summaryrefslogtreecommitdiff
path: root/drivers/dma/stm32-dma.c
blob: e4cbe38d1b83a7651dc0845dafbceee140eb192c (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
1218
1219
1220
1221
1222
1223
1224
1225
1226
1227
1228
1229
1230
1231
1232
1233
1234
1235
1236
1237
1238
1239
1240
1241
1242
1243
1244
1245
1246
1247
1248
1249
1250
1251
1252
1253
1254
1255
1256
1257
1258
1259
1260
1261
1262
1263
1264
1265
1266
1267
1268
1269
1270
1271
1272
1273
1274
1275
1276
1277
1278
1279
1280
1281
1282
1283
1284
1285
1286
1287
1288
1289
1290
1291
1292
1293
1294
1295
1296
1297
1298
1299
1300
1301
1302
1303
1304
1305
1306
1307
1308
1309
1310
1311
1312
1313
1314
1315
1316
1317
1318
1319
1320
1321
1322
1323
1324
1325
1326
1327
1328
1329
1330
1331
1332
1333
1334
1335
1336
1337
1338
1339
1340
1341
1342
1343
1344
1345
1346
1347
1348
1349
1350
1351
1352
1353
1354
1355
1356
1357
1358
1359
1360
1361
1362
1363
1364
1365
1366
1367
1368
1369
1370
1371
1372
1373
1374
1375
1376
1377
1378
1379
1380
1381
1382
1383
1384
1385
1386
1387
1388
1389
1390
1391
1392
1393
1394
1395
1396
1397
1398
1399
1400
1401
1402
1403
1404
1405
1406
1407
1408
1409
1410
1411
1412
1413
1414
1415
1416
1417
1418
1419
1420
1421
1422
1423
1424
1425
1426
1427
1428
1429
1430
1431
1432
1433
1434
1435
1436
1437
1438
1439
1440
1441
1442
1443
1444
1445
1446
1447
1448
1449
1450
1451
1452
1453
// SPDX-License-Identifier: GPL-2.0-only
/*
 * Driver for STM32 DMA controller
 *
 * Inspired by dma-jz4740.c and tegra20-apb-dma.c
 *
 * Copyright (C) M'boumba Cedric Madianga 2015
 * Author: M'boumba Cedric Madianga <cedric.madianga@gmail.com>
 *         Pierre-Yves Mordret <pierre-yves.mordret@st.com>
 */

#include <linux/clk.h>
#include <linux/delay.h>
#include <linux/dmaengine.h>
#include <linux/dma-mapping.h>
#include <linux/err.h>
#include <linux/init.h>
#include <linux/jiffies.h>
#include <linux/list.h>
#include <linux/module.h>
#include <linux/of.h>
#include <linux/of_device.h>
#include <linux/of_dma.h>
#include <linux/platform_device.h>
#include <linux/pm_runtime.h>
#include <linux/reset.h>
#include <linux/sched.h>
#include <linux/slab.h>

#include "virt-dma.h"

#define STM32_DMA_LISR			0x0000 /* DMA Low Int Status Reg */
#define STM32_DMA_HISR			0x0004 /* DMA High Int Status Reg */
#define STM32_DMA_LIFCR			0x0008 /* DMA Low Int Flag Clear Reg */
#define STM32_DMA_HIFCR			0x000c /* DMA High Int Flag Clear Reg */
#define STM32_DMA_TCI			BIT(5) /* Transfer Complete Interrupt */
#define STM32_DMA_HTI			BIT(4) /* Half Transfer Interrupt */
#define STM32_DMA_TEI			BIT(3) /* Transfer Error Interrupt */
#define STM32_DMA_DMEI			BIT(2) /* Direct Mode Error Interrupt */
#define STM32_DMA_FEI			BIT(0) /* FIFO Error Interrupt */
#define STM32_DMA_MASKI			(STM32_DMA_TCI \
					 | STM32_DMA_TEI \
					 | STM32_DMA_DMEI \
					 | STM32_DMA_FEI)

/* DMA Stream x Configuration Register */
#define STM32_DMA_SCR(x)		(0x0010 + 0x18 * (x)) /* x = 0..7 */
#define STM32_DMA_SCR_REQ(n)		((n & 0x7) << 25)
#define STM32_DMA_SCR_MBURST_MASK	GENMASK(24, 23)
#define STM32_DMA_SCR_MBURST(n)	        ((n & 0x3) << 23)
#define STM32_DMA_SCR_PBURST_MASK	GENMASK(22, 21)
#define STM32_DMA_SCR_PBURST(n)	        ((n & 0x3) << 21)
#define STM32_DMA_SCR_PL_MASK		GENMASK(17, 16)
#define STM32_DMA_SCR_PL(n)		((n & 0x3) << 16)
#define STM32_DMA_SCR_MSIZE_MASK	GENMASK(14, 13)
#define STM32_DMA_SCR_MSIZE(n)		((n & 0x3) << 13)
#define STM32_DMA_SCR_PSIZE_MASK	GENMASK(12, 11)
#define STM32_DMA_SCR_PSIZE(n)		((n & 0x3) << 11)
#define STM32_DMA_SCR_PSIZE_GET(n)	((n & STM32_DMA_SCR_PSIZE_MASK) >> 11)
#define STM32_DMA_SCR_DIR_MASK		GENMASK(7, 6)
#define STM32_DMA_SCR_DIR(n)		((n & 0x3) << 6)
#define STM32_DMA_SCR_CT		BIT(19) /* Target in double buffer */
#define STM32_DMA_SCR_DBM		BIT(18) /* Double Buffer Mode */
#define STM32_DMA_SCR_PINCOS		BIT(15) /* Peripheral inc offset size */
#define STM32_DMA_SCR_MINC		BIT(10) /* Memory increment mode */
#define STM32_DMA_SCR_PINC		BIT(9) /* Peripheral increment mode */
#define STM32_DMA_SCR_CIRC		BIT(8) /* Circular mode */
#define STM32_DMA_SCR_PFCTRL		BIT(5) /* Peripheral Flow Controller */
#define STM32_DMA_SCR_TCIE		BIT(4) /* Transfer Complete Int Enable
						*/
#define STM32_DMA_SCR_TEIE		BIT(2) /* Transfer Error Int Enable */
#define STM32_DMA_SCR_DMEIE		BIT(1) /* Direct Mode Err Int Enable */
#define STM32_DMA_SCR_EN		BIT(0) /* Stream Enable */
#define STM32_DMA_SCR_CFG_MASK		(STM32_DMA_SCR_PINC \
					| STM32_DMA_SCR_MINC \
					| STM32_DMA_SCR_PINCOS \
					| STM32_DMA_SCR_PL_MASK)
#define STM32_DMA_SCR_IRQ_MASK		(STM32_DMA_SCR_TCIE \
					| STM32_DMA_SCR_TEIE \
					| STM32_DMA_SCR_DMEIE)

/* DMA Stream x number of data register */
#define STM32_DMA_SNDTR(x)		(0x0014 + 0x18 * (x))

/* DMA stream peripheral address register */
#define STM32_DMA_SPAR(x)		(0x0018 + 0x18 * (x))

/* DMA stream x memory 0 address register */
#define STM32_DMA_SM0AR(x)		(0x001c + 0x18 * (x))

/* DMA stream x memory 1 address register */
#define STM32_DMA_SM1AR(x)		(0x0020 + 0x18 * (x))

