summaryrefslogtreecommitdiff
path: root/drivers/spi/spi-ep93xx.c
blob: 9a9e27b52a242241e0b4f185bd042a84d105de6c (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
736
737
738
739
740
741
742
743
744
745
746
747
748
749
750
751
752
753
754
755
756
757
758
759
760
761
762
763
764
765
766
767
768
769
770
771
772
773
774
775
776
777
778
779
780
781
782
783
784
785
786
787
788
789
790
791
792
793
794
795
796
797
798
799
800
801
802
803
804
805
806
807
808
809
810
811
812
813
814
815
816
817
818
819
820
821
822
823
824
825
826
827
828
829
830
831
832
833
834
835
836
837
838
839
840
841
842
843
844
845
846
847
848
849
850
851
852
853
854
855
856
857
858
859
860
861
862
863
864
865
866
867
868
869
870
871
872
873
874
875
876
877
878
879
880
881
882
883
884
885
886
887
888
889
890
891
892
893
894
895
896
897
898
899
900
901
902
903
904
905
906
907
908
909
910
911
912
913
914
915
916
917
918
919
920
921
922
923
924
925
926
927
928
929
930
931
932
933
934
935
936
937
938
939
940
941
942
943
944
945
946
947
948
949
950
951
952
953
954
955
956
957
958
959
960
961
962
963
964
965
966
967
968
969
970
971
972
973
974
975
976
977
978
979
980
981
982
983
984
985
986
987
988
989
990
991
992
993
994
995
996
997
998
999
1000
1001
1002
1003
1004
1005
1006
1007
1008
1009
1010
1011
1012
1013
1014
1015
1016
1017
1018
1019
1020
1021
1022
1023
1024
1025
1026
1027
1028
1029
1030
1031
1032
1033
1034
1035
1036
1037
1038
1039
1040
1041
1042
1043
1044
1045
1046
1047
1048
1049
1050
1051
1052
1053
1054
1055
1056
1057
1058
1059
1060
1061
1062
1063
1064
1065
1066
1067
1068
1069
1070
1071
1072
1073
1074
1075
1076
1077
1078
1079
1080
1081
1082
1083
1084
1085
1086
1087
1088
1089
1090
1091
1092
1093
1094
1095
1096
1097
1098
1099
1100
1101
1102
1103
1104
1105
1106
1107
1108
1109
1110
1111
1112
1113
1114
1115
1116
1117
1118
1119
1120
1121
1122
1123
1124
1125
1126
1127
1128
1129
1130
1131
1132
1133
1134
1135
1136
1137
1138
1139
1140
1141
1142
1143
1144
1145
1146
1147
1148
1149
1150
1151
1152
1153
1154
1155
1156
1157
1158
1159
1160
1161
1162
1163
1164
1165
1166
1167
1168
1169
1170
1171
1172
1173
1174
1175
1176
1177
1178
1179
1180
1181
1182
1183
1184
1185
1186
1187
1188
1189
1190
1191
1192
1193
1194
1195
1196
1197
1198
1199
1200
1201
1202
1203
1204
1205
1206
1207
1208
1209
1210
1211
1212
1213
1214
1215
1216
1217
/*
 * Driver for Cirrus Logic EP93xx SPI controller.
 *
 * Copyright (C) 2010-2011 Mika Westerberg
 *
 * Explicit FIFO handling code was inspired by amba-pl022 driver.
 *
 * Chip select support using other than built-in GPIOs by H. Hartley Sweeten.
 *
 * For more information about the SPI controller see documentation on Cirrus
 * Logic web site:
 *     http://www.cirrus.com/en/pubs/manual/EP93xx_Users_Guide_UM1.pdf
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License version 2 as
 * published by the Free Software Foundation.
 */

#include <linux/io.h>
#include <linux/clk.h>
#include <linux/err.h>
#include <linux/delay.h>
#include <linux/device.h>
#include <linux/dmaengine.h>
#include <linux/bitops.h>
#include <linux/interrupt.h>
#include <linux/platform_device.h>
#include <linux/workqueue.h>
#include <linux/sched.h>
#include <linux/scatterlist.h>
#include <linux/spi/spi.h>

#include <mach/dma.h>
#include <mach/ep93xx_spi.h>

#define SSPCR0			0x0000
#define SSPCR0_MODE_SHIFT	6
#define SSPCR0_SCR_SHIFT	8

#define SSPCR1			0x0004
#define SSPCR1_RIE		BIT(0)
#define SSPCR1_TIE		BIT(1)
#define SSPCR1_RORIE		BIT(2)
#define SSPCR1_LBM		BIT(3)
#define SSPCR1_SSE		BIT(4)
#define SSPCR1_MS		BIT(5)
#define SSPCR1_SOD		BIT(6)

#define SSPDR			0x0008

#define SSPSR			0x000c
#define SSPSR_TFE		BIT(0)
#define SSPSR_TNF		BIT(1)
#define SSPSR_RNE		BIT(2)
#define SSPSR_RFF		BIT(3)
#define SSPSR_BSY		BIT(4)
#define SSPCPSR			0x0010

#define SSPIIR			0x0014
#define SSPIIR_RIS		BIT(0)
#define SSPIIR_TIS		BIT(1)
#define SSPIIR_RORIS		BIT(2)
#define SSPICR			SSPIIR

/* timeout in milliseconds */
#define SPI_TIMEOUT		5
/* maximum depth of RX/TX FIFO */
#define SPI_FIFO_SIZE		8

