2 * linux/kernel/time/tick-common.c
4 * This file contains the base functions to manage periodic 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>
21 #include <linux/tick.h>
23 #include <asm/irq_regs.h>
25 #include "tick-internal.h"
30 DEFINE_PER_CPU(struct tick_device, tick_cpu_device);
32 * Tick next event: keeps track of the tick time
34 ktime_t tick_next_period;
36 int tick_do_timer_cpu __read_mostly = TICK_DO_TIMER_BOOT;
37 DEFINE_SPINLOCK(tick_device_lock);
40 * Debugging: see timer_list.c
42 struct tick_device *tick_get_device(int cpu)
44 return &per_cpu(tick_cpu_device, cpu);
48 * tick_is_oneshot_available - check for a oneshot capable event device
50 int tick_is_oneshot_available(void)
52 struct clock_event_device *dev = __get_cpu_var(tick_cpu_device).evtdev;
54 return dev && (dev->features & CLOCK_EVT_FEAT_ONESHOT);
60 static void tick_periodic(int cpu)
62 if (tick_do_timer_cpu == cpu) {
63 write_seqlock(&xtime_lock);
65 /* Keep track of the next tick event */
66 tick_next_period = ktime_add(tick_next_period, tick_period);
69 write_sequnlock(&xtime_lock);
72 update_process_times(user_mode(get_irq_regs()));
73 profile_tick(CPU_PROFILING);
77 * Event handler for periodic ticks
79 void tick_handle_periodic(struct clock_event_device *dev)
81 int cpu = smp_processor_id();
86 if (dev->mode != CLOCK_EVT_MODE_ONESHOT)
89 * Setup the next period for devices, which do not have
92 next = ktime_add(dev->next_event, tick_period);
94 if (!clockevents_program_event(dev, next, ktime_get()))
97 * Have to be careful here. If we're in oneshot mode,
98 * before we call tick_periodic() in a loop, we need
99 * to be sure we're using a real hardware clocksource.
100 * Otherwise we could get trapped in an infinite
101 * loop, as the tick_periodic() increments jiffies,
102 * when then will increment time, posibly causing
103 * the loop to trigger again and again.
105 if (timekeeping_valid_for_hres())
107 next = ktime_add(next, tick_period);
112 * Setup the device for a periodic tick
114 void tick_setup_periodic(struct clock_event_device *dev, int broadcast)
116 tick_set_periodic_handler(dev, broadcast);
118 /* Broadcast setup ? */
119 if (!tick_device_is_functional(dev))
122 if ((dev->features & CLOCK_EVT_FEAT_PERIODIC) &&
123 !tick_broadcast_oneshot_active()) {
124 clockevents_set_mode(dev, CLOCK_EVT_MODE_PERIODIC);
130 seq = read_seqbegin(&xtime_lock);
131 next = tick_next_period;
132 } while (read_seqretry(&xtime_lock, seq));
134 clockevents_set_mode(dev, CLOCK_EVT_MODE_ONESHOT);
137 if (!clockevents_program_event(dev, next, ktime_get()))
139 next = ktime_add(next, tick_period);
145 * Setup the tick device
147 static void tick_setup_device(struct tick_device *td,
148 struct clock_event_device *newdev, int cpu,
149 const struct cpumask *cpumask)
152 void (*handler)(struct clock_event_device *) = NULL;
155 * First device setup ?
159 * If no cpu took the do_timer update, assign it to
162 if (tick_do_timer_cpu == TICK_DO_TIMER_BOOT) {
163 tick_do_timer_cpu = cpu;
164 tick_next_period = ktime_get();
165 tick_period = ktime_set(0, NSEC_PER_SEC / HZ);
169 * Startup in periodic mode first.
171 td->mode = TICKDEV_MODE_PERIODIC;
173 handler = td->evtdev->event_handler;
174 next_event = td->evtdev->next_event;
175 td->evtdev->event_handler = clockevents_handle_noop;
181 * When the device is not per cpu, pin the interrupt to the
184 if (!cpumask_equal(newdev->cpumask, cpumask))
185 irq_set_affinity(newdev->irq, cpumask);
188 * When global broadcasting is active, check if the current
189 * device is registered as a placeholder for broadcast mode.
190 * This allows us to handle this x86 misfeature in a generic
193 if (tick_device_uses_broadcast(newdev, cpu))
196 if (td->mode == TICKDEV_MODE_PERIODIC)
197 tick_setup_periodic(newdev, 0);
199 tick_setup_oneshot(newdev, handler, next_event);
203 * Check, if the new registered device should be used.
