uio: documentation fixups

[zen-stable.git] / kernel / time / clockevents.c

/*
 * 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>

#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);

/**
 * 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)
 */
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);

/**
 * 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;

                /*
                 * 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);
                        }
                }
        }
}

/**
 * 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;
}

#ifdef CONFIG_GENERIC_CLOCKEVENTS_MIN_ADJUST

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

/**
 * clockevents_increase_min_delta - raise minimum delta of a clock event device
 * @dev:       device to increase the minimum delta
 *
 * Returns 0 on success, -ETIME when the minimum delta reached the limit.
 */
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;
}

/**
 * clockevents_program_min_delta - Set clock event device to the minimum delay.
 * @dev:        device to program
 *
 * Returns 0 on success, -ETIME when the retry loop failed.
 */
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 */

/**
 * clockevents_program_min_delta - Set clock event device to the minimum delay.
 * @dev:        device to program
 *
 * Returns 0 on success, -ETIME when the retry loop failed.
 */
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 */

/**
 * clockevents_program_event - Reprogram the clock event device.
 * @dev:        device to program
 * @expires:    absolute expiry time (monotonic clock)
 * @force:      program minimum delay if expires can not be set
 *
 * Returns 0 on success, -ETIME when the event is in the past.
 */
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;
}

/**
 * clockevents_register_notifier - register a clock events change listener
 */
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);
        }
}

/**
 * clockevents_register_device - register a clock event device
 * @dev:        device to register
 */
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);

static 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);
}

/**
 * clockevents_config_and_register - Configure and register a clock event device
 * @dev:        device to register
 * @freq:       The clock frequency
 * @min_delta:  The minimum clock ticks to program in oneshot mode
 * @max_delta:  The maximum clock ticks to program in oneshot mode
 *
 * min/max_delta can be 0 for devices which do not support oneshot mode.
 */
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);
}

/**
 * clockevents_update_freq - Update frequency and reprogram a clock event device.
 * @dev:        device to modify
 * @freq:       new device frequency
 *
 * Reconfigure and reprogram a clock event device in oneshot
 * mode. Must be called on the cpu for which the device delivers per
 * cpu timer events with interrupts disabled!  Returns 0 on success,
 * -ETIME when the event is in the past.
 */
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)
{
}

/**
 * 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 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