/* DMA stream x FIFO control register */
#define STM32_DMA_SFCR(x)		(0x0024 + 0x18 * (x))
#define STM32_DMA_SFCR_FTH_MASK		GENMASK(1, 0)
#define STM32_DMA_SFCR_FTH(n)		(n & STM32_DMA_SFCR_FTH_MASK)
#define STM32_DMA_SFCR_FEIE		BIT(7) /* FIFO error interrupt enable */
#define STM32_DMA_SFCR_DMDIS		BIT(2) /* Direct mode disable */
#define STM32_DMA_SFCR_MASK		(STM32_DMA_SFCR_FEIE \
					| STM32_DMA_SFCR_DMDIS)

/* DMA direction */
#define STM32_DMA_DEV_TO_MEM		0x00
#define	STM32_DMA_MEM_TO_DEV		0x01
#define	STM32_DMA_MEM_TO_MEM		0x02

/* DMA priority level */
#define STM32_DMA_PRIORITY_LOW		0x00
#define STM32_DMA_PRIORITY_MEDIUM	0x01
#define STM32_DMA_PRIORITY_HIGH		0x02
#define STM32_DMA_PRIORITY_VERY_HIGH	0x03

/* DMA FIFO threshold selection */
#define STM32_DMA_FIFO_THRESHOLD_1QUARTERFULL		0x00
#define STM32_DMA_FIFO_THRESHOLD_HALFFULL		0x01
#define STM32_DMA_FIFO_THRESHOLD_3QUARTERSFULL		0x02
#define STM32_DMA_FIFO_THRESHOLD_FULL			0x03

#define STM32_DMA_MAX_DATA_ITEMS	0xffff
/*
 * Valid transfer starts from @0 to @0xFFFE leading to unaligned scatter
 * gather at boundary. Thus it's safer to round down this value on FIFO
 * size (16 Bytes)
 */
#define STM32_DMA_ALIGNED_MAX_DATA_ITEMS	\
	ALIGN_DOWN(STM32_DMA_MAX_DATA_ITEMS, 16)
#define STM32_DMA_MAX_CHANNELS		0x08
#define STM32_DMA_MAX_REQUEST_ID	0x08
#define STM32_DMA_MAX_DATA_PARAM	0x03
#define STM32_DMA_FIFO_SIZE		16	/* FIFO is 16 bytes */
#define STM32_DMA_MIN_BURST		4
#define STM32_DMA_MAX_BURST		16

/* DMA Features */
#define STM32_DMA_THRESHOLD_FTR_MASK	GENMASK(1, 0)
#define STM32_DMA_THRESHOLD_FTR_GET(n)	((n) & STM32_DMA_THRESHOLD_FTR_MASK)

enum stm32_dma_width {
	STM32_DMA_BYTE,
	STM32_DMA_HALF_WORD,
	STM32_DMA_WORD,
};

enum stm32_dma_burst_size {
	STM32_DMA_BURST_SINGLE,
	STM32_DMA_BURST_INCR4,
	STM32_DMA_BURST_INCR8,
	STM32_DMA_BURST_INCR16,
};

/**
 * struct stm32_dma_cfg - STM32 DMA custom configuration
 * @channel_id: channel ID
 * @request_line: DMA request
 * @stream_config: 32bit mask specifying the DMA channel configuration
 * @features: 32bit mask specifying the DMA Feature list
 */
struct stm32_dma_cfg {
	u32 channel_id;
	u32 request_line;
	u32 stream_config;
	u32 features;
};

struct stm32_dma_chan_reg {
	u32 dma_lisr;
	u32 dma_hisr;
	u32 dma_lifcr;
	u32 dma_hifcr;
	u32 dma_scr;
	u32 dma_sndtr;
	u32 dma_spar;
	u32 dma_sm0ar;
	u32 dma_sm1ar;
	u32 dma_sfcr;
};

struct stm32_dma_sg_req {
	u32 len;
	struct stm32_dma_chan_reg chan_reg;
};

struct stm32_dma_desc {
	struct virt_dma_desc vdesc;
	bool cyclic;
	u32 num_sgs;
	struct stm32_dma_sg_req sg_req[];
};

struct stm32_dma_chan {
	struct virt_dma_chan vchan;
	bool config_init;
	bool busy;
	u32 id;
	u32 irq;
	struct stm32_dma_desc *desc;
	u32 next_sg;
	struct dma_slave_config	dma_sconfig;
	struct stm32_dma_chan_reg chan_reg;
	u32 threshold;
	u32 mem_burst;
	u32 mem_width;
};

struct stm32_dma_device {
	struct dma_device ddev;
	void __iomem *base;
	struct clk *clk;
	struct reset_control *rst;
	bool mem2mem;
	struct stm32_dma_chan chan[STM32_DMA_MAX_CHANNELS];
};

static struct stm32_dma_device *stm32_dma_get_dev(struct stm32_dma_chan *chan)
{
	return container_of(chan->vchan.chan.device, struct stm32_dma_device,
			    ddev);
}

static struct stm32_dma_chan *to_stm32_dma_chan(struct dma_chan *c)
{
	return container_of(c, struct stm32_dma_chan, vchan.chan);
}

static struct stm32_dma_desc *to_stm32_dma_desc(struct virt_dma_desc *vdesc)
{
	return container_of(vdesc, struct stm32_dma_desc, vdesc);
}

static struct device *chan2dev(struct stm32_dma_chan *chan)
{
	return &chan->vchan.chan.dev->device;
}

static u32 stm32_dma_read(struct stm32_dma_device *dmadev, u32 reg)
{
	return readl_relaxed(dmadev->base + reg);
}

static void stm32_dma_write(struct stm32_dma_device *dmadev, u32 reg, u32 val)
{
	writel_relaxed(val, dmadev->base + reg);
}

static struct stm32_dma_desc *stm32_dma_alloc_desc(u32 num_sgs)
{
	return kzalloc(sizeof(struct stm32_dma_desc) +
		       sizeof(struct stm32_dma_sg_req) * num_sgs, GFP_NOWAIT);
}

static int stm32_dma_get_width(struct stm32_dma_chan *chan,
			       enum dma_slave_buswidth width)
{
	switch (width) {
	case DMA_SLAVE_BUSWIDTH_1_BYTE:
		return STM32_DMA_BYTE;
	case DMA_SLAVE_BUSWIDTH_2_BYTES:
		return STM32_DMA_HALF_WORD;
	case DMA_SLAVE_BUSWIDTH_4_BYTES:
		return STM32_DMA_WORD;
	default:
		dev_err(chan2dev(chan), "Dma bus width not supported\n");
		return -EINVAL;
	}
}

static enum dma_slave_buswidth stm32_dma_get_max_width(u32 buf_len,
						       u32 threshold)
{
	enum dma_slave_buswidth max_width;

	if (threshold == STM32_DMA_FIFO_THRESHOLD_FULL)
		max_width = DMA_SLAVE_BUSWIDTH_4_BYTES;
	else
		max_width = DMA_SLAVE_BUSWIDTH_2_BYTES;

	while ((buf_len < max_width  || buf_len % max_width) &&
	       max_width > DMA_SLAVE_BUSWIDTH_1_BYTE)
		max_width = max_width >> 1;

	return max_width;
}

static bool stm32_dma_fifo_threshold_is_allowed(u32 burst, u32 threshold,
						enum dma_slave_buswidth width)
{
	u32 remaining;

