aboutsummaryrefslogtreecommitdiffstats
path: root/drivers/rtc/interface.c
blob: 636a2ec218109e90791894301daea464299f4241 (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
/*
 * RTC subsystem, interface functions
 *
 * Copyright (C) 2005 Tower Technologies
 * Author: Alessandro Zummo <a.zummo@towertech.it>
 *
 * based on arch/arm/common/rtctime.c
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License version 2 as
 * published by the Free Software Foundation.
*/

#include <linux/rtc.h>
#include <linux/sched.h>
#include <linux/log2.h>
#include <linux/workqueue.h>

static int rtc_timer_enqueue(struct rtc_device *rtc, struct rtc_timer *timer);
static void rtc_timer_remove(struct rtc_device *rtc, struct rtc_timer *timer);

static int __rtc_read_time(struct rtc_device *rtc, struct rtc_time *tm)
{
	int err;
	if (!rtc->ops)
		err = -ENODEV;
	else if (!rtc->ops->read_time)
		err = -EINVAL;
	else {
		memset(tm, 0, sizeof(struct rtc_time));
		err = rtc->ops->read_time(rtc->dev.parent, tm);
	}
	return err;
}

int rtc_read_time(struct rtc_device *rtc, struct rtc_time *tm)
{
	int err;

	err = mutex_lock_interruptible(&rtc->ops_lock);
	if (err)
		return err;

	err = __rtc_read_time(rtc, tm);
	mutex_unlock(&rtc->ops_lock);
	return err;
}
EXPORT_SYMBOL_GPL(rtc_read_time);

int rtc_set_time(struct rtc_device *rtc, struct rtc_time *tm)
{
	int err;

	err = rtc_valid_tm(tm);
	if (err != 0)
		return err;

	err = mutex_lock_interruptible(&rtc->ops_lock);
	if (err)
		return err;

	if (!rtc->ops)
		err = -ENODEV;
	else if (rtc->ops->set_time)
		err = rtc->ops->set_time(rtc->dev.parent, tm);
	else if (rtc->ops->set_mmss) {
		unsigned long secs;
		err = rtc_tm_to_time(tm, &secs);
		if (err == 0)
			err = rtc->ops->set_mmss(rtc->dev.parent, secs);
	} else
		err = -EINVAL;

	mutex_unlock(&rtc->ops_lock);
	return err;
}
EXPORT_SYMBOL_GPL(rtc_set_time);

int rtc_set_mmss(struct rtc_device *rtc, unsigned long secs)
{
	int err;

	err = mutex_lock_interruptible(&rtc->ops_lock);
	if (err)
		return err;

	if (!rtc->ops)
		err = -ENODEV;
	else if (rtc->ops->set_mmss)
		err = rtc->ops->set_mmss(rtc->dev.parent, secs);
	else if (rtc->ops->read_time && rtc->ops->set_time) {
		struct rtc_time new, old;

		err = rtc->ops->read_time(rtc->dev.parent, &old);
		if (err == 0) {
			rtc_time_to_tm(secs, &new);

			/*
			 * avoid writing when we're going to change the day of
			 * the month. We will retry in the next minute. This
			 * basically means that if the RTC must not drift
			 * by more than 1 minute in 11 minutes.
			 */
			if (!((old.tm_hour == 23 && old.tm_min == 59) ||
				(new.tm_hour == 23 && new.tm_min == 59)))
				err = rtc->ops->set_time(rtc->dev.parent,
						&new);
		}
	}
	else
		err = -EINVAL;

	mutex_unlock(&rtc->ops_lock);

	return err;
}
EXPORT_SYMBOL_GPL(rtc_set_mmss);

static int rtc_read_alarm_internal(struct rtc_device *rtc, struct rtc_wkalrm *alarm)
{
	int err;

	err = mutex_lock_interruptible(&rtc->ops_lock);
	if (err)
		return err;

	if (rtc->ops == NULL)
		err = -ENODEV;
	else if (!rtc->ops->read_alarm)
		err = -EINVAL;
	else {
		memset(alarm, 0, sizeof(struct rtc_wkalrm));
		err = rtc->ops->read_alarm(rtc->dev.parent, alarm);
	}

	mutex_unlock(&rtc->ops_lock);
	return err;
}

int __rtc_read_alarm(struct rtc_device *rtc, struct rtc_wkalrm *alarm)
{
	int err;
	struct rtc_time before, now;
	int first_time = 1;
	unsigned long t_now, t_alm;
	enum { none, day, month, year } missing = none;
	unsigned days;

