0d, 0x0d,
|
|
0x0e, 0x0e, 0x0f, 0x0f, 0x0e, 0x0e, 0x0f, 0x0f,
|
|
0x08, 0x08, 0x09, 0x09, 0x08, 0x08, 0x09, 0x09,
|
|
0x0a, 0x0a, 0x0b, 0x0b, 0x0a, 0x0a, 0x0b, 0x0b,
|
|
0x08, 0x08, 0x09, 0x09, 0x08, 0x08, 0x09, 0x09,
|
|
0x0a, 0x0a, 0x0b, 0x0b, 0x0a, 0x0a, 0x0b, 0x0b,
|
|
0x0c, 0x0c, 0x0d, 0x0d, 0x0c, 0x0c, 0x0d, 0x0d,
|
|
0x0e, 0x0e, 0x0f, 0x0f, 0x0e, 0x0e, 0x0f, 0x0f,
|
|
0x0c, 0x0c, 0x0d, 0x0d, 0x0c, 0x0c, 0x0d, 0x0d,
|
|
0x0e, 0x0e, 0x0f, 0x0f, 0x0e, 0x0e, 0x0f, 0x0f
|
|
};
|
|
|
|
/**
|
|
* __nand_calculate_ecc - [NAND Interface] Calculate 3-byte ECC for 256/512-byte
|
|
* block
|
|
* @buf: input buffer with raw data
|
|
* @eccsize: data bytes per ECC step (256 or 512)
|
|
* @code: output buffer with ECC
|
|
*/
|
|
void __nand_calculate_ecc(const unsigned char *buf, unsigned int eccsize,
|
|
unsigned char *code)
|
|
{
|
|
int i;
|
|
const uint32_t *bp = (uint32_t *)buf;
|
|
/* 256 or 512 bytes/ecc */
|
|
const uint32_t eccsize_mult = eccsize >> 8;
|
|
uint32_t cur; /* current value in buffer */
|
|
/* rp0..rp15..rp17 are the various accumulated parities (per byte) */
|
|
uint32_t rp0, rp1, rp2, rp3, rp4, rp5, rp6, rp7;
|
|
uint32_t rp8, rp9, rp10, rp11, rp12, rp13, rp14, rp15, rp16;
|
|
uint32_t uninitialized_var(rp17); /* to make compiler happy */
|
|
uint32_t par; /* the cumulative parity for all data */
|
|
uint32_t tmppar; /* the cumulative parity for this iteration;
|
|
for rp12, rp14 and rp16 at the end of the
|
|
loop */
|
|
|
|
par = 0;
|
|
rp4 = 0;
|
|
rp6 = 0;
|
|
rp8 = 0;
|
|
rp10 = 0;
|
|
rp12 = 0;
|
|
rp14 = 0;
|
|
rp16 = 0;
|
|
|
|
/*
|
|
* The loop is unrolled a number of times;
|
|
* This avoids if statements to decide on which rp value to update
|
|
* Also we process the data by longwords.
|
|
* Note: passing unaligned data might give a performance penalty.
|
|
* It is assumed that the buffers are aligned.
|
|
* tmppar is the cumulative sum of this iteration.
|
|
* needed for calculating rp12, rp14, rp16 and par
|
|
* also used as a performance improvement for rp6, rp8 and rp10
|
|
*/
|
|
for (i = 0; i < eccsize_mult << 2; i++) {
|
|
cur = *bp++;
|
|
tmppar = cur;
|
|
rp4 ^= cur;
|
|
cur = *bp++;
|
|
tmppar ^= cur;
|
|
rp6 ^= tmppar;
|
|
cur = *bp++;
|
|
tmppar ^= cur;
|
|
rp4 ^= cur;
|
|
cur = *bp++;
|
|
tmppar ^= cur;
|
|
rp8 ^= tmppar;
|
|
|
|
cur = *bp++;
|
|
tmppar ^= cur;
|
|
rp4 ^= cur;
|
|
rp6 ^= cur;
|
|
cur = *bp++;
|
|
tmppar ^= cur;
|
|
rp6 ^= cur;
|
|
cur = *bp++;
|
|
tmppar ^= cur;
|
|
rp4 ^= cur;
|
|
cur = *bp++;
|
|
tmppar ^= cur;
|
|
rp10 ^= tmppar;
|
|
|
|
cur = *bp++;
|
|
tmppar ^= cur;
|
|
rp4 ^= cur;
|
|
rp6 ^= cur;
|
|
rp8 ^= cur;
|
|
cur = *bp++;
|
|
