summaryrefslogtreecommitdiff
path: root/drivers/iio/light/rohm-bu27034.c
blob: bf3de853a811dccaefcba995a2e7151120be5397 (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
1468
1469
1470
1471
1472
1473
1474
1475
1476
1477
1478
1479
1480
1481
1482
1483
1484
1485
1486
1487
1488
1489
1490
1491
1492
1493
1494
1495
1496
1497
1498
1499
1500
1501
1502
1503
1504
1505
1506
1507
1508
1509
1510
1511
1512
1513
1514
1515
1516
1517
1518
1519
1520
1521
1522
1523
1524
1525
1526
1527
1528
// SPDX-License-Identifier: GPL-2.0-only
/*
 * BU27034 ROHM Ambient Light Sensor
 *
 * Copyright (c) 2023, ROHM Semiconductor.
 * https://fscdn.rohm.com/en/products/databook/datasheet/ic/sensor/light/bu27034nuc-e.pdf
 */

#include <linux/bitfield.h>
#include <linux/bits.h>
#include <linux/device.h>
#include <linux/i2c.h>
#include <linux/module.h>
#include <linux/property.h>
#include <linux/regmap.h>
#include <linux/regulator/consumer.h>
#include <linux/units.h>

#include <linux/iio/buffer.h>
#include <linux/iio/iio.h>
#include <linux/iio/iio-gts-helper.h>
#include <linux/iio/kfifo_buf.h>

#define BU27034_REG_SYSTEM_CONTROL	0x40
#define BU27034_MASK_SW_RESET		BIT(7)
#define BU27034_MASK_PART_ID		GENMASK(5, 0)
#define BU27034_ID			0x19
#define BU27034_REG_MODE_CONTROL1	0x41
#define BU27034_MASK_MEAS_MODE		GENMASK(2, 0)

#define BU27034_REG_MODE_CONTROL2	0x42
#define BU27034_MASK_D01_GAIN		GENMASK(7, 3)
#define BU27034_MASK_D2_GAIN_HI		GENMASK(7, 6)
#define BU27034_MASK_D2_GAIN_LO		GENMASK(2, 0)

#define BU27034_REG_MODE_CONTROL3	0x43
#define BU27034_REG_MODE_CONTROL4	0x44
#define BU27034_MASK_MEAS_EN		BIT(0)
#define BU27034_MASK_VALID		BIT(7)
#define BU27034_REG_DATA0_LO		0x50
#define BU27034_REG_DATA1_LO		0x52
#define BU27034_REG_DATA2_LO		0x54
#define BU27034_REG_DATA2_HI		0x55
#define BU27034_REG_MANUFACTURER_ID	0x92
#define BU27034_REG_MAX BU27034_REG_MANUFACTURER_ID

/*
 * The BU27034 does not have interrupt to trigger the data read when a
 * measurement has finished. Hence we poll the VALID bit in a thread. We will
 * try to wake the thread BU27034_MEAS_WAIT_PREMATURE_MS milliseconds before
 * the expected sampling time to prevent the drifting.
 *
 * If we constantly wake up a bit too late we would eventually skip a sample.
 * And because the sleep can't wake up _exactly_ at given time this would be
 * inevitable even if the sensor clock would be perfectly phase-locked to CPU
 * clock - which we can't say is the case.
 *
 * This is still fragile. No matter how big advance do we have, we will still
 * risk of losing a sample because things can in a rainy-day scenario be
 * delayed a lot. Yet, more we reserve the time for polling, more we also lose
 * the performance by spending cycles polling the register. So, selecting this
 * value is a balancing dance between severity of wasting CPU time and severity
 * of losing samples.
 *
 * In most cases losing the samples is not _that_ crucial because light levels
 * tend to change slowly.
 *
 * Other option that was pointed to me would be always sleeping 1/2 of the
 * measurement time, checking the VALID bit and just sleeping again if the bit
 * was not set. That should be pretty tolerant against missing samples due to
 * the scheduling delays while also not wasting much of cycles for polling.
 * Downside is that the time-stamps would be very inaccurate as the wake-up
 * would not really be tied to the sensor toggling the valid bit. This would also
 * result 'jumps' in the time-stamps when the delay drifted so that wake-up was
 * performed during the consecutive wake-ups (Or, when sensor and CPU clocks
 * were very different and scheduling the wake-ups was very close to given
 * timeout - and when the time-outs were very close to the actual sensor
 * sampling, Eg. once in a blue moon, two consecutive time-outs would occur
 * without having a sample ready).
 */
#define BU27034_MEAS_WAIT_PREMATURE_MS	5
#define BU27034_DATA_WAIT_TIME_US	1000
#define BU27034_TOTAL_DATA_WAIT_TIME_US (BU27034_MEAS_WAIT_PREMATURE_MS * 1000)

#define BU27034_RETRY_LIMIT 18

enum {
	BU27034_CHAN_ALS,
	BU27034_CHAN_DATA0,
	BU27034_CHAN_DATA1,
	BU27034_CHAN_DATA2,
	BU27034_NUM_CHANS
};

static const unsigned long bu27034_scan_masks[] = {
	GENMASK(BU27034_CHAN_DATA2, BU27034_CHAN_ALS), 0
};

/*
 * Available scales with gain 1x - 4096x, timings 55, 100, 200, 400 mS
 * Time impacts to gain: 1x, 2x, 4x, 8x.
 *
 * => Max total gain is HWGAIN * gain by integration time (8 * 4096) = 32768
 *
 * Using NANO precision for scale we must use scale 64x corresponding gain 1x
 * to avoid precision loss. (32x would result scale 976 562.5(nanos).
 */
#define BU27034_SCALE_1X	64

/* See the data sheet for the "Gain Setting" table */
#define BU27034_GSEL_1X		0x00 /* 00000 */
#define BU27034_GSEL_4X		0x08 /* 01000 */
#define BU27034_GSEL_16X	0x0a /* 01010 */
#define BU27034_GSEL_32X	0x0b /* 01011 */
#define BU27034_GSEL_64X	0x0c /* 01100 */
#define BU27034_GSEL_256X	0x18 /* 11000 */
#define BU27034_GSEL_512X	0x19 /* 11001 */
#define BU27034_GSEL_1024X	0x1a /* 11010 */
#define BU27034_GSEL_2048X	0x1b /* 11011 */
#define BU27034_GSEL_4096X	0x1c /* 11100 */

