tick-broadcast.c revision b7e113dc9d52c4a37d2da6fafe77959f3a28eccf 
1/*
2 * linux/kernel/time/tick-broadcast.c
3 *
4 * This file contains functions which emulate a local clock-event
5 * device via a broadcast event source.
6 *
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
10 *
11 * This code is licenced under the GPL version 2. For details see
12 * kernel-base/COPYING.
13 */
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>
22
23#include "tick-internal.h"
24
25/*
26 * Broadcast support for broken x86 hardware, where the local apic
27 * timer stops in C3 state.
28 */
29
30struct tick_device tick_broadcast_device;
31static cpumask_t tick_broadcast_mask;
32static DEFINE_SPINLOCK(tick_broadcast_lock);
33
34#ifdef CONFIG_TICK_ONESHOT
35static void tick_broadcast_clear_oneshot(int cpu);
36#else
37static inline void tick_broadcast_clear_oneshot(int cpu) { }
38#endif
39
40/*
41 * Debugging: see timer_list.c
42 */
43struct tick_device *tick_get_broadcast_device(void)
44{
45	return &tick_broadcast_device;
46}
47
48cpumask_t *tick_get_broadcast_mask(void)
49{
50	return &tick_broadcast_mask;
51}
52
53/*
54 * Start the device in periodic mode
55 */
56static void tick_broadcast_start_periodic(struct clock_event_device *bc)
57{
58	if (bc)
59		tick_setup_periodic(bc, 1);
60}
61
62/*
63 * Check, if the device can be utilized as broadcast device:
64 */
65int tick_check_broadcast_device(struct clock_event_device *dev)
66{
67	if (tick_broadcast_device.evtdev ||
68	    (dev->features & CLOCK_EVT_FEAT_C3STOP))
69		return 0;
70
71	clockevents_exchange_device(NULL, dev);
72	tick_broadcast_device.evtdev = dev;
73	if (!cpus_empty(tick_broadcast_mask))
74		tick_broadcast_start_periodic(dev);
75	return 1;
76}
77
78/*
79 * Check, if the device is the broadcast device
80 */
81int tick_is_broadcast_device(struct clock_event_device *dev)
82{
83	return (dev && tick_broadcast_device.evtdev == dev);
84}
85
86/*
87 * Check, if the device is disfunctional and a place holder, which
88 * needs to be handled by the broadcast device.
89 */
90int tick_device_uses_broadcast(struct clock_event_device *dev, int cpu)
91{
92	unsigned long flags;
93	int ret = 0;
94
95	spin_lock_irqsave(&tick_broadcast_lock, flags);
96
97	/*
98	 * Devices might be registered with both periodic and oneshot
99	 * mode disabled. This signals, that the device needs to be
100	 * operated from the broadcast device and is a placeholder for
101	 * the cpu local device.
102	 */
103	if (!tick_device_is_functional(dev)) {
104		dev->event_handler = tick_handle_periodic;
105		cpu_set(cpu, tick_broadcast_mask);
106		tick_broadcast_start_periodic(tick_broadcast_device.evtdev);
107		ret = 1;
108	} else {
109		/*
110		 * When the new device is not affected by the stop
111		 * feature and the cpu is marked in the broadcast mask
112		 * then clear the broadcast bit.