tmppar ^= cur;
|
|
rp6 ^= cur;
|
|
rp8 ^= cur;
|
|
cur = *bp++;
|
|
tmppar ^= cur;
|
|
rp4 ^= cur;
|
|
rp8 ^= cur;
|
|
cur = *bp++;
|
|
tmppar ^= cur;
|
|
rp8 ^= cur;
|
|
|
|
cur = *bp++;
|
|
tmppar ^= cur;
|
|
rp4 ^= cur;
|
|
rp6 ^= cur;
|
|
cur = *bp++;
|
|
tmppar ^= cur;
|
|
rp6 ^= cur;
|
|
cur = *bp++;
|
|
tmppar ^= cur;
|
|
rp4 ^= cur;
|
|
cur = *bp++;
|
|
tmppar ^= cur;
|
|
|
|
par ^= tmppar;
|
|
if ((i & 0x1) == 0)
|
|
rp12 ^= tmppar;
|
|
if ((i & 0x2) == 0)
|
|
rp14 ^= tmppar;
|
|
if (eccsize_mult == 2 && (i & 0x4) == 0)
|
|
rp16 ^= tmppar;
|
|
}
|
|
|
|
/*
|
|
* handle the fact that we use longword operations
|
|
* we'll bring rp4..rp14..rp16 back to single byte entities by
|
|
* shifting and xoring first fold the upper and lower 16 bits,
|
|
* then the upper and lower 8 bits.
|
|
*/
|
|
rp4 ^= (rp4 >> 16);
|
|
rp4 ^= (rp4 >> 8);
|
|
rp4 &= 0xff;
|
|
rp6 ^= (rp6 >> 16);
|
|
rp6 ^= (rp6 >> 8);
|
|
rp6 &= 0xff;
|
|
rp8 ^= (rp8 >> 16);
|
|
rp8 ^= (rp8 >> 8);
|
|
rp8 &= 0xff;
|
|
rp10 ^= (rp10 >> 16);
|
|
rp10 ^= (rp10 >> 8);
|
|
rp10 &= 0xff;
|
|
rp12 ^= (rp12 >> 16);
|
|
rp12 ^= (rp12 >> 8);
|
|
rp12 &= 0xff;
|
|
rp14 ^= (rp14 >> 16);
|
|
rp14 ^= (rp14 >> 8);
|
|
rp14 &= 0xff;
|
|
if (eccsize_mult == 2) {
|
|
rp16 ^= (rp16 >> 16);
|
|
rp16 ^= (rp16 >> 8);
|
|
rp16 &= 0xff;
|
|
}
|
|
|
|
/*
|
|
* we also need to calculate the row parity for rp0..rp3
|
|
* This is present in par, because par is now
|
|
* rp3 rp3 rp2 rp2 in little endian and
|
|
* rp2 rp2 rp3 rp3 in big endian
|
|
* as well as
|
|
* rp1 rp0 rp1 rp0 in little endian and
|
|
* rp0 rp1 rp0 rp1 in big endian
|
|
* First calculate rp2 and rp3
|
|
*/
|
|
#ifdef __BIG_ENDIAN
|
|
rp2 = (par >> 16);
|
|
rp2 ^= (rp2 >> 8);
|
|
rp2 &= 0xff;
|
|
rp3 = par & 0xffff;
|
|
rp3 ^= (rp3 >> 8);
|
|
rp3 &= 0xff;
|
|
#else
|
|
rp3 = (par >> 16);
|
|
rp3 ^= (rp3 >> 8);
|
|
rp3 &= 0xff;
|
|
rp2 = par & 0xffff;
|
|
rp2 ^= (rp2 >> 8);
|
|
rp2 &= 0xff;
|
|
#endif
|
|
|
|
/* reduce par to 16 bits then calculate rp1 and rp0 */
|
|
par ^= (par >> 16);
|
|
#ifdef __BIG_ENDIAN
|
|
rp0 = (par >> 8) & 0xff;
|
|
rp1 = (par & 0xff);
|
|
#else
|
|
rp1 = (par >> 8) & 0xff;
|
|
rp0 = (par & 0xff);
|
|
#endif
|
|
|
|
/* finally reduce par to 8 bits */
|
|
par ^= (par >> 8);
|
|
par &= 0xff;
|
|
|
|
/*
|
|
* and calculate rp5..rp15..rp17
|
|
* note that par = rp4 ^ rp5 and due to the commutative property
|
|
* of the ^ operator we can say:
|
|
* rp5 = (par ^ rp4);
|
|
* The & 0xff seems superfluous, but benchmarking learned that
|
|
* leaving it out gives slightly worse results. No idea why, probably
|
|
* it has to do with the way the pipeline in pentium is organized.
