aboutsummaryrefslogtreecommitdiff
path: root/kernel/time/alarmtimer.c
blob: 7fbba635a5499805c316c36e99910f1d96eb6fb6 (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
/*
 * Alarmtimer interface
 *
 * This interface provides a timer which is similarto hrtimers,
 * but triggers a RTC alarm if the box is suspend.
 *
 * This interface is influenced by the Android RTC Alarm timer
 * interface.
 *
 * Copyright (C) 2010 IBM Corperation
 *
 * Author: John Stultz <john.stultz@linaro.org>
 *
 * 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/time.h>
#include <linux/hrtimer.h>
#include <linux/timerqueue.h>
#include <linux/rtc.h>
#include <linux/alarmtimer.h>
#include <linux/mutex.h>
#include <linux/platform_device.h>
#include <linux/posix-timers.h>
#include <linux/workqueue.h>
#include <linux/freezer.h>

/**
 * struct alarm_base - Alarm timer bases
 * @lock:		Lock for syncrhonized access to the base
 * @timerqueue:		Timerqueue head managing the list of events
 * @timer: 		hrtimer used to schedule events while running
 * @gettime:		Function to read the time correlating to the base
 * @base_clockid:	clockid for the base
 */
static struct alarm_base {
	spinlock_t		lock;
	struct timerqueue_head	timerqueue;
	ktime_t			(*gettime)(void);
	clockid_t		base_clockid;
} alarm_bases[ALARM_NUMTYPE];

/* freezer delta & lock used to handle clock_nanosleep triggered wakeups */
static ktime_t freezer_delta;
static DEFINE_SPINLOCK(freezer_delta_lock);

static struct wakeup_source *ws;

#ifdef CONFIG_RTC_CLASS
/* rtc timer and device for setting alarm wakeups at suspend */
static struct rtc_timer		rtctimer;
static struct rtc_device	*rtcdev;
static DEFINE_SPINLOCK(rtcdev_lock);

/**
 * alarmtimer_get_rtcdev - Return selected rtcdevice
 *
 * This function returns the rtc device to use for wakealarms.
 * If one has not already been chosen, it checks to see if a
 * functional rtc device is available.
 */
struct rtc_device *alarmtimer_get_rtcdev(void)
{
	unsigned long flags;
	struct rtc_device *ret;

	spin_lock_irqsave(&rtcdev_lock, flags);
	ret = rtcdev;
	spin_unlock_irqrestore(&rtcdev_lock, flags);

	return ret;
}
EXPORT_SYMBOL_GPL(alarmtimer_get_rtcdev);

static int alarmtimer_rtc_add_device(struct device *dev,
				struct class_interface *class_intf)
{
	unsigned long flags;
	struct rtc_device *rtc = to_rtc_device(dev);

	if (rtcdev)
		return -EBUSY;

	if (!rtc->ops->set_alarm)
		return -1;
	if (!device_may_wakeup(rtc->dev.parent))
		return -1;

	spin_lock_irqsave(&rtcdev_lock, flags);
	if (!rtcdev) {
		rtcdev = rtc;
		/* hold a reference so it doesn't go away */
		get_device(dev);
	}
	spin_unlock_irqrestore(&rtcdev_lock, flags);
	return 0;
}

static inline void alarmtimer_rtc_timer_init(void)
{
	rtc_timer_init(&rtctimer, NULL, NULL);
}

static struct class_interface alarmtimer_rtc_interface = {
	.add_dev = &alarmtimer_rtc_add_device,
};

static int alarmtimer_rtc_interface_setup(void)
{
	alarmtimer_rtc_interface.class = rtc_class;
	return class_interface_register(&alarmtimer_rtc_interface);
}
static void alarmtimer_rtc_interface_remove(void)
{
	class_interface_unregister(&alarmtimer_rtc_interface);
}
#else
struct rtc_device *alarmtimer_get_rtcdev(void)
{
	return NULL;
}
#define rtcdev (NULL)
static inline int alarmtimer_rtc_interface_setup(void) { return 0; }
static inline void alarmtimer_rtc_interface_remove(void) { }
static inline void alarmtimer_rtc_timer_init(void) { }
#endif

