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1/*
2 * linux/kernel/time/clockevents.c
3 *
4 * This file contains functions which manage clock event devices.
5 *
6 * Copyright(C) 2005-2006, Thomas Gleixner <tglx@linutronix.de>
7 * Copyright(C) 2005-2007, Red Hat, Inc., Ingo Molnar
8 * Copyright(C) 2006-2007, Timesys Corp., Thomas Gleixner
9 *
10 * This code is licenced under the GPL version 2. For details see
11 * kernel-base/COPYING.
12 */
13
14#include <linux/clockchips.h>
15#include <linux/hrtimer.h>
16#include <linux/init.h>
17#include <linux/module.h>
18#include <linux/smp.h>
19#include <linux/device.h>
20
21#include "tick-internal.h"
22
23/* The registered clock event devices */
24static LIST_HEAD(clockevent_devices);
25static LIST_HEAD(clockevents_released);
26/* Protection for the above */
27static DEFINE_RAW_SPINLOCK(clockevents_lock);
28/* Protection for unbind operations */
29static DEFINE_MUTEX(clockevents_mutex);
30
31struct ce_unbind {
32 struct clock_event_device *ce;
33 int res;
34};
35
36static u64 cev_delta2ns(unsigned long latch, struct clock_event_device *evt,
37 bool ismax)
38{
39 u64 clc = (u64) latch << evt->shift;
40 u64 rnd;
41
42 if (unlikely(!evt->mult)) {
43 evt->mult = 1;
44 WARN_ON(1);
45 }
46 rnd = (u64) evt->mult - 1;
47
48 /*
49 * Upper bound sanity check. If the backwards conversion is
50 * not equal latch, we know that the above shift overflowed.
51 */
52 if ((clc >> evt->shift) != (u64)latch)
53 clc = ~0ULL;
54
55 /*
56 * Scaled math oddities:
57 *
58 * For mult <= (1 << shift) we can safely add mult - 1 to
59 * prevent integer rounding loss. So the backwards conversion
60 * from nsec to device ticks will be correct.
61 *
62 * For mult > (1 << shift), i.e. device frequency is > 1GHz we
63 * need to be careful. Adding mult - 1 will result in a value
64 * which when converted back to device ticks can be larger
65 * than latch by up to (mult - 1) >> shift. For the min_delta
66 * calculation we still want to apply this in order to stay
67 * above the minimum device ticks limit. For the upper limit
68 * we would end up with a latch value larger than the upper
69 * limit of the device, so we omit the add to stay below the
70 * device upper boundary.
71 *
72 * Also omit the add if it would overflow the u64 boundary.
73 */
74 if ((~0ULL - clc > rnd) &&
75 (!ismax || evt->mult <= (1ULL << evt->shift)))
76 clc += rnd;
77
78 do_div(clc, evt->mult);
79
80 /* Deltas less than 1usec are pointless noise */
81 return clc > 1000 ? clc : 1000;
82}
83
84/**
85 * clockevents_delta2ns - Convert a latch value (device ticks) to nanoseconds
86 * @latch: value to convert
87 * @evt: pointer to clock event device descriptor
88 *
89 * Math helper, returns latch value converted to nanoseconds (bound checked)
90 */
91u64 clockevent_delta2ns(unsigned long latch, struct clock_event_device *evt)
92{
93 return cev_delta2ns(latch, evt, false);
94}
95EXPORT_SYMBOL_GPL(clockevent_delta2ns);
96
97static int __clockevents_switch_state(struct clock_event_device *dev,
98 enum clock_event_state state)
99{
100 if (dev->features & CLOCK_EVT_FEAT_DUMMY)
101 return 0;
102
103 /* Transition with new state-specific callbacks */
104 switch (state) {
105 case CLOCK_EVT_STATE_DETACHED:
106 /* The clockevent device is getting replaced. Shut it down. */
107
108 case CLOCK_EVT_STATE_SHUTDOWN:
109 if (dev->set_state_shutdown)
110 return dev->set_state_shutdown(dev);
111 return 0;
112
113 case CLOCK_EVT_STATE_PERIODIC:
114 /* Core internal bug */
115 if (!(dev->features & CLOCK_EVT_FEAT_PERIODIC))
116 return -ENOSYS;
117 if (dev->set_state_periodic)
118 return dev->set_state_periodic(dev);
119 return 0;
120
121 case CLOCK_EVT_STATE_ONESHOT:
122 /* Core internal bug */
123 if (!(dev->features & CLOCK_EVT_FEAT_ONESHOT))
124 return -ENOSYS;
125 if (dev->set_state_oneshot)
126 return dev->set_state_oneshot(dev);
127 return 0;
128
129 case CLOCK_EVT_STATE_ONESHOT_STOPPED:
130 /* Core internal bug */
131 if (WARN_ONCE(!clockevent_state_oneshot(dev),
132 "Current state: %d\n",
133 clockevent_get_state(dev)))
134 return -EINVAL;
135
136 if (dev->set_state_oneshot_stopped)
137 return dev->set_state_oneshot_stopped(dev);
138 else
139 return -ENOSYS;
140
141 default:
142 return -ENOSYS;
143 }
144}
145
146/**
147 * clockevents_switch_state - set the operating state of a clock event device
148 * @dev: device to modify
149 * @state: new state
150 *
151 * Must be called with interrupts disabled !
