summaryrefslogtreecommitdiffstats
path: root/drivers/mtd/nand/ecc.c
blob: 5250764cedee155804eb18c44ea5e3d59625ff61 (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
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
552
553
554
555
556
557
558
559
560
561
562
563
564
565
566
567
568
569
570
571
572
573
574
575
576
577
578
579
580
581
582
583
584
585
586
587
588
589
590
591
592
593
594
595
596
597
598
599
600
601
602
603
604
605
606
607
608
609
610
611
612
613
614
615
616
617
618
619
620
621
622
623
624
625
626
627
628
629
630
631
632
633
634
635
636
637
638
639
640
641
642
643
644
645
646
647
648
649
650
651
652
653
654
655
656
657
658
659
660
661
662
663
664
665
666
667
668
669
670
671
672
673
674
675
676
677
678
679
680
681
682
683
684
685
686
687
688
689
690
691
692
693
694
695
696
697
698
699
700
701
702
703
704
705
706
707
708
709
710
711
712
713
714
715
716
717
718
719
720
721
722
723
724
725
726
727
728
729
730
731
732
733
734
735
// SPDX-License-Identifier: GPL-2.0+
/*
 * Generic Error-Correcting Code (ECC) engine
 *
 * Copyright (C) 2019 Macronix
 * Author:
 *     Miquèl RAYNAL <miquel.raynal@bootlin.com>
 *
 *
 * This file describes the abstraction of any NAND ECC engine. It has been
 * designed to fit most cases, including parallel NANDs and SPI-NANDs.
 *
 * There are three main situations where instantiating this ECC engine makes
 * sense:
 *   - external: The ECC engine is outside the NAND pipeline, typically this
 *               is a software ECC engine, or an hardware engine that is
 *               outside the NAND controller pipeline.
 *   - pipelined: The ECC engine is inside the NAND pipeline, ie. on the
 *                controller's side. This is the case of most of the raw NAND
 *                controllers. In the pipeline case, the ECC bytes are
 *                generated/data corrected on the fly when a page is
 *                written/read.
 *   - ondie: The ECC engine is inside the NAND pipeline, on the chip's side.
 *            Some NAND chips can correct themselves the data.
 *
 * Besides the initial setup and final cleanups, the interfaces are rather
 * simple:
 *   - prepare: Prepare an I/O request. Enable/disable the ECC engine based on
 *              the I/O request type. In case of software correction or external
 *              engine, this step may involve to derive the ECC bytes and place
 *              them in the OOB area before a write.
 *   - finish: Finish an I/O request. Correct the data in case of a read
 *             request and report the number of corrected bits/uncorrectable
 *             errors. Most likely empty for write operations, unless you have
 *             hardware specific stuff to do, like shutting down the engine to
 *             save power.
 *
 * The I/O request should be enclosed in a prepare()/finish() pair of calls
 * and will behave differently depending on the requested I/O type:
 *   - raw: Correction disabled
 *   - ecc: Correction enabled
 *
 * The request direction is impacting the logic as well:
 *   - read: Load data from the NAND chip
 *   - write: Store data in the NAND chip
 *
 * Mixing all this combinations together gives the following behavior.
 * Those are just examples, drivers are free to add custom steps in their
 * prepare/finish hook.
 *
 * [external ECC engine]
 *   - external + prepare + raw + read: do nothing
 *   - external + finish  + raw + read: do nothing
 *   - external + prepare + raw + write: do nothing
 *   - external + finish  + raw + write: do nothing
 *   - external + prepare + ecc + read: do nothing
 *   - external + finish  + ecc + read: calculate expected ECC bytes, extract
 *                                      ECC bytes from OOB buffer, correct
 *                                      and report any bitflip/error
 *   - external + prepare + ecc + write: calculate ECC bytes and store them at
 *                                       the right place in the OOB buffer based
 *                                       on the OOB layout
 *   - external + finish  + ecc + write: do nothing
 *
 * [pipelined ECC engine]
 *   - pipelined + prepare + raw + read: disable the controller's ECC engine if
 *                                       activated
 *   - pipelined + finish  + raw + read: do nothing
 *   - pipelined + prepare + raw + write: disable the controller's ECC engine if
 *                                        activated
 *   - pipelined + finish  + raw + write: do nothing
 *   - pipelined + prepare + ecc + read: enable the controller's ECC engine if
 *                                       deactivated
 *   - pipelined + finish  + ecc + read: check the status, report any
 *                                       error/bitflip
 *   - pipelined + prepare + ecc + write: enable the controller's ECC engine if
 *                                        deactivated
 *   - pipelined + finish  + ecc + write: do nothing
 *
 * [ondie ECC engine]
 *   - ondie + prepare + raw + read: send commands to disable the on-chip ECC
 *                                   engine if activated
 *   - ondie + finish  + raw + read: do nothing
 *   - ondie + prepare + raw + write: send commands to disable the on-chip ECC
 *                                    engine if activated
 *   - ondie + finish  + raw + write: do nothing
 *   - ondie + prepare + ecc + read: send commands to enable the on-chip ECC
 *                                   engine if deactivated
 *   - ondie + finish  + ecc + read: send commands to check the status, report
 *                                   any error/bitflip
 *   - ondie + prepare + ecc + write: send commands to enable the on-chip ECC
 *                                    engine if deactivated
 *   - ondie + finish  + ecc + write: do nothing
 */

