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_isset(*oncpu, cpu_online_map)) {
247		printk(KERN_ERR "tick-braodcast: ignoring broadcast for "
248		       "offline CPU #%d\n", *oncpu);
249	} else {
250
251		if (cpu == *oncpu)
252			tick_do_broadcast_on_off(&reason);
253		else
254			smp_call_function_single(*oncpu,
255						 tick_do_broadcast_on_off,
256						 &reason, 1, 1);
257	}
258	put_cpu();
259}
260
261/*
262 * Set the periodic handler depending on broadcast on/off
263 */
264void tick_set_periodic_handler(struct clock_event_device *dev, int broadcast)
265{
266	if (!broadcast)
267		dev->event_handler = tick_handle_periodic;
268	else
269		dev->event_handler = tick_handle_periodic_broadcast;
270}
271
272/*
273 * Remove a CPU from broadcasting
274 */
275void tick_shutdown_broadcast(unsigned int *cpup)
276{
277	struct clock_event_device *bc;
278	unsigned long flags;
279	unsigned int cpu = *cpup;
280
281	spin_lock_irqsave(&tick_broadcast_lock, flags);
282
283	bc = tick_broadcast_device.evtdev;
284	cpu_clear(cpu, tick_broadcast_mask);
285
286	if (tick_broadcast_device.mode == TICKDEV_MODE_PERIODIC) {
287		if (bc && cpus_empty(tick_broadcast_mask))
288			clockevents_set_mode(bc, CLOCK_EVT_MODE_SHUTDOWN);
289	}
290
291	spin_unlock_irqrestore(&tick_broadcast_lock, flags);
292}
293
294void tick_suspend_broadcast(void)
295{
296	struct clock_event_device *bc;
297	unsigned long flags;
298
299	spin_lock_irqsave(&tick_broadcast_lock, flags);
300
301	bc = tick_broadcast_device.evtdev;
302	if (bc && tick_broadcast_device.mode == TICKDEV_MODE_PERIODIC)
303		clockevents_set_mode(bc, CLOCK_EVT_MODE_SHUTDOWN);
304
305	spin_unlock_irqrestore(&tick_broadcast_lock, flags);
306}
307
308int tick_resume_broadcast(void)
309{
310	struct clock_event_device *bc;
311	unsigned long flags;
312	int broadcast = 0;
313
314	spin_lock_irqsave(&tick_broadcast_lock, flags);
315
316	bc = tick_broadcast_device.evtdev;
317
318	if (bc) {
319		switch (tick_broadcast_device.mode) {
320		case TICKDEV_MODE_PERIODIC:
321			if(!cpus_empty(tick_broadcast_mask))
322				tick_broadcast_start_periodic(bc);
323			broadcast = cpu_isset(smp_processor_id(),
324					      tick_broadcast_mask);
325			break;
326		case TICKDEV_MODE_ONESHOT:
327			broadcast = tick_resume_broadcast_oneshot(bc);
328			break;
329		}
330	}
331	spin_unlock_irqrestore(&tick_broadcast_lock, flags);
332
333	return broadcast;
334}
335
336
337#ifdef CONFIG_TICK_ONESHOT
338
339static cpumask_t tick_broadcast_oneshot_mask;
340
341/*
342 * Debugging: see timer_list.c
343 */
344cpumask_t *tick_get_broadcast_oneshot_mask(void)
345{
346	return &tick_broadcast_oneshot_mask;
347}
348
349static int tick_broadcast_set_event(ktime_t expires, int force)
350{
351	struct clock_event_device *bc = tick_broadcast_device.evtdev;
352	ktime_t now = ktime_get();
353	int res;
354
355	for(;;) {
356		res = clockevents_program_event(bc, expires, now);
357		if (!res || !force)
358			return res;
359		now = ktime_get();
360		expires = ktime_add(now, ktime_set(0, bc->min_delta_ns));
361	}
362}
363
364int tick_resume_broadcast_oneshot(struct clock_event_device *bc)
365{
366	clockevents_set_mode(bc, CLOCK_EVT_MODE_ONESHOT);
367
368	if(!cpus_empty(tick_broadcast_oneshot_mask))
369		tick_broadcast_set_event(ktime_get(), 1);
370
371	return cpu_isset(smp_processor_id(), tick_broadcast_oneshot_mask);
372}
373
374/*
375 * Reprogram the broadcast device:
376 *
377 * Called with tick_broadcast_lock held and interrupts disabled.