/* Available gain settings */
static const struct iio_gain_sel_pair bu27034_gains[] = {
	GAIN_SCALE_GAIN(1, BU27034_GSEL_1X),
	GAIN_SCALE_GAIN(4, BU27034_GSEL_4X),
	GAIN_SCALE_GAIN(16, BU27034_GSEL_16X),
	GAIN_SCALE_GAIN(32, BU27034_GSEL_32X),
	GAIN_SCALE_GAIN(64, BU27034_GSEL_64X),
	GAIN_SCALE_GAIN(256, BU27034_GSEL_256X),
	GAIN_SCALE_GAIN(512, BU27034_GSEL_512X),
	GAIN_SCALE_GAIN(1024, BU27034_GSEL_1024X),
	GAIN_SCALE_GAIN(2048, BU27034_GSEL_2048X),
	GAIN_SCALE_GAIN(4096, BU27034_GSEL_4096X),
};

/*
 * The IC has 5 modes for sampling time. 5 mS mode is exceptional as it limits
 * the data collection to data0-channel only and cuts the supported range to
 * 10 bit. It is not supported by the driver.
 *
 * "normal" modes are 55, 100, 200 and 400 mS modes - which do have direct
 * multiplying impact to the register values (similar to gain).
 *
 * This means that if meas-mode is changed for example from 400 => 200,
 * the scale is doubled. Eg, time impact to total gain is x1, x2, x4, x8.
 */
#define BU27034_MEAS_MODE_100MS		0
#define BU27034_MEAS_MODE_55MS		1
#define BU27034_MEAS_MODE_200MS		2
#define BU27034_MEAS_MODE_400MS		4

static const struct iio_itime_sel_mul bu27034_itimes[] = {
	GAIN_SCALE_ITIME_US(400000, BU27034_MEAS_MODE_400MS, 8),
	GAIN_SCALE_ITIME_US(200000, BU27034_MEAS_MODE_200MS, 4),
	GAIN_SCALE_ITIME_US(100000, BU27034_MEAS_MODE_100MS, 2),
	GAIN_SCALE_ITIME_US(55000, BU27034_MEAS_MODE_55MS, 1),
};

#define BU27034_CHAN_DATA(_name, _ch2)					\
{									\
	.type = IIO_INTENSITY,						\
	.channel = BU27034_CHAN_##_name,				\
	.channel2 = (_ch2),						\
	.info_mask_separate = BIT(IIO_CHAN_INFO_RAW) |			\
			      BIT(IIO_CHAN_INFO_SCALE),			\
	.info_mask_separate_available = BIT(IIO_CHAN_INFO_SCALE),	\
	.info_mask_shared_by_all = BIT(IIO_CHAN_INFO_INT_TIME),		\
	.info_mask_shared_by_all_available =				\
					BIT(IIO_CHAN_INFO_INT_TIME),	\
	.address = BU27034_REG_##_name##_LO,				\
	.scan_index = BU27034_CHAN_##_name,				\
	.scan_type = {							\
		.sign = 'u',						\
		.realbits = 16,						\
		.storagebits = 16,					\
		.endianness = IIO_LE,					\
	},								\
	.indexed = 1,							\
}

static const struct iio_chan_spec bu27034_channels[] = {
	{
		.type = IIO_LIGHT,
		.info_mask_separate = BIT(IIO_CHAN_INFO_RAW) |
				      BIT(IIO_CHAN_INFO_SCALE),
		.channel = BU27034_CHAN_ALS,
		.scan_index = BU27034_CHAN_ALS,
		.scan_type = {
			.sign = 'u',
			.realbits = 32,
			.storagebits = 32,
			.endianness = IIO_CPU,
		},
	},
	/*
	 * The BU27034 DATA0 and DATA1 channels are both on the visible light
	 * area (mostly). The data0 sensitivity peaks at 500nm, DATA1 at 600nm.
	 * These wave lengths are pretty much on the border of colours making
	 * these a poor candidates for R/G/B standardization. Hence they're both
	 * marked as clear channels
	 */
	BU27034_CHAN_DATA(DATA0, IIO_MOD_LIGHT_CLEAR),
	BU27034_CHAN_DATA(DATA1, IIO_MOD_LIGHT_CLEAR),
	BU27034_CHAN_DATA(DATA2, IIO_MOD_LIGHT_IR),
	IIO_CHAN_SOFT_TIMESTAMP(4),
};

struct bu27034_data {
	struct regmap *regmap;
	struct device *dev;
	/*
	 * Protect gain and time during scale adjustment and data reading.
	 * Protect measurement enabling/disabling.
	 */
	struct mutex mutex;
	struct iio_gts gts;
	struct task_struct *task;
	__le16 raw[3];
	struct {
		u32 mlux;
		__le16 channels[3];
		s64 ts __aligned(8);
	} scan;
};

struct bu27034_result {
	u16 ch0;
	u16 ch1;
	u16 ch2;
};

static const struct regmap_range bu27034_volatile_ranges[] = {
	{
		.range_min = BU27034_REG_SYSTEM_CONTROL,
		.range_max = BU27034_REG_SYSTEM_CONTROL,
	}, {
		.range_min = BU27034_REG_MODE_CONTROL4,
		.range_max = BU27034_REG_MODE_CONTROL4,
	}, {
		.range_min = BU27034_REG_DATA0_LO,
		.range_max = BU27034_REG_DATA2_HI,
	},
};

static const struct regmap_access_table bu27034_volatile_regs = {
	.yes_ranges = &bu27034_volatile_ranges[0],
	.n_yes_ranges = ARRAY_SIZE(bu27034_volatile_ranges),
};

static const struct regmap_range bu27034_read_only_ranges[] = {
	{
		.range_min = BU27034_REG_DATA0_LO,
		.range_max = BU27034_REG_DATA2_HI,
	}, {
		.range_min = BU27034_REG_MANUFACTURER_ID,
		.range_max = BU27034_REG_MANUFACTURER_ID,
	}
};

static const struct regmap_access_table bu27034_ro_regs = {
	.no_ranges = &bu27034_read_only_ranges[0],
	.n_no_ranges = ARRAY_SIZE(bu27034_read_only_ranges),
};

static const struct regmap_config bu27034_regmap = {
	.reg_bits = 8,
	.val_bits = 8,
	.max_register = BU27034_REG_MAX,
	.cache_type = REGCACHE_RBTREE,
	.volatile_table = &bu27034_volatile_regs,
	.wr_table = &bu27034_ro_regs,
};

struct bu27034_gain_check {
	int old_gain;
	int new_gain;
	int chan;
};

static int bu27034_get_gain_sel(struct bu27034_data *data, int chan)
{
	int ret, val;

	switch (chan) {
	case BU27034_CHAN_DATA0:
	case BU27034_CHAN_DATA1:
	{
		int reg[] = {
			[BU27034_CHAN_DATA0] = BU27034_REG_MODE_CONTROL2,
			[BU27034_CHAN_DATA1] = BU27034_REG_MODE_CONTROL3,
		};
		ret = regmap_read(data->regmap, reg[chan], &val);
		if (ret)
			return ret;

		return FIELD_GET(BU27034_MASK_D01_GAIN, val);
	}
	case BU27034_CHAN_DATA2:
	{
		int d2_lo_bits = fls(BU27034_MASK_D2_GAIN_LO);

		ret = regmap_read(data->regmap, BU27034_REG_MODE_CONTROL2, &val);
		if (ret)
			return ret;