152 */
153void clockevents_switch_state(struct clock_event_device *dev,
154 enum clock_event_state state)
155{
156 if (clockevent_get_state(dev) != state) {
157 if (__clockevents_switch_state(dev, state))
158 return;
159
160 clockevent_set_state(dev, state);
161
162 /*
163 * A nsec2cyc multiplicator of 0 is invalid and we'd crash
164 * on it, so fix it up and emit a warning:
165 */
166 if (clockevent_state_oneshot(dev)) {
167 if (unlikely(!dev->mult)) {
168 dev->mult = 1;
169 WARN_ON(1);
170 }
171 }
172 }
173}
174
175/**
176 * clockevents_shutdown - shutdown the device and clear next_event
177 * @dev: device to shutdown
178 */
179void clockevents_shutdown(struct clock_event_device *dev)
180{
181 clockevents_switch_state(dev, CLOCK_EVT_STATE_SHUTDOWN);
182 dev->next_event = KTIME_MAX;
183}
184
185/**
186 * clockevents_tick_resume - Resume the tick device before using it again
187 * @dev: device to resume
188 */
189int clockevents_tick_resume(struct clock_event_device *dev)
190{
191 int ret = 0;
192
193 if (dev->tick_resume)
194 ret = dev->tick_resume(dev);
195
196 return ret;
197}
198
199#ifdef CONFIG_GENERIC_CLOCKEVENTS_MIN_ADJUST
200
201/* Limit min_delta to a jiffie */
202#define MIN_DELTA_LIMIT (NSEC_PER_SEC / HZ)
203
204/**
205 * clockevents_increase_min_delta - raise minimum delta of a clock event device
206 * @dev: device to increase the minimum delta
207 *
208 * Returns 0 on success, -ETIME when the minimum delta reached the limit.
209 */
210static int clockevents_increase_min_delta(struct clock_event_device *dev)
211{
212 /* Nothing to do if we already reached the limit */
213 if (dev->min_delta_ns >= MIN_DELTA_LIMIT) {
214 printk_deferred(KERN_WARNING
215 "CE: Reprogramming failure. Giving up\n");
216 dev->next_event = KTIME_MAX;
217 return -ETIME;
218 }
219
220 if (dev->min_delta_ns < 5000)
221 dev->min_delta_ns = 5000;
222 else
223 dev->min_delta_ns += dev->min_delta_ns >> 1;
224
225 if (dev->min_delta_ns > MIN_DELTA_LIMIT)
226 dev->min_delta_ns = MIN_DELTA_LIMIT;
227
228 printk_deferred(KERN_WARNING
229 "CE: %s increased min_delta_ns to %llu nsec\n",
230 dev->name ? dev->name : "?",
231 (unsigned long long) dev->min_delta_ns);
232 return 0;
233}
234
235/**
236 * clockevents_program_min_delta - Set clock event device to the minimum delay.
237 * @dev: device to program
238 *
239 * Returns 0 on success, -ETIME when the retry loop failed.
240 */
241static int clockevents_program_min_delta(struct clock_event_device *dev)
242{
243 unsigned long long clc;
244 int64_t delta;
245 int i;
246
247 for (i = 0;;) {
248 delta = dev->min_delta_ns;
249 dev->next_event = ktime_add_ns(ktime_get(), delta);
250
251 if (clockevent_state_shutdown(dev))
252 return 0;
253
254 dev->retries++;
255 clc = ((unsigned long long) delta * dev->mult) >> dev->shift;
256 if (dev->set_next_event((unsigned long) clc, dev) == 0)
257 return 0;
258
259 if (++i > 2) {
260 /*
261 * We tried 3 times to program the device with the
262 * given min_delta_ns. Try to increase the minimum
263 * delta, if that fails as well get out of here.
264 */
265 if (clockevents_increase_min_delta(dev))
266 return -ETIME;
267 i = 0;
268 }
269 }
270}
271
272#else /* CONFIG_GENERIC_CLOCKEVENTS_MIN_ADJUST */
273
274/**
275 * clockevents_program_min_delta - Set clock event device to the minimum delay.
276 * @dev: device to program
277 *
278 * Returns 0 on success, -ETIME when the retry loop failed.
279 */
280static int clockevents_program_min_delta(struct clock_event_device *dev)
281{
282 unsigned long long clc;
283 int64_t delta;
284
285 delta = dev->min_delta_ns;
286 dev->next_event = ktime_add_ns(ktime_get(), delta);
287
288 if (clockevent_state_shutdown(dev))
289 return 0;
290
291 dev->retries++;
292 clc = ((unsigned long long) delta * dev->mult) >> dev->shift;
293 return dev->set_next_event((unsigned long) clc, dev);
294}
295
296#endif /* CONFIG_GENERIC_CLOCKEVENTS_MIN_ADJUST */
297
298/**
299 * clockevents_program_event - Reprogram the clock event device.
300 * @dev: device to program
301 * @expires: absolute expiry time (monotonic clock)
302 * @force: program minimum delay if expires can not be set
303 *
304 * Returns 0 on success, -ETIME when the event is in the past.
305 */
306int clockevents_program_event(struct clock_event_device *dev, ktime_t expires,
307 bool force)
308{
309 unsigned long long clc;
310 int64_t delta;
311 int rc;
312
313 if (unlikely(expires < 0)) {
314 WARN_ON_ONCE(1);
315 return -ETIME;
316 }
317
318 dev->next_event = expires;
319
320 if (clockevent_state_shutdown(dev))
321 return 0;
322
323 /* We must be in ONESHOT state here */
324 WARN_ONCE(!clockevent_state_oneshot(dev), "Current state: %d\n",
325 clockevent_get_state(dev));
326
327 /* Shortcut for clockevent devices that can deal with ktime. */
328 if (dev->features & CLOCK_EVT_FEAT_KTIME)
329 return dev->set_next_ktime(expires, dev);
330
331 delta = ktime_to_ns(ktime_sub(expires, ktime_get()));
332 if (delta <= 0)
333 return force ? clockevents_program_min_delta(dev) : -ETIME;
334
335 delta = min(delta, (int64_t) dev->max_delta_ns);
336 delta = max(delta, (int64_t) dev->min_delta_ns);
337
338 clc = ((unsigned long long) delta * dev->mult) >> dev->shift;
339 rc = dev->set_next_event((unsigned long) clc, dev);
340
341 return (rc && force) ? clockevents_program_min_delta(dev) : rc;
342}
343
344/*
345 * Called after a notify add to make devices available which were
346 * released from the notifier call.