	if (width != DMA_SLAVE_BUSWIDTH_UNDEFINED) {
		if (burst != 0) {
			/*
			 * If number of beats fit in several whole bursts
			 * this configuration is allowed.
			 */
			remaining = ((STM32_DMA_FIFO_SIZE / width) *
				     (threshold + 1) / 4) % burst;

			if (remaining == 0)
				return true;
		} else {
			return true;
		}
	}

	return false;
}

static bool stm32_dma_is_burst_possible(u32 buf_len, u32 threshold)
{
	/*
	 * Buffer or period length has to be aligned on FIFO depth.
	 * Otherwise bytes may be stuck within FIFO at buffer or period
	 * length.
	 */
	return ((buf_len % ((threshold + 1) * 4)) == 0);
}

static u32 stm32_dma_get_best_burst(u32 buf_len, u32 max_burst, u32 threshold,
				    enum dma_slave_buswidth width)
{
	u32 best_burst = max_burst;

	if (best_burst == 1 || !stm32_dma_is_burst_possible(buf_len, threshold))
		return 0;

	while ((buf_len < best_burst * width && best_burst > 1) ||
	       !stm32_dma_fifo_threshold_is_allowed(best_burst, threshold,
						    width)) {
		if (best_burst > STM32_DMA_MIN_BURST)
			best_burst = best_burst >> 1;
		else
			best_burst = 0;
	}

	return best_burst;
}

static int stm32_dma_get_burst(struct stm32_dma_chan *chan, u32 maxburst)
{
	switch (maxburst) {
	case 0:
	case 1:
		return STM32_DMA_BURST_SINGLE;
	case 4:
		return STM32_DMA_BURST_INCR4;
	case 8:
		return STM32_DMA_BURST_INCR8;
	case 16:
		return STM32_DMA_BURST_INCR16;
	default:
		dev_err(chan2dev(chan), "Dma burst size not supported\n");
		return -EINVAL;
	}
}

static void stm32_dma_set_fifo_config(struct stm32_dma_chan *chan,
				      u32 src_burst, u32 dst_burst)
{
	chan->chan_reg.dma_sfcr &= ~STM32_DMA_SFCR_MASK;
	chan->chan_reg.dma_scr &= ~STM32_DMA_SCR_DMEIE;

	if (!src_burst && !dst_burst) {
		/* Using direct mode */
		chan->chan_reg.dma_scr |= STM32_DMA_SCR_DMEIE;
	} else {
		/* Using FIFO mode */
		chan->chan_reg.dma_sfcr |= STM32_DMA_SFCR_MASK;
	}
}

static int stm32_dma_slave_config(struct dma_chan *c,
				  struct dma_slave_config *config)
{
	struct stm32_dma_chan *chan = to_stm32_dma_chan(c);

	memcpy(&chan->dma_sconfig, config, sizeof(*config));

	chan->config_init = true;

	return 0;
}

static u32 stm32_dma_irq_status(struct stm32_dma_chan *chan)
{
	struct stm32_dma_device *dmadev = stm32_dma_get_dev(chan);
	u32 flags, dma_isr;

	/*
	 * Read "flags" from DMA_xISR register corresponding to the selected
	 * DMA channel at the correct bit offset inside that register.
	 *
	 * If (ch % 4) is 2 or 3, left shift the mask by 16 bits.
	 * If (ch % 4) is 1 or 3, additionally left shift the mask by 6 bits.
	 */

	if (chan->id & 4)
		dma_isr = stm32_dma_read(dmadev, STM32_DMA_HISR);
	else
		dma_isr = stm32_dma_read(dmadev, STM32_DMA_LISR);

	flags = dma_isr >> (((chan->id & 2) << 3) | ((chan->id & 1) * 6));

	return flags & STM32_DMA_MASKI;
}

static void stm32_dma_irq_clear(struct stm32_dma_chan *chan, u32 flags)
{
	struct stm32_dma_device *dmadev = stm32_dma_get_dev(chan);
	u32 dma_ifcr;

	/*
	 * Write "flags" to the DMA_xIFCR register corresponding to the selected
	 * DMA channel at the correct bit offset inside that register.
	 *
	 * If (ch % 4) is 2 or 3, left shift the mask by 16 bits.
	 * If (ch % 4) is 1 or 3, additionally left shift the mask by 6 bits.
	 */
	flags &= STM32_DMA_MASKI;
	dma_ifcr = flags << (((chan->id & 2) << 3) | ((chan->id & 1) * 6));

	if (chan->id & 4)
		stm32_dma_write(dmadev, STM32_DMA_HIFCR, dma_ifcr);
	else
		stm32_dma_write(dmadev, STM32_DMA_LIFCR, dma_ifcr);
}

static int stm32_dma_disable_chan(struct stm32_dma_chan *chan)
{
	struct stm32_dma_device *dmadev = stm32_dma_get_dev(chan);
	unsigned long timeout = jiffies + msecs_to_jiffies(5000);
	u32 dma_scr, id;

	id = chan->id;
	dma_scr = stm32_dma_read(dmadev, STM32_DMA_SCR(id));

	if (dma_scr & STM32_DMA_SCR_EN) {
		dma_scr &= ~STM32_DMA_SCR_EN;
		stm32_dma_write(dmadev, STM32_DMA_SCR(id), dma_scr);

		do {
			dma_scr = stm32_dma_read(dmadev, STM32_DMA_SCR(id));
			dma_scr &= STM32_DMA_SCR_EN;
			if (!dma_scr)
				break;

			if (time_after_eq(jiffies, timeout)) {
				dev_err(chan2dev(chan), "%s: timeout!\n",
					__func__);
				return -EBUSY;
			}
			cond_resched();
		} while (1);
	}

	return 0;
}

static void stm32_dma_stop(struct stm32_dma_chan *chan)
{
	struct stm32_dma_device *dmadev = stm32_dma_get_dev(chan);
	u32 dma_scr, dma_sfcr, status;
	int ret;

	/* Disable interrupts */
	dma_scr = stm32_dma_read(dmadev, STM32_DMA_SCR(chan->id));
	dma_scr &= ~STM32_DMA_SCR_IRQ_MASK;
	stm32_dma_write(dmadev, STM32_DMA_SCR(chan->id), dma_scr);
	dma_sfcr = stm32_dma_read(dmadev, STM32_DMA_SFCR(chan->id));
	dma_sfcr &= ~STM32_DMA_SFCR_FEIE;
	stm32_dma_write(dmadev, STM32_DMA_SFCR(chan->id), dma_sfcr);

	/* Disable DMA */
	ret = stm32_dma_disable_chan(chan);
	if (ret < 0)
		return;

