/* * 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 * * 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. * */ #include #include #include #include #include #include #include #include #include /** * 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->priv; 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->priv; 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 = -1; } 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->priv; unsigned int m, t, eccsteps, i; struct nand_ecclayout *layout = nand->ecc.layout; 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) { 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 (!layout) { /* 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; nand->ecc.layout = layout; } /* sanity checks */ if (8*(eccsize+eccbytes) >= (1 << m)) { printk(KERN_WARNING "eccsize %u is too large\n", eccsize); goto fail; } if (layout->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; 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 "); MODULE_DESCRIPTION("NAND software BCH ECC support");