summaryrefslogtreecommitdiff
path: root/drivers/i2c/busses/i2c-img-scb.c
blob: ea20425b6972179c037abb239ecde0b4b4f1994f (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
1454
1455
1456
1457
1458
1459
1460
1461
1462
1463
1464
1465
1466
1467
/*
 * I2C adapter for the IMG Serial Control Bus (SCB) IP block.
 *
 * Copyright (C) 2009, 2010, 2012, 2014 Imagination Technologies Ltd.
 *
 * 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.
 *
 * There are three ways that this I2C controller can be driven:
 *
 * - Raw control of the SDA and SCK signals.
 *
 *   This corresponds to MODE_RAW, which takes control of the signals
 *   directly for a certain number of clock cycles (the INT_TIMING
 *   interrupt can be used for timing).
 *
 * - Atomic commands. A low level I2C symbol (such as generate
 *   start/stop/ack/nack bit, generate byte, receive byte, and receive
 *   ACK) is given to the hardware, with detection of completion by bits
 *   in the LINESTAT register.
 *
 *   This mode of operation is used by MODE_ATOMIC, which uses an I2C
 *   state machine in the interrupt handler to compose/react to I2C
 *   transactions using atomic mode commands, and also by MODE_SEQUENCE,
 *   which emits a simple fixed sequence of atomic mode commands.
 *
 *   Due to software control, the use of atomic commands usually results
 *   in suboptimal use of the bus, with gaps between the I2C symbols while
 *   the driver decides what to do next.
 *
 * - Automatic mode. A bus address, and whether to read/write is
 *   specified, and the hardware takes care of the I2C state machine,
 *   using a FIFO to send/receive bytes of data to an I2C slave. The
 *   driver just has to keep the FIFO drained or filled in response to the
 *   appropriate FIFO interrupts.
 *
 *   This corresponds to MODE_AUTOMATIC, which manages the FIFOs and deals
 *   with control of repeated start bits between I2C messages.
 *
 *   Use of automatic mode and the FIFO can make much more efficient use
 *   of the bus compared to individual atomic commands, with potentially
 *   no wasted time between I2C symbols or I2C messages.
 *
 * In most cases MODE_AUTOMATIC is used, however if any of the messages in
 * a transaction are zero byte writes (e.g. used by i2cdetect for probing
 * the bus), MODE_ATOMIC must be used since automatic mode is normally
 * started by the writing of data into the FIFO.
 *
 * The other modes are used in specific circumstances where MODE_ATOMIC and
 * MODE_AUTOMATIC aren't appropriate. MODE_RAW is used to implement a bus
 * recovery routine. MODE_SEQUENCE is used to reset the bus and make sure
 * it is in a sane state.
 *
 * Notice that the driver implements a timer-based timeout mechanism.
 * The reason for this mechanism is to reduce the number of interrupts
 * received in automatic mode.
 *
 * The driver would get a slave event and transaction done interrupts for
 * each atomic mode command that gets completed. However, these events are
 * not needed in automatic mode, becase those atomic mode commands are
 * managed automatically by the hardware.
 *
 * In practice, normal I2C transactions will be complete well before you
 * get the timer interrupt, as the timer is re-scheduled during FIFO
 * maintenance and disabled after the transaction is complete.
 *
 * In this way normal automatic mode operation isn't impacted by
 * unnecessary interrupts, but the exceptional abort condition can still be
 * detected (with a slight delay).
 */

#include <linux/bitops.h>
#include <linux/clk.h>
#include <linux/completion.h>
#include <linux/err.h>
#include <linux/i2c.h>
#include <linux/init.h>
#include <linux/interrupt.h>
#include <linux/io.h>
#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/of_platform.h>
#include <linux/platform_device.h>
#include <linux/slab.h>
#include <linux/timer.h>

/* Register offsets */

#define SCB_STATUS_REG			0x00
#define SCB_OVERRIDE_REG		0x04
#define SCB_READ_ADDR_REG		0x08
#define SCB_READ_COUNT_REG		0x0c
#define SCB_WRITE_ADDR_REG		0x10
#define SCB_READ_DATA_REG		0x14
#define SCB_WRITE_DATA_REG		0x18
#define SCB_FIFO_STATUS_REG		0x1c
#define SCB_CONTROL_SOFT_RESET		0x1f
#define SCB_CLK_SET_REG			0x3c
#define SCB_INT_STATUS_REG		0x40
#define SCB_INT_CLEAR_REG		0x44
#define SCB_INT_MASK_REG		0x48
#define SCB_CONTROL_REG			0x4c
#define SCB_TIME_TPL_REG		0x50
#define SCB_TIME_TPH_REG		0x54
#define SCB_TIME_TP2S_REG		0x58
#define SCB_TIME_TBI_REG		0x60
#define SCB_TIME_TSL_REG		0x64
#define SCB_TIME_TDL_REG		0x68
#define SCB_TIME_TSDL_REG		0x6c
#define SCB_TIME_TSDH_REG		0x70
#define SCB_READ_XADDR_REG		0x74
#define SCB_WRITE_XADDR_REG		0x78
#define SCB_WRITE_COUNT_REG		0x7c
#define SCB_CORE_REV_REG		0x80
#define SCB_TIME_TCKH_REG		0x84
#define SCB_TIME_TCKL_REG		0x88
#define SCB_FIFO_FLUSH_REG		0x8c
#define SCB_READ_FIFO_REG		0x94
#define SCB_CLEAR_REG			0x98

/* SCB_CONTROL_REG bits */

#define SCB_CONTROL_CLK_ENABLE		0x1e0
#define SCB_CONTROL_TRANSACTION_HALT	0x200

#define FIFO_READ_FULL			BIT(0)
#define FIFO_READ_EMPTY			BIT(1)
#define FIFO_WRITE_FULL			BIT(2)
#define FIFO_WRITE_EMPTY		BIT(3)

/* SCB_CLK_SET_REG bits */
#define SCB_FILT_DISABLE		BIT(31)
#define SCB_FILT_BYPASS			BIT(30)
#define SCB_FILT_INC_MASK		0x7f
#define SCB_FILT_INC_SHIFT		16
#define SCB_INC_MASK			0x7f
#define SCB_INC_SHIFT			8

/* SCB_INT_*_REG bits */

#define INT_BUS_INACTIVE		BIT(0)
#define INT_UNEXPECTED_START		BIT(1)
#define INT_SCLK_LOW_TIMEOUT		BIT(2)
#define INT_SDAT_LOW_TIMEOUT		BIT(3)
#define INT_WRITE_ACK_ERR		BIT(4)
#define INT_ADDR_ACK_ERR		BIT(5)
#define INT_FIFO_FULL			BIT(9)
#define INT_FIFO_FILLING		BIT(10)
#define INT_FIFO_EMPTY			BIT(11)
#define INT_FIFO_EMPTYING		BIT(12)
#define INT_TRANSACTION_DONE		BIT(15)
#define INT_SLAVE_EVENT			BIT(16)
#define INT_MASTER_HALTED		BIT(17)
#define INT_TIMING			BIT(18)
#define INT_STOP_DETECTED		BIT(19)