	/* Clear interrupt status if it is there */
	status = stm32_dma_irq_status(chan);
	if (status) {
		dev_dbg(chan2dev(chan), "%s(): clearing interrupt: 0x%08x\n",
			__func__, status);
		stm32_dma_irq_clear(chan, status);
	}

	chan->busy = false;
}

static int stm32_dma_terminate_all(struct dma_chan *c)
{
	struct stm32_dma_chan *chan = to_stm32_dma_chan(c);
	unsigned long flags;
	LIST_HEAD(head);

	spin_lock_irqsave(&chan->vchan.lock, flags);

	if (chan->busy) {
		stm32_dma_stop(chan);
		chan->desc = NULL;
	}

	vchan_get_all_descriptors(&chan->vchan, &head);
	spin_unlock_irqrestore(&chan->vchan.lock, flags);
	vchan_dma_desc_free_list(&chan->vchan, &head);

	return 0;
}

static void stm32_dma_synchronize(struct dma_chan *c)
{
	struct stm32_dma_chan *chan = to_stm32_dma_chan(c);

	vchan_synchronize(&chan->vchan);
}

static void stm32_dma_dump_reg(struct stm32_dma_chan *chan)
{
	struct stm32_dma_device *dmadev = stm32_dma_get_dev(chan);
	u32 scr = stm32_dma_read(dmadev, STM32_DMA_SCR(chan->id));
	u32 ndtr = stm32_dma_read(dmadev, STM32_DMA_SNDTR(chan->id));
	u32 spar = stm32_dma_read(dmadev, STM32_DMA_SPAR(chan->id));
	u32 sm0ar = stm32_dma_read(dmadev, STM32_DMA_SM0AR(chan->id));
	u32 sm1ar = stm32_dma_read(dmadev, STM32_DMA_SM1AR(chan->id));
	u32 sfcr = stm32_dma_read(dmadev, STM32_DMA_SFCR(chan->id));

	dev_dbg(chan2dev(chan), "SCR:   0x%08x\n", scr);
	dev_dbg(chan2dev(chan), "NDTR:  0x%08x\n", ndtr);
	dev_dbg(chan2dev(chan), "SPAR:  0x%08x\n", spar);
	dev_dbg(chan2dev(chan), "SM0AR: 0x%08x\n", sm0ar);
	dev_dbg(chan2dev(chan), "SM1AR: 0x%08x\n", sm1ar);
	dev_dbg(chan2dev(chan), "SFCR:  0x%08x\n", sfcr);
}

static void stm32_dma_configure_next_sg(struct stm32_dma_chan *chan);

static void stm32_dma_start_transfer(struct stm32_dma_chan *chan)
{
	struct stm32_dma_device *dmadev = stm32_dma_get_dev(chan);
	struct virt_dma_desc *vdesc;
	struct stm32_dma_sg_req *sg_req;
	struct stm32_dma_chan_reg *reg;
	u32 status;
	int ret;

	ret = stm32_dma_disable_chan(chan);
	if (ret < 0)
		return;

	if (!chan->desc) {
		vdesc = vchan_next_desc(&chan->vchan);
		if (!vdesc)
			return;

		chan->desc = to_stm32_dma_desc(vdesc);
		chan->next_sg = 0;
	}

	if (chan->next_sg == chan->desc->num_sgs)
		chan->next_sg = 0;

	sg_req = &chan->desc->sg_req[chan->next_sg];
	reg = &sg_req->chan_reg;

	stm32_dma_write(dmadev, STM32_DMA_SCR(chan->id), reg->dma_scr);
	stm32_dma_write(dmadev, STM32_DMA_SPAR(chan->id), reg->dma_spar);
	stm32_dma_write(dmadev, STM32_DMA_SM0AR(chan->id), reg->dma_sm0ar);
	stm32_dma_write(dmadev, STM32_DMA_SFCR(chan->id), reg->dma_sfcr);
	stm32_dma_write(dmadev, STM32_DMA_SM1AR(chan->id), reg->dma_sm1ar);
	stm32_dma_write(dmadev, STM32_DMA_SNDTR(chan->id), reg->dma_sndtr);

	chan->next_sg++;

	/* Clear interrupt status if it is there */
	status = stm32_dma_irq_status(chan);
	if (status)
		stm32_dma_irq_clear(chan, status);

	if (chan->desc->cyclic)
		stm32_dma_configure_next_sg(chan);

	stm32_dma_dump_reg(chan);

	/* Start DMA */
	reg->dma_scr |= STM32_DMA_SCR_EN;
	stm32_dma_write(dmadev, STM32_DMA_SCR(chan->id), reg->dma_scr);

	chan->busy = true;

	dev_dbg(chan2dev(chan), "vchan %pK: started\n", &chan->vchan);
}

static void stm32_dma_configure_next_sg(struct stm32_dma_chan *chan)
{
	struct stm32_dma_device *dmadev = stm32_dma_get_dev(chan);
	struct stm32_dma_sg_req *sg_req;
	u32 dma_scr, dma_sm0ar, dma_sm1ar, id;

	id = chan->id;
	dma_scr = stm32_dma_read(dmadev, STM32_DMA_SCR(id));

	if (dma_scr & STM32_DMA_SCR_DBM) {
		if (chan->next_sg == chan->desc->num_sgs)
			chan->next_sg = 0;

		sg_req = &chan->desc->sg_req[chan->next_sg];

		if (dma_scr & STM32_DMA_SCR_CT) {
			dma_sm0ar = sg_req->chan_reg.dma_sm0ar;
			stm32_dma_write(dmadev, STM32_DMA_SM0AR(id), dma_sm0ar);
			dev_dbg(chan2dev(chan), "CT=1 <=> SM0AR: 0x%08x\n",
				stm32_dma_read(dmadev, STM32_DMA_SM0AR(id)));
		} else {
			dma_sm1ar = sg_req->chan_reg.dma_sm1ar;
			stm32_dma_write(dmadev, STM32_DMA_SM1AR(id), dma_sm1ar);
			dev_dbg(chan2dev(chan), "CT=0 <=> SM1AR: 0x%08x\n",
				stm32_dma_read(dmadev, STM32_DMA_SM1AR(id)));
		}
	}
}

static void stm32_dma_handle_chan_done(struct stm32_dma_chan *chan)
{
	if (chan->desc) {
		if (chan->desc->cyclic) {
			vchan_cyclic_callback(&chan->desc->vdesc);
			chan->next_sg++;
			stm32_dma_configure_next_sg(chan);
		} else {
			chan->busy = false;
			if (chan->next_sg == chan->desc->num_sgs) {
				list_del(&chan->desc->vdesc.node);
				vchan_cookie_complete(&chan->desc->vdesc);
				chan->desc = NULL;
			}
			stm32_dma_start_transfer(chan);
		}
	}
}

static irqreturn_t stm32_dma_chan_irq(int irq, void *devid)
{
	struct stm32_dma_chan *chan = devid;
	struct stm32_dma_device *dmadev = stm32_dma_get_dev(chan);
	u32 status, scr, sfcr;

	spin_lock(&chan->vchan.lock);

	status = stm32_dma_irq_status(chan);
	scr = stm32_dma_read(dmadev, STM32_DMA_SCR(chan->id));
	sfcr = stm32_dma_read(dmadev, STM32_DMA_SFCR(chan->id));

	if (status & STM32_DMA_TCI) {
		stm32_dma_irq_clear(chan, STM32_DMA_TCI);
		if (scr & STM32_DMA_SCR_TCIE)
			stm32_dma_handle_chan_done(chan);
		status &= ~STM32_DMA_TCI;
	}
	if (status & STM32_DMA_HTI) {
		stm32_dma_irq_clear(chan, STM32_DMA_HTI);
		status &= ~STM32_DMA_HTI;
	}
	if (status & STM32_DMA_FEI) {
		stm32_dma_irq_clear(chan, STM32_DMA_FEI);
		status &= ~STM32_DMA_FEI;
		if (sfcr & STM32_DMA_SFCR_FEIE) {
			if (!(scr & STM32_DMA_SCR_EN))
				dev_err(chan2dev(chan), "FIFO Error\n");
			else
				dev_dbg(chan2dev(chan), "FIFO over/underrun\n");
		}
	}
	if (status) {
		stm32_dma_irq_clear(chan, status);
		dev_err(chan2dev(chan), "DMA error: status=0x%08x\n", status);
		if (!(scr & STM32_DMA_SCR_EN))
			dev_err(chan2dev(chan), "chan disabled by HW\n");
	}

	spin_unlock(&chan->vchan.lock);

	return IRQ_HANDLED;
}

static void stm32_dma_issue_pending(struct dma_chan *c)
{
	struct stm32_dma_chan *chan = to_stm32_dma_chan(c);
	unsigned long flags;

	spin_lock_irqsave(&chan->vchan.lock, flags);
	if (vchan_issue_pending(&chan->vchan) && !chan->desc && !chan->busy) {
		dev_dbg(chan2dev(chan), "vchan %pK: issued\n", &chan->vchan);
		stm32_dma_start_transfer(chan);

