2 * linux/kernel/time/clockevents.c
4 * This file contains functions which manage clock event devices.
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
10 * This code is licenced under the GPL version 2. For details see
11 * kernel-base/COPYING.
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>
21 #include "tick-internal.h"
23 /* The registered clock event devices */
24 static LIST_HEAD(clockevent_devices);
25 static LIST_HEAD(clockevents_released);
26 /* Protection for the above */
27 static DEFINE_RAW_SPINLOCK(clockevents_lock);
28 /* Protection for unbind operations */
29 static DEFINE_MUTEX(clockevents_mutex);
32 struct clock_event_device *ce;
36 static u64 cev_delta2ns(unsigned long latch, struct clock_event_device *evt,
39 u64 clc = (u64) latch << evt->shift;
42 if (unlikely(!evt->mult)) {
46 rnd = (u64) evt->mult - 1;
49 * Upper bound sanity check. If the backwards conversion is
50 * not equal latch, we know that the above shift overflowed.
52 if ((clc >> evt->shift) != (u64)latch)
56 * Scaled math oddities:
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.
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.
72 * Also omit the add if it would overflow the u64 boundary.
74 if ((~0ULL - clc > rnd) &&
75 (!ismax || evt->mult <= (1ULL << evt->shift)))
78 do_div(clc, evt->mult);
80 /* Deltas less than 1usec are pointless noise */
81 return clc > 1000 ? clc : 1000;
85 * clockevents_delta2ns - Convert a latch value (device ticks) to nanoseconds
86 * @latch: value to convert
87 * @evt: pointer to clock event device descriptor
89 * Math helper, returns latch value converted to nanoseconds (bound checked)
91 u64 clockevent_delta2ns(unsigned long latch, struct clock_event_device *evt)
93 return cev_delta2ns(latch, evt, false);
95 EXPORT_SYMBOL_GPL(clockevent_delta2ns);
97 static int __clockevents_set_state(struct clock_event_device *dev,
98 enum clock_event_state state)
100 /* Transition with legacy set_mode() callback */
102 /* Legacy callback doesn't support new modes */
103 if (state > CLOCK_EVT_STATE_ONESHOT)
106 * 'clock_event_state' and 'clock_event_mode' have 1-to-1
107 * mapping until *_ONESHOT, and so a simple cast will work.
109 dev->set_mode((enum clock_event_mode)state, dev);
110 dev->mode = (enum clock_event_mode)state;
114 if (dev->features & CLOCK_EVT_FEAT_DUMMY)
117 /* Transition with new state-specific callbacks */
119 case CLOCK_EVT_STATE_DETACHED:
121 * This is an internal state, which is guaranteed to go from
122 * SHUTDOWN to DETACHED. No driver interaction required.
126 case CLOCK_EVT_STATE_SHUTDOWN:
127 return dev->set_state_shutdown(dev);
129 case CLOCK_EVT_STATE_PERIODIC:
130 /* Core internal bug */
131 if (!(dev->features & CLOCK_EVT_FEAT_PERIODIC))
133 return dev->set_state_periodic(dev);
135 case CLOCK_EVT_STATE_ONESHOT:
136 /* Core internal bug */
137 if (!(dev->features & CLOCK_EVT_FEAT_ONESHOT))
139 return dev->set_state_oneshot(dev);
147 * clockevents_set_state - set the operating state of a clock event device
148 * @dev: device to modify
151 * Must be called with interrupts disabled !
