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, state: 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, state: 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, state: CLOCK_EVT_STATE_ONESHOT);
55 clockevents_program_event(dev, expires: ktime_get(), force: 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(dev: newdev, state: CLOCK_EVT_STATE_ONESHOT);
67 clockevents_program_event(dev: newdev, expires: next_event, force: 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, state: 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(handler: hrtimer_interrupt);
127}
128#endif
129