205 static int tick_check_new_device(struct clock_event_device *newdev)
207 struct clock_event_device *curdev;
208 struct tick_device *td;
209 int cpu, ret = NOTIFY_OK;
212 spin_lock_irqsave(&tick_device_lock, flags);
214 cpu = smp_processor_id();
215 if (!cpumask_test_cpu(cpu, newdev->cpumask))
218 td = &per_cpu(tick_cpu_device, cpu);
221 /* cpu local device ? */
222 if (!cpumask_equal(newdev->cpumask, cpumask_of(cpu))) {
225 * If the cpu affinity of the device interrupt can not
228 if (!irq_can_set_affinity(newdev->irq))
232 * If we have a cpu local device already, do not replace it
233 * by a non cpu local device
235 if (curdev && cpumask_equal(curdev->cpumask, cpumask_of(cpu)))
240 * If we have an active device, then check the rating and the oneshot
245 * Prefer one shot capable devices !
247 if ((curdev->features & CLOCK_EVT_FEAT_ONESHOT) &&
248 !(newdev->features & CLOCK_EVT_FEAT_ONESHOT))
253 if (curdev->rating >= newdev->rating)
258 * Replace the eventually existing device by the new
259 * device. If the current device is the broadcast device, do
260 * not give it back to the clockevents layer !
262 if (tick_is_broadcast_device(curdev)) {
263 clockevents_shutdown(curdev);
266 clockevents_exchange_device(curdev, newdev);
267 tick_setup_device(td, newdev, cpu, cpumask_of(cpu));
268 if (newdev->features & CLOCK_EVT_FEAT_ONESHOT)
269 tick_oneshot_notify();
271 spin_unlock_irqrestore(&tick_device_lock, flags);
276 * Can the new device be used as a broadcast device ?
278 if (tick_check_broadcast_device(newdev))
281 spin_unlock_irqrestore(&tick_device_lock, flags);
287 * Transfer the do_timer job away from a dying cpu.
289 * Called with interrupts disabled.
291 static void tick_handover_do_timer(int *cpup)
293 if (*cpup == tick_do_timer_cpu) {
294 int cpu = cpumask_first(cpu_online_mask);
296 tick_do_timer_cpu = (cpu < nr_cpu_ids) ? cpu :
302 * Shutdown an event device on a given cpu:
304 * This is called on a life CPU, when a CPU is dead. So we cannot
305 * access the hardware device itself.
306 * We just set the mode and remove it from the lists.
308 static void tick_shutdown(unsigned int *cpup)
310 struct tick_device *td = &per_cpu(tick_cpu_device, *cpup);
311 struct clock_event_device *dev = td->evtdev;
314 spin_lock_irqsave(&tick_device_lock, flags);
315 td->mode = TICKDEV_MODE_PERIODIC;
318 * Prevent that the clock events layer tries to call
319 * the set mode function!
321 dev->mode = CLOCK_EVT_MODE_UNUSED;
322 clockevents_exchange_device(dev, NULL);
325 spin_unlock_irqrestore(&tick_device_lock, flags);
328 static void tick_suspend(void)
330 struct tick_device *td = &__get_cpu_var(tick_cpu_device);
333 spin_lock_irqsave(&tick_device_lock, flags);
334 clockevents_shutdown(td->evtdev);
335 spin_unlock_irqrestore(&tick_device_lock, flags);
338 static void tick_resume(void)
340 struct tick_device *td = &__get_cpu_var(tick_cpu_device);
342 int broadcast = tick_resume_broadcast();
344 spin_lock_irqsave(&tick_device_lock, flags);
345 clockevents_set_mode(td->evtdev, CLOCK_EVT_MODE_RESUME);
348 if (td->mode == TICKDEV_MODE_PERIODIC)
349 tick_setup_periodic(td->evtdev, 0);
351 tick_resume_oneshot();
353 spin_unlock_irqrestore(&tick_device_lock, flags);
357 * Notification about clock event devices
359 static int tick_notify(struct notifier_block *nb, unsigned long reason,
364 case CLOCK_EVT_NOTIFY_ADD:
365 return tick_check_new_device(dev);
367 case CLOCK_EVT_NOTIFY_BROADCAST_ON:
368 case CLOCK_EVT_NOTIFY_BROADCAST_OFF:
369 case CLOCK_EVT_NOTIFY_BROADCAST_FORCE:
370 tick_broadcast_on_off(reason, dev);
373 case CLOCK_EVT_NOTIFY_BROADCAST_ENTER:
374 case CLOCK_EVT_NOTIFY_BROADCAST_EXIT:
375 tick_broadcast_oneshot_control(reason);
378 case CLOCK_EVT_NOTIFY_CPU_DYING:
379 tick_handover_do_timer(dev);
382 case CLOCK_EVT_NOTIFY_CPU_DEAD:
383 tick_shutdown_broadcast_oneshot(dev);
384 tick_shutdown_broadcast(dev);
388 case CLOCK_EVT_NOTIFY_SUSPEND:
390 tick_suspend_broadcast();
393 case CLOCK_EVT_NOTIFY_RESUME:
404 static struct notifier_block tick_notifier = {
405 .notifier_call = tick_notify,
409 * tick_init - initialize the tick control
411 * Register the notifier with the clockevents framework
413 void __init tick_init(void)
415 clockevents_register_notifier(&tick_notifier);