// 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 <[email protected]>
*/
#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_cleanup - Cleanup software BCH ECC resources
* @nand: NAND device
*/
static void nand_ecc_sw_bch_cleanup(struct nand_device *nand)
{
struct nand_ecc_sw_bch_conf *engine_conf = nand->ecc.ctx.priv;
bch_free(engine_conf->bch);
kfree(engine_conf->errloc);
kfree(engine_conf->eccmask);
}
/**
* 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)
*/
static int nand_ecc_sw_bch_init(struct nand_device *nand)
{
struct nand_ecc_sw_bch_conf *engine_conf = nand->ecc.ctx.priv;
unsigned int eccsize = nand->ecc.ctx.conf.step_size;
unsigned int eccbytes = engine_conf->code_size;
unsigned int m, t, i;
unsigned char *erased_page;
int ret;
m = fls(1 + (8 * eccsize));
t = (eccbytes * 8) / m;
engine_conf->bch = bch_init(m, t, 0, false);
if (!engine_conf->bch)
return -EINVAL;
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) {
ret = -ENOMEM;
goto cleanup;
}
/* Compute and store the inverted ECC of an erased step */
erased_page = kmalloc(eccsize, GFP_KERNEL);
if (!erased_page) {
ret = -ENOMEM;
goto cleanup;
}
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;
/* Verify that the number of code bytes has the expected value */
if (engine_conf->bch->ecc_bytes != eccbytes) {
pr_err("Invalid number of ECC bytes: %u, expected: %u\n",
eccbytes, engine_conf->bch->ecc_bytes);
ret = -EINVAL;
goto cleanup;
}
/* Sanity checks */
if (8 * (eccsize + eccbytes) >= (1 << m)) {
pr_err("ECC step size is too large (%u)\n", eccsize);
ret = -EINVAL;
goto cleanup;
}
return 0;
cleanup:
nand_ecc_sw_bch_cleanup(nand);
return ret;
}
int nand_ecc_sw_bch_init_ctx(struct nand_device *nand)
{
struct nand_ecc_props *conf = &nand->ecc.ctx.conf;
struct mtd_info *mtd = nanddev_to_mtd(nand);
struct nand_ecc_sw_bch_conf *engine_conf;
unsigned int code_size = 0, nsteps;
int ret;
/* Only large page NAND chips may use BCH */
if (mtd->oobsize < 64) {
pr_err("BCH cannot be used with small page NAND chips\n");
return -EINVAL;
}
if (!mtd->ooblayout)
mtd_set_ooblayout(mtd, nand_get_large_page_ooblayout());
conf->engine_type = NAND_ECC_ENGINE_TYPE_SOFT;
conf->algo = NAND_ECC_ALGO_BCH;
conf->step_size = nand->ecc.user_conf.step_size;
conf->strength = nand->ecc.user_conf.strength;
/*
* Board driver should supply ECC size and ECC strength
* values to select how many bits are correctable.
* Otherwise, default to 512 bytes for large page devices and 256 for
* small page devices.
*/
if (!conf->step_size) {
if (mtd->oobsize >= 64)
conf->step_size = 512;
else
conf->step_size = 256;
conf->strength = 4;
}
nsteps = mtd->writesize / conf->step_size;
/* Maximize */
if (nand->ecc.user_conf.flags & NAND_ECC_MAXIMIZE_STRENGTH) {
conf->step_size = 1024;
nsteps = mtd->writesize / conf->step_size;
/* Reserve 2 bytes for the BBM */
code_size = (mtd->oobsize - 2) / nsteps;
conf->strength = code_size * 8 / fls(8 * conf->step_size);
}
if (!code_size)
code_size = DIV_ROUND_UP(conf->strength *
fls(8 * conf->step_size), 8);
if (!conf->strength)
conf->strength = (code_size * 8) / fls(8 * conf->step_size);
if (!code_size && !conf->strength) {
pr_err("Missing ECC parameters\n");
return -EINVAL;
}
engine_conf = kzalloc(sizeof(*engine_conf), GFP_KERNEL);
if (!engine_conf)
return -ENOMEM;
ret = nand_ecc_init_req_tweaking(&engine_conf->req_ctx, nand);
if (ret)
goto free_engine_conf;
engine_conf->code_size = code_size;
engine_conf->calc_buf = kzalloc(mtd->oobsize, GFP_KERNEL);
engine_conf->code_buf = kzalloc(mtd->oobsize, GFP_KERNEL);
if (!engine_conf->calc_buf || !engine_conf->code_buf) {
ret = -ENOMEM;
goto free_bufs;
}
nand->ecc.ctx.priv = engine_conf;
nand->ecc.ctx.nsteps = nsteps;
nand->ecc.ctx.total = nsteps * code_size;
ret = nand_ecc_sw_bch_init(nand);
if (ret)
goto free_bufs;
/* Verify the layout validity */
if (mtd_ooblayout_count_eccbytes(mtd) !=
nand->ecc.ctx.nsteps * engine_conf->code_size) {
