xref: /linux/kernel/time/clockevents.c (revision 36ec807b627b4c0a0a382f0ae48eac7187d14b2b)
1 // SPDX-License-Identifier: GPL-2.0
2 /*
3  * This file contains functions which manage clock event devices.
4  *
5  * Copyright(C) 2005-2006, Thomas Gleixner <tglx@linutronix.de>
6  * Copyright(C) 2005-2007, Red Hat, Inc., Ingo Molnar
7  * Copyright(C) 2006-2007, Timesys Corp., Thomas Gleixner
8  */
9 
10 #include <linux/clockchips.h>
11 #include <linux/hrtimer.h>
12 #include <linux/init.h>
13 #include <linux/module.h>
14 #include <linux/smp.h>
15 #include <linux/device.h>
16 
17 #include "tick-internal.h"
18 
19 /* The registered clock event devices */
20 static LIST_HEAD(clockevent_devices);
21 static LIST_HEAD(clockevents_released);
22 /* Protection for the above */
23 static DEFINE_RAW_SPINLOCK(clockevents_lock);
24 /* Protection for unbind operations */
25 static DEFINE_MUTEX(clockevents_mutex);
26 
27 struct ce_unbind {
28 	struct clock_event_device *ce;
29 	int res;
30 };
31 
32 static u64 cev_delta2ns(unsigned long latch, struct clock_event_device *evt,
33 			bool ismax)
34 {
35 	u64 clc = (u64) latch << evt->shift;
36 	u64 rnd;
37 
38 	if (WARN_ON(!evt->mult))
39 		evt->mult = 1;
40 	rnd = (u64) evt->mult - 1;
41 
42 	/*
43 	 * Upper bound sanity check. If the backwards conversion is
44 	 * not equal latch, we know that the above shift overflowed.
45 	 */
46 	if ((clc >> evt->shift) != (u64)latch)
47 		clc = ~0ULL;
48 
49 	/*
50 	 * Scaled math oddities:
51 	 *
52 	 * For mult <= (1 << shift) we can safely add mult - 1 to
53 	 * prevent integer rounding loss. So the backwards conversion
54 	 * from nsec to device ticks will be correct.
55 	 *
56 	 * For mult > (1 << shift), i.e. device frequency is > 1GHz we
57 	 * need to be careful. Adding mult - 1 will result in a value
58 	 * which when converted back to device ticks can be larger
59 	 * than latch by up to (mult - 1) >> shift. For the min_delta
60 	 * calculation we still want to apply this in order to stay
61 	 * above the minimum device ticks limit. For the upper limit
62 	 * we would end up with a latch value larger than the upper
63 	 * limit of the device, so we omit the add to stay below the
64 	 * device upper boundary.
65 	 *
66 	 * Also omit the add if it would overflow the u64 boundary.
67 	 */
68 	if ((~0ULL - clc > rnd) &&
69 	    (!ismax || evt->mult <= (1ULL << evt->shift)))
70 		clc += rnd;
71 
72 	do_div(clc, evt->mult);
73 
74 	/* Deltas less than 1usec are pointless noise */
75 	return clc > 1000 ? clc : 1000;
76 }
77 
78 /**
79  * clockevent_delta2ns - Convert a latch value (device ticks) to nanoseconds
80  * @latch:	value to convert
81  * @evt:	pointer to clock event device descriptor
82  *
83  * Math helper, returns latch value converted to nanoseconds (bound checked)
84  */
85 u64 clockevent_delta2ns(unsigned long latch, struct clock_event_device *evt)
86 {
87 	return cev_delta2ns(latch, evt, false);
88 }
89 EXPORT_SYMBOL_GPL(clockevent_delta2ns);
90 
91 static int __clockevents_switch_state(struct clock_event_device *dev,
