summaryrefslogtreecommitdiff
path: root/drivers/rtc/rtc-m41t80.c
blob: cce5b52846586565fa5a756bf4d3225bfc45e848 (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
// SPDX-License-Identifier: GPL-2.0-only
/*
 * I2C client/driver for the ST M41T80 family of i2c rtc chips.
 *
 * Author: Alexander Bigga <ab@mycable.de>
 *
 * Based on m41t00.c by Mark A. Greer <mgreer@mvista.com>
 *
 * 2006 (c) mycable GmbH
 */

#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt

#include <linux/bcd.h>
#include <linux/clk-provider.h>
#include <linux/i2c.h>
#include <linux/init.h>
#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/of_device.h>
#include <linux/rtc.h>
#include <linux/slab.h>
#include <linux/mutex.h>
#include <linux/string.h>
#ifdef CONFIG_RTC_DRV_M41T80_WDT
#include <linux/fs.h>
#include <linux/ioctl.h>
#include <linux/miscdevice.h>
#include <linux/reboot.h>
#include <linux/watchdog.h>
#endif

#define M41T80_REG_SSEC		0x00
#define M41T80_REG_SEC		0x01
#define M41T80_REG_MIN		0x02
#define M41T80_REG_HOUR		0x03
#define M41T80_REG_WDAY		0x04
#define M41T80_REG_DAY		0x05
#define M41T80_REG_MON		0x06
#define M41T80_REG_YEAR		0x07
#define M41T80_REG_ALARM_MON	0x0a
#define M41T80_REG_ALARM_DAY	0x0b
#define M41T80_REG_ALARM_HOUR	0x0c
#define M41T80_REG_ALARM_MIN	0x0d
#define M41T80_REG_ALARM_SEC	0x0e
#define M41T80_REG_FLAGS	0x0f
#define M41T80_REG_SQW		0x13

#define M41T80_DATETIME_REG_SIZE	(M41T80_REG_YEAR + 1)
#define M41T80_ALARM_REG_SIZE	\
	(M41T80_REG_ALARM_SEC + 1 - M41T80_REG_ALARM_MON)

#define M41T80_SQW_MAX_FREQ	32768

#define M41T80_SEC_ST		BIT(7)	/* ST: Stop Bit */
#define M41T80_ALMON_AFE	BIT(7)	/* AFE: AF Enable Bit */
#define M41T80_ALMON_SQWE	BIT(6)	/* SQWE: SQW Enable Bit */
#define M41T80_ALHOUR_HT	BIT(6)	/* HT: Halt Update Bit */
#define M41T80_FLAGS_OF		BIT(2)	/* OF: Oscillator Failure Bit */
#define M41T80_FLAGS_AF		BIT(6)	/* AF: Alarm Flag Bit */
#define M41T80_FLAGS_BATT_LOW	BIT(4)	/* BL: Battery Low Bit */
#define M41T80_WATCHDOG_RB2	BIT(7)	/* RB: Watchdog resolution */
#define M41T80_WATCHDOG_RB1	BIT(1)	/* RB: Watchdog resolution */
#define M41T80_WATCHDOG_RB0	BIT(0)	/* RB: Watchdog resolution */

#define M41T80_FEATURE_HT	BIT(0)	/* Halt feature */
#define M41T80_FEATURE_BL	BIT(1)	/* Battery low indicator */
#define M41T80_FEATURE_SQ	BIT(2)	/* Squarewave feature */
#define M41T80_FEATURE_WD	BIT(3)	/* Extra watchdog resolution */
#define M41T80_FEATURE_SQ_ALT	BIT(4)	/* RSx bits are in reg 4 */

static const struct i2c_device_id m41t80_id[] = {
	{ "m41t62", M41T80_FEATURE_SQ | M41T80_FEATURE_SQ_ALT },
	{ "m41t65", M41T80_FEATURE_HT | M41T80_FEATURE_WD },
	{ "m41t80", M41T80_FEATURE_SQ },
	{ "m41t81", M41T80_FEATURE_HT | M41T80_FEATURE_SQ},
	{ "m41t81s", M41T80_FEATURE_HT | M41T80_FEATURE_BL | M41T80_FEATURE_SQ },
	{ "m41t82", M41T80_FEATURE_HT | M41T80_FEATURE_BL | M41T80_FEATURE_SQ },
	{ "m41t83", M41T80_FEATURE_HT | M41T80_FEATURE_BL | M41T80_FEATURE_SQ },
	{ "m41st84", M41T80_FEATURE_HT | M41T80_FEATURE_BL | M41T80_FEATURE_SQ },
	{ "m41st85", M41T80_FEATURE_HT | M41T80_FEATURE_BL | M41T80_FEATURE_SQ },
	{ "m41st87", M41T80_FEATURE_HT | M41T80_FEATURE_BL | M41T80_FEATURE_SQ },
	{ "rv4162", M41T80_FEATURE_SQ | M41T80_FEATURE_WD | M41T80_FEATURE_SQ_ALT },
	{ }
};
MODULE_DEVICE_TABLE(i2c, m41t80_id);