pr_err("Invalid ECC layout\n");
ret = -EINVAL;
goto cleanup_bch_ctx;
}
return 0;
cleanup_bch_ctx:
nand_ecc_sw_bch_cleanup(nand);
free_bufs:
nand_ecc_cleanup_req_tweaking(&engine_conf->req_ctx);
kfree(engine_conf->calc_buf);
kfree(engine_conf->code_buf);
free_engine_conf:
kfree(engine_conf);
return ret;
}
EXPORT_SYMBOL(nand_ecc_sw_bch_init_ctx);
void nand_ecc_sw_bch_cleanup_ctx(struct nand_device *nand)
{
struct nand_ecc_sw_bch_conf *engine_conf = nand->ecc.ctx.priv;
if (engine_conf) {
nand_ecc_sw_bch_cleanup(nand);
nand_ecc_cleanup_req_tweaking(&engine_conf->req_ctx);
kfree(engine_conf->calc_buf);
kfree(engine_conf->code_buf);
kfree(engine_conf);
}
}
EXPORT_SYMBOL(nand_ecc_sw_bch_cleanup_ctx);
static int nand_ecc_sw_bch_prepare_io_req(struct nand_device *nand,
struct nand_page_io_req *req)
{
struct nand_ecc_sw_bch_conf *engine_conf = nand->ecc.ctx.priv;
struct mtd_info *mtd = nanddev_to_mtd(nand);
int eccsize = nand->ecc.ctx.conf.step_size;
int eccbytes = engine_conf->code_size;
int eccsteps = nand->ecc.ctx.nsteps;
int total = nand->ecc.ctx.total;
u8 *ecccalc = engine_conf->calc_buf;
const u8 *data;
int i;
/* Nothing to do for a raw operation */
if (req->mode == MTD_OPS_RAW)
return 0;
/* This engine does not provide BBM/free OOB bytes protection */
if (!req->datalen)
return 0;
nand_ecc_tweak_req(&engine_conf->req_ctx, req);
/* No more preparation for page read */
if (req->type == NAND_PAGE_READ)
return 0;
/* Preparation for page write: derive the ECC bytes and place them */
for (i = 0, data = req->databuf.out;
eccsteps;
eccsteps--, i += eccbytes, data += eccsize)
nand_ecc_sw_bch_calculate(nand, data, &ecccalc[i]);
return mtd_ooblayout_set_eccbytes(mtd, ecccalc, (void *)req->oobbuf.out,
0, total);
}
static int nand_ecc_sw_bch_finish_io_req(struct nand_device *nand,
struct nand_page_io_req *req)
{
struct nand_ecc_sw_bch_conf *engine_conf = nand->ecc.ctx.priv;
struct mtd_info *mtd = nanddev_to_mtd(nand);
int eccsize = nand->ecc.ctx.conf.step_size;
int total = nand->ecc.ctx.total;
int eccbytes = engine_conf->code_size;
int eccsteps = nand->ecc.ctx.nsteps;
u8 *ecccalc = engine_conf->calc_buf;
u8 *ecccode = engine_conf->code_buf;
unsigned int max_bitflips = 0;
u8 *data = req->databuf.in;
int i, ret;
/* Nothing to do for a raw operation */
if (req->mode == MTD_OPS_RAW)
return 0;
/* This engine does not provide BBM/free OOB bytes protection */
if (!req->datalen)
return 0;
/* No more preparation for page write */
if (req->type == NAND_PAGE_WRITE) {
nand_ecc_restore_req(&engine_conf->req_ctx, req);
return 0;
}
/* Finish a page read: retrieve the (raw) ECC bytes*/
ret = mtd_ooblayout_get_eccbytes(mtd, ecccode, req->oobbuf.in, 0,
total);
if (ret)
return ret;
/* Calculate the ECC bytes */
for (i = 0; eccsteps; eccsteps--, i += eccbytes, data += eccsize)
nand_ecc_sw_bch_calculate(nand, data, &ecccalc[i]);
/* Finish a page read: compare and correct */
for (eccsteps = nand->ecc.ctx.nsteps, i = 0, data = req->databuf.in;
eccsteps;
eccsteps--, i += eccbytes, data += eccsize) {
int stat = nand_ecc_sw_bch_correct(nand, data,
&ecccode[i],
&ecccalc[i]);
if (stat < 0) {
mtd->ecc_stats.failed++;
} else {
mtd->ecc_stats.corrected += stat;
max_bitflips = max_t(unsigned int, max_bitflips, stat);
}
}
nand_ecc_restore_req(&engine_conf->req_ctx, req);
return max_bitflips;
}
static struct nand_ecc_engine_ops nand_ecc_sw_bch_engine_ops = {
.init_ctx = nand_ecc_sw_bch_init_ctx,
.cleanup_ctx = nand_ecc_sw_bch_cleanup_ctx,
.prepare_io_req = nand_ecc_sw_bch_prepare_io_req,
.finish_io_req = nand_ecc_sw_bch_finish_io_req,
};
static struct nand_ecc_engine nand_ecc_sw_bch_engine = {
.ops = &nand_ecc_sw_bch_engine_ops,
};
struct nand_ecc_engine *nand_ecc_sw_bch_get_engine(void)
{
return &nand_ecc_sw_bch_engine;
}
EXPORT_SYMBOL(nand_ecc_sw_bch_get_engine);
MODULE_LICENSE("GPL");
MODULE_AUTHOR("Ivan Djelic <[email protected]>");
MODULE_DESCRIPTION("NAND software BCH ECC support");
Codebase Browser
linux