113		 */
114		if (!(dev->features & CLOCK_EVT_FEAT_C3STOP)) {
115			int cpu = smp_processor_id();
116
117			cpu_clear(cpu, tick_broadcast_mask);
118			tick_broadcast_clear_oneshot(cpu);
119		}
120	}
121	spin_unlock_irqrestore(&tick_broadcast_lock, flags);
122	return ret;
123}
124
125/*
126 * Broadcast the event to the cpus, which are set in the mask
127 */
128int tick_do_broadcast(cpumask_t mask)
129{
130	int ret = 0, cpu = smp_processor_id();
131	struct tick_device *td;
132
133	/*
134	 * Check, if the current cpu is in the mask
135	 */
136	if (cpu_isset(cpu, mask)) {
137		cpu_clear(cpu, mask);
138		td = &per_cpu(tick_cpu_device, cpu);
139		td->evtdev->event_handler(td->evtdev);
140		ret = 1;
141	}
142
143	if (!cpus_empty(mask)) {
144		/*
145		 * It might be necessary to actually check whether the devices
146		 * have different broadcast functions. For now, just use the
147		 * one of the first device. This works as long as we have this
148		 * misfeature only on x86 (lapic)
149		 */
150		cpu = first_cpu(mask);
151		td = &per_cpu(tick_cpu_device, cpu);
152		td->evtdev->broadcast(mask);
153		ret = 1;
154	}
155	return ret;
156}
157
158/*
159 * Periodic broadcast:
160 * - invoke the broadcast handlers
161 */
162static void tick_do_periodic_broadcast(void)
163{
164	cpumask_t mask;
165
166	spin_lock(&tick_broadcast_lock);
167
168	cpus_and(mask, cpu_online_map, tick_broadcast_mask);
169	tick_do_broadcast(mask);
170
171	spin_unlock(&tick_broadcast_lock);
172}
173
174/*
175 * Event handler for periodic broadcast ticks
176 */
177static void tick_handle_periodic_broadcast(struct clock_event_device *dev)
178{
179	dev->next_event.tv64 = KTIME_MAX;
180
181	tick_do_periodic_broadcast();
182
183	/*
184	 * The device is in periodic mode. No reprogramming necessary:
185	 */
186	if (dev->mode == CLOCK_EVT_MODE_PERIODIC)
187		return;
188
189	/*
190	 * Setup the next period for devices, which do not have
191	 * periodic mode:
192	 */
193	for (;;) {
194		ktime_t next = ktime_add(dev->next_event, tick_period);
195
196		if (!clockevents_program_event(dev, next, ktime_get()))
197			return;
198		tick_do_periodic_broadcast();
199	}
200}
201
202/*
203 * Powerstate information: The system enters/leaves a state, where
204 * affected devices might stop
205 */
206static void tick_do_broadcast_on_off(void *why)
207{
208	struct clock_event_device *bc, *dev;
209	struct tick_device *td;
210	unsigned long flags, *reason = why;
211	int cpu;
212
213	spin_lock_irqsave(&tick_broadcast_lock, flags);
214
215	cpu = smp_processor_id();
216	td = &per_cpu(tick_cpu_device, cpu);
217	dev = td->evtdev;
218	bc = tick_broadcast_device.evtdev;
219
220	/*
221	 * Is the device in broadcast mode forever or is it not
222	 * affected by the powerstate ?
223	 */
224	if (!dev || !tick_device_is_functional(dev) ||
225	    !(dev->features & CLOCK_EVT_FEAT_C3STOP))
226		goto out;
227
228	if (*reason == CLOCK_EVT_NOTIFY_BROADCAST_ON) {
229		if (!cpu_isset(cpu, tick_broadcast_mask)) {
230			cpu_set(cpu, tick_broadcast_mask);
231			if (td->mode == TICKDEV_MODE_PERIODIC)
232				clockevents_set_mode(dev,
233						     CLOCK_EVT_MODE_SHUTDOWN);
234		}
235	} else {
236		if (cpu_isset(cpu, tick_broadcast_mask)) {
237			cpu_clear(cpu, tick_broadcast_mask);
238			if (td->mode == TICKDEV_MODE_PERIODIC)
239				tick_setup_periodic(dev, 0);
240		}
241	}
242
243	if (cpus_empty(tick_broadcast_mask))
244		clockevents_set_mode(bc, CLOCK_EVT_MODE_SHUTDOWN);
245	else {
246		if (tick_broadcast_device.mode == TICKDEV_MODE_PERIODIC)
247			tick_broadcast_start_periodic(bc);
248		else
249			tick_broadcast_setup_oneshot(bc);
250	}
251out:
252	spin_unlock_irqrestore(&tick_broadcast_lock, flags);
253}
254
255/*
256 * Powerstate information: The system enters/leaves a state, where
257 * affected devices might stop.
