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 */
20static LIST_HEAD(clockevent_devices);
21static LIST_HEAD(clockevents_released);
22/* Protection for the above */
23static DEFINE_RAW_SPINLOCK(clockevents_lock);
24/* Protection for unbind operations */
25static DEFINE_MUTEX(clockevents_mutex);
26
27struct ce_unbind {
28 struct clock_event_device *ce;
29 int res;
30};
31
32static 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 */
85u64 clockevent_delta2ns(unsigned long latch, struct clock_event_device *evt)
86{
87 return cev_delta2ns(latch, evt, ismax: false);
88}
89EXPORT_SYMBOL_GPL(clockevent_delta2ns);
90
91static 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 */
147void 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 */
171void clockevents_shutdown(struct clock_event_device *dev)
172{
173 clockevents_switch_state(dev, state: 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 */
181int 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 jiffy */
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 */
202static 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 */
233static 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 */
272static 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 */
303int 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 clockevent has been added which might
341 * have replaced a current regular or broadcast device. A
342 * released normal device might be a suitable replacement
343 * for the current broadcast device. Similarly a released
344 * broadcast device might be a suitable replacement for a
345 * normal device.
346 */
347static void clockevents_notify_released(void)
348{
349 struct clock_event_device *dev;
350
351 /*
352 * Keep iterating as long as tick_check_new_device()
353 * replaces a device.
354 */
355 while (!list_empty(head: &clockevents_released)) {
356 dev = list_entry(clockevents_released.next,
357 struct clock_event_device, list);
358 list_move(list: &dev->list, head: &clockevent_devices);
359 tick_check_new_device(dev);
360 }
361}
362
363/*
364 * Try to install a replacement clock event device
365 */
366static int clockevents_replace(struct clock_event_device *ced)
367{
368 struct clock_event_device *dev, *newdev = NULL;
369
370 list_for_each_entry(dev, &clockevent_devices, list) {
371 if (dev == ced || !clockevent_state_detached(dev))
372 continue;
373
374 if (!tick_check_replacement(curdev: newdev, newdev: dev))
375 continue;
376
377 if (!try_module_get(module: dev->owner))
378 continue;
379
380 if (newdev)
381 module_put(module: newdev->owner);
382 newdev = dev;
383 }
384 if (newdev) {
385 tick_install_replacement(dev: newdev);
386 list_del_init(entry: &ced->list);
387 }
388 return newdev ? 0 : -EBUSY;
389}
390
391/*
392 * Called with clockevents_mutex and clockevents_lock held
393 */
394static int __clockevents_try_unbind(struct clock_event_device *ced, int cpu)
395{
396 /* Fast track. Device is unused */
397 if (clockevent_state_detached(dev: ced)) {
398 list_del_init(entry: &ced->list);
399 return 0;
400 }
401
402 return ced == per_cpu(tick_cpu_device, cpu).evtdev ? -EAGAIN : -EBUSY;
403}
404
405/*
406 * SMP function call to unbind a device
407 */
408static void __clockevents_unbind(void *arg)
409{
410 struct ce_unbind *cu = arg;
411 int res;
412
413 raw_spin_lock(&clockevents_lock);
414 res = __clockevents_try_unbind(ced: cu->ce, smp_processor_id());
415 if (res == -EAGAIN)
416 res = clockevents_replace(ced: cu->ce);
417 cu->res = res;
418 raw_spin_unlock(&clockevents_lock);
419}
420
421/*
422 * Issues smp function call to unbind a per cpu device. Called with
423 * clockevents_mutex held.
424 */
425static int clockevents_unbind(struct clock_event_device *ced, int cpu)
426{
427 struct ce_unbind cu = { .ce = ced, .res = -ENODEV };
428
429 smp_call_function_single(cpuid: cpu, func: __clockevents_unbind, info: &cu, wait: 1);
430 return cu.res;
431}
432
433/*
434 * Unbind a clockevents device.
