/*
   * 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 = &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;
  
  	/* XXX - Should we enforce a minimum sleep time? */
  	WARN_ON(min.tv64 < NSEC_PER_SEC);
  
  	/* 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);

  	rtc_timer_start(rtc, &rtctimer, now, ktime_set(0, 0));

  
  	return 0;
  }

  #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,
  		void (*function)(struct alarm *))
  {
  	timerqueue_init(&alarm->node);
  	alarm->period = ktime_set(0, 0);
  	alarm->function = function;
  	alarm->type = type;
  	alarm->enabled = 0;
  }

  /**

   * alarm_start - Sets an alarm to fire
   * @alarm: ptr to alarm to set
   * @start: time to run the alarm
   * @period: period at which the alarm will recur

   */
  void alarm_start(struct alarm *alarm, ktime_t start, ktime_t period)
  {
  	struct alarm_base *base = &alarm_bases[alarm->type];
  	unsigned long flags;
  
  	spin_lock_irqsave(&base->lock, flags);
  	if (alarm->enabled)
  		alarmtimer_remove(base, alarm);
  	alarm->node.expires = start;
  	alarm->period = period;
  	alarmtimer_enqueue(base, alarm);
  	alarm->enabled = 1;
  	spin_unlock_irqrestore(&base->lock, flags);
  }

  /**

   * alarm_cancel - Tries to cancel an alarm timer
   * @alarm: ptr to alarm to be canceled

   */
  void alarm_cancel(struct alarm *alarm)
  {
  	struct alarm_base *base = &alarm_bases[alarm->type];
  	unsigned long flags;
  
  	spin_lock_irqsave(&base->lock, flags);
  	if (alarm->enabled)
  		alarmtimer_remove(base, alarm);
  	alarm->enabled = 0;
  	spin_unlock_irqrestore(&base->lock, flags);
  }

  /**

   * 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 void alarm_handle_timer(struct alarm *alarm)
  {
  	struct k_itimer *ptr = container_of(alarm, struct k_itimer,
  						it.alarmtimer);
  	if (posix_timer_event(ptr, 0) != 0)
  		ptr->it_overrun++;
  }

  /**

   * 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)
  {
  	clockid_t baseid = alarm_bases[clock2alarm(which_clock)].base_clockid;

  	if (!alarmtimer_get_rtcdev())
  		return -ENOTSUPP;

  	return hrtimer_get_res(baseid, tp);
  }
  
  /**
   * 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 -ENOTSUPP;

  	*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.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 the itimerspec data out from the k_itimer
   */
  static void alarm_timer_get(struct k_itimer *timr,
  				struct itimerspec *cur_setting)
  {

  	memset(cur_setting, 0, sizeof(struct itimerspec));

  	cur_setting->it_interval =
  			ktime_to_timespec(timr->it.alarmtimer.period);
  	cur_setting->it_value =
  			ktime_to_timespec(timr->it.alarmtimer.node.expires);
  	return;
  }
  
  /**
   * 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;

  	alarm_cancel(&timr->it.alarmtimer);
  	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)
  {

  	if (!rtcdev)
  		return -ENOTSUPP;

  	/*
  	 * XXX HACK! Currently we can DOS a system if the interval
  	 * period on alarmtimers is too small. Cap the interval here
  	 * to 100us and solve this properly in a future patch! -jstultz
  	 */
  	if ((new_setting->it_interval.tv_sec == 0) &&
  			(new_setting->it_interval.tv_nsec < 100000))
  		new_setting->it_interval.tv_nsec = 100000;

  	if (old_setting)
  		alarm_timer_get(timr, old_setting);

  
  	/* If the timer was already set, cancel it */
  	alarm_cancel(&timr->it.alarmtimer);
  
  	/* start the timer */
  	alarm_start(&timr->it.alarmtimer,
  			timespec_to_ktime(new_setting->it_value),
  			timespec_to_ktime(new_setting->it_interval));
  	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 void alarmtimer_nsleep_wakeup(struct alarm *alarm)
  {
  	struct task_struct *task = (struct task_struct *)alarm->data;
  
  	alarm->data = NULL;
  	if (task)
  		wake_up_process(task);
  }
  
  /**
   * 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, ktime_set(0, 0));
  		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 (!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_thread_info()->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)
  {
  	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,
  	};
  
  	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);
  		hrtimer_init(&alarm_bases[i].timer,
  				alarm_bases[i].base_clockid,
  				HRTIMER_MODE_ABS);
  		alarm_bases[i].timer.function = alarmtimer_fired;

  	}
  	error = platform_driver_register(&alarmtimer_driver);
  	platform_device_register_simple("alarmtimer", -1, NULL, 0);
  
  	return error;
  }
  device_initcall(alarmtimer_init);