LXR linux/kernel/time/tick-oneshot.c

   1/*
   2 * linux/kernel/time/tick-oneshot.c
   3 *
   4 * This file contains functions which manage high resolution tick
   5 * related events.
   6 *
   7 * Copyright(C) 2005-2006, Thomas Gleixner <tglx@linutronix.de>
   8 * Copyright(C) 2005-2007, Red Hat, Inc., Ingo Molnar
   9 * Copyright(C) 2006-2007, Timesys Corp., Thomas Gleixner
  10 *
  11 * This code is licenced under the GPL version 2. For details see
  12 * kernel-base/COPYING.
  13 */
  14#include <linux/cpu.h>
  15#include <linux/err.h>
  16#include <linux/hrtimer.h>
  17#include <linux/interrupt.h>
  18#include <linux/percpu.h>
  19#include <linux/profile.h>
  20#include <linux/sched.h>
  21
  22#include "tick-internal.h"
  23
  24/**
  25 * tick_program_event
  26 */
  27int tick_program_event(ktime_t expires, int force)
  28{
  29        struct clock_event_device *dev = __this_cpu_read(tick_cpu_device.evtdev);
  30
  31        if (unlikely(expires.tv64 == KTIME_MAX)) {
  32                /*
  33                 * We don't need the clock event device any more, stop it.
  34                 */
  35                clockevents_switch_state(dev, CLOCK_EVT_STATE_ONESHOT_STOPPED);
  36                return 0;
  37        }
  38
  39        if (unlikely(clockevent_state_oneshot_stopped(dev))) {
  40                /*
  41                 * We need the clock event again, configure it in ONESHOT mode
  42                 * before using it.
  43                 */
  44                clockevents_switch_state(dev, CLOCK_EVT_STATE_ONESHOT);
  45        }
  46
  47        return clockevents_program_event(dev, expires, force);
  48}
  49
  50/**
  51 * tick_resume_onshot - resume oneshot mode
  52 */
  53void tick_resume_oneshot(void)
  54{
  55        struct clock_event_device *dev = __this_cpu_read(tick_cpu_device.evtdev);
  56
  57        clockevents_switch_state(dev, CLOCK_EVT_STATE_ONESHOT);
  58        clockevents_program_event(dev, ktime_get(), true);
  59}
  60
  61/**
  62 * tick_setup_oneshot - setup the event device for oneshot mode (hres or nohz)
  63 */
  64void tick_setup_oneshot(struct clock_event_device *newdev,
  65                        void (*handler)(struct clock_event_device *),
  66                        ktime_t next_event)
  67{
  68        newdev->event_handler = handler;
  69        clockevents_switch_state(newdev, CLOCK_EVT_STATE_ONESHOT);
  70        clockevents_program_event(newdev, next_event, true);
  71}
  72
  73/**
  74 * tick_switch_to_oneshot - switch to oneshot mode
  75 */
  76int tick_switch_to_oneshot(void (*handler)(struct clock_event_device *))
  77{
  78        struct tick_device *td = this_cpu_ptr(&tick_cpu_device);
  79        struct clock_event_device *dev = td->evtdev;
  80
  81        if (!dev || !(dev->features & CLOCK_EVT_FEAT_ONESHOT) ||
  82                    !tick_device_is_functional(dev)) {
  83
  84                printk(KERN_INFO "Clockevents: "
  85                       "could not switch to one-shot mode:");
  86                if (!dev) {
  87                        printk(" no tick device\n");
  88                } else {
  89                        if (!tick_device_is_functional(dev))
  90                                printk(" %s is not functional.\n", dev->name);
  91                        else
  92                                printk(" %s does not support one-shot mode.\n",
  93                                       dev->name);
  94                }
  95                return -EINVAL;
  96        }
  97
  98        td->mode = TICKDEV_MODE_ONESHOT;
  99        dev->event_handler = handler;
 100        clockevents_switch_state(dev, CLOCK_EVT_STATE_ONESHOT);
 101        tick_broadcast_switch_to_oneshot();
 102        return 0;
 103}
 104
 105/**
 106 * tick_check_oneshot_mode - check whether the system is in oneshot mode
 107 *
 108 * returns 1 when either nohz or highres are enabled. otherwise 0.
 109 */
 110int tick_oneshot_mode_active(void)
 111{
 112        unsigned long flags;
 113        int ret;
 114
 115        local_irq_save(flags);
 116        ret = __this_cpu_read(tick_cpu_device.mode) == TICKDEV_MODE_ONESHOT;
 117        local_irq_restore(flags);
 118
 119        return ret;
 120}
 121
 122#ifdef CONFIG_HIGH_RES_TIMERS
 123/**
 124 * tick_init_highres - switch to high resolution mode
 125 *
 126 * Called with interrupts disabled.
 127 */
 128int tick_init_highres(void)
 129{
 130        return tick_switch_to_oneshot(hrtimer_interrupt);
 131}
 132#endif
 133