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(bch: engine_conf->bch, data: buf, len: nand->ecc.ctx.conf.step_size, ecc: 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(bch: engine_conf->bch, NULL, len: step_size, recv_ecc: 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(bch: engine_conf->bch);
87 kfree(objp: engine_conf->errloc);
88 kfree(objp: 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(x: 1 + (8 * eccsize));
118 t = (eccbytes * 8) / m;
119
120 engine_conf->bch = bch_init(m, t, prim_poly: 0, swap_bits: false);
121 if (!engine_conf->bch)
122 return -EINVAL;
123
124 engine_conf->eccmask = kzalloc(size: eccbytes, GFP_KERNEL);
125 engine_conf->errloc = kmalloc_array(n: t, size: 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(size: eccsize, GFP_KERNEL);
134 if (!erased_page) {
135 ret = -ENOMEM;
136 goto cleanup;
137 }
138
139 memset(erased_page, 0xff, eccsize);
140 bch_encode(bch: engine_conf->bch, data: erased_page, len: eccsize,
141 ecc: engine_conf->eccmask);
142 kfree(objp: 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, ooblayout: 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(x: 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(x: 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(size: sizeof(*engine_conf), GFP_KERNEL);
231 if (!engine_conf)
232 return -ENOMEM;
233
234 ret = nand_ecc_init_req_tweaking(ctx: &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(size: mtd->oobsize, GFP_KERNEL);
240 engine_conf->code_buf = kzalloc(size: 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(ctx: &engine_conf->req_ctx);
268 kfree(objp: engine_conf->calc_buf);
269 kfree(objp: engine_conf->code_buf);
270free_engine_conf:
271 kfree(objp: 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(ctx: &engine_conf->req_ctx);
284 kfree(objp: engine_conf->calc_buf);
285 kfree(objp: engine_conf->code_buf);
286 kfree(objp: 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(ctx: &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, eccbuf: ecccalc, oobbuf: (void *)req->oobbuf.out,
325 start: 0, nbytes: 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(ctx: &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, eccbuf: ecccode, oobbuf: req->oobbuf.in, start: 0,
359 nbytes: 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(ctx: &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

source code of linux/drivers/mtd/nand/ecc-sw-bch.c