/**
 * struct ep93xx_spi - EP93xx SPI controller structure
 * @lock: spinlock that protects concurrent accesses to fields @running,
 *        @current_msg and @msg_queue
 * @pdev: pointer to platform device
 * @clk: clock for the controller
 * @regs_base: pointer to ioremap()'d registers
 * @sspdr_phys: physical address of the SSPDR register
 * @irq: IRQ number used by the driver
 * @min_rate: minimum clock rate (in Hz) supported by the controller
 * @max_rate: maximum clock rate (in Hz) supported by the controller
 * @running: is the queue running
 * @wq: workqueue used by the driver
 * @msg_work: work that is queued for the driver
 * @wait: wait here until given transfer is completed
 * @msg_queue: queue for the messages
 * @current_msg: message that is currently processed (or %NULL if none)
 * @tx: current byte in transfer to transmit
 * @rx: current byte in transfer to receive
 * @fifo_level: how full is FIFO (%0..%SPI_FIFO_SIZE - %1). Receiving one
 *              frame decreases this level and sending one frame increases it.
 * @dma_rx: RX DMA channel
 * @dma_tx: TX DMA channel
 * @dma_rx_data: RX parameters passed to the DMA engine
 * @dma_tx_data: TX parameters passed to the DMA engine
 * @rx_sgt: sg table for RX transfers
 * @tx_sgt: sg table for TX transfers
 * @zeropage: dummy page used as RX buffer when only TX buffer is passed in by
 *            the client
 *
 * This structure holds EP93xx SPI controller specific information. When
 * @running is %true, driver accepts transfer requests from protocol drivers.
 * @current_msg is used to hold pointer to the message that is currently
 * processed. If @current_msg is %NULL, it means that no processing is going
 * on.
 *
 * Most of the fields are only written once and they can be accessed without
 * taking the @lock. Fields that are accessed concurrently are: @current_msg,
 * @running, and @msg_queue.
 */
struct ep93xx_spi {
	spinlock_t			lock;
	const struct platform_device	*pdev;
	struct clk			*clk;
	void __iomem			*regs_base;
	unsigned long			sspdr_phys;
	int				irq;
	unsigned long			min_rate;
	unsigned long			max_rate;
	bool				running;
	struct workqueue_struct		*wq;
	struct work_struct		msg_work;
	struct completion		wait;
	struct list_head		msg_queue;
	struct spi_message		*current_msg;
	size_t				tx;
	size_t				rx;
	size_t				fifo_level;
	struct dma_chan			*dma_rx;
	struct dma_chan			*dma_tx;
	struct ep93xx_dma_data		dma_rx_data;
	struct ep93xx_dma_data		dma_tx_data;
	struct sg_table			rx_sgt;
	struct sg_table			tx_sgt;
	void				*zeropage;
};

/**
 * struct ep93xx_spi_chip - SPI device hardware settings
 * @spi: back pointer to the SPI device
 * @rate: max rate in hz this chip supports
 * @div_cpsr: cpsr (pre-scaler) divider
 * @div_scr: scr divider
 * @dss: bits per word (4 - 16 bits)
 * @ops: private chip operations
 *
 * This structure is used to store hardware register specific settings for each
 * SPI device. Settings are written to hardware by function
 * ep93xx_spi_chip_setup().
 */
struct ep93xx_spi_chip {
	const struct spi_device		*spi;
	unsigned long			rate;
	u8				div_cpsr;
	u8				div_scr;
	u8				dss;
	struct ep93xx_spi_chip_ops	*ops;
};

/* converts bits per word to CR0.DSS value */
#define bits_per_word_to_dss(bpw)	((bpw) - 1)

static inline void
ep93xx_spi_write_u8(const struct ep93xx_spi *espi, u16 reg, u8 value)
{
	__raw_writeb(value, espi->regs_base + reg);
}

static inline u8
ep93xx_spi_read_u8(const struct ep93xx_spi *spi, u16 reg)
{
	return __raw_readb(spi->regs_base + reg);
}

static inline void
ep93xx_spi_write_u16(const struct ep93xx_spi *espi, u16 reg, u16 value)
{
	__raw_writew(value, espi->regs_base + reg);
}

static inline u16
ep93xx_spi_read_u16(const struct ep93xx_spi *spi, u16 reg)
{
	return __raw_readw(spi->regs_base + reg);
}

static int ep93xx_spi_enable(const struct ep93xx_spi *espi)
{
	u8 regval;
	int err;

	err = clk_enable(espi->clk);
	if (err)
		return err;

	regval = ep93xx_spi_read_u8(espi, SSPCR1);
	regval |= SSPCR1_SSE;
	ep93xx_spi_write_u8(espi, SSPCR1, regval);

	return 0;
}

static void ep93xx_spi_disable(const struct ep93xx_spi *espi)
{
	u8 regval;

	regval = ep93xx_spi_read_u8(espi, SSPCR1);
	regval &= ~SSPCR1_SSE;
	ep93xx_spi_write_u8(espi, SSPCR1, regval);

	clk_disable(espi->clk);
}

static void ep93xx_spi_enable_interrupts(const struct ep93xx_spi *espi)
{
	u8 regval;

	regval = ep93xx_spi_read_u8(espi, SSPCR1);
	regval |= (SSPCR1_RORIE | SSPCR1_TIE | SSPCR1_RIE);
	ep93xx_spi_write_u8(espi, SSPCR1, regval);
}

static void ep93xx_spi_disable_interrupts(const struct ep93xx_spi *espi)
{
	u8 regval;

	regval = ep93xx_spi_read_u8(espi, SSPCR1);
	regval &= ~(SSPCR1_RORIE | SSPCR1_TIE | SSPCR1_RIE);
	ep93xx_spi_write_u8(espi, SSPCR1, regval);
}

