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:
120 /* The clockevent device is getting replaced. Shut it down. */
122 case CLOCK_EVT_STATE_SHUTDOWN:
123 return dev->set_state_shutdown(dev);
125 case CLOCK_EVT_STATE_PERIODIC:
126 /* Core internal bug */
127 if (!(dev->features & CLOCK_EVT_FEAT_PERIODIC))
129 return dev->set_state_periodic(dev);
131 case CLOCK_EVT_STATE_ONESHOT:
132 /* Core internal bug */
133 if (!(dev->features & CLOCK_EVT_FEAT_ONESHOT))
135 return dev->set_state_oneshot(dev);
137 case CLOCK_EVT_STATE_ONESHOT_STOPPED:
138 /* Core internal bug */
139 if (WARN_ONCE(dev->state != CLOCK_EVT_STATE_ONESHOT,
140 "Current state: %d\n", dev->state))
143 if (dev->set_state_oneshot_stopped)
144 return dev->set_state_oneshot_stopped(dev);
154 * clockevents_set_state - set the operating state of a clock event device
155 * @dev: device to modify
158 * Must be called with interrupts disabled !
160 void clockevents_set_state(struct clock_event_device *dev,
161 enum clock_event_state state)
163 if (dev->state != state) {
164 if (__clockevents_set_state(dev, state))
170 * A nsec2cyc multiplicator of 0 is invalid and we'd crash
171 * on it, so fix it up and emit a warning:
173 if (state == CLOCK_EVT_STATE_ONESHOT) {
174 if (unlikely(!dev->mult)) {
183 * clockevents_shutdown - shutdown the device and clear next_event
184 * @dev: device to shutdown
186 void clockevents_shutdown(struct clock_event_device *dev)
188 clockevents_set_state(dev, CLOCK_EVT_STATE_SHUTDOWN);
189 dev->next_event.tv64 = KTIME_MAX;
193 * clockevents_tick_resume - Resume the tick device before using it again
194 * @dev: device to resume
196 int clockevents_tick_resume(struct clock_event_device *dev)
201 dev->set_mode(CLOCK_EVT_MODE_RESUME, dev);
202 dev->mode = CLOCK_EVT_MODE_RESUME;
203 } else if (dev->tick_resume) {
204 ret = dev->tick_resume(dev);
210 #ifdef CONFIG_GENERIC_CLOCKEVENTS_MIN_ADJUST
212 /* Limit min_delta to a jiffie */
213 #define MIN_DELTA_LIMIT (NSEC_PER_SEC / HZ)
216 * clockevents_increase_min_delta - raise minimum delta of a clock event device
217 * @dev: device to increase the minimum delta
219 * Returns 0 on success, -ETIME when the minimum delta reached the limit.
221 static int clockevents_increase_min_delta(struct clock_event_device *dev)
223 /* Nothing to do if we already reached the limit */
224 if (dev->min_delta_ns >= MIN_DELTA_LIMIT) {
225 printk_deferred(KERN_WARNING
226 "CE: Reprogramming failure. Giving up\n");
227 dev->next_event.tv64 = KTIME_MAX;
231 if (dev->min_delta_ns < 5000)
232 dev->min_delta_ns = 5000;
234 dev->min_delta_ns += dev->min_delta_ns >> 1;
236 if (dev->min_delta_ns > MIN_DELTA_LIMIT)
237 dev->min_delta_ns = MIN_DELTA_LIMIT;
239 printk_deferred(KERN_WARNING
240 "CE: %s increased min_delta_ns to %llu nsec\n",
241 dev->name ? dev->name : "?",
242 (unsigned long long) dev->min_delta_ns);
247 * clockevents_program_min_delta - Set clock event device to the minimum delay.
248 * @dev: device to program
250 * Returns 0 on success, -ETIME when the retry loop failed.
252 static int clockevents_program_min_delta(struct clock_event_device *dev)
254 unsigned long long clc;
259 delta = dev->min_delta_ns;
260 dev->next_event = ktime_add_ns(ktime_get(), delta);
262 if (dev->state == CLOCK_EVT_STATE_SHUTDOWN)
266 clc = ((unsigned long long) delta * dev->mult) >> dev->shift;
267 if (dev->set_next_event((unsigned long) clc, dev) == 0)
272 * We tried 3 times to program the device with the
273 * given min_delta_ns. Try to increase the minimum
274 * delta, if that fails as well get out of here.
276 if (clockevents_increase_min_delta(dev))
283 #else /* CONFIG_GENERIC_CLOCKEVENTS_MIN_ADJUST */
286 * clockevents_program_min_delta - Set clock event device to the minimum delay.