92 				      enum clock_event_state state)
93 {
94 	if (dev->features & CLOCK_EVT_FEAT_DUMMY)
95 		return 0;
96 
97 	/* Transition with new state-specific callbacks */
98 	switch (state) {
99 	case CLOCK_EVT_STATE_DETACHED:
100 		/* The clockevent device is getting replaced. Shut it down. */
101 
102 	case CLOCK_EVT_STATE_SHUTDOWN:
103 		if (dev->set_state_shutdown)
104 			return dev->set_state_shutdown(dev);
105 		return 0;
106 
107 	case CLOCK_EVT_STATE_PERIODIC:
108 		/* Core internal bug */
109 		if (!(dev->features & CLOCK_EVT_FEAT_PERIODIC))
110 			return -ENOSYS;
111 		if (dev->set_state_periodic)
112 			return dev->set_state_periodic(dev);
113 		return 0;
114 
115 	case CLOCK_EVT_STATE_ONESHOT:
116 		/* Core internal bug */
117 		if (!(dev->features & CLOCK_EVT_FEAT_ONESHOT))
118 			return -ENOSYS;
119 		if (dev->set_state_oneshot)
120 			return dev->set_state_oneshot(dev);
121 		return 0;
122 
123 	case CLOCK_EVT_STATE_ONESHOT_STOPPED:
124 		/* Core internal bug */
125 		if (WARN_ONCE(!clockevent_state_oneshot(dev),
126 			      "Current state: %d\n",
127 			      clockevent_get_state(dev)))
128 			return -EINVAL;
129 
130 		if (dev->set_state_oneshot_stopped)
131 			return dev->set_state_oneshot_stopped(dev);
132 		else
133 			return -ENOSYS;
134 
135 	default:
136 		return -ENOSYS;
137 	}
138 }
139 
140 /**
141  * clockevents_switch_state - set the operating state of a clock event device
142  * @dev:	device to modify
143  * @state:	new state
144  *
145  * Must be called with interrupts disabled !
146  */
147 void clockevents_switch_state(struct clock_event_device *dev,
148 			      enum clock_event_state state)
149 {
150 	if (clockevent_get_state(dev) != state) {
151 		if (__clockevents_switch_state(dev, state))
152 			return;
153 
154 		clockevent_set_state(dev, state);
155 
156 		/*
157 		 * A nsec2cyc multiplicator of 0 is invalid and we'd crash
158 		 * on it, so fix it up and emit a warning:
159 		 */
160 		if (clockevent_state_oneshot(dev)) {
161 			if (WARN_ON(!dev->mult))
162 				dev->mult = 1;
163 		}
164 	}
165 }
166 
167 /**
168  * clockevents_shutdown - shutdown the device and clear next_event
169  * @dev:	device to shutdown
170  */
171 void clockevents_shutdown(struct clock_event_device *dev)
172 {
173 	clockevents_switch_state(dev, CLOCK_EVT_STATE_SHUTDOWN);
174 	dev->next_event = KTIME_MAX;
175 }
176 
177 /**
178  * clockevents_tick_resume -	Resume the tick device before using it again
179  * @dev:			device to resume
180  */
181 int clockevents_tick_resume(struct clock_event_device *dev)
182 {
183 	int ret = 0;
184 
185 	if (dev->tick_resume)
186 		ret = dev->tick_resume(dev);
187 
188 	return ret;
189 }
190 
191 #ifdef CONFIG_GENERIC_CLOCKEVENTS_MIN_ADJUST
192 
193 /* Limit min_delta to a jiffie */
194 #define MIN_DELTA_LIMIT		(NSEC_PER_SEC / HZ)
195 
196 /**
197  * clockevents_increase_min_delta - raise minimum delta of a clock event device
198  * @dev:       device to increase the minimum delta
199  *
200  * Returns 0 on success, -ETIME when the minimum delta reached the limit.