/**
 * alarmtimer_enqueue - Adds an alarm timer to an alarm_base timerqueue
 * @base: pointer to the base where the timer is being run
 * @alarm: pointer to alarm being enqueued.
 *
 * Adds alarm to a alarm_base timerqueue
 *
 * Must hold base->lock when calling.
 */
static void alarmtimer_enqueue(struct alarm_base *base, struct alarm *alarm)
{
	if (alarm->state & ALARMTIMER_STATE_ENQUEUED)
		timerqueue_del(&base->timerqueue, &alarm->node);

	timerqueue_add(&base->timerqueue, &alarm->node);
	alarm->state |= ALARMTIMER_STATE_ENQUEUED;
}

/**
 * alarmtimer_dequeue - Removes an alarm timer from an alarm_base timerqueue
 * @base: pointer to the base where the timer is running
 * @alarm: pointer to alarm being removed
 *
 * Removes alarm to a alarm_base timerqueue
 *
 * Must hold base->lock when calling.
 */
static void alarmtimer_dequeue(struct alarm_base *base, struct alarm *alarm)
{
	if (!(alarm->state & ALARMTIMER_STATE_ENQUEUED))
		return;

	timerqueue_del(&base->timerqueue, &alarm->node);
	alarm->state &= ~ALARMTIMER_STATE_ENQUEUED;
}


/**
 * alarmtimer_fired - Handles alarm hrtimer being fired.
 * @timer: pointer to hrtimer being run
 *
 * When a alarm timer fires, this runs through the timerqueue to
 * see which alarms expired, and runs those. If there are more alarm
 * timers queued for the future, we set the hrtimer to fire when
 * when the next future alarm timer expires.
 */
static enum hrtimer_restart alarmtimer_fired(struct hrtimer *timer)
{
	struct alarm *alarm = container_of(timer, struct alarm, timer);
	struct alarm_base *base = &alarm_bases[alarm->type];
	unsigned long flags;
	int ret = HRTIMER_NORESTART;
	int restart = ALARMTIMER_NORESTART;

	spin_lock_irqsave(&base->lock, flags);
	alarmtimer_dequeue(base, alarm);
	spin_unlock_irqrestore(&base->lock, flags);

	if (alarm->function)
		restart = alarm->function(alarm, base->gettime());

	spin_lock_irqsave(&base->lock, flags);
	if (restart != ALARMTIMER_NORESTART) {
		hrtimer_set_expires(&alarm->timer, alarm->node.expires);
		alarmtimer_enqueue(base, alarm);
		ret = HRTIMER_RESTART;
	}
	spin_unlock_irqrestore(&base->lock, flags);

	return ret;

}

ktime_t alarm_expires_remaining(const struct alarm *alarm)
{
	struct alarm_base *base = &alarm_bases[alarm->type];
	return ktime_sub(alarm->node.expires, base->gettime());
}
EXPORT_SYMBOL_GPL(alarm_expires_remaining);

#ifdef CONFIG_RTC_CLASS
/**
 * alarmtimer_suspend - Suspend time callback
 * @dev: unused
 * @state: unused
 *
 * When we are going into suspend, we look through the bases
 * to see which is the soonest timer to expire. We then
 * set an rtc timer to fire that far into the future, which
 * will wake us from suspend.
 */
static int alarmtimer_suspend(struct device *dev)
{
	struct rtc_time tm;
	ktime_t min, now;
	unsigned long flags;
	struct rtc_device *rtc;
	int i;
	int ret;

	spin_lock_irqsave(&freezer_delta_lock, flags);
	min = freezer_delta;
	freezer_delta = ktime_set(0, 0);
	spin_unlock_irqrestore(&freezer_delta_lock, flags);

	rtc = alarmtimer_get_rtcdev();
	/* If we have no rtcdev, just return */
	if (!rtc)
		return 0;

