text: // SPDX-License-Identifier: GPL-2.0
  /*
   * 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>
   */
  #include <linux/time.h>
  #include <linux/hrtimer.h>
  #include <linux/timerqueue.h>
  #include <linux/rtc.h>
  #include <linux/sched/signal.h>
  #include <linux/sched/debug.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>
  #include <linux/compat.h>
  #include <linux/module.h>
  
  #include "posix-timers.h"
  
  #define CREATE_TRACE_POINTS
  #include <trace/events/alarmtimer.h>
  
  /**
   * struct alarm_base - Alarm timer bases
   * @lock:		Lock for syncrhonized access to the base
   * @timerqueue:		Timerqueue head managing the list of events
   * @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];
  
  #if defined(CONFIG_POSIX_TIMERS) || defined(CONFIG_RTC_CLASS)
  /* freezer information to handle clock_nanosleep triggered wakeups */
  static enum alarmtimer_type freezer_alarmtype;
  static ktime_t freezer_expires;
  static ktime_t freezer_delta;
  static DEFINE_SPINLOCK(freezer_delta_lock);
  #endif
  
  #ifdef CONFIG_RTC_CLASS
  static struct wakeup_source *ws;
  
  /* 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);
  	struct wakeup_source *__ws;
  
  	if (rtcdev)
  		return -EBUSY;
  
  	if (!rtc->ops->set_alarm)
  		return -1;
  	if (!device_may_wakeup(rtc->dev.parent))
  		return -1;
  
  	__ws = wakeup_source_register("alarmtimer");
  
  	spin_lock_irqsave(&rtcdev_lock, flags);
  	if (!rtcdev) {
  		if (!try_module_get(rtc->owner)) {
  			spin_unlock_irqrestore(&rtcdev_lock, flags);
  			return -1;
  		}
  
  		rtcdev = rtc;
  		/* hold a reference so it doesn't go away */
  		get_device(dev);
  		ws = __ws;
  		__ws = NULL;
  	}
  	spin_unlock_irqrestore(&rtcdev_lock, flags);
  
  	wakeup_source_unregister(__ws);
  
  	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);
  
  	trace_alarmtimer_fired(alarm, base->gettime());
  	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
   *
   * 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)
  {
  	ktime_t min, now, expires;
  	int i, ret, type;
  	struct rtc_device *rtc;
  	unsigned long flags;
  	struct rtc_time tm;
  
  	spin_lock_irqsave(&freezer_delta_lock, flags);
  	min = freezer_delta;
  	expires = freezer_expires;
  	type = freezer_alarmtype;
  	freezer_delta = 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 || (delta < min)) {
  			expires = next->expires;
  			min = delta;
  			type = i;
  		}
  	}
  	if (min == 0)
  		return 0;
  
  	if (ktime_to_ns(min) < 2 * NSEC_PER_SEC) {
  		__pm_wakeup_event(ws, 2 * MSEC_PER_SEC);
  		return -EBUSY;
  	}
  
  	trace_alarmtimer_suspend(expires, type);
  
  	/* 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, 0);
  	if (ret < 0)
  		__pm_wakeup_event(ws, MSEC_PER_SEC);
  	return ret;
  }
  
  static int alarmtimer_resume(struct device *dev)
  {
  	struct rtc_device *rtc;
  
  	rtc = alarmtimer_get_rtcdev();
  	if (rtc)
  		rtc_timer_cancel(rtc, &rtctimer);
  	return 0;
  }
  
  #else
  static int alarmtimer_suspend(struct device *dev)
  {
  	return 0;
  }
  
  static int alarmtimer_resume(struct device *dev)
  {
  	return 0;
  }
  #endif
  
  static void
  __alarm_init(struct alarm *alarm, enum alarmtimer_type type,
  	     enum alarmtimer_restart (*function)(struct alarm *, ktime_t))
  {
  	timerqueue_init(&alarm->node);
  	alarm->timer.function = alarmtimer_fired;
  	alarm->function = function;
  	alarm->type = type;
  	alarm->state = ALARMTIMER_STATE_INACTIVE;
  }
  
  /**
   * 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))
  {
  	hrtimer_init(&alarm->timer, alarm_bases[type].base_clockid,
  		     HRTIMER_MODE_ABS);
  	__alarm_init(alarm, type, function);
  }
  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);
  
  	trace_alarmtimer_start(alarm, base->gettime());
  }
  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_safe(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);
  
  	trace_alarmtimer_cancel(alarm, base->gettime());
  	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 < 0)
  		return 0;
  
  	if (unlikely(delta >= interval)) {
  		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 > now)
  			return overrun;
  		/*
  		 * This (and the ktime_add() below) is the
  		 * correction for exact:
  		 */
  		overrun++;
  	}
  
  	alarm->node.expires = ktime_add_safe(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);
  
