x86/xen: resume timer irqs early
[linux/fpc-iii.git] / kernel / time / tick-common.c
blob271ce26faa21160b6acf2f33b560a15095434dc4
1 /*
2 * linux/kernel/time/tick-common.c
4 * This file contains the base functions to manage periodic tick
5 * related events.
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"
28 * Tick devices
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;
35 ktime_t tick_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);
46 /**
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))
54 return 0;
55 if (!(dev->features & CLOCK_EVT_FEAT_C3STOP))
56 return 1;
57 return tick_broadcast_oneshot_available();
61 * Periodic tick
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);
71 do_timer(1);
72 write_sequnlock(&jiffies_lock);
75 update_process_times(user_mode(get_irq_regs()));
76 profile_tick(CPU_PROFILING);
80 * Event handler for periodic ticks
82 void tick_handle_periodic(struct clock_event_device *dev)
84 int cpu = smp_processor_id();
85 ktime_t next;
87 tick_periodic(cpu);
89 if (dev->mode != CLOCK_EVT_MODE_ONESHOT)
90 return;
92 * Setup the next period for devices, which do not have
93 * periodic mode:
95 next = ktime_add(dev->next_event, tick_period);
96 for (;;) {
97 if (!clockevents_program_event(dev, next, false))
98 return;
100 * Have to be careful here. If we're in oneshot mode,
101 * before we call tick_periodic() in a loop, we need
102 * to be sure we're using a real hardware clocksource.
103 * Otherwise we could get trapped in an infinite
104 * loop, as the tick_periodic() increments jiffies,
105 * when then will increment time, posibly causing
106 * the loop to trigger again and again.
108 if (timekeeping_valid_for_hres())
109 tick_periodic(cpu);
110 next = ktime_add(next, tick_period);
115 * Setup the device for a periodic tick
117 void tick_setup_periodic(struct clock_event_device *dev, int broadcast)
119 tick_set_periodic_handler(dev, broadcast);
121 /* Broadcast setup ? */
122 if (!tick_device_is_functional(dev))
123 return;
125 if ((dev->features & CLOCK_EVT_FEAT_PERIODIC) &&
126 !tick_broadcast_oneshot_active()) {
127 clockevents_set_mode(dev, CLOCK_EVT_MODE_PERIODIC);
128 } else {
129 unsigned long seq;
130 ktime_t next;
132 do {
133 seq = read_seqbegin(&jiffies_lock);
134 next = tick_next_period;
135 } while (read_seqretry(&jiffies_lock, seq));
137 clockevents_set_mode(dev, CLOCK_EVT_MODE_ONESHOT);
139 for (;;) {
140 if (!clockevents_program_event(dev, next, false))
141 return;
142 next = ktime_add(next, tick_period);
148 * Setup the tick device
150 static void tick_setup_device(struct tick_device *td,
151 struct clock_event_device *newdev, int cpu,
152 const struct cpumask *cpumask)
154 ktime_t next_event;
155 void (*handler)(struct clock_event_device *) = NULL;
158 * First device setup ?
160 if (!td->evtdev) {
162 * If no cpu took the do_timer update, assign it to
163 * this cpu:
165 if (tick_do_timer_cpu == TICK_DO_TIMER_BOOT) {
166 if (!tick_nohz_full_cpu(cpu))
167 tick_do_timer_cpu = cpu;
168 else
169 tick_do_timer_cpu = TICK_DO_TIMER_NONE;
170 tick_next_period = ktime_get();
171 tick_period = ktime_set(0, NSEC_PER_SEC / HZ);
175 * Startup in periodic mode first.
177 td->mode = TICKDEV_MODE_PERIODIC;
178 } else {
179 handler = td->evtdev->event_handler;
180 next_event = td->evtdev->next_event;
181 td->evtdev->event_handler = clockevents_handle_noop;
184 td->evtdev = newdev;
187 * When the device is not per cpu, pin the interrupt to the
188 * current cpu:
190 if (!cpumask_equal(newdev->cpumask, cpumask))
191 irq_set_affinity(newdev->irq, cpumask);
194 * When global broadcasting is active, check if the current
195 * device is registered as a placeholder for broadcast mode.
196 * This allows us to handle this x86 misfeature in a generic
197 * way. This function also returns !=0 when we keep the
198 * current active broadcast state for this CPU.