		/*
		 * The data2 channel gain is composed by 5 non continuous bits
		 * [7:6], [2:0]. Thus when we combine the 5-bit 'selector'
		 * from register value we must right shift the high bits by 3.
		 */
		return FIELD_GET(BU27034_MASK_D2_GAIN_HI, val) << d2_lo_bits |
		       FIELD_GET(BU27034_MASK_D2_GAIN_LO, val);
	}
	default:
		return -EINVAL;
	}
}

static int bu27034_get_gain(struct bu27034_data *data, int chan, int *gain)
{
	int ret, sel;

	ret = bu27034_get_gain_sel(data, chan);
	if (ret < 0)
		return ret;

	sel = ret;

	ret = iio_gts_find_gain_by_sel(&data->gts, sel);
	if (ret < 0) {
		dev_err(data->dev, "chan %u: unknown gain value 0x%x\n", chan,
			sel);

		return ret;
	}

	*gain = ret;

	return 0;
}

static int bu27034_get_int_time(struct bu27034_data *data)
{
	int ret, sel;

	ret = regmap_read(data->regmap, BU27034_REG_MODE_CONTROL1, &sel);
	if (ret)
		return ret;

	return iio_gts_find_int_time_by_sel(&data->gts,
					    sel & BU27034_MASK_MEAS_MODE);
}

static int _bu27034_get_scale(struct bu27034_data *data, int channel, int *val,
			      int *val2)
{
	int gain, ret;

	ret = bu27034_get_gain(data, channel, &gain);
	if (ret)
		return ret;

	ret = bu27034_get_int_time(data);
	if (ret < 0)
		return ret;

	return iio_gts_get_scale(&data->gts, gain, ret, val, val2);
}

static int bu27034_get_scale(struct bu27034_data *data, int channel, int *val,
			      int *val2)
{
	int ret;

	if (channel == BU27034_CHAN_ALS) {
		*val = 0;
		*val2 = 1000;
		return IIO_VAL_INT_PLUS_MICRO;
	}

	mutex_lock(&data->mutex);
	ret = _bu27034_get_scale(data, channel, val, val2);
	mutex_unlock(&data->mutex);
	if (ret)
		return ret;

	return IIO_VAL_INT_PLUS_NANO;
}

/* Caller should hold the lock to protect lux reading */
static int bu27034_write_gain_sel(struct bu27034_data *data, int chan, int sel)
{
	static const int reg[] = {
		[BU27034_CHAN_DATA0] = BU27034_REG_MODE_CONTROL2,
		[BU27034_CHAN_DATA1] = BU27034_REG_MODE_CONTROL3,
	};
	int mask, val;

	if (chan != BU27034_CHAN_DATA0 && chan != BU27034_CHAN_DATA1)
		return -EINVAL;

	val = FIELD_PREP(BU27034_MASK_D01_GAIN, sel);

	mask = BU27034_MASK_D01_GAIN;

	if (chan == BU27034_CHAN_DATA0) {
		/*
		 * We keep the same gain for channel 2 as we set for channel 0
		 * We can't allow them to be individually controlled because
		 * setting one will impact also the other. Also, if we don't
		 * always update both gains we may result unsupported bit
		 * combinations.
		 *
		 * This is not nice but this is yet another place where the
		 * user space must be prepared to surprizes. Namely, see chan 2
		 * gain changed when chan 0 gain is changed.
		 *
		 * This is not fatal for most users though. I don't expect the
		 * channel 2 to be used in any generic cases - the intensity
		 * values provided by the sensor for IR area are not openly
		 * documented. Also, channel 2 is not used for visible light.
		 *
		 * So, if there is application which is written to utilize the
		 * channel 2 - then it is probably specifically targeted to this
		 * sensor and knows how to utilize those values. It is safe to
		 * hope such user can also cope with the gain changes.
		 */
		mask |=  BU27034_MASK_D2_GAIN_LO;

		/*
		 * The D2 gain bits are directly the lowest bits of selector.
		 * Just do add those bits to the value
		 */
		val |= sel & BU27034_MASK_D2_GAIN_LO;
	}

	return regmap_update_bits(data->regmap, reg[chan], mask, val);
}

static int bu27034_set_gain(struct bu27034_data *data, int chan, int gain)
{
	int ret;

	/*
	 * We don't allow setting channel 2 gain as it messes up the
	 * gain for channel 0 - which shares the high bits
	 */
	if (chan != BU27034_CHAN_DATA0 && chan != BU27034_CHAN_DATA1)
		return -EINVAL;

	ret = iio_gts_find_sel_by_gain(&data->gts, gain);
	if (ret < 0)
		return ret;

	return bu27034_write_gain_sel(data, chan, ret);
}

/* Caller should hold the lock to protect data->int_time */
static int bu27034_set_int_time(struct bu27034_data *data, int time)
{
	int ret;

	ret = iio_gts_find_sel_by_int_time(&data->gts, time);
	if (ret < 0)
		return ret;

	return regmap_update_bits(data->regmap, BU27034_REG_MODE_CONTROL1,
				 BU27034_MASK_MEAS_MODE, ret);
}

/*
 * We try to change the time in such way that the scale is maintained for
 * given channels by adjusting gain so that it compensates the time change.
 */
static int bu27034_try_set_int_time(struct bu27034_data *data, int time_us)
{
	struct bu27034_gain_check gains[] = {
		{ .chan = BU27034_CHAN_DATA0 },
		{ .chan = BU27034_CHAN_DATA1 },
	};
	int numg = ARRAY_SIZE(gains);
	int ret, int_time_old, i;

	mutex_lock(&data->mutex);
	ret = bu27034_get_int_time(data);
	if (ret < 0)
		goto unlock_out;

	int_time_old = ret;

	if (!iio_gts_valid_time(&data->gts, time_us)) {
		dev_err(data->dev, "Unsupported integration time %u\n",
			time_us);
		ret = -EINVAL;

		goto unlock_out;
	}

	if (time_us == int_time_old) {
		ret = 0;
		goto unlock_out;
	}

	for (i = 0; i < numg; i++) {
		ret = bu27034_get_gain(data, gains[i].chan, &gains[i].old_gain);
		if (ret)
			goto unlock_out;

		ret = iio_gts_find_new_gain_by_old_gain_time(&data->gts,
							     gains[i].old_gain,
							     int_time_old, time_us,
							     &gains[i].new_gain);
		if (ret) {
			int scale1, scale2;
			bool ok;

			_bu27034_get_scale(data, gains[i].chan, &scale1, &scale2);
			dev_dbg(data->dev,
				"chan %u, can't support time %u with scale %u %u\n",
				gains[i].chan, time_us, scale1, scale2);

			if (gains[i].new_gain < 0)
				goto unlock_out;

