LXR linux/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
  22 */
  23int 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_onshot - resume oneshot mode
  49 */
  50void 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 */
  61void 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 */
  73int 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_check_oneshot_mode - check whether the system is in oneshot mode
 103 *
 104 * returns 1 when either nohz or highres are enabled. otherwise 0.
 105 */
 106int 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 */
 124int tick_init_highres(void)
 125{
 126        return tick_switch_to_oneshot(hrtimer_interrupt);
 127}
 128#endif
 129