	/* The lower level RTC driver may return -1 in some fields,
	 * creating invalid alarm->time values, for reasons like:
	 *
	 *   - The hardware may not be capable of filling them in;
	 *     many alarms match only on time-of-day fields, not
	 *     day/month/year calendar data.
	 *
	 *   - Some hardware uses illegal values as "wildcard" match
	 *     values, which non-Linux firmware (like a BIOS) may try
	 *     to set up as e.g. "alarm 15 minutes after each hour".
	 *     Linux uses only oneshot alarms.
	 *
	 * When we see that here, we deal with it by using values from
	 * a current RTC timestamp for any missing (-1) values.  The
	 * RTC driver prevents "periodic alarm" modes.
	 *
	 * But this can be racey, because some fields of the RTC timestamp
	 * may have wrapped in the interval since we read the RTC alarm,
	 * which would lead to us inserting inconsistent values in place
	 * of the -1 fields.
	 *
	 * Reading the alarm and timestamp in the reverse sequence
	 * would have the same race condition, and not solve the issue.
	 *
	 * So, we must first read the RTC timestamp,
	 * then read the RTC alarm value,
	 * and then read a second RTC timestamp.
	 *
	 * If any fields of the second timestamp have changed
	 * when compared with the first timestamp, then we know
	 * our timestamp may be inconsistent with that used by
	 * the low-level rtc_read_alarm_internal() function.
	 *
	 * So, when the two timestamps disagree, we just loop and do
	 * the process again to get a fully consistent set of values.
	 *
	 * This could all instead be done in the lower level driver,
	 * but since more than one lower level RTC implementation needs it,
	 * then it's probably best best to do it here instead of there..
	 */

	/* Get the "before" timestamp */
	err = rtc_read_time(rtc, &before);
	if (err < 0)
		return err;
	do {
		if (!first_time)
			memcpy(&before, &now, sizeof(struct rtc_time));
		first_time = 0;

		/* get the RTC alarm values, which may be incomplete */
		err = rtc_read_alarm_internal(rtc, alarm);
		if (err)
			return err;

		/* full-function RTCs won't have such missing fields */
		if (rtc_valid_tm(&alarm->time) == 0)
			return 0;

		/* get the "after" timestamp, to detect wrapped fields */
		err = rtc_read_time(rtc, &now);
		if (err < 0)
			return err;

		/* note that tm_sec is a "don't care" value here: */
	} while (   before.tm_min   != now.tm_min
		 || before.tm_hour  != now.tm_hour
		 || before.tm_mon   != now.tm_mon
		 || before.tm_year  != now.tm_year);

	/* Fill in the missing alarm fields using the timestamp; we
	 * know there's at least one since alarm->time is invalid.
	 */
	if (alarm->time.tm_sec == -1)
		alarm->time.tm_sec = now.tm_sec;
	if (alarm->time.tm_min == -1)
		alarm->time.tm_min = now.tm_min;
	if (alarm->time.tm_hour == -1)
		alarm->time.tm_hour = now.tm_hour;

	/* For simplicity, only support date rollover for now */
	if (alarm->time.tm_mday < 1 || alarm->time.tm_mday > 31) {
		alarm->time.tm_mday = now.tm_mday;
		missing = day;
	}
	if ((unsigned)alarm->time.tm_mon >= 12) {
		alarm->time.tm_mon = now.tm_mon;
		if (missing == none)
			missing = month;
	}
	if (alarm->time.tm_year == -1) {
		alarm->time.tm_year = now.tm_year;
		if (missing == none)
			missing = year;
	}

	/* with luck, no rollover is needed */
	rtc_tm_to_time(&now, &t_now);
	rtc_tm_to_time(&alarm->time, &t_alm);
	if (t_now < t_alm)
		goto done;

	switch (missing) {

	/* 24 hour rollover ... if it's now 10am Monday, an alarm that
	 * that will trigger at 5am will do so at 5am Tuesday, which
	 * could also be in the next month or year.  This is a common
	 * case, especially for PCs.
	 */
	case day:
		dev_dbg(&rtc->dev, "alarm rollover: %s\n", "day");
		t_alm += 24 * 60 * 60;
		rtc_time_to_tm(t_alm, &alarm->time);
		break;

