tick-broadcast.c revision 6321dd60c76b2e12383bc06046288b15397ed3a0 
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/*
35 * Debugging: see timer_list.c
36 */
37struct tick_device *tick_get_broadcast_device(void)
38{
39	return &tick_broadcast_device;
40}
41
42cpumask_t *tick_get_broadcast_mask(void)
43{
44	return &tick_broadcast_mask;
45}
46
47/*
48 * Start the device in periodic mode
49 */
50static void tick_broadcast_start_periodic(struct clock_event_device *bc)
51{
52	if (bc && bc->mode == CLOCK_EVT_MODE_SHUTDOWN)
53		tick_setup_periodic(bc, 1);
54}
55
56/*
57 * Check, if the device can be utilized as broadcast device:
58 */
59int tick_check_broadcast_device(struct clock_event_device *dev)
60{
61	if (tick_broadcast_device.evtdev ||
62	    (dev->features & CLOCK_EVT_FEAT_C3STOP))
63		return 0;
64
65	clockevents_exchange_device(NULL, dev);
66	tick_broadcast_device.evtdev = dev;
67	if (!cpus_empty(tick_broadcast_mask))
68		tick_broadcast_start_periodic(dev);
69	return 1;
70}
71
72/*
73 * Check, if the device is the broadcast device
74 */
75int tick_is_broadcast_device(struct clock_event_device *dev)
76{
77	return (dev && tick_broadcast_device.evtdev == dev);
78}
79
80/*
81 * Check, if the device is disfunctional and a place holder, which
82 * needs to be handled by the broadcast device.
83 */
84int tick_device_uses_broadcast(struct clock_event_device *dev, int cpu)
85{
86	unsigned long flags;
87	int ret = 0;
88
89	spin_lock_irqsave(&tick_broadcast_lock, flags);
90
91	/*
92	 * Devices might be registered with both periodic and oneshot
93	 * mode disabled. This signals, that the device needs to be
94	 * operated from the broadcast device and is a placeholder for
95	 * the cpu local device.
96	 */
97	if (!tick_device_is_functional(dev)) {
98		dev->event_handler = tick_handle_periodic;
99		cpu_set(cpu, tick_broadcast_mask);
100		tick_broadcast_start_periodic(tick_broadcast_device.evtdev);
101		ret = 1;
102	}
103
104	spin_unlock_irqrestore(&tick_broadcast_lock, flags);
105	return ret;
106}
107
108/*
109 * Broadcast the event to the cpus, which are set in the mask
110 */
111int tick_do_broadcast(cpumask_t mask)
112{
113	int ret = 0, cpu = smp_processor_id();
114	struct tick_device *td;
115
116	/*
117	 * Check, if the current cpu is in the mask
118	 */
119	if (cpu_isset(cpu, mask)) {
120		cpu_clear(cpu, mask);
121		td = &per_cpu(tick_cpu_device, cpu);
122		td->evtdev->event_handler(td->evtdev);
123		ret = 1;
124	}
125
126	if (!cpus_empty(mask)) {
127		/*
128		 * It might be necessary to actually check whether the devices
129		 * have different broadcast functions. For now, just use the
130		 * one of the first device. This works as long as we have this
131		 * misfeature only on x86 (lapic)
132		 */
133		cpu = first_cpu(mask);
134		td = &per_cpu(tick_cpu_device, cpu);
135		td->evtdev->broadcast(mask);
136		ret = 1;
137	}
138	return ret;
139}
140
141/*
142 * Periodic broadcast:
143 * - invoke the broadcast handlers
144 */
145static void tick_do_periodic_broadcast(void)
146{
147	cpumask_t mask;
148
149	spin_lock(&tick_broadcast_lock);
150
151	cpus_and(mask, cpu_online_map, tick_broadcast_mask);
152	tick_do_broadcast(mask);
153
154	spin_unlock(&tick_broadcast_lock);
155}
156
157/*
158 * Event handler for periodic broadcast ticks
159 */
160static void tick_handle_periodic_broadcast(struct clock_event_device *dev)
161{
162	dev->next_event.tv64 = KTIME_MAX;
163
164	tick_do_periodic_broadcast();
165
166	/*
167	 * The device is in periodic mode. No reprogramming necessary:
168	 */
169	if (dev->mode == CLOCK_EVT_MODE_PERIODIC)
170		return;
171
172	/*
173	 * Setup the next period for devices, which do not have
174	 * periodic mode:
175	 */
176	for (;;) {
177		ktime_t next = ktime_add(dev->next_event, tick_period);
178
179		if (!clockevents_program_event(dev, next, ktime_get()))
180			return;
181		tick_do_periodic_broadcast();
182	}
183}
184
185/*
186 * Powerstate information: The system enters/leaves a state, where
187 * affected devices might stop
188 */
189static void tick_do_broadcast_on_off(void *why)
190{
191	struct clock_event_device *bc, *dev;
192	struct tick_device *td;
193	unsigned long flags, *reason = why;
194	int cpu;
195
196	spin_lock_irqsave(&tick_broadcast_lock, flags);
197
198	cpu = smp_processor_id();
199	td = &per_cpu(tick_cpu_device, cpu);
200	dev = td->evtdev;
201	bc = tick_broadcast_device.evtdev;
202
203	/*
204	 * Is the device in broadcast mode forever or is it not
205	 * affected by the powerstate ?
