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 #include <linux/tick.h>
  22
  23 #include "tick-internal.h"
  24
  25 /**
  26  * tick_program_event
  27  */
  28 int tick_program_event(ktime_t expires, int force)
  29 {
  30         struct clock_event_device *dev = __get_cpu_var(tick_cpu_device).evtdev;
  31         ktime_t now = ktime_get();
  32
  33         while (1) {
  34                 int ret = clockevents_program_event(dev, expires, now);
  35
  36                 if (!ret || !force)
  37                         return ret;
  38                 now = ktime_get();
  39                 expires = ktime_add(now, ktime_set(0, dev->min_delta_ns));
  40         }
  41 }
  42
  43 /**
  44  * tick_resume_onshot - resume oneshot mode
  45  */
  46 void tick_resume_oneshot(void)
  47 {
  48         struct tick_device *td = &__get_cpu_var(tick_cpu_device);
  49         struct clock_event_device *dev = td->evtdev;
  50
  51         clockevents_set_mode(dev, CLOCK_EVT_MODE_ONESHOT);
  52         tick_program_event(ktime_get(), 1);
  53 }
  54
  55 /**
  56  * tick_setup_oneshot - setup the event device for oneshot mode (hres or nohz)
  57  */
  58 void tick_setup_oneshot(struct clock_event_device *newdev,
  59                         void (*handler)(struct clock_event_device *),
  60                         ktime_t next_event)
  61 {
  62         newdev->event_handler = handler;
  63         clockevents_set_mode(newdev, CLOCK_EVT_MODE_ONESHOT);
  64         clockevents_program_event(newdev, next_event, ktime_get());
  65 }
  66
  67 /**
  68  * tick_switch_to_oneshot - switch to oneshot mode
  69  */
  70 int tick_switch_to_oneshot(void (*handler)(struct clock_event_device *))
  71 {
  72         struct tick_device *td = &__get_cpu_var(tick_cpu_device);
  73         struct clock_event_device *dev = td->evtdev;
  74
  75         if (!dev || !(dev->features & CLOCK_EVT_FEAT_ONESHOT) ||
  76                     !tick_device_is_functional(dev)) {
  77
  78                 printk(KERN_INFO "Clockevents: "
  79                        "could not switch to one-shot mode:");
  80                 if (!dev) {
  81                         printk(" no tick device\n");
  82                 } else {
  83                         if (!tick_device_is_functional(dev))
  84                                 printk(" %s is not functional.\n", dev->name);
  85                         else
  86                                 printk(" %s does not support one-shot mode.\n",
  87                                        dev->name);
  88                 }
  89                 return -EINVAL;
  90         }
  91
  92         td->mode = TICKDEV_MODE_ONESHOT;
  93         dev->event_handler = handler;
  94         clockevents_set_mode(dev, CLOCK_EVT_MODE_ONESHOT);
  95         tick_broadcast_switch_to_oneshot();
  96         return 0;
  97 }
  98
  99 #ifdef CONFIG_HIGH_RES_TIMERS
 100 /**
 101  * tick_init_highres - switch to high resolution mode
 102  *
 103  * Called with interrupts disabled.
 104  */
 105 int tick_init_highres(void)
 106 {
 107         return tick_switch_to_oneshot(hrtimer_interrupt);
 108 }
 109 #endif