347 */
348static void clockevents_notify_released(void)
349{
350 struct clock_event_device *dev;
351
352 while (!list_empty(&clockevents_released)) {
353 dev = list_entry(clockevents_released.next,
354 struct clock_event_device, list);
355 list_del(&dev->list);
356 list_add(&dev->list, &clockevent_devices);
357 tick_check_new_device(dev);
358 }
359}
360
361/*
362 * Try to install a replacement clock event device
363 */
364static int clockevents_replace(struct clock_event_device *ced)
365{
366 struct clock_event_device *dev, *newdev = NULL;
367
368 list_for_each_entry(dev, &clockevent_devices, list) {
369 if (dev == ced || !clockevent_state_detached(dev))
370 continue;
371
372 if (!tick_check_replacement(newdev, dev))
373 continue;
374
375 if (!try_module_get(dev->owner))
376 continue;
377
378 if (newdev)
379 module_put(newdev->owner);
380 newdev = dev;
381 }
382 if (newdev) {
383 tick_install_replacement(newdev);
384 list_del_init(&ced->list);
385 }
386 return newdev ? 0 : -EBUSY;
387}
388
389/*
390 * Called with clockevents_mutex and clockevents_lock held
391 */
392static int __clockevents_try_unbind(struct clock_event_device *ced, int cpu)
393{
394 /* Fast track. Device is unused */
395 if (clockevent_state_detached(ced)) {
396 list_del_init(&ced->list);
397 return 0;
398 }
399
400 return ced == per_cpu(tick_cpu_device, cpu).evtdev ? -EAGAIN : -EBUSY;
401}
402
403/*
404 * SMP function call to unbind a device
405 */
406static void __clockevents_unbind(void *arg)
407{
408 struct ce_unbind *cu = arg;
409 int res;
410
411 raw_spin_lock(&clockevents_lock);
412 res = __clockevents_try_unbind(cu->ce, smp_processor_id());
413 if (res == -EAGAIN)
414 res = clockevents_replace(cu->ce);
415 cu->res = res;
416 raw_spin_unlock(&clockevents_lock);
417}
418
419/*
420 * Issues smp function call to unbind a per cpu device. Called with
421 * clockevents_mutex held.
422 */
423static int clockevents_unbind(struct clock_event_device *ced, int cpu)
424{
425 struct ce_unbind cu = { .ce = ced, .res = -ENODEV };
426
427 smp_call_function_single(cpu, __clockevents_unbind, &cu, 1);
428 return cu.res;
429}
430
431/*
432 * Unbind a clockevents device.
433 */
434int clockevents_unbind_device(struct clock_event_device *ced, int cpu)
435{
436 int ret;
437
438 mutex_lock(&clockevents_mutex);
439 ret = clockevents_unbind(ced, cpu);
440 mutex_unlock(&clockevents_mutex);
441 return ret;
442}
443EXPORT_SYMBOL_GPL(clockevents_unbind_device);
444
445/**
446 * clockevents_register_device - register a clock event device
447 * @dev: device to register
448 */
449void clockevents_register_device(struct clock_event_device *dev)
450{
451 unsigned long flags;
452
453 /* Initialize state to DETACHED */
454 clockevent_set_state(dev, CLOCK_EVT_STATE_DETACHED);
455
456 if (!dev->cpumask) {
457 WARN_ON(num_possible_cpus() > 1);
458 dev->cpumask = cpumask_of(smp_processor_id());
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}
469EXPORT_SYMBOL_GPL(clockevents_register_device);
470
471void 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 */
504void 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}
513EXPORT_SYMBOL_GPL(clockevents_config_and_register);
514
515int __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 */
540int 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 */
556void 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 */
568void 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_del(&old->list);
579 list_add(&old->list, &clockevents_released);
580 }
581
582 if (new) {
583 BUG_ON(!clockevent_state_detached(new));
584 clockevents_shutdown(new);
585 }
586}
587
588/**
589 * clockevents_suspend - suspend clock devices
590 */
591void clockevents_suspend(void)
592{
593 struct clock_event_device *dev;
594
595 list_for_each_entry_reverse(dev, &clockevent_devices, list)
596 if (dev->suspend && !clockevent_state_detached(dev))
597 dev->suspend(dev);
598}
599
600/**
601 * clockevents_resume - resume clock devices
602 */
603void clockevents_resume(void)
604{
605 struct clock_event_device *dev;
606
607 list_for_each_entry(dev, &clockevent_devices, list)
608 if (dev->resume && !clockevent_state_detached(dev))
609 dev->resume(dev);
610}
611
612#ifdef CONFIG_HOTPLUG_CPU
613/**
614 * tick_cleanup_dead_cpu - Cleanup the tick and clockevents of a dead cpu
615 */
616void tick_cleanup_dead_cpu(int cpu)
617{
618 struct clock_event_device *dev, *tmp;
619 unsigned long flags;
620
621 raw_spin_lock_irqsave(&clockevents_lock, flags);
622
623 tick_shutdown_broadcast_oneshot(cpu);
624 tick_shutdown_broadcast(cpu);
625 tick_shutdown(cpu);
626 /*
627 * Unregister the clock event devices which were
628 * released from the users in the notify chain.
