alarmtimer.c

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/*
 * 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 <[email protected]>
 *
 * 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>

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);

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;
}


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

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;
}

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;
}


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;

}

#ifdef CONFIG_RTC_CLASS

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);
}


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;
}

int alarm_start(struct alarm *alarm, ktime_t start)
{
    struct alarm_base *base = &alarm_bases[alarm->type];
    unsigned long flags;
    int ret;

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

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;
}


int alarm_cancel(struct alarm *alarm)
{
    for (;;) {
        int ret = alarm_try_to_cancel(alarm);
        if (ret >= 0)
            return ret;
        cpu_relax();
    }
}


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;
}




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;
}

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);
    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);
        return ALARMTIMER_RESTART;
    }
    return ALARMTIMER_NORESTART;
}

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);
}

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;
}

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;
}

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.alarm.interval);
    cur_setting->it_value =
        ktime_to_timespec(timr->it.alarm.alarmtimer.node.expires);
    return;
}

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;
}

static int alarm_timer_set(struct k_itimer *timr, int flags,
                struct itimerspec *new_setting,
                struct itimerspec *old_setting)
{
    if (!rtcdev)
        return -ENOTSUPP;

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

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;
}

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);
}


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;

}

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;
}

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,
    }
};

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);