root/kernel/time/clockevents.c

DEFINITIONS

1. clockevent_delta2ns
2. clockevents_set_mode
3. clockevents_shutdown
4. clockevents_program_event
5. clockevents_register_notifier
6. clockevents_do_notify
7. clockevents_notify_released
8. clockevents_register_device
9. clockevents_handle_noop
10. clockevents_exchange_device
11. clockevents_notify

/*
 * linux/kernel/time/clockevents.c
 *
 * This file contains functions which manage clock event devices.
 *
 * Copyright(C) 2005-2006, Thomas Gleixner <tglx@linutronix.de>
 * 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 <linux/sysdev.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_SPINLOCK(clockevents_lock);

/**
 * clockevents_delta2ns - Convert a latch value (device ticks) to nanoseconds
 * @latch:      value to convert
 * @evt:        pointer to clock event device descriptor
 *
 * Math helper, returns latch value converted to nanoseconds (bound checked)
 */
unsigned long 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 > LONG_MAX)
                clc = LONG_MAX;

        return (unsigned long) clc;
}

/**
 * clockevents_set_mode - set the operating mode of a clock event device
 * @dev:        device to modify
 * @mode:       new mode
 *
 * Must be called with interrupts disabled !
 */
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;
        }
}

/**
 * clockevents_shutdown - shutdown the device and clear next_event
 * @dev:        device to shutdown
 */
void clockevents_shutdown(struct clock_event_device *dev)
{
        clockevents_set_mode(dev, CLOCK_EVT_MODE_SHUTDOWN);
        dev->next_event.tv64 = KTIME_MAX;
}

/**
 * clockevents_program_event - Reprogram the clock event device.
 * @expires:    absolute expiry time (monotonic clock)
 *
 * Returns 0 on success, -ETIME when the event is in the past.
 */
int clockevents_program_event(struct clock_event_device *dev, ktime_t expires,
                              ktime_t now)
{
        unsigned long long clc;
        int64_t delta;

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

        delta = ktime_to_ns(ktime_sub(expires, now));

        if (delta <= 0)
                return -ETIME;

        dev->next_event = expires;

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

        if (delta > dev->max_delta_ns)
                delta = dev->max_delta_ns;
        if (delta < dev->min_delta_ns)
                delta = dev->min_delta_ns;

        clc = delta * dev->mult;
        clc >>= dev->shift;

        return dev->set_next_event((unsigned long) clc, dev);
}

/**
 * clockevents_register_notifier - register a clock events change listener
 */
int clockevents_register_notifier(struct notifier_block *nb)
{
        int ret;

        spin_lock(&clockevents_lock);
        ret = raw_notifier_chain_register(&clockevents_chain, nb);
        spin_unlock(&clockevents_lock);

        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);
        }
}

/**
 * clockevents_register_device - register a clock event device
 * @dev:        device to register
 */
void clockevents_register_device(struct clock_event_device *dev)
{
        BUG_ON(dev->mode != CLOCK_EVT_MODE_UNUSED);
        /*
         * A nsec2cyc multiplicator of 0 is invalid and we'd crash
         * on it, so fix it up and emit a warning:
         */
        if (unlikely(!dev->mult)) {
                dev->mult = 1;
                WARN_ON(1);
        }

        spin_lock(&clockevents_lock);

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

        spin_unlock(&clockevents_lock);
}

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

/**
 * clockevents_exchange_device - release and request clock devices
 * @old:        device to release (can be NULL)
 * @new:        device to request (can be NULL)
 *
 * Called from the notifier chain. clockevents_lock is held already
 */
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);
}

#ifdef CONFIG_GENERIC_CLOCKEVENTS
/**
 * clockevents_notify - notification about relevant events
 */
void clockevents_notify(unsigned long reason, void *arg)
{
        struct list_head *node, *tmp;

        spin_lock(&clockevents_lock);
        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_safe(node, tmp, &clockevents_released)
                        list_del(node);
                break;
        default:
                break;
        }
        spin_unlock(&clockevents_lock);
}
EXPORT_SYMBOL_GPL(clockevents_notify);
#endif