#define INT_FIFO_FULL_FILLING	(INT_FIFO_FULL  | INT_FIFO_FILLING)

/* Level interrupts need clearing after handling instead of before */
#define INT_LEVEL			0x01e00

/* Don't allow any interrupts while the clock may be off */
#define INT_ENABLE_MASK_INACTIVE	0x00000

/* Interrupt masks for the different driver modes */

#define INT_ENABLE_MASK_RAW		INT_TIMING

#define INT_ENABLE_MASK_ATOMIC		(INT_TRANSACTION_DONE | \
					 INT_SLAVE_EVENT      | \
					 INT_ADDR_ACK_ERR     | \
					 INT_WRITE_ACK_ERR)

#define INT_ENABLE_MASK_AUTOMATIC	(INT_SCLK_LOW_TIMEOUT | \
					 INT_ADDR_ACK_ERR     | \
					 INT_WRITE_ACK_ERR    | \
					 INT_FIFO_FULL        | \
					 INT_FIFO_FILLING     | \
					 INT_FIFO_EMPTY       | \
					 INT_MASTER_HALTED    | \
					 INT_STOP_DETECTED)

#define INT_ENABLE_MASK_WAITSTOP	(INT_SLAVE_EVENT      | \
					 INT_ADDR_ACK_ERR     | \
					 INT_WRITE_ACK_ERR)

/* SCB_STATUS_REG fields */

#define LINESTAT_SCLK_LINE_STATUS	BIT(0)
#define LINESTAT_SCLK_EN		BIT(1)
#define LINESTAT_SDAT_LINE_STATUS	BIT(2)
#define LINESTAT_SDAT_EN		BIT(3)
#define LINESTAT_DET_START_STATUS	BIT(4)
#define LINESTAT_DET_STOP_STATUS	BIT(5)
#define LINESTAT_DET_ACK_STATUS		BIT(6)
#define LINESTAT_DET_NACK_STATUS	BIT(7)
#define LINESTAT_BUS_IDLE		BIT(8)
#define LINESTAT_T_DONE_STATUS		BIT(9)
#define LINESTAT_SCLK_OUT_STATUS	BIT(10)
#define LINESTAT_SDAT_OUT_STATUS	BIT(11)
#define LINESTAT_GEN_LINE_MASK_STATUS	BIT(12)
#define LINESTAT_START_BIT_DET		BIT(13)
#define LINESTAT_STOP_BIT_DET		BIT(14)
#define LINESTAT_ACK_DET		BIT(15)
#define LINESTAT_NACK_DET		BIT(16)
#define LINESTAT_INPUT_HELD_V		BIT(17)
#define LINESTAT_ABORT_DET		BIT(18)
#define LINESTAT_ACK_OR_NACK_DET	(LINESTAT_ACK_DET | LINESTAT_NACK_DET)
#define LINESTAT_INPUT_DATA		0xff000000
#define LINESTAT_INPUT_DATA_SHIFT	24

#define LINESTAT_CLEAR_SHIFT		13
#define LINESTAT_LATCHED		(0x3f << LINESTAT_CLEAR_SHIFT)

/* SCB_OVERRIDE_REG fields */

#define OVERRIDE_SCLK_OVR		BIT(0)
#define OVERRIDE_SCLKEN_OVR		BIT(1)
#define OVERRIDE_SDAT_OVR		BIT(2)
#define OVERRIDE_SDATEN_OVR		BIT(3)
#define OVERRIDE_MASTER			BIT(9)
#define OVERRIDE_LINE_OVR_EN		BIT(10)
#define OVERRIDE_DIRECT			BIT(11)
#define OVERRIDE_CMD_SHIFT		4
#define OVERRIDE_CMD_MASK		0x1f
#define OVERRIDE_DATA_SHIFT		24

#define OVERRIDE_SCLK_DOWN		(OVERRIDE_LINE_OVR_EN | \
					 OVERRIDE_SCLKEN_OVR)
#define OVERRIDE_SCLK_UP		(OVERRIDE_LINE_OVR_EN | \
					 OVERRIDE_SCLKEN_OVR | \
					 OVERRIDE_SCLK_OVR)
#define OVERRIDE_SDAT_DOWN		(OVERRIDE_LINE_OVR_EN | \
					 OVERRIDE_SDATEN_OVR)
#define OVERRIDE_SDAT_UP		(OVERRIDE_LINE_OVR_EN | \
					 OVERRIDE_SDATEN_OVR | \
					 OVERRIDE_SDAT_OVR)

/* OVERRIDE_CMD values */

#define CMD_PAUSE			0x00
#define CMD_GEN_DATA			0x01
#define CMD_GEN_START			0x02
#define CMD_GEN_STOP			0x03
#define CMD_GEN_ACK			0x04
#define CMD_GEN_NACK			0x05
#define CMD_RET_DATA			0x08
#define CMD_RET_ACK			0x09

/* Fixed timing values */

#define TIMEOUT_TBI			0x0
#define TIMEOUT_TSL			0xffff
#define TIMEOUT_TDL			0x0

/* Transaction timeout */

#define IMG_I2C_TIMEOUT			(msecs_to_jiffies(1000))

/*
 * Worst incs are 1 (innacurate) and 16*256 (irregular).
 * So a sensible inc is the logarithmic mean: 64 (2^6), which is
 * in the middle of the valid range (0-127).
 */
#define SCB_OPT_INC		64

/* Setup the clock enable filtering for 25 ns */
#define SCB_FILT_GLITCH		25

/*
 * Bits to return from interrupt handler functions for different modes.
 * This delays completion until we've finished with the registers, so that the
 * function waiting for completion can safely disable the clock to save power.
 */
#define ISR_COMPLETE_M		BIT(31)
#define ISR_FATAL_M		BIT(30)
#define ISR_WAITSTOP		BIT(29)
#define ISR_STATUS_M		0x0000ffff	/* contains +ve errno */
#define ISR_COMPLETE(err)	(ISR_COMPLETE_M | (ISR_STATUS_M & (err)))
#define ISR_FATAL(err)		(ISR_COMPLETE(err) | ISR_FATAL_M)

enum img_i2c_mode {
	MODE_INACTIVE,
	MODE_RAW,
	MODE_ATOMIC,
	MODE_AUTOMATIC,
	MODE_SEQUENCE,
	MODE_FATAL,
	MODE_WAITSTOP,
	MODE_SUSPEND,
};

/* Timing parameters for i2c modes (in ns) */
struct img_i2c_timings {
	const char *name;
	unsigned int max_bitrate;
	unsigned int tckh, tckl, tsdh, tsdl;
	unsigned int tp2s, tpl, tph;
};

/* The timings array must be ordered from slower to faster */
static struct img_i2c_timings timings[] = {
	/* Standard mode */
	{
		.name = "standard",
		.max_bitrate = 100000,
		.tckh = 4000,
		.tckl = 4700,
		.tsdh = 4700,
		.tsdl = 8700,
		.tp2s = 4700,
		.tpl = 4700,
		.tph = 4000,
	},
	/* Fast mode */
	{
		.name = "fast",
		.max_bitrate = 400000,
		.tckh = 600,
		.tckl = 1300,
		.tsdh = 600,
		.tsdl = 1200,
		.tp2s = 1300,
		.tpl = 600,
		.tph = 600,
	},
};