629 */
630 list_for_each_entry_safe(dev, tmp, &clockevents_released, list)
631 list_del(&dev->list);
632 /*
633 * Now check whether the CPU has left unused per cpu devices
634 */
635 list_for_each_entry_safe(dev, tmp, &clockevent_devices, list) {
636 if (cpumask_test_cpu(cpu, dev->cpumask) &&
637 cpumask_weight(dev->cpumask) == 1 &&
638 !tick_is_broadcast_device(dev)) {
639 BUG_ON(!clockevent_state_detached(dev));
640 list_del(&dev->list);
641 }
642 }
643 raw_spin_unlock_irqrestore(&clockevents_lock, flags);
644}
645#endif
646
647#ifdef CONFIG_SYSFS
648static struct bus_type clockevents_subsys = {
649 .name = "clockevents",
650 .dev_name = "clockevent",
651};
652
653static DEFINE_PER_CPU(struct device, tick_percpu_dev);
654static struct tick_device *tick_get_tick_dev(struct device *dev);
655
656static ssize_t sysfs_show_current_tick_dev(struct device *dev,
657 struct device_attribute *attr,
658 char *buf)
659{
660 struct tick_device *td;
661 ssize_t count = 0;
662
663 raw_spin_lock_irq(&clockevents_lock);
664 td = tick_get_tick_dev(dev);
665 if (td && td->evtdev)
666 count = snprintf(buf, PAGE_SIZE, "%s\n", td->evtdev->name);
667 raw_spin_unlock_irq(&clockevents_lock);
668 return count;
669}
670static DEVICE_ATTR(current_device, 0444, sysfs_show_current_tick_dev, NULL);
671
672/* We don't support the abomination of removable broadcast devices */
673static ssize_t sysfs_unbind_tick_dev(struct device *dev,
674 struct device_attribute *attr,
675 const char *buf, size_t count)
676{
677 char name[CS_NAME_LEN];
678 ssize_t ret = sysfs_get_uname(buf, name, count);
679 struct clock_event_device *ce;
680
681 if (ret < 0)
682 return ret;
683
684 ret = -ENODEV;
685 mutex_lock(&clockevents_mutex);
686 raw_spin_lock_irq(&clockevents_lock);
687 list_for_each_entry(ce, &clockevent_devices, list) {
688 if (!strcmp(ce->name, name)) {
689 ret = __clockevents_try_unbind(ce, dev->id);
690 break;
691 }
692 }
693 raw_spin_unlock_irq(&clockevents_lock);
694 /*
695 * We hold clockevents_mutex, so ce can't go away
696 */
697 if (ret == -EAGAIN)
698 ret = clockevents_unbind(ce, dev->id);
699 mutex_unlock(&clockevents_mutex);
700 return ret ? ret : count;
701}
702static DEVICE_ATTR(unbind_device, 0200, NULL, sysfs_unbind_tick_dev);
703
704#ifdef CONFIG_GENERIC_CLOCKEVENTS_BROADCAST
705static struct device tick_bc_dev = {
706 .init_name = "broadcast",
707 .id = 0,
708 .bus = &clockevents_subsys,
709};
710
711static struct tick_device *tick_get_tick_dev(struct device *dev)
712{
713 return dev == &tick_bc_dev ? tick_get_broadcast_device() :
714 &per_cpu(tick_cpu_device, dev->id);
715}
716
717static __init int tick_broadcast_init_sysfs(void)
718{
719 int err = device_register(&tick_bc_dev);
720
721 if (!err)
722 err = device_create_file(&tick_bc_dev, &dev_attr_current_device);
723 return err;
724}
725#else
726static struct tick_device *tick_get_tick_dev(struct device *dev)
727{
728 return &per_cpu(tick_cpu_device, dev->id);
729}
730static inline int tick_broadcast_init_sysfs(void) { return 0; }
731#endif
732
733static int __init tick_init_sysfs(void)
734{
735 int cpu;
736
737 for_each_possible_cpu(cpu) {
738 struct device *dev = &per_cpu(tick_percpu_dev, cpu);
739 int err;
740
741 dev->id = cpu;
742 dev->bus = &clockevents_subsys;
743 err = device_register(dev);
744 if (!err)
745 err = device_create_file(dev, &dev_attr_current_device);
746 if (!err)
747 err = device_create_file(dev, &dev_attr_unbind_device);
748 if (err)
749 return err;
750 }
751 return tick_broadcast_init_sysfs();
752}
753
754static int __init clockevents_init_sysfs(void)
755{
756 int err = subsys_system_register(&clockevents_subsys, NULL);
757
758 if (!err)
759 err = tick_init_sysfs();
760 return err;
761}
762device_initcall(clockevents_init_sysfs);
763#endif /* SYSFS */
1/*
2 * linux/kernel/time/clockevents.c
3 *
4 * This file contains functions which manage clock event devices.
5 *
6 * Copyright(C) 2005-2006, Thomas Gleixner <tglx@linutronix.de>
7 * Copyright(C) 2005-2007, Red Hat, Inc., Ingo Molnar
8 * Copyright(C) 2006-2007, Timesys Corp., Thomas Gleixner
9 *
10 * This code is licenced under the GPL version 2. For details see
11 * kernel-base/COPYING.
12 */
13
14#include <linux/clockchips.h>
15#include <linux/hrtimer.h>
16#include <linux/init.h>
17#include <linux/module.h>
18#include <linux/smp.h>
19#include <linux/device.h>
20
21#include "tick-internal.h"
22
23/* The registered clock event devices */
24static LIST_HEAD(clockevent_devices);
25static LIST_HEAD(clockevents_released);
26/* Protection for the above */
27static DEFINE_RAW_SPINLOCK(clockevents_lock);
28/* Protection for unbind operations */
29static DEFINE_MUTEX(clockevents_mutex);
30
31struct ce_unbind {
32 struct clock_event_device *ce;
33 int res;
34};
35
36static u64 cev_delta2ns(unsigned long latch, struct clock_event_device *evt,
37 bool ismax)
38{
39 u64 clc = (u64) latch << evt->shift;
40 u64 rnd;
41
42 if (unlikely(!evt->mult)) {
43 evt->mult = 1;
44 WARN_ON(1);
45 }
46 rnd = (u64) evt->mult - 1;
47
48 /*
49 * Upper bound sanity check. If the backwards conversion is
50 * not equal latch, we know that the above shift overflowed.
