[mirror_ubuntu-hirsute-kernel.git] / kernel / time / alarmtimer.c

// 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 -ENOTSUPP;

        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 -ENOTSUPP;

        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);