#include <linux/module.h>
#include <linux/mtd/nand.h>
#include <linux/slab.h>
#include <linux/of.h>
#include <linux/of_device.h>
#include <linux/of_platform.h>

static LIST_HEAD(on_host_hw_engines);
static DEFINE_MUTEX(on_host_hw_engines_mutex);

/**
 * nand_ecc_init_ctx - Init the ECC engine context
 * @nand: the NAND device
 *
 * On success, the caller is responsible of calling @nand_ecc_cleanup_ctx().
 */
int nand_ecc_init_ctx(struct nand_device *nand)
{
	if (!nand->ecc.engine || !nand->ecc.engine->ops->init_ctx)
		return 0;

	return nand->ecc.engine->ops->init_ctx(nand);
}
EXPORT_SYMBOL(nand_ecc_init_ctx);

/**
 * nand_ecc_cleanup_ctx - Cleanup the ECC engine context
 * @nand: the NAND device
 */
void nand_ecc_cleanup_ctx(struct nand_device *nand)
{
	if (nand->ecc.engine && nand->ecc.engine->ops->cleanup_ctx)
		nand->ecc.engine->ops->cleanup_ctx(nand);
}
EXPORT_SYMBOL(nand_ecc_cleanup_ctx);

/**
 * nand_ecc_prepare_io_req - Prepare an I/O request
 * @nand: the NAND device
 * @req: the I/O request
 */
int nand_ecc_prepare_io_req(struct nand_device *nand,
			    struct nand_page_io_req *req)
{
	if (!nand->ecc.engine || !nand->ecc.engine->ops->prepare_io_req)
		return 0;

	return nand->ecc.engine->ops->prepare_io_req(nand, req);
}
EXPORT_SYMBOL(nand_ecc_prepare_io_req);

/**
 * nand_ecc_finish_io_req - Finish an I/O request
 * @nand: the NAND device
 * @req: the I/O request
 */
int nand_ecc_finish_io_req(struct nand_device *nand,
			   struct nand_page_io_req *req)
{
	if (!nand->ecc.engine || !nand->ecc.engine->ops->finish_io_req)
		return 0;

	return nand->ecc.engine->ops->finish_io_req(nand, req);
}
EXPORT_SYMBOL(nand_ecc_finish_io_req);

/* Define default OOB placement schemes for large and small page devices */
static int nand_ooblayout_ecc_sp(struct mtd_info *mtd, int section,
				 struct mtd_oob_region *oobregion)
{
	struct nand_device *nand = mtd_to_nanddev(mtd);
	unsigned int total_ecc_bytes = nand->ecc.ctx.total;

	if (section > 1)
		return -ERANGE;

	if (!section) {
		oobregion->offset = 0;
		if (mtd->oobsize == 16)
			oobregion->length = 4;
		else
			oobregion->length = 3;
	} else {
		if (mtd->oobsize == 8)
			return -ERANGE;

		oobregion->offset = 6;
		oobregion->length = total_ecc_bytes - 4;
	}

	return 0;
}

static int nand_ooblayout_free_sp(struct mtd_info *mtd, int section,
				  struct mtd_oob_region *oobregion)
{
	if (section > 1)
		return -ERANGE;

	if (mtd->oobsize == 16) {
		if (section)
			return -ERANGE;

		oobregion->length = 8;
		oobregion->offset = 8;
	} else {
		oobregion->length = 2;
		if (!section)
			oobregion->offset = 3;
		else
			oobregion->offset = 6;
	}

