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1/*
2 * linux/kernel/time/tick-oneshot.c
3 *
4 * This file contains functions which manage high resolution tick
5 * related events.
6 *
7 * Copyright(C) 2005-2006, Thomas Gleixner <tglx@linutronix.de>
8 * Copyright(C) 2005-2007, Red Hat, Inc., Ingo Molnar
9 * Copyright(C) 2006-2007, Timesys Corp., Thomas Gleixner
10 *
11 * This code is licenced under the GPL version 2. For details see
12 * kernel-base/COPYING.
13 */
14#include <linux/cpu.h>
15#include <linux/err.h>
16#include <linux/hrtimer.h>
17#include <linux/interrupt.h>
18#include <linux/percpu.h>
19#include <linux/profile.h>
20#include <linux/sched.h>
21
22#include "tick-internal.h"
23
24/**
25 * tick_program_event
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 return clockevents_program_event(dev, expires, force);
32}
33
34/**
35 * tick_resume_onshot - resume oneshot mode
36 */
37void tick_resume_oneshot(void)
38{
39 struct clock_event_device *dev = __this_cpu_read(tick_cpu_device.evtdev);
40
41 clockevents_set_mode(dev, CLOCK_EVT_MODE_ONESHOT);
42 clockevents_program_event(dev, ktime_get(), true);
43}
44
45/**
46 * tick_setup_oneshot - setup the event device for oneshot mode (hres or nohz)
47 */
48void tick_setup_oneshot(struct clock_event_device *newdev,
49 void (*handler)(struct clock_event_device *),
50 ktime_t next_event)
51{
52 newdev->event_handler = handler;
53 clockevents_set_mode(newdev, CLOCK_EVT_MODE_ONESHOT);
54 clockevents_program_event(newdev, next_event, true);
55}
56
57/**
58 * tick_switch_to_oneshot - switch to oneshot mode
59 */
60int tick_switch_to_oneshot(void (*handler)(struct clock_event_device *))
61{
62 struct tick_device *td = &__get_cpu_var(tick_cpu_device);
63 struct clock_event_device *dev = td->evtdev;
64
65 if (!dev || !(dev->features & CLOCK_EVT_FEAT_ONESHOT) ||
66 !tick_device_is_functional(dev)) {
67
68 printk(KERN_INFO "Clockevents: "
69 "could not switch to one-shot mode:");
70 if (!dev) {
71 printk(" no tick device\n");
72 } else {
73 if (!tick_device_is_functional(dev))
74 printk(" %s is not functional.\n", dev->name);
75 else
76 printk(" %s does not support one-shot mode.\n",
77 dev->name);
78 }
79 return -EINVAL;
80 }
81
82 td->mode = TICKDEV_MODE_ONESHOT;
83 dev->event_handler = handler;
84 clockevents_set_mode(dev, CLOCK_EVT_MODE_ONESHOT);
85 tick_broadcast_switch_to_oneshot();
86 return 0;
87}
88
89/**
90 * tick_check_oneshot_mode - check whether the system is in oneshot mode
91 *
92 * returns 1 when either nohz or highres are enabled. otherwise 0.
93 */
94int tick_oneshot_mode_active(void)
95{
96 unsigned long flags;
97 int ret;
98
99 local_irq_save(flags);
100 ret = __this_cpu_read(tick_cpu_device.mode) == TICKDEV_MODE_ONESHOT;
101 local_irq_restore(flags);
102
103 return ret;
104}
105
106#ifdef CONFIG_HIGH_RES_TIMERS
107/**
108 * tick_init_highres - switch to high resolution mode
109 *
110 * Called with interrupts disabled.
111 */
112int tick_init_highres(void)
113{
114 return tick_switch_to_oneshot(hrtimer_interrupt);
115}
116#endif
1/*
2 * linux/kernel/time/tick-oneshot.c
3 *
4 * This file contains functions which manage high resolution tick
5 * related events.
6 *
7 * Copyright(C) 2005-2006, Thomas Gleixner <tglx@linutronix.de>
8 * Copyright(C) 2005-2007, Red Hat, Inc., Ingo Molnar
9 * Copyright(C) 2006-2007, Timesys Corp., Thomas Gleixner
10 *
11 * This code is licenced under the GPL version 2. For details see
12 * kernel-base/COPYING.