static const __maybe_unused struct of_device_id m41t80_of_match[] = {
	{
		.compatible = "st,m41t62",
		.data = (void *)(M41T80_FEATURE_SQ | M41T80_FEATURE_SQ_ALT)
	},
	{
		.compatible = "st,m41t65",
		.data = (void *)(M41T80_FEATURE_HT | M41T80_FEATURE_WD)
	},
	{
		.compatible = "st,m41t80",
		.data = (void *)(M41T80_FEATURE_SQ)
	},
	{
		.compatible = "st,m41t81",
		.data = (void *)(M41T80_FEATURE_HT | M41T80_FEATURE_SQ)
	},
	{
		.compatible = "st,m41t81s",
		.data = (void *)(M41T80_FEATURE_HT | M41T80_FEATURE_BL | M41T80_FEATURE_SQ)
	},
	{
		.compatible = "st,m41t82",
		.data = (void *)(M41T80_FEATURE_HT | M41T80_FEATURE_BL | M41T80_FEATURE_SQ)
	},
	{
		.compatible = "st,m41t83",
		.data = (void *)(M41T80_FEATURE_HT | M41T80_FEATURE_BL | M41T80_FEATURE_SQ)
	},
	{
		.compatible = "st,m41t84",
		.data = (void *)(M41T80_FEATURE_HT | M41T80_FEATURE_BL | M41T80_FEATURE_SQ)
	},
	{
		.compatible = "st,m41t85",
		.data = (void *)(M41T80_FEATURE_HT | M41T80_FEATURE_BL | M41T80_FEATURE_SQ)
	},
	{
		.compatible = "st,m41t87",
		.data = (void *)(M41T80_FEATURE_HT | M41T80_FEATURE_BL | M41T80_FEATURE_SQ)
	},
	{
		.compatible = "microcrystal,rv4162",
		.data = (void *)(M41T80_FEATURE_SQ | M41T80_FEATURE_WD | M41T80_FEATURE_SQ_ALT)
	},
	/* DT compatibility only, do not use compatibles below: */
	{
		.compatible = "st,rv4162",
		.data = (void *)(M41T80_FEATURE_SQ | M41T80_FEATURE_WD | M41T80_FEATURE_SQ_ALT)
	},
	{
		.compatible = "rv4162",
		.data = (void *)(M41T80_FEATURE_SQ | M41T80_FEATURE_WD | M41T80_FEATURE_SQ_ALT)
	},
	{ }
};
MODULE_DEVICE_TABLE(of, m41t80_of_match);

struct m41t80_data {
	unsigned long features;
	struct i2c_client *client;
	struct rtc_device *rtc;
#ifdef CONFIG_COMMON_CLK
	struct clk_hw sqw;
	unsigned long freq;
	unsigned int sqwe;
#endif
};

static irqreturn_t m41t80_handle_irq(int irq, void *dev_id)
{
	struct i2c_client *client = dev_id;
	struct m41t80_data *m41t80 = i2c_get_clientdata(client);
	unsigned long events = 0;
	int flags, flags_afe;

	rtc_lock(m41t80->rtc);

	flags_afe = i2c_smbus_read_byte_data(client, M41T80_REG_ALARM_MON);
	if (flags_afe < 0) {
		rtc_unlock(m41t80->rtc);
		return IRQ_NONE;
	}

	flags = i2c_smbus_read_byte_data(client, M41T80_REG_FLAGS);
	if (flags <= 0) {
		rtc_unlock(m41t80->rtc);
		return IRQ_NONE;
	}

	if (flags & M41T80_FLAGS_AF) {
		flags &= ~M41T80_FLAGS_AF;
		flags_afe &= ~M41T80_ALMON_AFE;
		events |= RTC_AF;
	}

	if (events) {
		rtc_update_irq(m41t80->rtc, 1, events);
		i2c_smbus_write_byte_data(client, M41T80_REG_FLAGS, flags);
		i2c_smbus_write_byte_data(client, M41T80_REG_ALARM_MON,
					  flags_afe);
	}

	rtc_unlock(m41t80->rtc);

	return IRQ_HANDLED;
}

static int m41t80_rtc_read_time(struct device *dev, struct rtc_time *tm)
{
	struct i2c_client *client = to_i2c_client(dev);
	unsigned char buf[8];
	int err, flags;

