linux/drivers/mtd/nand/ecc-sw-bch.c
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   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/nand.h>
  15#include <linux/mtd/nand-ecc-sw-bch.h>
  16
  17/**
  18 * nand_ecc_sw_bch_calculate - Calculate the ECC corresponding to a data block
  19 * @nand: NAND device
  20 * @buf: Input buffer with raw data
  21 * @code: Output buffer with ECC
  22 */
  23int nand_ecc_sw_bch_calculate(struct nand_device *nand,
  24                              const unsigned char *buf, unsigned char *code)
  25{
  26        struct nand_ecc_sw_bch_conf *engine_conf = nand->ecc.ctx.priv;
  27        unsigned int i;
  28
  29        memset(code, 0, engine_conf->code_size);
  30        bch_encode(engine_conf->bch, buf, nand->ecc.ctx.conf.step_size, code);
  31
  32        /* apply mask so that an erased page is a valid codeword */
  33        for (i = 0; i < engine_conf->code_size; i++)
  34                code[i] ^= engine_conf->eccmask[i];
  35
  36        return 0;
  37}
  38EXPORT_SYMBOL(nand_ecc_sw_bch_calculate);
  39
  40/**
  41 * nand_ecc_sw_bch_correct - Detect, correct and report bit error(s)
  42 * @nand: NAND device
  43 * @buf: Raw data read from the chip
  44 * @read_ecc: ECC bytes from the chip
  45 * @calc_ecc: ECC calculated from the raw data
  46 *
  47 * Detect and correct bit errors for a data block.
  48 */
  49int nand_ecc_sw_bch_correct(struct nand_device *nand, unsigned char *buf,
  50                            unsigned char *read_ecc, unsigned char *calc_ecc)
  51{
  52        struct nand_ecc_sw_bch_conf *engine_conf = nand->ecc.ctx.priv;
  53        unsigned int step_size = nand->ecc.ctx.conf.step_size;
  54        unsigned int *errloc = engine_conf->errloc;
  55        int i, count;
  56
  57        count = bch_decode(engine_conf->bch, NULL, step_size, read_ecc,
  58                           calc_ecc, NULL, errloc);
  59        if (count > 0) {
  60                for (i = 0; i < count; i++) {
  61                        if (errloc[i] < (step_size * 8))
  62                                /* The error is in the data area: correct it */
  63                                buf[errloc[i] >> 3] ^= (1 << (errloc[i] & 7));
  64
  65                        /* Otherwise the error is in the ECC area: nothing to do */
  66                        pr_debug("%s: corrected bitflip %u\n", __func__,
  67                                 errloc[i]);
  68                }
  69        } else if (count < 0) {
  70                pr_err("ECC unrecoverable error\n");
  71                count = -EBADMSG;
  72        }
  73
  74        return count;
  75}
  76EXPORT_SYMBOL(nand_ecc_sw_bch_correct);
  77
  78/**
  79 * nand_ecc_sw_bch_cleanup - Cleanup software BCH ECC resources
  80 * @nand: NAND device
  81 */
  82static void nand_ecc_sw_bch_cleanup(struct nand_device *nand)
  83{
  84        struct nand_ecc_sw_bch_conf *engine_conf = nand->ecc.ctx.priv;
  85
  86        bch_free(engine_conf->bch);
  87        kfree(engine_conf->errloc);
  88        kfree(engine_conf->eccmask);
  89}
  90
  91/**
  92 * nand_ecc_sw_bch_init - Initialize software BCH ECC engine
  93 * @nand: NAND device
  94 *
  95 * Returns: a pointer to a new NAND BCH control structure, or NULL upon failure
  96 *
  97 * Initialize NAND BCH error correction. @nand.ecc parameters 'step_size' and
  98 * 'bytes' are used to compute the following BCH parameters:
  99 *     m, the Galois field order
 100 *     t, the error correction capability
 101 * 'bytes' should be equal to the number of bytes required to store m * t
 102 * bits, where m is such that 2^m - 1 > step_size * 8.