	}
	spin_unlock_irqrestore(&chan->vchan.lock, flags);
}

static int stm32_dma_set_xfer_param(struct stm32_dma_chan *chan,
				    enum dma_transfer_direction direction,
				    enum dma_slave_buswidth *buswidth,
				    u32 buf_len)
{
	enum dma_slave_buswidth src_addr_width, dst_addr_width;
	int src_bus_width, dst_bus_width;
	int src_burst_size, dst_burst_size;
	u32 src_maxburst, dst_maxburst, src_best_burst, dst_best_burst;
	u32 dma_scr, threshold;

	src_addr_width = chan->dma_sconfig.src_addr_width;
	dst_addr_width = chan->dma_sconfig.dst_addr_width;
	src_maxburst = chan->dma_sconfig.src_maxburst;
	dst_maxburst = chan->dma_sconfig.dst_maxburst;
	threshold = chan->threshold;

	switch (direction) {
	case DMA_MEM_TO_DEV:
		/* Set device data size */
		dst_bus_width = stm32_dma_get_width(chan, dst_addr_width);
		if (dst_bus_width < 0)
			return dst_bus_width;

		/* Set device burst size */
		dst_best_burst = stm32_dma_get_best_burst(buf_len,
							  dst_maxburst,
							  threshold,
							  dst_addr_width);

		dst_burst_size = stm32_dma_get_burst(chan, dst_best_burst);
		if (dst_burst_size < 0)
			return dst_burst_size;

		/* Set memory data size */
		src_addr_width = stm32_dma_get_max_width(buf_len, threshold);
		chan->mem_width = src_addr_width;
		src_bus_width = stm32_dma_get_width(chan, src_addr_width);
		if (src_bus_width < 0)
			return src_bus_width;

		/* Set memory burst size */
		src_maxburst = STM32_DMA_MAX_BURST;
		src_best_burst = stm32_dma_get_best_burst(buf_len,
							  src_maxburst,
							  threshold,
							  src_addr_width);
		src_burst_size = stm32_dma_get_burst(chan, src_best_burst);
		if (src_burst_size < 0)
			return src_burst_size;

		dma_scr = STM32_DMA_SCR_DIR(STM32_DMA_MEM_TO_DEV) |
			STM32_DMA_SCR_PSIZE(dst_bus_width) |
			STM32_DMA_SCR_MSIZE(src_bus_width) |
			STM32_DMA_SCR_PBURST(dst_burst_size) |
			STM32_DMA_SCR_MBURST(src_burst_size);

		/* Set FIFO threshold */
		chan->chan_reg.dma_sfcr &= ~STM32_DMA_SFCR_FTH_MASK;
		chan->chan_reg.dma_sfcr |= STM32_DMA_SFCR_FTH(threshold);

		/* Set peripheral address */
		chan->chan_reg.dma_spar = chan->dma_sconfig.dst_addr;
		*buswidth = dst_addr_width;
		break;

	case DMA_DEV_TO_MEM:
		/* Set device data size */
		src_bus_width = stm32_dma_get_width(chan, src_addr_width);
		if (src_bus_width < 0)
			return src_bus_width;

		/* Set device burst size */
		src_best_burst = stm32_dma_get_best_burst(buf_len,
							  src_maxburst,
							  threshold,
							  src_addr_width);
		chan->mem_burst = src_best_burst;
		src_burst_size = stm32_dma_get_burst(chan, src_best_burst);
		if (src_burst_size < 0)
			return src_burst_size;

		/* Set memory data size */
		dst_addr_width = stm32_dma_get_max_width(buf_len, threshold);
		chan->mem_width = dst_addr_width;
		dst_bus_width = stm32_dma_get_width(chan, dst_addr_width);
		if (dst_bus_width < 0)
			return dst_bus_width;

		/* Set memory burst size */
		dst_maxburst = STM32_DMA_MAX_BURST;
		dst_best_burst = stm32_dma_get_best_burst(buf_len,
							  dst_maxburst,
							  threshold,
							  dst_addr_width);
		chan->mem_burst = dst_best_burst;
		dst_burst_size = stm32_dma_get_burst(chan, dst_best_burst);
		if (dst_burst_size < 0)
			return dst_burst_size;

		dma_scr = STM32_DMA_SCR_DIR(STM32_DMA_DEV_TO_MEM) |
			STM32_DMA_SCR_PSIZE(src_bus_width) |
			STM32_DMA_SCR_MSIZE(dst_bus_width) |
			STM32_DMA_SCR_PBURST(src_burst_size) |
			STM32_DMA_SCR_MBURST(dst_burst_size);

		/* Set FIFO threshold */
		chan->chan_reg.dma_sfcr &= ~STM32_DMA_SFCR_FTH_MASK;
		chan->chan_reg.dma_sfcr |= STM32_DMA_SFCR_FTH(threshold);

		/* Set peripheral address */
		chan->chan_reg.dma_spar = chan->dma_sconfig.src_addr;
		*buswidth = chan->dma_sconfig.src_addr_width;
		break;

	default:
		dev_err(chan2dev(chan), "Dma direction is not supported\n");
		return -EINVAL;
	}

	stm32_dma_set_fifo_config(chan, src_best_burst, dst_best_burst);

	/* Set DMA control register */
	chan->chan_reg.dma_scr &= ~(STM32_DMA_SCR_DIR_MASK |
			STM32_DMA_SCR_PSIZE_MASK | STM32_DMA_SCR_MSIZE_MASK |
			STM32_DMA_SCR_PBURST_MASK | STM32_DMA_SCR_MBURST_MASK);
	chan->chan_reg.dma_scr |= dma_scr;

	return 0;
}

static void stm32_dma_clear_reg(struct stm32_dma_chan_reg *regs)
{
	memset(regs, 0, sizeof(struct stm32_dma_chan_reg));
}

static struct dma_async_tx_descriptor *stm32_dma_prep_slave_sg(
	struct dma_chan *c, struct scatterlist *sgl,
	u32 sg_len, enum dma_transfer_direction direction,
	unsigned long flags, void *context)
{
	struct stm32_dma_chan *chan = to_stm32_dma_chan(c);
	struct stm32_dma_desc *desc;
	struct scatterlist *sg;
	enum dma_slave_buswidth buswidth;
	u32 nb_data_items;
	int i, ret;

	if (!chan->config_init) {
		dev_err(chan2dev(chan), "dma channel is not configured\n");
		return NULL;
	}

	if (sg_len < 1) {
		dev_err(chan2dev(chan), "Invalid segment length %d\n", sg_len);
		return NULL;
	}

	desc = stm32_dma_alloc_desc(sg_len);
	if (!desc)
		return NULL;