201  */
202 static int clockevents_increase_min_delta(struct clock_event_device *dev)
203 {
204 	/* Nothing to do if we already reached the limit */
205 	if (dev->min_delta_ns >= MIN_DELTA_LIMIT) {
206 		printk_deferred(KERN_WARNING
207 				"CE: Reprogramming failure. Giving up\n");
208 		dev->next_event = KTIME_MAX;
209 		return -ETIME;
210 	}
211 
212 	if (dev->min_delta_ns < 5000)
213 		dev->min_delta_ns = 5000;
214 	else
215 		dev->min_delta_ns += dev->min_delta_ns >> 1;
216 
217 	if (dev->min_delta_ns > MIN_DELTA_LIMIT)
218 		dev->min_delta_ns = MIN_DELTA_LIMIT;
219 
220 	printk_deferred(KERN_WARNING
221 			"CE: %s increased min_delta_ns to %llu nsec\n",
222 			dev->name ? dev->name : "?",
223 			(unsigned long long) dev->min_delta_ns);
224 	return 0;
225 }
226 
227 /**
228  * clockevents_program_min_delta - Set clock event device to the minimum delay.
229  * @dev:	device to program
230  *
231  * Returns 0 on success, -ETIME when the retry loop failed.
232  */
233 static int clockevents_program_min_delta(struct clock_event_device *dev)
234 {
235 	unsigned long long clc;
236 	int64_t delta;
237 	int i;
238 
239 	for (i = 0;;) {
240 		delta = dev->min_delta_ns;
241 		dev->next_event = ktime_add_ns(ktime_get(), delta);
242 
243 		if (clockevent_state_shutdown(dev))
244 			return 0;
245 
246 		dev->retries++;
247 		clc = ((unsigned long long) delta * dev->mult) >> dev->shift;
248 		if (dev->set_next_event((unsigned long) clc, dev) == 0)
249 			return 0;
250 
251 		if (++i > 2) {
252 			/*
253 			 * We tried 3 times to program the device with the
254 			 * given min_delta_ns. Try to increase the minimum
255 			 * delta, if that fails as well get out of here.
256 			 */
257 			if (clockevents_increase_min_delta(dev))
258 				return -ETIME;
259 			i = 0;
260 		}
261 	}
262 }
263 
264 #else  /* CONFIG_GENERIC_CLOCKEVENTS_MIN_ADJUST */
265 
266 /**
267  * clockevents_program_min_delta - Set clock event device to the minimum delay.
268  * @dev:	device to program
269  *
270  * Returns 0 on success, -ETIME when the retry loop failed.
271  */
272 static int clockevents_program_min_delta(struct clock_event_device *dev)
273 {
274 	unsigned long long clc;
275 	int64_t delta = 0;
276 	int i;
277 
278 	for (i = 0; i < 10; i++) {
279 		delta += dev->min_delta_ns;
280 		dev->next_event = ktime_add_ns(ktime_get(), delta);
281 
282 		if (clockevent_state_shutdown(dev))
283 			return 0;
284 
285 		dev->retries++;
286 		clc = ((unsigned long long) delta * dev->mult) >> dev->shift;
287 		if (dev->set_next_event((unsigned long) clc, dev) == 0)
288 			return 0;
289 	}
290 	return -ETIME;
291 }
292 
293 #endif /* CONFIG_GENERIC_CLOCKEVENTS_MIN_ADJUST */
294 
295 /**
296  * clockevents_program_event - Reprogram the clock event device.
297  * @dev:	device to program
298  * @expires:	absolute expiry time (monotonic clock)
299  * @force:	program minimum delay if expires can not be set
300  *
301  * Returns 0 on success, -ETIME when the event is in the past.
302  */
303 int clockevents_program_event(struct clock_event_device *dev, ktime_t expires,
304 			      bool force)
305 {
306 	unsigned long long clc;
307 	int64_t delta;
308 	int rc;
309 
310 	if (WARN_ON_ONCE(expires < 0))
311 		return -ETIME;
312 
313 	dev->next_event = expires;
314 
315 	if (clockevent_state_shutdown(dev))
316 		return 0;
317 
318 	/* We must be in ONESHOT state here */
319 	WARN_ONCE(!clockevent_state_oneshot(dev), "Current state: %d\n",
320 		  clockevent_get_state(dev));
321 
322 	/* Shortcut for clockevent devices that can deal with ktime. */
323 	if (dev->features & CLOCK_EVT_FEAT_KTIME)
324 		return dev->set_next_ktime(expires, dev);
325 
326 	delta = ktime_to_ns(ktime_sub(expires, ktime_get()));
327 	if (delta <= 0)
328 		return force ? clockevents_program_min_delta(dev) : -ETIME;
329 
330 	delta = min(delta, (int64_t) dev->max_delta_ns);
331 	delta = max(delta, (int64_t) dev->min_delta_ns);
332 
333 	clc = ((unsigned long long) delta * dev->mult) >> dev->shift;
334 	rc = dev->set_next_event((unsigned long) clc, dev);
335 
336 	return (rc && force) ? clockevents_program_min_delta(dev) : rc;
337 }
338 
339 /*
340  * Called after a notify add to make devices available which were
341  * released from the notifier call.