/**
 * ep93xx_spi_calc_divisors() - calculates SPI clock divisors
 * @espi: ep93xx SPI controller struct
 * @chip: divisors are calculated for this chip
 * @rate: desired SPI output clock rate
 *
 * Function calculates cpsr (clock pre-scaler) and scr divisors based on
 * given @rate and places them to @chip->div_cpsr and @chip->div_scr. If,
 * for some reason, divisors cannot be calculated nothing is stored and
 * %-EINVAL is returned.
 */
static int ep93xx_spi_calc_divisors(const struct ep93xx_spi *espi,
				    struct ep93xx_spi_chip *chip,
				    unsigned long rate)
{
	unsigned long spi_clk_rate = clk_get_rate(espi->clk);
	int cpsr, scr;

	/*
	 * Make sure that max value is between values supported by the
	 * controller. Note that minimum value is already checked in
	 * ep93xx_spi_transfer().
	 */
	rate = clamp(rate, espi->min_rate, espi->max_rate);

	/*
	 * Calculate divisors so that we can get speed according the
	 * following formula:
	 *	rate = spi_clock_rate / (cpsr * (1 + scr))
	 *
	 * cpsr must be even number and starts from 2, scr can be any number
	 * between 0 and 255.
	 */
	for (cpsr = 2; cpsr <= 254; cpsr += 2) {
		for (scr = 0; scr <= 255; scr++) {
			if ((spi_clk_rate / (cpsr * (scr + 1))) <= rate) {
				chip->div_scr = (u8)scr;
				chip->div_cpsr = (u8)cpsr;
				return 0;
			}
		}
	}

	return -EINVAL;
}

static void ep93xx_spi_cs_control(struct spi_device *spi, bool control)
{
	struct ep93xx_spi_chip *chip = spi_get_ctldata(spi);
	int value = (spi->mode & SPI_CS_HIGH) ? control : !control;

	if (chip->ops && chip->ops->cs_control)
		chip->ops->cs_control(spi, value);
}

/**
 * ep93xx_spi_setup() - setup an SPI device
 * @spi: SPI device to setup
 *
 * This function sets up SPI device mode, speed etc. Can be called multiple
 * times for a single device. Returns %0 in case of success, negative error in
 * case of failure. When this function returns success, the device is
 * deselected.
 */
static int ep93xx_spi_setup(struct spi_device *spi)
{
	struct ep93xx_spi *espi = spi_master_get_devdata(spi->master);
	struct ep93xx_spi_chip *chip;

	if (spi->bits_per_word < 4 || spi->bits_per_word > 16) {
		dev_err(&espi->pdev->dev, "invalid bits per word %d\n",
			spi->bits_per_word);
		return -EINVAL;
	}

	chip = spi_get_ctldata(spi);
	if (!chip) {
		dev_dbg(&espi->pdev->dev, "initial setup for %s\n",
			spi->modalias);

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

		chip->spi = spi;
		chip->ops = spi->controller_data;

		if (chip->ops && chip->ops->setup) {
			int ret = chip->ops->setup(spi);
			if (ret) {
				kfree(chip);
				return ret;
			}
		}

		spi_set_ctldata(spi, chip);
	}

	if (spi->max_speed_hz != chip->rate) {
		int err;

		err = ep93xx_spi_calc_divisors(espi, chip, spi->max_speed_hz);
		if (err != 0) {
			spi_set_ctldata(spi, NULL);
			kfree(chip);
			return err;
		}
		chip->rate = spi->max_speed_hz;
	}

	chip->dss = bits_per_word_to_dss(spi->bits_per_word);

	ep93xx_spi_cs_control(spi, false);
	return 0;
}

/**
 * ep93xx_spi_transfer() - queue message to be transferred
 * @spi: target SPI device
 * @msg: message to be transferred
 *
 * This function is called by SPI device drivers when they are going to transfer
 * a new message. It simply puts the message in the queue and schedules
 * workqueue to perform the actual transfer later on.
 *
 * Returns %0 on success and negative error in case of failure.
 */
static int ep93xx_spi_transfer(struct spi_device *spi, struct spi_message *msg)
{
	struct ep93xx_spi *espi = spi_master_get_devdata(spi->master);
	struct spi_transfer *t;
	unsigned long flags;

	if (!msg || !msg->complete)
		return -EINVAL;

	/* first validate each transfer */
	list_for_each_entry(t, &msg->transfers, transfer_list) {
		if (t->bits_per_word) {
			if (t->bits_per_word < 4 || t->bits_per_word > 16)
				return -EINVAL;
		}
		if (t->speed_hz && t->speed_hz < espi->min_rate)
				return -EINVAL;
	}