153 void clockevents_set_state(struct clock_event_device *dev,
154 enum clock_event_state state)
156 if (dev->state != state) {
157 if (__clockevents_set_state(dev, state))
163 * A nsec2cyc multiplicator of 0 is invalid and we'd crash
164 * on it, so fix it up and emit a warning:
166 if (state == CLOCK_EVT_STATE_ONESHOT) {
167 if (unlikely(!dev->mult)) {
176 * clockevents_shutdown - shutdown the device and clear next_event
177 * @dev: device to shutdown
179 void clockevents_shutdown(struct clock_event_device *dev)
181 clockevents_set_state(dev, CLOCK_EVT_STATE_SHUTDOWN);
182 dev->next_event.tv64 = KTIME_MAX;
186 * clockevents_tick_resume - Resume the tick device before using it again
187 * @dev: device to resume
189 int clockevents_tick_resume(struct clock_event_device *dev)
194 dev->set_mode(CLOCK_EVT_MODE_RESUME, dev);
195 dev->mode = CLOCK_EVT_MODE_RESUME;
196 } else if (dev->tick_resume) {
197 ret = dev->tick_resume(dev);
203 #ifdef CONFIG_GENERIC_CLOCKEVENTS_MIN_ADJUST
205 /* Limit min_delta to a jiffie */
206 #define MIN_DELTA_LIMIT (NSEC_PER_SEC / HZ)
209 * clockevents_increase_min_delta - raise minimum delta of a clock event device
210 * @dev: device to increase the minimum delta
212 * Returns 0 on success, -ETIME when the minimum delta reached the limit.
214 static int clockevents_increase_min_delta(struct clock_event_device *dev)
216 /* Nothing to do if we already reached the limit */
217 if (dev->min_delta_ns >= MIN_DELTA_LIMIT) {
218 printk_deferred(KERN_WARNING
219 "CE: Reprogramming failure. Giving up\n");
220 dev->next_event.tv64 = KTIME_MAX;
224 if (dev->min_delta_ns < 5000)
225 dev->min_delta_ns = 5000;
227 dev->min_delta_ns += dev->min_delta_ns >> 1;
229 if (dev->min_delta_ns > MIN_DELTA_LIMIT)
230 dev->min_delta_ns = MIN_DELTA_LIMIT;
232 printk_deferred(KERN_WARNING
233 "CE: %s increased min_delta_ns to %llu nsec\n",
234 dev->name ? dev->name : "?",
235 (unsigned long long) dev->min_delta_ns);
240 * clockevents_program_min_delta - Set clock event device to the minimum delay.
241 * @dev: device to program
243 * Returns 0 on success, -ETIME when the retry loop failed.
245 static int clockevents_program_min_delta(struct clock_event_device *dev)
247 unsigned long long clc;
252 delta = dev->min_delta_ns;
253 dev->next_event = ktime_add_ns(ktime_get(), delta);
255 if (dev->state == CLOCK_EVT_STATE_SHUTDOWN)
259 clc = ((unsigned long long) delta * dev->mult) >> dev->shift;
260 if (dev->set_next_event((unsigned long) clc, dev) == 0)
265 * We tried 3 times to program the device with the
266 * given min_delta_ns. Try to increase the minimum
267 * delta, if that fails as well get out of here.
269 if (clockevents_increase_min_delta(dev))
276 #else /* CONFIG_GENERIC_CLOCKEVENTS_MIN_ADJUST */
279 * clockevents_program_min_delta - Set clock event device to the minimum delay.
280 * @dev: device to program
282 * Returns 0 on success, -ETIME when the retry loop failed.
284 static int clockevents_program_min_delta(struct clock_event_device *dev)
286 unsigned long long clc;
289 delta = dev->min_delta_ns;
290 dev->next_event = ktime_add_ns(ktime_get(), delta);
292 if (dev->state == CLOCK_EVT_STATE_SHUTDOWN)
296 clc = ((unsigned long long) delta * dev->mult) >> dev->shift;
297 return dev->set_next_event((unsigned long) clc, dev);
300 #endif /* CONFIG_GENERIC_CLOCKEVENTS_MIN_ADJUST */
303 * clockevents_program_event - Reprogram the clock event device.
304 * @dev: device to program
305 * @expires: absolute expiry time (monotonic clock)
306 * @force: program minimum delay if expires can not be set
308 * Returns 0 on success, -ETIME when the event is in the past.
310 int clockevents_program_event(struct clock_event_device *dev, ktime_t expires,
313 unsigned long long clc;
317 if (unlikely(expires.tv64 < 0)) {
322 dev->next_event = expires;
324 if (dev->state == CLOCK_EVT_STATE_SHUTDOWN)
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);
331 delta = ktime_to_ns(ktime_sub(expires, ktime_get()));
333 return force ? clockevents_program_min_delta(dev) : -ETIME;
335 delta = min(delta, (int64_t) dev->max_delta_ns);
336 delta = max(delta, (int64_t) dev->min_delta_ns);
338 clc = ((unsigned long long) delta * dev->mult) >> dev->shift;
339 rc = dev->set_next_event((unsigned long) clc, dev);
341 return (rc && force) ? clockevents_program_min_delta(dev) : rc;
345 * Called after a notify add to make devices available which were
346 * released from the notifier call.