	/* Month rollover ... if it's the 31th, an alarm on the 3rd will
	 * be next month.  An alarm matching on the 30th, 29th, or 28th
	 * may end up in the month after that!  Many newer PCs support
	 * this type of alarm.
	 */
	case month:
		dev_dbg(&rtc->dev, "alarm rollover: %s\n", "month");
		do {
			if (alarm->time.tm_mon < 11)
				alarm->time.tm_mon++;
			else {
				alarm->time.tm_mon = 0;
				alarm->time.tm_year++;
			}
			days = rtc_month_days(alarm->time.tm_mon,
					alarm->time.tm_year);
		} while (days < alarm->time.tm_mday);
		break;

	/* Year rollover ... easy except for leap years! */
	case year:
		dev_dbg(&rtc->dev, "alarm rollover: %s\n", "year");
		do {
			alarm->time.tm_year++;
		} while (rtc_valid_tm(&alarm->time) != 0);
		break;

	default:
		dev_warn(&rtc->dev, "alarm rollover not handled\n");
	}

done:
	return 0;
}

int rtc_read_alarm(struct rtc_device *rtc, struct rtc_wkalrm *alarm)
{
	int err;

	err = mutex_lock_interruptible(&rtc->ops_lock);
	if (err)
		return err;
	if (rtc->ops == NULL)
		err = -ENODEV;
	else if (!rtc->ops->read_alarm)
		err = -EINVAL;
	else {
		memset(alarm, 0, sizeof(struct rtc_wkalrm));
		alarm->enabled = rtc->aie_timer.enabled;
		alarm->time = rtc_ktime_to_tm(rtc->aie_timer.node.expires);
	}
	mutex_unlock(&rtc->ops_lock);

	return err;
}
EXPORT_SYMBOL_GPL(rtc_read_alarm);

static int __rtc_set_alarm(struct rtc_device *rtc, struct rtc_wkalrm *alarm)
{
	struct rtc_time tm;
	long now, scheduled;
	int err;

	err = rtc_valid_tm(&alarm->time);
	if (err)
		return err;
	rtc_tm_to_time(&alarm->time, &scheduled);

	/* Make sure we're not setting alarms in the past */
	err = __rtc_read_time(rtc, &tm);
	rtc_tm_to_time(&tm, &now);
	if (scheduled <= now)
		return -ETIME;
	/*
	 * XXX - We just checked to make sure the alarm time is not
	 * in the past, but there is still a race window where if
	 * the is alarm set for the next second and the second ticks
	 * over right here, before we set the alarm.
	 */

	if (!rtc->ops)
		err = -ENODEV;
	else if (!rtc->ops->set_alarm)
		err = -EINVAL;
	else
		err = rtc->ops->set_alarm(rtc->dev.parent, alarm);

	return err;
}

int rtc_set_alarm(struct rtc_device *rtc, struct rtc_wkalrm *alarm)
{
	int err;

	err = rtc_valid_tm(&alarm->time);
	if (err != 0)
		return err;

	err = mutex_lock_interruptible(&rtc->ops_lock);
	if (err)
		return err;
	if (rtc->aie_timer.enabled) {
		rtc_timer_remove(rtc, &rtc->aie_timer);
	}
	rtc->aie_timer.node.expires = rtc_tm_to_ktime(alarm->time);
	rtc->aie_timer.period = ktime_set(0, 0);
	if (alarm->enabled) {
		err = rtc_timer_enqueue(rtc, &rtc->aie_timer);
	}
	mutex_unlock(&rtc->ops_lock);
	return err;
}
EXPORT_SYMBOL_GPL(rtc_set_alarm);