	/*
	 * Now that we own the message, let's initialize it so that it is
	 * suitable for us. We use @msg->status to signal whether there was
	 * error in transfer and @msg->state is used to hold pointer to the
	 * current transfer (or %NULL if no active current transfer).
	 */
	msg->state = NULL;
	msg->status = 0;
	msg->actual_length = 0;

	spin_lock_irqsave(&espi->lock, flags);
	if (!espi->running) {
		spin_unlock_irqrestore(&espi->lock, flags);
		return -ESHUTDOWN;
	}
	list_add_tail(&msg->queue, &espi->msg_queue);
	queue_work(espi->wq, &espi->msg_work);
	spin_unlock_irqrestore(&espi->lock, flags);

	return 0;
}

/**
 * ep93xx_spi_cleanup() - cleans up master controller specific state
 * @spi: SPI device to cleanup
 *
 * This function releases master controller specific state for given @spi
 * device.
 */
static void ep93xx_spi_cleanup(struct spi_device *spi)
{
	struct ep93xx_spi_chip *chip;

	chip = spi_get_ctldata(spi);
	if (chip) {
		if (chip->ops && chip->ops->cleanup)
			chip->ops->cleanup(spi);
		spi_set_ctldata(spi, NULL);
		kfree(chip);
	}
}

/**
 * ep93xx_spi_chip_setup() - configures hardware according to given @chip
 * @espi: ep93xx SPI controller struct
 * @chip: chip specific settings
 *
 * This function sets up the actual hardware registers with settings given in
 * @chip. Note that no validation is done so make sure that callers validate
 * settings before calling this.
 */
static void ep93xx_spi_chip_setup(const struct ep93xx_spi *espi,
				  const struct ep93xx_spi_chip *chip)
{
	u16 cr0;

	cr0 = chip->div_scr << SSPCR0_SCR_SHIFT;
	cr0 |= (chip->spi->mode & (SPI_CPHA|SPI_CPOL)) << SSPCR0_MODE_SHIFT;
	cr0 |= chip->dss;

	dev_dbg(&espi->pdev->dev, "setup: mode %d, cpsr %d, scr %d, dss %d\n",
		chip->spi->mode, chip->div_cpsr, chip->div_scr, chip->dss);
	dev_dbg(&espi->pdev->dev, "setup: cr0 %#x", cr0);

	ep93xx_spi_write_u8(espi, SSPCPSR, chip->div_cpsr);
	ep93xx_spi_write_u16(espi, SSPCR0, cr0);
}

static inline int bits_per_word(const struct ep93xx_spi *espi)
{
	struct spi_message *msg = espi->current_msg;
	struct spi_transfer *t = msg->state;

	return t->bits_per_word ? t->bits_per_word : msg->spi->bits_per_word;
}

static void ep93xx_do_write(struct ep93xx_spi *espi, struct spi_transfer *t)
{
	if (bits_per_word(espi) > 8) {
		u16 tx_val = 0;

		if (t->tx_buf)
			tx_val = ((u16 *)t->tx_buf)[espi->tx];
		ep93xx_spi_write_u16(espi, SSPDR, tx_val);
		espi->tx += sizeof(tx_val);
	} else {
		u8 tx_val = 0;

		if (t->tx_buf)
			tx_val = ((u8 *)t->tx_buf)[espi->tx];
		ep93xx_spi_write_u8(espi, SSPDR, tx_val);
		espi->tx += sizeof(tx_val);
	}
}

static void ep93xx_do_read(struct ep93xx_spi *espi, struct spi_transfer *t)
{
	if (bits_per_word(espi) > 8) {
		u16 rx_val;

		rx_val = ep93xx_spi_read_u16(espi, SSPDR);
		if (t->rx_buf)
			((u16 *)t->rx_buf)[espi->rx] = rx_val;
		espi->rx += sizeof(rx_val);
	} else {
		u8 rx_val;

		rx_val = ep93xx_spi_read_u8(espi, SSPDR);
		if (t->rx_buf)
			((u8 *)t->rx_buf)[espi->rx] = rx_val;
		espi->rx += sizeof(rx_val);
	}
}

/**
 * ep93xx_spi_read_write() - perform next RX/TX transfer
 * @espi: ep93xx SPI controller struct
 *
 * This function transfers next bytes (or half-words) to/from RX/TX FIFOs. If
 * called several times, the whole transfer will be completed. Returns
 * %-EINPROGRESS when current transfer was not yet completed otherwise %0.
 *
 * When this function is finished, RX FIFO should be empty and TX FIFO should be
 * full.
 */
static int ep93xx_spi_read_write(struct ep93xx_spi *espi)
{
	struct spi_message *msg = espi->current_msg;
	struct spi_transfer *t = msg->state;

	/* read as long as RX FIFO has frames in it */
	while ((ep93xx_spi_read_u8(espi, SSPSR) & SSPSR_RNE)) {
		ep93xx_do_read(espi, t);
		espi->fifo_level--;
	}

	/* write as long as TX FIFO has room */
	while (espi->fifo_level < SPI_FIFO_SIZE && espi->tx < t->len) {
		ep93xx_do_write(espi, t);
		espi->fifo_level++;
	}

	if (espi->rx == t->len)
		return 0;

	return -EINPROGRESS;
}

static void ep93xx_spi_pio_transfer(struct ep93xx_spi *espi)
{
	/*
	 * Now everything is set up for the current transfer. We prime the TX
	 * FIFO, enable interrupts, and wait for the transfer to complete.
	 */
	if (ep93xx_spi_read_write(espi)) {
		ep93xx_spi_enable_interrupts(espi);
		wait_for_completion(&espi->wait);
	}
}

