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         if (unlikely(expires == 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                 dev->next_event = KTIME_MAX;
  37                 return 0;
  38         }
  39
  40         if (unlikely(clockevent_state_oneshot_stopped(dev))) {
  41                 /*
  42                  * We need the clock event again, configure it in ONESHOT mode
  43                  * before using it.
  44                  */
  45                 clockevents_switch_state(dev, CLOCK_EVT_STATE_ONESHOT);
  46         }
  47
  48         return clockevents_program_event(dev, expires, force);
  49 }
  50
  51 /**
  52  * tick_resume_onshot - resume oneshot mode
  53  */
  54 void tick_resume_oneshot(void)
  55 {
  56         struct clock_event_device *dev = __this_cpu_read(tick_cpu_device.evtdev);
  57
  58         clockevents_switch_state(dev, CLOCK_EVT_STATE_ONESHOT);
  59         clockevents_program_event(dev, ktime_get(), true);
  60 }
  61
  62 /**
  63  * tick_setup_oneshot - setup the event device for oneshot mode (hres or nohz)
  64  */
  65 void tick_setup_oneshot(struct clock_event_device *newdev,
  66                         void (*handler)(struct clock_event_device *),
  67                         ktime_t next_event)
  68 {
  69         newdev->event_handler = handler;
  70         clockevents_switch_state(newdev, CLOCK_EVT_STATE_ONESHOT);
  71         clockevents_program_event(newdev, next_event, true);
  72 }
  73
  74 /**
  75  * tick_switch_to_oneshot - switch to oneshot mode
  76  */
  77 int tick_switch_to_oneshot(void (*handler)(struct clock_event_device *))
  78 {
  79         struct tick_device *td = this_cpu_ptr(&tick_cpu_device);
  80         struct clock_event_device *dev = td->evtdev;
  81
  82         if (!dev || !(dev->features & CLOCK_EVT_FEAT_ONESHOT) ||
  83                     !tick_device_is_functional(dev)) {
  84
  85                 pr_info("Clockevents: could not switch to one-shot mode:");
  86                 if (!dev) {
  87                         pr_cont(" no tick device\n");
  88                 } else {
  89                         if (!tick_device_is_functional(dev))
  90                                 pr_cont(" %s is not functional.\n", dev->name);
  91                         else
  92                                 pr_cont(" %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  */
 110 int 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  */
 128 int tick_init_highres(void)
 129 {
 130         return tick_switch_to_oneshot(hrtimer_interrupt);
 131 }
 132 #endif