|
|
*/
|
|
rp5 = (par ^ rp4) & 0xff;
|
|
rp7 = (par ^ rp6) & 0xff;
|
|
rp9 = (par ^ rp8) & 0xff;
|
|
rp11 = (par ^ rp10) & 0xff;
|
|
rp13 = (par ^ rp12) & 0xff;
|
|
rp15 = (par ^ rp14) & 0xff;
|
|
if (eccsize_mult == 2)
|
|
rp17 = (par ^ rp16) & 0xff;
|
|
|
|
/*
|
|
* Finally calculate the ECC bits.
|
|
* Again here it might seem that there are performance optimisations
|
|
* possible, but benchmarks showed that on the system this is developed
|
|
* the code below is the fastest
|
|
*/
|
|
#ifdef CONFIG_MTD_NAND_ECC_SMC
|
|
code[0] =
|
|
(invparity[rp7] << 7) |
|
|
(invparity[rp6] << 6) |
|
|
(invparity[rp5] << 5) |
|
|
(invparity[rp4] << 4) |
|
|
(invparity[rp3] << 3) |
|
|
(invparity[rp2] << 2) |
|
|
(invparity[rp1] << 1) |
|
|
(invparity[rp0]);
|
|
code[1] =
|
|
(invparity[rp15] << 7) |
|
|
(invparity[rp14] << 6) |
|
|
(invparity[rp13] << 5) |
|
|
(invparity[rp12] << 4) |
|
|
(invparity[rp11] << 3) |
|
|
(invparity[rp10] << 2) |
|
|
(invparity[rp9] << 1) |
|
|
(invparity[rp8]);
|
|
#else
|
|
code[1] =
|
|
(invparity[rp7] << 7) |
|
|
(invparity[rp6] << 6) |
|
|
(invparity[rp5] << 5) |
|
|
(invparity[rp4] << 4) |
|
|
(invparity[rp3] << 3) |
|
|
(invparity[rp2] << 2) |
|
|
(invparity[rp1] << 1) |
|
|
(invparity[rp0]);
|
|
code[0] =
|
|
(invparity[rp15] << 7) |
|
|
(invparity[rp14] << 6) |
|
|
(invparity[rp13] << 5) |
|
|
(invparity[rp12] << 4) |
|
|
(invparity[rp11] << 3) |
|
|
(invparity[rp10] << 2) |
|
|
(invparity[rp9] << 1) |
|
|
(invparity[rp8]);
|
|
#endif
|
|
if (eccsize_mult == 1)
|
|
code[2] =
|
|
(invparity[par & 0xf0] << 7) |
|
|
(invparity[par & 0x0f] << 6) |
|
|
(invparity[par & 0xcc] << 5) |
|
|
(invparity[par & 0x33] << 4) |
|
|
(invparity[par & 0xaa] << 3) |
|
|
(invparity[par & 0x55] << 2) |
|
|
3;
|
|
else
|
|
code[2] =
|
|
(invparity[par & 0xf0] << 7) |
|
|
(invparity[par & 0x0f] << 6) |
|
|
(invparity[par & 0xcc] << 5) |
|
|
(invparity[par & 0x33] << 4) |
|
|
(invparity[par & 0xaa] << 3) |
|
|
(invparity[par & 0x55] << 2) |
|
|
(invparity[rp17] << 1) |
|
|
(invparity[rp16] << 0);
|
|
}
|
|
EXPORT_SYMBOL(__nand_calculate_ecc);
|
|
|
|
/**
|
|
* nand_calculate_ecc - [NAND Interface] Calculate 3-byte ECC for 256/512-byte
|
|
* block
|
|
* @mtd: MTD block structure
|
|
* @buf: input buffer with raw data
|
|
* @code: output buffer with ECC
|
|
*/
|
|
int nand_calculate_ecc(struct mtd_info *mtd, const unsigned char *buf,
|
|
unsigned char *code)
|
|
{
|
|
__nand_calculate_ecc(buf,
|
|
((struct nand_chip *)mtd->priv)->ecc.size, code);
|
|
|
|
return 0;
|
|
}
|
|
EXPORT_SYMBOL(nand_calculate_ecc);
|
|
|
|
/**
|
|
* __nand_correct_data - [NAND Interface] Detect and correct bit error(s)
|
|
* @buf: raw data read from the chip
|
|
* @read_ecc: ECC from the chip
|
|
* @calc_ecc: the ECC calculated from raw data
|
|
* @eccsize: data bytes per ECC step (256 or 512)
|
|
*
|
|
* Detect and correct a 1 bit error for eccsize byte block
|
|
*/
|
|
int __nand_correct_data(unsigned char *buf,
|
|
unsigned char *read_ecc, unsigned char *calc_ecc,
|
|
