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(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 | } |
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(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 | } |
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(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 | */ |
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(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 | |
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, 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 | |
264 | cleanup_bch_ctx: |
265 | nand_ecc_sw_bch_cleanup(nand); |
266 | free_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); |
270 | free_engine_conf: |
271 | kfree(objp: 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(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 | } |
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 = 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 | |
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 = 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 | |
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" ); |
407 | |