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 */
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_oneshot - 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_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 */
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