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/irq.h>
18 #include <linux/percpu.h>
19 #include <linux/profile.h>
20 #include <linux/sched.h>
21 #include <linux/tick.h>
23 #include "tick-internal.h"
28 DEFINE_PER_CPU(struct tick_device, tick_cpu_device);
30 * Tick next event: keeps track of the tick time
32 ktime_t tick_next_period;
34 static int tick_do_timer_cpu = -1;
35 DEFINE_SPINLOCK(tick_device_lock);
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 = __get_cpu_var(tick_cpu_device).evtdev;
52 return dev && (dev->features & CLOCK_EVT_FEAT_ONESHOT);
58 static void tick_periodic(int cpu)
60 if (tick_do_timer_cpu == cpu) {
61 write_seqlock(&xtime_lock);
63 /* Keep track of the next tick event */
64 tick_next_period = ktime_add(tick_next_period, tick_period);
67 write_sequnlock(&xtime_lock);
70 update_process_times(user_mode(get_irq_regs()));
71 profile_tick(CPU_PROFILING);
75 * Event handler for periodic ticks
77 void tick_handle_periodic(struct clock_event_device *dev)
79 int cpu = smp_processor_id();
83 if (dev->mode != CLOCK_EVT_MODE_ONESHOT)
86 * Setup the next period for devices, which do not have
90 ktime_t next = ktime_add(dev->next_event, tick_period);
92 if (!clockevents_program_event(dev, next, ktime_get()))
99 * Setup the device for a periodic tick
101 void tick_setup_periodic(struct clock_event_device *dev, int broadcast)
103 tick_set_periodic_handler(dev, broadcast);
105 /* Broadcast setup ? */
106 if (!tick_device_is_functional(dev))
109 if (dev->features & CLOCK_EVT_FEAT_PERIODIC) {
110 clockevents_set_mode(dev, CLOCK_EVT_MODE_PERIODIC);
116 seq = read_seqbegin(&xtime_lock);
117 next = tick_next_period;
118 } while (read_seqretry(&xtime_lock, seq));
120 clockevents_set_mode(dev, CLOCK_EVT_MODE_ONESHOT);
123 if (!clockevents_program_event(dev, next, ktime_get()))
125 next = ktime_add(next, tick_period);
131 * Setup the tick device
133 static void tick_setup_device(struct tick_device *td,
134 struct clock_event_device *newdev, int cpu,
138 void (*handler)(struct clock_event_device *) = NULL;
141 * First device setup ?
145 * If no cpu took the do_timer update, assign it to
148 if (tick_do_timer_cpu == -1) {
149 tick_do_timer_cpu = cpu;
150 tick_next_period = ktime_get();
151 tick_period = ktime_set(0, NSEC_PER_SEC / HZ);
155 * Startup in periodic mode first.
157 td->mode = TICKDEV_MODE_PERIODIC;
159 handler = td->evtdev->event_handler;
160 next_event = td->evtdev->next_event;
166 * When the device is not per cpu, pin the interrupt to the
169 if (!cpus_equal(newdev->cpumask, cpumask))
170 irq_set_affinity(newdev->irq, cpumask);
173 * When global broadcasting is active, check if the current
174 * device is registered as a placeholder for broadcast mode.
175 * This allows us to handle this x86 misfeature in a generic
178 if (tick_device_uses_broadcast(newdev, cpu))
181 if (td->mode == TICKDEV_MODE_PERIODIC)
182 tick_setup_periodic(newdev, 0);
184 tick_setup_oneshot(newdev, handler, next_event);
188 * Check, if the new registered device should be used.
190 static int tick_check_new_device(struct clock_event_device *newdev)
192 struct clock_event_device *curdev;
193 struct tick_device *td;
194 int cpu, ret = NOTIFY_OK;
198 spin_lock_irqsave(&tick_device_lock, flags);
200 cpu = smp_processor_id();
201 if (!cpu_isset(cpu, newdev->cpumask))
204 td = &per_cpu(tick_cpu_device, cpu);
206 cpumask = cpumask_of_cpu(cpu);
208 /* cpu local device ? */
209 if (!cpus_equal(newdev->cpumask, cpumask)) {
212 * If the cpu affinity of the device interrupt can not
215 if (!irq_can_set_affinity(newdev->irq))
219 * If we have a cpu local device already, do not replace it
220 * by a non cpu local device
222 if (curdev && cpus_equal(curdev->cpumask, cpumask))
227 * If we have an active device, then check the rating and the oneshot
232 * Prefer one shot capable devices !
234 if ((curdev->features & CLOCK_EVT_FEAT_ONESHOT) &&
235 !(newdev->features & CLOCK_EVT_FEAT_ONESHOT))
240 if (curdev->rating >= newdev->rating)
245 * Replace the eventually existing device by the new
246 * device. If the current device is the broadcast device, do
247 * not give it back to the clockevents layer !
249 if (tick_is_broadcast_device(curdev)) {
250 clockevents_set_mode(curdev, CLOCK_EVT_MODE_SHUTDOWN);
253 clockevents_exchange_device(curdev, newdev);
254 tick_setup_device(td, newdev, cpu, cpumask);
255 if (newdev->features & CLOCK_EVT_FEAT_ONESHOT)
256 tick_oneshot_notify();
258 spin_unlock_irqrestore(&tick_device_lock, flags);
263 * Can the new device be used as a broadcast device ?
265 if (tick_check_broadcast_device(newdev))
268 spin_unlock_irqrestore(&tick_device_lock, flags);
274 * Shutdown an event device on a given cpu:
276 * This is called on a life CPU, when a CPU is dead. So we cannot
277 * access the hardware device itself.
278 * We just set the mode and remove it from the lists.
280 static void tick_shutdown(unsigned int *cpup)
282 struct tick_device *td = &per_cpu(tick_cpu_device, *cpup);
283 struct clock_event_device *dev = td->evtdev;
286 spin_lock_irqsave(&tick_device_lock, flags);
287 td->mode = TICKDEV_MODE_PERIODIC;
290 * Prevent that the clock events layer tries to call
291 * the set mode function!
293 dev->mode = CLOCK_EVT_MODE_UNUSED;
294 clockevents_exchange_device(dev, NULL);
297 spin_unlock_irqrestore(&tick_device_lock, flags);
301 * Notification about clock event devices
303 static int tick_notify(struct notifier_block *nb, unsigned long reason,
308 case CLOCK_EVT_NOTIFY_ADD:
309 return tick_check_new_device(dev);
311 case CLOCK_EVT_NOTIFY_BROADCAST_ON:
312 case CLOCK_EVT_NOTIFY_BROADCAST_OFF:
313 tick_broadcast_on_off(reason, dev);
316 case CLOCK_EVT_NOTIFY_BROADCAST_ENTER:
317 case CLOCK_EVT_NOTIFY_BROADCAST_EXIT:
318 tick_broadcast_oneshot_control(reason);
321 case CLOCK_EVT_NOTIFY_CPU_DEAD:
322 tick_shutdown_broadcast_oneshot(dev);
323 tick_shutdown_broadcast(dev);
334 static struct notifier_block tick_notifier = {
335 .notifier_call = tick_notify,
339 * tick_init - initialize the tick control
341 * Register the notifier with the clockevents framework
343 void __init tick_init(void)
345 clockevents_register_notifier(&tick_notifier);