	return 0;
}

static const struct mtd_ooblayout_ops nand_ooblayout_sp_ops = {
	.ecc = nand_ooblayout_ecc_sp,
	.free = nand_ooblayout_free_sp,
};

const struct mtd_ooblayout_ops *nand_get_small_page_ooblayout(void)
{
	return &nand_ooblayout_sp_ops;
}
EXPORT_SYMBOL_GPL(nand_get_small_page_ooblayout);

static int nand_ooblayout_ecc_lp(struct mtd_info *mtd, int section,
				 struct mtd_oob_region *oobregion)
{
	struct nand_device *nand = mtd_to_nanddev(mtd);
	unsigned int total_ecc_bytes = nand->ecc.ctx.total;

	if (section || !total_ecc_bytes)
		return -ERANGE;

	oobregion->length = total_ecc_bytes;
	oobregion->offset = mtd->oobsize - oobregion->length;

	return 0;
}

static int nand_ooblayout_free_lp(struct mtd_info *mtd, int section,
				  struct mtd_oob_region *oobregion)
{
	struct nand_device *nand = mtd_to_nanddev(mtd);
	unsigned int total_ecc_bytes = nand->ecc.ctx.total;

	if (section)
		return -ERANGE;

	oobregion->length = mtd->oobsize - total_ecc_bytes - 2;
	oobregion->offset = 2;

	return 0;
}

static const struct mtd_ooblayout_ops nand_ooblayout_lp_ops = {
	.ecc = nand_ooblayout_ecc_lp,
	.free = nand_ooblayout_free_lp,
};

const struct mtd_ooblayout_ops *nand_get_large_page_ooblayout(void)
{
	return &nand_ooblayout_lp_ops;
}
EXPORT_SYMBOL_GPL(nand_get_large_page_ooblayout);

/*
 * Support the old "large page" layout used for 1-bit Hamming ECC where ECC
 * are placed at a fixed offset.
 */
static int nand_ooblayout_ecc_lp_hamming(struct mtd_info *mtd, int section,
					 struct mtd_oob_region *oobregion)
{
	struct nand_device *nand = mtd_to_nanddev(mtd);
	unsigned int total_ecc_bytes = nand->ecc.ctx.total;

	if (section)
		return -ERANGE;

	switch (mtd->oobsize) {
	case 64:
		oobregion->offset = 40;
		break;
	case 128:
		oobregion->offset = 80;
		break;
	default:
		return -EINVAL;
	}

	oobregion->length = total_ecc_bytes;
	if (oobregion->offset + oobregion->length > mtd->oobsize)
		return -ERANGE;

	return 0;
}

static int nand_ooblayout_free_lp_hamming(struct mtd_info *mtd, int section,
					  struct mtd_oob_region *oobregion)
{
	struct nand_device *nand = mtd_to_nanddev(mtd);
	unsigned int total_ecc_bytes = nand->ecc.ctx.total;
	int ecc_offset = 0;

	if (section < 0 || section > 1)
		return -ERANGE;

	switch (mtd->oobsize) {
	case 64:
		ecc_offset = 40;
		break;
	case 128:
		ecc_offset = 80;
		break;
	default:
		return -EINVAL;
	}

	if (section == 0) {
		oobregion->offset = 2;
		oobregion->length = ecc_offset - 2;
	} else {
		oobregion->offset = ecc_offset + total_ecc_bytes;
		oobregion->length = mtd->oobsize - oobregion->offset;
	}

	return 0;
}

static const struct mtd_ooblayout_ops nand_ooblayout_lp_hamming_ops = {
	.ecc = nand_ooblayout_ecc_lp_hamming,
	.free = nand_ooblayout_free_lp_hamming,
};

const struct mtd_ooblayout_ops *nand_get_large_page_hamming_ooblayout(void)
{
	return &nand_ooblayout_lp_hamming_ops;
}
EXPORT_SYMBOL_GPL(nand_get_large_page_hamming_ooblayout);

static enum nand_ecc_engine_type
of_get_nand_ecc_engine_type(struct device_node *np)
{
	struct device_node *eng_np;

	if (of_property_read_bool(np, "nand-no-ecc-engine"))
		return NAND_ECC_ENGINE_TYPE_NONE;

	if (of_property_read_bool(np, "nand-use-soft-ecc-engine"))
		return NAND_ECC_ENGINE_TYPE_SOFT;