 103 *
 104 * Example: to configure 4 bit correction per 512 bytes, you should pass
 105 * step_size = 512 (thus, m = 13 is the smallest integer such that 2^m - 1 > 512 * 8)
 106 * bytes = 7 (7 bytes are required to store m * t = 13 * 4 = 52 bits)
 107 */
 108static int nand_ecc_sw_bch_init(struct nand_device *nand)
 109{
 110        struct nand_ecc_sw_bch_conf *engine_conf = nand->ecc.ctx.priv;
 111        unsigned int eccsize = nand->ecc.ctx.conf.step_size;
 112        unsigned int eccbytes = engine_conf->code_size;
 113        unsigned int m, t, i;
 114        unsigned char *erased_page;
 115        int ret;
 116
 117        m = fls(1 + (8 * eccsize));
 118        t = (eccbytes * 8) / m;
 119
 120        engine_conf->bch = bch_init(m, t, 0, false);
 121        if (!engine_conf->bch)
 122                return -EINVAL;
 123
 124        engine_conf->eccmask = kzalloc(eccbytes, GFP_KERNEL);
 125        engine_conf->errloc = kmalloc_array(t, sizeof(*engine_conf->errloc),
 126                                            GFP_KERNEL);
 127        if (!engine_conf->eccmask || !engine_conf->errloc) {
 128                ret = -ENOMEM;
 129                goto cleanup;
 130        }
 131
 132        /* Compute and store the inverted ECC of an erased step */
 133        erased_page = kmalloc(eccsize, GFP_KERNEL);
 134        if (!erased_page) {
 135                ret = -ENOMEM;
 136                goto cleanup;
 137        }
 138
 139        memset(erased_page, 0xff, eccsize);
 140        bch_encode(engine_conf->bch, erased_page, eccsize,
 141                   engine_conf->eccmask);
 142        kfree(erased_page);
 143
 144        for (i = 0; i < eccbytes; i++)
 145                engine_conf->eccmask[i] ^= 0xff;
 146
 147        /* Verify that the number of code bytes has the expected value */
 148        if (engine_conf->bch->ecc_bytes != eccbytes) {
 149                pr_err("Invalid number of ECC bytes: %u, expected: %u\n",
 150                       eccbytes, engine_conf->bch->ecc_bytes);
 151                ret = -EINVAL;
 152                goto cleanup;
 153        }
 154
 155        /* Sanity checks */
 156        if (8 * (eccsize + eccbytes) >= (1 << m)) {
 157                pr_err("ECC step size is too large (%u)\n", eccsize);
 158                ret = -EINVAL;
 159                goto cleanup;
 160        }
 161
 162        return 0;
 163
 164cleanup:
 165        nand_ecc_sw_bch_cleanup(nand);
 166
 167        return ret;
 168}
 169
 170int nand_ecc_sw_bch_init_ctx(struct nand_device *nand)
 171{
 172        struct nand_ecc_props *conf = &nand->ecc.ctx.conf;
 173        struct mtd_info *mtd = nanddev_to_mtd(nand);
 174        struct nand_ecc_sw_bch_conf *engine_conf;
 175        unsigned int code_size = 0, nsteps;
 176        int ret;
 177
 178        /* Only large page NAND chips may use BCH */
 179        if (mtd->oobsize < 64) {
 180                pr_err("BCH cannot be used with small page NAND chips\n");
 181                return -EINVAL;
 182        }
 183
 184        if (!mtd->ooblayout)
 185                mtd_set_ooblayout(mtd, nand_get_large_page_ooblayout());
 186
 187        conf->engine_type = NAND_ECC_ENGINE_TYPE_SOFT;
 188        conf->algo = NAND_ECC_ALGO_BCH;
 189        conf->step_size = nand->ecc.user_conf.step_size;
 190        conf->strength = nand->ecc.user_conf.strength;
 191
 192        /*
 193         * Board driver should supply ECC size and ECC strength
 194         * values to select how many bits are correctable.
 195         * Otherwise, default to 512 bytes for large page devices and 256 for
 196         * small page devices.
