/*
 * 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;
        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);

/**
 * 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;
}


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

/**
 * 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);

        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;
        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);
}


/**
 * 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))
{
        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;
}

/**
 * alarm_start - Sets an alarm to fire
 * @alarm: ptr to alarm to set
 * @start: time to run the alarm
 */
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;
}

/**
 * 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);
        return ret;
}


/**
 * 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();
        }
}


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;
}




/**
 * 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);
        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;
}

/**
 * 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.alarm.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.alarm.interval);
        cur_setting->it_value =
                ktime_to_timespec(timr->it.alarm.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;

        if (alarm_try_to_cancel(&timr->it.alarm.alarmtimer) < 0)
                return TIMER_RETRY;

        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;

        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;
}

/**
 * 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)
{
        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);
}


/**
 * 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)
{
        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);