/**
 * ep93xx_spi_dma_prepare() - prepares a DMA transfer
 * @espi: ep93xx SPI controller struct
 * @dir: DMA transfer direction
 *
 * Function configures the DMA, maps the buffer and prepares the DMA
 * descriptor. Returns a valid DMA descriptor in case of success and ERR_PTR
 * in case of failure.
 */
static struct dma_async_tx_descriptor *
ep93xx_spi_dma_prepare(struct ep93xx_spi *espi, enum dma_data_direction dir)
{
	struct spi_transfer *t = espi->current_msg->state;
	struct dma_async_tx_descriptor *txd;
	enum dma_slave_buswidth buswidth;
	struct dma_slave_config conf;
	struct scatterlist *sg;
	struct sg_table *sgt;
	struct dma_chan *chan;
	const void *buf, *pbuf;
	size_t len = t->len;
	int i, ret, nents;

	if (bits_per_word(espi) > 8)
		buswidth = DMA_SLAVE_BUSWIDTH_2_BYTES;
	else
		buswidth = DMA_SLAVE_BUSWIDTH_1_BYTE;

	memset(&conf, 0, sizeof(conf));
	conf.direction = dir;

	if (dir == DMA_FROM_DEVICE) {
		chan = espi->dma_rx;
		buf = t->rx_buf;
		sgt = &espi->rx_sgt;

		conf.src_addr = espi->sspdr_phys;
		conf.src_addr_width = buswidth;
	} else {
		chan = espi->dma_tx;
		buf = t->tx_buf;
		sgt = &espi->tx_sgt;

		conf.dst_addr = espi->sspdr_phys;
		conf.dst_addr_width = buswidth;
	}

	ret = dmaengine_slave_config(chan, &conf);
	if (ret)
		return ERR_PTR(ret);

	/*
	 * We need to split the transfer into PAGE_SIZE'd chunks. This is
	 * because we are using @espi->zeropage to provide a zero RX buffer
	 * for the TX transfers and we have only allocated one page for that.
	 *
	 * For performance reasons we allocate a new sg_table only when
	 * needed. Otherwise we will re-use the current one. Eventually the
	 * last sg_table is released in ep93xx_spi_release_dma().
	 */

	nents = DIV_ROUND_UP(len, PAGE_SIZE);
	if (nents != sgt->nents) {
		sg_free_table(sgt);

		ret = sg_alloc_table(sgt, nents, GFP_KERNEL);
		if (ret)
			return ERR_PTR(ret);
	}

	pbuf = buf;
	for_each_sg(sgt->sgl, sg, sgt->nents, i) {
		size_t bytes = min_t(size_t, len, PAGE_SIZE);

		if (buf) {
			sg_set_page(sg, virt_to_page(pbuf), bytes,
				    offset_in_page(pbuf));
		} else {
			sg_set_page(sg, virt_to_page(espi->zeropage),
				    bytes, 0);
		}

		pbuf += bytes;
		len -= bytes;
	}

	if (WARN_ON(len)) {
		dev_warn(&espi->pdev->dev, "len = %d expected 0!", len);
		return ERR_PTR(-EINVAL);
	}

	nents = dma_map_sg(chan->device->dev, sgt->sgl, sgt->nents, dir);
	if (!nents)
		return ERR_PTR(-ENOMEM);

	txd = dmaengine_prep_slave_sg(chan, sgt->sgl, nents,
					slave_dirn, DMA_CTRL_ACK);
	if (!txd) {
		dma_unmap_sg(chan->device->dev, sgt->sgl, sgt->nents, dir);
		return ERR_PTR(-ENOMEM);
	}
	return txd;
}

/**
 * ep93xx_spi_dma_finish() - finishes with a DMA transfer
 * @espi: ep93xx SPI controller struct
 * @dir: DMA transfer direction
 *
 * Function finishes with the DMA transfer. After this, the DMA buffer is
 * unmapped.
 */
static void ep93xx_spi_dma_finish(struct ep93xx_spi *espi,
				  enum dma_data_direction dir)
{
	struct dma_chan *chan;
	struct sg_table *sgt;

	if (dir == DMA_FROM_DEVICE) {
		chan = espi->dma_rx;
		sgt = &espi->rx_sgt;
	} else {
		chan = espi->dma_tx;
		sgt = &espi->tx_sgt;
	}

	dma_unmap_sg(chan->device->dev, sgt->sgl, sgt->nents, dir);
}

static void ep93xx_spi_dma_callback(void *callback_param)
{
	complete(callback_param);
}

static void ep93xx_spi_dma_transfer(struct ep93xx_spi *espi)
{
	struct spi_message *msg = espi->current_msg;
	struct dma_async_tx_descriptor *rxd, *txd;

	rxd = ep93xx_spi_dma_prepare(espi, DMA_FROM_DEVICE);
	if (IS_ERR(rxd)) {
		dev_err(&espi->pdev->dev, "DMA RX failed: %ld\n", PTR_ERR(rxd));
		msg->status = PTR_ERR(rxd);
		return;
	}

	txd = ep93xx_spi_dma_prepare(espi, DMA_TO_DEVICE);
	if (IS_ERR(txd)) {
		ep93xx_spi_dma_finish(espi, DMA_FROM_DEVICE);
		dev_err(&espi->pdev->dev, "DMA TX failed: %ld\n", PTR_ERR(rxd));
		msg->status = PTR_ERR(txd);
		return;
	}

	/* We are ready when RX is done */
	rxd->callback = ep93xx_spi_dma_callback;
	rxd->callback_param = &espi->wait;

	/* Now submit both descriptors and wait while they finish */
	dmaengine_submit(rxd);
	dmaengine_submit(txd);

	dma_async_issue_pending(espi->dma_rx);
	dma_async_issue_pending(espi->dma_tx);

	wait_for_completion(&espi->wait);

	ep93xx_spi_dma_finish(espi, DMA_TO_DEVICE);
	ep93xx_spi_dma_finish(espi, DMA_FROM_DEVICE);
}