			/*
			 * If caller requests for integration time change and we
			 * can't support the scale - then the caller should be
			 * prepared to 'pick up the pieces and deal with the
			 * fact that the scale changed'.
			 */
			ret = iio_find_closest_gain_low(&data->gts,
							gains[i].new_gain, &ok);

			if (!ok)
				dev_dbg(data->dev,
					"optimal gain out of range for chan %u\n",
					gains[i].chan);

			if (ret < 0) {
				dev_dbg(data->dev,
					 "Total gain increase. Risk of saturation");
				ret = iio_gts_get_min_gain(&data->gts);
				if (ret < 0)
					goto unlock_out;
			}
			dev_dbg(data->dev, "chan %u scale changed\n",
				 gains[i].chan);
			gains[i].new_gain = ret;
			dev_dbg(data->dev, "chan %u new gain %u\n",
				gains[i].chan, gains[i].new_gain);
		}
	}

	for (i = 0; i < numg; i++) {
		ret = bu27034_set_gain(data, gains[i].chan, gains[i].new_gain);
		if (ret)
			goto unlock_out;
	}

	ret = bu27034_set_int_time(data, time_us);

unlock_out:
	mutex_unlock(&data->mutex);

	return ret;
}

static int bu27034_set_scale(struct bu27034_data *data, int chan,
			    int val, int val2)
{
	int ret, time_sel, gain_sel, i;
	bool found = false;

	if (chan == BU27034_CHAN_DATA2)
		return -EINVAL;

	if (chan == BU27034_CHAN_ALS) {
		if (val == 0 && val2 == 1000000)
			return 0;

		return -EINVAL;
	}

	mutex_lock(&data->mutex);
	ret = regmap_read(data->regmap, BU27034_REG_MODE_CONTROL1, &time_sel);
	if (ret)
		goto unlock_out;

	ret = iio_gts_find_gain_sel_for_scale_using_time(&data->gts, time_sel,
						val, val2, &gain_sel);
	if (ret) {
		/*
		 * Could not support scale with given time. Need to change time.
		 * We still want to maintain the scale for all channels
		 */
		struct bu27034_gain_check gain;
		int new_time_sel;

		/*
		 * Populate information for the other channel which should also
		 * maintain the scale. (Due to the HW limitations the chan2
		 * gets the same gain as chan0, so we only need to explicitly
		 * set the chan 0 and 1).
		 */
		if (chan == BU27034_CHAN_DATA0)
			gain.chan = BU27034_CHAN_DATA1;
		else if (chan == BU27034_CHAN_DATA1)
			gain.chan = BU27034_CHAN_DATA0;

		ret = bu27034_get_gain(data, gain.chan, &gain.old_gain);
		if (ret)
			goto unlock_out;

		/*
		 * Iterate through all the times to see if we find one which
		 * can support requested scale for requested channel, while
		 * maintaining the scale for other channels
		 */
		for (i = 0; i < data->gts.num_itime; i++) {
			new_time_sel = data->gts.itime_table[i].sel;

			if (new_time_sel == time_sel)
				continue;

			/* Can we provide requested scale with this time? */
			ret = iio_gts_find_gain_sel_for_scale_using_time(
				&data->gts, new_time_sel, val, val2,
				&gain_sel);
			if (ret)
				continue;

			/* Can the other channel(s) maintain scale? */
			ret = iio_gts_find_new_gain_sel_by_old_gain_time(
				&data->gts, gain.old_gain, time_sel,
				new_time_sel, &gain.new_gain);
			if (!ret) {
				/* Yes - we found suitable time */
				found = true;
				break;
			}
		}
		if (!found) {
			dev_dbg(data->dev,
				"Can't set scale maintaining other channels\n");
			ret = -EINVAL;

			goto unlock_out;
		}

		ret = bu27034_set_gain(data, gain.chan, gain.new_gain);
		if (ret)
			goto unlock_out;

		ret = regmap_update_bits(data->regmap, BU27034_REG_MODE_CONTROL1,
				  BU27034_MASK_MEAS_MODE, new_time_sel);
		if (ret)
			goto unlock_out;
	}

	ret = bu27034_write_gain_sel(data, chan, gain_sel);
unlock_out:
	mutex_unlock(&data->mutex);