	eng_np = of_parse_phandle(np, "nand-ecc-engine", 0);
	of_node_put(eng_np);

	if (eng_np) {
		if (eng_np == np)
			return NAND_ECC_ENGINE_TYPE_ON_DIE;
		else
			return NAND_ECC_ENGINE_TYPE_ON_HOST;
	}

	return NAND_ECC_ENGINE_TYPE_INVALID;
}

static const char * const nand_ecc_placement[] = {
	[NAND_ECC_PLACEMENT_OOB] = "oob",
	[NAND_ECC_PLACEMENT_INTERLEAVED] = "interleaved",
};

static enum nand_ecc_placement of_get_nand_ecc_placement(struct device_node *np)
{
	enum nand_ecc_placement placement;
	const char *pm;
	int err;

	err = of_property_read_string(np, "nand-ecc-placement", &pm);
	if (!err) {
		for (placement = NAND_ECC_PLACEMENT_OOB;
		     placement < ARRAY_SIZE(nand_ecc_placement); placement++) {
			if (!strcasecmp(pm, nand_ecc_placement[placement]))
				return placement;
		}
	}

	return NAND_ECC_PLACEMENT_UNKNOWN;
}

static const char * const nand_ecc_algos[] = {
	[NAND_ECC_ALGO_HAMMING] = "hamming",
	[NAND_ECC_ALGO_BCH] = "bch",
	[NAND_ECC_ALGO_RS] = "rs",
};

static enum nand_ecc_algo of_get_nand_ecc_algo(struct device_node *np)
{
	enum nand_ecc_algo ecc_algo;
	const char *pm;
	int err;

	err = of_property_read_string(np, "nand-ecc-algo", &pm);
	if (!err) {
		for (ecc_algo = NAND_ECC_ALGO_HAMMING;
		     ecc_algo < ARRAY_SIZE(nand_ecc_algos);
		     ecc_algo++) {
			if (!strcasecmp(pm, nand_ecc_algos[ecc_algo]))
				return ecc_algo;
		}
	}

	return NAND_ECC_ALGO_UNKNOWN;
}

static int of_get_nand_ecc_step_size(struct device_node *np)
{
	int ret;
	u32 val;

	ret = of_property_read_u32(np, "nand-ecc-step-size", &val);
	return ret ? ret : val;
}

static int of_get_nand_ecc_strength(struct device_node *np)
{
	int ret;
	u32 val;

	ret = of_property_read_u32(np, "nand-ecc-strength", &val);
	return ret ? ret : val;
}

void of_get_nand_ecc_user_config(struct nand_device *nand)
{
	struct device_node *dn = nanddev_get_of_node(nand);
	int strength, size;

	nand->ecc.user_conf.engine_type = of_get_nand_ecc_engine_type(dn);
	nand->ecc.user_conf.algo = of_get_nand_ecc_algo(dn);
	nand->ecc.user_conf.placement = of_get_nand_ecc_placement(dn);

	strength = of_get_nand_ecc_strength(dn);
	if (strength >= 0)
		nand->ecc.user_conf.strength = strength;

	size = of_get_nand_ecc_step_size(dn);
	if (size >= 0)
		nand->ecc.user_conf.step_size = size;

	if (of_property_read_bool(dn, "nand-ecc-maximize"))
		nand->ecc.user_conf.flags |= NAND_ECC_MAXIMIZE_STRENGTH;
}
EXPORT_SYMBOL(of_get_nand_ecc_user_config);

/**
 * nand_ecc_is_strong_enough - Check if the chip configuration meets the
 *                             datasheet requirements.
 *
 * @nand: Device to check
 *
 * If our configuration corrects A bits per B bytes and the minimum
 * required correction level is X bits per Y bytes, then we must ensure
 * both of the following are true:
 *
 * (1) A / B >= X / Y
 * (2) A >= X
 *
 * Requirement (1) ensures we can correct for the required bitflip density.
 * Requirement (2) ensures we can correct even when all bitflips are clumped
 * in the same sector.
 */
bool nand_ecc_is_strong_enough(struct nand_device *nand)
{
	const struct nand_ecc_props *reqs = nanddev_get_ecc_requirements(nand);
	const struct nand_ecc_props *conf = nanddev_get_ecc_conf(nand);
	struct mtd_info *mtd = nanddev_to_mtd(nand);
	int corr, ds_corr;

	if (conf->step_size == 0 || reqs->step_size == 0)
		/* Not enough information */
		return true;