 197         */
 198        if (!conf->step_size) {
 199                if (mtd->oobsize >= 64)
 200                        conf->step_size = 512;
 201                else
 202                        conf->step_size = 256;
 203
 204                conf->strength = 4;
 205        }
 206
 207        nsteps = mtd->writesize / conf->step_size;
 208
 209        /* Maximize */
 210        if (nand->ecc.user_conf.flags & NAND_ECC_MAXIMIZE_STRENGTH) {
 211                conf->step_size = 1024;
 212                nsteps = mtd->writesize / conf->step_size;
 213                /* Reserve 2 bytes for the BBM */
 214                code_size = (mtd->oobsize - 2) / nsteps;
 215                conf->strength = code_size * 8 / fls(8 * conf->step_size);
 216        }
 217
 218        if (!code_size)
 219                code_size = DIV_ROUND_UP(conf->strength *
 220                                         fls(8 * conf->step_size), 8);
 221
 222        if (!conf->strength)
 223                conf->strength = (code_size * 8) / fls(8 * conf->step_size);
 224
 225        if (!code_size && !conf->strength) {
 226                pr_err("Missing ECC parameters\n");
 227                return -EINVAL;
 228        }
 229
 230        engine_conf = kzalloc(sizeof(*engine_conf), GFP_KERNEL);
 231        if (!engine_conf)
 232                return -ENOMEM;
 233
 234        ret = nand_ecc_init_req_tweaking(&engine_conf->req_ctx, nand);
 235        if (ret)
 236                goto free_engine_conf;
 237
 238        engine_conf->code_size = code_size;
 239        engine_conf->calc_buf = kzalloc(mtd->oobsize, GFP_KERNEL);
 240        engine_conf->code_buf = kzalloc(mtd->oobsize, GFP_KERNEL);
 241        if (!engine_conf->calc_buf || !engine_conf->code_buf) {
 242                ret = -ENOMEM;
 243                goto free_bufs;
 244        }
 245
 246        nand->ecc.ctx.priv = engine_conf;
 247        nand->ecc.ctx.nsteps = nsteps;
 248        nand->ecc.ctx.total = nsteps * code_size;
 249
 250        ret = nand_ecc_sw_bch_init(nand);
 251        if (ret)
 252                goto free_bufs;
 253
 254        /* Verify the layout validity */
 255        if (mtd_ooblayout_count_eccbytes(mtd) !=
 256            nand->ecc.ctx.nsteps * engine_conf->code_size) {
 257                pr_err("Invalid ECC layout\n");
 258                ret = -EINVAL;
 259                goto cleanup_bch_ctx;
 260        }
 261
 262        return 0;
 263
 264cleanup_bch_ctx:
 265        nand_ecc_sw_bch_cleanup(nand);
 266free_bufs:
 267        nand_ecc_cleanup_req_tweaking(&engine_conf->req_ctx);
 268        kfree(engine_conf->calc_buf);
 269        kfree(engine_conf->code_buf);
 270free_engine_conf:
 271        kfree(engine_conf);
 272
 273        return ret;
 274}
 275EXPORT_SYMBOL(nand_ecc_sw_bch_init_ctx);
 276
 277void nand_ecc_sw_bch_cleanup_ctx(struct nand_device *nand)
 278{
 279        struct nand_ecc_sw_bch_conf *engine_conf = nand->ecc.ctx.priv;
 280
 281        if (engine_conf) {
 282                nand_ecc_sw_bch_cleanup(nand);
 283                nand_ecc_cleanup_req_tweaking(&engine_conf->req_ctx);
 284                kfree(engine_conf->calc_buf);
 285                kfree(engine_conf->code_buf);
 286                kfree(engine_conf);
 287        }
 288}
 289EXPORT_SYMBOL(nand_ecc_sw_bch_cleanup_ctx);
 290
 291static int nand_ecc_sw_bch_prepare_io_req(struct nand_device *nand,
 292                                          struct nand_page_io_req *req)
 293{
 294        struct nand_ecc_sw_bch_conf *engine_conf = nand->ecc.ctx.priv;
 295        struct mtd_info *mtd = nanddev_to_mtd(nand);
 296        int eccsize = nand->ecc.ctx.conf.step_size;
 297        int eccbytes = engine_conf->code_size;
 298        int eccsteps = nand->ecc.ctx.nsteps;
 299        int total = nand->ecc.ctx.total;
 300        u8 *ecccalc = engine_conf->calc_buf;
 301        const u8 *data;
 302        int i;
 303
 304        /* Nothing to do for a raw operation */
 305        if (req->mode == MTD_OPS_RAW)
 306                return 0;
 307