258 */
259void tick_broadcast_on_off(unsigned long reason, int *oncpu)
260{
261	int cpu = get_cpu();
262
263	if (!cpu_isset(*oncpu, cpu_online_map)) {
264		printk(KERN_ERR "tick-braodcast: ignoring broadcast for "
265		       "offline CPU #%d\n", *oncpu);
266	} else {
267
268		if (cpu == *oncpu)
269			tick_do_broadcast_on_off(&reason);
270		else
271			smp_call_function_single(*oncpu,
272						 tick_do_broadcast_on_off,
273						 &reason, 1, 1);
274	}
275	put_cpu();
276}
277
278/*
279 * Set the periodic handler depending on broadcast on/off
280 */
281void tick_set_periodic_handler(struct clock_event_device *dev, int broadcast)
282{
283	if (!broadcast)
284		dev->event_handler = tick_handle_periodic;
285	else
286		dev->event_handler = tick_handle_periodic_broadcast;
287}
288
289/*
290 * Remove a CPU from broadcasting
291 */
292void tick_shutdown_broadcast(unsigned int *cpup)
293{
294	struct clock_event_device *bc;
295	unsigned long flags;
296	unsigned int cpu = *cpup;
297
298	spin_lock_irqsave(&tick_broadcast_lock, flags);
299
300	bc = tick_broadcast_device.evtdev;
301	cpu_clear(cpu, tick_broadcast_mask);
302
303	if (tick_broadcast_device.mode == TICKDEV_MODE_PERIODIC) {
304		if (bc && cpus_empty(tick_broadcast_mask))
305			clockevents_set_mode(bc, CLOCK_EVT_MODE_SHUTDOWN);
306	}
307
308	spin_unlock_irqrestore(&tick_broadcast_lock, flags);
309}
310
311void tick_suspend_broadcast(void)
312{
313	struct clock_event_device *bc;
314	unsigned long flags;
315
316	spin_lock_irqsave(&tick_broadcast_lock, flags);
317
318	bc = tick_broadcast_device.evtdev;
319	if (bc)
320		clockevents_set_mode(bc, CLOCK_EVT_MODE_SHUTDOWN);
321
322	spin_unlock_irqrestore(&tick_broadcast_lock, flags);
323}
324
325int tick_resume_broadcast(void)
326{
327	struct clock_event_device *bc;
328	unsigned long flags;
329	int broadcast = 0;
330
331	spin_lock_irqsave(&tick_broadcast_lock, flags);
332
333	bc = tick_broadcast_device.evtdev;
334
335	if (bc) {
336		clockevents_set_mode(bc, CLOCK_EVT_MODE_RESUME);
337
338		switch (tick_broadcast_device.mode) {
339		case TICKDEV_MODE_PERIODIC:
340			if(!cpus_empty(tick_broadcast_mask))
341				tick_broadcast_start_periodic(bc);
342			broadcast = cpu_isset(smp_processor_id(),
343					      tick_broadcast_mask);
344			break;
345		case TICKDEV_MODE_ONESHOT:
346			broadcast = tick_resume_broadcast_oneshot(bc);
347			break;
348		}
349	}
350	spin_unlock_irqrestore(&tick_broadcast_lock, flags);
351
352	return broadcast;
353}
354
355
356#ifdef CONFIG_TICK_ONESHOT
357
358static cpumask_t tick_broadcast_oneshot_mask;
359
360/*
361 * Debugging: see timer_list.c
362 */
363cpumask_t *tick_get_broadcast_oneshot_mask(void)
364{
365	return &tick_broadcast_oneshot_mask;
366}
367
368static int tick_broadcast_set_event(ktime_t expires, int force)
369{
370	struct clock_event_device *bc = tick_broadcast_device.evtdev;
371	ktime_t now = ktime_get();
372	int res;
373
374	for(;;) {
375		res = clockevents_program_event(bc, expires, now);
376		if (!res || !force)
377			return res;
378		now = ktime_get();
379		expires = ktime_add(now, ktime_set(0, bc->min_delta_ns));
380	}
381}
382
383int tick_resume_broadcast_oneshot(struct clock_event_device *bc)
384{
385	clockevents_set_mode(bc, CLOCK_EVT_MODE_ONESHOT);
386	return 0;
387}
388
389/*
390 * Reprogram the broadcast device:
391 *
392 * Called with tick_broadcast_lock held and interrupts disabled.
393 */
394static int tick_broadcast_reprogram(void)
395{
396	ktime_t expires = { .tv64 = KTIME_MAX };
397	struct tick_device *td;
398	int cpu;
399
400	/*
401	 * Find the event which expires next:
402	 */
403	for (cpu = first_cpu(tick_broadcast_oneshot_mask); cpu != NR_CPUS;
404	     cpu = next_cpu(cpu, tick_broadcast_oneshot_mask)) {
405		td = &per_cpu(tick_cpu_device, cpu);
406		if (td->evtdev->next_event.tv64 < expires.tv64)
407			expires = td->evtdev->next_event;
408	}
409
410	if (expires.tv64 == KTIME_MAX)
411		return 0;
412
413	return tick_broadcast_set_event(expires, 0);
414}
415
416/*
417 * Handle oneshot mode broadcasting
418 */
419static void tick_handle_oneshot_broadcast(struct clock_event_device *dev)
420{
421	struct tick_device *td;
422	cpumask_t mask;
423	ktime_t now;
424	int cpu;
425
426	spin_lock(&tick_broadcast_lock);
427again:
428	dev->next_event.tv64 = KTIME_MAX;
429	mask = CPU_MASK_NONE;
430	now = ktime_get();
431	/* Find all expired events */
432	for (cpu = first_cpu(tick_broadcast_oneshot_mask); cpu != NR_CPUS;
433	     cpu = next_cpu(cpu, tick_broadcast_oneshot_mask)) {
434		td = &per_cpu(tick_cpu_device, cpu);
435		if (td->evtdev->next_event.tv64 <= now.tv64)
436			cpu_set(cpu, mask);
437	}
438
439	/*
440	 * Wakeup the cpus which have an expired event. The broadcast
441	 * device is reprogrammed in the return from idle code.