/**
 * ep93xx_spi_process_transfer() - processes one SPI transfer
 * @espi: ep93xx SPI controller struct
 * @msg: current message
 * @t: transfer to process
 *
 * This function processes one SPI transfer given in @t. Function waits until
 * transfer is complete (may sleep) and updates @msg->status based on whether
 * transfer was successfully processed or not.
 */
static void ep93xx_spi_process_transfer(struct ep93xx_spi *espi,
					struct spi_message *msg,
					struct spi_transfer *t)
{
	struct ep93xx_spi_chip *chip = spi_get_ctldata(msg->spi);

	msg->state = t;

	/*
	 * Handle any transfer specific settings if needed. We use
	 * temporary chip settings here and restore original later when
	 * the transfer is finished.
	 */
	if (t->speed_hz || t->bits_per_word) {
		struct ep93xx_spi_chip tmp_chip = *chip;

		if (t->speed_hz) {
			int err;

			err = ep93xx_spi_calc_divisors(espi, &tmp_chip,
						       t->speed_hz);
			if (err) {
				dev_err(&espi->pdev->dev,
					"failed to adjust speed\n");
				msg->status = err;
				return;
			}
		}

		if (t->bits_per_word)
			tmp_chip.dss = bits_per_word_to_dss(t->bits_per_word);

		/*
		 * Set up temporary new hw settings for this transfer.
		 */
		ep93xx_spi_chip_setup(espi, &tmp_chip);
	}

	espi->rx = 0;
	espi->tx = 0;

	/*
	 * There is no point of setting up DMA for the transfers which will
	 * fit into the FIFO and can be transferred with a single interrupt.
	 * So in these cases we will be using PIO and don't bother for DMA.
	 */
	if (espi->dma_rx && t->len > SPI_FIFO_SIZE)
		ep93xx_spi_dma_transfer(espi);
	else
		ep93xx_spi_pio_transfer(espi);

	/*
	 * In case of error during transmit, we bail out from processing
	 * the message.
	 */
	if (msg->status)
		return;

	msg->actual_length += t->len;

	/*
	 * After this transfer is finished, perform any possible
	 * post-transfer actions requested by the protocol driver.
	 */
	if (t->delay_usecs) {
		set_current_state(TASK_UNINTERRUPTIBLE);
		schedule_timeout(usecs_to_jiffies(t->delay_usecs));
	}
	if (t->cs_change) {
		if (!list_is_last(&t->transfer_list, &msg->transfers)) {
			/*
			 * In case protocol driver is asking us to drop the
			 * chipselect briefly, we let the scheduler to handle
			 * any "delay" here.
			 */
			ep93xx_spi_cs_control(msg->spi, false);
			cond_resched();
			ep93xx_spi_cs_control(msg->spi, true);
		}
	}

	if (t->speed_hz || t->bits_per_word)
		ep93xx_spi_chip_setup(espi, chip);
}

/*
 * ep93xx_spi_process_message() - process one SPI message
 * @espi: ep93xx SPI controller struct
 * @msg: message to process
 *
 * This function processes a single SPI message. We go through all transfers in
 * the message and pass them to ep93xx_spi_process_transfer(). Chipselect is
 * asserted during the whole message (unless per transfer cs_change is set).
 *
 * @msg->status contains %0 in case of success or negative error code in case of
 * failure.
 */
static void ep93xx_spi_process_message(struct ep93xx_spi *espi,
				       struct spi_message *msg)
{
	unsigned long timeout;
	struct spi_transfer *t;
	int err;

	/*
	 * Enable the SPI controller and its clock.
	 */
	err = ep93xx_spi_enable(espi);
	if (err) {
		dev_err(&espi->pdev->dev, "failed to enable SPI controller\n");
		msg->status = err;
		return;
	}

	/*
	 * Just to be sure: flush any data from RX FIFO.
	 */
	timeout = jiffies + msecs_to_jiffies(SPI_TIMEOUT);
	while (ep93xx_spi_read_u16(espi, SSPSR) & SSPSR_RNE) {
		if (time_after(jiffies, timeout)) {
			dev_warn(&espi->pdev->dev,
				 "timeout while flushing RX FIFO\n");
			msg->status = -ETIMEDOUT;
			return;
		}
		ep93xx_spi_read_u16(espi, SSPDR);
	}

	/*
	 * We explicitly handle FIFO level. This way we don't have to check TX
	 * FIFO status using %SSPSR_TNF bit which may cause RX FIFO overruns.
	 */
	espi->fifo_level = 0;

	/*
	 * Update SPI controller registers according to spi device and assert
	 * the chipselect.
	 */
	ep93xx_spi_chip_setup(espi, spi_get_ctldata(msg->spi));
	ep93xx_spi_cs_control(msg->spi, true);

	list_for_each_entry(t, &msg->transfers, transfer_list) {
		ep93xx_spi_process_transfer(espi, msg, t);
		if (msg->status)
			break;
	}

	/*
	 * Now the whole message is transferred (or failed for some reason). We
	 * deselect the device and disable the SPI controller.
	 */
	ep93xx_spi_cs_control(msg->spi, false);
	ep93xx_spi_disable(espi);
}

#define work_to_espi(work) (container_of((work), struct ep93xx_spi, msg_work))

