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  */
tick_program_event(ktime_t expires,int force)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  */
tick_resume_oneshot(void)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  */
tick_setup_oneshot(struct clock_event_device * newdev,void (* handler)(struct clock_event_device *),ktime_t next_event)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  */
tick_switch_to_oneshot(void (* handler)(struct clock_event_device *))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  */
tick_oneshot_mode_active(void)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  */
tick_init_highres(void)124 int tick_init_highres(void)
125 {
126 	return tick_switch_to_oneshot(hrtimer_interrupt);
127 }
128 #endif
129