	flags = i2c_smbus_read_byte_data(client, M41T80_REG_FLAGS);
	if (flags < 0)
		return flags;

	if (flags & M41T80_FLAGS_OF) {
		dev_err(&client->dev, "Oscillator failure, data is invalid.\n");
		return -EINVAL;
	}

	err = i2c_smbus_read_i2c_block_data(client, M41T80_REG_SSEC,
					    sizeof(buf), buf);
	if (err < 0) {
		dev_err(&client->dev, "Unable to read date\n");
		return err;
	}

	tm->tm_sec = bcd2bin(buf[M41T80_REG_SEC] & 0x7f);
	tm->tm_min = bcd2bin(buf[M41T80_REG_MIN] & 0x7f);
	tm->tm_hour = bcd2bin(buf[M41T80_REG_HOUR] & 0x3f);
	tm->tm_mday = bcd2bin(buf[M41T80_REG_DAY] & 0x3f);
	tm->tm_wday = buf[M41T80_REG_WDAY] & 0x07;
	tm->tm_mon = bcd2bin(buf[M41T80_REG_MON] & 0x1f) - 1;

	/* assume 20YY not 19YY, and ignore the Century Bit */
	tm->tm_year = bcd2bin(buf[M41T80_REG_YEAR]) + 100;
	return 0;
}

static int m41t80_rtc_set_time(struct device *dev, struct rtc_time *tm)
{
	struct i2c_client *client = to_i2c_client(dev);
	struct m41t80_data *clientdata = i2c_get_clientdata(client);
	unsigned char buf[8];
	int err, flags;

	buf[M41T80_REG_SSEC] = 0;
	buf[M41T80_REG_SEC] = bin2bcd(tm->tm_sec);
	buf[M41T80_REG_MIN] = bin2bcd(tm->tm_min);
	buf[M41T80_REG_HOUR] = bin2bcd(tm->tm_hour);
	buf[M41T80_REG_DAY] = bin2bcd(tm->tm_mday);
	buf[M41T80_REG_MON] = bin2bcd(tm->tm_mon + 1);
	buf[M41T80_REG_YEAR] = bin2bcd(tm->tm_year - 100);
	buf[M41T80_REG_WDAY] = tm->tm_wday;

	/* If the square wave output is controlled in the weekday register */
	if (clientdata->features & M41T80_FEATURE_SQ_ALT) {
		int val;

		val = i2c_smbus_read_byte_data(client, M41T80_REG_WDAY);
		if (val < 0)
			return val;

		buf[M41T80_REG_WDAY] |= (val & 0xf0);
	}

	err = i2c_smbus_write_i2c_block_data(client, M41T80_REG_SSEC,
					     sizeof(buf), buf);
	if (err < 0) {
		dev_err(&client->dev, "Unable to write to date registers\n");
		return err;
	}

	/* Clear the OF bit of Flags Register */
	flags = i2c_smbus_read_byte_data(client, M41T80_REG_FLAGS);
	if (flags < 0)
		return flags;

	err = i2c_smbus_write_byte_data(client, M41T80_REG_FLAGS,
					flags & ~M41T80_FLAGS_OF);
	if (err < 0) {
		dev_err(&client->dev, "Unable to write flags register\n");
		return err;
	}

	return err;
}

static int m41t80_rtc_proc(struct device *dev, struct seq_file *seq)
{
	struct i2c_client *client = to_i2c_client(dev);
	struct m41t80_data *clientdata = i2c_get_clientdata(client);
	int reg;

	if (clientdata->features & M41T80_FEATURE_BL) {
		reg = i2c_smbus_read_byte_data(client, M41T80_REG_FLAGS);
		if (reg < 0)
			return reg;
		seq_printf(seq, "battery\t\t: %s\n",
			   (reg & M41T80_FLAGS_BATT_LOW) ? "exhausted" : "ok");
	}
	return 0;
}

static int m41t80_alarm_irq_enable(struct device *dev, unsigned int enabled)
{
	struct i2c_client *client = to_i2c_client(dev);
	int flags, retval;

	flags = i2c_smbus_read_byte_data(client, M41T80_REG_ALARM_MON);
	if (flags < 0)
		return flags;

	if (enabled)
		flags |= M41T80_ALMON_AFE;
	else
		flags &= ~M41T80_ALMON_AFE;

	retval = i2c_smbus_write_byte_data(client, M41T80_REG_ALARM_MON, flags);
	if (retval < 0) {
		dev_err(dev, "Unable to enable alarm IRQ %d\n", retval);
		return retval;
	}
	return 0;
}

static int m41t80_set_alarm(struct device *dev, struct rtc_wkalrm *alrm)
{
	struct i2c_client *client = to_i2c_client(dev);
	u8 alarmvals[5];
	int ret, err;

	alarmvals[0] = bin2bcd(alrm->time.tm_mon + 1);
	alarmvals[1] = bin2bcd(alrm->time.tm_mday);
	alarmvals[2] = bin2bcd(alrm->time.tm_hour);
	alarmvals[3] = bin2bcd(alrm->time.tm_min);
	alarmvals[4] = bin2bcd(alrm->time.tm_sec);