/* Called once per device from rtc_device_register */
int rtc_initialize_alarm(struct rtc_device *rtc, struct rtc_wkalrm *alarm)
{
	int err;

	err = rtc_valid_tm(&alarm->time);
	if (err != 0)
		return err;

	err = mutex_lock_interruptible(&rtc->ops_lock);
	if (err)
		return err;

	rtc->aie_timer.node.expires = rtc_tm_to_ktime(alarm->time);
	rtc->aie_timer.period = ktime_set(0, 0);
	if (alarm->enabled) {
		rtc->aie_timer.enabled = 1;
		timerqueue_add(&rtc->timerqueue, &rtc->aie_timer.node);
	}
	mutex_unlock(&rtc->ops_lock);
	return err;
}
EXPORT_SYMBOL_GPL(rtc_initialize_alarm);



int rtc_alarm_irq_enable(struct rtc_device *rtc, unsigned int enabled)
{
	int err = mutex_lock_interruptible(&rtc->ops_lock);
	if (err)
		return err;

	if (rtc->aie_timer.enabled != enabled) {
		if (enabled)
			err = rtc_timer_enqueue(rtc, &rtc->aie_timer);
		else
			rtc_timer_remove(rtc, &rtc->aie_timer);
	}

	if (err)
		/* nothing */;
	else if (!rtc->ops)
		err = -ENODEV;
	else if (!rtc->ops->alarm_irq_enable)
		err = -EINVAL;
	else
		err = rtc->ops->alarm_irq_enable(rtc->dev.parent, enabled);

	mutex_unlock(&rtc->ops_lock);
	return err;
}
EXPORT_SYMBOL_GPL(rtc_alarm_irq_enable);

int rtc_update_irq_enable(struct rtc_device *rtc, unsigned int enabled)
{
	int err = mutex_lock_interruptible(&rtc->ops_lock);
	if (err)
		return err;

#ifdef CONFIG_RTC_INTF_DEV_UIE_EMUL
	if (enabled == 0 && rtc->uie_irq_active) {
		mutex_unlock(&rtc->ops_lock);
		return rtc_dev_update_irq_enable_emul(rtc, 0);
	}
#endif
	/* make sure we're changing state */
	if (rtc->uie_rtctimer.enabled == enabled)
		goto out;

	if (enabled) {
		struct rtc_time tm;
		ktime_t now, onesec;

		__rtc_read_time(rtc, &tm);
		onesec = ktime_set(1, 0);
		now = rtc_tm_to_ktime(tm);
		rtc->uie_rtctimer.node.expires = ktime_add(now, onesec);
		rtc->uie_rtctimer.period = ktime_set(1, 0);
		err = rtc_timer_enqueue(rtc, &rtc->uie_rtctimer);
	} else
		rtc_timer_remove(rtc, &rtc->uie_rtctimer);

out:
	mutex_unlock(&rtc->ops_lock);
#ifdef CONFIG_RTC_INTF_DEV_UIE_EMUL
	/*
	 * Enable emulation if the driver did not provide
	 * the update_irq_enable function pointer or if returned
	 * -EINVAL to signal that it has been configured without
	 * interrupts or that are not available at the moment.
	 */
	if (err == -EINVAL)
		err = rtc_dev_update_irq_enable_emul(rtc, enabled);
#endif
	return err;

}
EXPORT_SYMBOL_GPL(rtc_update_irq_enable);


/**
 * rtc_handle_legacy_irq - AIE, UIE and PIE event hook
 * @rtc: pointer to the rtc device
 *
 * This function is called when an AIE, UIE or PIE mode interrupt
 * has occurred (or been emulated).
 *
 * Triggers the registered irq_task function callback.
 */
void rtc_handle_legacy_irq(struct rtc_device *rtc, int num, int mode)
{
	unsigned long flags;

	/* mark one irq of the appropriate mode */
	spin_lock_irqsave(&rtc->irq_lock, flags);
	rtc->irq_data = (rtc->irq_data + (num << 8)) | (RTC_IRQF|mode);
	spin_unlock_irqrestore(&rtc->irq_lock, flags);

	/* call the task func */
	spin_lock_irqsave(&rtc->irq_task_lock, flags);
	if (rtc->irq_task)
		rtc->irq_task->func(rtc->irq_task->private_data);
	spin_unlock_irqrestore(&rtc->irq_task_lock, flags);

	wake_up_interruptible(&rtc->irq_queue);
	kill_fasync(&rtc->async_queue, SIGIO, POLL_IN);
}


/**
 * rtc_aie_update_irq - AIE mode rtctimer hook
 * @private: pointer to the rtc_device
 *
 * This functions is called when the aie_timer expires.
 */
void rtc_aie_update_irq(void *private)
{
	struct rtc_device *rtc = (struct rtc_device *)private;
	rtc_handle_legacy_irq(rtc, 1, RTC_AF);
}