206	 */
207	if (!dev || !tick_device_is_functional(dev) ||
208	    !(dev->features & CLOCK_EVT_FEAT_C3STOP))
209		goto out;
210
211	if (*reason == CLOCK_EVT_NOTIFY_BROADCAST_ON) {
212		if (!cpu_isset(cpu, tick_broadcast_mask)) {
213			cpu_set(cpu, tick_broadcast_mask);
214			if (td->mode == TICKDEV_MODE_PERIODIC)
215				clockevents_set_mode(dev,
216						     CLOCK_EVT_MODE_SHUTDOWN);
217		}
218	} else {
219		if (cpu_isset(cpu, tick_broadcast_mask)) {
220			cpu_clear(cpu, tick_broadcast_mask);
221			if (td->mode == TICKDEV_MODE_PERIODIC)
222				tick_setup_periodic(dev, 0);
223		}
224	}
225
226	if (cpus_empty(tick_broadcast_mask))
227		clockevents_set_mode(bc, CLOCK_EVT_MODE_SHUTDOWN);
228	else {
229		if (tick_broadcast_device.mode == TICKDEV_MODE_PERIODIC)
230			tick_broadcast_start_periodic(bc);
231		else
232			tick_broadcast_setup_oneshot(bc);
233	}
234out:
235	spin_unlock_irqrestore(&tick_broadcast_lock, flags);
236}
237
238/*
239 * Powerstate information: The system enters/leaves a state, where
240 * affected devices might stop.
241 */
242void tick_broadcast_on_off(unsigned long reason, int *oncpu)
243{
244	int cpu = get_cpu();
245
246	if (cpu == *oncpu)
247		tick_do_broadcast_on_off(&reason);
248	else
249		smp_call_function_single(*oncpu, tick_do_broadcast_on_off,
250					 &reason, 1, 1);
251	put_cpu();
252}
253
254/*
255 * Set the periodic handler depending on broadcast on/off
256 */
257void tick_set_periodic_handler(struct clock_event_device *dev, int broadcast)
258{
259	if (!broadcast)
260		dev->event_handler = tick_handle_periodic;
261	else
262		dev->event_handler = tick_handle_periodic_broadcast;
263}
264
265/*
266 * Remove a CPU from broadcasting
267 */
268void tick_shutdown_broadcast(unsigned int *cpup)
269{
270	struct clock_event_device *bc;
271	unsigned long flags;
272	unsigned int cpu = *cpup;
273
274	spin_lock_irqsave(&tick_broadcast_lock, flags);
275
276	bc = tick_broadcast_device.evtdev;
277	cpu_clear(cpu, tick_broadcast_mask);
278
279	if (tick_broadcast_device.mode == TICKDEV_MODE_PERIODIC) {
280		if (bc && cpus_empty(tick_broadcast_mask))
281			clockevents_set_mode(bc, CLOCK_EVT_MODE_SHUTDOWN);
282	}
283
284	spin_unlock_irqrestore(&tick_broadcast_lock, flags);
285}
286
287void tick_suspend_broadcast(void)
288{
289	struct clock_event_device *bc;
290	unsigned long flags;
291
292	spin_lock_irqsave(&tick_broadcast_lock, flags);
293
294	bc = tick_broadcast_device.evtdev;
295	if (bc && tick_broadcast_device.mode == TICKDEV_MODE_PERIODIC)
296		clockevents_set_mode(bc, CLOCK_EVT_MODE_SHUTDOWN);
297
298	spin_unlock_irqrestore(&tick_broadcast_lock, flags);
299}
300
301int tick_resume_broadcast(void)