51 */
52 if ((clc >> evt->shift) != (u64)latch)
53 clc = ~0ULL;
54
55 /*
56 * Scaled math oddities:
57 *
58 * For mult <= (1 << shift) we can safely add mult - 1 to
59 * prevent integer rounding loss. So the backwards conversion
60 * from nsec to device ticks will be correct.
61 *
62 * For mult > (1 << shift), i.e. device frequency is > 1GHz we
63 * need to be careful. Adding mult - 1 will result in a value
64 * which when converted back to device ticks can be larger
65 * than latch by up to (mult - 1) >> shift. For the min_delta
66 * calculation we still want to apply this in order to stay
67 * above the minimum device ticks limit. For the upper limit
68 * we would end up with a latch value larger than the upper
69 * limit of the device, so we omit the add to stay below the
70 * device upper boundary.
71 *
72 * Also omit the add if it would overflow the u64 boundary.
73 */
74 if ((~0ULL - clc > rnd) &&
75 (!ismax || evt->mult <= (1U << evt->shift)))
76 clc += rnd;
77
78 do_div(clc, evt->mult);
79
80 /* Deltas less than 1usec are pointless noise */
81 return clc > 1000 ? clc : 1000;
82}
83
84/**
85 * clockevents_delta2ns - Convert a latch value (device ticks) to nanoseconds
86 * @latch: value to convert
87 * @evt: pointer to clock event device descriptor
88 *
89 * Math helper, returns latch value converted to nanoseconds (bound checked)
90 */
91u64 clockevent_delta2ns(unsigned long latch, struct clock_event_device *evt)
92{
93 return cev_delta2ns(latch, evt, false);
94}
95EXPORT_SYMBOL_GPL(clockevent_delta2ns);
96
97/**
98 * clockevents_set_mode - set the operating mode of a clock event device
99 * @dev: device to modify
100 * @mode: new mode
101 *
102 * Must be called with interrupts disabled !
103 */
104void clockevents_set_mode(struct clock_event_device *dev,
105 enum clock_event_mode mode)
106{
107 if (dev->mode != mode) {
108 dev->set_mode(mode, dev);
109 dev->mode = mode;
110
111 /*
112 * A nsec2cyc multiplicator of 0 is invalid and we'd crash
113 * on it, so fix it up and emit a warning:
114 */
115 if (mode == CLOCK_EVT_MODE_ONESHOT) {
116 if (unlikely(!dev->mult)) {
117 dev->mult = 1;
118 WARN_ON(1);
119 }
120 }
121 }
122}
123
124/**
125 * clockevents_shutdown - shutdown the device and clear next_event
126 * @dev: device to shutdown
127 */
128void clockevents_shutdown(struct clock_event_device *dev)
129{
130 clockevents_set_mode(dev, CLOCK_EVT_MODE_SHUTDOWN);
131 dev->next_event.tv64 = KTIME_MAX;
132}
133
134#ifdef CONFIG_GENERIC_CLOCKEVENTS_MIN_ADJUST
135
136/* Limit min_delta to a jiffie */
137#define MIN_DELTA_LIMIT (NSEC_PER_SEC / HZ)
138
139/**
140 * clockevents_increase_min_delta - raise minimum delta of a clock event device
141 * @dev: device to increase the minimum delta
142 *
143 * Returns 0 on success, -ETIME when the minimum delta reached the limit.
144 */
145static int clockevents_increase_min_delta(struct clock_event_device *dev)
146{
147 /* Nothing to do if we already reached the limit */
148 if (dev->min_delta_ns >= MIN_DELTA_LIMIT) {
149 printk(KERN_WARNING "CE: Reprogramming failure. Giving up\n");
150 dev->next_event.tv64 = KTIME_MAX;
151 return -ETIME;
152 }
153
154 if (dev->min_delta_ns < 5000)
155 dev->min_delta_ns = 5000;
156 else
157 dev->min_delta_ns += dev->min_delta_ns >> 1;
158
159 if (dev->min_delta_ns > MIN_DELTA_LIMIT)
160 dev->min_delta_ns = MIN_DELTA_LIMIT;
161
162 printk(KERN_WARNING "CE: %s increased min_delta_ns to %llu nsec\n",
163 dev->name ? dev->name : "?",
164 (unsigned long long) dev->min_delta_ns);
165 return 0;
166}
167
168/**
169 * clockevents_program_min_delta - Set clock event device to the minimum delay.
170 * @dev: device to program
171 *
172 * Returns 0 on success, -ETIME when the retry loop failed.
173 */
174static int clockevents_program_min_delta(struct clock_event_device *dev)
175{
176 unsigned long long clc;
177 int64_t delta;
178 int i;
179
180 for (i = 0;;) {
181 delta = dev->min_delta_ns;
182 dev->next_event = ktime_add_ns(ktime_get(), delta);
183
184 if (dev->mode == CLOCK_EVT_MODE_SHUTDOWN)
185 return 0;
186
187 dev->retries++;
188 clc = ((unsigned long long) delta * dev->mult) >> dev->shift;
189 if (dev->set_next_event((unsigned long) clc, dev) == 0)
190 return 0;
191
192 if (++i > 2) {
193 /*
194 * We tried 3 times to program the device with the
195 * given min_delta_ns. Try to increase the minimum
196 * delta, if that fails as well get out of here.
197 */
198 if (clockevents_increase_min_delta(dev))
199 return -ETIME;
200 i = 0;
201 }
202 }
203}
204
205#else /* CONFIG_GENERIC_CLOCKEVENTS_MIN_ADJUST */
206
207/**
208 * clockevents_program_min_delta - Set clock event device to the minimum delay.
209 * @dev: device to program
210 *
211 * Returns 0 on success, -ETIME when the retry loop failed.
