summaryrefslogtreecommitdiff
path: root/drivers/mtd/nand/ecc-sw-bch.c
blob: 0a0ac11d5725a545c5d36396b41c2007646bfcaa (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
// SPDX-License-Identifier: GPL-2.0-or-later
/*
 * This file provides ECC correction for more than 1 bit per block of data,
 * using binary BCH codes. It relies on the generic BCH library lib/bch.c.
 *
 * Copyright © 2011 Ivan Djelic <ivan.djelic@parrot.com>
 */

#include <linux/types.h>
#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/slab.h>
#include <linux/bitops.h>
#include <linux/mtd/nand.h>
#include <linux/mtd/nand-ecc-sw-bch.h>

/**
 * nand_ecc_sw_bch_calculate - Calculate the ECC corresponding to a data block
 * @nand: NAND device
 * @buf: Input buffer with raw data
 * @code: Output buffer with ECC
 */
int nand_ecc_sw_bch_calculate(struct nand_device *nand,
			      const unsigned char *buf, unsigned char *code)
{
	struct nand_ecc_sw_bch_conf *engine_conf = nand->ecc.ctx.priv;
	unsigned int i;

	memset(code, 0, engine_conf->code_size);
	bch_encode(engine_conf->bch, buf, nand->ecc.ctx.conf.step_size, code);

	/* apply mask so that an erased page is a valid codeword */
	for (i = 0; i < engine_conf->code_size; i++)
		code[i] ^= engine_conf->eccmask[i];

	return 0;
}
EXPORT_SYMBOL(nand_ecc_sw_bch_calculate);

/**
 * nand_ecc_sw_bch_correct - Detect, correct and report bit error(s)
 * @nand: NAND device
 * @buf: Raw data read from the chip
 * @read_ecc: ECC bytes from the chip
 * @calc_ecc: ECC calculated from the raw data
 *
 * Detect and correct bit errors for a data block.
 */
int nand_ecc_sw_bch_correct(struct nand_device *nand, unsigned char *buf,
			    unsigned char *read_ecc, unsigned char *calc_ecc)
{
	struct nand_ecc_sw_bch_conf *engine_conf = nand->ecc.ctx.priv;
	unsigned int step_size = nand->ecc.ctx.conf.step_size;
	unsigned int *errloc = engine_conf->errloc;
	int i, count;

	count = bch_decode(engine_conf->bch, NULL, step_size, read_ecc,
			   calc_ecc, NULL, errloc);
	if (count > 0) {
		for (i = 0; i < count; i++) {
			if (errloc[i] < (step_size * 8))
				/* The error is in the data area: correct it */
				buf[errloc[i] >> 3] ^= (1 << (errloc[i] & 7));

			/* Otherwise the error is in the ECC area: nothing to do */
			pr_debug("%s: corrected bitflip %u\n", __func__,
				 errloc[i]);
		}
	} else if (count < 0) {
		pr_err("ECC unrecoverable error\n");
		count = -EBADMSG;
	}

	return count;
}
EXPORT_SYMBOL(nand_ecc_sw_bch_correct);

/**
 * nand_ecc_sw_bch_cleanup - Cleanup software BCH ECC resources
 * @nand: NAND device
 */
static void nand_ecc_sw_bch_cleanup(struct nand_device *nand)
{
	struct nand_ecc_sw_bch_conf *engine_conf = nand->ecc.ctx.priv;

	bch_free(engine_conf->bch);
	kfree(engine_conf->errloc);
	kfree(engine_conf->eccmask);
}