302{
303	struct clock_event_device *bc;
304	unsigned long flags;
305	int broadcast = 0;
306
307	spin_lock_irqsave(&tick_broadcast_lock, flags);
308
309	bc = tick_broadcast_device.evtdev;
310	if (bc) {
311		if (tick_broadcast_device.mode == TICKDEV_MODE_PERIODIC &&
312		    !cpus_empty(tick_broadcast_mask))
313			tick_broadcast_start_periodic(bc);
314
315		broadcast = cpu_isset(smp_processor_id(), tick_broadcast_mask);
316	}
317	spin_unlock_irqrestore(&tick_broadcast_lock, flags);
318
319	return broadcast;
320}
321
322
323#ifdef CONFIG_TICK_ONESHOT
324
325static cpumask_t tick_broadcast_oneshot_mask;
326
327/*
328 * Debugging: see timer_list.c
329 */
330cpumask_t *tick_get_broadcast_oneshot_mask(void)
331{
332	return &tick_broadcast_oneshot_mask;
333}
334
335static int tick_broadcast_set_event(ktime_t expires, int force)
336{
337	struct clock_event_device *bc = tick_broadcast_device.evtdev;
338	ktime_t now = ktime_get();
339	int res;
340
341	for(;;) {
342		res = clockevents_program_event(bc, expires, now);
343		if (!res || !force)
344			return res;
345		now = ktime_get();
346		expires = ktime_add(now, ktime_set(0, bc->min_delta_ns));
347	}
348}
349
350/*
351 * Reprogram the broadcast device:
352 *
353 * Called with tick_broadcast_lock held and interrupts disabled.
354 */
355static int tick_broadcast_reprogram(void)
356{
357	ktime_t expires = { .tv64 = KTIME_MAX };
358	struct tick_device *td;
359	int cpu;
360
361	/*
362	 * Find the event which expires next:
363	 */
364	for (cpu = first_cpu(tick_broadcast_oneshot_mask); cpu != NR_CPUS;
365	     cpu = next_cpu(cpu, tick_broadcast_oneshot_mask)) {
366		td = &per_cpu(tick_cpu_device, cpu);
367		if (td->evtdev->next_event.tv64 < expires.tv64)
368			expires = td->evtdev->next_event;
369	}
370
371	if (expires.tv64 == KTIME_MAX)
372		return 0;
373
374	return tick_broadcast_set_event(expires, 0);
375}
376
377/*
378 * Handle oneshot mode broadcasting
379 */
380static void tick_handle_oneshot_broadcast(struct clock_event_device *dev)
381{
382	struct tick_device *td;
383	cpumask_t mask;
384	ktime_t now;
385	int cpu;
386
387	spin_lock(&tick_broadcast_lock);
388again:
389	dev->next_event.tv64 = KTIME_MAX;
390	mask = CPU_MASK_NONE;
391	now = ktime_get();
392	/* Find all expired events */
393	for (cpu = first_cpu(tick_broadcast_oneshot_mask); cpu != NR_CPUS;
394	     cpu = next_cpu(cpu, tick_broadcast_oneshot_mask)) {
395		td = &per_cpu(tick_cpu_device, cpu);
396		if (td->evtdev->next_event.tv64 <= now.tv64)
397			cpu_set(cpu, mask);
398	}
399
400	/*
401	 * Wakeup the cpus which have an expired event. The broadcast
402	 * device is reprogrammed in the return from idle code.