342  */
343 static void clockevents_notify_released(void)
344 {
345 	struct clock_event_device *dev;
346 
347 	while (!list_empty(&clockevents_released)) {
348 		dev = list_entry(clockevents_released.next,
349 				 struct clock_event_device, list);
350 		list_move(&dev->list, &clockevent_devices);
351 		tick_check_new_device(dev);
352 	}
353 }
354 
355 /*
356  * Try to install a replacement clock event device
357  */
358 static int clockevents_replace(struct clock_event_device *ced)
359 {
360 	struct clock_event_device *dev, *newdev = NULL;
361 
362 	list_for_each_entry(dev, &clockevent_devices, list) {
363 		if (dev == ced || !clockevent_state_detached(dev))
364 			continue;
365 
366 		if (!tick_check_replacement(newdev, dev))
367 			continue;
368 
369 		if (!try_module_get(dev->owner))
370 			continue;
371 
372 		if (newdev)
373 			module_put(newdev->owner);
374 		newdev = dev;
375 	}
376 	if (newdev) {
377 		tick_install_replacement(newdev);
378 		list_del_init(&ced->list);
379 	}
380 	return newdev ? 0 : -EBUSY;
381 }
382 
383 /*
384  * Called with clockevents_mutex and clockevents_lock held
385  */
386 static int __clockevents_try_unbind(struct clock_event_device *ced, int cpu)
387 {
388 	/* Fast track. Device is unused */
389 	if (clockevent_state_detached(ced)) {
390 		list_del_init(&ced->list);
391 		return 0;
392 	}
393 
394 	return ced == per_cpu(tick_cpu_device, cpu).evtdev ? -EAGAIN : -EBUSY;
395 }
396 
397 /*
398  * SMP function call to unbind a device
399  */
400 static void __clockevents_unbind(void *arg)
401 {
402 	struct ce_unbind *cu = arg;
403 	int res;
404 
405 	raw_spin_lock(&clockevents_lock);
406 	res = __clockevents_try_unbind(cu->ce, smp_processor_id());
407 	if (res == -EAGAIN)
408 		res = clockevents_replace(cu->ce);
409 	cu->res = res;
410 	raw_spin_unlock(&clockevents_lock);
411 }
412 
413 /*
414  * Issues smp function call to unbind a per cpu device. Called with
415  * clockevents_mutex held.
416  */
417 static int clockevents_unbind(struct clock_event_device *ced, int cpu)
418 {
419 	struct ce_unbind cu = { .ce = ced, .res = -ENODEV };
420 
421 	smp_call_function_single(cpu, __clockevents_unbind, &cu, 1);
422 	return cu.res;
423 }
424 
425 /*
426  * Unbind a clockevents device.