	/* Find the soonest timer to expire*/
	for (i = 0; i < ALARM_NUMTYPE; i++) {
		struct alarm_base *base = &alarm_bases[i];
		struct timerqueue_node *next;
		ktime_t delta;

		spin_lock_irqsave(&base->lock, flags);
		next = timerqueue_getnext(&base->timerqueue);
		spin_unlock_irqrestore(&base->lock, flags);
		if (!next)
			continue;
		delta = ktime_sub(next->expires, base->gettime());
		if (!min.tv64 || (delta.tv64 < min.tv64))
			min = delta;
	}
	if (min.tv64 == 0)
		return 0;

	if (ktime_to_ns(min) < 2 * NSEC_PER_SEC) {
		__pm_wakeup_event(ws, 2 * MSEC_PER_SEC);
		return -EBUSY;
	}

	/* Setup an rtc timer to fire that far in the future */
	rtc_timer_cancel(rtc, &rtctimer);
	rtc_read_time(rtc, &tm);
	now = rtc_tm_to_ktime(tm);
	now = ktime_add(now, min);

	/* Set alarm, if in the past reject suspend briefly to handle */
	ret = rtc_timer_start(rtc, &rtctimer, now, ktime_set(0, 0));
	if (ret < 0)
		__pm_wakeup_event(ws, MSEC_PER_SEC);
	return ret;
}
#else
static int alarmtimer_suspend(struct device *dev)
{
	return 0;
}
#endif

static void alarmtimer_freezerset(ktime_t absexp, enum alarmtimer_type type)
{
	ktime_t delta;
	unsigned long flags;
	struct alarm_base *base = &alarm_bases[type];

	delta = ktime_sub(absexp, base->gettime());

	spin_lock_irqsave(&freezer_delta_lock, flags);
	if (!freezer_delta.tv64 || (delta.tv64 < freezer_delta.tv64))
		freezer_delta = delta;
	spin_unlock_irqrestore(&freezer_delta_lock, flags);
}


/**
 * alarm_init - Initialize an alarm structure
 * @alarm: ptr to alarm to be initialized
 * @type: the type of the alarm
 * @function: callback that is run when the alarm fires
 */
void alarm_init(struct alarm *alarm, enum alarmtimer_type type,
		enum alarmtimer_restart (*function)(struct alarm *, ktime_t))
{
	timerqueue_init(&alarm->node);
	hrtimer_init(&alarm->timer, alarm_bases[type].base_clockid,
			HRTIMER_MODE_ABS);
	alarm->timer.function = alarmtimer_fired;
	alarm->function = function;
	alarm->type = type;
	alarm->state = ALARMTIMER_STATE_INACTIVE;
}
EXPORT_SYMBOL_GPL(alarm_init);

/**
 * alarm_start - Sets an absolute alarm to fire
 * @alarm: ptr to alarm to set
 * @start: time to run the alarm
 */
void alarm_start(struct alarm *alarm, ktime_t start)
{
	struct alarm_base *base = &alarm_bases[alarm->type];
	unsigned long flags;

	spin_lock_irqsave(&base->lock, flags);
	alarm->node.expires = start;
	alarmtimer_enqueue(base, alarm);
	hrtimer_start(&alarm->timer, alarm->node.expires, HRTIMER_MODE_ABS);
	spin_unlock_irqrestore(&base->lock, flags);
}
EXPORT_SYMBOL_GPL(alarm_start);

/**
 * alarm_start_relative - Sets a relative alarm to fire
 * @alarm: ptr to alarm to set
 * @start: time relative to now to run the alarm
 */
void alarm_start_relative(struct alarm *alarm, ktime_t start)
{
	struct alarm_base *base = &alarm_bases[alarm->type];

	start = ktime_add(start, base->gettime());
	alarm_start(alarm, start);
}
EXPORT_SYMBOL_GPL(alarm_start_relative);

void alarm_restart(struct alarm *alarm)
{
	struct alarm_base *base = &alarm_bases[alarm->type];
	unsigned long flags;

	spin_lock_irqsave(&base->lock, flags);
	hrtimer_set_expires(&alarm->timer, alarm->node.expires);
	hrtimer_restart(&alarm->timer);
	alarmtimer_enqueue(base, alarm);
	spin_unlock_irqrestore(&base->lock, flags);
}
EXPORT_SYMBOL_GPL(alarm_restart);