/* Reset dance */
static u8 img_i2c_reset_seq[] = { CMD_GEN_START,
				  CMD_GEN_DATA, 0xff,
				  CMD_RET_ACK,
				  CMD_GEN_START,
				  CMD_GEN_STOP,
				  0 };
/* Just issue a stop (after an abort condition) */
static u8 img_i2c_stop_seq[] = {  CMD_GEN_STOP,
				  0 };

/* We're interested in different interrupts depending on the mode */
static unsigned int img_i2c_int_enable_by_mode[] = {
	[MODE_INACTIVE]  = INT_ENABLE_MASK_INACTIVE,
	[MODE_RAW]       = INT_ENABLE_MASK_RAW,
	[MODE_ATOMIC]    = INT_ENABLE_MASK_ATOMIC,
	[MODE_AUTOMATIC] = INT_ENABLE_MASK_AUTOMATIC,
	[MODE_SEQUENCE]  = INT_ENABLE_MASK_ATOMIC,
	[MODE_FATAL]     = 0,
	[MODE_WAITSTOP]  = INT_ENABLE_MASK_WAITSTOP,
	[MODE_SUSPEND]   = 0,
};

/* Atomic command names */
static const char * const img_i2c_atomic_cmd_names[] = {
	[CMD_PAUSE]	= "PAUSE",
	[CMD_GEN_DATA]	= "GEN_DATA",
	[CMD_GEN_START]	= "GEN_START",
	[CMD_GEN_STOP]	= "GEN_STOP",
	[CMD_GEN_ACK]	= "GEN_ACK",
	[CMD_GEN_NACK]	= "GEN_NACK",
	[CMD_RET_DATA]	= "RET_DATA",
	[CMD_RET_ACK]	= "RET_ACK",
};

struct img_i2c {
	struct i2c_adapter adap;

	void __iomem *base;

	/*
	 * The scb core clock is used to get the input frequency, and to disable
	 * it after every set of transactions to save some power.
	 */
	struct clk *scb_clk, *sys_clk;
	unsigned int bitrate;
	bool need_wr_rd_fence;

	/* state */
	struct completion msg_complete;
	spinlock_t lock;	/* lock before doing anything with the state */
	struct i2c_msg msg;

	/* After the last transaction, wait for a stop bit */
	bool last_msg;
	int msg_status;

	enum img_i2c_mode mode;
	u32 int_enable;		/* depends on mode */
	u32 line_status;	/* line status over command */

	/*
	 * To avoid slave event interrupts in automatic mode, use a timer to
	 * poll the abort condition if we don't get an interrupt for too long.
	 */
	struct timer_list check_timer;
	bool t_halt;

	/* atomic mode state */
	bool at_t_done;
	bool at_slave_event;
	int at_cur_cmd;
	u8 at_cur_data;

	/* Sequence: either reset or stop. See img_i2c_sequence. */
	u8 *seq;

	/* raw mode */
	unsigned int raw_timeout;
};

static void img_i2c_writel(struct img_i2c *i2c, u32 offset, u32 value)
{
	writel(value, i2c->base + offset);
}

static u32 img_i2c_readl(struct img_i2c *i2c, u32 offset)
{
	return readl(i2c->base + offset);
}

/*
 * The code to read from the master read fifo, and write to the master
 * write fifo, checks a bit in an SCB register before every byte to
 * ensure that the fifo is not full (write fifo) or empty (read fifo).
 * Due to clock domain crossing inside the SCB block the updated value
 * of this bit is only visible after 2 cycles.
 *
 * The scb_wr_rd_fence() function does 2 dummy writes (to the read-only
 * revision register), and it's called after reading from or writing to the
 * fifos to ensure that subsequent reads of the fifo status bits do not read
 * stale values.
 */
static void img_i2c_wr_rd_fence(struct img_i2c *i2c)
{
	if (i2c->need_wr_rd_fence) {
		img_i2c_writel(i2c, SCB_CORE_REV_REG, 0);
		img_i2c_writel(i2c, SCB_CORE_REV_REG, 0);
	}
}

static void img_i2c_switch_mode(struct img_i2c *i2c, enum img_i2c_mode mode)
{
	i2c->mode = mode;
	i2c->int_enable = img_i2c_int_enable_by_mode[mode];
	i2c->line_status = 0;
}

static void img_i2c_raw_op(struct img_i2c *i2c)
{
	i2c->raw_timeout = 0;
	img_i2c_writel(i2c, SCB_OVERRIDE_REG,
		OVERRIDE_SCLKEN_OVR |
		OVERRIDE_SDATEN_OVR |
		OVERRIDE_MASTER |
		OVERRIDE_LINE_OVR_EN |
		OVERRIDE_DIRECT |
		((i2c->at_cur_cmd & OVERRIDE_CMD_MASK) << OVERRIDE_CMD_SHIFT) |
		(i2c->at_cur_data << OVERRIDE_DATA_SHIFT));
}

static const char *img_i2c_atomic_op_name(unsigned int cmd)
{
	if (unlikely(cmd >= ARRAY_SIZE(img_i2c_atomic_cmd_names)))
		return "UNKNOWN";
	return img_i2c_atomic_cmd_names[cmd];
}

/* Send a single atomic mode command to the hardware */
static void img_i2c_atomic_op(struct img_i2c *i2c, int cmd, u8 data)
{
	i2c->at_cur_cmd = cmd;
	i2c->at_cur_data = data;

	/* work around lack of data setup time when generating data */
	if (cmd == CMD_GEN_DATA && i2c->mode == MODE_ATOMIC) {
		u32 line_status = img_i2c_readl(i2c, SCB_STATUS_REG);

		if (line_status & LINESTAT_SDAT_LINE_STATUS && !(data & 0x80)) {
			/* hold the data line down for a moment */
			img_i2c_switch_mode(i2c, MODE_RAW);
			img_i2c_raw_op(i2c);
			return;
		}
	}

	dev_dbg(i2c->adap.dev.parent,
		"atomic cmd=%s (%d) data=%#x\n",
		img_i2c_atomic_op_name(cmd), cmd, data);
	i2c->at_t_done = (cmd == CMD_RET_DATA || cmd == CMD_RET_ACK);
	i2c->at_slave_event = false;
	i2c->line_status = 0;

	img_i2c_writel(i2c, SCB_OVERRIDE_REG,
		((cmd & OVERRIDE_CMD_MASK) << OVERRIDE_CMD_SHIFT) |
		OVERRIDE_MASTER |
		OVERRIDE_DIRECT |
		(data << OVERRIDE_DATA_SHIFT));
}