/**
 * ep93xx_spi_work() - EP93xx SPI workqueue worker function
 * @work: work struct
 *
 * Workqueue worker function. This function is called when there are new
 * SPI messages to be processed. Message is taken out from the queue and then
 * passed to ep93xx_spi_process_message().
 *
 * After message is transferred, protocol driver is notified by calling
 * @msg->complete(). In case of error, @msg->status is set to negative error
 * number, otherwise it contains zero (and @msg->actual_length is updated).
 */
static void ep93xx_spi_work(struct work_struct *work)
{
	struct ep93xx_spi *espi = work_to_espi(work);
	struct spi_message *msg;

	spin_lock_irq(&espi->lock);
	if (!espi->running || espi->current_msg ||
		list_empty(&espi->msg_queue)) {
		spin_unlock_irq(&espi->lock);
		return;
	}
	msg = list_first_entry(&espi->msg_queue, struct spi_message, queue);
	list_del_init(&msg->queue);
	espi->current_msg = msg;
	spin_unlock_irq(&espi->lock);

	ep93xx_spi_process_message(espi, msg);

	/*
	 * Update the current message and re-schedule ourselves if there are
	 * more messages in the queue.
	 */
	spin_lock_irq(&espi->lock);
	espi->current_msg = NULL;
	if (espi->running && !list_empty(&espi->msg_queue))
		queue_work(espi->wq, &espi->msg_work);
	spin_unlock_irq(&espi->lock);

	/* notify the protocol driver that we are done with this message */
	msg->complete(msg->context);
}

static irqreturn_t ep93xx_spi_interrupt(int irq, void *dev_id)
{
	struct ep93xx_spi *espi = dev_id;
	u8 irq_status = ep93xx_spi_read_u8(espi, SSPIIR);

	/*
	 * If we got ROR (receive overrun) interrupt we know that something is
	 * wrong. Just abort the message.
	 */
	if (unlikely(irq_status & SSPIIR_RORIS)) {
		/* clear the overrun interrupt */
		ep93xx_spi_write_u8(espi, SSPICR, 0);
		dev_warn(&espi->pdev->dev,
			 "receive overrun, aborting the message\n");
		espi->current_msg->status = -EIO;
	} else {
		/*
		 * Interrupt is either RX (RIS) or TX (TIS). For both cases we
		 * simply execute next data transfer.
		 */
		if (ep93xx_spi_read_write(espi)) {
			/*
			 * In normal case, there still is some processing left
			 * for current transfer. Let's wait for the next
			 * interrupt then.
			 */
			return IRQ_HANDLED;
		}
	}

	/*
	 * Current transfer is finished, either with error or with success. In
	 * any case we disable interrupts and notify the worker to handle
	 * any post-processing of the message.
	 */
	ep93xx_spi_disable_interrupts(espi);
	complete(&espi->wait);
	return IRQ_HANDLED;
}

static bool ep93xx_spi_dma_filter(struct dma_chan *chan, void *filter_param)
{
	if (ep93xx_dma_chan_is_m2p(chan))
		return false;

	chan->private = filter_param;
	return true;
}

static int ep93xx_spi_setup_dma(struct ep93xx_spi *espi)
{
	dma_cap_mask_t mask;
	int ret;

	espi->zeropage = (void *)get_zeroed_page(GFP_KERNEL);
	if (!espi->zeropage)
		return -ENOMEM;

	dma_cap_zero(mask);
	dma_cap_set(DMA_SLAVE, mask);

	espi->dma_rx_data.port = EP93XX_DMA_SSP;
	espi->dma_rx_data.direction = DMA_FROM_DEVICE;
	espi->dma_rx_data.name = "ep93xx-spi-rx";

	espi->dma_rx = dma_request_channel(mask, ep93xx_spi_dma_filter,
					   &espi->dma_rx_data);
	if (!espi->dma_rx) {
		ret = -ENODEV;
		goto fail_free_page;
	}

	espi->dma_tx_data.port = EP93XX_DMA_SSP;
	espi->dma_tx_data.direction = DMA_TO_DEVICE;
	espi->dma_tx_data.name = "ep93xx-spi-tx";

	espi->dma_tx = dma_request_channel(mask, ep93xx_spi_dma_filter,
					   &espi->dma_tx_data);
	if (!espi->dma_tx) {
		ret = -ENODEV;
		goto fail_release_rx;
	}

	return 0;

fail_release_rx:
	dma_release_channel(espi->dma_rx);
	espi->dma_rx = NULL;
fail_free_page:
	free_page((unsigned long)espi->zeropage);

	return ret;
}

static void ep93xx_spi_release_dma(struct ep93xx_spi *espi)
{
	if (espi->dma_rx) {
		dma_release_channel(espi->dma_rx);
		sg_free_table(&espi->rx_sgt);
	}
	if (espi->dma_tx) {
		dma_release_channel(espi->dma_tx);
		sg_free_table(&espi->tx_sgt);
	}

	if (espi->zeropage)
		free_page((unsigned long)espi->zeropage);
}

static int __init ep93xx_spi_probe(struct platform_device *pdev)
{
	struct spi_master *master;
	struct ep93xx_spi_info *info;
	struct ep93xx_spi *espi;
	struct resource *res;
	int error;

	info = pdev->dev.platform_data;

	master = spi_alloc_master(&pdev->dev, sizeof(*espi));
	if (!master) {
		dev_err(&pdev->dev, "failed to allocate spi master\n");
		return -ENOMEM;
	}

	master->setup = ep93xx_spi_setup;
	master->transfer = ep93xx_spi_transfer;
	master->cleanup = ep93xx_spi_cleanup;
	master->bus_num = pdev->id;
	master->num_chipselect = info->num_chipselect;
	master->mode_bits = SPI_CPOL | SPI_CPHA | SPI_CS_HIGH;

	platform_set_drvdata(pdev, master);

	espi = spi_master_get_devdata(master);

	espi->clk = clk_get(&pdev->dev, NULL);
	if (IS_ERR(espi->clk)) {
		dev_err(&pdev->dev, "unable to get spi clock\n");
		error = PTR_ERR(espi->clk);
		goto fail_release_master;
	}

	spin_lock_init(&espi->lock);
	init_completion(&espi->wait);