/**
 * nand_ecc_sw_bch_init - Initialize software BCH ECC engine
 * @nand: NAND device
 *
 * Returns: a pointer to a new NAND BCH control structure, or NULL upon failure
 *
 * Initialize NAND BCH error correction. @nand.ecc parameters 'step_size' and
 * 'bytes' are used to compute the following BCH parameters:
 *     m, the Galois field order
 *     t, the error correction capability
 * 'bytes' should be equal to the number of bytes required to store m * t
 * bits, where m is such that 2^m - 1 > step_size * 8.
 *
 * Example: to configure 4 bit correction per 512 bytes, you should pass
 * step_size = 512 (thus, m = 13 is the smallest integer such that 2^m - 1 > 512 * 8)
 * bytes = 7 (7 bytes are required to store m * t = 13 * 4 = 52 bits)
 */
static int nand_ecc_sw_bch_init(struct nand_device *nand)
{
	struct nand_ecc_sw_bch_conf *engine_conf = nand->ecc.ctx.priv;
	unsigned int eccsize = nand->ecc.ctx.conf.step_size;
	unsigned int eccbytes = engine_conf->code_size;
	unsigned int m, t, i;
	unsigned char *erased_page;
	int ret;

	m = fls(1 + (8 * eccsize));
	t = (eccbytes * 8) / m;

	engine_conf->bch = bch_init(m, t, 0, false);
	if (!engine_conf->bch)
		return -EINVAL;

	engine_conf->eccmask = kzalloc(eccbytes, GFP_KERNEL);
	engine_conf->errloc = kmalloc_array(t, sizeof(*engine_conf->errloc),
					    GFP_KERNEL);
	if (!engine_conf->eccmask || !engine_conf->errloc) {
		ret = -ENOMEM;
		goto cleanup;
	}

	/* Compute and store the inverted ECC of an erased step */
	erased_page = kmalloc(eccsize, GFP_KERNEL);
	if (!erased_page) {
		ret = -ENOMEM;
		goto cleanup;
	}

	memset(erased_page, 0xff, eccsize);
	bch_encode(engine_conf->bch, erased_page, eccsize,
		   engine_conf->eccmask);
	kfree(erased_page);

	for (i = 0; i < eccbytes; i++)
		engine_conf->eccmask[i] ^= 0xff;

	/* Verify that the number of code bytes has the expected value */
	if (engine_conf->bch->ecc_bytes != eccbytes) {
		pr_err("Invalid number of ECC bytes: %u, expected: %u\n",
		       eccbytes, engine_conf->bch->ecc_bytes);
		ret = -EINVAL;
		goto cleanup;
	}

	/* Sanity checks */
	if (8 * (eccsize + eccbytes) >= (1 << m)) {
		pr_err("ECC step size is too large (%u)\n", eccsize);
		ret = -EINVAL;
		goto cleanup;
	}

	return 0;

cleanup:
	nand_ecc_sw_bch_cleanup(nand);

	return ret;
}

int nand_ecc_sw_bch_init_ctx(struct nand_device *nand)
{
	struct nand_ecc_props *conf = &nand->ecc.ctx.conf;
	struct mtd_info *mtd = nanddev_to_mtd(nand);
	struct nand_ecc_sw_bch_conf *engine_conf;
	unsigned int code_size = 0, nsteps;
	int ret;

	/* Only large page NAND chips may use BCH */
	if (mtd->oobsize < 64) {
		pr_err("BCH cannot be used with small page NAND chips\n");
		return -EINVAL;
	}

	if (!mtd->ooblayout)
		mtd_set_ooblayout(mtd, nand_get_large_page_ooblayout());

	conf->engine_type = NAND_ECC_ENGINE_TYPE_SOFT;
	conf->algo = NAND_ECC_ALGO_BCH;
	conf->step_size = nand->ecc.user_conf.step_size;
	conf->strength = nand->ecc.user_conf.strength;

	/*
	 * Board driver should supply ECC size and ECC strength
	 * values to select how many bits are correctable.
	 * Otherwise, default to 512 bytes for large page devices and 256 for
	 * small page devices.
	 */
	if (!conf->step_size) {
		if (mtd->oobsize >= 64)
			conf->step_size = 512;
		else
			conf->step_size = 256;

		conf->strength = 4;
	}

	nsteps = mtd->writesize / conf->step_size;