	return ret;
}

/*
 * for (D1/D0 < 0.87):
 * lx = 0.004521097 * D1 - 0.002663996 * D0 +
 *	0.00012213 * D1 * D1 / D0
 *
 * =>	115.7400832 * ch1 / gain1 / mt -
 *	68.1982976 * ch0 / gain0 / mt +
 *	0.00012213 * 25600 * (ch1 / gain1 / mt) * 25600 *
 *	(ch1 /gain1 / mt) / (25600 * ch0 / gain0 / mt)
 *
 * A =	0.00012213 * 25600 * (ch1 /gain1 / mt) * 25600 *
 *	(ch1 /gain1 / mt) / (25600 * ch0 / gain0 / mt)
 * =>	0.00012213 * 25600 * (ch1 /gain1 / mt) *
 *	(ch1 /gain1 / mt) / (ch0 / gain0 / mt)
 * =>	0.00012213 * 25600 * (ch1 / gain1) * (ch1 /gain1 / mt) /
 *	(ch0 / gain0)
 * =>	0.00012213 * 25600 * (ch1 / gain1) * (ch1 /gain1 / mt) *
 *	gain0 / ch0
 * =>	3.126528 * ch1 * ch1 * gain0 / gain1 / gain1 / mt /ch0
 *
 * lx = (115.7400832 * ch1 / gain1 - 68.1982976 * ch0 / gain0) /
 *	mt + A
 * =>	(115.7400832 * ch1 / gain1 - 68.1982976 * ch0 / gain0) /
 *	mt + 3.126528 * ch1 * ch1 * gain0 / gain1 / gain1 / mt /
 *	ch0
 *
 * =>	(115.7400832 * ch1 / gain1 - 68.1982976 * ch0 / gain0 +
 *	  3.126528 * ch1 * ch1 * gain0 / gain1 / gain1 / ch0) /
 *	  mt
 *
 * For (0.87 <= D1/D0 < 1.00)
 * lx = (0.001331* D0 + 0.0000354 * D1) * ((D1/D0 – 0.87) * (0.385) + 1)
 * =>	(0.001331 * 256 * 100 * ch0 / gain0 / mt + 0.0000354 * 256 *
 *	100 * ch1 / gain1 / mt) * ((D1/D0 -  0.87) * (0.385) + 1)
 * =>	(34.0736 * ch0 / gain0 / mt + 0.90624 * ch1 / gain1 / mt) *
 *	((D1/D0 -  0.87) * (0.385) + 1)
 * =>	(34.0736 * ch0 / gain0 / mt + 0.90624 * ch1 / gain1 / mt) *
 *	(0.385 * D1/D0 - 0.66505)
 * =>	(34.0736 * ch0 / gain0 / mt + 0.90624 * ch1 / gain1 / mt) *
 *	(0.385 * 256 * 100 * ch1 / gain1 / mt / (256 * 100 * ch0 / gain0 / mt) - 0.66505)
 * =>	(34.0736 * ch0 / gain0 / mt + 0.90624 * ch1 / gain1 / mt) *
 *	(9856 * ch1 / gain1 / mt / (25600 * ch0 / gain0 / mt) + 0.66505)
 * =>	13.118336 * ch1 / (gain1 * mt)
 *	+ 22.66064768 * ch0 / (gain0 * mt)
 *	+ 8931.90144 * ch1 * ch1 * gain0 /
 *	  (25600 * ch0 * gain1 * gain1 * mt)
 *	+ 0.602694912 * ch1 / (gain1 * mt)
 *
 * =>	[0.3489024 * ch1 * ch1 * gain0 / (ch0 * gain1 * gain1)
 *	 + 22.66064768 * ch0 / gain0
 *	 + 13.721030912 * ch1 / gain1
 *	] / mt
 *
 * For (D1/D0 >= 1.00)
 *
 * lx	= (0.001331* D0 + 0.0000354 * D1) * ((D1/D0 – 2.0) * (-0.05) + 1)
 *	=> (0.001331* D0 + 0.0000354 * D1) * (-0.05D1/D0 + 1.1)
 *	=> (0.001331 * 256 * 100 * ch0 / gain0 / mt + 0.0000354 * 256 *
 *	   100 * ch1 / gain1 / mt) * (-0.05D1/D0 + 1.1)
 *	=> (34.0736 * ch0 / gain0 / mt + 0.90624 * ch1 / gain1 / mt) *
 *	   (-0.05 * 256 * 100 * ch1 / gain1 / mt / (256 * 100 * ch0 / gain0 / mt) + 1.1)
 *	=> (34.0736 * ch0 / gain0 / mt + 0.90624 * ch1 / gain1 / mt) *
 *	   (-1280 * ch1 / (gain1 * mt * 25600 * ch0 / gain0 / mt) + 1.1)
 *	=> (34.0736 * ch0 * -1280 * ch1 * gain0 * mt /( gain0 * mt * gain1 * mt * 25600 * ch0)
 *	    + 34.0736 * 1.1 * ch0 / (gain0 * mt)
 *	    + 0.90624 * ch1 * -1280 * ch1 *gain0 * mt / (gain1 * mt *gain1 * mt * 25600 * ch0)
 *	    + 1.1 * 0.90624 * ch1 / (gain1 * mt)
 *	=> -43614.208 * ch1 / (gain1 * mt * 25600)
 *	    + 37.48096  ch0 / (gain0 * mt)
 *	    - 1159.9872 * ch1 * ch1 * gain0 / (gain1 * gain1 * mt * 25600 * ch0)
 *	    + 0.996864 ch1 / (gain1 * mt)
 *	=> [
 *		- 0.045312 * ch1 * ch1 * gain0 / (gain1 * gain1 * ch0)
 *		- 0.706816 * ch1 / gain1
 *		+ 37.48096  ch0 /gain0
 *	   ] * mt
 *
 *
 * So, the first case (D1/D0 < 0.87) can be computed to a form:
 *
 * lx = (3.126528 * ch1 * ch1 * gain0 / (ch0 * gain1 * gain1) +
 *	 115.7400832 * ch1 / gain1 +
 *	-68.1982976 * ch0 / gain0
 *	 / mt
 *
 * Second case (0.87 <= D1/D0 < 1.00) goes to form:
 *
 *	=> [0.3489024 * ch1 * ch1 * gain0 / (ch0 * gain1 * gain1) +
 *	    13.721030912 * ch1 / gain1 +
 *	    22.66064768 * ch0 / gain0
 *	   ] / mt
 *
 * Third case (D1/D0 >= 1.00) goes to form:
 *	=> [-0.045312 * ch1 * ch1 * gain0 / (ch0 * gain1 * gain1) +
 *	    -0.706816 * ch1 / gain1 +
 *	    37.48096  ch0 /(gain0
 *	   ] / mt
 *
 * This can be unified to format:
 * lx = [
 *	 A * ch1 * ch1 * gain0 / (ch0 * gain1 * gain1) +
 *	 B * ch1 / gain1 +
 *	 C * ch0 / gain0
 *	] / mt
 *
 * For case 1:
 * A = 3.126528,
 * B = 115.7400832
 * C = -68.1982976
 *
 * For case 2:
 * A = 0.3489024
 * B = 13.721030912
 * C = 22.66064768
 *
 * For case 3:
 * A = -0.045312
 * B = -0.706816
 * C = 37.48096
 */

struct bu27034_lx_coeff {
	unsigned int A;
	unsigned int B;
	unsigned int C;
	/* Indicate which of the coefficients above are negative */
	bool is_neg[3];
};

static inline u64 gain_mul_div_helper(u64 val, unsigned int gain,
				      unsigned int div)
{
	/*
	 * Max gain for a channel is 4096. The max u64 (0xffffffffffffffffULL)
	 * divided by 4096 is 0xFFFFFFFFFFFFF (GENMASK_ULL(51, 0)) (floored).
	 * Thus, the 0xFFFFFFFFFFFFF is the largest value we can safely multiply
	 * with the gain, no matter what gain is set.
	 *
	 * So, multiplication with max gain may overflow if val is greater than
	 * 0xFFFFFFFFFFFFF (52 bits set)..
	 *
	 * If this is the case we divide first.
	 */
	if (val < GENMASK_ULL(51, 0)) {
		val *= gain;
		do_div(val, div);
	} else {
		do_div(val, div);
		val *= gain;
	}

	return val;
}

static u64 bu27034_fixp_calc_t1_64bit(unsigned int coeff, unsigned int ch0,
				      unsigned int ch1, unsigned int gain0,
				      unsigned int gain1)
{
	unsigned int helper;
	u64 helper64;

	helper64 = (u64)coeff * (u64)ch1 * (u64)ch1;

	helper = gain1 * gain1;
	if (helper > ch0) {
		do_div(helper64, helper);

		return gain_mul_div_helper(helper64, gain0, ch0);
	}

	do_div(helper64, ch0);

	return gain_mul_div_helper(helper64, gain0, helper);

}

static u64 bu27034_fixp_calc_t1(unsigned int coeff, unsigned int ch0,
				unsigned int ch1, unsigned int gain0,
				unsigned int gain1)
{
	unsigned int helper, tmp;