348 static void clockevents_notify_released(void)
350 struct clock_event_device *dev;
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);
362 * Try to install a replacement clock event device
364 static int clockevents_replace(struct clock_event_device *ced)
366 struct clock_event_device *dev, *newdev = NULL;
368 list_for_each_entry(dev, &clockevent_devices, list) {
369 if (dev == ced || dev->state != CLOCK_EVT_STATE_DETACHED)
372 if (!tick_check_replacement(newdev, dev))
375 if (!try_module_get(dev->owner))
379 module_put(newdev->owner);
383 tick_install_replacement(newdev);
384 list_del_init(&ced->list);
386 return newdev ? 0 : -EBUSY;
390 * Called with clockevents_mutex and clockevents_lock held
392 static int __clockevents_try_unbind(struct clock_event_device *ced, int cpu)
394 /* Fast track. Device is unused */
395 if (ced->state == CLOCK_EVT_STATE_DETACHED) {
396 list_del_init(&ced->list);
400 return ced == per_cpu(tick_cpu_device, cpu).evtdev ? -EAGAIN : -EBUSY;
404 * SMP function call to unbind a device
406 static void __clockevents_unbind(void *arg)
408 struct ce_unbind *cu = arg;
411 raw_spin_lock(&clockevents_lock);
412 res = __clockevents_try_unbind(cu->ce, smp_processor_id());
414 res = clockevents_replace(cu->ce);
416 raw_spin_unlock(&clockevents_lock);
420 * Issues smp function call to unbind a per cpu device. Called with
421 * clockevents_mutex held.
423 static int clockevents_unbind(struct clock_event_device *ced, int cpu)
425 struct ce_unbind cu = { .ce = ced, .res = -ENODEV };
427 smp_call_function_single(cpu, __clockevents_unbind, &cu, 1);
432 * Unbind a clockevents device.
434 int clockevents_unbind_device(struct clock_event_device *ced, int cpu)
438 mutex_lock(&clockevents_mutex);
439 ret = clockevents_unbind(ced, cpu);
440 mutex_unlock(&clockevents_mutex);
443 EXPORT_SYMBOL_GPL(clockevents_unbind_device);
445 /* Sanity check of state transition callbacks */
446 static int clockevents_sanity_check(struct clock_event_device *dev)
448 /* Legacy set_mode() callback */
450 /* We shouldn't be supporting new modes now */
451 WARN_ON(dev->set_state_periodic || dev->set_state_oneshot ||
452 dev->set_state_shutdown || dev->tick_resume);
454 BUG_ON(dev->mode != CLOCK_EVT_MODE_UNUSED);
458 if (dev->features & CLOCK_EVT_FEAT_DUMMY)
461 /* New state-specific callbacks */
462 if (!dev->set_state_shutdown)
465 if ((dev->features & CLOCK_EVT_FEAT_PERIODIC) &&
466 !dev->set_state_periodic)
469 if ((dev->features & CLOCK_EVT_FEAT_ONESHOT) &&
470 !dev->set_state_oneshot)
477 * clockevents_register_device - register a clock event device
478 * @dev: device to register
480 void clockevents_register_device(struct clock_event_device *dev)
484 BUG_ON(clockevents_sanity_check(dev));
486 /* Initialize state to DETACHED */
487 dev->state = CLOCK_EVT_STATE_DETACHED;
490 WARN_ON(num_possible_cpus() > 1);
491 dev->cpumask = cpumask_of(smp_processor_id());
494 raw_spin_lock_irqsave(&clockevents_lock, flags);
496 list_add(&dev->list, &clockevent_devices);
497 tick_check_new_device(dev);
498 clockevents_notify_released();
500 raw_spin_unlock_irqrestore(&clockevents_lock, flags);
502 EXPORT_SYMBOL_GPL(clockevents_register_device);
504 void clockevents_config(struct clock_event_device *dev, u32 freq)
508 if (!(dev->features & CLOCK_EVT_FEAT_ONESHOT))
512 * Calculate the maximum number of seconds we can sleep. Limit
513 * to 10 minutes for hardware which can program more than
514 * 32bit ticks so we still get reasonable conversion values.
