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git.proxmox.com Git - mirror_ubuntu-artful-kernel.git/blob - kernel/time/tick-oneshot.c
2 * linux/kernel/time/tick-oneshot.c
4 * This file contains functions which manage high resolution tick
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
11 * This code is licenced under the GPL version 2. For details see
12 * kernel-base/COPYING.
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>
22 #include "tick-internal.h"
24 /* Limit min_delta to a jiffie */
25 #define MIN_DELTA_LIMIT (NSEC_PER_SEC / HZ)
27 static int tick_increase_min_delta(struct clock_event_device
*dev
)
29 /* Nothing to do if we already reached the limit */
30 if (dev
->min_delta_ns
>= MIN_DELTA_LIMIT
)
33 if (dev
->min_delta_ns
< 5000)
34 dev
->min_delta_ns
= 5000;
36 dev
->min_delta_ns
+= dev
->min_delta_ns
>> 1;
38 if (dev
->min_delta_ns
> MIN_DELTA_LIMIT
)
39 dev
->min_delta_ns
= MIN_DELTA_LIMIT
;
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
);
48 * tick_program_event internal worker function
50 int tick_dev_program_event(struct clock_event_device
*dev
, ktime_t expires
,
53 ktime_t now
= ktime_get();
57 int ret
= clockevents_program_event(dev
, expires
, now
);
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
69 /* Increase the min. delta and try again */
70 if (tick_increase_min_delta(dev
)) {
72 * Get out of the loop if min_delta_ns
73 * hit the limit already. That's
74 * better than staying here forever.
76 * We clear next_event so we have a
77 * chance that the box survives.
80 "CE: Reprogramming failure. Giving up\n");
81 dev
->next_event
.tv64
= KTIME_MAX
;
88 expires
= ktime_add_ns(now
, dev
->min_delta_ns
);
95 int tick_program_event(ktime_t expires
, int force
)
97 struct clock_event_device
*dev
= __this_cpu_read(tick_cpu_device
.evtdev
);
99 return tick_dev_program_event(dev
, expires
, force
);
103 * tick_resume_onshot - resume oneshot mode
105 void tick_resume_oneshot(void)
107 struct tick_device
*td
= &__get_cpu_var(tick_cpu_device
);
108 struct clock_event_device
*dev
= td
->evtdev
;
110 clockevents_set_mode(dev
, CLOCK_EVT_MODE_ONESHOT
);
111 tick_program_event(ktime_get(), 1);
115 * tick_setup_oneshot - setup the event device for oneshot mode (hres or nohz)
117 void tick_setup_oneshot(struct clock_event_device
*newdev
,
118 void (*handler
)(struct clock_event_device
*),
121 newdev
->event_handler
= handler
;
122 clockevents_set_mode(newdev
, CLOCK_EVT_MODE_ONESHOT
);
123 tick_dev_program_event(newdev
, next_event
, 1);
127 * tick_switch_to_oneshot - switch to oneshot mode
129 int tick_switch_to_oneshot(void (*handler
)(struct clock_event_device
*))
131 struct tick_device
*td
= &__get_cpu_var(tick_cpu_device
);
132 struct clock_event_device
*dev
= td
->evtdev
;
134 if (!dev
|| !(dev
->features
& CLOCK_EVT_FEAT_ONESHOT
) ||
135 !tick_device_is_functional(dev
)) {
137 printk(KERN_INFO
"Clockevents: "
138 "could not switch to one-shot mode:");
140 printk(" no tick device\n");
142 if (!tick_device_is_functional(dev
))
143 printk(" %s is not functional.\n", dev
->name
);
145 printk(" %s does not support one-shot mode.\n",
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();
159 * tick_check_oneshot_mode - check whether the system is in oneshot mode
161 * returns 1 when either nohz or highres are enabled. otherwise 0.
163 int tick_oneshot_mode_active(void)
168 local_irq_save(flags
);
169 ret
= __this_cpu_read(tick_cpu_device
.mode
) == TICKDEV_MODE_ONESHOT
;
170 local_irq_restore(flags
);
175 #ifdef CONFIG_HIGH_RES_TIMERS
177 * tick_init_highres - switch to high resolution mode
179 * Called with interrupts disabled.
181 int tick_init_highres(void)
183 return tick_switch_to_oneshot(hrtimer_interrupt
);