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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 <[email protected]>
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