path: root/kernel/time/alarmtimer.c

/*
 * 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;
	struct hrtimer		timer;
	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);

#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);

/**
 * has_wakealarm - check rtc device has wakealarm ability
 * @dev: current device
 * @name_ptr: name to be returned
 *
 * This helper function checks to see if the rtc device can wake
 * from suspend.
 */
static int has_wakealarm(struct device *dev, void *name_ptr)
{
	struct rtc_device *candidate = to_rtc_device(dev);

	if (!candidate->ops->set_alarm)
		return 0;
	if (!device_may_wakeup(candidate->dev.parent))
		return 0;

	*(const char **)name_ptr = dev_name(dev);
	return 1;
}

/**
 * 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.
 */
static struct rtc_device *alarmtimer_get_rtcdev(void)
{
	struct device *dev;
	char *str;
	unsigned long flags;
	struct rtc_device *ret;

	spin_lock_irqsave(&rtcdev_lock, flags);
	if (!rtcdev) {
		/* Find an rtc device and init the rtc_timer */
		dev = class_find_device(rtc_class, NULL, &str, has_wakealarm);
		/* If we have a device then str is valid. See has_wakealarm() */
		if (dev) {
			rtcdev = rtc_class_open(str);
			/*
			 * Drop the reference we got in class_find_device,
			 * rtc_open takes its own.
			 */
			put_device(dev);
			rtc_timer_init(&rtctimer, NULL, NULL);
		}
	}
	ret = rtcdev;
	spin_unlock_irqrestore(&rtcdev_lock, flags);

	return ret;
}
#else
#define alarmtimer_get_rtcdev() (0)
#define rtcdev (0)
#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 and if necessary sets
 * an hrtimer to run.
 *
 * Must hold base->lock when calling.
 */
static void alarmtimer_enqueue(struct alarm_base *base, struct alarm *alarm)
{
	timerqueue_add(&base->timerqueue, &alarm->node);
	if (&alarm->node == timerqueue_getnext(&base->timerqueue)) {
		hrtimer_try_to_cancel(&base->timer);
		hrtimer_start(&base->timer, alarm->node.expires,
				HRTIMER_MODE_ABS);
	}
}

/**
 * alarmtimer_remove - 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 and if necessary sets
 * a new timer to run.
 *
 * Must hold base->lock when calling.
 */
static void alarmtimer_remove(struct alarm_base *base, struct alarm *alarm)
{
	struct timerqueue_node *next = timerqueue_getnext(&base->timerqueue);

	timerqueue_del(&base->timerqueue, &alarm->node);
	if (next == &alarm->node) {
		hrtimer_try_to_cancel(&base->timer);
		next = timerqueue_getnext(&base->timerqueue);
		if (!next)
			return;
		hrtimer_start(&base->timer, next->expires, HRTIMER_MODE_ABS);
	}
}


/**
 * 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_base *base = container_of(timer, struct alarm_base, timer);
	struct timerqueue_node *next;
	unsigned long flags;
	ktime_t now;
	int ret = HRTIMER_NORESTART;

	spin_lock_irqsave(&base->lock, flags);
	now = base->gettime();
	while ((next = timerqueue_getnext(&base->timerqueue))) {
		struct alarm *alarm;
		ktime_t expired = next->expires;

		if (expired.tv64 >= now.tv64)
			break;

		alarm = container_of(next, struct alarm, node);

		timerqueue_del(&base->timerqueue, &alarm->node);
		alarm->enabled = 0;
		/* Re-add periodic timers */
		if (alarm->period.tv64) {
			alarm->node.expires = ktime_add(expired, alarm->period);
			timerqueue_add(&base->timerqueue, &alarm->node);
			alarm->enabled = 1;
		}
		spin_unlock_irqrestore(&base->lock, flags);
		if (alarm->function)
			alarm->function(alarm);
		spin_lock_irqsave(&base->lock, flags);
	}

	if (next) {
		hrtimer_set_expires(&base->timer, next->expires);
		ret = HRTIMER_RESTART;
	}
	spin_unlock_irqrestore(&base->lock, flags);

	return ret;

}

#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;

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

	rtc = 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 =