427  */
428 int clockevents_unbind_device(struct clock_event_device *ced, int cpu)
429 {
430 	int ret;
431 
432 	mutex_lock(&clockevents_mutex);
433 	ret = clockevents_unbind(ced, cpu);
434 	mutex_unlock(&clockevents_mutex);
435 	return ret;
436 }
437 EXPORT_SYMBOL_GPL(clockevents_unbind_device);
438 
439 /**
440  * clockevents_register_device - register a clock event device
441  * @dev:	device to register
442  */
443 void clockevents_register_device(struct clock_event_device *dev)
444 {
445 	unsigned long flags;
446 
447 	/* Initialize state to DETACHED */
448 	clockevent_set_state(dev, CLOCK_EVT_STATE_DETACHED);
449 
450 	if (!dev->cpumask) {
451 		WARN_ON(num_possible_cpus() > 1);
452 		dev->cpumask = cpumask_of(smp_processor_id());
453 	}
454 
455 	if (dev->cpumask == cpu_all_mask) {
456 		WARN(1, "%s cpumask == cpu_all_mask, using cpu_possible_mask instead\n",
457 		     dev->name);
458 		dev->cpumask = cpu_possible_mask;
459 	}
460 
461 	raw_spin_lock_irqsave(&clockevents_lock, flags);
462 
463 	list_add(&dev->list, &clockevent_devices);
464 	tick_check_new_device(dev);
465 	clockevents_notify_released();
466 
467 	raw_spin_unlock_irqrestore(&clockevents_lock, flags);
468 }
469 EXPORT_SYMBOL_GPL(clockevents_register_device);
470 
471 static void clockevents_config(struct clock_event_device *dev, u32 freq)
472 {
473 	u64 sec;
474 
475 	if (!(dev->features & CLOCK_EVT_FEAT_ONESHOT))
476 		return;
477 
478 	/*
479 	 * Calculate the maximum number of seconds we can sleep. Limit
480 	 * to 10 minutes for hardware which can program more than
481 	 * 32bit ticks so we still get reasonable conversion values.
482 	 */
483 	sec = dev->max_delta_ticks;
484 	do_div(sec, freq);
485 	if (!sec)
486 		sec = 1;
487 	else if (sec > 600 && dev->max_delta_ticks > UINT_MAX)
488 		sec = 600;
489 
490 	clockevents_calc_mult_shift(dev, freq, sec);
491 	dev->min_delta_ns = cev_delta2ns(dev->min_delta_ticks, dev, false);
492 	dev->max_delta_ns = cev_delta2ns(dev->max_delta_ticks, dev, true);
493 }
494 
495 /**
496  * clockevents_config_and_register - Configure and register a clock event device
497  * @dev:	device to register
498  * @freq:	The clock frequency
499  * @min_delta:	The minimum clock ticks to program in oneshot mode
500  * @max_delta:	The maximum clock ticks to program in oneshot mode
501  *
502  * min/max_delta can be 0 for devices which do not support oneshot mode.
503  */
504 void clockevents_config_and_register(struct clock_event_device *dev,
505 				     u32 freq, unsigned long min_delta,
506 				     unsigned long max_delta)
507 {
508 	dev->min_delta_ticks = min_delta;
509 	dev->max_delta_ticks = max_delta;
510 	clockevents_config(dev, freq);
511 	clockevents_register_device(dev);
512 }
513 EXPORT_SYMBOL_GPL(clockevents_config_and_register);
514 
515 int __clockevents_update_freq(struct clock_event_device *dev, u32 freq)
516 {
517 	clockevents_config(dev, freq);
518 
519 	if (clockevent_state_oneshot(dev))
520 		return clockevents_program_event(dev, dev->next_event, false);
521 
522 	if (clockevent_state_periodic(dev))
523 		return __clockevents_switch_state(dev, CLOCK_EVT_STATE_PERIODIC);
524 
525 	return 0;
526 }
527 
528 /**
529  * clockevents_update_freq - Update frequency and reprogram a clock event device.
530  * @dev:	device to modify
531  * @freq:	new device frequency
532  *
533  * Reconfigure and reprogram a clock event device in oneshot
534  * mode. Must be called on the cpu for which the device delivers per
535  * cpu timer events. If called for the broadcast device the core takes
536  * care of serialization.
537  *
538  * Returns 0 on success, -ETIME when the event is in the past.