/**
 * alarm_try_to_cancel - Tries to cancel an alarm timer
 * @alarm: ptr to alarm to be canceled
 *
 * Returns 1 if the timer was canceled, 0 if it was not running,
 * and -1 if the callback was running
 */
int alarm_try_to_cancel(struct alarm *alarm)
{
	struct alarm_base *base = &alarm_bases[alarm->type];
	unsigned long flags;
	int ret;

	spin_lock_irqsave(&base->lock, flags);
	ret = hrtimer_try_to_cancel(&alarm->timer);
	if (ret >= 0)
		alarmtimer_dequeue(base, alarm);
	spin_unlock_irqrestore(&base->lock, flags);
	return ret;
}
EXPORT_SYMBOL_GPL(alarm_try_to_cancel);


/**
 * alarm_cancel - Spins trying to cancel an alarm timer until it is done
 * @alarm: ptr to alarm to be canceled
 *
 * Returns 1 if the timer was canceled, 0 if it was not active.
 */
int alarm_cancel(struct alarm *alarm)
{
	for (;;) {
		int ret = alarm_try_to_cancel(alarm);
		if (ret >= 0)
			return ret;
		cpu_relax();
	}
}
EXPORT_SYMBOL_GPL(alarm_cancel);


u64 alarm_forward(struct alarm *alarm, ktime_t now, ktime_t interval)
{
	u64 overrun = 1;
	ktime_t delta;

	delta = ktime_sub(now, alarm->node.expires);

	if (delta.tv64 < 0)
		return 0;

	if (unlikely(delta.tv64 >= interval.tv64)) {
		s64 incr = ktime_to_ns(interval);

		overrun = ktime_divns(delta, incr);

		alarm->node.expires = ktime_add_ns(alarm->node.expires,
							incr*overrun);

		if (alarm->node.expires.tv64 > now.tv64)
			return overrun;
		/*
		 * This (and the ktime_add() below) is the
		 * correction for exact:
		 */
		overrun++;
	}

	alarm->node.expires = ktime_add(alarm->node.expires, interval);
	return overrun;
}
EXPORT_SYMBOL_GPL(alarm_forward);

u64 alarm_forward_now(struct alarm *alarm, ktime_t interval)
{
	struct alarm_base *base = &alarm_bases[alarm->type];

	return alarm_forward(alarm, base->gettime(), interval);
}
EXPORT_SYMBOL_GPL(alarm_forward_now);


/**
 * clock2alarm - helper that converts from clockid to alarmtypes
 * @clockid: clockid.
 */
static enum alarmtimer_type clock2alarm(clockid_t clockid)
{
	if (clockid == CLOCK_REALTIME_ALARM)
		return ALARM_REALTIME;
	if (clockid == CLOCK_BOOTTIME_ALARM)
		return ALARM_BOOTTIME;
	return -1;
}

/**
 * alarm_handle_timer - Callback for posix timers
 * @alarm: alarm that fired
 *
 * Posix timer callback for expired alarm timers.
 */
static enum alarmtimer_restart alarm_handle_timer(struct alarm *alarm,
							ktime_t now)
{
	unsigned long flags;
	struct k_itimer *ptr = container_of(alarm, struct k_itimer,
						it.alarm.alarmtimer);
	enum alarmtimer_restart result = ALARMTIMER_NORESTART;

	spin_lock_irqsave(&ptr->it_lock, flags);
	if ((ptr->it_sigev_notify & ~SIGEV_THREAD_ID) != SIGEV_NONE) {
		if (posix_timer_event(ptr, 0) != 0)
			ptr->it_overrun++;
	}

