kernel/time/tick-oneshot.c

   1 // SPDX-License-Identifier: GPL-2.0
   2 /*
   3  * This file contains functions which manage high resolution tick
   4  * related events.
   5  *
   6  * Copyright(C) 2005-2006, Thomas Gleixner <tglx@linutronix.de>
   7  * Copyright(C) 2005-2007, Red Hat, Inc., Ingo Molnar
   8  * Copyright(C) 2006-2007, Timesys Corp., Thomas Gleixner
   9  */
  10 #include <linux/cpu.h>
  11 #include <linux/err.h>
  12 #include <linux/hrtimer.h>
  13 #include <linux/interrupt.h>
  14 #include <linux/percpu.h>
  15 #include <linux/profile.h>
  16 #include <linux/sched.h>
  17
  18 #include "tick-internal.h"
  19
  20 /**
  21  * tick_program_event - program the CPU local timer device for the next event
  22  */
  23 int tick_program_event(ktime_t expires, int force)
  24 {
  25         struct clock_event_device *dev = __this_cpu_read(tick_cpu_device.evtdev);
  26
  27         if (unlikely(expires == KTIME_MAX)) {
  28                 /*
  29                  * We don't need the clock event device any more, stop it.
  30                  */
  31                 clockevents_switch_state(dev, CLOCK_EVT_STATE_ONESHOT_STOPPED);
  32                 dev->next_event = KTIME_MAX;
  33                 return 0;
  34         }
  35
  36         if (unlikely(clockevent_state_oneshot_stopped(dev))) {
  37                 /*
  38                  * We need the clock event again, configure it in ONESHOT mode
  39                  * before using it.
  40                  */
  41                 clockevents_switch_state(dev, CLOCK_EVT_STATE_ONESHOT);
  42         }
  43
  44         return clockevents_program_event(dev, expires, force);
  45 }
  46
  47 /**
  48  * tick_resume_oneshot - resume oneshot mode
  49  */
  50 void tick_resume_oneshot(void)
  51 {
  52         struct clock_event_device *dev = __this_cpu_read(tick_cpu_device.evtdev);
  53
  54         clockevents_switch_state(dev, CLOCK_EVT_STATE_ONESHOT);
  55         clockevents_program_event(dev, ktime_get(), true);
  56 }
  57
  58 /**
  59  * tick_setup_oneshot - setup the event device for oneshot mode (hres or nohz)
  60  */
  61 void tick_setup_oneshot(struct clock_event_device *newdev,
  62                         void (*handler)(struct clock_event_device *),
  63                         ktime_t next_event)
  64 {
  65         newdev->event_handler = handler;
  66         clockevents_switch_state(newdev, CLOCK_EVT_STATE_ONESHOT);
  67         clockevents_program_event(newdev, next_event, true);
  68 }
  69
  70 /**
  71  * tick_switch_to_oneshot - switch to oneshot mode
  72  */
  73 int tick_switch_to_oneshot(void (*handler)(struct clock_event_device *))
  74 {
  75         struct tick_device *td = this_cpu_ptr(&tick_cpu_device);
  76         struct clock_event_device *dev = td->evtdev;
  77
  78         if (!dev || !(dev->features & CLOCK_EVT_FEAT_ONESHOT) ||
  79                     !tick_device_is_functional(dev)) {
  80
  81                 pr_info("Clockevents: could not switch to one-shot mode:");
  82                 if (!dev) {
  83                         pr_cont(" no tick device\n");
  84                 } else {
  85                         if (!tick_device_is_functional(dev))
  86                                 pr_cont(" %s is not functional.\n", dev->name);
  87                         else
  88                                 pr_cont(" %s does not support one-shot mode.\n",
  89                                         dev->name);
  90                 }
  91                 return -EINVAL;
  92         }
  93
  94         td->mode = TICKDEV_MODE_ONESHOT;
  95         dev->event_handler = handler;
  96         clockevents_switch_state(dev, CLOCK_EVT_STATE_ONESHOT);
  97         tick_broadcast_switch_to_oneshot();
  98         return 0;
  99 }
 100
 101 /**
 102  * tick_oneshot_mode_active - check whether the system is in oneshot mode
 103  *
 104  * returns 1 when either nohz or highres are enabled. otherwise 0.
 105  */
 106 int tick_oneshot_mode_active(void)
 107 {
 108         unsigned long flags;
 109         int ret;
 110
 111         local_irq_save(flags);
 112         ret = __this_cpu_read(tick_cpu_device.mode) == TICKDEV_MODE_ONESHOT;
 113         local_irq_restore(flags);
 114
 115         return ret;
 116 }
 117
 118 #ifdef CONFIG_HIGH_RES_TIMERS
 119 /**
 120  * tick_init_highres - switch to high resolution mode
 121  *
 122  * Called with interrupts disabled.
 123  */
 124 int tick_init_highres(void)
 125 {
 126         return tick_switch_to_oneshot(hrtimer_interrupt);
 127 }
 128 #endif