378 */
379static int tick_broadcast_reprogram(void)
380{
381	ktime_t expires = { .tv64 = KTIME_MAX };
382	struct tick_device *td;
383	int cpu;
384
385	/*
386	 * Find the event which expires next:
387	 */
388	for (cpu = first_cpu(tick_broadcast_oneshot_mask); cpu != NR_CPUS;
389	     cpu = next_cpu(cpu, tick_broadcast_oneshot_mask)) {
390		td = &per_cpu(tick_cpu_device, cpu);
391		if (td->evtdev->next_event.tv64 < expires.tv64)
392			expires = td->evtdev->next_event;
393	}
394
395	if (expires.tv64 == KTIME_MAX)
396		return 0;
397
398	return tick_broadcast_set_event(expires, 0);
399}
400
401/*
402 * Handle oneshot mode broadcasting
403 */
404static void tick_handle_oneshot_broadcast(struct clock_event_device *dev)
405{
406	struct tick_device *td;
407	cpumask_t mask;
408	ktime_t now;
409	int cpu;
410
411	spin_lock(&tick_broadcast_lock);
412again:
413	dev->next_event.tv64 = KTIME_MAX;
414	mask = CPU_MASK_NONE;
415	now = ktime_get();
416	/* Find all expired events */
417	for (cpu = first_cpu(tick_broadcast_oneshot_mask); cpu != NR_CPUS;
418	     cpu = next_cpu(cpu, tick_broadcast_oneshot_mask)) {
419		td = &per_cpu(tick_cpu_device, cpu);
420		if (td->evtdev->next_event.tv64 <= now.tv64)
421			cpu_set(cpu, mask);
422	}
423
424	/*
425	 * Wakeup the cpus which have an expired event. The broadcast
426	 * device is reprogrammed in the return from idle code.
427	 */
428	if (!tick_do_broadcast(mask)) {
429		/*
430		 * The global event did not expire any CPU local
431		 * events. This happens in dyntick mode, as the
432		 * maximum PIT delta is quite small.
433		 */
434		if (tick_broadcast_reprogram())
435			goto again;
436	}
437	spin_unlock(&tick_broadcast_lock);
438}
439
440/*
441 * Powerstate information: The system enters/leaves a state, where
442 * affected devices might stop
443 */
444void tick_broadcast_oneshot_control(unsigned long reason)
445{
446	struct clock_event_device *bc, *dev;
447	struct tick_device *td;
448	unsigned long flags;
449	int cpu;
450
451	spin_lock_irqsave(&tick_broadcast_lock, flags);
452
453	/*
454	 * Periodic mode does not care about the enter/exit of power
455	 * states
456	 */
457	if (tick_broadcast_device.mode == TICKDEV_MODE_PERIODIC)
458		goto out;
459
460	bc = tick_broadcast_device.evtdev;
461	cpu = smp_processor_id();
462	td = &per_cpu(tick_cpu_device, cpu);
463	dev = td->evtdev;
464
465	if (!(dev->features & CLOCK_EVT_FEAT_C3STOP))
466		goto out;
467
468	if (reason == CLOCK_EVT_NOTIFY_BROADCAST_ENTER) {
469		if (!cpu_isset(cpu, tick_broadcast_oneshot_mask)) {
470			cpu_set(cpu, tick_broadcast_oneshot_mask);
471			clockevents_set_mode(dev, CLOCK_EVT_MODE_SHUTDOWN);
472			if (dev->next_event.tv64 < bc->next_event.tv64)
473				tick_broadcast_set_event(dev->next_event, 1);
474		}
475	} else {
476		if (cpu_isset(cpu, tick_broadcast_oneshot_mask)) {
477			cpu_clear(cpu, tick_broadcast_oneshot_mask);
478			clockevents_set_mode(dev, CLOCK_EVT_MODE_ONESHOT);
479			if (dev->next_event.tv64 != KTIME_MAX)
480				tick_program_event(dev->next_event, 1);
481		}
482	}
483
484out:
485	spin_unlock_irqrestore(&tick_broadcast_lock, flags);
486}
487
488/**
489 * tick_broadcast_setup_highres - setup the broadcast device for highres
490 */
491void tick_broadcast_setup_oneshot(struct clock_event_device *bc)
492{
493	if (bc->mode != CLOCK_EVT_MODE_ONESHOT) {
494		bc->event_handler = tick_handle_oneshot_broadcast;
495		clockevents_set_mode(bc, CLOCK_EVT_MODE_ONESHOT);
496		bc->next_event.tv64 = KTIME_MAX;
497	}
498}
499
500/*
501 * Select oneshot operating mode for the broadcast device
502 */
503void tick_broadcast_switch_to_oneshot(void)
504{
505	struct clock_event_device *bc;
506	unsigned long flags;
507
508	spin_lock_irqsave(&tick_broadcast_lock, flags);
509
510	tick_broadcast_device.mode = TICKDEV_MODE_ONESHOT;
511	bc = tick_broadcast_device.evtdev;
512	if (bc)
513		tick_broadcast_setup_oneshot(bc);
514	spin_unlock_irqrestore(&tick_broadcast_lock, flags);
515}
516
517
518/*
519 * Remove a dead CPU from broadcasting
520 */
521void tick_shutdown_broadcast_oneshot(unsigned int *cpup)
522{
523	struct clock_event_device *bc;
524	unsigned long flags;
525	unsigned int cpu = *cpup;
526
527	spin_lock_irqsave(&tick_broadcast_lock, flags);
528
529	bc = tick_broadcast_device.evtdev;
530	cpu_clear(cpu, tick_broadcast_oneshot_mask);
531
532	if (tick_broadcast_device.mode == TICKDEV_MODE_ONESHOT) {
533		if (bc && cpus_empty(tick_broadcast_oneshot_mask))
534			clockevents_set_mode(bc, CLOCK_EVT_MODE_SHUTDOWN);
535	}
536
537	spin_unlock_irqrestore(&tick_broadcast_lock, flags);
538}
539
540#endif
541