unsigned int eccsize)
|
|
{
|
|
unsigned char b0, b1, b2, bit_addr;
|
|
unsigned int byte_addr;
|
|
/* 256 or 512 bytes/ecc */
|
|
const uint32_t eccsize_mult = eccsize >> 8;
|
|
|
|
/*
|
|
* b0 to b2 indicate which bit is faulty (if any)
|
|
* we might need the xor result more than once,
|
|
* so keep them in a local var
|
|
*/
|
|
#ifdef CONFIG_MTD_NAND_ECC_SMC
|
|
b0 = read_ecc[0] ^ calc_ecc[0];
|
|
b1 = read_ecc[1] ^ calc_ecc[1];
|
|
#else
|
|
b0 = read_ecc[1] ^ calc_ecc[1];
|
|
b1 = read_ecc[0] ^ calc_ecc[0];
|
|
#endif
|
|
b2 = read_ecc[2] ^ calc_ecc[2];
|
|
|
|
/* check if there are any bitfaults */
|
|
|
|
/* repeated if statements are slightly more efficient than switch ... */
|
|
/* ordered in order of likelihood */
|
|
|
|
if ((b0 | b1 | b2) == 0)
|
|
return 0; /* no error */
|
|
|
|
if ((((b0 ^ (b0 >> 1)) & 0x55) == 0x55) &&
|
|
(((b1 ^ (b1 >> 1)) & 0x55) == 0x55) &&
|
|
((eccsize_mult == 1 && ((b2 ^ (b2 >> 1)) & 0x54) == 0x54) ||
|
|
(eccsize_mult == 2 && ((b2 ^ (b2 >> 1)) & 0x55) == 0x55))) {
|
|
/* single bit error */
|
|
/*
|
|
* rp17/rp15/13/11/9/7/5/3/1 indicate which byte is the faulty
|
|
* byte, cp 5/3/1 indicate the faulty bit.
|
|
* A lookup table (called addressbits) is used to filter
|
|
* the bits from the byte they are in.
|
|
* A marginal optimisation is possible by having three
|
|
* different lookup tables.
|
|
* One as we have now (for b0), one for b2
|
|
* (that would avoid the >> 1), and one for b1 (with all values
|
|
* << 4). However it was felt that introducing two more tables
|
|
* hardly justify the gain.
|
|
*
|
|
* The b2 shift is there to get rid of the lowest two bits.
|
|
* We could also do addressbits[b2] >> 1 but for the
|
|
* performance it does not make any difference
|
|
*/
|
|
if (eccsize_mult == 1)
|
|
byte_addr = (addressbits[b1] << 4) + addressbits[b0];
|
|
else
|
|
byte_addr = (addressbits[b2 & 0x3] << 8) +
|
|
(addressbits[b1] << 4) + addressbits[b0];
|
|
bit_addr = addressbits[b2 >> 2];
|
|
/* flip the bit */
|
|
buf[byte_addr] ^= (1 << bit_addr);
|
|
return 1;
|
|
|
|
}
|
|
/* count nr of bits; use table lookup, faster than calculating it */
|
|
if ((bitsperbyte[b0] + bitsperbyte[b1] + bitsperbyte[b2]) == 1)
|
|
return 1; /* error in ECC data; no action needed */
|
|
|
|
printk(KERN_ERR "uncorrectable error : ");
|
|
return -1;
|
|
}
|
|
EXPORT_SYMBOL(__nand_correct_data);
|
|
|
|
/**
|
|
* nand_correct_data - [NAND Interface] Detect and correct bit error(s)
|
|
* @mtd: MTD block structure
|
|
* @buf: 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 256/512 byte block
|
|
*/
|
|
int nand_correct_data(struct mtd_info *mtd, unsigned char *buf,
|
|
unsigned char *read_ecc, unsigned char *calc_ecc)
|
|
{
|
|
return __nand_correct_data(buf, read_ecc, calc_ecc,
|
|
((struct nand_chip *)mtd->priv)->ecc.size);
|
|
}
|
|
EXPORT_SYMBOL(nand_correct_data);
|
|
|
|
MODULE_LICENSE("GPL");
|
|
MODULE_AUTHOR("Frans Meulenbroeks <fransmeulenbroeks@gmail.com>");
|
|
MODULE_DESCRIPTION("Generic NAND ECC support");
|