	/* Clear AF and AFE flags */
	ret = i2c_smbus_read_byte_data(client, M41T80_REG_ALARM_MON);
	if (ret < 0)
		return ret;
	err = i2c_smbus_write_byte_data(client, M41T80_REG_ALARM_MON,
					ret & ~(M41T80_ALMON_AFE));
	if (err < 0) {
		dev_err(dev, "Unable to clear AFE bit\n");
		return err;
	}

	/* Keep SQWE bit value */
	alarmvals[0] |= (ret & M41T80_ALMON_SQWE);

	ret = i2c_smbus_read_byte_data(client, M41T80_REG_FLAGS);
	if (ret < 0)
		return ret;

	err = i2c_smbus_write_byte_data(client, M41T80_REG_FLAGS,
					ret & ~(M41T80_FLAGS_AF));
	if (err < 0) {
		dev_err(dev, "Unable to clear AF bit\n");
		return err;
	}

	/* Write the alarm */
	err = i2c_smbus_write_i2c_block_data(client, M41T80_REG_ALARM_MON,
					     5, alarmvals);
	if (err)
		return err;

	/* Enable the alarm interrupt */
	if (alrm->enabled) {
		alarmvals[0] |= M41T80_ALMON_AFE;
		err = i2c_smbus_write_byte_data(client, M41T80_REG_ALARM_MON,
						alarmvals[0]);
		if (err)
			return err;
	}

	return 0;
}

static int m41t80_read_alarm(struct device *dev, struct rtc_wkalrm *alrm)
{
	struct i2c_client *client = to_i2c_client(dev);
	u8 alarmvals[5];
	int flags, ret;

	ret = i2c_smbus_read_i2c_block_data(client, M41T80_REG_ALARM_MON,
					    5, alarmvals);
	if (ret != 5)
		return ret < 0 ? ret : -EIO;

	flags = i2c_smbus_read_byte_data(client, M41T80_REG_FLAGS);
	if (flags < 0)
		return flags;

	alrm->time.tm_sec  = bcd2bin(alarmvals[4] & 0x7f);
	alrm->time.tm_min  = bcd2bin(alarmvals[3] & 0x7f);
	alrm->time.tm_hour = bcd2bin(alarmvals[2] & 0x3f);
	alrm->time.tm_mday = bcd2bin(alarmvals[1] & 0x3f);
	alrm->time.tm_mon  = bcd2bin(alarmvals[0] & 0x3f) - 1;

	alrm->enabled = !!(alarmvals[0] & M41T80_ALMON_AFE);
	alrm->pending = (flags & M41T80_FLAGS_AF) && alrm->enabled;

	return 0;
}

static const struct rtc_class_ops m41t80_rtc_ops = {
	.read_time = m41t80_rtc_read_time,
	.set_time = m41t80_rtc_set_time,
	.proc = m41t80_rtc_proc,
	.read_alarm = m41t80_read_alarm,
	.set_alarm = m41t80_set_alarm,
	.alarm_irq_enable = m41t80_alarm_irq_enable,
};

#ifdef CONFIG_PM_SLEEP
static int m41t80_suspend(struct device *dev)
{
	struct i2c_client *client = to_i2c_client(dev);

	if (client->irq >= 0 && device_may_wakeup(dev))
		enable_irq_wake(client->irq);

	return 0;
}

static int m41t80_resume(struct device *dev)
{
	struct i2c_client *client = to_i2c_client(dev);

	if (client->irq >= 0 && device_may_wakeup(dev))
		disable_irq_wake(client->irq);

	return 0;
}
#endif

static SIMPLE_DEV_PM_OPS(m41t80_pm, m41t80_suspend, m41t80_resume);

