clockevents.c

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/*
 * linux/kernel/time/clockevents.c
 *
 * This file contains functions which manage clock event devices.
 *
 * Copyright(C) 2005-2006, Thomas Gleixner <[email protected]>
 * Copyright(C) 2005-2007, Red Hat, Inc., Ingo Molnar
 * Copyright(C) 2006-2007, Timesys Corp., Thomas Gleixner
 *
 * This code is licenced under the GPL version 2. For details see
 * kernel-base/COPYING.
 */

#include <linux/clockchips.h>
#include <linux/hrtimer.h>
#include <linux/init.h>
#include <linux/module.h>
#include <linux/notifier.h>
#include <linux/smp.h>

#include "tick-internal.h"

/* The registered clock event devices */
static LIST_HEAD(clockevent_devices);
static LIST_HEAD(clockevents_released);

/* Notification for clock events */
static RAW_NOTIFIER_HEAD(clockevents_chain);

/* Protection for the above */
static DEFINE_RAW_SPINLOCK(clockevents_lock);

u64 clockevent_delta2ns(unsigned long latch, struct clock_event_device *evt)
{
    u64 clc = (u64) latch << evt->shift;

    if (unlikely(!evt->mult)) {
        evt->mult = 1;
        WARN_ON(1);
    }

    do_div(clc, evt->mult);
    if (clc < 1000)
        clc = 1000;
    if (clc > KTIME_MAX)
        clc = KTIME_MAX;

    return clc;
}
EXPORT_SYMBOL_GPL(clockevent_delta2ns);

void clockevents_set_mode(struct clock_event_device *dev,
                 enum clock_event_mode mode)
{
    if (dev->mode != mode) {
        dev->set_mode(mode, dev);
        dev->mode = mode;

        /*
         * A nsec2cyc multiplicator of 0 is invalid and we'd crash
         * on it, so fix it up and emit a warning:
         */
        if (mode == CLOCK_EVT_MODE_ONESHOT) {
            if (unlikely(!dev->mult)) {
                dev->mult = 1;
                WARN_ON(1);
            }
        }
    }
}

void clockevents_shutdown(struct clock_event_device *dev)
{
    clockevents_set_mode(dev, CLOCK_EVT_MODE_SHUTDOWN);
    dev->next_event.tv64 = KTIME_MAX;
}

#ifdef CONFIG_GENERIC_CLOCKEVENTS_MIN_ADJUST

/* Limit min_delta to a jiffie */
#define MIN_DELTA_LIMIT     (NSEC_PER_SEC / HZ)

static int clockevents_increase_min_delta(struct clock_event_device *dev)
{
    /* Nothing to do if we already reached the limit */
    if (dev->min_delta_ns >= MIN_DELTA_LIMIT) {
        printk(KERN_WARNING "CE: Reprogramming failure. Giving up\n");
        dev->next_event.tv64 = KTIME_MAX;
        return -ETIME;
    }

    if (dev->min_delta_ns < 5000)
        dev->min_delta_ns = 5000;
    else
        dev->min_delta_ns += dev->min_delta_ns >> 1;

    if (dev->min_delta_ns > MIN_DELTA_LIMIT)
        dev->min_delta_ns = MIN_DELTA_LIMIT;

    printk(KERN_WARNING "CE: %s increased min_delta_ns to %llu nsec\n",
           dev->name ? dev->name : "?",
           (unsigned long long) dev->min_delta_ns);
    return 0;
}

static int clockevents_program_min_delta(struct clock_event_device *dev)
{
    unsigned long long clc;
    int64_t delta;
    int i;

    for (i = 0;;) {
        delta = dev->min_delta_ns;
        dev->next_event = ktime_add_ns(ktime_get(), delta);

        if (dev->mode == CLOCK_EVT_MODE_SHUTDOWN)
            return 0;

        dev->retries++;
        clc = ((unsigned long long) delta * dev->mult) >> dev->shift;
        if (dev->set_next_event((unsigned long) clc, dev) == 0)
            return 0;

        if (++i > 2) {
            /*
             * We tried 3 times to program the device with the
             * given min_delta_ns. Try to increase the minimum
             * delta, if that fails as well get out of here.
             */
            if (clockevents_increase_min_delta(dev))
                return -ETIME;
            i = 0;
        }
    }
}

