LXR linux/drivers/mtd/nand/raw/nand

   1// SPDX-License-Identifier: GPL-2.0-or-later
   2/*
   3 * This file provides ECC correction for more than 1 bit per block of data,
   4 * using binary BCH codes. It relies on the generic BCH library lib/bch.c.
   5 *
   6 * Copyright © 2011 Ivan Djelic <ivan.djelic@parrot.com>
   7 */
   8
   9#include <linux/types.h>
  10#include <linux/kernel.h>
  11#include <linux/module.h>
  12#include <linux/slab.h>
  13#include <linux/bitops.h>
  14#include <linux/mtd/mtd.h>
  15#include <linux/mtd/rawnand.h>
  16#include <linux/mtd/nand_bch.h>
  17#include <linux/bch.h>
  18
  19/**
  20 * struct nand_bch_control - private NAND BCH control structure
  21 * @bch:       BCH control structure
  22 * @errloc:    error location array
  23 * @eccmask:   XOR ecc mask, allows erased pages to be decoded as valid
  24 */
  25struct nand_bch_control {
  26        struct bch_control   *bch;
  27        unsigned int         *errloc;
  28        unsigned char        *eccmask;
  29};
  30
  31/**
  32 * nand_bch_calculate_ecc - [NAND Interface] Calculate ECC for data block
  33 * @chip:       NAND chip object
  34 * @buf:        input buffer with raw data
  35 * @code:       output buffer with ECC
  36 */
  37int nand_bch_calculate_ecc(struct nand_chip *chip, const unsigned char *buf,
  38                           unsigned char *code)
  39{
  40        struct nand_bch_control *nbc = chip->ecc.priv;
  41        unsigned int i;
  42
  43        memset(code, 0, chip->ecc.bytes);
  44        encode_bch(nbc->bch, buf, chip->ecc.size, code);
  45
  46        /* apply mask so that an erased page is a valid codeword */
  47        for (i = 0; i < chip->ecc.bytes; i++)
  48                code[i] ^= nbc->eccmask[i];
  49
  50        return 0;
  51}
  52EXPORT_SYMBOL(nand_bch_calculate_ecc);
  53
  54/**
  55 * nand_bch_correct_data - [NAND Interface] Detect and correct bit error(s)
  56 * @chip:       NAND chip object
  57 * @buf:        raw data read from the chip
  58 * @read_ecc:   ECC from the chip
  59 * @calc_ecc:   the ECC calculated from raw data
  60 *
  61 * Detect and correct bit errors for a data byte block
  62 */
  63int nand_bch_correct_data(struct nand_chip *chip, unsigned char *buf,
  64                          unsigned char *read_ecc, unsigned char *calc_ecc)
  65{
  66        struct nand_bch_control *nbc = chip->ecc.priv;
  67        unsigned int *errloc = nbc->errloc;
  68        int i, count;
  69
  70        count = decode_bch(nbc->bch, NULL, chip->ecc.size, read_ecc, calc_ecc,
  71                           NULL, errloc);
  72        if (count > 0) {
  73                for (i = 0; i < count; i++) {
  74                        if (errloc[i] < (chip->ecc.size*8))
  75                                /* error is located in data, correct it */
  76                                buf[errloc[i] >> 3] ^= (1 << (errloc[i] & 7));
  77                        /* else error in ecc, no action needed */
  78
  79                        pr_debug("%s: corrected bitflip %u\n", __func__,
  80                                        errloc[i]);
  81                }
  82        } else if (count < 0) {
  83                pr_err("ecc unrecoverable error\n");
  84                count = -EBADMSG;
  85        }
  86        return count;
  87}
  88EXPORT_SYMBOL(nand_bch_correct_data);
  89
  90/**
  91 * nand_bch_init - [NAND Interface] Initialize NAND BCH error correction
  92 * @mtd:        MTD block structure
  93 *
  94 * Returns:
  95 *  a pointer to a new NAND BCH control structure, or NULL upon failure
  96 *
  97 * Initialize NAND BCH error correction. Parameters @eccsize and @eccbytes
  98 * are used to compute BCH parameters m (Galois field order) and t (error
  99 * correction capability). @eccbytes should be equal to the number of bytes
 100 * required to store m*t bits, where m is such that 2^m-1 > @eccsize*8.