#ifdef CONFIG_COMMON_CLK
#define sqw_to_m41t80_data(_hw) container_of(_hw, struct m41t80_data, sqw)

static unsigned long m41t80_decode_freq(int setting)
{
	return (setting == 0) ? 0 : (setting == 1) ? M41T80_SQW_MAX_FREQ :
		M41T80_SQW_MAX_FREQ >> setting;
}

static unsigned long m41t80_get_freq(struct m41t80_data *m41t80)
{
	struct i2c_client *client = m41t80->client;
	int reg_sqw = (m41t80->features & M41T80_FEATURE_SQ_ALT) ?
		M41T80_REG_WDAY : M41T80_REG_SQW;
	int ret = i2c_smbus_read_byte_data(client, reg_sqw);

	if (ret < 0)
		return 0;
	return m41t80_decode_freq(ret >> 4);
}

static unsigned long m41t80_sqw_recalc_rate(struct clk_hw *hw,
					    unsigned long parent_rate)
{
	return sqw_to_m41t80_data(hw)->freq;
}

static long m41t80_sqw_round_rate(struct clk_hw *hw, unsigned long rate,
				  unsigned long *prate)
{
	if (rate >= M41T80_SQW_MAX_FREQ)
		return M41T80_SQW_MAX_FREQ;
	if (rate >= M41T80_SQW_MAX_FREQ / 4)
		return M41T80_SQW_MAX_FREQ / 4;
	if (!rate)
		return 0;
	return 1 << ilog2(rate);
}

static int m41t80_sqw_set_rate(struct clk_hw *hw, unsigned long rate,
			       unsigned long parent_rate)
{
	struct m41t80_data *m41t80 = sqw_to_m41t80_data(hw);
	struct i2c_client *client = m41t80->client;
	int reg_sqw = (m41t80->features & M41T80_FEATURE_SQ_ALT) ?
		M41T80_REG_WDAY : M41T80_REG_SQW;
	int reg, ret, val = 0;

	if (rate >= M41T80_SQW_MAX_FREQ)
		val = 1;
	else if (rate >= M41T80_SQW_MAX_FREQ / 4)
		val = 2;
	else if (rate)
		val = 15 - ilog2(rate);

	reg = i2c_smbus_read_byte_data(client, reg_sqw);
	if (reg < 0)
		return reg;

	reg = (reg & 0x0f) | (val << 4);

	ret = i2c_smbus_write_byte_data(client, reg_sqw, reg);
	if (!ret)
		m41t80->freq = m41t80_decode_freq(val);
	return ret;
}

static int m41t80_sqw_control(struct clk_hw *hw, bool enable)
{
	struct m41t80_data *m41t80 = sqw_to_m41t80_data(hw);
	struct i2c_client *client = m41t80->client;
	int ret = i2c_smbus_read_byte_data(client, M41T80_REG_ALARM_MON);

	if (ret < 0)
		return ret;

	if (enable)
		ret |= M41T80_ALMON_SQWE;
	else
		ret &= ~M41T80_ALMON_SQWE;

	ret = i2c_smbus_write_byte_data(client, M41T80_REG_ALARM_MON, ret);
	if (!ret)
		m41t80->sqwe = enable;
	return ret;
}

static int m41t80_sqw_prepare(struct clk_hw *hw)
{
	return m41t80_sqw_control(hw, 1);
}

static void m41t80_sqw_unprepare(struct clk_hw *hw)
{
	m41t80_sqw_control(hw, 0);
}

static int m41t80_sqw_is_prepared(struct clk_hw *hw)
{
	return sqw_to_m41t80_data(hw)->sqwe;
}

static const struct clk_ops m41t80_sqw_ops = {
	.prepare = m41t80_sqw_prepare,
	.unprepare = m41t80_sqw_unprepare,
	.is_prepared = m41t80_sqw_is_prepared,
	.recalc_rate = m41t80_sqw_recalc_rate,
	.round_rate = m41t80_sqw_round_rate,
	.set_rate = m41t80_sqw_set_rate,
};

static struct clk *m41t80_sqw_register_clk(struct m41t80_data *m41t80)
{
	struct i2c_client *client = m41t80->client;
	struct device_node *node = client->dev.of_node;
	struct clk *clk;
	struct clk_init_data init;
	int ret;

	/* First disable the clock */
	ret = i2c_smbus_read_byte_data(client, M41T80_REG_ALARM_MON);
	if (ret < 0)
		return ERR_PTR(ret);
	ret = i2c_smbus_write_byte_data(client, M41T80_REG_ALARM_MON,
					ret & ~(M41T80_ALMON_SQWE));
	if (ret < 0)
		return ERR_PTR(ret);

	init.name = "m41t80-sqw";
	init.ops = &m41t80_sqw_ops;
	init.flags = 0;
	init.parent_names = NULL;
	init.num_parents = 0;
	m41t80->sqw.init = &init;
	m41t80->freq = m41t80_get_freq(m41t80);

	/* optional override of the clockname */
	of_property_read_string(node, "clock-output-names", &init.name);