	/* Maximize */
	if (nand->ecc.user_conf.flags & NAND_ECC_MAXIMIZE_STRENGTH) {
		conf->step_size = 1024;
		nsteps = mtd->writesize / conf->step_size;
		/* Reserve 2 bytes for the BBM */
		code_size = (mtd->oobsize - 2) / nsteps;
		conf->strength = code_size * 8 / fls(8 * conf->step_size);
	}

	if (!code_size)
		code_size = DIV_ROUND_UP(conf->strength *
					 fls(8 * conf->step_size), 8);

	if (!conf->strength)
		conf->strength = (code_size * 8) / fls(8 * conf->step_size);

	if (!code_size && !conf->strength) {
		pr_err("Missing ECC parameters\n");
		return -EINVAL;
	}

	engine_conf = kzalloc(sizeof(*engine_conf), GFP_KERNEL);
	if (!engine_conf)
		return -ENOMEM;

	ret = nand_ecc_init_req_tweaking(&engine_conf->req_ctx, nand);
	if (ret)
		goto free_engine_conf;

	engine_conf->code_size = code_size;
	engine_conf->nsteps = nsteps;
	engine_conf->calc_buf = kzalloc(mtd->oobsize, GFP_KERNEL);
	engine_conf->code_buf = kzalloc(mtd->oobsize, GFP_KERNEL);
	if (!engine_conf->calc_buf || !engine_conf->code_buf) {
		ret = -ENOMEM;
		goto free_bufs;
	}

	nand->ecc.ctx.priv = engine_conf;
	nand->ecc.ctx.total = nsteps * code_size;

	ret = nand_ecc_sw_bch_init(nand);
	if (ret)
		goto free_bufs;

	/* Verify the layout validity */
	if (mtd_ooblayout_count_eccbytes(mtd) !=
	    engine_conf->nsteps * engine_conf->code_size) {
		pr_err("Invalid ECC layout\n");
		ret = -EINVAL;
		goto cleanup_bch_ctx;
	}

	return 0;

cleanup_bch_ctx:
	nand_ecc_sw_bch_cleanup(nand);
free_bufs:
	nand_ecc_cleanup_req_tweaking(&engine_conf->req_ctx);
	kfree(engine_conf->calc_buf);
	kfree(engine_conf->code_buf);
free_engine_conf:
	kfree(engine_conf);

	return ret;
}
EXPORT_SYMBOL(nand_ecc_sw_bch_init_ctx);

void nand_ecc_sw_bch_cleanup_ctx(struct nand_device *nand)
{
	struct nand_ecc_sw_bch_conf *engine_conf = nand->ecc.ctx.priv;

	if (engine_conf) {
		nand_ecc_sw_bch_cleanup(nand);
		nand_ecc_cleanup_req_tweaking(&engine_conf->req_ctx);
		kfree(engine_conf->calc_buf);
		kfree(engine_conf->code_buf);
		kfree(engine_conf);
	}
}
EXPORT_SYMBOL(nand_ecc_sw_bch_cleanup_ctx);

static int nand_ecc_sw_bch_prepare_io_req(struct nand_device *nand,
					  struct nand_page_io_req *req)
{
	struct nand_ecc_sw_bch_conf *engine_conf = nand->ecc.ctx.priv;
	struct mtd_info *mtd = nanddev_to_mtd(nand);
	int eccsize = nand->ecc.ctx.conf.step_size;
	int eccbytes = engine_conf->code_size;
	int eccsteps = engine_conf->nsteps;
	int total = nand->ecc.ctx.total;
	u8 *ecccalc = engine_conf->calc_buf;
	const u8 *data;
	int i;

	/* Nothing to do for a raw operation */
	if (req->mode == MTD_OPS_RAW)
		return 0;