442	 */
443	if (!tick_do_broadcast(mask)) {
444		/*
445		 * The global event did not expire any CPU local
446		 * events. This happens in dyntick mode, as the
447		 * maximum PIT delta is quite small.
448		 */
449		if (tick_broadcast_reprogram())
450			goto again;
451	}
452	spin_unlock(&tick_broadcast_lock);
453}
454
455/*
456 * Powerstate information: The system enters/leaves a state, where
457 * affected devices might stop
458 */
459void tick_broadcast_oneshot_control(unsigned long reason)
460{
461	struct clock_event_device *bc, *dev;
462	struct tick_device *td;
463	unsigned long flags;
464	int cpu;
465
466	spin_lock_irqsave(&tick_broadcast_lock, flags);
467
468	/*
469	 * Periodic mode does not care about the enter/exit of power
470	 * states
471	 */
472	if (tick_broadcast_device.mode == TICKDEV_MODE_PERIODIC)
473		goto out;
474
475	bc = tick_broadcast_device.evtdev;
476	cpu = smp_processor_id();
477	td = &per_cpu(tick_cpu_device, cpu);
478	dev = td->evtdev;
479
480	if (!(dev->features & CLOCK_EVT_FEAT_C3STOP))
481		goto out;
482
483	if (reason == CLOCK_EVT_NOTIFY_BROADCAST_ENTER) {
484		if (!cpu_isset(cpu, tick_broadcast_oneshot_mask)) {
485			cpu_set(cpu, tick_broadcast_oneshot_mask);
486			clockevents_set_mode(dev, CLOCK_EVT_MODE_SHUTDOWN);
487			if (dev->next_event.tv64 < bc->next_event.tv64)
488				tick_broadcast_set_event(dev->next_event, 1);
489		}
490	} else {
491		if (cpu_isset(cpu, tick_broadcast_oneshot_mask)) {
492			cpu_clear(cpu, tick_broadcast_oneshot_mask);
493			clockevents_set_mode(dev, CLOCK_EVT_MODE_ONESHOT);
494			if (dev->next_event.tv64 != KTIME_MAX)
495				tick_program_event(dev->next_event, 1);
496		}
497	}
498
499out:
500	spin_unlock_irqrestore(&tick_broadcast_lock, flags);
501}
502
503/*
504 * Reset the one shot broadcast for a cpu
505 *
506 * Called with tick_broadcast_lock held
507 */
508static void tick_broadcast_clear_oneshot(int cpu)
509{
510	cpu_clear(cpu, tick_broadcast_oneshot_mask);
511}
512
513/**
514 * tick_broadcast_setup_highres - setup the broadcast device for highres
515 */
516void tick_broadcast_setup_oneshot(struct clock_event_device *bc)
517{
518	if (bc->mode != CLOCK_EVT_MODE_ONESHOT) {
519		bc->event_handler = tick_handle_oneshot_broadcast;
520		clockevents_set_mode(bc, CLOCK_EVT_MODE_ONESHOT);
521		bc->next_event.tv64 = KTIME_MAX;
522	}
523}
524
525/*
526 * Select oneshot operating mode for the broadcast device
527 */
528void tick_broadcast_switch_to_oneshot(void)
529{
530	struct clock_event_device *bc;
531	unsigned long flags;
532
533	spin_lock_irqsave(&tick_broadcast_lock, flags);
534
535	tick_broadcast_device.mode = TICKDEV_MODE_ONESHOT;
536	bc = tick_broadcast_device.evtdev;
537	if (bc)
538		tick_broadcast_setup_oneshot(bc);
539	spin_unlock_irqrestore(&tick_broadcast_lock, flags);
540}
541
542
543/*
544 * Remove a dead CPU from broadcasting
545 */
546void tick_shutdown_broadcast_oneshot(unsigned int *cpup)
547{
548	unsigned long flags;
549	unsigned int cpu = *cpup;
550
551	spin_lock_irqsave(&tick_broadcast_lock, flags);
552
553	/*
554	 * Clear the broadcast mask flag for the dead cpu, but do not
555	 * stop the broadcast device!
556	 */
557	cpu_clear(cpu, tick_broadcast_oneshot_mask);
558
559	spin_unlock_irqrestore(&tick_broadcast_lock, flags);
560}
561
562#endif
563