  #ifdef CONFIG_POSIX_TIMERS
  
  static void alarmtimer_freezerset(ktime_t absexp, enum alarmtimer_type type)
  {
  	struct alarm_base *base;
  	unsigned long flags;
  	ktime_t delta;
  
  	switch(type) {
  	case ALARM_REALTIME:
  		base = &alarm_bases[ALARM_REALTIME];
  		type = ALARM_REALTIME_FREEZER;
  		break;
  	case ALARM_BOOTTIME:
  		base = &alarm_bases[ALARM_BOOTTIME];
  		type = ALARM_BOOTTIME_FREEZER;
  		break;
  	default:
  		WARN_ONCE(1, "Invalid alarm type: %d\n", type);
  		return;
  	}
  
  	delta = ktime_sub(absexp, base->gettime());
  
  	spin_lock_irqsave(&freezer_delta_lock, flags);
  	if (!freezer_delta || (delta < freezer_delta)) {
  		freezer_delta = delta;
  		freezer_expires = absexp;
  		freezer_alarmtype = type;
  	}
  	spin_unlock_irqrestore(&freezer_delta_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 enum alarmtimer_restart alarm_handle_timer(struct alarm *alarm,
  							ktime_t now)
  {
  	struct k_itimer *ptr = container_of(alarm, struct k_itimer,
  					    it.alarm.alarmtimer);
  	enum alarmtimer_restart result = ALARMTIMER_NORESTART;
  	unsigned long flags;
  	int si_private = 0;
  
  	spin_lock_irqsave(&ptr->it_lock, flags);
  
  	ptr->it_active = 0;
  	if (ptr->it_interval)
  		si_private = ++ptr->it_requeue_pending;
  
  	if (posix_timer_event(ptr, si_private) && ptr->it_interval) {
  		/*
  		 * Handle ignored signals and rearm the timer. This will go
  		 * away once we handle ignored signals proper.
  		 */
  		ptr->it_overrun += alarm_forward_now(alarm, ptr->it_interval);
  		++ptr->it_requeue_pending;
  		ptr->it_active = 1;
  		result = ALARMTIMER_RESTART;
  	}
  	spin_unlock_irqrestore(&ptr->it_lock, flags);
  
  	return result;
  }
  
  /**
   * alarm_timer_rearm - Posix timer callback for rearming timer
   * @timr:	Pointer to the posixtimer data struct
   */
  static void alarm_timer_rearm(struct k_itimer *timr)
  {
  	struct alarm *alarm = &timr->it.alarm.alarmtimer;
  
  	timr->it_overrun += alarm_forward_now(alarm, timr->it_interval);
  	alarm_start(alarm, alarm->node.expires);
  }
  
  /**
   * alarm_timer_forward - Posix timer callback for forwarding timer
   * @timr:	Pointer to the posixtimer data struct
   * @now:	Current time to forward the timer against
   */
  static s64 alarm_timer_forward(struct k_itimer *timr, ktime_t now)
  {
  	struct alarm *alarm = &timr->it.alarm.alarmtimer;
  
  	return alarm_forward(alarm, timr->it_interval, now);
  }
  
  /**
   * alarm_timer_remaining - Posix timer callback to retrieve remaining time
   * @timr:	Pointer to the posixtimer data struct
   * @now:	Current time to calculate against
   */
  static ktime_t alarm_timer_remaining(struct k_itimer *timr, ktime_t now)
  {
  	struct alarm *alarm = &timr->it.alarm.alarmtimer;
  
  	return ktime_sub(alarm->node.expires, now);
  }
  
  /**
   * alarm_timer_try_to_cancel - Posix timer callback to cancel a timer
   * @timr:	Pointer to the posixtimer data struct
   */
  static int alarm_timer_try_to_cancel(struct k_itimer *timr)
  {
  	return alarm_try_to_cancel(&timr->it.alarm.alarmtimer);
  }
  
  /**
   * alarm_timer_arm - Posix timer callback to arm a timer
   * @timr:	Pointer to the posixtimer data struct
   * @expires:	The new expiry time
   * @absolute:	Expiry value is absolute time
   * @sigev_none:	Posix timer does not deliver signals
   */
  static void alarm_timer_arm(struct k_itimer *timr, ktime_t expires,
  			    bool absolute, bool sigev_none)
  {
  	struct alarm *alarm = &timr->it.alarm.alarmtimer;
  	struct alarm_base *base = &alarm_bases[alarm->type];
  
  	if (!absolute)
  		expires = ktime_add_safe(expires, base->gettime());
  	if (sigev_none)
  		alarm->node.expires = expires;
  	else
  		alarm_start(&timr->it.alarm.alarmtimer, expires);
  }
  
