drivers/mtd/nand/ecc-sw-bch.c

   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  */
  23 int 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 }
  38 EXPORT_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  */
  49 int 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 }
  76 EXPORT_SYMBOL(nand_ecc_sw_bch_correct);
  77
  78 /**
  79  * nand_ecc_sw_bch_cleanup - Cleanup software BCH ECC resources
  80  * @nand: NAND device
  81  */
  82 static 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  */
 108 static 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
 164 cleanup:
 165         nand_ecc_sw_bch_cleanup(nand);
 166
 167         return ret;
 168 }
 169
 170 int 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->nsteps = nsteps;
 240         engine_conf->calc_buf = kzalloc(mtd->oobsize, GFP_KERNEL);
 241         engine_conf->code_buf = kzalloc(mtd->oobsize, GFP_KERNEL);
 242         if (!engine_conf->calc_buf || !engine_conf->code_buf) {
 243                 ret = -ENOMEM;
 244                 goto free_bufs;
 245         }
 246
 247         nand->ecc.ctx.priv = engine_conf;
 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             engine_conf->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
 264 cleanup_bch_ctx:
 265         nand_ecc_sw_bch_cleanup(nand);
 266 free_bufs:
 267         nand_ecc_cleanup_req_tweaking(&engine_conf->req_ctx);
 268         kfree(engine_conf->calc_buf);
 269         kfree(engine_conf->code_buf);
 270 free_engine_conf:
 271         kfree(engine_conf);
 272
 273         return ret;
 274 }
 275 EXPORT_SYMBOL(nand_ecc_sw_bch_init_ctx);
 276
 277 void 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 }
 289 EXPORT_SYMBOL(nand_ecc_sw_bch_cleanup_ctx);
 290
 291 static 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 = engine_conf->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
 328 static 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 = engine_conf->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 = engine_conf->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
 387 static 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
 394 static struct nand_ecc_engine nand_ecc_sw_bch_engine = {
 395         .ops = &nand_ecc_sw_bch_engine_ops,
 396 };
 397
 398 struct nand_ecc_engine *nand_ecc_sw_bch_get_engine(void)
 399 {
 400         return &nand_ecc_sw_bch_engine;
 401 }
 402 EXPORT_SYMBOL(nand_ecc_sw_bch_get_engine);
 403
 404 MODULE_LICENSE("GPL");
 405 MODULE_AUTHOR("Ivan Djelic <ivan.djelic@parrot.com>");
 406 MODULE_DESCRIPTION("NAND software BCH ECC support");