clockevents: enforce reprogram in oneshot setup
[linux-2.6.git] / kernel / time / tick-oneshot.c
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 #include <linux/tick.h>
22
23 #include "tick-internal.h"
24
25 /**
26  * tick_program_event internal worker function
27  */
28 static int __tick_program_event(struct clock_event_device *dev,
29                                 ktime_t expires, int force)
30 {
31         ktime_t now = ktime_get();
32
33         while (1) {
34                 int ret = clockevents_program_event(dev, expires, now);
35
36                 if (!ret || !force)
37                         return ret;
38                 now = ktime_get();
39                 expires = ktime_add(now, ktime_set(0, dev->min_delta_ns));
40         }
41 }
42
43 /**
44  * tick_program_event
45  */
46 int tick_program_event(ktime_t expires, int force)
47 {
48         struct clock_event_device *dev = __get_cpu_var(tick_cpu_device).evtdev;
49
50         return __tick_program_event(dev, expires, force);
51 }
52
53 /**
54  * tick_resume_onshot - resume oneshot mode
55  */
56 void tick_resume_oneshot(void)
57 {
58         struct tick_device *td = &__get_cpu_var(tick_cpu_device);
59         struct clock_event_device *dev = td->evtdev;
60
61         clockevents_set_mode(dev, CLOCK_EVT_MODE_ONESHOT);
62         tick_program_event(ktime_get(), 1);
63 }
64
65 /**
66  * tick_setup_oneshot - setup the event device for oneshot mode (hres or nohz)
67  */
68 void tick_setup_oneshot(struct clock_event_device *newdev,
69                         void (*handler)(struct clock_event_device *),
70                         ktime_t next_event)
71 {
72         newdev->event_handler = handler;
73         clockevents_set_mode(newdev, CLOCK_EVT_MODE_ONESHOT);
74         __tick_program_event(newdev, next_event, 1);
75 }
76
77 /**
78  * tick_switch_to_oneshot - switch to oneshot mode
79  */
80 int tick_switch_to_oneshot(void (*handler)(struct clock_event_device *))
81 {
82         struct tick_device *td = &__get_cpu_var(tick_cpu_device);
83         struct clock_event_device *dev = td->evtdev;
84
85         if (!dev || !(dev->features & CLOCK_EVT_FEAT_ONESHOT) ||
86                     !tick_device_is_functional(dev)) {
87
88                 printk(KERN_INFO "Clockevents: "
89                        "could not switch to one-shot mode:");
90                 if (!dev) {
91                         printk(" no tick device\n");
92                 } else {
93                         if (!tick_device_is_functional(dev))
94                                 printk(" %s is not functional.\n", dev->name);
95                         else
96                                 printk(" %s does not support one-shot mode.\n",
97                                        dev->name);
98                 }
99                 return -EINVAL;
100         }
101
102         td->mode = TICKDEV_MODE_ONESHOT;
103         dev->event_handler = handler;
104         clockevents_set_mode(dev, CLOCK_EVT_MODE_ONESHOT);
105         tick_broadcast_switch_to_oneshot();
106         return 0;
107 }
108
109 #ifdef CONFIG_HIGH_RES_TIMERS
110 /**
111  * tick_init_highres - switch to high resolution mode
112  *
113  * Called with interrupts disabled.
114  */
115 int tick_init_highres(void)
116 {
117         return tick_switch_to_oneshot(hrtimer_interrupt);
118 }
119 #endif