virtio: console as a config option
[linux-2.6/linux-loongson.git] / kernel / time / tick-common.c
blobbf43284d6855ad083319d653d1b0fbc3235dde08
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/tick.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 = -1;
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);
47 /**
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);
58 * Periodic tick
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);
68 do_timer(1);
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();
82 ktime_t next;
84 tick_periodic(cpu);
86 if (dev->mode != CLOCK_EVT_MODE_ONESHOT)
87 return;
89 * Setup the next period for devices, which do not have
90 * periodic mode:
92 next = ktime_add(dev->next_event, tick_period);
93 for (;;) {
94 if (!clockevents_program_event(dev, next, ktime_get()))
95 return;
96 tick_periodic(cpu);
97 next = ktime_add(next, tick_period);
102 * Setup the device for a periodic tick
104 void tick_setup_periodic(struct clock_event_device *dev, int broadcast)
106 tick_set_periodic_handler(dev, broadcast);
108 /* Broadcast setup ? */
109 if (!tick_device_is_functional(dev))
110 return;
112 if (dev->features & CLOCK_EVT_FEAT_PERIODIC) {
113 clockevents_set_mode(dev, CLOCK_EVT_MODE_PERIODIC);
114 } else {
115 unsigned long seq;
116 ktime_t next;
118 do {
119 seq = read_seqbegin(&xtime_lock);
120 next = tick_next_period;
121 } while (read_seqretry(&xtime_lock, seq));
123 clockevents_set_mode(dev, CLOCK_EVT_MODE_ONESHOT);
125 for (;;) {
126 if (!clockevents_program_event(dev, next, ktime_get()))
127 return;
128 next = ktime_add(next, tick_period);
134 * Setup the tick device
136 static void tick_setup_device(struct tick_device *td,
137 struct clock_event_device *newdev, int cpu,
138 const cpumask_t *cpumask)
140 ktime_t next_event;
141 void (*handler)(struct clock_event_device *) = NULL;
144 * First device setup ?
146 if (!td->evtdev) {
148 * If no cpu took the do_timer update, assign it to
149 * this cpu:
151 if (tick_do_timer_cpu == -1) {
152 tick_do_timer_cpu = cpu;
153 tick_next_period = ktime_get();
154 tick_period = ktime_set(0, NSEC_PER_SEC / HZ);
158 * Startup in periodic mode first.
160 td->mode = TICKDEV_MODE_PERIODIC;
161 } else {
162 handler = td->evtdev->event_handler;
163 next_event = td->evtdev->next_event;
166 td->evtdev = newdev;
169 * When the device is not per cpu, pin the interrupt to the
170 * current cpu:
172 if (!cpus_equal(newdev->cpumask, *cpumask))
173 irq_set_affinity(newdev->irq, *cpumask);
176 * When global broadcasting is active, check if the current
177 * device is registered as a placeholder for broadcast mode.
178 * This allows us to handle this x86 misfeature in a generic
179 * way.
181 if (tick_device_uses_broadcast(newdev, cpu))
182 return;
184 if (td->mode == TICKDEV_MODE_PERIODIC)
185 tick_setup_periodic(newdev, 0);
186 else
187 tick_setup_oneshot(newdev, handler, next_event);
191 * Check, if the new registered device should be used.
193 static int tick_check_new_device(struct clock_event_device *newdev)
195 struct clock_event_device *curdev;
196 struct tick_device *td;
197 int cpu, ret = NOTIFY_OK;
198 unsigned long flags;
199 cpumask_of_cpu_ptr_declare(cpumask);
201 spin_lock_irqsave(&tick_device_lock, flags);
203 cpu = smp_processor_id();
204 cpumask_of_cpu_ptr_next(cpumask, cpu);
205 if (!cpu_isset(cpu, newdev->cpumask))
206 goto out_bc;
208 td = &per_cpu(tick_cpu_device, cpu);
209 curdev = td->evtdev;
211 /* cpu local device ? */
212 if (!cpus_equal(newdev->cpumask, *cpumask)) {
215 * If the cpu affinity of the device interrupt can not
216 * be set, ignore it.
218 if (!irq_can_set_affinity(newdev->irq))
219 goto out_bc;
222 * If we have a cpu local device already, do not replace it
223 * by a non cpu local device
225 if (curdev && cpus_equal(curdev->cpumask, *cpumask))
226 goto out_bc;
230 * If we have an active device, then check the rating and the oneshot
231 * feature.
233 if (curdev) {
235 * Prefer one shot capable devices !
237 if ((curdev->features & CLOCK_EVT_FEAT_ONESHOT) &&
238 !(newdev->features & CLOCK_EVT_FEAT_ONESHOT))
239 goto out_bc;
241 * Check the rating
243 if (curdev->rating >= newdev->rating)
244 goto out_bc;
248 * Replace the eventually existing device by the new
249 * device. If the current device is the broadcast device, do
250 * not give it back to the clockevents layer !