	/* Set peripheral flow controller */
	if (chan->dma_sconfig.device_fc)
		chan->chan_reg.dma_scr |= STM32_DMA_SCR_PFCTRL;
	else
		chan->chan_reg.dma_scr &= ~STM32_DMA_SCR_PFCTRL;

	for_each_sg(sgl, sg, sg_len, i) {
		ret = stm32_dma_set_xfer_param(chan, direction, &buswidth,
					       sg_dma_len(sg));
		if (ret < 0)
			goto err;

		desc->sg_req[i].len = sg_dma_len(sg);

		nb_data_items = desc->sg_req[i].len / buswidth;
		if (nb_data_items > STM32_DMA_ALIGNED_MAX_DATA_ITEMS) {
			dev_err(chan2dev(chan), "nb items not supported\n");
			goto err;
		}

		stm32_dma_clear_reg(&desc->sg_req[i].chan_reg);
		desc->sg_req[i].chan_reg.dma_scr = chan->chan_reg.dma_scr;
		desc->sg_req[i].chan_reg.dma_sfcr = chan->chan_reg.dma_sfcr;
		desc->sg_req[i].chan_reg.dma_spar = chan->chan_reg.dma_spar;
		desc->sg_req[i].chan_reg.dma_sm0ar = sg_dma_address(sg);
		desc->sg_req[i].chan_reg.dma_sm1ar = sg_dma_address(sg);
		desc->sg_req[i].chan_reg.dma_sndtr = nb_data_items;
	}

	desc->num_sgs = sg_len;
	desc->cyclic = false;

	return vchan_tx_prep(&chan->vchan, &desc->vdesc, flags);

err:
	kfree(desc);
	return NULL;
}

static struct dma_async_tx_descriptor *stm32_dma_prep_dma_cyclic(
	struct dma_chan *c, dma_addr_t buf_addr, size_t buf_len,
	size_t period_len, enum dma_transfer_direction direction,
	unsigned long flags)
{
	struct stm32_dma_chan *chan = to_stm32_dma_chan(c);
	struct stm32_dma_desc *desc;
	enum dma_slave_buswidth buswidth;
	u32 num_periods, nb_data_items;
	int i, ret;

	if (!buf_len || !period_len) {
		dev_err(chan2dev(chan), "Invalid buffer/period len\n");
		return NULL;
	}

	if (!chan->config_init) {
		dev_err(chan2dev(chan), "dma channel is not configured\n");
		return NULL;
	}

	if (buf_len % period_len) {
		dev_err(chan2dev(chan), "buf_len not multiple of period_len\n");
		return NULL;
	}

	/*
	 * We allow to take more number of requests till DMA is
	 * not started. The driver will loop over all requests.
	 * Once DMA is started then new requests can be queued only after
	 * terminating the DMA.
	 */
	if (chan->busy) {
		dev_err(chan2dev(chan), "Request not allowed when dma busy\n");
		return NULL;
	}

	ret = stm32_dma_set_xfer_param(chan, direction, &buswidth, period_len);
	if (ret < 0)
		return NULL;

	nb_data_items = period_len / buswidth;
	if (nb_data_items > STM32_DMA_ALIGNED_MAX_DATA_ITEMS) {
		dev_err(chan2dev(chan), "number of items not supported\n");
		return NULL;
	}

	/*  Enable Circular mode or double buffer mode */
	if (buf_len == period_len)
		chan->chan_reg.dma_scr |= STM32_DMA_SCR_CIRC;
	else
		chan->chan_reg.dma_scr |= STM32_DMA_SCR_DBM;

	/* Clear periph ctrl if client set it */
	chan->chan_reg.dma_scr &= ~STM32_DMA_SCR_PFCTRL;

	num_periods = buf_len / period_len;

	desc = stm32_dma_alloc_desc(num_periods);
	if (!desc)
		return NULL;

	for (i = 0; i < num_periods; i++) {
		desc->sg_req[i].len = period_len;

		stm32_dma_clear_reg(&desc->sg_req[i].chan_reg);
		desc->sg_req[i].chan_reg.dma_scr = chan->chan_reg.dma_scr;
		desc->sg_req[i].chan_reg.dma_sfcr = chan->chan_reg.dma_sfcr;
		desc->sg_req[i].chan_reg.dma_spar = chan->chan_reg.dma_spar;
		desc->sg_req[i].chan_reg.dma_sm0ar = buf_addr;
		desc->sg_req[i].chan_reg.dma_sm1ar = buf_addr;
		desc->sg_req[i].chan_reg.dma_sndtr = nb_data_items;
		buf_addr += period_len;
	}

	desc->num_sgs = num_periods;
	desc->cyclic = true;

	return vchan_tx_prep(&chan->vchan, &desc->vdesc, flags);
}

static struct dma_async_tx_descriptor *stm32_dma_prep_dma_memcpy(
	struct dma_chan *c, dma_addr_t dest,
	dma_addr_t src, size_t len, unsigned long flags)
{
	struct stm32_dma_chan *chan = to_stm32_dma_chan(c);
	enum dma_slave_buswidth max_width;
	struct stm32_dma_desc *desc;
	size_t xfer_count, offset;
	u32 num_sgs, best_burst, dma_burst, threshold;
	int i;

	num_sgs = DIV_ROUND_UP(len, STM32_DMA_ALIGNED_MAX_DATA_ITEMS);
	desc = stm32_dma_alloc_desc(num_sgs);
	if (!desc)
		return NULL;

	threshold = chan->threshold;

	for (offset = 0, i = 0; offset < len; offset += xfer_count, i++) {
		xfer_count = min_t(size_t, len - offset,
				   STM32_DMA_ALIGNED_MAX_DATA_ITEMS);

		/* Compute best burst size */
		max_width = DMA_SLAVE_BUSWIDTH_1_BYTE;
		best_burst = stm32_dma_get_best_burst(len, STM32_DMA_MAX_BURST,
						      threshold, max_width);
		dma_burst = stm32_dma_get_burst(chan, best_burst);

		stm32_dma_clear_reg(&desc->sg_req[i].chan_reg);
		desc->sg_req[i].chan_reg.dma_scr =
			STM32_DMA_SCR_DIR(STM32_DMA_MEM_TO_MEM) |
			STM32_DMA_SCR_PBURST(dma_burst) |
			STM32_DMA_SCR_MBURST(dma_burst) |
			STM32_DMA_SCR_MINC |
			STM32_DMA_SCR_PINC |
			STM32_DMA_SCR_TCIE |
			STM32_DMA_SCR_TEIE;
		desc->sg_req[i].chan_reg.dma_sfcr |= STM32_DMA_SFCR_MASK;
		desc->sg_req[i].chan_reg.dma_sfcr |=
			STM32_DMA_SFCR_FTH(threshold);
		desc->sg_req[i].chan_reg.dma_spar = src + offset;
		desc->sg_req[i].chan_reg.dma_sm0ar = dest + offset;
		desc->sg_req[i].chan_reg.dma_sndtr = xfer_count;
		desc->sg_req[i].len = xfer_count;
	}

	desc->num_sgs = num_sgs;
	desc->cyclic = false;

	return vchan_tx_prep(&chan->vchan, &desc->vdesc, flags);
}

static u32 stm32_dma_get_remaining_bytes(struct stm32_dma_chan *chan)
{
	u32 dma_scr, width, ndtr;
	struct stm32_dma_device *dmadev = stm32_dma_get_dev(chan);

	dma_scr = stm32_dma_read(dmadev, STM32_DMA_SCR(chan->id));
	width = STM32_DMA_SCR_PSIZE_GET(dma_scr);
	ndtr = stm32_dma_read(dmadev, STM32_DMA_SNDTR(chan->id));