13 */
14#include <linux/cpu.h>
15#include <linux/err.h>
16#include <linux/hrtimer.h>
17#include <linux/interrupt.h>
18#include <linux/percpu.h>
19#include <linux/profile.h>
20#include <linux/sched.h>
21
22#include "tick-internal.h"
23
24/* Limit min_delta to a jiffie */
25#define MIN_DELTA_LIMIT (NSEC_PER_SEC / HZ)
26
27static int tick_increase_min_delta(struct clock_event_device *dev)
28{
29 /* Nothing to do if we already reached the limit */
30 if (dev->min_delta_ns >= MIN_DELTA_LIMIT)
31 return -ETIME;
32
33 if (dev->min_delta_ns < 5000)
34 dev->min_delta_ns = 5000;
35 else
36 dev->min_delta_ns += dev->min_delta_ns >> 1;
37
38 if (dev->min_delta_ns > MIN_DELTA_LIMIT)
39 dev->min_delta_ns = MIN_DELTA_LIMIT;
40
41 printk(KERN_WARNING "CE: %s increased min_delta_ns to %llu nsec\n",
42 dev->name ? dev->name : "?",
43 (unsigned long long) dev->min_delta_ns);
44 return 0;
45}
46
47/**
48 * tick_program_event internal worker function
49 */
50int tick_dev_program_event(struct clock_event_device *dev, ktime_t expires,
51 int force)
52{
53 ktime_t now = ktime_get();
54 int i;
55
56 for (i = 0;;) {
57 int ret = clockevents_program_event(dev, expires, now);
58
59 if (!ret || !force)
60 return ret;
61
62 dev->retries++;
63 /*
64 * We tried 3 times to program the device with the given
65 * min_delta_ns. If that's not working then we increase it
66 * and emit a warning.
67 */
68 if (++i > 2) {
69 /* Increase the min. delta and try again */
70 if (tick_increase_min_delta(dev)) {
71 /*
72 * Get out of the loop if min_delta_ns
73 * hit the limit already. That's
74 * better than staying here forever.
75 *
76 * We clear next_event so we have a
77 * chance that the box survives.
78 */
79 printk(KERN_WARNING
80 "CE: Reprogramming failure. Giving up\n");
81 dev->next_event.tv64 = KTIME_MAX;
82 return -ETIME;
83 }
84 i = 0;
85 }
86
87 now = ktime_get();
88 expires = ktime_add_ns(now, dev->min_delta_ns);
89 }
90}
91
92/**
93 * tick_program_event
94 */
95int tick_program_event(ktime_t expires, int force)
96{
97 struct clock_event_device *dev = __this_cpu_read(tick_cpu_device.evtdev);
98
99 return tick_dev_program_event(dev, expires, force);
100}
101
102/**
103 * tick_resume_onshot - resume oneshot mode
104 */
105void tick_resume_oneshot(void)
106{
107 struct tick_device *td = &__get_cpu_var(tick_cpu_device);
108 struct clock_event_device *dev = td->evtdev;
109
110 clockevents_set_mode(dev, CLOCK_EVT_MODE_ONESHOT);
111 tick_program_event(ktime_get(), 1);
112}
113
114/**
115 * tick_setup_oneshot - setup the event device for oneshot mode (hres or nohz)
116 */
117void tick_setup_oneshot(struct clock_event_device *newdev,
118 void (*handler)(struct clock_event_device *),
119 ktime_t next_event)
120{
121 newdev->event_handler = handler;
122 clockevents_set_mode(newdev, CLOCK_EVT_MODE_ONESHOT);
123 tick_dev_program_event(newdev, next_event, 1);
124}
125
126/**
127 * tick_switch_to_oneshot - switch to oneshot mode
128 */
129int tick_switch_to_oneshot(void (*handler)(struct clock_event_device *))
130{
131 struct tick_device *td = &__get_cpu_var(tick_cpu_device);
132 struct clock_event_device *dev = td->evtdev;
133
134 if (!dev || !(dev->features & CLOCK_EVT_FEAT_ONESHOT) ||
135 !tick_device_is_functional(dev)) {
136
137 printk(KERN_INFO "Clockevents: "
138 "could not switch to one-shot mode:");
139 if (!dev) {
140 printk(" no tick device\n");
141 } else {
142 if (!tick_device_is_functional(dev))
143 printk(" %s is not functional.\n", dev->name);
144 else
145 printk(" %s does not support one-shot mode.\n",
146 dev->name);
147 }
148 return -EINVAL;
149 }
150
151 td->mode = TICKDEV_MODE_ONESHOT;
152 dev->event_handler = handler;
153 clockevents_set_mode(dev, CLOCK_EVT_MODE_ONESHOT);
154 tick_broadcast_switch_to_oneshot();
155 return 0;
156}
157
158/**
159 * tick_check_oneshot_mode - check whether the system is in oneshot mode
160 *
161 * returns 1 when either nohz or highres are enabled. otherwise 0.
162 */
163int tick_oneshot_mode_active(void)
164{
165 unsigned long flags;
166 int ret;
167
168 local_irq_save(flags);
169 ret = __this_cpu_read(tick_cpu_device.mode) == TICKDEV_MODE_ONESHOT;
170 local_irq_restore(flags);
171
172 return ret;
173}
174
175#ifdef CONFIG_HIGH_RES_TIMERS
176/**
177 * tick_init_highres - switch to high resolution mode
178 *
179 * Called with interrupts disabled.
180 */
181int tick_init_highres(void)
182{
183 return tick_switch_to_oneshot(hrtimer_interrupt);
184}
185#endif