	/* register the clock */
	clk = clk_register(&client->dev, &m41t80->sqw);
	if (!IS_ERR(clk))
		of_clk_add_provider(node, of_clk_src_simple_get, clk);

	return clk;
}
#endif

#ifdef CONFIG_RTC_DRV_M41T80_WDT
/*
 *****************************************************************************
 *
 * Watchdog Driver
 *
 *****************************************************************************
 */
static DEFINE_MUTEX(m41t80_rtc_mutex);
static struct i2c_client *save_client;

/* Default margin */
#define WD_TIMO 60		/* 1..31 seconds */

static int wdt_margin = WD_TIMO;
module_param(wdt_margin, int, 0);
MODULE_PARM_DESC(wdt_margin, "Watchdog timeout in seconds (default 60s)");

static unsigned long wdt_is_open;
static int boot_flag;

/**
 *	wdt_ping:
 *
 *	Reload counter one with the watchdog timeout. We don't bother reloading
 *	the cascade counter.
 */
static void wdt_ping(void)
{
	unsigned char i2c_data[2];
	struct i2c_msg msgs1[1] = {
		{
			.addr	= save_client->addr,
			.flags	= 0,
			.len	= 2,
			.buf	= i2c_data,
		},
	};
	struct m41t80_data *clientdata = i2c_get_clientdata(save_client);

	i2c_data[0] = 0x09;		/* watchdog register */

	if (wdt_margin > 31)
		i2c_data[1] = (wdt_margin & 0xFC) | 0x83; /* resolution = 4s */
	else
		/*
		 * WDS = 1 (0x80), mulitplier = WD_TIMO, resolution = 1s (0x02)
		 */
		i2c_data[1] = wdt_margin << 2 | 0x82;

	/*
	 * M41T65 has three bits for watchdog resolution.  Don't set bit 7, as
	 * that would be an invalid resolution.
	 */
	if (clientdata->features & M41T80_FEATURE_WD)
		i2c_data[1] &= ~M41T80_WATCHDOG_RB2;

	i2c_transfer(save_client->adapter, msgs1, 1);
}

/**
 *	wdt_disable:
 *
 *	disables watchdog.
 */
static void wdt_disable(void)
{
	unsigned char i2c_data[2], i2c_buf[0x10];
	struct i2c_msg msgs0[2] = {
		{
			.addr	= save_client->addr,
			.flags	= 0,
			.len	= 1,
			.buf	= i2c_data,
		},
		{
			.addr	= save_client->addr,
			.flags	= I2C_M_RD,
			.len	= 1,
			.buf	= i2c_buf,
		},
	};
	struct i2c_msg msgs1[1] = {
		{
			.addr	= save_client->addr,
			.flags	= 0,
			.len	= 2,
			.buf	= i2c_data,
		},
	};

	i2c_data[0] = 0x09;
	i2c_transfer(save_client->adapter, msgs0, 2);

	i2c_data[0] = 0x09;
	i2c_data[1] = 0x00;
	i2c_transfer(save_client->adapter, msgs1, 1);
}

/**
 *	wdt_write:
 *	@file: file handle to the watchdog
 *	@buf: buffer to write (unused as data does not matter here
 *	@count: count of bytes
 *	@ppos: pointer to the position to write. No seeks allowed
 *
 *	A write to a watchdog device is defined as a keepalive signal. Any
 *	write of data will do, as we we don't define content meaning.
 */
static ssize_t wdt_write(struct file *file, const char __user *buf,
			 size_t count, loff_t *ppos)
{
	if (count) {
		wdt_ping();
		return 1;
	}
	return 0;
}

static ssize_t wdt_read(struct file *file, char __user *buf,
			size_t count, loff_t *ppos)
{
	return 0;
}

/**
 *	wdt_ioctl:
 *	@file: file handle to the device
 *	@cmd: watchdog command
 *	@arg: argument pointer
 *
 *	The watchdog API defines a common set of functions for all watchdogs
 *	according to their available features. We only actually usefully support
 *	querying capabilities and current status.
 */
static int wdt_ioctl(struct file *file, unsigned int cmd,
		     unsigned long arg)
{
	int new_margin, rv;
	static struct watchdog_info ident = {
		.options = WDIOF_POWERUNDER | WDIOF_KEEPALIVEPING |
			WDIOF_SETTIMEOUT,
		.firmware_version = 1,
		.identity = "M41T80 WTD"
	};

	switch (cmd) {
	case WDIOC_GETSUPPORT:
		return copy_to_user((struct watchdog_info __user *)arg, &ident,
				    sizeof(ident)) ? -EFAULT : 0;