539  */
540 int clockevents_update_freq(struct clock_event_device *dev, u32 freq)
541 {
542 	unsigned long flags;
543 	int ret;
544 
545 	local_irq_save(flags);
546 	ret = tick_broadcast_update_freq(dev, freq);
547 	if (ret == -ENODEV)
548 		ret = __clockevents_update_freq(dev, freq);
549 	local_irq_restore(flags);
550 	return ret;
551 }
552 
553 /*
554  * Noop handler when we shut down an event device
555  */
556 void clockevents_handle_noop(struct clock_event_device *dev)
557 {
558 }
559 
560 /**
561  * clockevents_exchange_device - release and request clock devices
562  * @old:	device to release (can be NULL)
563  * @new:	device to request (can be NULL)
564  *
565  * Called from various tick functions with clockevents_lock held and
566  * interrupts disabled.
567  */
568 void clockevents_exchange_device(struct clock_event_device *old,
569 				 struct clock_event_device *new)
570 {
571 	/*
572 	 * Caller releases a clock event device. We queue it into the
573 	 * released list and do a notify add later.
574 	 */
575 	if (old) {
576 		module_put(old->owner);
577 		clockevents_switch_state(old, CLOCK_EVT_STATE_DETACHED);
578 		list_move(&old->list, &clockevents_released);
579 	}
580 
581 	if (new) {
582 		BUG_ON(!clockevent_state_detached(new));
583 		clockevents_shutdown(new);
584 	}
585 }
586 
587 /**
588  * clockevents_suspend - suspend clock devices
589  */
590 void clockevents_suspend(void)
591 {
592 	struct clock_event_device *dev;
593 
594 	list_for_each_entry_reverse(dev, &clockevent_devices, list)
595 		if (dev->suspend && !clockevent_state_detached(dev))
596 			dev->suspend(dev);
597 }
598 
599 /**
600  * clockevents_resume - resume clock devices
601  */
602 void clockevents_resume(void)
603 {
604 	struct clock_event_device *dev;
605 
606 	list_for_each_entry(dev, &clockevent_devices, list)
607 		if (dev->resume && !clockevent_state_detached(dev))
608 			dev->resume(dev);
609 }
610 
611 #ifdef CONFIG_HOTPLUG_CPU
612 
613 # ifdef CONFIG_GENERIC_CLOCKEVENTS_BROADCAST
614 /**
615  * tick_offline_cpu - Take CPU out of the broadcast mechanism
616  * @cpu:	The outgoing CPU
617  *
618  * Called on the outgoing CPU after it took itself offline.
619  */
620 void tick_offline_cpu(unsigned int cpu)
621 {
622 	raw_spin_lock(&clockevents_lock);
623 	tick_broadcast_offline(cpu);
624 	raw_spin_unlock(&clockevents_lock);
625 }
626 # endif
627 
628 /**
629  * tick_cleanup_dead_cpu - Cleanup the tick and clockevents of a dead cpu
630  * @cpu:	The dead CPU
631  */
632 void tick_cleanup_dead_cpu(int cpu)
633 {
634 	struct clock_event_device *dev, *tmp;
635 	unsigned long flags;
636 
637 	raw_spin_lock_irqsave(&clockevents_lock, flags);
638 
639 	tick_shutdown(cpu);
640 	/*
641 	 * Unregister the clock event devices which were
642 	 * released from the users in the notify chain.