#else  /* CONFIG_GENERIC_CLOCKEVENTS_MIN_ADJUST */

static int clockevents_program_min_delta(struct clock_event_device *dev)
{
    unsigned long long clc;
    int64_t delta;

    delta = dev->min_delta_ns;
    dev->next_event = ktime_add_ns(ktime_get(), delta);

    if (dev->mode == CLOCK_EVT_MODE_SHUTDOWN)
        return 0;

    dev->retries++;
    clc = ((unsigned long long) delta * dev->mult) >> dev->shift;
    return dev->set_next_event((unsigned long) clc, dev);
}

#endif /* CONFIG_GENERIC_CLOCKEVENTS_MIN_ADJUST */

int clockevents_program_event(struct clock_event_device *dev, ktime_t expires,
                  bool force)
{
    unsigned long long clc;
    int64_t delta;
    int rc;

    if (unlikely(expires.tv64 < 0)) {
        WARN_ON_ONCE(1);
        return -ETIME;
    }

    dev->next_event = expires;

    if (dev->mode == CLOCK_EVT_MODE_SHUTDOWN)
        return 0;

    /* Shortcut for clockevent devices that can deal with ktime. */
    if (dev->features & CLOCK_EVT_FEAT_KTIME)
        return dev->set_next_ktime(expires, dev);

    delta = ktime_to_ns(ktime_sub(expires, ktime_get()));
    if (delta <= 0)
        return force ? clockevents_program_min_delta(dev) : -ETIME;

    delta = min(delta, (int64_t) dev->max_delta_ns);
    delta = max(delta, (int64_t) dev->min_delta_ns);

    clc = ((unsigned long long) delta * dev->mult) >> dev->shift;
    rc = dev->set_next_event((unsigned long) clc, dev);

    return (rc && force) ? clockevents_program_min_delta(dev) : rc;
}

int clockevents_register_notifier(struct notifier_block *nb)
{
    unsigned long flags;
    int ret;

    raw_spin_lock_irqsave(&clockevents_lock, flags);
    ret = raw_notifier_chain_register(&clockevents_chain, nb);
    raw_spin_unlock_irqrestore(&clockevents_lock, flags);

    return ret;
}

/*
 * Notify about a clock event change. Called with clockevents_lock
 * held.
 */
static void clockevents_do_notify(unsigned long reason, void *dev)
{
    raw_notifier_call_chain(&clockevents_chain, reason, dev);
}

/*
 * Called after a notify add to make devices available which were
 * released from the notifier call.
 */
static void clockevents_notify_released(void)
{
    struct clock_event_device *dev;

    while (!list_empty(&clockevents_released)) {
        dev = list_entry(clockevents_released.next,
                 struct clock_event_device, list);
        list_del(&dev->list);
        list_add(&dev->list, &clockevent_devices);
        clockevents_do_notify(CLOCK_EVT_NOTIFY_ADD, dev);
    }
}

void clockevents_register_device(struct clock_event_device *dev)
{
    unsigned long flags;

    BUG_ON(dev->mode != CLOCK_EVT_MODE_UNUSED);
    if (!dev->cpumask) {
        WARN_ON(num_possible_cpus() > 1);
        dev->cpumask = cpumask_of(smp_processor_id());
    }

    raw_spin_lock_irqsave(&clockevents_lock, flags);

    list_add(&dev->list, &clockevent_devices);
    clockevents_do_notify(CLOCK_EVT_NOTIFY_ADD, dev);
    clockevents_notify_released();

    raw_spin_unlock_irqrestore(&clockevents_lock, flags);
}
EXPORT_SYMBOL_GPL(clockevents_register_device);

void clockevents_config(struct clock_event_device *dev, u32 freq)
{
    u64 sec;

    if (!(dev->features & CLOCK_EVT_FEAT_ONESHOT))
        return;