	case WDIOC_GETSTATUS:
	case WDIOC_GETBOOTSTATUS:
		return put_user(boot_flag, (int __user *)arg);
	case WDIOC_KEEPALIVE:
		wdt_ping();
		return 0;
	case WDIOC_SETTIMEOUT:
		if (get_user(new_margin, (int __user *)arg))
			return -EFAULT;
		/* Arbitrary, can't find the card's limits */
		if (new_margin < 1 || new_margin > 124)
			return -EINVAL;
		wdt_margin = new_margin;
		wdt_ping();
		fallthrough;
	case WDIOC_GETTIMEOUT:
		return put_user(wdt_margin, (int __user *)arg);

	case WDIOC_SETOPTIONS:
		if (copy_from_user(&rv, (int __user *)arg, sizeof(int)))
			return -EFAULT;

		if (rv & WDIOS_DISABLECARD) {
			pr_info("disable watchdog\n");
			wdt_disable();
		}

		if (rv & WDIOS_ENABLECARD) {
			pr_info("enable watchdog\n");
			wdt_ping();
		}

		return -EINVAL;
	}
	return -ENOTTY;
}

static long wdt_unlocked_ioctl(struct file *file, unsigned int cmd,
			       unsigned long arg)
{
	int ret;

	mutex_lock(&m41t80_rtc_mutex);
	ret = wdt_ioctl(file, cmd, arg);
	mutex_unlock(&m41t80_rtc_mutex);

	return ret;
}

/**
 *	wdt_open:
 *	@inode: inode of device
 *	@file: file handle to device
 *
 */
static int wdt_open(struct inode *inode, struct file *file)
{
	if (MINOR(inode->i_rdev) == WATCHDOG_MINOR) {
		mutex_lock(&m41t80_rtc_mutex);
		if (test_and_set_bit(0, &wdt_is_open)) {
			mutex_unlock(&m41t80_rtc_mutex);
			return -EBUSY;
		}
		/*
		 *	Activate
		 */
		wdt_is_open = 1;
		mutex_unlock(&m41t80_rtc_mutex);
		return stream_open(inode, file);
	}
	return -ENODEV;
}

/**
 *	wdt_close:
 *	@inode: inode to board
 *	@file: file handle to board
 *
 */
static int wdt_release(struct inode *inode, struct file *file)
{
	if (MINOR(inode->i_rdev) == WATCHDOG_MINOR)
		clear_bit(0, &wdt_is_open);
	return 0;
}

/**
 *	notify_sys:
 *	@this: our notifier block
 *	@code: the event being reported
 *	@unused: unused
 *
 *	Our notifier is called on system shutdowns. We want to turn the card
 *	off at reboot otherwise the machine will reboot again during memory
 *	test or worse yet during the following fsck. This would suck, in fact
 *	trust me - if it happens it does suck.
 */
static int wdt_notify_sys(struct notifier_block *this, unsigned long code,
			  void *unused)
{
	if (code == SYS_DOWN || code == SYS_HALT)
		/* Disable Watchdog */
		wdt_disable();
	return NOTIFY_DONE;
}

static const struct file_operations wdt_fops = {
	.owner	= THIS_MODULE,
	.read	= wdt_read,
	.unlocked_ioctl = wdt_unlocked_ioctl,
	.compat_ioctl = compat_ptr_ioctl,
	.write	= wdt_write,
	.open	= wdt_open,
	.release = wdt_release,
	.llseek = no_llseek,
};

static struct miscdevice wdt_dev = {
	.minor = WATCHDOG_MINOR,
	.name = "watchdog",
	.fops = &wdt_fops,
};

/*
 *	The WDT card needs to learn about soft shutdowns in order to
 *	turn the timebomb registers off.
 */
static struct notifier_block wdt_notifier = {
	.notifier_call = wdt_notify_sys,
};
#endif /* CONFIG_RTC_DRV_M41T80_WDT */

/*
 *****************************************************************************
 *
 *	Driver Interface
 *
 *****************************************************************************
 */

static int m41t80_probe(struct i2c_client *client,
			const struct i2c_device_id *id)
{
	struct i2c_adapter *adapter = client->adapter;
	int rc = 0;
	struct rtc_time tm;
	struct m41t80_data *m41t80_data = NULL;
	bool wakeup_source = false;

	if (!i2c_check_functionality(client->adapter, I2C_FUNC_SMBUS_I2C_BLOCK |
				     I2C_FUNC_SMBUS_BYTE_DATA)) {
		dev_err(&adapter->dev, "doesn't support I2C_FUNC_SMBUS_BYTE_DATA | I2C_FUNC_SMBUS_I2C_BLOCK\n");
		return -ENODEV;
	}

	m41t80_data = devm_kzalloc(&client->dev, sizeof(*m41t80_data),
				   GFP_KERNEL);
	if (!m41t80_data)
		return -ENOMEM;

	m41t80_data->client = client;
	if (client->dev.of_node)
		m41t80_data->features = (unsigned long)
			of_device_get_match_data(&client->dev);
	else
		m41t80_data->features = id->driver_data;
	i2c_set_clientdata(client, m41t80_data);

	m41t80_data->rtc =  devm_rtc_allocate_device(&client->dev);
	if (IS_ERR(m41t80_data->rtc))
		return PTR_ERR(m41t80_data->rtc);