435 */
436int clockevents_unbind_device(struct clock_event_device *ced, int cpu)
437{
438 int ret;
439
440 mutex_lock(&clockevents_mutex);
441 ret = clockevents_unbind(ced, cpu);
442 mutex_unlock(lock: &clockevents_mutex);
443 return ret;
444}
445EXPORT_SYMBOL_GPL(clockevents_unbind_device);
446
447/**
448 * clockevents_register_device - register a clock event device
449 * @dev: device to register
450 */
451void clockevents_register_device(struct clock_event_device *dev)
452{
453 unsigned long flags;
454
455 /* Initialize state to DETACHED */
456 clockevent_set_state(dev, state: CLOCK_EVT_STATE_DETACHED);
457
458 if (!dev->cpumask) {
459 WARN_ON(num_possible_cpus() > 1);
460 dev->cpumask = cpumask_of(smp_processor_id());
461 }
462
463 if (dev->cpumask == cpu_all_mask) {
464 WARN(1, "%s cpumask == cpu_all_mask, using cpu_possible_mask instead\n",
465 dev->name);
466 dev->cpumask = cpu_possible_mask;
467 }
468
469 raw_spin_lock_irqsave(&clockevents_lock, flags);
470
471 list_add(new: &dev->list, head: &clockevent_devices);
472 tick_check_new_device(dev);
473 clockevents_notify_released();
474
475 raw_spin_unlock_irqrestore(&clockevents_lock, flags);
476}
477EXPORT_SYMBOL_GPL(clockevents_register_device);
478
479static void clockevents_config(struct clock_event_device *dev, u32 freq)
480{
481 u64 sec;
482
483 if (!(dev->features & CLOCK_EVT_FEAT_ONESHOT))
484 return;
485
486 /*
487 * Calculate the maximum number of seconds we can sleep. Limit
488 * to 10 minutes for hardware which can program more than
489 * 32bit ticks so we still get reasonable conversion values.
490 */
491 sec = dev->max_delta_ticks;
492 do_div(sec, freq);
493 if (!sec)
494 sec = 1;
495 else if (sec > 600 && dev->max_delta_ticks > UINT_MAX)
496 sec = 600;
497
498 clockevents_calc_mult_shift(ce: dev, freq, maxsec: sec);
499 dev->min_delta_ns = cev_delta2ns(latch: dev->min_delta_ticks, evt: dev, ismax: false);
500 dev->max_delta_ns = cev_delta2ns(latch: dev->max_delta_ticks, evt: dev, ismax: true);
501}
502
503/**
504 * clockevents_config_and_register - Configure and register a clock event device
505 * @dev: device to register
506 * @freq: The clock frequency
507 * @min_delta: The minimum clock ticks to program in oneshot mode
508 * @max_delta: The maximum clock ticks to program in oneshot mode
509 *
510 * min/max_delta can be 0 for devices which do not support oneshot mode.
511 */
512void clockevents_config_and_register(struct clock_event_device *dev,
513 u32 freq, unsigned long min_delta,
514 unsigned long max_delta)
515{
516 dev->min_delta_ticks = min_delta;
517 dev->max_delta_ticks = max_delta;
518 clockevents_config(dev, freq);
519 clockevents_register_device(dev);
520}
521EXPORT_SYMBOL_GPL(clockevents_config_and_register);
522
523int __clockevents_update_freq(struct clock_event_device *dev, u32 freq)
524{
525 clockevents_config(dev, freq);
526
527 if (clockevent_state_oneshot(dev))
528 return clockevents_program_event(dev, expires: dev->next_event, force: false);
529
530 if (clockevent_state_periodic(dev))
531 return __clockevents_switch_state(dev, state: CLOCK_EVT_STATE_PERIODIC);
532
533 return 0;
534}
535
536/**
537 * clockevents_update_freq - Update frequency and reprogram a clock event device.
538 * @dev: device to modify
539 * @freq: new device frequency
540 *
541 * Reconfigure and reprogram a clock event device in oneshot
542 * mode. Must be called on the cpu for which the device delivers per
543 * cpu timer events. If called for the broadcast device the core takes
544 * care of serialization.
545 *
546 * Returns 0 on success, -ETIME when the event is in the past.
547 */
548int clockevents_update_freq(struct clock_event_device *dev, u32 freq)
549{
550 unsigned long flags;
551 int ret;
552
553 local_irq_save(flags);
554 ret = tick_broadcast_update_freq(dev, freq);
555 if (ret == -ENODEV)
556 ret = __clockevents_update_freq(dev, freq);
557 local_irq_restore(flags);
558 return ret;
559}
560
561/*
562 * Noop handler when we shut down an event device
563 */
564void clockevents_handle_noop(struct clock_event_device *dev)
565{
566}
567
568/**
569 * clockevents_exchange_device - release and request clock devices
570 * @old: device to release (can be NULL)
571 * @new: device to request (can be NULL)
572 *
573 * Called from various tick functions with clockevents_lock held and
574 * interrupts disabled.
575 */
576void clockevents_exchange_device(struct clock_event_device *old,
577 struct clock_event_device *new)
578{
579 /*
580 * Caller releases a clock event device. We queue it into the
581 * released list and do a notify add later.