    /*
     * Calculate the maximum number of seconds we can sleep. Limit
     * to 10 minutes for hardware which can program more than
     * 32bit ticks so we still get reasonable conversion values.
     */
    sec = dev->max_delta_ticks;
    do_div(sec, freq);
    if (!sec)
        sec = 1;
    else if (sec > 600 && dev->max_delta_ticks > UINT_MAX)
        sec = 600;

    clockevents_calc_mult_shift(dev, freq, sec);
    dev->min_delta_ns = clockevent_delta2ns(dev->min_delta_ticks, dev);
    dev->max_delta_ns = clockevent_delta2ns(dev->max_delta_ticks, dev);
}

void clockevents_config_and_register(struct clock_event_device *dev,
                     u32 freq, unsigned long min_delta,
                     unsigned long max_delta)
{
    dev->min_delta_ticks = min_delta;
    dev->max_delta_ticks = max_delta;
    clockevents_config(dev, freq);
    clockevents_register_device(dev);
}

int clockevents_update_freq(struct clock_event_device *dev, u32 freq)
{
    clockevents_config(dev, freq);

    if (dev->mode != CLOCK_EVT_MODE_ONESHOT)
        return 0;

    return clockevents_program_event(dev, dev->next_event, false);
}

/*
 * Noop handler when we shut down an event device
 */
void clockevents_handle_noop(struct clock_event_device *dev)
{
}

void clockevents_exchange_device(struct clock_event_device *old,
                 struct clock_event_device *new)
{
    unsigned long flags;

    local_irq_save(flags);
    /*
     * Caller releases a clock event device. We queue it into the
     * released list and do a notify add later.
     */
    if (old) {
        clockevents_set_mode(old, CLOCK_EVT_MODE_UNUSED);
        list_del(&old->list);
        list_add(&old->list, &clockevents_released);
    }

    if (new) {
        BUG_ON(new->mode != CLOCK_EVT_MODE_UNUSED);
        clockevents_shutdown(new);
    }
    local_irq_restore(flags);
}

void clockevents_suspend(void)
{
    struct clock_event_device *dev;

    list_for_each_entry_reverse(dev, &clockevent_devices, list)
        if (dev->suspend)
            dev->suspend(dev);
}

void clockevents_resume(void)
{
    struct clock_event_device *dev;

    list_for_each_entry(dev, &clockevent_devices, list)
        if (dev->resume)
            dev->resume(dev);
}

#ifdef CONFIG_GENERIC_CLOCKEVENTS

void clockevents_notify(unsigned long reason, void *arg)
{
    struct clock_event_device *dev, *tmp;
    unsigned long flags;
    int cpu;

    raw_spin_lock_irqsave(&clockevents_lock, flags);
    clockevents_do_notify(reason, arg);

    switch (reason) {
    case CLOCK_EVT_NOTIFY_CPU_DEAD:
        /*
         * Unregister the clock event devices which were
         * released from the users in the notify chain.
         */
        list_for_each_entry_safe(dev, tmp, &clockevents_released, list)
            list_del(&dev->list);
        /*
         * Now check whether the CPU has left unused per cpu devices
         */
        cpu = *((int *)arg);
        list_for_each_entry_safe(dev, tmp, &clockevent_devices, list) {
            if (cpumask_test_cpu(cpu, dev->cpumask) &&
                cpumask_weight(dev->cpumask) == 1 &&
                !tick_is_broadcast_device(dev)) {
                BUG_ON(dev->mode != CLOCK_EVT_MODE_UNUSED);
                list_del(&dev->list);
            }
        }
        break;
    default:
        break;
    }
    raw_spin_unlock_irqrestore(&clockevents_lock, flags);
}
EXPORT_SYMBOL_GPL(clockevents_notify);
#endif