	/* Re-add periodic timers */
	if (ptr->it.alarm.interval.tv64) {
		ptr->it_overrun += alarm_forward(alarm, now,
						ptr->it.alarm.interval);
		result = ALARMTIMER_RESTART;
	}
	spin_unlock_irqrestore(&ptr->it_lock, flags);

	return result;
}

/**
 * alarm_clock_getres - posix getres interface
 * @which_clock: clockid
 * @tp: timespec to fill
 *
 * Returns the granularity of underlying alarm base clock
 */
static int alarm_clock_getres(const clockid_t which_clock, struct timespec *tp)
{
	if (!alarmtimer_get_rtcdev())
		return -EINVAL;

	tp->tv_sec = 0;
	tp->tv_nsec = hrtimer_resolution;
	return 0;
}

/**
 * alarm_clock_get - posix clock_get interface
 * @which_clock: clockid
 * @tp: timespec to fill.
 *
 * Provides the underlying alarm base time.
 */
static int alarm_clock_get(clockid_t which_clock, struct timespec *tp)
{
	struct alarm_base *base = &alarm_bases[clock2alarm(which_clock)];

	if (!alarmtimer_get_rtcdev())
		return -EINVAL;

	*tp = ktime_to_timespec(base->gettime());
	return 0;
}

/**
 * alarm_timer_create - posix timer_create interface
 * @new_timer: k_itimer pointer to manage
 *
 * Initializes the k_itimer structure.
 */
static int alarm_timer_create(struct k_itimer *new_timer)
{
	enum  alarmtimer_type type;
	struct alarm_base *base;

	if (!alarmtimer_get_rtcdev())
		return -ENOTSUPP;

	if (!capable(CAP_WAKE_ALARM))
		return -EPERM;

	type = clock2alarm(new_timer->it_clock);
	base = &alarm_bases[type];
	alarm_init(&new_timer->it.alarm.alarmtimer, type, alarm_handle_timer);
	return 0;
}

/**
 * alarm_timer_get - posix timer_get interface
 * @new_timer: k_itimer pointer
 * @cur_setting: itimerspec data to fill
 *
 * Copies out the current itimerspec data
 */
static void alarm_timer_get(struct k_itimer *timr,
				struct itimerspec *cur_setting)
{
	ktime_t relative_expiry_time =
		alarm_expires_remaining(&(timr->it.alarm.alarmtimer));

	if (ktime_to_ns(relative_expiry_time) > 0) {
		cur_setting->it_value = ktime_to_timespec(relative_expiry_time);
	} else {
		cur_setting->it_value.tv_sec = 0;
		cur_setting->it_value.tv_nsec = 0;
	}

	cur_setting->it_interval = ktime_to_timespec(timr->it.alarm.interval);
}

/**
 * alarm_timer_del - posix timer_del interface
 * @timr: k_itimer pointer to be deleted
 *
 * Cancels any programmed alarms for the given timer.
 */
static int alarm_timer_del(struct k_itimer *timr)
{
	if (!rtcdev)
		return -ENOTSUPP;

	if (alarm_try_to_cancel(&timr->it.alarm.alarmtimer) < 0)
		return TIMER_RETRY;

	return 0;
}

/**
 * alarm_timer_set - posix timer_set interface
 * @timr: k_itimer pointer to be deleted
 * @flags: timer flags
 * @new_setting: itimerspec to be used
 * @old_setting: itimerspec being replaced
 *
 * Sets the timer to new_setting, and starts the timer.
 */
static int alarm_timer_set(struct k_itimer *timr, int flags,
				struct itimerspec *new_setting,
				struct itimerspec *old_setting)
{
	ktime_t exp;

	if (!rtcdev)
		return -ENOTSUPP;

	if (flags & ~TIMER_ABSTIME)
		return -EINVAL;

	if (old_setting)
		alarm_timer_get(timr, old_setting);

	/* If the timer was already set, cancel it */
	if (alarm_try_to_cancel(&timr->it.alarm.alarmtimer) < 0)
		return TIMER_RETRY;

