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 */
23 int 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 */
50 void 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 */
61 void 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 */
73 int 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 */
106 int 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 */
124 int tick_init_highres(void)
125 {
126 return tick_switch_to_oneshot(hrtimer_interrupt);
127 }
128 #endif
129
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