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>
22 #include <asm/irq_regs.h>
24 #include "tick-internal.h"
29 DEFINE_PER_CPU(struct tick_device, tick_cpu_device);
31 * Tick next event: keeps track of the tick time
33 ktime_t tick_next_period;
35 int tick_do_timer_cpu __read_mostly = TICK_DO_TIMER_BOOT;
38 * Debugging: see timer_list.c
40 struct tick_device *tick_get_device(int cpu)
42 return &per_cpu(tick_cpu_device, cpu);
46 * tick_is_oneshot_available - check for a oneshot capable event device
48 int tick_is_oneshot_available(void)
50 struct clock_event_device *dev = __this_cpu_read(tick_cpu_device.evtdev);
52 if (!dev || !(dev->features & CLOCK_EVT_FEAT_ONESHOT))
54 if (!(dev->features & CLOCK_EVT_FEAT_C3STOP))
56 return tick_broadcast_oneshot_available();
62 static void tick_periodic(int cpu)
64 if (tick_do_timer_cpu == cpu) {
65 write_seqlock(&jiffies_lock);
67 /* Keep track of the next tick event */
68 tick_next_period = ktime_add(tick_next_period, tick_period);
71 write_sequnlock(&jiffies_lock);
74 update_process_times(user_mode(get_irq_regs()));
75 profile_tick(CPU_PROFILING);
79 * Event handler for periodic ticks
81 void tick_handle_periodic(struct clock_event_device *dev)
83 int cpu = smp_processor_id();
88 if (dev->mode != CLOCK_EVT_MODE_ONESHOT)
91 * Setup the next period for devices, which do not have
94 next = ktime_add(dev->next_event, tick_period);
96 if (!clockevents_program_event(dev, next, false))
99 * Have to be careful here. If we're in oneshot mode,
100 * before we call tick_periodic() in a loop, we need
101 * to be sure we're using a real hardware clocksource.
102 * Otherwise we could get trapped in an infinite
103 * loop, as the tick_periodic() increments jiffies,
104 * when then will increment time, posibly causing
105 * the loop to trigger again and again.
107 if (timekeeping_valid_for_hres())
109 next = ktime_add(next, tick_period);
114 * Setup the device for a periodic tick
116 void tick_setup_periodic(struct clock_event_device *dev, int broadcast)
118 tick_set_periodic_handler(dev, broadcast);
120 /* Broadcast setup ? */
121 if (!tick_device_is_functional(dev))
124 if ((dev->features & CLOCK_EVT_FEAT_PERIODIC) &&
125 !tick_broadcast_oneshot_active()) {
126 clockevents_set_mode(dev, CLOCK_EVT_MODE_PERIODIC);
132 seq = read_seqbegin(&jiffies_lock);
133 next = tick_next_period;
134 } while (read_seqretry(&jiffies_lock, seq));
136 clockevents_set_mode(dev, CLOCK_EVT_MODE_ONESHOT);
139 if (!clockevents_program_event(dev, next, false))
141 next = ktime_add(next, tick_period);
147 * Setup the tick device
149 static void tick_setup_device(struct tick_device *td,
150 struct clock_event_device *newdev, int cpu,
151 const struct cpumask *cpumask)
154 void (*handler)(struct clock_event_device *) = NULL;
157 * First device setup ?
161 * If no cpu took the do_timer update, assign it to
164 if (tick_do_timer_cpu == TICK_DO_TIMER_BOOT) {
165 if (!tick_nohz_full_cpu(cpu))
166 tick_do_timer_cpu = cpu;
168 tick_do_timer_cpu = TICK_DO_TIMER_NONE;
169 tick_next_period = ktime_get();
170 tick_period = ktime_set(0, NSEC_PER_SEC / HZ);
174 * Startup in periodic mode first.
176 td->mode = TICKDEV_MODE_PERIODIC;
178 handler = td->evtdev->event_handler;
179 next_event = td->evtdev->next_event;
180 td->evtdev->event_handler = clockevents_handle_noop;
186 * When the device is not per cpu, pin the interrupt to the
189 if (!cpumask_equal(newdev->cpumask, cpumask))
190 irq_set_affinity(newdev->irq, cpumask);
193 * When global broadcasting is active, check if the current
194 * device is registered as a placeholder for broadcast mode.