	/* start the timer */
	timr->it.alarm.interval = timespec_to_ktime(new_setting->it_interval);
	exp = timespec_to_ktime(new_setting->it_value);
	/* Convert (if necessary) to absolute time */
	if (flags != TIMER_ABSTIME) {
		ktime_t now;

		now = alarm_bases[timr->it.alarm.alarmtimer.type].gettime();
		exp = ktime_add(now, exp);
	}

	alarm_start(&timr->it.alarm.alarmtimer, exp);
	return 0;
}

/**
 * alarmtimer_nsleep_wakeup - Wakeup function for alarm_timer_nsleep
 * @alarm: ptr to alarm that fired
 *
 * Wakes up the task that set the alarmtimer
 */
static enum alarmtimer_restart alarmtimer_nsleep_wakeup(struct alarm *alarm,
								ktime_t now)
{
	struct task_struct *task = (struct task_struct *)alarm->data;

	alarm->data = NULL;
	if (task)
		wake_up_process(task);
	return ALARMTIMER_NORESTART;
}

/**
 * alarmtimer_do_nsleep - Internal alarmtimer nsleep implementation
 * @alarm: ptr to alarmtimer
 * @absexp: absolute expiration time
 *
 * Sets the alarm timer and sleeps until it is fired or interrupted.
 */
static int alarmtimer_do_nsleep(struct alarm *alarm, ktime_t absexp)
{
	alarm->data = (void *)current;
	do {
		set_current_state(TASK_INTERRUPTIBLE);
		alarm_start(alarm, absexp);
		if (likely(alarm->data))
			schedule();

		alarm_cancel(alarm);
	} while (alarm->data && !signal_pending(current));

	__set_current_state(TASK_RUNNING);

	return (alarm->data == NULL);
}


/**
 * update_rmtp - Update remaining timespec value
 * @exp: expiration time
 * @type: timer type
 * @rmtp: user pointer to remaining timepsec value
 *
 * Helper function that fills in rmtp value with time between
 * now and the exp value
 */
static int update_rmtp(ktime_t exp, enum  alarmtimer_type type,
			struct timespec __user *rmtp)
{
	struct timespec rmt;
	ktime_t rem;

	rem = ktime_sub(exp, alarm_bases[type].gettime());

	if (rem.tv64 <= 0)
		return 0;
	rmt = ktime_to_timespec(rem);

	if (copy_to_user(rmtp, &rmt, sizeof(*rmtp)))
		return -EFAULT;

	return 1;

}

/**
 * alarm_timer_nsleep_restart - restartblock alarmtimer nsleep
 * @restart: ptr to restart block
 *
 * Handles restarted clock_nanosleep calls
 */
static long __sched alarm_timer_nsleep_restart(struct restart_block *restart)
{
	enum  alarmtimer_type type = restart->nanosleep.clockid;
	ktime_t exp;
	struct timespec __user  *rmtp;
	struct alarm alarm;
	int ret = 0;

	exp.tv64 = restart->nanosleep.expires;
	alarm_init(&alarm, type, alarmtimer_nsleep_wakeup);

	if (alarmtimer_do_nsleep(&alarm, exp))
		goto out;

	if (freezing(current))
		alarmtimer_freezerset(exp, type);

	rmtp = restart->nanosleep.rmtp;
	if (rmtp) {
		ret = update_rmtp(exp, type, rmtp);
		if (ret <= 0)
			goto out;
	}


	/* The other values in restart are already filled in */
	ret = -ERESTART_RESTARTBLOCK;
out:
	return ret;
}