200 if (tick_device_uses_broadcast(newdev, cpu))
201 return;
203 if (td->mode == TICKDEV_MODE_PERIODIC)
204 tick_setup_periodic(newdev, 0);
205 else
206 tick_setup_oneshot(newdev, handler, next_event);
209 void tick_install_replacement(struct clock_event_device *newdev)
211 struct tick_device *td = &__get_cpu_var(tick_cpu_device);
212 int cpu = smp_processor_id();
214 clockevents_exchange_device(td->evtdev, newdev);
215 tick_setup_device(td, newdev, cpu, cpumask_of(cpu));
216 if (newdev->features & CLOCK_EVT_FEAT_ONESHOT)
217 tick_oneshot_notify();
220 static bool tick_check_percpu(struct clock_event_device *curdev,
221 struct clock_event_device *newdev, int cpu)
223 if (!cpumask_test_cpu(cpu, newdev->cpumask))
224 return false;
225 if (cpumask_equal(newdev->cpumask, cpumask_of(cpu)))
226 return true;
227 /* Check if irq affinity can be set */
228 if (newdev->irq >= 0 && !irq_can_set_affinity(newdev->irq))
229 return false;
230 /* Prefer an existing cpu local device */
231 if (curdev && cpumask_equal(curdev->cpumask, cpumask_of(cpu)))
232 return false;
233 return true;
236 static bool tick_check_preferred(struct clock_event_device *curdev,
237 struct clock_event_device *newdev)
239 /* Prefer oneshot capable device */
240 if (!(newdev->features & CLOCK_EVT_FEAT_ONESHOT)) {
241 if (curdev && (curdev->features & CLOCK_EVT_FEAT_ONESHOT))
242 return false;
243 if (tick_oneshot_mode_active())
244 return false;
248 * Use the higher rated one, but prefer a CPU local device with a lower
249 * rating than a non-CPU local device
251 return !curdev ||
252 newdev->rating > curdev->rating ||
253 !cpumask_equal(curdev->cpumask, newdev->cpumask);
257 * Check whether the new device is a better fit than curdev. curdev
258 * can be NULL !
260 bool tick_check_replacement(struct clock_event_device *curdev,
261 struct clock_event_device *newdev)
263 if (!tick_check_percpu(curdev, newdev, smp_processor_id()))
264 return false;
266 return tick_check_preferred(curdev, newdev);
270 * Check, if the new registered device should be used. Called with
271 * clockevents_lock held and interrupts disabled.
273 void tick_check_new_device(struct clock_event_device *newdev)
275 struct clock_event_device *curdev;
276 struct tick_device *td;
277 int cpu;
279 cpu = smp_processor_id();
280 if (!cpumask_test_cpu(cpu, newdev->cpumask))
281 goto out_bc;
283 td = &per_cpu(tick_cpu_device, cpu);
284 curdev = td->evtdev;
286 /* cpu local device ? */
287 if (!tick_check_percpu(curdev, newdev, cpu))
288 goto out_bc;
290 /* Preference decision */
291 if (!tick_check_preferred(curdev, newdev))
292 goto out_bc;
294 if (!try_module_get(newdev->owner))
295 return;
298 * Replace the eventually existing device by the new
299 * device. If the current device is the broadcast device, do
300 * not give it back to the clockevents layer !
302 if (tick_is_broadcast_device(curdev)) {
303 clockevents_shutdown(curdev);
304 curdev = NULL;
306 clockevents_exchange_device(curdev, newdev);
307 tick_setup_device(td, newdev, cpu, cpumask_of(cpu));
308 if (newdev->features & CLOCK_EVT_FEAT_ONESHOT)
309 tick_oneshot_notify();
310 return;
312 out_bc:
314 * Can the new device be used as a broadcast device ?
316 tick_install_broadcast_device(newdev);
320 * Transfer the do_timer job away from a dying cpu.
322 * Called with interrupts disabled.
324 void tick_handover_do_timer(int *cpup)
326 if (*cpup == tick_do_timer_cpu) {
327 int cpu = cpumask_first(cpu_online_mask);
329 tick_do_timer_cpu = (cpu < nr_cpu_ids) ? cpu :
330 TICK_DO_TIMER_NONE;
335 * Shutdown an event device on a given cpu:
337 * This is called on a life CPU, when a CPU is dead. So we cannot
338 * access the hardware device itself.
339 * We just set the mode and remove it from the lists.
341 void tick_shutdown(unsigned int *cpup)
343 struct tick_device *td = &per_cpu(tick_cpu_device, *cpup);
344 struct clock_event_device *dev = td->evtdev;
346 td->mode = TICKDEV_MODE_PERIODIC;
347 if (dev) {
349 * Prevent that the clock events layer tries to call
350 * the set mode function!
352 dev->mode = CLOCK_EVT_MODE_UNUSED;
353 clockevents_exchange_device(dev, NULL);
354 dev->event_handler = clockevents_handle_noop;
355 td->evtdev = NULL;
359 void tick_suspend(void)
361 struct tick_device *td = &__get_cpu_var(tick_cpu_device);
363 clockevents_shutdown(td->evtdev);
366 void tick_resume(void)
368 struct tick_device *td = &__get_cpu_var(tick_cpu_device);
369 int broadcast = tick_resume_broadcast();
371 clockevents_set_mode(td->evtdev, CLOCK_EVT_MODE_RESUME);
373 if (!broadcast) {
374 if (td->mode == TICKDEV_MODE_PERIODIC)
375 tick_setup_periodic(td->evtdev, 0);
376 else
377 tick_resume_oneshot();
382 * tick_init - initialize the tick control
384 void __init tick_init(void)
386 tick_broadcast_init();