 308        /* This engine does not provide BBM/free OOB bytes protection */
 309        if (!req->datalen)
 310                return 0;
 311
 312        nand_ecc_tweak_req(&engine_conf->req_ctx, req);
 313
 314        /* No more preparation for page read */
 315        if (req->type == NAND_PAGE_READ)
 316                return 0;
 317
 318        /* Preparation for page write: derive the ECC bytes and place them */
 319        for (i = 0, data = req->databuf.out;
 320             eccsteps;
 321             eccsteps--, i += eccbytes, data += eccsize)
 322                nand_ecc_sw_bch_calculate(nand, data, &ecccalc[i]);
 323
 324        return mtd_ooblayout_set_eccbytes(mtd, ecccalc, (void *)req->oobbuf.out,
 325                                          0, total);
 326}
 327
 328static int nand_ecc_sw_bch_finish_io_req(struct nand_device *nand,
 329                                         struct nand_page_io_req *req)
 330{
 331        struct nand_ecc_sw_bch_conf *engine_conf = nand->ecc.ctx.priv;
 332        struct mtd_info *mtd = nanddev_to_mtd(nand);
 333        int eccsize = nand->ecc.ctx.conf.step_size;
 334        int total = nand->ecc.ctx.total;
 335        int eccbytes = engine_conf->code_size;
 336        int eccsteps = nand->ecc.ctx.nsteps;
 337        u8 *ecccalc = engine_conf->calc_buf;
 338        u8 *ecccode = engine_conf->code_buf;
 339        unsigned int max_bitflips = 0;
 340        u8 *data = req->databuf.in;
 341        int i, ret;
 342
 343        /* Nothing to do for a raw operation */
 344        if (req->mode == MTD_OPS_RAW)
 345                return 0;
 346
 347        /* This engine does not provide BBM/free OOB bytes protection */
 348        if (!req->datalen)
 349                return 0;
 350
 351        /* No more preparation for page write */
 352        if (req->type == NAND_PAGE_WRITE) {
 353                nand_ecc_restore_req(&engine_conf->req_ctx, req);
 354                return 0;
 355        }
 356
 357        /* Finish a page read: retrieve the (raw) ECC bytes*/
 358        ret = mtd_ooblayout_get_eccbytes(mtd, ecccode, req->oobbuf.in, 0,
 359                                         total);
 360        if (ret)
 361                return ret;
 362
 363        /* Calculate the ECC bytes */
 364        for (i = 0; eccsteps; eccsteps--, i += eccbytes, data += eccsize)
 365                nand_ecc_sw_bch_calculate(nand, data, &ecccalc[i]);
 366
 367        /* Finish a page read: compare and correct */
 368        for (eccsteps = nand->ecc.ctx.nsteps, i = 0, data = req->databuf.in;
 369             eccsteps;
 370             eccsteps--, i += eccbytes, data += eccsize) {
 371                int stat =  nand_ecc_sw_bch_correct(nand, data,
 372                                                    &ecccode[i],
 373                                                    &ecccalc[i]);
 374                if (stat < 0) {
 375                        mtd->ecc_stats.failed++;
 376                } else {
 377                        mtd->ecc_stats.corrected += stat;
 378                        max_bitflips = max_t(unsigned int, max_bitflips, stat);
 379                }
 380        }
 381
 382        nand_ecc_restore_req(&engine_conf->req_ctx, req);
 383
 384        return max_bitflips;
 385}
 386
 387static struct nand_ecc_engine_ops nand_ecc_sw_bch_engine_ops = {
 388        .init_ctx = nand_ecc_sw_bch_init_ctx,
 389        .cleanup_ctx = nand_ecc_sw_bch_cleanup_ctx,
 390        .prepare_io_req = nand_ecc_sw_bch_prepare_io_req,
 391        .finish_io_req = nand_ecc_sw_bch_finish_io_req,
 392};
 393
 394static struct nand_ecc_engine nand_ecc_sw_bch_engine = {
 395        .ops = &nand_ecc_sw_bch_engine_ops,
 396};
 397
 398struct nand_ecc_engine *nand_ecc_sw_bch_get_engine(void)
 399{
 400        return &nand_ecc_sw_bch_engine;
 401}
 402EXPORT_SYMBOL(nand_ecc_sw_bch_get_engine);
 403
 404MODULE_LICENSE("GPL");
 405MODULE_AUTHOR("Ivan Djelic <ivan.djelic@parrot.com>");
 406MODULE_DESCRIPTION("NAND software BCH ECC support");
 407
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