/* Start a transaction in atomic mode */
static void img_i2c_atomic_start(struct img_i2c *i2c)
{
	img_i2c_switch_mode(i2c, MODE_ATOMIC);
	img_i2c_writel(i2c, SCB_INT_MASK_REG, i2c->int_enable);
	img_i2c_atomic_op(i2c, CMD_GEN_START, 0x00);
}

static void img_i2c_soft_reset(struct img_i2c *i2c)
{
	i2c->t_halt = false;
	img_i2c_writel(i2c, SCB_CONTROL_REG, 0);
	img_i2c_writel(i2c, SCB_CONTROL_REG,
		       SCB_CONTROL_CLK_ENABLE | SCB_CONTROL_SOFT_RESET);
}

/*
 * Enable or release transaction halt for control of repeated starts.
 * In version 3.3 of the IP when transaction halt is set, an interrupt
 * will be generated after each byte of a transfer instead of after
 * every transfer but before the stop bit.
 * Due to this behaviour we have to be careful that every time we
 * release the transaction halt we have to re-enable it straight away
 * so that we only process a single byte, not doing so will result in
 * all remaining bytes been processed and a stop bit being issued,
 * which will prevent us having a repeated start.
 */
static void img_i2c_transaction_halt(struct img_i2c *i2c, bool t_halt)
{
	u32 val;

	if (i2c->t_halt == t_halt)
		return;
	i2c->t_halt = t_halt;
	val = img_i2c_readl(i2c, SCB_CONTROL_REG);
	if (t_halt)
		val |= SCB_CONTROL_TRANSACTION_HALT;
	else
		val &= ~SCB_CONTROL_TRANSACTION_HALT;
	img_i2c_writel(i2c, SCB_CONTROL_REG, val);
}

/* Drain data from the FIFO into the buffer (automatic mode) */
static void img_i2c_read_fifo(struct img_i2c *i2c)
{
	while (i2c->msg.len) {
		u32 fifo_status;
		u8 data;

		img_i2c_wr_rd_fence(i2c);
		fifo_status = img_i2c_readl(i2c, SCB_FIFO_STATUS_REG);
		if (fifo_status & FIFO_READ_EMPTY)
			break;

		data = img_i2c_readl(i2c, SCB_READ_DATA_REG);
		*i2c->msg.buf = data;

		img_i2c_writel(i2c, SCB_READ_FIFO_REG, 0xff);
		i2c->msg.len--;
		i2c->msg.buf++;
	}
}

/* Fill the FIFO with data from the buffer (automatic mode) */
static void img_i2c_write_fifo(struct img_i2c *i2c)
{
	while (i2c->msg.len) {
		u32 fifo_status;

		img_i2c_wr_rd_fence(i2c);
		fifo_status = img_i2c_readl(i2c, SCB_FIFO_STATUS_REG);
		if (fifo_status & FIFO_WRITE_FULL)
			break;

		img_i2c_writel(i2c, SCB_WRITE_DATA_REG, *i2c->msg.buf);
		i2c->msg.len--;
		i2c->msg.buf++;
	}

	/* Disable fifo emptying interrupt if nothing more to write */
	if (!i2c->msg.len)
		i2c->int_enable &= ~INT_FIFO_EMPTYING;
}

/* Start a read transaction in automatic mode */
static void img_i2c_read(struct img_i2c *i2c)
{
	img_i2c_switch_mode(i2c, MODE_AUTOMATIC);
	if (!i2c->last_msg)
		i2c->int_enable |= INT_SLAVE_EVENT;

	img_i2c_writel(i2c, SCB_INT_MASK_REG, i2c->int_enable);
	img_i2c_writel(i2c, SCB_READ_ADDR_REG, i2c->msg.addr);
	img_i2c_writel(i2c, SCB_READ_COUNT_REG, i2c->msg.len);

	mod_timer(&i2c->check_timer, jiffies + msecs_to_jiffies(1));
}

/* Start a write transaction in automatic mode */
static void img_i2c_write(struct img_i2c *i2c)
{
	img_i2c_switch_mode(i2c, MODE_AUTOMATIC);
	if (!i2c->last_msg)
		i2c->int_enable |= INT_SLAVE_EVENT;

	img_i2c_writel(i2c, SCB_WRITE_ADDR_REG, i2c->msg.addr);
	img_i2c_writel(i2c, SCB_WRITE_COUNT_REG, i2c->msg.len);

	mod_timer(&i2c->check_timer, jiffies + msecs_to_jiffies(1));
	img_i2c_write_fifo(i2c);

	/* img_i2c_write_fifo() may modify int_enable */
	img_i2c_writel(i2c, SCB_INT_MASK_REG, i2c->int_enable);
}

/*
 * Indicate that the transaction is complete. This is called from the
 * ISR to wake up the waiting thread, after which the ISR must not
 * access any more SCB registers.
 */
static void img_i2c_complete_transaction(struct img_i2c *i2c, int status)
{
	img_i2c_switch_mode(i2c, MODE_INACTIVE);
	if (status) {
		i2c->msg_status = status;
		img_i2c_transaction_halt(i2c, false);
	}
	complete(&i2c->msg_complete);
}

static unsigned int img_i2c_raw_atomic_delay_handler(struct img_i2c *i2c,
					u32 int_status, u32 line_status)
{
	/* Stay in raw mode for this, so we don't just loop infinitely */
	img_i2c_atomic_op(i2c, i2c->at_cur_cmd, i2c->at_cur_data);
	img_i2c_switch_mode(i2c, MODE_ATOMIC);
	return 0;
}

static unsigned int img_i2c_raw(struct img_i2c *i2c, u32 int_status,
				u32 line_status)
{
	if (int_status & INT_TIMING) {
		if (i2c->raw_timeout == 0)
			return img_i2c_raw_atomic_delay_handler(i2c,
				int_status, line_status);
		--i2c->raw_timeout;
	}
	return 0;
}

static unsigned int img_i2c_sequence(struct img_i2c *i2c, u32 int_status)
{
	static const unsigned int continue_bits[] = {
		[CMD_GEN_START] = LINESTAT_START_BIT_DET,
		[CMD_GEN_DATA]  = LINESTAT_INPUT_HELD_V,
		[CMD_RET_ACK]   = LINESTAT_ACK_DET | LINESTAT_NACK_DET,
		[CMD_RET_DATA]  = LINESTAT_INPUT_HELD_V,
		[CMD_GEN_STOP]  = LINESTAT_STOP_BIT_DET,
	};
	int next_cmd = -1;
	u8 next_data = 0x00;

	if (int_status & INT_SLAVE_EVENT)
		i2c->at_slave_event = true;
	if (int_status & INT_TRANSACTION_DONE)
		i2c->at_t_done = true;

	if (!i2c->at_slave_event || !i2c->at_t_done)
		return 0;

	/* wait if no continue bits are set */
	if (i2c->at_cur_cmd >= 0 &&
	    i2c->at_cur_cmd < ARRAY_SIZE(continue_bits)) {
		unsigned int cont_bits = continue_bits[i2c->at_cur_cmd];

		if (cont_bits) {
			cont_bits |= LINESTAT_ABORT_DET;
			if (!(i2c->line_status & cont_bits))
				return 0;
		}
	}