	/*
	 * Here we could overflow even the 64bit value. Hence we
	 * multiply with gain0 only after the divisions - even though
	 * it may result loss of accuracy
	 */
	helper = coeff * ch1 * ch1;
	tmp = helper * gain0;

	helper = ch1 * ch1;

	if (check_mul_overflow(helper, coeff, &helper))
		return bu27034_fixp_calc_t1_64bit(coeff, ch0, ch1, gain0, gain1);

	if (check_mul_overflow(helper, gain0, &tmp))
		return bu27034_fixp_calc_t1_64bit(coeff, ch0, ch1, gain0, gain1);

	return tmp / (gain1 * gain1) / ch0;

}

static u64 bu27034_fixp_calc_t23(unsigned int coeff, unsigned int ch,
				 unsigned int gain)
{
	unsigned int helper;
	u64 helper64;

	if (!check_mul_overflow(coeff, ch, &helper))
		return helper / gain;

	helper64 = (u64)coeff * (u64)ch;
	do_div(helper64, gain);

	return helper64;
}

static int bu27034_fixp_calc_lx(unsigned int ch0, unsigned int ch1,
				unsigned int gain0, unsigned int gain1,
				unsigned int meastime, int coeff_idx)
{
	static const struct bu27034_lx_coeff coeff[] = {
		{
			.A = 31265280,		/* 3.126528 */
			.B = 1157400832,	/*115.7400832 */
			.C = 681982976,		/* -68.1982976 */
			.is_neg = {false, false, true},
		}, {
			.A = 3489024,		/* 0.3489024 */
			.B = 137210309,		/* 13.721030912 */
			.C = 226606476,		/* 22.66064768 */
			/* All terms positive */
		}, {
			.A = 453120,		/* -0.045312 */
			.B = 7068160,		/* -0.706816 */
			.C = 374809600,		/* 37.48096 */
			.is_neg = {true, true, false},
		}
	};
	const struct bu27034_lx_coeff *c = &coeff[coeff_idx];
	u64 res = 0, terms[3];
	int i;

	if (coeff_idx >= ARRAY_SIZE(coeff))
		return -EINVAL;

	terms[0] = bu27034_fixp_calc_t1(c->A, ch0, ch1, gain0, gain1);
	terms[1] = bu27034_fixp_calc_t23(c->B, ch1, gain1);
	terms[2] = bu27034_fixp_calc_t23(c->C, ch0, gain0);

	/* First, add positive terms */
	for (i = 0; i < 3; i++)
		if (!c->is_neg[i])
			res += terms[i];

	/* No positive term => zero lux */
	if (!res)
		return 0;

	/* Then, subtract negative terms (if any) */
	for (i = 0; i < 3; i++)
		if (c->is_neg[i]) {
			/*
			 * If the negative term is greater than positive - then
			 * the darkness has taken over and we are all doomed! Eh,
			 * I mean, then we can just return 0 lx and go out
			 */
			if (terms[i] >= res)
				return 0;

			res -= terms[i];
		}

	meastime *= 10;
	do_div(res, meastime);

	return (int) res;
}

static bool bu27034_has_valid_sample(struct bu27034_data *data)
{
	int ret, val;

	ret = regmap_read(data->regmap, BU27034_REG_MODE_CONTROL4, &val);
	if (ret) {
		dev_err(data->dev, "Read failed %d\n", ret);

		return false;
	}

	return val & BU27034_MASK_VALID;
}

/*
 * Reading the register where VALID bit is clears this bit. (So does changing
 * any gain / integration time configuration registers) The bit gets
 * set when we have acquired new data. We use this bit to indicate data
 * validity.
 */
static void bu27034_invalidate_read_data(struct bu27034_data *data)
{
	bu27034_has_valid_sample(data);
}

static int bu27034_read_result(struct bu27034_data *data, int chan, int *res)
{
	int reg[] = {
		[BU27034_CHAN_DATA0] = BU27034_REG_DATA0_LO,
		[BU27034_CHAN_DATA1] = BU27034_REG_DATA1_LO,
		[BU27034_CHAN_DATA2] = BU27034_REG_DATA2_LO,
	};
	int valid, ret;
	__le16 val;

	ret = regmap_read_poll_timeout(data->regmap, BU27034_REG_MODE_CONTROL4,
				       valid, (valid & BU27034_MASK_VALID),
				       BU27034_DATA_WAIT_TIME_US, 0);
	if (ret)
		return ret;

	ret = regmap_bulk_read(data->regmap, reg[chan], &val, sizeof(val));
	if (ret)
		return ret;

	*res = le16_to_cpu(val);

	return 0;
}

static int bu27034_get_result_unlocked(struct bu27034_data *data, __le16 *res,
				       int size)
{
	int ret = 0, retry_cnt = 0;

retry:
	/* Get new value from sensor if data is ready */
	if (bu27034_has_valid_sample(data)) {
		ret = regmap_bulk_read(data->regmap, BU27034_REG_DATA0_LO,
				       res, size);
		if (ret)
			return ret;

		bu27034_invalidate_read_data(data);
	} else {
		/* No new data in sensor. Wait and retry */
		retry_cnt++;

		if (retry_cnt > BU27034_RETRY_LIMIT) {
			dev_err(data->dev, "No data from sensor\n");

			return -ETIMEDOUT;
		}

		msleep(25);

		goto retry;
	}

	return ret;
}

static int bu27034_meas_set(struct bu27034_data *data, bool en)
{
	if (en)
		return regmap_set_bits(data->regmap, BU27034_REG_MODE_CONTROL4,
				       BU27034_MASK_MEAS_EN);

	return regmap_clear_bits(data->regmap, BU27034_REG_MODE_CONTROL4,
				 BU27034_MASK_MEAS_EN);
}

static int bu27034_get_single_result(struct bu27034_data *data, int chan,
				     int *val)
{
	int ret;

	if (chan < BU27034_CHAN_DATA0 || chan > BU27034_CHAN_DATA2)
		return -EINVAL;

	ret = bu27034_meas_set(data, true);
	if (ret)
		return ret;

	ret = bu27034_get_int_time(data);
	if (ret < 0)
		return ret;

	msleep(ret / 1000);

	return bu27034_read_result(data, chan, val);
}

/*
 * The formula given by vendor for computing luxes out of data0 and data1
 * (in open air) is as follows:
 *
 * Let's mark:
 * D0 = data0/ch0_gain/meas_time_ms * 25600
 * D1 = data1/ch1_gain/meas_time_ms * 25600
 *
 * Then:
 * if (D1/D0 < 0.87)
 *	lx = (0.001331 * D0 + 0.0000354 * D1) * ((D1 / D0 - 0.87) * 3.45 + 1)
 * else if (D1/D0 < 1)
 *	lx = (0.001331 * D0 + 0.0000354 * D1) * ((D1 / D0 - 0.87) * 0.385 + 1)
 * else
 *	lx = (0.001331 * D0 + 0.0000354 * D1) * ((D1 / D0 - 2) * -0.05 + 1)
 *
 * We use it here. Users who have for example some colored lens
 * need to modify the calculation but I hope this gives a starting point for
 * those working with such devices.
 */

static int bu27034_calc_mlux(struct bu27034_data *data, __le16 *res, int *val)
{
	unsigned int gain0, gain1, meastime;
	unsigned int d1_d0_ratio_scaled;
	u16 ch0, ch1;
	u64 helper64;
	int ret;