/**
 * rtc_uie_update_irq - UIE mode rtctimer hook
 * @private: pointer to the rtc_device
 *
 * This functions is called when the uie_timer expires.
 */
void rtc_uie_update_irq(void *private)
{
	struct rtc_device *rtc = (struct rtc_device *)private;
	rtc_handle_legacy_irq(rtc, 1,  RTC_UF);
}


/**
 * rtc_pie_update_irq - PIE mode hrtimer hook
 * @timer: pointer to the pie mode hrtimer
 *
 * This function is used to emulate PIE mode interrupts
 * using an hrtimer. This function is called when the periodic
 * hrtimer expires.
 */
enum hrtimer_restart rtc_pie_update_irq(struct hrtimer *timer)
{
	struct rtc_device *rtc;
	ktime_t period;
	int count;
	rtc = container_of(timer, struct rtc_device, pie_timer);

	period = ktime_set(0, NSEC_PER_SEC/rtc->irq_freq);
	count = hrtimer_forward_now(timer, period);

	rtc_handle_legacy_irq(rtc, count, RTC_PF);

	return HRTIMER_RESTART;
}

/**
 * rtc_update_irq - Triggered when a RTC interrupt occurs.
 * @rtc: the rtc device
 * @num: how many irqs are being reported (usually one)
 * @events: mask of RTC_IRQF with one or more of RTC_PF, RTC_AF, RTC_UF
 * Context: any
 */
void rtc_update_irq(struct rtc_device *rtc,
		unsigned long num, unsigned long events)
{
	schedule_work(&rtc->irqwork);
}
EXPORT_SYMBOL_GPL(rtc_update_irq);

static int __rtc_match(struct device *dev, void *data)
{
	char *name = (char *)data;

	if (strcmp(dev_name(dev), name) == 0)
		return 1;
	return 0;
}

struct rtc_device *rtc_class_open(char *name)
{
	struct device *dev;
	struct rtc_device *rtc = NULL;

	dev = class_find_device(rtc_class, NULL, name, __rtc_match);
	if (dev)
		rtc = to_rtc_device(dev);

	if (rtc) {
		if (!try_module_get(rtc->owner)) {
			put_device(dev);
			rtc = NULL;
		}
	}

	return rtc;
}
EXPORT_SYMBOL_GPL(rtc_class_open);

void rtc_class_close(struct rtc_device *rtc)
{
	module_put(rtc->owner);
	put_device(&rtc->dev);
}
EXPORT_SYMBOL_GPL(rtc_class_close);

int rtc_irq_register(struct rtc_device *rtc, struct rtc_task *task)
{
	int retval = -EBUSY;

	if (task == NULL || task->func == NULL)
		return -EINVAL;

	/* Cannot register while the char dev is in use */
	if (test_and_set_bit_lock(RTC_DEV_BUSY, &rtc->flags))
		return -EBUSY;

	spin_lock_irq(&rtc->irq_task_lock);
	if (rtc->irq_task == NULL) {
		rtc->irq_task = task;
		retval = 0;
	}
	spin_unlock_irq(&rtc->irq_task_lock);

	clear_bit_unlock(RTC_DEV_BUSY, &rtc->flags);

	return retval;
}
EXPORT_SYMBOL_GPL(rtc_irq_register);

void rtc_irq_unregister(struct rtc_device *rtc, struct rtc_task *task)
{
	spin_lock_irq(&rtc->irq_task_lock);
	if (rtc->irq_task == task)
		rtc->irq_task = NULL;
	spin_unlock_irq(&rtc->irq_task_lock);
}
EXPORT_SYMBOL_GPL(rtc_irq_unregister);

static int rtc_update_hrtimer(struct rtc_device *rtc, int enabled)
{
	/*
	 * We unconditionally cancel the timer here, because otherwise
	 * we could run into BUG_ON(timer->state != HRTIMER_STATE_CALLBACK);
	 * when we manage to start the timer before the callback
	 * returns HRTIMER_RESTART.
	 *
	 * We cannot use hrtimer_cancel() here as a running callback
	 * could be blocked on rtc->irq_task_lock and hrtimer_cancel()
	 * would spin forever.
	 */
	if (hrtimer_try_to_cancel(&rtc->pie_timer) < 0)
		return -1;

	if (enabled) {
		ktime_t period = ktime_set(0, NSEC_PER_SEC / rtc->irq_freq);