	/* follow the sequence of commands in i2c->seq */
	next_cmd = *i2c->seq;
	/* stop on a nil */
	if (!next_cmd) {
		img_i2c_writel(i2c, SCB_OVERRIDE_REG, 0);
		return ISR_COMPLETE(0);
	}
	/* when generating data, the next byte is the data */
	if (next_cmd == CMD_GEN_DATA) {
		++i2c->seq;
		next_data = *i2c->seq;
	}
	++i2c->seq;
	img_i2c_atomic_op(i2c, next_cmd, next_data);

	return 0;
}

static void img_i2c_reset_start(struct img_i2c *i2c)
{
	/* Initiate the magic dance */
	img_i2c_switch_mode(i2c, MODE_SEQUENCE);
	img_i2c_writel(i2c, SCB_INT_MASK_REG, i2c->int_enable);
	i2c->seq = img_i2c_reset_seq;
	i2c->at_slave_event = true;
	i2c->at_t_done = true;
	i2c->at_cur_cmd = -1;

	/* img_i2c_reset_seq isn't empty so the following won't fail */
	img_i2c_sequence(i2c, 0);
}

static void img_i2c_stop_start(struct img_i2c *i2c)
{
	/* Initiate a stop bit sequence */
	img_i2c_switch_mode(i2c, MODE_SEQUENCE);
	img_i2c_writel(i2c, SCB_INT_MASK_REG, i2c->int_enable);
	i2c->seq = img_i2c_stop_seq;
	i2c->at_slave_event = true;
	i2c->at_t_done = true;
	i2c->at_cur_cmd = -1;

	/* img_i2c_stop_seq isn't empty so the following won't fail */
	img_i2c_sequence(i2c, 0);
}

static unsigned int img_i2c_atomic(struct img_i2c *i2c,
				   u32 int_status,
				   u32 line_status)
{
	int next_cmd = -1;
	u8 next_data = 0x00;

	if (int_status & INT_SLAVE_EVENT)
		i2c->at_slave_event = true;
	if (int_status & INT_TRANSACTION_DONE)
		i2c->at_t_done = true;

	if (!i2c->at_slave_event || !i2c->at_t_done)
		goto next_atomic_cmd;
	if (i2c->line_status & LINESTAT_ABORT_DET) {
		dev_dbg(i2c->adap.dev.parent, "abort condition detected\n");
		next_cmd = CMD_GEN_STOP;
		i2c->msg_status = -EIO;
		goto next_atomic_cmd;
	}

	/* i2c->at_cur_cmd may have completed */
	switch (i2c->at_cur_cmd) {
	case CMD_GEN_START:
		next_cmd = CMD_GEN_DATA;
		next_data = i2c_8bit_addr_from_msg(&i2c->msg);
		break;
	case CMD_GEN_DATA:
		if (i2c->line_status & LINESTAT_INPUT_HELD_V)
			next_cmd = CMD_RET_ACK;
		break;
	case CMD_RET_ACK:
		if (i2c->line_status & LINESTAT_ACK_DET ||
		    (i2c->line_status & LINESTAT_NACK_DET &&
		    i2c->msg.flags & I2C_M_IGNORE_NAK)) {
			if (i2c->msg.len == 0) {
				next_cmd = CMD_GEN_STOP;
			} else if (i2c->msg.flags & I2C_M_RD) {
				next_cmd = CMD_RET_DATA;
			} else {
				next_cmd = CMD_GEN_DATA;
				next_data = *i2c->msg.buf;
				--i2c->msg.len;
				++i2c->msg.buf;
			}
		} else if (i2c->line_status & LINESTAT_NACK_DET) {
			i2c->msg_status = -EIO;
			next_cmd = CMD_GEN_STOP;
		}
		break;
	case CMD_RET_DATA:
		if (i2c->line_status & LINESTAT_INPUT_HELD_V) {
			*i2c->msg.buf = (i2c->line_status &
						LINESTAT_INPUT_DATA)
					>> LINESTAT_INPUT_DATA_SHIFT;
			--i2c->msg.len;
			++i2c->msg.buf;
			if (i2c->msg.len)
				next_cmd = CMD_GEN_ACK;
			else
				next_cmd = CMD_GEN_NACK;
		}
		break;
	case CMD_GEN_ACK:
		if (i2c->line_status & LINESTAT_ACK_DET) {
			next_cmd = CMD_RET_DATA;
		} else {
			i2c->msg_status = -EIO;
			next_cmd = CMD_GEN_STOP;
		}
		break;
	case CMD_GEN_NACK:
		next_cmd = CMD_GEN_STOP;
		break;
	case CMD_GEN_STOP:
		img_i2c_writel(i2c, SCB_OVERRIDE_REG, 0);
		return ISR_COMPLETE(0);
	default:
		dev_err(i2c->adap.dev.parent, "bad atomic command %d\n",
			i2c->at_cur_cmd);
		i2c->msg_status = -EIO;
		next_cmd = CMD_GEN_STOP;
		break;
	}

next_atomic_cmd:
	if (next_cmd != -1) {
		/* don't actually stop unless we're the last transaction */
		if (next_cmd == CMD_GEN_STOP && !i2c->msg_status &&
						!i2c->last_msg)
			return ISR_COMPLETE(0);
		img_i2c_atomic_op(i2c, next_cmd, next_data);
	}
	return 0;
}

/*
 * Timer function to check if something has gone wrong in automatic mode (so we
 * don't have to handle so many interrupts just to catch an exception).
 */
static void img_i2c_check_timer(unsigned long arg)
{
	struct img_i2c *i2c = (struct img_i2c *)arg;
	unsigned long flags;
	unsigned int line_status;

	spin_lock_irqsave(&i2c->lock, flags);
	line_status = img_i2c_readl(i2c, SCB_STATUS_REG);

	/* check for an abort condition */
	if (line_status & LINESTAT_ABORT_DET) {
		dev_dbg(i2c->adap.dev.parent,
			"abort condition detected by check timer\n");
		/* enable slave event interrupt mask to trigger irq */
		img_i2c_writel(i2c, SCB_INT_MASK_REG,
			       i2c->int_enable | INT_SLAVE_EVENT);
	}

	spin_unlock_irqrestore(&i2c->lock, flags);
}

static unsigned int img_i2c_auto(struct img_i2c *i2c,
				 unsigned int int_status,
				 unsigned int line_status)
{
	if (int_status & (INT_WRITE_ACK_ERR | INT_ADDR_ACK_ERR))
		return ISR_COMPLETE(EIO);

	if (line_status & LINESTAT_ABORT_DET) {
		dev_dbg(i2c->adap.dev.parent, "abort condition detected\n");
		/* empty the read fifo */
		if ((i2c->msg.flags & I2C_M_RD) &&
		    (int_status & INT_FIFO_FULL_FILLING))
			img_i2c_read_fifo(i2c);
		/* use atomic mode and try to force a stop bit */
		i2c->msg_status = -EIO;
		img_i2c_stop_start(i2c);
		return 0;
	}