	/*
	 * We return 0 lux if calculation fails. This should be reasonably
	 * easy to spot from the buffers especially if raw-data channels show
	 * valid values
	 */
	*val = 0;

	ch0 = max_t(u16, 1, le16_to_cpu(res[0]));
	ch1 = max_t(u16, 1, le16_to_cpu(res[1]));

	ret = bu27034_get_gain(data, BU27034_CHAN_DATA0, &gain0);
	if (ret)
		return ret;

	ret = bu27034_get_gain(data, BU27034_CHAN_DATA1, &gain1);
	if (ret)
		return ret;

	ret = bu27034_get_int_time(data);
	if (ret < 0)
		return ret;

	meastime = ret;

	d1_d0_ratio_scaled = (unsigned int)ch1 * (unsigned int)gain0 * 100;
	helper64 = (u64)ch1 * (u64)gain0 * 100LLU;

	if (helper64 != d1_d0_ratio_scaled) {
		unsigned int div = (unsigned int)ch0 * gain1;

		do_div(helper64, div);
		d1_d0_ratio_scaled = helper64;
	} else {
		d1_d0_ratio_scaled /= ch0 * gain1;
	}

	if (d1_d0_ratio_scaled < 87)
		ret = bu27034_fixp_calc_lx(ch0, ch1, gain0, gain1, meastime, 0);
	else if (d1_d0_ratio_scaled < 100)
		ret = bu27034_fixp_calc_lx(ch0, ch1, gain0, gain1, meastime, 1);
	else
		ret = bu27034_fixp_calc_lx(ch0, ch1, gain0, gain1, meastime, 2);

	if (ret < 0)
		return ret;

	*val = ret;

	return 0;

}

static int bu27034_get_mlux(struct bu27034_data *data, int chan, int *val)
{
	__le16 res[3];
	int ret;

	ret = bu27034_meas_set(data, true);
	if (ret)
		return ret;

	ret = bu27034_get_result_unlocked(data, &res[0], sizeof(res));
	if (ret)
		return ret;

	ret = bu27034_calc_mlux(data, res, val);
	if (ret)
		return ret;

	ret = bu27034_meas_set(data, false);
	if (ret)
		dev_err(data->dev, "failed to disable measurement\n");

	return 0;
}

static int bu27034_read_raw(struct iio_dev *idev,
			   struct iio_chan_spec const *chan,
			   int *val, int *val2, long mask)
{
	struct bu27034_data *data = iio_priv(idev);
	int ret;

	switch (mask) {
	case IIO_CHAN_INFO_INT_TIME:
		*val = 0;
		*val2 = bu27034_get_int_time(data);
		if (*val2 < 0)
			return *val2;

		return IIO_VAL_INT_PLUS_MICRO;

	case IIO_CHAN_INFO_SCALE:
		return bu27034_get_scale(data, chan->channel, val, val2);

	case IIO_CHAN_INFO_RAW:
	{
		int (*result_get)(struct bu27034_data *data, int chan, int *val);

		if (chan->type == IIO_INTENSITY)
			result_get = bu27034_get_single_result;
		else if (chan->type == IIO_LIGHT)
			result_get = bu27034_get_mlux;
		else
			return -EINVAL;

		/* Don't mess with measurement enabling while buffering */
		ret = iio_device_claim_direct_mode(idev);
		if (ret)
			return ret;

		mutex_lock(&data->mutex);
		/*
		 * Reading one channel at a time is inefficient but we
		 * don't care here. Buffered version should be used if
		 * performance is an issue.
		 */
		ret = result_get(data, chan->channel, val);

		mutex_unlock(&data->mutex);
		iio_device_release_direct_mode(idev);

		if (ret)
			return ret;

		return IIO_VAL_INT;
	}
	default:
		return -EINVAL;
	}
}

static int bu27034_write_raw_get_fmt(struct iio_dev *indio_dev,
				     struct iio_chan_spec const *chan,
				     long mask)
{

	switch (mask) {
	case IIO_CHAN_INFO_SCALE:
		return IIO_VAL_INT_PLUS_NANO;
	case IIO_CHAN_INFO_INT_TIME:
		return IIO_VAL_INT_PLUS_MICRO;
	default:
		return -EINVAL;
	}
}

static int bu27034_write_raw(struct iio_dev *idev,
			     struct iio_chan_spec const *chan,
			     int val, int val2, long mask)
{
	struct bu27034_data *data = iio_priv(idev);
	int ret;

	ret = iio_device_claim_direct_mode(idev);
	if (ret)
		return ret;

	switch (mask) {
	case IIO_CHAN_INFO_SCALE:
		ret = bu27034_set_scale(data, chan->channel, val, val2);
		break;
	case IIO_CHAN_INFO_INT_TIME:
		if (!val)
			ret = bu27034_try_set_int_time(data, val2);
		else
			ret = -EINVAL;
		break;
	default:
		ret = -EINVAL;
		break;
	}

	iio_device_release_direct_mode(idev);

	return ret;
}

static int bu27034_read_avail(struct iio_dev *idev,
			      struct iio_chan_spec const *chan, const int **vals,
			      int *type, int *length, long mask)
{
	struct bu27034_data *data = iio_priv(idev);

	switch (mask) {
	case IIO_CHAN_INFO_INT_TIME:
		return iio_gts_avail_times(&data->gts, vals, type, length);
	case IIO_CHAN_INFO_SCALE:
		return iio_gts_all_avail_scales(&data->gts, vals, type, length);
	default:
		return -EINVAL;
	}
}

static const struct iio_info bu27034_info = {
	.read_raw = &bu27034_read_raw,
	.write_raw = &bu27034_write_raw,
	.write_raw_get_fmt = &bu27034_write_raw_get_fmt,
	.read_avail = &bu27034_read_avail,
};

static int bu27034_chip_init(struct bu27034_data *data)
{
	int ret, sel;

	/* Reset */
	ret = regmap_write_bits(data->regmap, BU27034_REG_SYSTEM_CONTROL,
			   BU27034_MASK_SW_RESET, BU27034_MASK_SW_RESET);
	if (ret)
		return dev_err_probe(data->dev, ret, "Sensor reset failed\n");

	msleep(1);

	ret = regmap_reinit_cache(data->regmap, &bu27034_regmap);
	if (ret) {
		dev_err(data->dev, "Failed to reinit reg cache\n");
		return ret;
	}