#ifdef CONFIG_OF
	wakeup_source = of_property_read_bool(client->dev.of_node,
					      "wakeup-source");
#endif
	if (client->irq > 0) {
		rc = devm_request_threaded_irq(&client->dev, client->irq,
					       NULL, m41t80_handle_irq,
					       IRQF_TRIGGER_LOW | IRQF_ONESHOT,
					       "m41t80", client);
		if (rc) {
			dev_warn(&client->dev, "unable to request IRQ, alarms disabled\n");
			client->irq = 0;
			wakeup_source = false;
		}
	}
	if (client->irq > 0 || wakeup_source)
		device_init_wakeup(&client->dev, true);
	else
		clear_bit(RTC_FEATURE_ALARM, m41t80_data->rtc->features);

	m41t80_data->rtc->ops = &m41t80_rtc_ops;
	m41t80_data->rtc->range_min = RTC_TIMESTAMP_BEGIN_2000;
	m41t80_data->rtc->range_max = RTC_TIMESTAMP_END_2099;

	if (client->irq <= 0) {
		/* We cannot support UIE mode if we do not have an IRQ line */
		m41t80_data->rtc->uie_unsupported = 1;
	}

	/* Make sure HT (Halt Update) bit is cleared */
	rc = i2c_smbus_read_byte_data(client, M41T80_REG_ALARM_HOUR);

	if (rc >= 0 && rc & M41T80_ALHOUR_HT) {
		if (m41t80_data->features & M41T80_FEATURE_HT) {
			m41t80_rtc_read_time(&client->dev, &tm);
			dev_info(&client->dev, "HT bit was set!\n");
			dev_info(&client->dev, "Power Down at %ptR\n", &tm);
		}
		rc = i2c_smbus_write_byte_data(client, M41T80_REG_ALARM_HOUR,
					       rc & ~M41T80_ALHOUR_HT);
	}

	if (rc < 0) {
		dev_err(&client->dev, "Can't clear HT bit\n");
		return rc;
	}

	/* Make sure ST (stop) bit is cleared */
	rc = i2c_smbus_read_byte_data(client, M41T80_REG_SEC);

	if (rc >= 0 && rc & M41T80_SEC_ST)
		rc = i2c_smbus_write_byte_data(client, M41T80_REG_SEC,
					       rc & ~M41T80_SEC_ST);
	if (rc < 0) {
		dev_err(&client->dev, "Can't clear ST bit\n");
		return rc;
	}

#ifdef CONFIG_RTC_DRV_M41T80_WDT
	if (m41t80_data->features & M41T80_FEATURE_HT) {
		save_client = client;
		rc = misc_register(&wdt_dev);
		if (rc)
			return rc;
		rc = register_reboot_notifier(&wdt_notifier);
		if (rc) {
			misc_deregister(&wdt_dev);
			return rc;
		}
	}
#endif
#ifdef CONFIG_COMMON_CLK
	if (m41t80_data->features & M41T80_FEATURE_SQ)
		m41t80_sqw_register_clk(m41t80_data);
#endif

	rc = devm_rtc_register_device(m41t80_data->rtc);
	if (rc)
		return rc;

	return 0;
}

static int m41t80_remove(struct i2c_client *client)
{
#ifdef CONFIG_RTC_DRV_M41T80_WDT
	struct m41t80_data *clientdata = i2c_get_clientdata(client);

	if (clientdata->features & M41T80_FEATURE_HT) {
		misc_deregister(&wdt_dev);
		unregister_reboot_notifier(&wdt_notifier);
	}
#endif

	return 0;
}

static struct i2c_driver m41t80_driver = {
	.driver = {
		.name = "rtc-m41t80",
		.of_match_table = of_match_ptr(m41t80_of_match),
		.pm = &m41t80_pm,
	},
	.probe = m41t80_probe,
	.remove = m41t80_remove,
	.id_table = m41t80_id,
};

module_i2c_driver(m41t80_driver);

MODULE_AUTHOR("Alexander Bigga <ab@mycable.de>");
MODULE_DESCRIPTION("ST Microelectronics M41T80 series RTC I2C Client Driver");
MODULE_LICENSE("GPL");