diff options
Diffstat (limited to 'drivers/mtd/nand/raw/nand_bch.c')
| -rw-r--r-- | drivers/mtd/nand/raw/nand_bch.c | 234 |
1 files changed, 234 insertions, 0 deletions
diff --git a/drivers/mtd/nand/raw/nand_bch.c b/drivers/mtd/nand/raw/nand_bch.c new file mode 100644 index 000000000..b7387ace5 --- /dev/null +++ b/drivers/mtd/nand/raw/nand_bch.c @@ -0,0 +1,234 @@ +/* + * 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/rawnand.h> +#include <linux/mtd/nand_bch.h> +#include <linux/bch.h> + +/** + * struct nand_bch_control - private NAND BCH control structure + * @bch: BCH control structure + * @errloc: error location array + * @eccmask: XOR ecc mask, allows erased pages to be decoded as valid + */ +struct nand_bch_control { + struct bch_control *bch; + 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) { + pr_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 + * + * 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) +{ + struct nand_chip *nand = mtd_to_nand(mtd); + unsigned int m, t, eccsteps, i; + struct nand_bch_control *nbc = NULL; + unsigned char *erased_page; + unsigned int eccsize = nand->ecc.size; + unsigned int eccbytes = nand->ecc.bytes; + unsigned int eccstrength = nand->ecc.strength; + + if (!eccbytes && eccstrength) { + eccbytes = DIV_ROUND_UP(eccstrength * fls(8 * eccsize), 8); + nand->ecc.bytes = eccbytes; + } + + if (!eccsize || !eccbytes) { + pr_warn("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) { + pr_warn("invalid eccbytes %u, should be %u\n", + eccbytes, nbc->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; + } + + /* + * ecc->steps and ecc->total might be used by mtd->ooblayout->ecc(), + * which is called by mtd_ooblayout_count_eccbytes(). + * Make sure they are properly initialized before calling + * mtd_ooblayout_count_eccbytes(). + * FIXME: we should probably rework the sequencing in nand_scan_tail() + * to avoid setting those fields twice. + */ + nand->ecc.steps = eccsteps; + nand->ecc.total = eccsteps * eccbytes; + if (mtd_ooblayout_count_eccbytes(mtd) != (eccsteps*eccbytes)) { + pr_warn("invalid ecc layout\n"); + goto fail; + } + + nbc->eccmask = kmalloc(eccbytes, GFP_KERNEL); + nbc->errloc = kmalloc_array(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; + + if (!eccstrength) + nand->ecc.strength = (eccbytes * 8) / fls(8 * eccsize); + + 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"); |