244 lines
7.0 KiB
C
244 lines
7.0 KiB
C
/*
|
|
* This file provides ECC correction for more than 1 bit per block of data,
|
|
* using binary BCH codes. It relies on the generic BCH library lib/bch.c.
|
|
*
|
|
* Copyright © 2011 Ivan Djelic <ivan.djelic@parrot.com>
|
|
*
|
|
* 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.
|
|
*/
|
|
|
|
#include <linux/types.h>
|
|
#include <linux/kernel.h>
|
|
#include <linux/module.h>
|
|
#include <linux/slab.h>
|
|
#include <linux/bitops.h>
|
|
#include <linux/mtd/mtd.h>
|
|
#include <linux/mtd/nand.h>
|
|
#include <linux/mtd/nand_bch.h>
|
|
#include <linux/bch.h>
|
|
|
|
/**
|
|
* struct nand_bch_control - private NAND BCH control structure
|
|
* @bch: BCH control structure
|
|
* @ecclayout: private ecc layout for this BCH configuration
|
|
* @errloc: error location array
|
|
* @eccmask: XOR ecc mask, allows erased pages to be decoded as valid
|
|
*/
|
|
struct nand_bch_control {
|
|
struct bch_control *bch;
|
|
struct nand_ecclayout ecclayout;
|
|
unsigned int *errloc;
|
|
unsigned char *eccmask;
|
|
};
|
|
|
|
/**
|
|
* nand_bch_calculate_ecc - [NAND Interface] Calculate ECC for data block
|
|
* @mtd: MTD block structure
|
|
* @buf: input buffer with raw data
|
|
* @code: output buffer with ECC
|
|
*/
|
|
int nand_bch_calculate_ecc(struct mtd_info *mtd, const unsigned char *buf,
|
|
unsigned char *code)
|
|
{
|
|
const struct nand_chip *chip = mtd_to_nand(mtd);
|
|
struct nand_bch_control *nbc = chip->ecc.priv;
|
|
unsigned int i;
|
|
|
|
memset(code, 0, chip->ecc.bytes);
|
|
encode_bch(nbc->bch, buf, chip->ecc.size, code);
|
|
|
|
/* apply mask so that an erased page is a valid codeword */
|
|
for (i = 0; i < chip->ecc.bytes; i++)
|
|
code[i] ^= nbc->eccmask[i];
|
|
|
|
return 0;
|
|
}
|
|
EXPORT_SYMBOL(nand_bch_calculate_ecc);
|
|
|
|
/**
|
|
* nand_bch_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 bit errors for a data byte block
|
|
*/
|
|
int nand_bch_correct_data(struct mtd_info *mtd, unsigned char *buf,
|
|
unsigned char *read_ecc, unsigned char *calc_ecc)
|
|
{
|
|
const struct nand_chip *chip = mtd_to_nand(mtd);
|
|
struct nand_bch_control *nbc = chip->ecc.priv;
|
|
unsigned int *errloc = nbc->errloc;
|
|
int i, count;
|
|
|
|
count = decode_bch(nbc->bch, NULL, chip->ecc.size, read_ecc, calc_ecc,
|
|
NULL, errloc);
|
|
if (count > 0) {
|
|
for (i = 0; i < count; i++) {
|
|
if (errloc[i] < (chip->ecc.size*8))
|
|
/* error is located in data, correct it */
|
|
buf[errloc[i] >> 3] ^= (1 << (errloc[i] & 7));
|
|
/* else error in ecc, no action needed */
|
|
|
|
pr_debug("%s: corrected bitflip %u\n", __func__,
|
|
errloc[i]);
|
|
}
|
|
} else if (count < 0) {
|
|
printk(KERN_ERR "ecc unrecoverable error\n");
|
|
count = -EBADMSG;
|
|
}
|
|
return count;
|
|
}
|
|
EXPORT_SYMBOL(nand_bch_correct_data);
|
|
|
|
/**
|
|
* nand_bch_init - [NAND Interface] Initialize NAND BCH error correction
|
|
* @mtd: MTD block structure
|
|
* @eccsize: ecc block size in bytes
|
|
* @eccbytes: ecc length in bytes
|
|
* @ecclayout: output default layout
|
|
*
|
|
* Returns:
|
|
* a pointer to a new NAND BCH control structure, or NULL upon failure
|
|
*
|
|
* Initialize NAND BCH error correction. Parameters @eccsize and @eccbytes
|
|
* are used to compute BCH parameters m (Galois field order) and t (error
|
|
* correction capability). @eccbytes should be equal to the number of bytes
|
|
* required to store m*t bits, where m is such that 2^m-1 > @eccsize*8.