252 if (tick_is_broadcast_device(curdev)) {
253 clockevents_set_mode(curdev, CLOCK_EVT_MODE_SHUTDOWN);
254 curdev = NULL;
256 clockevents_exchange_device(curdev, newdev);
257 tick_setup_device(td, newdev, cpu, cpumask);
258 if (newdev->features & CLOCK_EVT_FEAT_ONESHOT)
259 tick_oneshot_notify();
261 spin_unlock_irqrestore(&tick_device_lock, flags);
262 return NOTIFY_STOP;
264 out_bc:
266 * Can the new device be used as a broadcast device ?
268 if (tick_check_broadcast_device(newdev))
269 ret = NOTIFY_STOP;
271 spin_unlock_irqrestore(&tick_device_lock, flags);
273 return ret;
277 * Shutdown an event device on a given cpu:
279 * This is called on a life CPU, when a CPU is dead. So we cannot
280 * access the hardware device itself.
281 * We just set the mode and remove it from the lists.
283 static void tick_shutdown(unsigned int *cpup)
285 struct tick_device *td = &per_cpu(tick_cpu_device, *cpup);
286 struct clock_event_device *dev = td->evtdev;
287 unsigned long flags;
289 spin_lock_irqsave(&tick_device_lock, flags);
290 td->mode = TICKDEV_MODE_PERIODIC;
291 if (dev) {
293 * Prevent that the clock events layer tries to call
294 * the set mode function!
296 dev->mode = CLOCK_EVT_MODE_UNUSED;
297 clockevents_exchange_device(dev, NULL);
298 td->evtdev = NULL;
300 /* Transfer the do_timer job away from this cpu */
301 if (*cpup == tick_do_timer_cpu) {
302 int cpu = first_cpu(cpu_online_map);
304 tick_do_timer_cpu = (cpu != NR_CPUS) ? cpu : -1;
306 spin_unlock_irqrestore(&tick_device_lock, flags);
309 static void tick_suspend(void)
311 struct tick_device *td = &__get_cpu_var(tick_cpu_device);
312 unsigned long flags;
314 spin_lock_irqsave(&tick_device_lock, flags);
315 clockevents_set_mode(td->evtdev, CLOCK_EVT_MODE_SHUTDOWN);
316 spin_unlock_irqrestore(&tick_device_lock, flags);
319 static void tick_resume(void)
321 struct tick_device *td = &__get_cpu_var(tick_cpu_device);
322 unsigned long flags;
323 int broadcast = tick_resume_broadcast();
325 spin_lock_irqsave(&tick_device_lock, flags);
326 clockevents_set_mode(td->evtdev, CLOCK_EVT_MODE_RESUME);
328 if (!broadcast) {
329 if (td->mode == TICKDEV_MODE_PERIODIC)
330 tick_setup_periodic(td->evtdev, 0);
331 else
332 tick_resume_oneshot();
334 spin_unlock_irqrestore(&tick_device_lock, flags);
338 * Notification about clock event devices
340 static int tick_notify(struct notifier_block *nb, unsigned long reason,
341 void *dev)
343 switch (reason) {
345 case CLOCK_EVT_NOTIFY_ADD:
346 return tick_check_new_device(dev);
348 case CLOCK_EVT_NOTIFY_BROADCAST_ON:
349 case CLOCK_EVT_NOTIFY_BROADCAST_OFF:
350 case CLOCK_EVT_NOTIFY_BROADCAST_FORCE:
351 tick_broadcast_on_off(reason, dev);
352 break;
354 case CLOCK_EVT_NOTIFY_BROADCAST_ENTER:
355 case CLOCK_EVT_NOTIFY_BROADCAST_EXIT:
356 tick_broadcast_oneshot_control(reason);
357 break;
359 case CLOCK_EVT_NOTIFY_CPU_DEAD:
360 tick_shutdown_broadcast_oneshot(dev);
361 tick_shutdown_broadcast(dev);
362 tick_shutdown(dev);
363 break;
365 case CLOCK_EVT_NOTIFY_SUSPEND:
366 tick_suspend();
367 tick_suspend_broadcast();
368 break;
370 case CLOCK_EVT_NOTIFY_RESUME:
371 tick_resume();
372 break;
374 default:
375 break;
378 return NOTIFY_OK;
381 static struct notifier_block tick_notifier = {
382 .notifier_call = tick_notify,
386 * tick_init - initialize the tick control
388 * Register the notifier with the clockevents framework
390 void __init tick_init(void)
392 clockevents_register_notifier(&tick_notifier);