212 */
213static int clockevents_program_min_delta(struct clock_event_device *dev)
214{
215 unsigned long long clc;
216 int64_t delta;
217
218 delta = dev->min_delta_ns;
219 dev->next_event = ktime_add_ns(ktime_get(), delta);
220
221 if (dev->mode == CLOCK_EVT_MODE_SHUTDOWN)
222 return 0;
223
224 dev->retries++;
225 clc = ((unsigned long long) delta * dev->mult) >> dev->shift;
226 return dev->set_next_event((unsigned long) clc, dev);
227}
228
229#endif /* CONFIG_GENERIC_CLOCKEVENTS_MIN_ADJUST */
230
231/**
232 * clockevents_program_event - Reprogram the clock event device.
233 * @dev: device to program
234 * @expires: absolute expiry time (monotonic clock)
235 * @force: program minimum delay if expires can not be set
236 *
237 * Returns 0 on success, -ETIME when the event is in the past.
238 */
239int clockevents_program_event(struct clock_event_device *dev, ktime_t expires,
240 bool force)
241{
242 unsigned long long clc;
243 int64_t delta;
244 int rc;
245
246 if (unlikely(expires.tv64 < 0)) {
247 WARN_ON_ONCE(1);
248 return -ETIME;
249 }
250
251 dev->next_event = expires;
252
253 if (dev->mode == CLOCK_EVT_MODE_SHUTDOWN)
254 return 0;
255
256 /* Shortcut for clockevent devices that can deal with ktime. */
257 if (dev->features & CLOCK_EVT_FEAT_KTIME)
258 return dev->set_next_ktime(expires, dev);
259
260 delta = ktime_to_ns(ktime_sub(expires, ktime_get()));
261 if (delta <= 0)
262 return force ? clockevents_program_min_delta(dev) : -ETIME;
263
264 delta = min(delta, (int64_t) dev->max_delta_ns);
265 delta = max(delta, (int64_t) dev->min_delta_ns);
266
267 clc = ((unsigned long long) delta * dev->mult) >> dev->shift;
268 rc = dev->set_next_event((unsigned long) clc, dev);
269
270 return (rc && force) ? clockevents_program_min_delta(dev) : rc;
271}
272
273/*
274 * Called after a notify add to make devices available which were
275 * released from the notifier call.
276 */
277static void clockevents_notify_released(void)
278{
279 struct clock_event_device *dev;
280
281 while (!list_empty(&clockevents_released)) {
282 dev = list_entry(clockevents_released.next,
283 struct clock_event_device, list);
284 list_del(&dev->list);
285 list_add(&dev->list, &clockevent_devices);
286 tick_check_new_device(dev);
287 }
288}
289
290/*
291 * Try to install a replacement clock event device
292 */
293static int clockevents_replace(struct clock_event_device *ced)
294{
295 struct clock_event_device *dev, *newdev = NULL;
296
297 list_for_each_entry(dev, &clockevent_devices, list) {
298 if (dev == ced || dev->mode != CLOCK_EVT_MODE_UNUSED)
299 continue;
300
301 if (!tick_check_replacement(newdev, dev))
302 continue;
303
304 if (!try_module_get(dev->owner))
305 continue;
306
307 if (newdev)
308 module_put(newdev->owner);
309 newdev = dev;
310 }
311 if (newdev) {
312 tick_install_replacement(newdev);
313 list_del_init(&ced->list);
314 }
315 return newdev ? 0 : -EBUSY;
316}
317
318/*
319 * Called with clockevents_mutex and clockevents_lock held
320 */
321static int __clockevents_try_unbind(struct clock_event_device *ced, int cpu)
322{
323 /* Fast track. Device is unused */
324 if (ced->mode == CLOCK_EVT_MODE_UNUSED) {
325 list_del_init(&ced->list);
326 return 0;
327 }
328
329 return ced == per_cpu(tick_cpu_device, cpu).evtdev ? -EAGAIN : -EBUSY;
330}
331
332/*
333 * SMP function call to unbind a device
334 */
335static void __clockevents_unbind(void *arg)
336{
337 struct ce_unbind *cu = arg;
338 int res;
339
340 raw_spin_lock(&clockevents_lock);
341 res = __clockevents_try_unbind(cu->ce, smp_processor_id());
342 if (res == -EAGAIN)
343 res = clockevents_replace(cu->ce);
344 cu->res = res;
345 raw_spin_unlock(&clockevents_lock);
346}
347
348/*
349 * Issues smp function call to unbind a per cpu device. Called with
350 * clockevents_mutex held.
351 */
352static int clockevents_unbind(struct clock_event_device *ced, int cpu)
353{
354 struct ce_unbind cu = { .ce = ced, .res = -ENODEV };
355
356 smp_call_function_single(cpu, __clockevents_unbind, &cu, 1);
357 return cu.res;
358}
359
360/*
361 * Unbind a clockevents device.
362 */
363int clockevents_unbind_device(struct clock_event_device *ced, int cpu)
364{
365 int ret;
366
367 mutex_lock(&clockevents_mutex);
368 ret = clockevents_unbind(ced, cpu);
369 mutex_unlock(&clockevents_mutex);
370 return ret;
371}
372EXPORT_SYMBOL_GPL(clockevents_unbind);
373
374/**
375 * clockevents_register_device - register a clock event device
376 * @dev: device to register
377 */
378void clockevents_register_device(struct clock_event_device *dev)
379{
380 unsigned long flags;
381
382 BUG_ON(dev->mode != CLOCK_EVT_MODE_UNUSED);
383 if (!dev->cpumask) {
384 WARN_ON(num_possible_cpus() > 1);
385 dev->cpumask = cpumask_of(smp_processor_id());
386 }
387
388 raw_spin_lock_irqsave(&clockevents_lock, flags);
389
390 list_add(&dev->list, &clockevent_devices);
391 tick_check_new_device(dev);
392 clockevents_notify_released();
393
394 raw_spin_unlock_irqrestore(&clockevents_lock, flags);
395}
396EXPORT_SYMBOL_GPL(clockevents_register_device);
397
398void clockevents_config(struct clock_event_device *dev, u32 freq)
399{
400 u64 sec;
401
402 if (!(dev->features & CLOCK_EVT_FEAT_ONESHOT))
403 return;
404
405 /*
406 * Calculate the maximum number of seconds we can sleep. Limit
407 * to 10 minutes for hardware which can program more than
408 * 32bit ticks so we still get reasonable conversion values.