|
|
*
|
|
* Example: to configure 4 bit correction per 512 bytes, you should pass
|
|
* @eccsize = 512 (thus, m=13 is the smallest integer such that 2^m-1 > 512*8)
|
|
* @eccbytes = 7 (7 bytes are required to store m*t = 13*4 = 52 bits)
|
|
*/
|
|
struct nand_bch_control *
|
|
nand_bch_init(struct mtd_info *mtd, unsigned int eccsize, unsigned int eccbytes,
|
|
struct nand_ecclayout **ecclayout)
|
|
{
|
|
unsigned int m, t, eccsteps, i;
|
|
struct nand_ecclayout *layout;
|
|
struct nand_bch_control *nbc = NULL;
|
|
unsigned char *erased_page;
|
|
|
|
if (!eccsize || !eccbytes) {
|
|
printk(KERN_WARNING "ecc parameters not supplied\n");
|
|
goto fail;
|
|
}
|
|
|
|
m = fls(1+8*eccsize);
|
|
t = (eccbytes*8)/m;
|
|
|
|
nbc = kzalloc(sizeof(*nbc), GFP_KERNEL);
|
|
if (!nbc)
|
|
goto fail;
|
|
|
|
nbc->bch = init_bch(m, t, 0);
|
|
if (!nbc->bch)
|
|
goto fail;
|
|
|
|
/* verify that eccbytes has the expected value */
|
|
if (nbc->bch->ecc_bytes != eccbytes) {
|
|
printk(KERN_WARNING "invalid eccbytes %u, should be %u\n",
|
|
eccbytes, nbc->bch->ecc_bytes);
|
|
goto fail;
|
|
}
|
|
|
|
eccsteps = mtd->writesize/eccsize;
|
|
|
|
/* if no ecc placement scheme was provided, build one */
|
|
if (!*ecclayout) {
|
|
|
|
/* handle large page devices only */
|
|
if (mtd->oobsize < 64) {
|
|
printk(KERN_WARNING "must provide an oob scheme for "
|
|
"oobsize %d\n", mtd->oobsize);
|
|
goto fail;
|
|
}
|
|
|
|
layout = &nbc->ecclayout;
|
|
layout->eccbytes = eccsteps*eccbytes;
|
|
|
|
/* reserve 2 bytes for bad block marker */
|
|
if (layout->eccbytes+2 > mtd->oobsize) {
|
|
printk(KERN_WARNING "no suitable oob scheme available "
|
|
"for oobsize %d eccbytes %u\n", mtd->oobsize,
|
|
eccbytes);
|
|
goto fail;
|
|
}
|
|
/* put ecc bytes at oob tail */
|
|
for (i = 0; i < layout->eccbytes; i++)
|
|
layout->eccpos[i] = mtd->oobsize-layout->eccbytes+i;
|
|
|
|
layout->oobfree[0].offset = 2;
|
|
layout->oobfree[0].length = mtd->oobsize-2-layout->eccbytes;
|
|
|
|
*ecclayout = layout;
|
|
}
|
|
|
|
/* sanity checks */
|
|
if (8*(eccsize+eccbytes) >= (1 << m)) {
|
|
printk(KERN_WARNING "eccsize %u is too large\n", eccsize);
|
|
goto fail;
|
|
}
|
|
if ((*ecclayout)->eccbytes != (eccsteps*eccbytes)) {
|
|
printk(KERN_WARNING "invalid ecc layout\n");
|
|
goto fail;
|
|
}
|
|
|
|
nbc->eccmask = kmalloc(eccbytes, GFP_KERNEL);
|
|
nbc->errloc = kmalloc(t*sizeof(*nbc->errloc), GFP_KERNEL);
|
|
if (!nbc->eccmask || !nbc->errloc)
|
|
goto fail;
|
|
/*
|
|
* compute and store the inverted ecc of an erased ecc block
|
|
*/
|
|
erased_page = kmalloc(eccsize, GFP_KERNEL);
|
|
if (!erased_page)
|
|
goto fail;
|
|
|
|
memset(erased_page, 0xff, eccsize);
|
|
memset(nbc->eccmask, 0, eccbytes);
|
|
encode_bch(nbc->bch, erased_page, eccsize, nbc->eccmask);
|
|
kfree(erased_page);
|
|
|
|
for (i = 0; i < eccbytes; i++)
|
|
nbc->eccmask[i] ^= 0xff;
|
|
|
|
return nbc;
|
|
fail:
|
|
nand_bch_free(nbc);
|
|
return NULL;
|
|
}
|
|
EXPORT_SYMBOL(nand_bch_init);
|
|
|
|
/**
|
|
* nand_bch_free - [NAND Interface] Release NAND BCH ECC resources
|
|
* @nbc: NAND BCH control structure
|
|
*/
|
|
void nand_bch_free(struct nand_bch_control *nbc)
|
|
{
|
|
if (nbc) {
|
|
free_bch(nbc->bch);
|
|
kfree(nbc->errloc);
|
|
kfree(nbc->eccmask);
|
|
kfree(nbc);
|
|
}
|
|
}
|
|
EXPORT_SYMBOL(nand_bch_free);
|
|
|
|
MODULE_LICENSE("GPL");
|
|
MODULE_AUTHOR("Ivan Djelic <ivan.djelic@parrot.com>");
|
|
MODULE_DESCRIPTION("NAND software BCH ECC support");
|