643 	 */
644 	list_for_each_entry_safe(dev, tmp, &clockevents_released, list)
645 		list_del(&dev->list);
646 	/*
647 	 * Now check whether the CPU has left unused per cpu devices
648 	 */
649 	list_for_each_entry_safe(dev, tmp, &clockevent_devices, list) {
650 		if (cpumask_test_cpu(cpu, dev->cpumask) &&
651 		    cpumask_weight(dev->cpumask) == 1 &&
652 		    !tick_is_broadcast_device(dev)) {
653 			BUG_ON(!clockevent_state_detached(dev));
654 			list_del(&dev->list);
655 		}
656 	}
657 	raw_spin_unlock_irqrestore(&clockevents_lock, flags);
658 }
659 #endif
660 
661 #ifdef CONFIG_SYSFS
662 static const struct bus_type clockevents_subsys = {
663 	.name		= "clockevents",
664 	.dev_name       = "clockevent",
665 };
666 
667 static DEFINE_PER_CPU(struct device, tick_percpu_dev);
668 static struct tick_device *tick_get_tick_dev(struct device *dev);
669 
670 static ssize_t current_device_show(struct device *dev,
671 				   struct device_attribute *attr,
672 				   char *buf)
673 {
674 	struct tick_device *td;
675 	ssize_t count = 0;
676 
677 	raw_spin_lock_irq(&clockevents_lock);
678 	td = tick_get_tick_dev(dev);
679 	if (td && td->evtdev)
680 		count = sysfs_emit(buf, "%s\n", td->evtdev->name);
681 	raw_spin_unlock_irq(&clockevents_lock);
682 	return count;
683 }
684 static DEVICE_ATTR_RO(current_device);
685 
686 /* We don't support the abomination of removable broadcast devices */
687 static ssize_t unbind_device_store(struct device *dev,
688 				   struct device_attribute *attr,
689 				   const char *buf, size_t count)
690 {
691 	char name[CS_NAME_LEN];
692 	ssize_t ret = sysfs_get_uname(buf, name, count);
693 	struct clock_event_device *ce = NULL, *iter;
694 
695 	if (ret < 0)
696 		return ret;
697 
698 	ret = -ENODEV;
699 	mutex_lock(&clockevents_mutex);
700 	raw_spin_lock_irq(&clockevents_lock);
701 	list_for_each_entry(iter, &clockevent_devices, list) {
702 		if (!strcmp(iter->name, name)) {
703 			ret = __clockevents_try_unbind(iter, dev->id);
704 			ce = iter;
705 			break;
706 		}
707 	}
708 	raw_spin_unlock_irq(&clockevents_lock);
709 	/*
710 	 * We hold clockevents_mutex, so ce can't go away
711 	 */
712 	if (ret == -EAGAIN)
713 		ret = clockevents_unbind(ce, dev->id);
714 	mutex_unlock(&clockevents_mutex);
715 	return ret ? ret : count;
716 }
717 static DEVICE_ATTR_WO(unbind_device);
718 
719 #ifdef CONFIG_GENERIC_CLOCKEVENTS_BROADCAST
720 static struct device tick_bc_dev = {
721 	.init_name	= "broadcast",
722 	.id		= 0,
723 	.bus		= &clockevents_subsys,
724 };
725 
726 static struct tick_device *tick_get_tick_dev(struct device *dev)
727 {
728 	return dev == &tick_bc_dev ? tick_get_broadcast_device() :
729 		&per_cpu(tick_cpu_device, dev->id);
730 }
731 
732 static __init int tick_broadcast_init_sysfs(void)
733 {
734 	int err = device_register(&tick_bc_dev);
735 
736 	if (!err)
737 		err = device_create_file(&tick_bc_dev, &dev_attr_current_device);
738 	return err;
739 }
740 #else
741 static struct tick_device *tick_get_tick_dev(struct device *dev)
742 {
743 	return &per_cpu(tick_cpu_device, dev->id);
744 }
745 static inline int tick_broadcast_init_sysfs(void) { return 0; }
746 #endif
747 
748 static int __init tick_init_sysfs(void)
749 {
750 	int cpu;
751 
752 	for_each_possible_cpu(cpu) {
753 		struct device *dev = &per_cpu(tick_percpu_dev, cpu);
754 		int err;
755 
756 		dev->id = cpu;
757 		dev->bus = &clockevents_subsys;
758 		err = device_register(dev);
759 		if (!err)
760 			err = device_create_file(dev, &dev_attr_current_device);
761 		if (!err)
762 			err = device_create_file(dev, &dev_attr_unbind_device);
763 		if (err)
764 			return err;
765 	}
766 	return tick_broadcast_init_sysfs();
767 }
768 
769 static int __init clockevents_init_sysfs(void)
770 {
771 	int err = subsys_system_register(&clockevents_subsys, NULL);
772 
773 	if (!err)
774 		err = tick_init_sysfs();
775 	return err;
776 }
777 device_initcall(clockevents_init_sysfs);
778 #endif /* SYSFS */
779