409 */
410 sec = dev->max_delta_ticks;
411 do_div(sec, freq);
412 if (!sec)
413 sec = 1;
414 else if (sec > 600 && dev->max_delta_ticks > UINT_MAX)
415 sec = 600;
416
417 clockevents_calc_mult_shift(dev, freq, sec);
418 dev->min_delta_ns = cev_delta2ns(dev->min_delta_ticks, dev, false);
419 dev->max_delta_ns = cev_delta2ns(dev->max_delta_ticks, dev, true);
420}
421
422/**
423 * clockevents_config_and_register - Configure and register a clock event device
424 * @dev: device to register
425 * @freq: The clock frequency
426 * @min_delta: The minimum clock ticks to program in oneshot mode
427 * @max_delta: The maximum clock ticks to program in oneshot mode
428 *
429 * min/max_delta can be 0 for devices which do not support oneshot mode.
430 */
431void clockevents_config_and_register(struct clock_event_device *dev,
432 u32 freq, unsigned long min_delta,
433 unsigned long max_delta)
434{
435 dev->min_delta_ticks = min_delta;
436 dev->max_delta_ticks = max_delta;
437 clockevents_config(dev, freq);
438 clockevents_register_device(dev);
439}
440EXPORT_SYMBOL_GPL(clockevents_config_and_register);
441
442int __clockevents_update_freq(struct clock_event_device *dev, u32 freq)
443{
444 clockevents_config(dev, freq);
445
446 if (dev->mode == CLOCK_EVT_MODE_ONESHOT)
447 return clockevents_program_event(dev, dev->next_event, false);
448
449 if (dev->mode == CLOCK_EVT_MODE_PERIODIC)
450 dev->set_mode(CLOCK_EVT_MODE_PERIODIC, dev);
451
452 return 0;
453}
454
455/**
456 * clockevents_update_freq - Update frequency and reprogram a clock event device.
457 * @dev: device to modify
458 * @freq: new device frequency
459 *
460 * Reconfigure and reprogram a clock event device in oneshot
461 * mode. Must be called on the cpu for which the device delivers per
462 * cpu timer events. If called for the broadcast device the core takes
463 * care of serialization.
464 *
465 * Returns 0 on success, -ETIME when the event is in the past.
466 */
467int clockevents_update_freq(struct clock_event_device *dev, u32 freq)
468{
469 unsigned long flags;
470 int ret;
471
472 local_irq_save(flags);
473 ret = tick_broadcast_update_freq(dev, freq);
474 if (ret == -ENODEV)
475 ret = __clockevents_update_freq(dev, freq);
476 local_irq_restore(flags);
477 return ret;
478}
479
480/*
481 * Noop handler when we shut down an event device
482 */
483void clockevents_handle_noop(struct clock_event_device *dev)
484{
485}
486
487/**
488 * clockevents_exchange_device - release and request clock devices
489 * @old: device to release (can be NULL)
490 * @new: device to request (can be NULL)
491 *
492 * Called from the notifier chain. clockevents_lock is held already
493 */
494void clockevents_exchange_device(struct clock_event_device *old,
495 struct clock_event_device *new)
496{
497 unsigned long flags;
498
499 local_irq_save(flags);
500 /*
501 * Caller releases a clock event device. We queue it into the
502 * released list and do a notify add later.
503 */
504 if (old) {
505 module_put(old->owner);
506 clockevents_set_mode(old, CLOCK_EVT_MODE_UNUSED);
507 list_del(&old->list);
508 list_add(&old->list, &clockevents_released);
509 }
510
511 if (new) {
512 BUG_ON(new->mode != CLOCK_EVT_MODE_UNUSED);
513 clockevents_shutdown(new);
514 }
515 local_irq_restore(flags);
516}
517
518/**
519 * clockevents_suspend - suspend clock devices
520 */
521void clockevents_suspend(void)
522{
523 struct clock_event_device *dev;
524
525 list_for_each_entry_reverse(dev, &clockevent_devices, list)
526 if (dev->suspend)
527 dev->suspend(dev);
528}
529
530/**
531 * clockevents_resume - resume clock devices
532 */
533void clockevents_resume(void)
534{
535 struct clock_event_device *dev;
536
537 list_for_each_entry(dev, &clockevent_devices, list)
538 if (dev->resume)
539 dev->resume(dev);
540}
541
542#ifdef CONFIG_GENERIC_CLOCKEVENTS
543/**
544 * clockevents_notify - notification about relevant events
545 * Returns 0 on success, any other value on error
546 */
547int clockevents_notify(unsigned long reason, void *arg)
548{
549 struct clock_event_device *dev, *tmp;
550 unsigned long flags;
551 int cpu, ret = 0;
552
553 raw_spin_lock_irqsave(&clockevents_lock, flags);
554
555 switch (reason) {
556 case CLOCK_EVT_NOTIFY_BROADCAST_ON:
557 case CLOCK_EVT_NOTIFY_BROADCAST_OFF:
558 case CLOCK_EVT_NOTIFY_BROADCAST_FORCE:
559 tick_broadcast_on_off(reason, arg);
560 break;
561
562 case CLOCK_EVT_NOTIFY_BROADCAST_ENTER:
563 case CLOCK_EVT_NOTIFY_BROADCAST_EXIT:
564 ret = tick_broadcast_oneshot_control(reason);
565 break;
566
567 case CLOCK_EVT_NOTIFY_CPU_DYING:
568 tick_handover_do_timer(arg);
569 break;
570
571 case CLOCK_EVT_NOTIFY_SUSPEND:
572 tick_suspend();
573 tick_suspend_broadcast();
574 break;
575
576 case CLOCK_EVT_NOTIFY_RESUME:
577 tick_resume();
578 break;
579
580 case CLOCK_EVT_NOTIFY_CPU_DEAD:
581 tick_shutdown_broadcast_oneshot(arg);
582 tick_shutdown_broadcast(arg);
583 tick_shutdown(arg);
584 /*
585 * Unregister the clock event devices which were
586 * released from the users in the notify chain.