516 sec = dev->max_delta_ticks;
520 else if (sec > 600 && dev->max_delta_ticks > UINT_MAX)
523 clockevents_calc_mult_shift(dev, freq, sec);
524 dev->min_delta_ns = cev_delta2ns(dev->min_delta_ticks, dev, false);
525 dev->max_delta_ns = cev_delta2ns(dev->max_delta_ticks, dev, true);
529 * clockevents_config_and_register - Configure and register a clock event device
530 * @dev: device to register
531 * @freq: The clock frequency
532 * @min_delta: The minimum clock ticks to program in oneshot mode
533 * @max_delta: The maximum clock ticks to program in oneshot mode
535 * min/max_delta can be 0 for devices which do not support oneshot mode.
537 void clockevents_config_and_register(struct clock_event_device *dev,
538 u32 freq, unsigned long min_delta,
539 unsigned long max_delta)
541 dev->min_delta_ticks = min_delta;
542 dev->max_delta_ticks = max_delta;
543 clockevents_config(dev, freq);
544 clockevents_register_device(dev);
546 EXPORT_SYMBOL_GPL(clockevents_config_and_register);
548 int __clockevents_update_freq(struct clock_event_device *dev, u32 freq)
550 clockevents_config(dev, freq);
552 if (dev->state == CLOCK_EVT_STATE_ONESHOT)
553 return clockevents_program_event(dev, dev->next_event, false);
555 if (dev->state == CLOCK_EVT_STATE_PERIODIC)
556 return __clockevents_set_state(dev, CLOCK_EVT_STATE_PERIODIC);
562 * clockevents_update_freq - Update frequency and reprogram a clock event device.
563 * @dev: device to modify
564 * @freq: new device frequency
566 * Reconfigure and reprogram a clock event device in oneshot
567 * mode. Must be called on the cpu for which the device delivers per
568 * cpu timer events. If called for the broadcast device the core takes
569 * care of serialization.
571 * Returns 0 on success, -ETIME when the event is in the past.
573 int clockevents_update_freq(struct clock_event_device *dev, u32 freq)
578 local_irq_save(flags);
579 ret = tick_broadcast_update_freq(dev, freq);
581 ret = __clockevents_update_freq(dev, freq);
582 local_irq_restore(flags);
587 * Noop handler when we shut down an event device
589 void clockevents_handle_noop(struct clock_event_device *dev)
594 * clockevents_exchange_device - release and request clock devices
595 * @old: device to release (can be NULL)
596 * @new: device to request (can be NULL)
598 * Called from various tick functions with clockevents_lock held and
599 * interrupts disabled.
601 void clockevents_exchange_device(struct clock_event_device *old,
602 struct clock_event_device *new)
605 * Caller releases a clock event device. We queue it into the
606 * released list and do a notify add later.
609 module_put(old->owner);
610 clockevents_set_state(old, CLOCK_EVT_STATE_DETACHED);
611 list_del(&old->list);
612 list_add(&old->list, &clockevents_released);
616 BUG_ON(new->state != CLOCK_EVT_STATE_DETACHED);
617 clockevents_shutdown(new);
622 * clockevents_suspend - suspend clock devices
624 void clockevents_suspend(void)
626 struct clock_event_device *dev;
628 list_for_each_entry_reverse(dev, &clockevent_devices, list)
634 * clockevents_resume - resume clock devices
636 void clockevents_resume(void)
638 struct clock_event_device *dev;
640 list_for_each_entry(dev, &clockevent_devices, list)
645 #ifdef CONFIG_HOTPLUG_CPU
647 * tick_cleanup_dead_cpu - Cleanup the tick and clockevents of a dead cpu
649 void tick_cleanup_dead_cpu(int cpu)
651 struct clock_event_device *dev, *tmp;
654 raw_spin_lock_irqsave(&clockevents_lock, flags);
656 tick_shutdown_broadcast_oneshot(cpu);
657 tick_shutdown_broadcast(cpu);
660 * Unregister the clock event devices which were
661 * released from the users in the notify chain.