582 */
583 if (old) {
584 module_put(module: old->owner);
585 clockevents_switch_state(dev: old, state: CLOCK_EVT_STATE_DETACHED);
586 list_move(list: &old->list, head: &clockevents_released);
587 }
588
589 if (new) {
590 BUG_ON(!clockevent_state_detached(new));
591 clockevents_shutdown(dev: new);
592 }
593}
594
595/**
596 * clockevents_suspend - suspend clock devices
597 */
598void clockevents_suspend(void)
599{
600 struct clock_event_device *dev;
601
602 list_for_each_entry_reverse(dev, &clockevent_devices, list)
603 if (dev->suspend && !clockevent_state_detached(dev))
604 dev->suspend(dev);
605}
606
607/**
608 * clockevents_resume - resume clock devices
609 */
610void clockevents_resume(void)
611{
612 struct clock_event_device *dev;
613
614 list_for_each_entry(dev, &clockevent_devices, list)
615 if (dev->resume && !clockevent_state_detached(dev))
616 dev->resume(dev);
617}
618
619#ifdef CONFIG_HOTPLUG_CPU
620
621/**
622 * tick_offline_cpu - Shutdown all clock events related
623 * to this CPU and take it out of the
624 * broadcast mechanism.
625 * @cpu: The outgoing CPU
626 *
627 * Called by the dying CPU during teardown.
628 */
629void tick_offline_cpu(unsigned int cpu)
630{
631 struct clock_event_device *dev, *tmp;
632
633 raw_spin_lock(&clockevents_lock);
634
635 tick_broadcast_offline(cpu);
636 tick_shutdown(cpu);
637
638 /*
639 * Unregister the clock event devices which were
640 * released above.
641 */
642 list_for_each_entry_safe(dev, tmp, &clockevents_released, list)
643 list_del(entry: &dev->list);
644
645 /*
646 * Now check whether the CPU has left unused per cpu devices
647 */
648 list_for_each_entry_safe(dev, tmp, &clockevent_devices, list) {
649 if (cpumask_test_cpu(cpu, cpumask: dev->cpumask) &&
650 cpumask_weight(srcp: dev->cpumask) == 1 &&
651 !tick_is_broadcast_device(dev)) {
652 BUG_ON(!clockevent_state_detached(dev));
653 list_del(entry: &dev->list);
654 }
655 }
656
657 raw_spin_unlock(&clockevents_lock);
658}
659#endif
660
661#ifdef CONFIG_SYSFS
662static const struct bus_type clockevents_subsys = {
663 .name = "clockevents",
664 .dev_name = "clockevent",
665};
666
667static DEFINE_PER_CPU(struct device, tick_percpu_dev);
668static struct tick_device *tick_get_tick_dev(struct device *dev);
669
670static 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, fmt: "%s\n", td->evtdev->name);
681 raw_spin_unlock_irq(&clockevents_lock);
682 return count;
683}
684static DEVICE_ATTR_RO(current_device);
685
686/* We don't support the abomination of removable broadcast devices */
687static 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, dst: name, cnt: 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(ced: iter, cpu: 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(ced: ce, cpu: dev->id);
714 mutex_unlock(lock: &clockevents_mutex);
715 return ret ? ret : count;
716}
717static DEVICE_ATTR_WO(unbind_device);
718
719#ifdef CONFIG_GENERIC_CLOCKEVENTS_BROADCAST
720static struct device tick_bc_dev = {
721 .init_name = "broadcast",
722 .id = 0,
723 .bus = &clockevents_subsys,
724};
725
726static 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
732static __init int tick_broadcast_init_sysfs(void)
733{
734 int err = device_register(dev: &tick_bc_dev);
735
736 if (!err)
737 err = device_create_file(device: &tick_bc_dev, entry: &dev_attr_current_device);
738 return err;
739}
740#else
741static struct tick_device *tick_get_tick_dev(struct device *dev)
742{
743 return &per_cpu(tick_cpu_device, dev->id);
744}
745static inline int tick_broadcast_init_sysfs(void) { return 0; }
746#endif
747
748static 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(device: dev, entry: &dev_attr_current_device);
761 if (!err)
762 err = device_create_file(device: dev, entry: &dev_attr_unbind_device);
763 if (err)
764 return err;
765 }
766 return tick_broadcast_init_sysfs();
767}
768
769static int __init clockevents_init_sysfs(void)
770{
771 int err = subsys_system_register(subsys: &clockevents_subsys, NULL);
772
773 if (!err)
774 err = tick_init_sysfs();
775 return err;
776}
777device_initcall(clockevents_init_sysfs);
778#endif /* SYSFS */
779

source code of linux/kernel/time/clockevents.c