	/* This engine does not provide BBM/free OOB bytes protection */
	if (!req->datalen)
		return 0;

	nand_ecc_tweak_req(&engine_conf->req_ctx, req);

	/* No more preparation for page read */
	if (req->type == NAND_PAGE_READ)
		return 0;

	/* Preparation for page write: derive the ECC bytes and place them */
	for (i = 0, data = req->databuf.out;
	     eccsteps;
	     eccsteps--, i += eccbytes, data += eccsize)
		nand_ecc_sw_bch_calculate(nand, data, &ecccalc[i]);

	return mtd_ooblayout_set_eccbytes(mtd, ecccalc, (void *)req->oobbuf.out,
					  0, total);
}

static int nand_ecc_sw_bch_finish_io_req(struct nand_device *nand,
					 struct nand_page_io_req *req)
{
	struct nand_ecc_sw_bch_conf *engine_conf = nand->ecc.ctx.priv;
	struct mtd_info *mtd = nanddev_to_mtd(nand);
	int eccsize = nand->ecc.ctx.conf.step_size;
	int total = nand->ecc.ctx.total;
	int eccbytes = engine_conf->code_size;
	int eccsteps = engine_conf->nsteps;
	u8 *ecccalc = engine_conf->calc_buf;
	u8 *ecccode = engine_conf->code_buf;
	unsigned int max_bitflips = 0;
	u8 *data = req->databuf.in;
	int i, ret;

	/* Nothing to do for a raw operation */
	if (req->mode == MTD_OPS_RAW)
		return 0;

	/* This engine does not provide BBM/free OOB bytes protection */
	if (!req->datalen)
		return 0;

	/* No more preparation for page write */
	if (req->type == NAND_PAGE_WRITE) {
		nand_ecc_restore_req(&engine_conf->req_ctx, req);
		return 0;
	}

	/* Finish a page read: retrieve the (raw) ECC bytes*/
	ret = mtd_ooblayout_get_eccbytes(mtd, ecccode, req->oobbuf.in, 0,
					 total);
	if (ret)
		return ret;

	/* Calculate the ECC bytes */
	for (i = 0; eccsteps; eccsteps--, i += eccbytes, data += eccsize)
		nand_ecc_sw_bch_calculate(nand, data, &ecccalc[i]);

	/* Finish a page read: compare and correct */
	for (eccsteps = engine_conf->nsteps, i = 0, data = req->databuf.in;
	     eccsteps;
	     eccsteps--, i += eccbytes, data += eccsize) {
		int stat =  nand_ecc_sw_bch_correct(nand, data,
						    &ecccode[i],
						    &ecccalc[i]);
		if (stat < 0) {
			mtd->ecc_stats.failed++;
		} else {
			mtd->ecc_stats.corrected += stat;
			max_bitflips = max_t(unsigned int, max_bitflips, stat);
		}
	}

	nand_ecc_restore_req(&engine_conf->req_ctx, req);

	return max_bitflips;
}

static struct nand_ecc_engine_ops nand_ecc_sw_bch_engine_ops = {
	.init_ctx = nand_ecc_sw_bch_init_ctx,
	.cleanup_ctx = nand_ecc_sw_bch_cleanup_ctx,
	.prepare_io_req = nand_ecc_sw_bch_prepare_io_req,
	.finish_io_req = nand_ecc_sw_bch_finish_io_req,
};

static struct nand_ecc_engine nand_ecc_sw_bch_engine = {
	.ops = &nand_ecc_sw_bch_engine_ops,
};

struct nand_ecc_engine *nand_ecc_sw_bch_get_engine(void)
{
	return &nand_ecc_sw_bch_engine;
}
EXPORT_SYMBOL(nand_ecc_sw_bch_get_engine);

MODULE_LICENSE("GPL");
MODULE_AUTHOR("Ivan Djelic <ivan.djelic@parrot.com>");
MODULE_DESCRIPTION("NAND software BCH ECC support");