	/*
	 * Calculate maximum and minimum supported clock rates
	 * for the controller.
	 */
	espi->max_rate = clk_get_rate(espi->clk) / 2;
	espi->min_rate = clk_get_rate(espi->clk) / (254 * 256);
	espi->pdev = pdev;

	espi->irq = platform_get_irq(pdev, 0);
	if (espi->irq < 0) {
		error = -EBUSY;
		dev_err(&pdev->dev, "failed to get irq resources\n");
		goto fail_put_clock;
	}

	res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
	if (!res) {
		dev_err(&pdev->dev, "unable to get iomem resource\n");
		error = -ENODEV;
		goto fail_put_clock;
	}

	res = request_mem_region(res->start, resource_size(res), pdev->name);
	if (!res) {
		dev_err(&pdev->dev, "unable to request iomem resources\n");
		error = -EBUSY;
		goto fail_put_clock;
	}

	espi->sspdr_phys = res->start + SSPDR;
	espi->regs_base = ioremap(res->start, resource_size(res));
	if (!espi->regs_base) {
		dev_err(&pdev->dev, "failed to map resources\n");
		error = -ENODEV;
		goto fail_free_mem;
	}

	error = request_irq(espi->irq, ep93xx_spi_interrupt, 0,
			    "ep93xx-spi", espi);
	if (error) {
		dev_err(&pdev->dev, "failed to request irq\n");
		goto fail_unmap_regs;
	}

	if (info->use_dma && ep93xx_spi_setup_dma(espi))
		dev_warn(&pdev->dev, "DMA setup failed. Falling back to PIO\n");

	espi->wq = create_singlethread_workqueue("ep93xx_spid");
	if (!espi->wq) {
		dev_err(&pdev->dev, "unable to create workqueue\n");
		goto fail_free_dma;
	}
	INIT_WORK(&espi->msg_work, ep93xx_spi_work);
	INIT_LIST_HEAD(&espi->msg_queue);
	espi->running = true;

	/* make sure that the hardware is disabled */
	ep93xx_spi_write_u8(espi, SSPCR1, 0);

	error = spi_register_master(master);
	if (error) {
		dev_err(&pdev->dev, "failed to register SPI master\n");
		goto fail_free_queue;
	}

	dev_info(&pdev->dev, "EP93xx SPI Controller at 0x%08lx irq %d\n",
		 (unsigned long)res->start, espi->irq);

	return 0;

fail_free_queue:
	destroy_workqueue(espi->wq);
fail_free_dma:
	ep93xx_spi_release_dma(espi);
	free_irq(espi->irq, espi);
fail_unmap_regs:
	iounmap(espi->regs_base);
fail_free_mem:
	release_mem_region(res->start, resource_size(res));
fail_put_clock:
	clk_put(espi->clk);
fail_release_master:
	spi_master_put(master);
	platform_set_drvdata(pdev, NULL);

	return error;
}

static int __exit ep93xx_spi_remove(struct platform_device *pdev)
{
	struct spi_master *master = platform_get_drvdata(pdev);
	struct ep93xx_spi *espi = spi_master_get_devdata(master);
	struct resource *res;

	spin_lock_irq(&espi->lock);
	espi->running = false;
	spin_unlock_irq(&espi->lock);

	destroy_workqueue(espi->wq);

	/*
	 * Complete remaining messages with %-ESHUTDOWN status.
	 */
	spin_lock_irq(&espi->lock);
	while (!list_empty(&espi->msg_queue)) {
		struct spi_message *msg;

		msg = list_first_entry(&espi->msg_queue,
				       struct spi_message, queue);
		list_del_init(&msg->queue);
		msg->status = -ESHUTDOWN;
		spin_unlock_irq(&espi->lock);
		msg->complete(msg->context);
		spin_lock_irq(&espi->lock);
	}
	spin_unlock_irq(&espi->lock);

	ep93xx_spi_release_dma(espi);
	free_irq(espi->irq, espi);
	iounmap(espi->regs_base);
	res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
	release_mem_region(res->start, resource_size(res));
	clk_put(espi->clk);
	platform_set_drvdata(pdev, NULL);

	spi_unregister_master(master);
	return 0;
}

static struct platform_driver ep93xx_spi_driver = {
	.driver		= {
		.name	= "ep93xx-spi",
		.owner	= THIS_MODULE,
	},
	.remove		= __exit_p(ep93xx_spi_remove),
};

static int __init ep93xx_spi_init(void)
{
	return platform_driver_probe(&ep93xx_spi_driver, ep93xx_spi_probe);
}
module_init(ep93xx_spi_init);

static void __exit ep93xx_spi_exit(void)
{
	platform_driver_unregister(&ep93xx_spi_driver);
}
module_exit(ep93xx_spi_exit);

MODULE_DESCRIPTION("EP93xx SPI Controller driver");
MODULE_AUTHOR("Mika Westerberg <mika.westerberg@iki.fi>");
MODULE_LICENSE("GPL");
MODULE_ALIAS("platform:ep93xx-spi");