/**
 * alarm_timer_nsleep - alarmtimer nanosleep
 * @which_clock: clockid
 * @flags: determins abstime or relative
 * @tsreq: requested sleep time (abs or rel)
 * @rmtp: remaining sleep time saved
 *
 * Handles clock_nanosleep calls against _ALARM clockids
 */
static int alarm_timer_nsleep(const clockid_t which_clock, int flags,
		     struct timespec *tsreq, struct timespec __user *rmtp)
{
	enum  alarmtimer_type type = clock2alarm(which_clock);
	struct alarm alarm;
	ktime_t exp;
	int ret = 0;
	struct restart_block *restart;

	if (!alarmtimer_get_rtcdev())
		return -ENOTSUPP;

	if (flags & ~TIMER_ABSTIME)
		return -EINVAL;

	if (!capable(CAP_WAKE_ALARM))
		return -EPERM;

	alarm_init(&alarm, type, alarmtimer_nsleep_wakeup);

	exp = timespec_to_ktime(*tsreq);
	/* Convert (if necessary) to absolute time */
	if (flags != TIMER_ABSTIME) {
		ktime_t now = alarm_bases[type].gettime();
		exp = ktime_add(now, exp);
	}

	if (alarmtimer_do_nsleep(&alarm, exp))
		goto out;

	if (freezing(current))
		alarmtimer_freezerset(exp, type);

	/* abs timers don't set remaining time or restart */
	if (flags == TIMER_ABSTIME) {
		ret = -ERESTARTNOHAND;
		goto out;
	}

	if (rmtp) {
		ret = update_rmtp(exp, type, rmtp);
		if (ret <= 0)
			goto out;
	}

	restart = &current->restart_block;
	restart->fn = alarm_timer_nsleep_restart;
	restart->nanosleep.clockid = type;
	restart->nanosleep.expires = exp.tv64;
	restart->nanosleep.rmtp = rmtp;
	ret = -ERESTART_RESTARTBLOCK;

out:
	return ret;
}


/* Suspend hook structures */
static const struct dev_pm_ops alarmtimer_pm_ops = {
	.suspend = alarmtimer_suspend,
};

static struct platform_driver alarmtimer_driver = {
	.driver = {
		.name = "alarmtimer",
		.pm = &alarmtimer_pm_ops,
	}
};

/**
 * alarmtimer_init - Initialize alarm timer code
 *
 * This function initializes the alarm bases and registers
 * the posix clock ids.
 */
static int __init alarmtimer_init(void)
{
	struct platform_device *pdev;
	int error = 0;
	int i;
	struct k_clock alarm_clock = {
		.clock_getres	= alarm_clock_getres,
		.clock_get	= alarm_clock_get,
		.timer_create	= alarm_timer_create,
		.timer_set	= alarm_timer_set,
		.timer_del	= alarm_timer_del,
		.timer_get	= alarm_timer_get,
		.nsleep		= alarm_timer_nsleep,
	};

	alarmtimer_rtc_timer_init();

	posix_timers_register_clock(CLOCK_REALTIME_ALARM, &alarm_clock);
	posix_timers_register_clock(CLOCK_BOOTTIME_ALARM, &alarm_clock);

	/* Initialize alarm bases */
	alarm_bases[ALARM_REALTIME].base_clockid = CLOCK_REALTIME;
	alarm_bases[ALARM_REALTIME].gettime = &ktime_get_real;
	alarm_bases[ALARM_BOOTTIME].base_clockid = CLOCK_BOOTTIME;
	alarm_bases[ALARM_BOOTTIME].gettime = &ktime_get_boottime;
	for (i = 0; i < ALARM_NUMTYPE; i++) {
		timerqueue_init_head(&alarm_bases[i].timerqueue);
		spin_lock_init(&alarm_bases[i].lock);
	}

	error = alarmtimer_rtc_interface_setup();
	if (error)
		return error;

	error = platform_driver_register(&alarmtimer_driver);
	if (error)
		goto out_if;

	pdev = platform_device_register_simple("alarmtimer", -1, NULL, 0);
	if (IS_ERR(pdev)) {
		error = PTR_ERR(pdev);
		goto out_drv;
	}
	ws = wakeup_source_register("alarmtimer");
	return 0;

out_drv:
	platform_driver_unregister(&alarmtimer_driver);
out_if:
	alarmtimer_rtc_interface_remove();
	return error;
}
device_initcall(alarmtimer_init);