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  */
  27 int tick_program_event(ktime_t expires, int force)
  28 {
  29         struct clock_event_device *dev = __this_cpu_read(tick_cpu_device.evtdev);
  30
  31         return clockevents_program_event(dev, expires, force);
  32 }
  33
  34 /**
  35  * tick_resume_onshot - resume oneshot mode
  36  */
  37 void tick_resume_oneshot(void)
  38 {
  39         struct clock_event_device *dev = __this_cpu_read(tick_cpu_device.evtdev);
  40
  41         clockevents_set_mode(dev, CLOCK_EVT_MODE_ONESHOT);
  42         clockevents_program_event(dev, ktime_get(), true);
  43 }
  44
  45 /**
  46  * tick_setup_oneshot - setup the event device for oneshot mode (hres or nohz)
  47  */
  48 void tick_setup_oneshot(struct clock_event_device *newdev,
  49                         void (*handler)(struct clock_event_device *),
  50                         ktime_t next_event)
  51 {
  52         newdev->event_handler = handler;
  53         clockevents_set_mode(newdev, CLOCK_EVT_MODE_ONESHOT);
  54         clockevents_program_event(newdev, next_event, true);
  55 }
  56
  57 /**
  58  * tick_switch_to_oneshot - switch to oneshot mode
  59  */
  60 int tick_switch_to_oneshot(void (*handler)(struct clock_event_device *))
  61 {
  62         struct tick_device *td = &__get_cpu_var(tick_cpu_device);
  63         struct clock_event_device *dev = td->evtdev;
  64
  65         if (!dev || !(dev->features & CLOCK_EVT_FEAT_ONESHOT) ||
  66                     !tick_device_is_functional(dev)) {
  67
  68                 printk(KERN_INFO "Clockevents: "
  69                        "could not switch to one-shot mode:");
  70                 if (!dev) {
  71                         printk(" no tick device\n");
  72                 } else {
  73                         if (!tick_device_is_functional(dev))
  74                                 printk(" %s is not functional.\n", dev->name);
  75                         else
  76                                 printk(" %s does not support one-shot mode.\n",
  77                                        dev->name);
  78                 }
  79                 return -EINVAL;
  80         }
  81
  82         td->mode = TICKDEV_MODE_ONESHOT;
  83         dev->event_handler = handler;
  84         clockevents_set_mode(dev, CLOCK_EVT_MODE_ONESHOT);
  85         tick_broadcast_switch_to_oneshot();
  86         return 0;
  87 }
  88
  89 /**
  90  * tick_check_oneshot_mode - check whether the system is in oneshot mode
  91  *
  92  * returns 1 when either nohz or highres are enabled. otherwise 0.
  93  */
  94 int tick_oneshot_mode_active(void)
  95 {
  96         unsigned long flags;
  97         int ret;
  98
  99         local_irq_save(flags);
 100         ret = __this_cpu_read(tick_cpu_device.mode) == TICKDEV_MODE_ONESHOT;
 101         local_irq_restore(flags);
 102
 103         return ret;
 104 }
 105
 106 #ifdef CONFIG_HIGH_RES_TIMERS
 107 /**
 108  * tick_init_highres - switch to high resolution mode
 109  *
 110  * Called with interrupts disabled.
 111  */
 112 int tick_init_highres(void)
 113 {
 114         return tick_switch_to_oneshot(hrtimer_interrupt);
 115 }
 116 #endif