	/* Enable transaction halt on start bit */
	if (!i2c->last_msg && line_status & LINESTAT_START_BIT_DET) {
		img_i2c_transaction_halt(i2c, !i2c->last_msg);
		/* we're no longer interested in the slave event */
		i2c->int_enable &= ~INT_SLAVE_EVENT;
	}

	mod_timer(&i2c->check_timer, jiffies + msecs_to_jiffies(1));

	if (int_status & INT_STOP_DETECTED) {
		/* Drain remaining data in FIFO and complete transaction */
		if (i2c->msg.flags & I2C_M_RD)
			img_i2c_read_fifo(i2c);
		return ISR_COMPLETE(0);
	}

	if (i2c->msg.flags & I2C_M_RD) {
		if (int_status & (INT_FIFO_FULL_FILLING | INT_MASTER_HALTED)) {
			img_i2c_read_fifo(i2c);
			if (i2c->msg.len == 0)
				return ISR_WAITSTOP;
		}
	} else {
		if (int_status & (INT_FIFO_EMPTY | INT_MASTER_HALTED)) {
			if ((int_status & INT_FIFO_EMPTY) &&
			    i2c->msg.len == 0)
				return ISR_WAITSTOP;
			img_i2c_write_fifo(i2c);
		}
	}
	if (int_status & INT_MASTER_HALTED) {
		/*
		 * Release and then enable transaction halt, to
		 * allow only a single byte to proceed.
		 */
		img_i2c_transaction_halt(i2c, false);
		img_i2c_transaction_halt(i2c, !i2c->last_msg);
	}

	return 0;
}

static irqreturn_t img_i2c_isr(int irq, void *dev_id)
{
	struct img_i2c *i2c = (struct img_i2c *)dev_id;
	u32 int_status, line_status;
	/* We handle transaction completion AFTER accessing registers */
	unsigned int hret;

	/* Read interrupt status register. */
	int_status = img_i2c_readl(i2c, SCB_INT_STATUS_REG);
	/* Clear detected interrupts. */
	img_i2c_writel(i2c, SCB_INT_CLEAR_REG, int_status);

	/*
	 * Read line status and clear it until it actually is clear.  We have
	 * to be careful not to lose any line status bits that get latched.
	 */
	line_status = img_i2c_readl(i2c, SCB_STATUS_REG);
	if (line_status & LINESTAT_LATCHED) {
		img_i2c_writel(i2c, SCB_CLEAR_REG,
			      (line_status & LINESTAT_LATCHED)
				>> LINESTAT_CLEAR_SHIFT);
		img_i2c_wr_rd_fence(i2c);
	}

	spin_lock(&i2c->lock);

	/* Keep track of line status bits received */
	i2c->line_status &= ~LINESTAT_INPUT_DATA;
	i2c->line_status |= line_status;

	/*
	 * Certain interrupts indicate that sclk low timeout is not
	 * a problem. If any of these are set, just continue.
	 */
	if ((int_status & INT_SCLK_LOW_TIMEOUT) &&
	    !(int_status & (INT_SLAVE_EVENT |
			    INT_FIFO_EMPTY |
			    INT_FIFO_FULL))) {
		dev_crit(i2c->adap.dev.parent,
			 "fatal: clock low timeout occurred %s addr 0x%02x\n",
			 (i2c->msg.flags & I2C_M_RD) ? "reading" : "writing",
			 i2c->msg.addr);
		hret = ISR_FATAL(EIO);
		goto out;
	}

	if (i2c->mode == MODE_ATOMIC)
		hret = img_i2c_atomic(i2c, int_status, line_status);
	else if (i2c->mode == MODE_AUTOMATIC)
		hret = img_i2c_auto(i2c, int_status, line_status);
	else if (i2c->mode == MODE_SEQUENCE)
		hret = img_i2c_sequence(i2c, int_status);
	else if (i2c->mode == MODE_WAITSTOP && (int_status & INT_SLAVE_EVENT) &&
			 (line_status & LINESTAT_STOP_BIT_DET))
		hret = ISR_COMPLETE(0);
	else if (i2c->mode == MODE_RAW)
		hret = img_i2c_raw(i2c, int_status, line_status);
	else
		hret = 0;

	/* Clear detected level interrupts. */
	img_i2c_writel(i2c, SCB_INT_CLEAR_REG, int_status & INT_LEVEL);

out:
	if (hret & ISR_WAITSTOP) {
		/*
		 * Only wait for stop on last message.
		 * Also we may already have detected the stop bit.
		 */
		if (!i2c->last_msg || i2c->line_status & LINESTAT_STOP_BIT_DET)
			hret = ISR_COMPLETE(0);
		else
			img_i2c_switch_mode(i2c, MODE_WAITSTOP);
	}

	/* now we've finished using regs, handle transaction completion */
	if (hret & ISR_COMPLETE_M) {
		int status = -(hret & ISR_STATUS_M);

		img_i2c_complete_transaction(i2c, status);
		if (hret & ISR_FATAL_M)
			img_i2c_switch_mode(i2c, MODE_FATAL);
	}

	/* Enable interrupts (int_enable may be altered by changing mode) */
	img_i2c_writel(i2c, SCB_INT_MASK_REG, i2c->int_enable);

	spin_unlock(&i2c->lock);

	return IRQ_HANDLED;
}

/* Force a bus reset sequence and wait for it to complete */
static int img_i2c_reset_bus(struct img_i2c *i2c)
{
	unsigned long flags;
	unsigned long time_left;

	spin_lock_irqsave(&i2c->lock, flags);
	reinit_completion(&i2c->msg_complete);
	img_i2c_reset_start(i2c);
	spin_unlock_irqrestore(&i2c->lock, flags);

	time_left = wait_for_completion_timeout(&i2c->msg_complete,
					      IMG_I2C_TIMEOUT);
	if (time_left == 0)
		return -ETIMEDOUT;
	return 0;
}

static int img_i2c_xfer(struct i2c_adapter *adap, struct i2c_msg *msgs,
			int num)
{
	struct img_i2c *i2c = i2c_get_adapdata(adap);
	bool atomic = false;
	int i, ret;
	unsigned long time_left;

	if (i2c->mode == MODE_SUSPEND) {
		WARN(1, "refusing to service transaction in suspended state\n");
		return -EIO;
	}

	if (i2c->mode == MODE_FATAL)
		return -EIO;

	for (i = 0; i < num; i++) {
		/*
		 * 0 byte reads are not possible because the slave could try
		 * and pull the data line low, preventing a stop bit.
		 */
		if (!msgs[i].len && msgs[i].flags & I2C_M_RD)
			return -EIO;
		/*
		 * 0 byte writes are possible and used for probing, but we
		 * cannot do them in automatic mode, so use atomic mode
		 * instead.
		 *
		 * Also, the I2C_M_IGNORE_NAK mode can only be implemented
		 * in atomic mode.
		 */
		if (!msgs[i].len ||
		    (msgs[i].flags & I2C_M_IGNORE_NAK))
			atomic = true;
	}

	ret = clk_prepare_enable(i2c->scb_clk);
	if (ret)
		return ret;

	for (i = 0; i < num; i++) {
		struct i2c_msg *msg = &msgs[i];
		unsigned long flags;

		spin_lock_irqsave(&i2c->lock, flags);