		hrtimer_start(&rtc->pie_timer, period, HRTIMER_MODE_REL);
	}
	return 0;
}

/**
 * rtc_irq_set_state - enable/disable 2^N Hz periodic IRQs
 * @rtc: the rtc device
 * @task: currently registered with rtc_irq_register()
 * @enabled: true to enable periodic IRQs
 * Context: any
 *
 * Note that rtc_irq_set_freq() should previously have been used to
 * specify the desired frequency of periodic IRQ task->func() callbacks.
 */
int rtc_irq_set_state(struct rtc_device *rtc, struct rtc_task *task, int enabled)
{
	int err = 0;
	unsigned long flags;

retry:
	spin_lock_irqsave(&rtc->irq_task_lock, flags);
	if (rtc->irq_task != NULL && task == NULL)
		err = -EBUSY;
	if (rtc->irq_task != task)
		err = -EACCES;
	if (!err) {
		if (rtc_update_hrtimer(rtc, enabled) < 0) {
			spin_unlock_irqrestore(&rtc->irq_task_lock, flags);
			cpu_relax();
			goto retry;
		}
		rtc->pie_enabled = enabled;
	}
	spin_unlock_irqrestore(&rtc->irq_task_lock, flags);
	return err;
}
EXPORT_SYMBOL_GPL(rtc_irq_set_state);

/**
 * rtc_irq_set_freq - set 2^N Hz periodic IRQ frequency for IRQ
 * @rtc: the rtc device
 * @task: currently registered with rtc_irq_register()
 * @freq: positive frequency with which task->func() will be called
 * Context: any
 *
 * Note that rtc_irq_set_state() is used to enable or disable the
 * periodic IRQs.
 */
int rtc_irq_set_freq(struct rtc_device *rtc, struct rtc_task *task, int freq)
{
	int err = 0;
	unsigned long flags;

	if (freq <= 0 || freq > RTC_MAX_FREQ)
		return -EINVAL;
retry:
	spin_lock_irqsave(&rtc->irq_task_lock, flags);
	if (rtc->irq_task != NULL && task == NULL)
		err = -EBUSY;
	if (rtc->irq_task != task)
		err = -EACCES;
	if (!err) {
		rtc->irq_freq = freq;
		if (rtc->pie_enabled && rtc_update_hrtimer(rtc, 1) < 0) {
			spin_unlock_irqrestore(&rtc->irq_task_lock, flags);
			cpu_relax();
			goto retry;
		}
	}
	spin_unlock_irqrestore(&rtc->irq_task_lock, flags);
	return err;
}
EXPORT_SYMBOL_GPL(rtc_irq_set_freq);

/**
 * rtc_timer_enqueue - Adds a rtc_timer to the rtc_device timerqueue
 * @rtc rtc device
 * @timer timer being added.
 *
 * Enqueues a timer onto the rtc devices timerqueue and sets
 * the next alarm event appropriately.
 *
 * Sets the enabled bit on the added timer.
 *
 * Must hold ops_lock for proper serialization of timerqueue
 */
static int rtc_timer_enqueue(struct rtc_device *rtc, struct rtc_timer *timer)
{
	timer->enabled = 1;
	timerqueue_add(&rtc->timerqueue, &timer->node);
	if (&timer->node == timerqueue_getnext(&rtc->timerqueue)) {
		struct rtc_wkalrm alarm;
		int err;
		alarm.time = rtc_ktime_to_tm(timer->node.expires);
		alarm.enabled = 1;
		err = __rtc_set_alarm(rtc, &alarm);
		if (err == -ETIME)
			schedule_work(&rtc->irqwork);
		else if (err) {
			timerqueue_del(&rtc->timerqueue, &timer->node);
			timer->enabled = 0;
			return err;
		}
	}
	return 0;
}

static void rtc_alarm_disable(struct rtc_device *rtc)
{
	if (!rtc->ops || !rtc->ops->alarm_irq_enable)
		return;

