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 internal worker function
  27  */
  28 int tick_dev_program_event(struct clock_event_device *dev, ktime_t expires,
  29                            int force)
  30 {
  31         ktime_t now = ktime_get();
  32         int i;
  33
  34         for (i = 0;;) {
  35                 int ret = clockevents_program_event(dev, expires, now);
  36
  37                 if (!ret || !force)
  38                         return ret;
  39
  40                 /*
  41                  * We tried 2 times to program the device with the given
  42                  * min_delta_ns. If that's not working then we double it
  43                  * and emit a warning.
  44                  */
  45                 if (++i > 2) {
  46                         printk(KERN_WARNING "CE: __tick_program_event of %s is "
  47                                "stuck %llx %llx\n", dev->name ? dev->name : "?",
  48                                now.tv64, expires.tv64);
  49                         printk(KERN_WARNING
  50                                "CE: increasing min_delta_ns %ld to %ld nsec\n",
  51                                dev->min_delta_ns, dev->min_delta_ns << 1);
  52                         WARN_ON(1);
  53
  54                         /* Double the min. delta and try again */
  55                         if (!dev->min_delta_ns)
  56                                 dev->min_delta_ns = 5000;
  57                         else
  58                                 dev->min_delta_ns <<= 1;
  59                         i = 0;
  60                 }
  61
  62                 now = ktime_get();
  63                 expires = ktime_add_ns(now, dev->min_delta_ns);
  64         }
  65 }
  66
  67 /**
  68  * tick_program_event
  69  */
  70 int tick_program_event(ktime_t expires, int force)
  71 {
  72         struct clock_event_device *dev = __get_cpu_var(tick_cpu_device).evtdev;
  73
  74         return tick_dev_program_event(dev, expires, force);
  75 }
  76
  77 /**
  78  * tick_resume_onshot - resume oneshot mode
  79  */
  80 void tick_resume_oneshot(void)
  81 {
  82         struct tick_device *td = &__get_cpu_var(tick_cpu_device);
  83         struct clock_event_device *dev = td->evtdev;
  84
  85         clockevents_set_mode(dev, CLOCK_EVT_MODE_ONESHOT);
  86         tick_program_event(ktime_get(), 1);
  87 }
  88
  89 /**
  90  * tick_setup_oneshot - setup the event device for oneshot mode (hres or nohz)
  91  */
  92 void tick_setup_oneshot(struct clock_event_device *newdev,
  93                         void (*handler)(struct clock_event_device *),
  94                         ktime_t next_event)
  95 {
  96         newdev->event_handler = handler;
  97         clockevents_set_mode(newdev, CLOCK_EVT_MODE_ONESHOT);
  98         tick_dev_program_event(newdev, next_event, 1);
  99 }
 100
 101 /**
 102  * tick_switch_to_oneshot - switch to oneshot mode
 103  */
 104 int tick_switch_to_oneshot(void (*handler)(struct clock_event_device *))
 105 {
 106         struct tick_device *td = &__get_cpu_var(tick_cpu_device);
 107         struct clock_event_device *dev = td->evtdev;
 108
 109         if (!dev || !(dev->features & CLOCK_EVT_FEAT_ONESHOT) ||
 110                     !tick_device_is_functional(dev)) {
 111
 112                 printk(KERN_INFO "Clockevents: "
 113                        "could not switch to one-shot mode:");
 114                 if (!dev) {
 115                         printk(" no tick device\n");
 116                 } else {
 117                         if (!tick_device_is_functional(dev))
 118                                 printk(" %s is not functional.\n", dev->name);
 119                         else
 120                                 printk(" %s does not support one-shot mode.\n",
 121                                        dev->name);
 122                 }
 123                 return -EINVAL;
 124         }
 125
 126         td->mode = TICKDEV_MODE_ONESHOT;
 127         dev->event_handler = handler;
 128         clockevents_set_mode(dev, CLOCK_EVT_MODE_ONESHOT);
 129         tick_broadcast_switch_to_oneshot();
 130         return 0;
 131 }
 132
 133 #ifdef CONFIG_HIGH_RES_TIMERS
 134 /**
 135  * tick_init_highres - switch to high resolution mode
 136  *
 137  * Called with interrupts disabled.
 138  */
 139 int tick_init_highres(void)
 140 {
 141         return tick_switch_to_oneshot(hrtimer_interrupt);
 142 }
 143 #endif