		/*
		 * Make a copy of the message struct. We mustn't modify the
		 * original or we'll confuse drivers and i2c-dev.
		 */
		i2c->msg = *msg;
		i2c->msg_status = 0;

		/*
		 * After the last message we must have waited for a stop bit.
		 * Not waiting can cause problems when the clock is disabled
		 * before the stop bit is sent, and the linux I2C interface
		 * requires separate transfers not to joined with repeated
		 * start.
		 */
		i2c->last_msg = (i == num - 1);
		reinit_completion(&i2c->msg_complete);

		/*
		 * Clear line status and all interrupts before starting a
		 * transfer, as we may have unserviced interrupts from
		 * previous transfers that might be handled in the context
		 * of the new transfer.
		 */
		img_i2c_writel(i2c, SCB_INT_CLEAR_REG, ~0);
		img_i2c_writel(i2c, SCB_CLEAR_REG, ~0);

		if (atomic) {
			img_i2c_atomic_start(i2c);
		} else {
			/*
			 * Enable transaction halt if not the last message in
			 * the queue so that we can control repeated starts.
			 */
			img_i2c_transaction_halt(i2c, !i2c->last_msg);

			if (msg->flags & I2C_M_RD)
				img_i2c_read(i2c);
			else
				img_i2c_write(i2c);

			/*
			 * Release and then enable transaction halt, to
			 * allow only a single byte to proceed.
			 * This doesn't have an effect on the initial transfer
			 * but will allow the following transfers to start
			 * processing if the previous transfer was marked as
			 * complete while the i2c block was halted.
			 */
			img_i2c_transaction_halt(i2c, false);
			img_i2c_transaction_halt(i2c, !i2c->last_msg);
		}
		spin_unlock_irqrestore(&i2c->lock, flags);

		time_left = wait_for_completion_timeout(&i2c->msg_complete,
						      IMG_I2C_TIMEOUT);
		del_timer_sync(&i2c->check_timer);

		if (time_left == 0) {
			dev_err(adap->dev.parent, "i2c transfer timed out\n");
			i2c->msg_status = -ETIMEDOUT;
			break;
		}

		if (i2c->msg_status)
			break;
	}

	clk_disable_unprepare(i2c->scb_clk);

	return i2c->msg_status ? i2c->msg_status : num;
}

static u32 img_i2c_func(struct i2c_adapter *adap)
{
	return I2C_FUNC_I2C | I2C_FUNC_SMBUS_EMUL;
}

static const struct i2c_algorithm img_i2c_algo = {
	.master_xfer = img_i2c_xfer,
	.functionality = img_i2c_func,
};

static int img_i2c_init(struct img_i2c *i2c)
{
	unsigned int clk_khz, bitrate_khz, clk_period, tckh, tckl, tsdh;
	unsigned int i, ret, data, prescale, inc, int_bitrate, filt;
	struct img_i2c_timings timing;
	u32 rev;

	ret = clk_prepare_enable(i2c->scb_clk);
	if (ret)
		return ret;

	rev = img_i2c_readl(i2c, SCB_CORE_REV_REG);
	if ((rev & 0x00ffffff) < 0x00020200) {
		dev_info(i2c->adap.dev.parent,
			 "Unknown hardware revision (%d.%d.%d.%d)\n",
			 (rev >> 24) & 0xff, (rev >> 16) & 0xff,
			 (rev >> 8) & 0xff, rev & 0xff);
		clk_disable_unprepare(i2c->scb_clk);
		return -EINVAL;
	}

	/* Fencing enabled by default. */
	i2c->need_wr_rd_fence = true;

	/* Determine what mode we're in from the bitrate */
	timing = timings[0];
	for (i = 0; i < ARRAY_SIZE(timings); i++) {
		if (i2c->bitrate <= timings[i].max_bitrate) {
			timing = timings[i];
			break;
		}
	}
	if (i2c->bitrate > timings[ARRAY_SIZE(timings) - 1].max_bitrate) {
		dev_warn(i2c->adap.dev.parent,
			 "requested bitrate (%u) is higher than the max bitrate supported (%u)\n",
			 i2c->bitrate,
			 timings[ARRAY_SIZE(timings) - 1].max_bitrate);
		timing = timings[ARRAY_SIZE(timings) - 1];
		i2c->bitrate = timing.max_bitrate;
	}

	bitrate_khz = i2c->bitrate / 1000;
	clk_khz = clk_get_rate(i2c->scb_clk) / 1000;

	/* Find the prescale that would give us that inc (approx delay = 0) */
	prescale = SCB_OPT_INC * clk_khz / (256 * 16 * bitrate_khz);
	prescale = clamp_t(unsigned int, prescale, 1, 8);
	clk_khz /= prescale;

	/* Setup the clock increment value */
	inc = (256 * 16 * bitrate_khz) / clk_khz;

	/*
	 * The clock generation logic allows to filter glitches on the bus.
	 * This filter is able to remove bus glitches shorter than 50ns.
	 * If the clock enable rate is greater than 20 MHz, no filtering
	 * is required, so we need to disable it.
	 * If it's between the 20-40 MHz range, there's no need to divide
	 * the clock to get a filter.
	 */
	if (clk_khz < 20000) {
		filt = SCB_FILT_DISABLE;
	} else if (clk_khz < 40000) {
		filt = SCB_FILT_BYPASS;
	} else {
		/* Calculate filter clock */
		filt = (64000 / ((clk_khz / 1000) * SCB_FILT_GLITCH));

		/* Scale up if needed */
		if (64000 % ((clk_khz / 1000) * SCB_FILT_GLITCH))
			inc++;

		if (filt > SCB_FILT_INC_MASK)
			filt = SCB_FILT_INC_MASK;

		filt = (filt & SCB_FILT_INC_MASK) << SCB_FILT_INC_SHIFT;
	}
	data = filt | ((inc & SCB_INC_MASK) << SCB_INC_SHIFT) | (prescale - 1);
	img_i2c_writel(i2c, SCB_CLK_SET_REG, data);

	/* Obtain the clock period of the fx16 clock in ns */
	clk_period = (256 * 1000000) / (clk_khz * inc);

	/* Calculate the bitrate in terms of internal clock pulses */
	int_bitrate = 1000000 / (bitrate_khz * clk_period);
	if ((1000000 % (bitrate_khz * clk_period)) >=
	    ((bitrate_khz * clk_period) / 2))
		int_bitrate++;

	/*
	 * Setup clock duty cycle, start with 50% and adjust TCKH and TCKL
	 * values from there if they don't meet minimum timing requirements
	 */
	tckh = int_bitrate / 2;
	tckl = int_bitrate - tckh;

	/* Adjust TCKH and TCKL values */
	data = DIV_ROUND_UP(timing.tckl, clk_period);

	if (tckl < data) {
		tckl = data;
		tckh = int_bitrate - tckl;
	}

	if (tckh > 0)
		--tckh;

	if (tckl > 0)
		--tckl;

	img_i2c_writel(i2c, SCB_TIME_TCKH_REG, tckh);
	img_i2c_writel(i2c, SCB_TIME_TCKL_REG, tckl);