	rtc->ops->alarm_irq_enable(rtc->dev.parent, false);
}

/**
 * rtc_timer_remove - Removes a rtc_timer from the rtc_device timerqueue
 * @rtc rtc device
 * @timer timer being removed.
 *
 * Removes a timer onto the rtc devices timerqueue and sets
 * the next alarm event appropriately.
 *
 * Clears the enabled bit on the removed timer.
 *
 * Must hold ops_lock for proper serialization of timerqueue
 */
static void rtc_timer_remove(struct rtc_device *rtc, struct rtc_timer *timer)
{
	struct timerqueue_node *next = timerqueue_getnext(&rtc->timerqueue);
	timerqueue_del(&rtc->timerqueue, &timer->node);
	timer->enabled = 0;
	if (next == &timer->node) {
		struct rtc_wkalrm alarm;
		int err;
		next = timerqueue_getnext(&rtc->timerqueue);
		if (!next) {
			rtc_alarm_disable(rtc);
			return;
		}
		alarm.time = rtc_ktime_to_tm(next->expires);
		alarm.enabled = 1;
		err = __rtc_set_alarm(rtc, &alarm);
		if (err == -ETIME)
			schedule_work(&rtc->irqwork);
	}
}

/**
 * rtc_timer_do_work - Expires rtc timers
 * @rtc rtc device
 * @timer timer being removed.
 *
 * Expires rtc timers. Reprograms next alarm event if needed.
 * Called via worktask.
 *
 * Serializes access to timerqueue via ops_lock mutex
 */
void rtc_timer_do_work(struct work_struct *work)
{
	struct rtc_timer *timer;
	struct timerqueue_node *next;
	ktime_t now;
	struct rtc_time tm;

	struct rtc_device *rtc =
		container_of(work, struct rtc_device, irqwork);

	mutex_lock(&rtc->ops_lock);
again:
	__rtc_read_time(rtc, &tm);
	now = rtc_tm_to_ktime(tm);
	while ((next = timerqueue_getnext(&rtc->timerqueue))) {
		if (next->expires.tv64 > now.tv64)
			break;

		/* expire timer */
		timer = container_of(next, struct rtc_timer, node);
		timerqueue_del(&rtc->timerqueue, &timer->node);
		timer->enabled = 0;
		if (timer->task.func)
			timer->task.func(timer->task.private_data);

		/* Re-add/fwd periodic timers */
		if (ktime_to_ns(timer->period)) {
			timer->node.expires = ktime_add(timer->node.expires,
							timer->period);
			timer->enabled = 1;
			timerqueue_add(&rtc->timerqueue, &timer->node);
		}
	}

	/* Set next alarm */
	if (next) {
		struct rtc_wkalrm alarm;
		int err;
		alarm.time = rtc_ktime_to_tm(next->expires);
		alarm.enabled = 1;
		err = __rtc_set_alarm(rtc, &alarm);
		if (err == -ETIME)
			goto again;
	} else
		rtc_alarm_disable(rtc);

	mutex_unlock(&rtc->ops_lock);
}


/* rtc_timer_init - Initializes an rtc_timer
 * @timer: timer to be intiialized
 * @f: function pointer to be called when timer fires
 * @data: private data passed to function pointer
 *
 * Kernel interface to initializing an rtc_timer.
 */
void rtc_timer_init(struct rtc_timer *timer, void (*f)(void* p), void* data)
{
	timerqueue_init(&timer->node);
	timer->enabled = 0;
	timer->task.func = f;
	timer->task.private_data = data;
}

/* rtc_timer_start - Sets an rtc_timer to fire in the future
 * @ rtc: rtc device to be used
 * @ timer: timer being set
 * @ expires: time at which to expire the timer
 * @ period: period that the timer will recur
 *
 * Kernel interface to set an rtc_timer
 */
int rtc_timer_start(struct rtc_device *rtc, struct rtc_timer* timer,
			ktime_t expires, ktime_t period)
{
	int ret = 0;
	mutex_lock(&rtc->ops_lock);
	if (timer->enabled)
		rtc_timer_remove(rtc, timer);

	timer->node.expires = expires;
	timer->period = period;

	ret = rtc_timer_enqueue(rtc, timer);

	mutex_unlock(&rtc->ops_lock);
	return ret;
}

/* rtc_timer_cancel - Stops an rtc_timer
 * @ rtc: rtc device to be used
 * @ timer: timer being set
 *
 * Kernel interface to cancel an rtc_timer
 */
int rtc_timer_cancel(struct rtc_device *rtc, struct rtc_timer* timer)
{
	int ret = 0;
	mutex_lock(&rtc->ops_lock);
	if (timer->enabled)
		rtc_timer_remove(rtc, timer);
	mutex_unlock(&rtc->ops_lock);
	return ret;
}