	/*
	 * Read integration time here to ensure it is in regmap cache. We do
	 * this to speed-up the int-time acquisition in the start of the buffer
	 * handling thread where longer delays could make it more likely we end
	 * up skipping a sample, and where the longer delays make timestamps
	 * less accurate.
	 */
	ret = regmap_read(data->regmap, BU27034_REG_MODE_CONTROL1, &sel);
	if (ret)
		dev_err(data->dev, "reading integration time failed\n");

	return 0;
}

static int bu27034_wait_for_data(struct bu27034_data *data)
{
	int ret, val;

	ret = regmap_read_poll_timeout(data->regmap, BU27034_REG_MODE_CONTROL4,
				       val, val & BU27034_MASK_VALID,
				       BU27034_DATA_WAIT_TIME_US,
				       BU27034_TOTAL_DATA_WAIT_TIME_US);
	if (ret) {
		dev_err(data->dev, "data polling %s\n",
			!(val & BU27034_MASK_VALID) ? "timeout" : "fail");

		return ret;
	}

	ret = regmap_bulk_read(data->regmap, BU27034_REG_DATA0_LO,
			       &data->scan.channels[0],
			       sizeof(data->scan.channels));
	if (ret)
		return ret;

	bu27034_invalidate_read_data(data);

	return 0;
}

static int bu27034_buffer_thread(void *arg)
{
	struct iio_dev *idev = arg;
	struct bu27034_data *data;
	int wait_ms;

	data = iio_priv(idev);

	wait_ms = bu27034_get_int_time(data);
	wait_ms /= 1000;

	wait_ms -= BU27034_MEAS_WAIT_PREMATURE_MS;

	while (!kthread_should_stop()) {
		int ret;
		int64_t tstamp;

		msleep(wait_ms);
		ret = bu27034_wait_for_data(data);
		if (ret)
			continue;

		tstamp = iio_get_time_ns(idev);

		if (test_bit(BU27034_CHAN_ALS, idev->active_scan_mask)) {
			int mlux;

			ret = bu27034_calc_mlux(data, &data->scan.channels[0],
					       &mlux);
			if (ret)
				dev_err(data->dev, "failed to calculate lux\n");

			/*
			 * The maximum Milli lux value we get with gain 1x time
			 * 55mS data ch0 = 0xffff ch1 = 0xffff fits in 26 bits
			 * so there should be no problem returning int from
			 * computations and casting it to u32
			 */
			data->scan.mlux = (u32)mlux;
		}
		iio_push_to_buffers_with_timestamp(idev, &data->scan, tstamp);
	}

	return 0;
}

static int bu27034_buffer_enable(struct iio_dev *idev)
{
	struct bu27034_data *data = iio_priv(idev);
	struct task_struct *task;
	int ret;

	mutex_lock(&data->mutex);
	ret = bu27034_meas_set(data, true);
	if (ret)
		goto unlock_out;

	task = kthread_run(bu27034_buffer_thread, idev,
				 "bu27034-buffering-%u",
				 iio_device_id(idev));
	if (IS_ERR(task)) {
		ret = PTR_ERR(task);
		goto unlock_out;
	}

	data->task = task;

unlock_out:
	mutex_unlock(&data->mutex);

	return ret;
}

static int bu27034_buffer_disable(struct iio_dev *idev)
{
	struct bu27034_data *data = iio_priv(idev);
	int ret;

	mutex_lock(&data->mutex);
	if (data->task) {
		kthread_stop(data->task);
		data->task = NULL;
	}

	ret = bu27034_meas_set(data, false);
	mutex_unlock(&data->mutex);

	return ret;
}

static const struct iio_buffer_setup_ops bu27034_buffer_ops = {
	.postenable = &bu27034_buffer_enable,
	.predisable = &bu27034_buffer_disable,
};

static int bu27034_probe(struct i2c_client *i2c)
{
	struct device *dev = &i2c->dev;
	struct bu27034_data *data;
	struct regmap *regmap;
	struct iio_dev *idev;
	unsigned int part_id, reg;
	int ret;

	regmap = devm_regmap_init_i2c(i2c, &bu27034_regmap);
	if (IS_ERR(regmap))
		return dev_err_probe(dev, PTR_ERR(regmap),
				     "Failed to initialize Regmap\n");

	idev = devm_iio_device_alloc(dev, sizeof(*data));
	if (!idev)
		return -ENOMEM;

	ret = devm_regulator_get_enable(dev, "vdd");
	if (ret)
		return dev_err_probe(dev, ret, "Failed to get regulator\n");

	data = iio_priv(idev);

	ret = regmap_read(regmap, BU27034_REG_SYSTEM_CONTROL, &reg);
	if (ret)
		return dev_err_probe(dev, ret, "Failed to access sensor\n");

	part_id = FIELD_GET(BU27034_MASK_PART_ID, reg);

	if (part_id != BU27034_ID)
		dev_warn(dev, "unknown device 0x%x\n", part_id);

	ret = devm_iio_init_iio_gts(dev, BU27034_SCALE_1X, 0, bu27034_gains,
				    ARRAY_SIZE(bu27034_gains), bu27034_itimes,
				    ARRAY_SIZE(bu27034_itimes), &data->gts);
	if (ret)
		return ret;

	mutex_init(&data->mutex);
	data->regmap = regmap;
	data->dev = dev;

	idev->channels = bu27034_channels;
	idev->num_channels = ARRAY_SIZE(bu27034_channels);
	idev->name = "bu27034";
	idev->info = &bu27034_info;

	idev->modes = INDIO_DIRECT_MODE | INDIO_BUFFER_SOFTWARE;
	idev->available_scan_masks = bu27034_scan_masks;

	ret = bu27034_chip_init(data);
	if (ret)
		return ret;

	ret = devm_iio_kfifo_buffer_setup(dev, idev, &bu27034_buffer_ops);
	if (ret)
		return dev_err_probe(dev, ret, "buffer setup failed\n");

	ret = devm_iio_device_register(dev, idev);
	if (ret < 0)
		return dev_err_probe(dev, ret,
				     "Unable to register iio device\n");

	return ret;
}

static const struct of_device_id bu27034_of_match[] = {
	{ .compatible = "rohm,bu27034" },
	{ }
};
MODULE_DEVICE_TABLE(of, bu27034_of_match);

static struct i2c_driver bu27034_i2c_driver = {
	.driver = {
		.name = "bu27034-als",
		.of_match_table = bu27034_of_match,
		.probe_type = PROBE_PREFER_ASYNCHRONOUS,
	},
	.probe = bu27034_probe,
};
module_i2c_driver(bu27034_i2c_driver);

MODULE_LICENSE("GPL");
MODULE_AUTHOR("Matti Vaittinen <matti.vaittinen@fi.rohmeurope.com>");
MODULE_DESCRIPTION("ROHM BU27034 ambient light sensor driver");
MODULE_IMPORT_NS(IIO_GTS_HELPER);