	/*
	 * We get the number of corrected bits per page to compare
	 * the correction density.
	 */
	corr = (mtd->writesize * conf->strength) / conf->step_size;
	ds_corr = (mtd->writesize * reqs->strength) / reqs->step_size;

	return corr >= ds_corr && conf->strength >= reqs->strength;
}
EXPORT_SYMBOL(nand_ecc_is_strong_enough);

/* ECC engine driver internal helpers */
int nand_ecc_init_req_tweaking(struct nand_ecc_req_tweak_ctx *ctx,
			       struct nand_device *nand)
{
	unsigned int total_buffer_size;

	ctx->nand = nand;

	/* Let the user decide the exact length of each buffer */
	if (!ctx->page_buffer_size)
		ctx->page_buffer_size = nanddev_page_size(nand);
	if (!ctx->oob_buffer_size)
		ctx->oob_buffer_size = nanddev_per_page_oobsize(nand);

	total_buffer_size = ctx->page_buffer_size + ctx->oob_buffer_size;

	ctx->spare_databuf = kzalloc(total_buffer_size, GFP_KERNEL);
	if (!ctx->spare_databuf)
		return -ENOMEM;

	ctx->spare_oobbuf = ctx->spare_databuf + ctx->page_buffer_size;

	return 0;
}
EXPORT_SYMBOL_GPL(nand_ecc_init_req_tweaking);

void nand_ecc_cleanup_req_tweaking(struct nand_ecc_req_tweak_ctx *ctx)
{
	kfree(ctx->spare_databuf);
}
EXPORT_SYMBOL_GPL(nand_ecc_cleanup_req_tweaking);

/*
 * Ensure data and OOB area is fully read/written otherwise the correction might
 * not work as expected.
 */
void nand_ecc_tweak_req(struct nand_ecc_req_tweak_ctx *ctx,
			struct nand_page_io_req *req)
{
	struct nand_device *nand = ctx->nand;
	struct nand_page_io_req *orig, *tweak;

	/* Save the original request */
	ctx->orig_req = *req;
	ctx->bounce_data = false;
	ctx->bounce_oob = false;
	orig = &ctx->orig_req;
	tweak = req;

	/* Ensure the request covers the entire page */
	if (orig->datalen < nanddev_page_size(nand)) {
		ctx->bounce_data = true;
		tweak->dataoffs = 0;
		tweak->datalen = nanddev_page_size(nand);
		tweak->databuf.in = ctx->spare_databuf;
		memset(tweak->databuf.in, 0xFF, ctx->page_buffer_size);
	}

	if (orig->ooblen < nanddev_per_page_oobsize(nand)) {
		ctx->bounce_oob = true;
		tweak->ooboffs = 0;
		tweak->ooblen = nanddev_per_page_oobsize(nand);
		tweak->oobbuf.in = ctx->spare_oobbuf;
		memset(tweak->oobbuf.in, 0xFF, ctx->oob_buffer_size);
	}

	/* Copy the data that must be writen in the bounce buffers, if needed */
	if (orig->type == NAND_PAGE_WRITE) {
		if (ctx->bounce_data)
			memcpy((void *)tweak->databuf.out + orig->dataoffs,
			       orig->databuf.out, orig->datalen);

		if (ctx->bounce_oob)
			memcpy((void *)tweak->oobbuf.out + orig->ooboffs,
			       orig->oobbuf.out, orig->ooblen);
	}
}
EXPORT_SYMBOL_GPL(nand_ecc_tweak_req);

void nand_ecc_restore_req(struct nand_ecc_req_tweak_ctx *ctx,
			  struct nand_page_io_req *req)
{
	struct nand_page_io_req *orig, *tweak;

	orig = &ctx->orig_req;
	tweak = req;

	/* Restore the data read from the bounce buffers, if needed */
	if (orig->type == NAND_PAGE_READ) {
		if (ctx->bounce_data)
			memcpy(orig->databuf.in,
			       tweak->databuf.in + orig->dataoffs,
			       orig->datalen);

		if (ctx->bounce_oob)
			memcpy(orig->oobbuf.in,
			       tweak->oobbuf.in + orig->ooboffs,
			       orig->ooblen);
	}