	return ndtr << width;
}

/**
 * stm32_dma_is_current_sg - check that expected sg_req is currently transferred
 * @chan: dma channel
 *
 * This function called when IRQ are disable, checks that the hardware has not
 * switched on the next transfer in double buffer mode. The test is done by
 * comparing the next_sg memory address with the hardware related register
 * (based on CT bit value).
 *
 * Returns true if expected current transfer is still running or double
 * buffer mode is not activated.
 */
static bool stm32_dma_is_current_sg(struct stm32_dma_chan *chan)
{
	struct stm32_dma_device *dmadev = stm32_dma_get_dev(chan);
	struct stm32_dma_sg_req *sg_req;
	u32 dma_scr, dma_smar, id;

	id = chan->id;
	dma_scr = stm32_dma_read(dmadev, STM32_DMA_SCR(id));

	if (!(dma_scr & STM32_DMA_SCR_DBM))
		return true;

	sg_req = &chan->desc->sg_req[chan->next_sg];

	if (dma_scr & STM32_DMA_SCR_CT) {
		dma_smar = stm32_dma_read(dmadev, STM32_DMA_SM0AR(id));
		return (dma_smar == sg_req->chan_reg.dma_sm0ar);
	}

	dma_smar = stm32_dma_read(dmadev, STM32_DMA_SM1AR(id));

	return (dma_smar == sg_req->chan_reg.dma_sm1ar);
}

static size_t stm32_dma_desc_residue(struct stm32_dma_chan *chan,
				     struct stm32_dma_desc *desc,
				     u32 next_sg)
{
	u32 modulo, burst_size;
	u32 residue;
	u32 n_sg = next_sg;
	struct stm32_dma_sg_req *sg_req = &chan->desc->sg_req[chan->next_sg];
	int i;

	/*
	 * Calculate the residue means compute the descriptors
	 * information:
	 * - the sg_req currently transferred
	 * - the Hardware remaining position in this sg (NDTR bits field).
	 *
	 * A race condition may occur if DMA is running in cyclic or double
	 * buffer mode, since the DMA register are automatically reloaded at end
	 * of period transfer. The hardware may have switched to the next
	 * transfer (CT bit updated) just before the position (SxNDTR reg) is
	 * read.
	 * In this case the SxNDTR reg could (or not) correspond to the new
	 * transfer position, and not the expected one.
	 * The strategy implemented in the stm32 driver is to:
	 *  - read the SxNDTR register
	 *  - crosscheck that hardware is still in current transfer.
	 * In case of switch, we can assume that the DMA is at the beginning of
	 * the next transfer. So we approximate the residue in consequence, by
	 * pointing on the beginning of next transfer.
	 *
	 * This race condition doesn't apply for none cyclic mode, as double
	 * buffer is not used. In such situation registers are updated by the
	 * software.
	 */

	residue = stm32_dma_get_remaining_bytes(chan);

	if (!stm32_dma_is_current_sg(chan)) {
		n_sg++;
		if (n_sg == chan->desc->num_sgs)
			n_sg = 0;
		residue = sg_req->len;
	}

	/*
	 * In cyclic mode, for the last period, residue = remaining bytes
	 * from NDTR,
	 * else for all other periods in cyclic mode, and in sg mode,
	 * residue = remaining bytes from NDTR + remaining
	 * periods/sg to be transferred
	 */
	if (!chan->desc->cyclic || n_sg != 0)
		for (i = n_sg; i < desc->num_sgs; i++)
			residue += desc->sg_req[i].len;

	if (!chan->mem_burst)
		return residue;

	burst_size = chan->mem_burst * chan->mem_width;
	modulo = residue % burst_size;
	if (modulo)
		residue = residue - modulo + burst_size;

	return residue;
}

static enum dma_status stm32_dma_tx_status(struct dma_chan *c,
					   dma_cookie_t cookie,
					   struct dma_tx_state *state)
{
	struct stm32_dma_chan *chan = to_stm32_dma_chan(c);
	struct virt_dma_desc *vdesc;
	enum dma_status status;
	unsigned long flags;
	u32 residue = 0;

	status = dma_cookie_status(c, cookie, state);
	if (status == DMA_COMPLETE || !state)
		return status;

	spin_lock_irqsave(&chan->vchan.lock, flags);
	vdesc = vchan_find_desc(&chan->vchan, cookie);
	if (chan->desc && cookie == chan->desc->vdesc.tx.cookie)
		residue = stm32_dma_desc_residue(chan, chan->desc,
						 chan->next_sg);
	else if (vdesc)
		residue = stm32_dma_desc_residue(chan,
						 to_stm32_dma_desc(vdesc), 0);
	dma_set_residue(state, residue);

	spin_unlock_irqrestore(&chan->vchan.lock, flags);

	return status;
}

static int stm32_dma_alloc_chan_resources(struct dma_chan *c)
{
	struct stm32_dma_chan *chan = to_stm32_dma_chan(c);
	struct stm32_dma_device *dmadev = stm32_dma_get_dev(chan);
	int ret;

	chan->config_init = false;

	ret = pm_runtime_get_sync(dmadev->ddev.dev);
	if (ret < 0)
		return ret;

	ret = stm32_dma_disable_chan(chan);
	if (ret < 0)
		pm_runtime_put(dmadev->ddev.dev);

	return ret;
}

static void stm32_dma_free_chan_resources(struct dma_chan *c)
{
	struct stm32_dma_chan *chan = to_stm32_dma_chan(c);
	struct stm32_dma_device *dmadev = stm32_dma_get_dev(chan);
	unsigned long flags;

	dev_dbg(chan2dev(chan), "Freeing channel %d\n", chan->id);

	if (chan->busy) {
		spin_lock_irqsave(&chan->vchan.lock, flags);
		stm32_dma_stop(chan);
		chan->desc = NULL;
		spin_unlock_irqrestore(&chan->vchan.lock, flags);
	}

	pm_runtime_put(dmadev->ddev.dev);

	vchan_free_chan_resources(to_virt_chan(c));
}

static void stm32_dma_desc_free(struct virt_dma_desc *vdesc)
{
	kfree(container_of(vdesc, struct stm32_dma_desc, vdesc));
}

static void stm32_dma_set_config(struct stm32_dma_chan *chan,
				 struct stm32_dma_cfg *cfg)
{
	stm32_dma_clear_reg(&chan->chan_reg);

	chan->chan_reg.dma_scr = cfg->stream_config & STM32_DMA_SCR_CFG_MASK;
	chan->chan_reg.dma_scr |= STM32_DMA_SCR_REQ(cfg->request_line);