195 * This allows us to handle this x86 misfeature in a generic
198 if (tick_device_uses_broadcast(newdev, cpu))
201 if (td->mode == TICKDEV_MODE_PERIODIC)
202 tick_setup_periodic(newdev, 0);
204 tick_setup_oneshot(newdev, handler, next_event);
208 * Check, if the new registered device should be used. Called with
209 * clockevents_lock held and interrupts disabled.
211 void tick_check_new_device(struct clock_event_device *newdev)
213 struct clock_event_device *curdev;
214 struct tick_device *td;
217 cpu = smp_processor_id();
218 if (!cpumask_test_cpu(cpu, newdev->cpumask))
221 td = &per_cpu(tick_cpu_device, cpu);
224 /* cpu local device ? */
225 if (!cpumask_equal(newdev->cpumask, cpumask_of(cpu))) {
228 * If the cpu affinity of the device interrupt can not
231 if (!irq_can_set_affinity(newdev->irq))
235 * If we have a cpu local device already, do not replace it
236 * by a non cpu local device
238 if (curdev && cpumask_equal(curdev->cpumask, cpumask_of(cpu)))
243 * If we have an active device, then check the rating and the oneshot
248 * Prefer one shot capable devices !
250 if ((curdev->features & CLOCK_EVT_FEAT_ONESHOT) &&
251 !(newdev->features & CLOCK_EVT_FEAT_ONESHOT))
256 if (curdev->rating >= newdev->rating)
261 * Replace the eventually existing device by the new
262 * device. If the current device is the broadcast device, do
263 * not give it back to the clockevents layer !
265 if (tick_is_broadcast_device(curdev)) {
266 clockevents_shutdown(curdev);
269 clockevents_exchange_device(curdev, newdev);
270 tick_setup_device(td, newdev, cpu, cpumask_of(cpu));
271 if (newdev->features & CLOCK_EVT_FEAT_ONESHOT)
272 tick_oneshot_notify();
277 * Can the new device be used as a broadcast device ?
279 tick_install_broadcast_device(newdev);
283 * Transfer the do_timer job away from a dying cpu.
285 * Called with interrupts disabled.
287 void tick_handover_do_timer(int *cpup)
289 if (*cpup == tick_do_timer_cpu) {
290 int cpu = cpumask_first(cpu_online_mask);
292 tick_do_timer_cpu = (cpu < nr_cpu_ids) ? cpu :
298 * Shutdown an event device on a given cpu:
300 * This is called on a life CPU, when a CPU is dead. So we cannot
301 * access the hardware device itself.
302 * We just set the mode and remove it from the lists.
304 void tick_shutdown(unsigned int *cpup)
306 struct tick_device *td = &per_cpu(tick_cpu_device, *cpup);
307 struct clock_event_device *dev = td->evtdev;
309 td->mode = TICKDEV_MODE_PERIODIC;
312 * Prevent that the clock events layer tries to call
313 * the set mode function!
315 dev->mode = CLOCK_EVT_MODE_UNUSED;
316 clockevents_exchange_device(dev, NULL);
317 dev->event_handler = clockevents_handle_noop;
322 void tick_suspend(void)
324 struct tick_device *td = &__get_cpu_var(tick_cpu_device);
326 clockevents_shutdown(td->evtdev);
329 void tick_resume(void)
331 struct tick_device *td = &__get_cpu_var(tick_cpu_device);
332 int broadcast = tick_resume_broadcast();
334 clockevents_set_mode(td->evtdev, CLOCK_EVT_MODE_RESUME);
337 if (td->mode == TICKDEV_MODE_PERIODIC)
338 tick_setup_periodic(td->evtdev, 0);
340 tick_resume_oneshot();
345 * tick_init - initialize the tick control
347 void __init tick_init(void)
349 tick_broadcast_init();