	/* Ensure the original request is restored */
	*req = *orig;
}
EXPORT_SYMBOL_GPL(nand_ecc_restore_req);

struct nand_ecc_engine *nand_ecc_get_sw_engine(struct nand_device *nand)
{
	unsigned int algo = nand->ecc.user_conf.algo;

	if (algo == NAND_ECC_ALGO_UNKNOWN)
		algo = nand->ecc.defaults.algo;

	switch (algo) {
	case NAND_ECC_ALGO_HAMMING:
		return nand_ecc_sw_hamming_get_engine();
	case NAND_ECC_ALGO_BCH:
		return nand_ecc_sw_bch_get_engine();
	default:
		break;
	}

	return NULL;
}
EXPORT_SYMBOL(nand_ecc_get_sw_engine);

struct nand_ecc_engine *nand_ecc_get_on_die_hw_engine(struct nand_device *nand)
{
	return nand->ecc.ondie_engine;
}
EXPORT_SYMBOL(nand_ecc_get_on_die_hw_engine);

int nand_ecc_register_on_host_hw_engine(struct nand_ecc_engine *engine)
{
	struct nand_ecc_engine *item;

	if (!engine)
		return -EINVAL;

	/* Prevent multiple registrations of one engine */
	list_for_each_entry(item, &on_host_hw_engines, node)
		if (item == engine)
			return 0;

	mutex_lock(&on_host_hw_engines_mutex);
	list_add_tail(&engine->node, &on_host_hw_engines);
	mutex_unlock(&on_host_hw_engines_mutex);

	return 0;
}
EXPORT_SYMBOL(nand_ecc_register_on_host_hw_engine);

int nand_ecc_unregister_on_host_hw_engine(struct nand_ecc_engine *engine)
{
	if (!engine)
		return -EINVAL;

	mutex_lock(&on_host_hw_engines_mutex);
	list_del(&engine->node);
	mutex_unlock(&on_host_hw_engines_mutex);

	return 0;
}
EXPORT_SYMBOL(nand_ecc_unregister_on_host_hw_engine);

static struct nand_ecc_engine *nand_ecc_match_on_host_hw_engine(struct device *dev)
{
	struct nand_ecc_engine *item;

	list_for_each_entry(item, &on_host_hw_engines, node)
		if (item->dev == dev)
			return item;

	return NULL;
}

struct nand_ecc_engine *nand_ecc_get_on_host_hw_engine(struct nand_device *nand)
{
	struct nand_ecc_engine *engine = NULL;
	struct device *dev = &nand->mtd.dev;
	struct platform_device *pdev;
	struct device_node *np;

	if (list_empty(&on_host_hw_engines))
		return NULL;

	/* Check for an explicit nand-ecc-engine property */
	np = of_parse_phandle(dev->of_node, "nand-ecc-engine", 0);
	if (np) {
		pdev = of_find_device_by_node(np);
		if (!pdev)
			return ERR_PTR(-EPROBE_DEFER);

		engine = nand_ecc_match_on_host_hw_engine(&pdev->dev);
		platform_device_put(pdev);
		of_node_put(np);

		if (!engine)
			return ERR_PTR(-EPROBE_DEFER);
	}

	if (engine)
		get_device(engine->dev);

	return engine;
}
EXPORT_SYMBOL(nand_ecc_get_on_host_hw_engine);

void nand_ecc_put_on_host_hw_engine(struct nand_device *nand)
{
	put_device(nand->ecc.engine->dev);
}
EXPORT_SYMBOL(nand_ecc_put_on_host_hw_engine);

/*
 * In the case of a pipelined engine, the device registering the ECC
 * engine is not necessarily the ECC engine itself but may be a host controller.
 * It is then useful to provide a helper to retrieve the right device object
 * which actually represents the ECC engine.
 */
struct device *nand_ecc_get_engine_dev(struct device *host)
{
	struct platform_device *ecc_pdev;
	struct device_node *np;

	/*
	 * If the device node contains this property, it means we need to follow
	 * it in order to get the right ECC engine device we are looking for.
	 */
	np = of_parse_phandle(host->of_node, "nand-ecc-engine", 0);
	if (!np)
		return host;

	ecc_pdev = of_find_device_by_node(np);
	if (!ecc_pdev) {
		of_node_put(np);
		return NULL;
	}

	platform_device_put(ecc_pdev);
	of_node_put(np);

	return &ecc_pdev->dev;
}

MODULE_LICENSE("GPL");
MODULE_AUTHOR("Miquel Raynal <miquel.raynal@bootlin.com>");
MODULE_DESCRIPTION("Generic ECC engine");