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 int tick_dev_program_event(struct clock_event_device *dev, ktime_t expires,
29 int force)
30 {
31 ktime_t now = ktime_get();
32 int i;
33
34 for (i = 0;;) {
35 int ret = clockevents_program_event(dev, expires, now);
36
37 if (!ret || !force)
38 return ret;
39
40 /*
41 * We tried 2 times to program the device with the given
42 * min_delta_ns. If that's not working then we double it
43 * and emit a warning.
44 */
45 if (++i > 2) {
46 /* Increase the min. delta and try again */
47 if (!dev->min_delta_ns)
48 dev->min_delta_ns = 5000;
49 else
50 dev->min_delta_ns += dev->min_delta_ns >> 1;
51
52 printk(KERN_WARNING
53 "CE: %s increasing min_delta_ns to %lu nsec\n",
54 dev->name ? dev->name : "?",
55 dev->min_delta_ns << 1);
56
57 i = 0;
58 }
59
60 now = ktime_get();
61 expires = ktime_add_ns(now, dev->min_delta_ns);
62 }
63 }
64
65 /**
66 * tick_program_event
67 */
68 int tick_program_event(ktime_t expires, int force)
69 {
70 struct clock_event_device *dev = __get_cpu_var(tick_cpu_device).evtdev;
71
72 return tick_dev_program_event(dev, expires, force);
73 }
74
75 /**
76 * tick_resume_onshot - resume oneshot mode
77 */
78 void tick_resume_oneshot(void)
79 {
80 struct tick_device *td = &__get_cpu_var(tick_cpu_device);
81 struct clock_event_device *dev = td->evtdev;
82
83 clockevents_set_mode(dev, CLOCK_EVT_MODE_ONESHOT);
84 tick_program_event(ktime_get(), 1);
85 }
86
87 /**
88 * tick_setup_oneshot - setup the event device for oneshot mode (hres or nohz)
89 */
90 void tick_setup_oneshot(struct clock_event_device *newdev,
91 void (*handler)(struct clock_event_device *),
92 ktime_t next_event)
93 {
94 newdev->event_handler = handler;
95 clockevents_set_mode(newdev, CLOCK_EVT_MODE_ONESHOT);
96 tick_dev_program_event(newdev, next_event, 1);
97 }
98
99 /**
100 * tick_switch_to_oneshot - switch to oneshot mode
101 */
102 int tick_switch_to_oneshot(void (*handler)(struct clock_event_device *))
103 {
104 struct tick_device *td = &__get_cpu_var(tick_cpu_device);
105 struct clock_event_device *dev = td->evtdev;
106
107 if (!dev || !(dev->features & CLOCK_EVT_FEAT_ONESHOT) ||
108 !tick_device_is_functional(dev)) {
109
110 printk(KERN_INFO "Clockevents: "
111 "could not switch to one-shot mode:");
112 if (!dev) {
113 printk(" no tick device\n");
114 } else {
115 if (!tick_device_is_functional(dev))
116 printk(" %s is not functional.\n", dev->name);
117 else
118 printk(" %s does not support one-shot mode.\n",
119 dev->name);
120 }
121 return -EINVAL;
122 }
123
124 td->mode = TICKDEV_MODE_ONESHOT;
125 dev->event_handler = handler;
126 clockevents_set_mode(dev, CLOCK_EVT_MODE_ONESHOT);
127 tick_broadcast_switch_to_oneshot();
128 return 0;
129 }
130
131 /**
132 * tick_check_oneshot_mode - check whether the system is in oneshot mode
133 *
134 * returns 1 when either nohz or highres are enabled. otherwise 0.
135 */
136 int tick_oneshot_mode_active(void)
137 {
138 unsigned long flags;
139 int ret;
140
141 local_irq_save(flags);
142 ret = __get_cpu_var(tick_cpu_device).mode == TICKDEV_MODE_ONESHOT;
143 local_irq_restore(flags);
144
145 return ret;
146 }
147
148 #ifdef CONFIG_HIGH_RES_TIMERS
149 /**
150 * tick_init_highres - switch to high resolution mode
151 *
152 * Called with interrupts disabled.
153 */
154 int tick_init_highres(void)
155 {
156 return tick_switch_to_oneshot(hrtimer_interrupt);
157 }
158 #endif
159
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