 101 *
 102 * Example: to configure 4 bit correction per 512 bytes, you should pass
 103 * @eccsize = 512  (thus, m=13 is the smallest integer such that 2^m-1 > 512*8)
 104 * @eccbytes = 7   (7 bytes are required to store m*t = 13*4 = 52 bits)
 105 */
 106struct nand_bch_control *nand_bch_init(struct mtd_info *mtd)
 107{
 108        struct nand_chip *nand = mtd_to_nand(mtd);
 109        unsigned int m, t, eccsteps, i;
 110        struct nand_bch_control *nbc = NULL;
 111        unsigned char *erased_page;
 112        unsigned int eccsize = nand->ecc.size;
 113        unsigned int eccbytes = nand->ecc.bytes;
 114        unsigned int eccstrength = nand->ecc.strength;
 115
 116        if (!eccbytes && eccstrength) {
 117                eccbytes = DIV_ROUND_UP(eccstrength * fls(8 * eccsize), 8);
 118                nand->ecc.bytes = eccbytes;
 119        }
 120
 121        if (!eccsize || !eccbytes) {
 122                pr_warn("ecc parameters not supplied\n");
 123                goto fail;
 124        }
 125
 126        m = fls(1+8*eccsize);
 127        t = (eccbytes*8)/m;
 128
 129        nbc = kzalloc(sizeof(*nbc), GFP_KERNEL);
 130        if (!nbc)
 131                goto fail;
 132
 133        nbc->bch = init_bch(m, t, 0);
 134        if (!nbc->bch)
 135                goto fail;
 136
 137        /* verify that eccbytes has the expected value */
 138        if (nbc->bch->ecc_bytes != eccbytes) {
 139                pr_warn("invalid eccbytes %u, should be %u\n",
 140                        eccbytes, nbc->bch->ecc_bytes);
 141                goto fail;
 142        }
 143
 144        eccsteps = mtd->writesize/eccsize;
 145
 146        /* Check that we have an oob layout description. */
 147        if (!mtd->ooblayout) {
 148                pr_warn("missing oob scheme");
 149                goto fail;
 150        }
 151
 152        /* sanity checks */
 153        if (8*(eccsize+eccbytes) >= (1 << m)) {
 154                pr_warn("eccsize %u is too large\n", eccsize);
 155                goto fail;
 156        }
 157
 158        /*
 159         * ecc->steps and ecc->total might be used by mtd->ooblayout->ecc(),
 160         * which is called by mtd_ooblayout_count_eccbytes().
 161         * Make sure they are properly initialized before calling
 162         * mtd_ooblayout_count_eccbytes().
 163         * FIXME: we should probably rework the sequencing in nand_scan_tail()
 164         * to avoid setting those fields twice.
 165         */
 166        nand->ecc.steps = eccsteps;
 167        nand->ecc.total = eccsteps * eccbytes;
 168        if (mtd_ooblayout_count_eccbytes(mtd) != (eccsteps*eccbytes)) {
 169                pr_warn("invalid ecc layout\n");
 170                goto fail;
 171        }
 172
 173        nbc->eccmask = kzalloc(eccbytes, GFP_KERNEL);
 174        nbc->errloc = kmalloc_array(t, sizeof(*nbc->errloc), GFP_KERNEL);
 175        if (!nbc->eccmask || !nbc->errloc)
 176                goto fail;
 177        /*
 178         * compute and store the inverted ecc of an erased ecc block
 179         */
 180        erased_page = kmalloc(eccsize, GFP_KERNEL);
 181        if (!erased_page)
 182                goto fail;
 183
 184        memset(erased_page, 0xff, eccsize);
 185        encode_bch(nbc->bch, erased_page, eccsize, nbc->eccmask);
 186        kfree(erased_page);
 187
 188        for (i = 0; i < eccbytes; i++)
 189                nbc->eccmask[i] ^= 0xff;
 190
 191        if (!eccstrength)
 192                nand->ecc.strength = (eccbytes * 8) / fls(8 * eccsize);
 193
 194        return nbc;
 195fail:
 196        nand_bch_free(nbc);
 197        return NULL;
 198}
 199EXPORT_SYMBOL(nand_bch_init);
 200
 201/**
 202 * nand_bch_free - [NAND Interface] Release NAND BCH ECC resources
 203 * @nbc:        NAND BCH control structure
 204 */
 205void nand_bch_free(struct nand_bch_control *nbc)
 206{
 207        if (nbc) {
 208                free_bch(nbc->bch);
 209                kfree(nbc->errloc);
 210                kfree(nbc->eccmask);
 211                kfree(nbc);
 212        }
 213}
 214EXPORT_SYMBOL(nand_bch_free);
 215
 216MODULE_LICENSE("GPL");
 217MODULE_AUTHOR("Ivan Djelic <ivan.djelic@parrot.com>");
 218MODULE_DESCRIPTION("NAND software BCH ECC support");
 219