587 */
588 list_for_each_entry_safe(dev, tmp, &clockevents_released, list)
589 list_del(&dev->list);
590 /*
591 * Now check whether the CPU has left unused per cpu devices
592 */
593 cpu = *((int *)arg);
594 list_for_each_entry_safe(dev, tmp, &clockevent_devices, list) {
595 if (cpumask_test_cpu(cpu, dev->cpumask) &&
596 cpumask_weight(dev->cpumask) == 1 &&
597 !tick_is_broadcast_device(dev)) {
598 BUG_ON(dev->mode != CLOCK_EVT_MODE_UNUSED);
599 list_del(&dev->list);
600 }
601 }
602 break;
603 default:
604 break;
605 }
606 raw_spin_unlock_irqrestore(&clockevents_lock, flags);
607 return ret;
608}
609EXPORT_SYMBOL_GPL(clockevents_notify);
610
611#ifdef CONFIG_SYSFS
612struct bus_type clockevents_subsys = {
613 .name = "clockevents",
614 .dev_name = "clockevent",
615};
616
617static DEFINE_PER_CPU(struct device, tick_percpu_dev);
618static struct tick_device *tick_get_tick_dev(struct device *dev);
619
620static ssize_t sysfs_show_current_tick_dev(struct device *dev,
621 struct device_attribute *attr,
622 char *buf)
623{
624 struct tick_device *td;
625 ssize_t count = 0;
626
627 raw_spin_lock_irq(&clockevents_lock);
628 td = tick_get_tick_dev(dev);
629 if (td && td->evtdev)
630 count = snprintf(buf, PAGE_SIZE, "%s\n", td->evtdev->name);
631 raw_spin_unlock_irq(&clockevents_lock);
632 return count;
633}
634static DEVICE_ATTR(current_device, 0444, sysfs_show_current_tick_dev, NULL);
635
636/* We don't support the abomination of removable broadcast devices */
637static ssize_t sysfs_unbind_tick_dev(struct device *dev,
638 struct device_attribute *attr,
639 const char *buf, size_t count)
640{
641 char name[CS_NAME_LEN];
642 ssize_t ret = sysfs_get_uname(buf, name, count);
643 struct clock_event_device *ce;
644
645 if (ret < 0)
646 return ret;
647
648 ret = -ENODEV;
649 mutex_lock(&clockevents_mutex);
650 raw_spin_lock_irq(&clockevents_lock);
651 list_for_each_entry(ce, &clockevent_devices, list) {
652 if (!strcmp(ce->name, name)) {
653 ret = __clockevents_try_unbind(ce, dev->id);
654 break;
655 }
656 }
657 raw_spin_unlock_irq(&clockevents_lock);
658 /*
659 * We hold clockevents_mutex, so ce can't go away
660 */
661 if (ret == -EAGAIN)
662 ret = clockevents_unbind(ce, dev->id);
663 mutex_unlock(&clockevents_mutex);
664 return ret ? ret : count;
665}
666static DEVICE_ATTR(unbind_device, 0200, NULL, sysfs_unbind_tick_dev);
667
668#ifdef CONFIG_GENERIC_CLOCKEVENTS_BROADCAST
669static struct device tick_bc_dev = {
670 .init_name = "broadcast",
671 .id = 0,
672 .bus = &clockevents_subsys,
673};
674
675static struct tick_device *tick_get_tick_dev(struct device *dev)
676{
677 return dev == &tick_bc_dev ? tick_get_broadcast_device() :
678 &per_cpu(tick_cpu_device, dev->id);
679}
680
681static __init int tick_broadcast_init_sysfs(void)
682{
683 int err = device_register(&tick_bc_dev);
684
685 if (!err)
686 err = device_create_file(&tick_bc_dev, &dev_attr_current_device);
687 return err;
688}
689#else
690static struct tick_device *tick_get_tick_dev(struct device *dev)
691{
692 return &per_cpu(tick_cpu_device, dev->id);
693}
694static inline int tick_broadcast_init_sysfs(void) { return 0; }
695#endif
696
697static int __init tick_init_sysfs(void)
698{
699 int cpu;
700
701 for_each_possible_cpu(cpu) {
702 struct device *dev = &per_cpu(tick_percpu_dev, cpu);
703 int err;
704
705 dev->id = cpu;
706 dev->bus = &clockevents_subsys;
707 err = device_register(dev);
708 if (!err)
709 err = device_create_file(dev, &dev_attr_current_device);
710 if (!err)
711 err = device_create_file(dev, &dev_attr_unbind_device);
712 if (err)
713 return err;
714 }
715 return tick_broadcast_init_sysfs();
716}
717
718static int __init clockevents_init_sysfs(void)
719{
720 int err = subsys_system_register(&clockevents_subsys, NULL);
721
722 if (!err)
723 err = tick_init_sysfs();
724 return err;
725}
726device_initcall(clockevents_init_sysfs);
727#endif /* SYSFS */
728
729#endif /* GENERIC_CLOCK_EVENTS */