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, Linutronix GmbH, Thomas Gleixner <tglx@kernel.org>
  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 * @expires: the time at which the next timer event should occur
 23 * @force: flag to force reprograming even if the event time hasn't changed
 24 *
 25 * Return: 0 on success, negative error code on failure
 26 */
 27int 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_oneshot - resume oneshot mode
 53 */
 54void 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 * @newdev: Pointer to the clock event device to configure
 65 * @handler: Function to be called when the event device triggers an interrupt
 66 * @next_event: Initial expiry time for the next event (in ktime)
 67 *
 68 * Configures the specified clock event device for onshot mode,
 69 * assigns the given handler as its event callback, and programs
 70 * the device to trigger at the specified next event time.
 71 */
 72void tick_setup_oneshot(struct clock_event_device *newdev,
 73			void (*handler)(struct clock_event_device *),
 74			ktime_t next_event)
 75{
 76	newdev->event_handler = handler;
 77	clockevents_switch_state(newdev, CLOCK_EVT_STATE_ONESHOT);
 78	clockevents_program_event(newdev, next_event, true);
 79}
 80
 81/**
 82 * tick_switch_to_oneshot - switch to oneshot mode
 83 * @handler: function to call when an event occurs on the tick device
 84 *
 85 * Return: 0 on success, -EINVAL if the tick device is not present,
 86 *         not functional, or does not support oneshot mode.
 87 */
 88int tick_switch_to_oneshot(void (*handler)(struct clock_event_device *))
 89{
 90	struct tick_device *td = this_cpu_ptr(&tick_cpu_device);
 91	struct clock_event_device *dev = td->evtdev;
 92
 93	if (!dev || !(dev->features & CLOCK_EVT_FEAT_ONESHOT) ||
 94		    !tick_device_is_functional(dev)) {
 95
 96		pr_info("Clockevents: could not switch to one-shot mode:");
 97		if (!dev) {
 98			pr_cont(" no tick device\n");
 99		} else {
100			if (!tick_device_is_functional(dev))
101				pr_cont(" %s is not functional.\n", dev->name);
102			else
103				pr_cont(" %s does not support one-shot mode.\n",
104					dev->name);
105		}
106		return -EINVAL;
107	}
108
109	td->mode = TICKDEV_MODE_ONESHOT;
110	dev->event_handler = handler;
111	clockevents_switch_state(dev, CLOCK_EVT_STATE_ONESHOT);
112	tick_broadcast_switch_to_oneshot();
113	return 0;
114}
115
116/**
117 * tick_oneshot_mode_active - check whether the system is in oneshot mode
118 *
119 * Return: 1 when either nohz or highres are enabled, otherwise 0.
120 */
121int tick_oneshot_mode_active(void)
122{
123	unsigned long flags;
124	int ret;
125
126	local_irq_save(flags);
127	ret = __this_cpu_read(tick_cpu_device.mode) == TICKDEV_MODE_ONESHOT;
128	local_irq_restore(flags);
129
130	return ret;
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 * Return: 0 on success, -EINVAL if the tick device cannot switch
140 *         to oneshot/high-resolution mode.
141 */
142int tick_init_highres(void)
143{
144	return tick_switch_to_oneshot(hrtimer_interrupt);
145}
146#endif