663 list_for_each_entry_safe(dev, tmp, &clockevents_released, list)
664 list_del(&dev->list);
666 * Now check whether the CPU has left unused per cpu devices
668 list_for_each_entry_safe(dev, tmp, &clockevent_devices, list) {
669 if (cpumask_test_cpu(cpu, dev->cpumask) &&
670 cpumask_weight(dev->cpumask) == 1 &&
671 !tick_is_broadcast_device(dev)) {
672 BUG_ON(dev->state != CLOCK_EVT_STATE_DETACHED);
673 list_del(&dev->list);
676 raw_spin_unlock_irqrestore(&clockevents_lock, flags);
681 struct bus_type clockevents_subsys = {
682 .name = "clockevents",
683 .dev_name = "clockevent",
686 static DEFINE_PER_CPU(struct device, tick_percpu_dev);
687 static struct tick_device *tick_get_tick_dev(struct device *dev);
689 static ssize_t sysfs_show_current_tick_dev(struct device *dev,
690 struct device_attribute *attr,
693 struct tick_device *td;
696 raw_spin_lock_irq(&clockevents_lock);
697 td = tick_get_tick_dev(dev);
698 if (td && td->evtdev)
699 count = snprintf(buf, PAGE_SIZE, "%s\n", td->evtdev->name);
700 raw_spin_unlock_irq(&clockevents_lock);
703 static DEVICE_ATTR(current_device, 0444, sysfs_show_current_tick_dev, NULL);
705 /* We don't support the abomination of removable broadcast devices */
706 static ssize_t sysfs_unbind_tick_dev(struct device *dev,
707 struct device_attribute *attr,
708 const char *buf, size_t count)
710 char name[CS_NAME_LEN];
711 ssize_t ret = sysfs_get_uname(buf, name, count);
712 struct clock_event_device *ce;
718 mutex_lock(&clockevents_mutex);
719 raw_spin_lock_irq(&clockevents_lock);
720 list_for_each_entry(ce, &clockevent_devices, list) {
721 if (!strcmp(ce->name, name)) {
722 ret = __clockevents_try_unbind(ce, dev->id);
726 raw_spin_unlock_irq(&clockevents_lock);
728 * We hold clockevents_mutex, so ce can't go away
731 ret = clockevents_unbind(ce, dev->id);
732 mutex_unlock(&clockevents_mutex);
733 return ret ? ret : count;
735 static DEVICE_ATTR(unbind_device, 0200, NULL, sysfs_unbind_tick_dev);
737 #ifdef CONFIG_GENERIC_CLOCKEVENTS_BROADCAST
738 static struct device tick_bc_dev = {
739 .init_name = "broadcast",
741 .bus = &clockevents_subsys,
744 static struct tick_device *tick_get_tick_dev(struct device *dev)
746 return dev == &tick_bc_dev ? tick_get_broadcast_device() :
747 &per_cpu(tick_cpu_device, dev->id);
750 static __init int tick_broadcast_init_sysfs(void)
752 int err = device_register(&tick_bc_dev);
755 err = device_create_file(&tick_bc_dev, &dev_attr_current_device);
759 static struct tick_device *tick_get_tick_dev(struct device *dev)
761 return &per_cpu(tick_cpu_device, dev->id);
763 static inline int tick_broadcast_init_sysfs(void) { return 0; }
766 static int __init tick_init_sysfs(void)
770 for_each_possible_cpu(cpu) {
771 struct device *dev = &per_cpu(tick_percpu_dev, cpu);
775 dev->bus = &clockevents_subsys;
776 err = device_register(dev);
778 err = device_create_file(dev, &dev_attr_current_device);
780 err = device_create_file(dev, &dev_attr_unbind_device);
784 return tick_broadcast_init_sysfs();
787 static int __init clockevents_init_sysfs(void)
789 int err = subsys_system_register(&clockevents_subsys, NULL);
792 err = tick_init_sysfs();
795 device_initcall(clockevents_init_sysfs);