	/* Setup TSDH value */
	tsdh = DIV_ROUND_UP(timing.tsdh, clk_period);

	if (tsdh > 1)
		data = tsdh - 1;
	else
		data = 0x01;
	img_i2c_writel(i2c, SCB_TIME_TSDH_REG, data);

	/* This value is used later */
	tsdh = data;

	/* Setup TPL value */
	data = timing.tpl / clk_period;
	if (data > 0)
		--data;
	img_i2c_writel(i2c, SCB_TIME_TPL_REG, data);

	/* Setup TPH value */
	data = timing.tph / clk_period;
	if (data > 0)
		--data;
	img_i2c_writel(i2c, SCB_TIME_TPH_REG, data);

	/* Setup TSDL value to TPL + TSDH + 2 */
	img_i2c_writel(i2c, SCB_TIME_TSDL_REG, data + tsdh + 2);

	/* Setup TP2S value */
	data = timing.tp2s / clk_period;
	if (data > 0)
		--data;
	img_i2c_writel(i2c, SCB_TIME_TP2S_REG, data);

	img_i2c_writel(i2c, SCB_TIME_TBI_REG, TIMEOUT_TBI);
	img_i2c_writel(i2c, SCB_TIME_TSL_REG, TIMEOUT_TSL);
	img_i2c_writel(i2c, SCB_TIME_TDL_REG, TIMEOUT_TDL);

	/* Take module out of soft reset and enable clocks */
	img_i2c_soft_reset(i2c);

	/* Disable all interrupts */
	img_i2c_writel(i2c, SCB_INT_MASK_REG, 0);

	/* Clear all interrupts */
	img_i2c_writel(i2c, SCB_INT_CLEAR_REG, ~0);

	/* Clear the scb_line_status events */
	img_i2c_writel(i2c, SCB_CLEAR_REG, ~0);

	/* Enable interrupts */
	img_i2c_writel(i2c, SCB_INT_MASK_REG, i2c->int_enable);

	/* Perform a synchronous sequence to reset the bus */
	ret = img_i2c_reset_bus(i2c);

	clk_disable_unprepare(i2c->scb_clk);

	return ret;
}

static int img_i2c_probe(struct platform_device *pdev)
{
	struct device_node *node = pdev->dev.of_node;
	struct img_i2c *i2c;
	struct resource *res;
	int irq, ret;
	u32 val;

	i2c = devm_kzalloc(&pdev->dev, sizeof(struct img_i2c), GFP_KERNEL);
	if (!i2c)
		return -ENOMEM;

	res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
	i2c->base = devm_ioremap_resource(&pdev->dev, res);
	if (IS_ERR(i2c->base))
		return PTR_ERR(i2c->base);

	irq = platform_get_irq(pdev, 0);
	if (irq < 0) {
		dev_err(&pdev->dev, "can't get irq number\n");
		return irq;
	}

	i2c->sys_clk = devm_clk_get(&pdev->dev, "sys");
	if (IS_ERR(i2c->sys_clk)) {
		dev_err(&pdev->dev, "can't get system clock\n");
		return PTR_ERR(i2c->sys_clk);
	}

	i2c->scb_clk = devm_clk_get(&pdev->dev, "scb");
	if (IS_ERR(i2c->scb_clk)) {
		dev_err(&pdev->dev, "can't get core clock\n");
		return PTR_ERR(i2c->scb_clk);
	}

	ret = devm_request_irq(&pdev->dev, irq, img_i2c_isr, 0,
			       pdev->name, i2c);
	if (ret) {
		dev_err(&pdev->dev, "can't request irq %d\n", irq);
		return ret;
	}

	/* Set up the exception check timer */
	init_timer(&i2c->check_timer);
	i2c->check_timer.function = img_i2c_check_timer;
	i2c->check_timer.data = (unsigned long)i2c;

	i2c->bitrate = timings[0].max_bitrate;
	if (!of_property_read_u32(node, "clock-frequency", &val))
		i2c->bitrate = val;

	i2c_set_adapdata(&i2c->adap, i2c);
	i2c->adap.dev.parent = &pdev->dev;
	i2c->adap.dev.of_node = node;
	i2c->adap.owner = THIS_MODULE;
	i2c->adap.algo = &img_i2c_algo;
	i2c->adap.retries = 5;
	i2c->adap.nr = pdev->id;
	snprintf(i2c->adap.name, sizeof(i2c->adap.name), "IMG SCB I2C");

	img_i2c_switch_mode(i2c, MODE_INACTIVE);
	spin_lock_init(&i2c->lock);
	init_completion(&i2c->msg_complete);

	platform_set_drvdata(pdev, i2c);

	ret = clk_prepare_enable(i2c->sys_clk);
	if (ret)
		return ret;

	ret = img_i2c_init(i2c);
	if (ret)
		goto disable_clk;

	ret = i2c_add_numbered_adapter(&i2c->adap);
	if (ret < 0) {
		dev_err(&pdev->dev, "failed to add adapter\n");
		goto disable_clk;
	}

	return 0;

disable_clk:
	clk_disable_unprepare(i2c->sys_clk);
	return ret;
}

static int img_i2c_remove(struct platform_device *dev)
{
	struct img_i2c *i2c = platform_get_drvdata(dev);

	i2c_del_adapter(&i2c->adap);
	clk_disable_unprepare(i2c->sys_clk);

	return 0;
}

#ifdef CONFIG_PM_SLEEP
static int img_i2c_suspend(struct device *dev)
{
	struct img_i2c *i2c = dev_get_drvdata(dev);

	img_i2c_switch_mode(i2c, MODE_SUSPEND);

	clk_disable_unprepare(i2c->sys_clk);

	return 0;
}

static int img_i2c_resume(struct device *dev)
{
	struct img_i2c *i2c = dev_get_drvdata(dev);
	int ret;

	ret = clk_prepare_enable(i2c->sys_clk);
	if (ret)
		return ret;

	img_i2c_init(i2c);

	return 0;
}
#endif /* CONFIG_PM_SLEEP */

static SIMPLE_DEV_PM_OPS(img_i2c_pm, img_i2c_suspend, img_i2c_resume);

static const struct of_device_id img_scb_i2c_match[] = {
	{ .compatible = "img,scb-i2c" },
	{ }
};
MODULE_DEVICE_TABLE(of, img_scb_i2c_match);

static struct platform_driver img_scb_i2c_driver = {
	.driver = {
		.name		= "img-i2c-scb",
		.of_match_table	= img_scb_i2c_match,
		.pm		= &img_i2c_pm,
	},
	.probe = img_i2c_probe,
	.remove = img_i2c_remove,
};
module_platform_driver(img_scb_i2c_driver);

MODULE_AUTHOR("James Hogan <james.hogan@imgtec.com>");
MODULE_DESCRIPTION("IMG host I2C driver");
MODULE_LICENSE("GPL v2");