  /**
   * 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 timespec64 *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 timespec64 *tp)
  {
  	struct alarm_base *base = &alarm_bases[clock2alarm(which_clock)];
  
  	if (!alarmtimer_get_rtcdev())
  		return -EINVAL;
  
  	*tp = ktime_to_timespec64(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;
  
  	if (!alarmtimer_get_rtcdev())
  		return -EOPNOTSUPP;
  
  	if (!capable(CAP_WAKE_ALARM))
  		return -EPERM;
  
  	type = clock2alarm(new_timer->it_clock);
  	alarm_init(&new_timer->it.alarm.alarmtimer, type, alarm_handle_timer);
  	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,
  				enum alarmtimer_type type)
  {
  	struct restart_block *restart;
  	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);
  
  	destroy_hrtimer_on_stack(&alarm->timer);
  
  	if (!alarm->data)
  		return 0;
  
  	if (freezing(current))
  		alarmtimer_freezerset(absexp, type);
  	restart = &current->restart_block;
  	if (restart->nanosleep.type != TT_NONE) {
  		struct timespec64 rmt;
  		ktime_t rem;
  
  		rem = ktime_sub(absexp, alarm_bases[type].gettime());
  
  		if (rem <= 0)
  			return 0;
  		rmt = ktime_to_timespec64(rem);
  
  		return nanosleep_copyout(restart, &rmt);
  	}
  	return -ERESTART_RESTARTBLOCK;
  }
  
  static void
  alarm_init_on_stack(struct alarm *alarm, enum alarmtimer_type type,
  		    enum alarmtimer_restart (*function)(struct alarm *, ktime_t))
  {
  	hrtimer_init_on_stack(&alarm->timer, alarm_bases[type].base_clockid,
  			      HRTIMER_MODE_ABS);
  	__alarm_init(alarm, type, function);
  }
  
  /**
   * 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 = restart->nanosleep.expires;
  	struct alarm alarm;
  
  	alarm_init_on_stack(&alarm, type, alarmtimer_nsleep_wakeup);
  
  	return alarmtimer_do_nsleep(&alarm, exp, type);
  }
  
  /**
   * 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,
  			      const struct timespec64 *tsreq)
  {
  	enum  alarmtimer_type type = clock2alarm(which_clock);
  	struct restart_block *restart = &current->restart_block;
  	struct alarm alarm;
  	ktime_t exp;
  	int ret = 0;
  
  	if (!alarmtimer_get_rtcdev())
  		return -EOPNOTSUPP;
  
  	if (flags & ~TIMER_ABSTIME)
  		return -EINVAL;
  
  	if (!capable(CAP_WAKE_ALARM))
  		return -EPERM;
  
  	alarm_init_on_stack(&alarm, type, alarmtimer_nsleep_wakeup);
  
  	exp = timespec64_to_ktime(*tsreq);
  	/* Convert (if necessary) to absolute time */
  	if (flags != TIMER_ABSTIME) {
  		ktime_t now = alarm_bases[type].gettime();
  
  		exp = ktime_add_safe(now, exp);
  	}
  
  	ret = alarmtimer_do_nsleep(&alarm, exp, type);
  	if (ret != -ERESTART_RESTARTBLOCK)
  		return ret;
  
  	/* abs timers don't set remaining time or restart */
  	if (flags == TIMER_ABSTIME)
  		return -ERESTARTNOHAND;
  
  	restart->fn = alarm_timer_nsleep_restart;
  	restart->nanosleep.clockid = type;
  	restart->nanosleep.expires = exp;
  	return ret;
  }
  
  const struct k_clock alarm_clock = {
  	.clock_getres		= alarm_clock_getres,
  	.clock_get		= alarm_clock_get,
  	.timer_create		= alarm_timer_create,
  	.timer_set		= common_timer_set,
  	.timer_del		= common_timer_del,
  	.timer_get		= common_timer_get,
  	.timer_arm		= alarm_timer_arm,
  	.timer_rearm		= alarm_timer_rearm,
  	.timer_forward		= alarm_timer_forward,
  	.timer_remaining	= alarm_timer_remaining,
  	.timer_try_to_cancel	= alarm_timer_try_to_cancel,
  	.nsleep			= alarm_timer_nsleep,
  };
  #endif /* CONFIG_POSIX_TIMERS */
  
  
  /* Suspend hook structures */
  static const struct dev_pm_ops alarmtimer_pm_ops = {
  	.suspend = alarmtimer_suspend,
  	.resume = alarmtimer_resume,
  };
  
  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;
  
  	alarmtimer_rtc_timer_init();
  
  	/* 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;
  	}
  	return 0;
  
  out_drv:
  	platform_driver_unregister(&alarmtimer_driver);
  out_if:
  	alarmtimer_rtc_interface_remove();
  	return error;
  }
  device_initcall(alarmtimer_init);
  