287 * @dev: device to program
289 * Returns 0 on success, -ETIME when the retry loop failed.
291 static int clockevents_program_min_delta(struct clock_event_device *dev)
293 unsigned long long clc;
296 delta = dev->min_delta_ns;
297 dev->next_event = ktime_add_ns(ktime_get(), delta);
299 if (dev->state == CLOCK_EVT_STATE_SHUTDOWN)
303 clc = ((unsigned long long) delta * dev->mult) >> dev->shift;
304 return dev->set_next_event((unsigned long) clc, dev);
307 #endif /* CONFIG_GENERIC_CLOCKEVENTS_MIN_ADJUST */
310 * clockevents_program_event - Reprogram the clock event device.
311 * @dev: device to program
312 * @expires: absolute expiry time (monotonic clock)
313 * @force: program minimum delay if expires can not be set
315 * Returns 0 on success, -ETIME when the event is in the past.
317 int clockevents_program_event(struct clock_event_device *dev, ktime_t expires,
320 unsigned long long clc;
324 if (unlikely(expires.tv64 < 0)) {
329 dev->next_event = expires;
331 if (dev->state == CLOCK_EVT_STATE_SHUTDOWN)
334 /* Shortcut for clockevent devices that can deal with ktime. */
335 if (dev->features & CLOCK_EVT_FEAT_KTIME)
336 return dev->set_next_ktime(expires, dev);
338 delta = ktime_to_ns(ktime_sub(expires, ktime_get()));
340 return force ? clockevents_program_min_delta(dev) : -ETIME;
342 delta = min(delta, (int64_t) dev->max_delta_ns);
343 delta = max(delta, (int64_t) dev->min_delta_ns);
345 clc = ((unsigned long long) delta * dev->mult) >> dev->shift;
346 rc = dev->set_next_event((unsigned long) clc, dev);
348 return (rc && force) ? clockevents_program_min_delta(dev) : rc;
352 * Called after a notify add to make devices available which were
353 * released from the notifier call.
355 static void clockevents_notify_released(void)
357 struct clock_event_device *dev;
359 while (!list_empty(&clockevents_released)) {
360 dev = list_entry(clockevents_released.next,
361 struct clock_event_device, list);
362 list_del(&dev->list);
363 list_add(&dev->list, &clockevent_devices);
364 tick_check_new_device(dev);
369 * Try to install a replacement clock event device
371 static int clockevents_replace(struct clock_event_device *ced)
373 struct clock_event_device *dev, *newdev = NULL;
375 list_for_each_entry(dev, &clockevent_devices, list) {
376 if (dev == ced || dev->state != CLOCK_EVT_STATE_DETACHED)
379 if (!tick_check_replacement(newdev, dev))
382 if (!try_module_get(dev->owner))
386 module_put(newdev->owner);
390 tick_install_replacement(newdev);
391 list_del_init(&ced->list);
393 return newdev ? 0 : -EBUSY;
397 * Called with clockevents_mutex and clockevents_lock held
399 static int __clockevents_try_unbind(struct clock_event_device *ced, int cpu)
401 /* Fast track. Device is unused */
402 if (ced->state == CLOCK_EVT_STATE_DETACHED) {
403 list_del_init(&ced->list);
407 return ced == per_cpu(tick_cpu_device, cpu).evtdev ? -EAGAIN : -EBUSY;
411 * SMP function call to unbind a device
413 static void __clockevents_unbind(void *arg)
415 struct ce_unbind *cu = arg;
418 raw_spin_lock(&clockevents_lock);
419 res = __clockevents_try_unbind(cu->ce, smp_processor_id());
421 res = clockevents_replace(cu->ce);
423 raw_spin_unlock(&clockevents_lock);
427 * Issues smp function call to unbind a per cpu device. Called with
428 * clockevents_mutex held.
430 static int clockevents_unbind(struct clock_event_device *ced, int cpu)
432 struct ce_unbind cu = { .ce = ced, .res = -ENODEV };
434 smp_call_function_single(cpu, __clockevents_unbind, &cu, 1);
439 * Unbind a clockevents device.
