root/kernel/time/tick-oneshot.c

DEFINITIONS

1. tick_dev_program_event
2. tick_program_event
3. tick_resume_oneshot
4. tick_setup_oneshot
5. tick_switch_to_oneshot
6. tick_init_highres

/*
 * linux/kernel/time/tick-oneshot.c
 *
 * This file contains functions which manage high resolution tick
 * related events.
 *
 * 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/cpu.h>
#include <linux/err.h>
#include <linux/hrtimer.h>
#include <linux/interrupt.h>
#include <linux/percpu.h>
#include <linux/profile.h>
#include <linux/sched.h>
#include <linux/tick.h>

#include "tick-internal.h"

/**
 * tick_program_event internal worker function
 */
int tick_dev_program_event(struct clock_event_device *dev, ktime_t expires,
                           int force)
{
        ktime_t now = ktime_get();
        int i;

        for (i = 0;;) {
                int ret = clockevents_program_event(dev, expires, now);

                if (!ret || !force)
                        return ret;

                /*
                 * We tried 2 times to program the device with the given
                 * min_delta_ns. If that's not working then we double it
                 * and emit a warning.
                 */
                if (++i > 2) {
                        /* Increase the min. delta and try again */
                        if (!dev->min_delta_ns)
                                dev->min_delta_ns = 5000;
                        else
                                dev->min_delta_ns += dev->min_delta_ns >> 1;

                        printk(KERN_WARNING
                               "CE: %s increasing min_delta_ns to %lu nsec\n",
                               dev->name ? dev->name : "?",
                               dev->min_delta_ns << 1);

                        i = 0;
                }

                now = ktime_get();
                expires = ktime_add_ns(now, dev->min_delta_ns);
        }
}

/**
 * tick_program_event
 */
int tick_program_event(ktime_t expires, int force)
{
        struct clock_event_device *dev = __get_cpu_var(tick_cpu_device).evtdev;

        return tick_dev_program_event(dev, expires, force);
}

/**
 * tick_resume_onshot - resume oneshot mode
 */
void tick_resume_oneshot(void)
{
        struct tick_device *td = &__get_cpu_var(tick_cpu_device);
        struct clock_event_device *dev = td->evtdev;

        clockevents_set_mode(dev, CLOCK_EVT_MODE_ONESHOT);
        tick_program_event(ktime_get(), 1);
}

/**
 * tick_setup_oneshot - setup the event device for oneshot mode (hres or nohz)
 */
void tick_setup_oneshot(struct clock_event_device *newdev,
                        void (*handler)(struct clock_event_device *),
                        ktime_t next_event)
{
        newdev->event_handler = handler;
        clockevents_set_mode(newdev, CLOCK_EVT_MODE_ONESHOT);
        tick_dev_program_event(newdev, next_event, 1);
}

/**
 * tick_switch_to_oneshot - switch to oneshot mode
 */
int tick_switch_to_oneshot(void (*handler)(struct clock_event_device *))
{
        struct tick_device *td = &__get_cpu_var(tick_cpu_device);
        struct clock_event_device *dev = td->evtdev;

        if (!dev || !(dev->features & CLOCK_EVT_FEAT_ONESHOT) ||
                    !tick_device_is_functional(dev)) {

                printk(KERN_INFO "Clockevents: "
                       "could not switch to one-shot mode:");
                if (!dev) {
                        printk(" no tick device\n");
                } else {
                        if (!tick_device_is_functional(dev))
                                printk(" %s is not functional.\n", dev->name);
                        else
                                printk(" %s does not support one-shot mode.\n",
                                       dev->name);
                }
                return -EINVAL;
        }

        td->mode = TICKDEV_MODE_ONESHOT;
        dev->event_handler = handler;
        clockevents_set_mode(dev, CLOCK_EVT_MODE_ONESHOT);
        tick_broadcast_switch_to_oneshot();
        return 0;
}

#ifdef CONFIG_HIGH_RES_TIMERS
/**
 * tick_init_highres - switch to high resolution mode
 *
 * Called with interrupts disabled.
 */
int tick_init_highres(void)
{
        return tick_switch_to_oneshot(hrtimer_interrupt);
}
#endif