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// SPDX-License-Identifier: GPL-2.0-or-later
/*
* 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>
*/
#include <linux/types.h>
#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/slab.h>
#include <linux/bitops.h>
#include <linux/mtd/nand.h>
#include <linux/mtd/nand-ecc-sw-bch.h>
/**
* nand_ecc_sw_bch_calculate - Calculate the ECC corresponding to a data block
* @nand: NAND device
* @buf: Input buffer with raw data
* @code: Output buffer with ECC
*/
int nand_ecc_sw_bch_calculate(struct nand_device *nand,
const unsigned char *buf, unsigned char *code)
{
struct nand_ecc_sw_bch_conf *engine_conf = nand->ecc.ctx.priv;
unsigned int i;
memset(code, 0, engine_conf->code_size);
bch_encode(engine_conf->bch, buf, nand->ecc.ctx.conf.step_size, code);
/* apply mask so that an erased page is a valid codeword */
for (i = 0; i < engine_conf->code_size; i++)
code[i] ^= engine_conf->eccmask[i];
return 0;
}
EXPORT_SYMBOL(nand_ecc_sw_bch_calculate);
/**
* nand_ecc_sw_bch_correct - Detect, correct and report bit error(s)
* @nand: NAND device
* @buf: Raw data read from the chip
* @read_ecc: ECC bytes from the chip
* @calc_ecc: ECC calculated from the raw data
*
* Detect and correct bit errors for a data block.
*/
int nand_ecc_sw_bch_correct(struct nand_device *nand, unsigned char *buf,
unsigned char *read_ecc, unsigned char *calc_ecc)
{
struct nand_ecc_sw_bch_conf *engine_conf = nand->ecc.ctx.priv;
unsigned int step_size = nand->ecc.ctx.conf.step_size;
unsigned int *errloc = engine_conf->errloc;
int i, count;
count = bch_decode(engine_conf->bch, NULL, step_size, read_ecc,
calc_ecc, NULL, errloc);
if (count > 0) {
for (i = 0; i < count; i++) {
if (errloc[i] < (step_size * 8))
/* The error is in the data area: correct it */
buf[errloc[i] >> 3] ^= (1 << (errloc[i] & 7));
/* Otherwise the error is in the ECC area: nothing to do */
pr_debug("%s: corrected bitflip %u\n", __func__,
errloc[i]);
}
} else if (count < 0) {
pr_err("ECC unrecoverable error\n");
count = -EBADMSG;
}
return count;
}
EXPORT_SYMBOL(nand_ecc_sw_bch_correct);
/**
* nand_ecc_sw_bch_init - Initialize software BCH ECC engine
* @nand: NAND device
*
* Returns: a pointer to a new NAND BCH control structure, or NULL upon failure
*
* Initialize NAND BCH error correction. @nand.ecc parameters 'step_size' and
* 'bytes' are used to compute the following BCH parameters:
* m, the Galois field order
* t, the error correction capability
* 'bytes' should be equal to the number of bytes required to store m * t
* bits, where m is such that 2^m - 1 > step_size * 8.
*
* Example: to configure 4 bit correction per 512 bytes, you should pass
* step_size = 512 (thus, m = 13 is the smallest integer such that 2^m - 1 > 512 * 8)
* bytes = 7 (7 bytes are required to store m * t = 13 * 4 = 52 bits)
*/
int nand_ecc_sw_bch_init(struct nand_device *nand)
{
struct mtd_info *mtd = nanddev_to_mtd(nand);
unsigned int m, t, eccsteps, i;
struct nand_ecc_sw_bch_conf *engine_conf = nand->ecc.ctx.priv;
unsigned char *erased_page;
unsigned int eccsize = nand->ecc.ctx.conf.step_size;
unsigned int eccbytes = engine_conf->code_size;
unsigned int eccstrength = nand->ecc.ctx.conf.strength;
if (!eccbytes && eccstrength) {
eccbytes = DIV_ROUND_UP(eccstrength * fls(8 * eccsize), 8);
engine_conf->code_size = eccbytes;
}
if (!eccsize || !eccbytes) {
pr_warn("ecc parameters not supplied\n");
return -EINVAL;
}
m = fls(1+8*eccsize);
t = (eccbytes*8)/m;
engine_conf->bch = bch_init(m, t, 0, false);
if (!engine_conf->bch)
return -EINVAL;
/* verify that eccbytes has the expected value */
if (engine_conf->bch->ecc_bytes != eccbytes) {
pr_warn("invalid eccbytes %u, should be %u\n",
eccbytes, engine_conf->bch->ecc_bytes);
goto fail;
}
eccsteps = mtd->writesize/eccsize;
/* Check that we have an oob layout description. */
if (!mtd->ooblayout) {
pr_warn("missing oob scheme");
goto fail;
}
/* sanity checks */
if (8*(eccsize+eccbytes) >= (1 << m)) {
pr_warn("eccsize %u is too large\n", eccsize);
goto fail;
}
if (mtd_ooblayout_count_eccbytes(mtd) != (eccsteps*eccbytes)) {
pr_warn("invalid ecc layout\n");
goto fail;
}
engine_conf->eccmask = kzalloc(eccbytes, GFP_KERNEL);
engine_conf->errloc = kmalloc_array(t, sizeof(*engine_conf->errloc),
GFP_KERNEL);
if (!engine_conf->eccmask || !engine_conf->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);
bch_encode(engine_conf->bch, erased_page, eccsize,
engine_conf->eccmask);
kfree(erased_page);
for (i = 0; i < eccbytes; i++)
engine_conf->eccmask[i] ^= 0xff;
if (!eccstrength)
nand->ecc.ctx.conf.strength = (eccbytes * 8) / fls(8 * eccsize);
return 0;
fail:
nand_ecc_sw_bch_cleanup(nand);
return -EINVAL;
}
EXPORT_SYMBOL(nand_ecc_sw_bch_init);
/**
* nand_ecc_sw_bch_cleanup - Cleanup software BCH ECC resources
* @nand: NAND device
*/
void nand_ecc_sw_bch_cleanup(struct nand_device *nand)
{
struct nand_ecc_sw_bch_conf *engine_conf = nand->ecc.ctx.priv;
if (engine_conf) {
bch_free(engine_conf->bch);
kfree(engine_conf->errloc);
kfree(engine_conf->eccmask);
}
}
EXPORT_SYMBOL(nand_ecc_sw_bch_cleanup);
MODULE_LICENSE("GPL");
MODULE_AUTHOR("Ivan Djelic <ivan.djelic@parrot.com>");
MODULE_DESCRIPTION("NAND software BCH ECC support");
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