	/* Enable Interrupts  */
	chan->chan_reg.dma_scr |= STM32_DMA_SCR_TEIE | STM32_DMA_SCR_TCIE;

	chan->threshold = STM32_DMA_THRESHOLD_FTR_GET(cfg->features);
}

static struct dma_chan *stm32_dma_of_xlate(struct of_phandle_args *dma_spec,
					   struct of_dma *ofdma)
{
	struct stm32_dma_device *dmadev = ofdma->of_dma_data;
	struct device *dev = dmadev->ddev.dev;
	struct stm32_dma_cfg cfg;
	struct stm32_dma_chan *chan;
	struct dma_chan *c;

	if (dma_spec->args_count < 4) {
		dev_err(dev, "Bad number of cells\n");
		return NULL;
	}

	cfg.channel_id = dma_spec->args[0];
	cfg.request_line = dma_spec->args[1];
	cfg.stream_config = dma_spec->args[2];
	cfg.features = dma_spec->args[3];

	if (cfg.channel_id >= STM32_DMA_MAX_CHANNELS ||
	    cfg.request_line >= STM32_DMA_MAX_REQUEST_ID) {
		dev_err(dev, "Bad channel and/or request id\n");
		return NULL;
	}

	chan = &dmadev->chan[cfg.channel_id];

	c = dma_get_slave_channel(&chan->vchan.chan);
	if (!c) {
		dev_err(dev, "No more channels available\n");
		return NULL;
	}

	stm32_dma_set_config(chan, &cfg);

	return c;
}

static const struct of_device_id stm32_dma_of_match[] = {
	{ .compatible = "st,stm32-dma", },
	{ /* sentinel */ },
};
MODULE_DEVICE_TABLE(of, stm32_dma_of_match);

static int stm32_dma_probe(struct platform_device *pdev)
{
	struct stm32_dma_chan *chan;
	struct stm32_dma_device *dmadev;
	struct dma_device *dd;
	const struct of_device_id *match;
	struct resource *res;
	int i, ret;

	match = of_match_device(stm32_dma_of_match, &pdev->dev);
	if (!match) {
		dev_err(&pdev->dev, "Error: No device match found\n");
		return -ENODEV;
	}

	dmadev = devm_kzalloc(&pdev->dev, sizeof(*dmadev), GFP_KERNEL);
	if (!dmadev)
		return -ENOMEM;

	dd = &dmadev->ddev;

	res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
	dmadev->base = devm_ioremap_resource(&pdev->dev, res);
	if (IS_ERR(dmadev->base))
		return PTR_ERR(dmadev->base);

	dmadev->clk = devm_clk_get(&pdev->dev, NULL);
	if (IS_ERR(dmadev->clk)) {
		dev_err(&pdev->dev, "Error: Missing controller clock\n");
		return PTR_ERR(dmadev->clk);
	}

	ret = clk_prepare_enable(dmadev->clk);
	if (ret < 0) {
		dev_err(&pdev->dev, "clk_prep_enable error: %d\n", ret);
		return ret;
	}

	dmadev->mem2mem = of_property_read_bool(pdev->dev.of_node,
						"st,mem2mem");

	dmadev->rst = devm_reset_control_get(&pdev->dev, NULL);
	if (!IS_ERR(dmadev->rst)) {
		reset_control_assert(dmadev->rst);
		udelay(2);
		reset_control_deassert(dmadev->rst);
	}

	dma_cap_set(DMA_SLAVE, dd->cap_mask);
	dma_cap_set(DMA_PRIVATE, dd->cap_mask);
	dma_cap_set(DMA_CYCLIC, dd->cap_mask);
	dd->device_alloc_chan_resources = stm32_dma_alloc_chan_resources;
	dd->device_free_chan_resources = stm32_dma_free_chan_resources;
	dd->device_tx_status = stm32_dma_tx_status;
	dd->device_issue_pending = stm32_dma_issue_pending;
	dd->device_prep_slave_sg = stm32_dma_prep_slave_sg;
	dd->device_prep_dma_cyclic = stm32_dma_prep_dma_cyclic;
	dd->device_config = stm32_dma_slave_config;
	dd->device_terminate_all = stm32_dma_terminate_all;
	dd->device_synchronize = stm32_dma_synchronize;
	dd->src_addr_widths = BIT(DMA_SLAVE_BUSWIDTH_1_BYTE) |
		BIT(DMA_SLAVE_BUSWIDTH_2_BYTES) |
		BIT(DMA_SLAVE_BUSWIDTH_4_BYTES);
	dd->dst_addr_widths = BIT(DMA_SLAVE_BUSWIDTH_1_BYTE) |
		BIT(DMA_SLAVE_BUSWIDTH_2_BYTES) |
		BIT(DMA_SLAVE_BUSWIDTH_4_BYTES);
	dd->directions = BIT(DMA_DEV_TO_MEM) | BIT(DMA_MEM_TO_DEV);
	dd->residue_granularity = DMA_RESIDUE_GRANULARITY_BURST;
	dd->max_burst = STM32_DMA_MAX_BURST;
	dd->dev = &pdev->dev;
	INIT_LIST_HEAD(&dd->channels);

	if (dmadev->mem2mem) {
		dma_cap_set(DMA_MEMCPY, dd->cap_mask);
		dd->device_prep_dma_memcpy = stm32_dma_prep_dma_memcpy;
		dd->directions |= BIT(DMA_MEM_TO_MEM);
	}

	for (i = 0; i < STM32_DMA_MAX_CHANNELS; i++) {
		chan = &dmadev->chan[i];
		chan->id = i;
		chan->vchan.desc_free = stm32_dma_desc_free;
		vchan_init(&chan->vchan, dd);
	}

	ret = dma_async_device_register(dd);
	if (ret)
		goto clk_free;

	for (i = 0; i < STM32_DMA_MAX_CHANNELS; i++) {
		chan = &dmadev->chan[i];
		ret = platform_get_irq(pdev, i);
		if (ret < 0)
			goto err_unregister;
		chan->irq = ret;

		ret = devm_request_irq(&pdev->dev, chan->irq,
				       stm32_dma_chan_irq, 0,
				       dev_name(chan2dev(chan)), chan);
		if (ret) {
			dev_err(&pdev->dev,
				"request_irq failed with err %d channel %d\n",
				ret, i);
			goto err_unregister;
		}
	}

	ret = of_dma_controller_register(pdev->dev.of_node,
					 stm32_dma_of_xlate, dmadev);
	if (ret < 0) {
		dev_err(&pdev->dev,
			"STM32 DMA DMA OF registration failed %d\n", ret);
		goto err_unregister;
	}

	platform_set_drvdata(pdev, dmadev);

	pm_runtime_set_active(&pdev->dev);
	pm_runtime_enable(&pdev->dev);
	pm_runtime_get_noresume(&pdev->dev);
	pm_runtime_put(&pdev->dev);

	dev_info(&pdev->dev, "STM32 DMA driver registered\n");

	return 0;

err_unregister:
	dma_async_device_unregister(dd);
clk_free:
	clk_disable_unprepare(dmadev->clk);

	return ret;
}

#ifdef CONFIG_PM
static int stm32_dma_runtime_suspend(struct device *dev)
{
	struct stm32_dma_device *dmadev = dev_get_drvdata(dev);

	clk_disable_unprepare(dmadev->clk);

	return 0;
}

static int stm32_dma_runtime_resume(struct device *dev)
{
	struct stm32_dma_device *dmadev = dev_get_drvdata(dev);
	int ret;

	ret = clk_prepare_enable(dmadev->clk);
	if (ret) {
		dev_err(dev, "failed to prepare_enable clock\n");
		return ret;
	}

	return 0;
}
#endif

static const struct dev_pm_ops stm32_dma_pm_ops = {
	SET_RUNTIME_PM_OPS(stm32_dma_runtime_suspend,
			   stm32_dma_runtime_resume, NULL)
};

static struct platform_driver stm32_dma_driver = {
	.driver = {
		.name = "stm32-dma",
		.of_match_table = stm32_dma_of_match,
		.pm = &stm32_dma_pm_ops,
	},
};

static int __init stm32_dma_init(void)
{
	return platform_driver_probe(&stm32_dma_driver, stm32_dma_probe);
}
subsys_initcall(stm32_dma_init);