403	 */
404	if (!tick_do_broadcast(mask)) {
405		/*
406		 * The global event did not expire any CPU local
407		 * events. This happens in dyntick mode, as the
408		 * maximum PIT delta is quite small.
409		 */
410		if (tick_broadcast_reprogram())
411			goto again;
412	}
413	spin_unlock(&tick_broadcast_lock);
414}
415
416/*
417 * Powerstate information: The system enters/leaves a state, where
418 * affected devices might stop
419 */
420void tick_broadcast_oneshot_control(unsigned long reason)
421{
422	struct clock_event_device *bc, *dev;
423	struct tick_device *td;
424	unsigned long flags;
425	int cpu;
426
427	spin_lock_irqsave(&tick_broadcast_lock, flags);
428
429	/*
430	 * Periodic mode does not care about the enter/exit of power
431	 * states
432	 */
433	if (tick_broadcast_device.mode == TICKDEV_MODE_PERIODIC)
434		goto out;
435
436	bc = tick_broadcast_device.evtdev;
437	cpu = smp_processor_id();
438	td = &per_cpu(tick_cpu_device, cpu);
439	dev = td->evtdev;
440
441	if (!(dev->features & CLOCK_EVT_FEAT_C3STOP))
442		goto out;
443
444	if (reason == CLOCK_EVT_NOTIFY_BROADCAST_ENTER) {
445		if (!cpu_isset(cpu, tick_broadcast_oneshot_mask)) {
446			cpu_set(cpu, tick_broadcast_oneshot_mask);
447			clockevents_set_mode(dev, CLOCK_EVT_MODE_SHUTDOWN);
448			if (dev->next_event.tv64 < bc->next_event.tv64)
449				tick_broadcast_set_event(dev->next_event, 1);
450		}
451	} else {
452		if (cpu_isset(cpu, tick_broadcast_oneshot_mask)) {
453			cpu_clear(cpu, tick_broadcast_oneshot_mask);
454			clockevents_set_mode(dev, CLOCK_EVT_MODE_ONESHOT);
455			if (dev->next_event.tv64 != KTIME_MAX)
456				tick_program_event(dev->next_event, 1);
457		}
458	}
459
460out:
461	spin_unlock_irqrestore(&tick_broadcast_lock, flags);
462}
463
464/**
465 * tick_broadcast_setup_highres - setup the broadcast device for highres
466 */
467void tick_broadcast_setup_oneshot(struct clock_event_device *bc)
468{
469	if (bc->mode != CLOCK_EVT_MODE_ONESHOT) {
470		bc->event_handler = tick_handle_oneshot_broadcast;
471		clockevents_set_mode(bc, CLOCK_EVT_MODE_ONESHOT);
472		bc->next_event.tv64 = KTIME_MAX;
473	}
474}
475
476/*
477 * Select oneshot operating mode for the broadcast device
478 */
479void tick_broadcast_switch_to_oneshot(void)
480{
481	struct clock_event_device *bc;
482	unsigned long flags;
483
484	spin_lock_irqsave(&tick_broadcast_lock, flags);
485
486	tick_broadcast_device.mode = TICKDEV_MODE_ONESHOT;
487	bc = tick_broadcast_device.evtdev;
488	if (bc)
489		tick_broadcast_setup_oneshot(bc);
490	spin_unlock_irqrestore(&tick_broadcast_lock, flags);
491}
492
493
494/*
495 * Remove a dead CPU from broadcasting
496 */
497void tick_shutdown_broadcast_oneshot(unsigned int *cpup)
498{
499	struct clock_event_device *bc;
500	unsigned long flags;
501	unsigned int cpu = *cpup;
502
503	spin_lock_irqsave(&tick_broadcast_lock, flags);
504
505	bc = tick_broadcast_device.evtdev;
506	cpu_clear(cpu, tick_broadcast_oneshot_mask);
507
508	if (tick_broadcast_device.mode == TICKDEV_MODE_ONESHOT) {
509		if (bc && cpus_empty(tick_broadcast_oneshot_mask))
510			clockevents_set_mode(bc, CLOCK_EVT_MODE_SHUTDOWN);
511	}
512
513	spin_unlock_irqrestore(&tick_broadcast_lock, flags);
514}
515
516#endif
517