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/module.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;
39 * Debugging: see timer_list.c
41 struct tick_device *tick_get_device(int cpu)
43 return &per_cpu(tick_cpu_device, cpu);
47 * tick_is_oneshot_available - check for a oneshot capable event device
49 int tick_is_oneshot_available(void)
51 struct clock_event_device *dev = __this_cpu_read(tick_cpu_device.evtdev);
53 if (!dev || !(dev->features & CLOCK_EVT_FEAT_ONESHOT))
55 if (!(dev->features & CLOCK_EVT_FEAT_C3STOP))
57 return tick_broadcast_oneshot_available();
63 static void tick_periodic(int cpu)
65 if (tick_do_timer_cpu == cpu) {
66 write_seqlock(&jiffies_lock);
68 /* Keep track of the next tick event */
69 tick_next_period = ktime_add(tick_next_period, tick_period);
72 write_sequnlock(&jiffies_lock);
76 update_process_times(user_mode(get_irq_regs()));
77 profile_tick(CPU_PROFILING);
81 * Event handler for periodic ticks
83 void tick_handle_periodic(struct clock_event_device *dev)
85 int cpu = smp_processor_id();
90 if (dev->mode != CLOCK_EVT_MODE_ONESHOT)
93 * Setup the next period for devices, which do not have
96 next = ktime_add(dev->next_event, tick_period);
98 if (!clockevents_program_event(dev, next, false))
101 * Have to be careful here. If we're in oneshot mode,
102 * before we call tick_periodic() in a loop, we need
103 * to be sure we're using a real hardware clocksource.
104 * Otherwise we could get trapped in an infinite
105 * loop, as the tick_periodic() increments jiffies,
106 * when then will increment time, posibly causing
107 * the loop to trigger again and again.
109 if (timekeeping_valid_for_hres())
111 next = ktime_add(next, tick_period);
116 * Setup the device for a periodic tick
118 void tick_setup_periodic(struct clock_event_device *dev, int broadcast)
120 tick_set_periodic_handler(dev, broadcast);
122 /* Broadcast setup ? */
123 if (!tick_device_is_functional(dev))
126 if ((dev->features & CLOCK_EVT_FEAT_PERIODIC) &&
127 !tick_broadcast_oneshot_active()) {
128 clockevents_set_mode(dev, CLOCK_EVT_MODE_PERIODIC);
134 seq = read_seqbegin(&jiffies_lock);
135 next = tick_next_period;
136 } while (read_seqretry(&jiffies_lock, seq));
138 clockevents_set_mode(dev, CLOCK_EVT_MODE_ONESHOT);
141 if (!clockevents_program_event(dev, next, false))
143 next = ktime_add(next, tick_period);
149 * Setup the tick device
151 static void tick_setup_device(struct tick_device *td,
152 struct clock_event_device *newdev, int cpu,
153 const struct cpumask *cpumask)
156 void (*handler)(struct clock_event_device *) = NULL;
159 * First device setup ?
163 * If no cpu took the do_timer update, assign it to
166 if (tick_do_timer_cpu == TICK_DO_TIMER_BOOT) {
167 if (!tick_nohz_full_cpu(cpu))
168 tick_do_timer_cpu = cpu;
170 tick_do_timer_cpu = TICK_DO_TIMER_NONE;
171 tick_next_period = ktime_get();
172 tick_period = ktime_set(0, NSEC_PER_SEC / HZ);
176 * Startup in periodic mode first.
178 td->mode = TICKDEV_MODE_PERIODIC;
180 handler = td->evtdev->event_handler;
181 next_event = td->evtdev->next_event;
182 td->evtdev->event_handler = clockevents_handle_noop;
188 * When the device is not per cpu, pin the interrupt to the
191 if (!cpumask_equal(newdev->cpumask, cpumask))
192 irq_set_affinity(newdev->irq, cpumask);
195 * When global broadcasting is active, check if the current
196 * device is registered as a placeholder for broadcast mode.
197 * This allows us to handle this x86 misfeature in a generic
198 * way. This function also returns !=0 when we keep the
199 * current active broadcast state for this CPU.
201 if (tick_device_uses_broadcast(newdev, cpu))
204 if (td->mode == TICKDEV_MODE_PERIODIC)
205 tick_setup_periodic(newdev, 0);
207 tick_setup_oneshot(newdev, handler, next_event);
210 void tick_install_replacement(struct clock_event_device *newdev)
212 struct tick_device *td = &__get_cpu_var(tick_cpu_device);
213 int cpu = smp_processor_id();
215 clockevents_exchange_device(td->evtdev, newdev);
216 tick_setup_device(td, newdev, cpu, cpumask_of(cpu));
217 if (newdev->features & CLOCK_EVT_FEAT_ONESHOT)
218 tick_oneshot_notify();
221 static bool tick_check_percpu(struct clock_event_device *curdev,
222 struct clock_event_device *newdev, int cpu)
224 if (!cpumask_test_cpu(cpu, newdev->cpumask))
226 if (cpumask_equal(newdev->cpumask, cpumask_of(cpu)))
228 /* Check if irq affinity can be set */
229 if (newdev->irq >= 0 && !irq_can_set_affinity(newdev->irq))
231 /* Prefer an existing cpu local device */
232 if (curdev && cpumask_equal(curdev->cpumask, cpumask_of(cpu)))
237 static bool tick_check_preferred(struct clock_event_device *curdev,
238 struct clock_event_device *newdev)
240 /* Prefer oneshot capable device */
241 if (!(newdev->features & CLOCK_EVT_FEAT_ONESHOT)) {
242 if (curdev && (curdev->features & CLOCK_EVT_FEAT_ONESHOT))
244 if (tick_oneshot_mode_active())
249 * Use the higher rated one, but prefer a CPU local device with a lower
250 * rating than a non-CPU local device
253 newdev->rating > curdev->rating ||
254 !cpumask_equal(curdev->cpumask, newdev->cpumask);
258 * Check whether the new device is a better fit than curdev. curdev
261 bool tick_check_replacement(struct clock_event_device *curdev,
262 struct clock_event_device *newdev)
264 if (tick_check_percpu(curdev, newdev, smp_processor_id()))
267 return tick_check_preferred(curdev, newdev);
271 * Check, if the new registered device should be used. Called with
272 * clockevents_lock held and interrupts disabled.
274 void tick_check_new_device(struct clock_event_device *newdev)
276 struct clock_event_device *curdev;
277 struct tick_device *td;
280 cpu = smp_processor_id();
281 if (!cpumask_test_cpu(cpu, newdev->cpumask))
284 td = &per_cpu(tick_cpu_device, cpu);
287 /* cpu local device ? */
288 if (!tick_check_percpu(curdev, newdev, cpu))
291 /* Preference decision */
292 if (!tick_check_preferred(curdev, newdev))
295 if (!try_module_get(newdev->owner))
299 * Replace the eventually existing device by the new
300 * device. If the current device is the broadcast device, do
301 * not give it back to the clockevents layer !
303 if (tick_is_broadcast_device(curdev)) {
304 clockevents_shutdown(curdev);
307 clockevents_exchange_device(curdev, newdev);
308 tick_setup_device(td, newdev, cpu, cpumask_of(cpu));
309 if (newdev->features & CLOCK_EVT_FEAT_ONESHOT)
310 tick_oneshot_notify();
315 * Can the new device be used as a broadcast device ?
317 tick_install_broadcast_device(newdev);
321 * Transfer the do_timer job away from a dying cpu.
323 * Called with interrupts disabled.
325 void tick_handover_do_timer(int *cpup)
327 if (*cpup == tick_do_timer_cpu) {
328 int cpu = cpumask_first(cpu_online_mask);
330 tick_do_timer_cpu = (cpu < nr_cpu_ids) ? cpu :
336 * Shutdown an event device on a given cpu:
338 * This is called on a life CPU, when a CPU is dead. So we cannot
339 * access the hardware device itself.
340 * We just set the mode and remove it from the lists.
342 void tick_shutdown(unsigned int *cpup)
344 struct tick_device *td = &per_cpu(tick_cpu_device, *cpup);
345 struct clock_event_device *dev = td->evtdev;
347 td->mode = TICKDEV_MODE_PERIODIC;
350 * Prevent that the clock events layer tries to call
351 * the set mode function!
353 dev->mode = CLOCK_EVT_MODE_UNUSED;
354 clockevents_exchange_device(dev, NULL);
355 dev->event_handler = clockevents_handle_noop;
360 void tick_suspend(void)
362 struct tick_device *td = &__get_cpu_var(tick_cpu_device);
364 clockevents_shutdown(td->evtdev);
367 void tick_resume(void)
369 struct tick_device *td = &__get_cpu_var(tick_cpu_device);
370 int broadcast = tick_resume_broadcast();
372 clockevents_set_mode(td->evtdev, CLOCK_EVT_MODE_RESUME);
375 if (td->mode == TICKDEV_MODE_PERIODIC)
376 tick_setup_periodic(td->evtdev, 0);
378 tick_resume_oneshot();
383 * tick_init - initialize the tick control
385 void __init tick_init(void)
387 tick_broadcast_init();