441 int clockevents_unbind_device(struct clock_event_device *ced, int cpu)
445 mutex_lock(&clockevents_mutex);
446 ret = clockevents_unbind(ced, cpu);
447 mutex_unlock(&clockevents_mutex);
450 EXPORT_SYMBOL_GPL(clockevents_unbind_device);
452 /* Sanity check of state transition callbacks */
453 static int clockevents_sanity_check(struct clock_event_device *dev)
455 /* Legacy set_mode() callback */
457 /* We shouldn't be supporting new modes now */
458 WARN_ON(dev->set_state_periodic || dev->set_state_oneshot ||
459 dev->set_state_shutdown || dev->tick_resume ||
460 dev->set_state_oneshot_stopped);
462 BUG_ON(dev->mode != CLOCK_EVT_MODE_UNUSED);
466 if (dev->features & CLOCK_EVT_FEAT_DUMMY)
469 /* New state-specific callbacks */
470 if (!dev->set_state_shutdown)
473 if ((dev->features & CLOCK_EVT_FEAT_PERIODIC) &&
474 !dev->set_state_periodic)
477 if ((dev->features & CLOCK_EVT_FEAT_ONESHOT) &&
478 !dev->set_state_oneshot)
485 * clockevents_register_device - register a clock event device
486 * @dev: device to register
488 void clockevents_register_device(struct clock_event_device *dev)
492 BUG_ON(clockevents_sanity_check(dev));
494 /* Initialize state to DETACHED */
495 dev->state = CLOCK_EVT_STATE_DETACHED;
498 WARN_ON(num_possible_cpus() > 1);
499 dev->cpumask = cpumask_of(smp_processor_id());
502 raw_spin_lock_irqsave(&clockevents_lock, flags);
504 list_add(&dev->list, &clockevent_devices);
505 tick_check_new_device(dev);
506 clockevents_notify_released();
508 raw_spin_unlock_irqrestore(&clockevents_lock, flags);
510 EXPORT_SYMBOL_GPL(clockevents_register_device);
512 void clockevents_config(struct clock_event_device *dev, u32 freq)
516 if (!(dev->features & CLOCK_EVT_FEAT_ONESHOT))
520 * Calculate the maximum number of seconds we can sleep. Limit
521 * to 10 minutes for hardware which can program more than
522 * 32bit ticks so we still get reasonable conversion values.
524 sec = dev->max_delta_ticks;
528 else if (sec > 600 && dev->max_delta_ticks > UINT_MAX)
531 clockevents_calc_mult_shift(dev, freq, sec);
532 dev->min_delta_ns = cev_delta2ns(dev->min_delta_ticks, dev, false);
533 dev->max_delta_ns = cev_delta2ns(dev->max_delta_ticks, dev, true);
537 * clockevents_config_and_register - Configure and register a clock event device
538 * @dev: device to register
539 * @freq: The clock frequency
540 * @min_delta: The minimum clock ticks to program in oneshot mode
541 * @max_delta: The maximum clock ticks to program in oneshot mode
543 * min/max_delta can be 0 for devices which do not support oneshot mode.
545 void clockevents_config_and_register(struct clock_event_device *dev,
546 u32 freq, unsigned long min_delta,
547 unsigned long max_delta)
549 dev->min_delta_ticks = min_delta;
550 dev->max_delta_ticks = max_delta;
551 clockevents_config(dev, freq);
552 clockevents_register_device(dev);
554 EXPORT_SYMBOL_GPL(clockevents_config_and_register);
556 int __clockevents_update_freq(struct clock_event_device *dev, u32 freq)
558 clockevents_config(dev, freq);
560 if (dev->state == CLOCK_EVT_STATE_ONESHOT)
561 return clockevents_program_event(dev, dev->next_event, false);
563 if (dev->state == CLOCK_EVT_STATE_PERIODIC)
564 return __clockevents_set_state(dev, CLOCK_EVT_STATE_PERIODIC);
570 * clockevents_update_freq - Update frequency and reprogram a clock event device.
571 * @dev: device to modify
572 * @freq: new device frequency
574 * Reconfigure and reprogram a clock event device in oneshot
575 * mode. Must be called on the cpu for which the device delivers per
576 * cpu timer events. If called for the broadcast device the core takes
577 * care of serialization.
579 * Returns 0 on success, -ETIME when the event is in the past.
581 int clockevents_update_freq(struct clock_event_device *dev, u32 freq)
586 local_irq_save(flags);
587 ret = tick_broadcast_update_freq(dev, freq);
589 ret = __clockevents_update_freq(dev, freq);
590 local_irq_restore(flags);
595 * Noop handler when we shut down an event device
597 void clockevents_handle_noop(struct clock_event_device *dev)
602 * clockevents_exchange_device - release and request clock devices
603 * @old: device to release (can be NULL)
604 * @new: device to request (can be NULL)
606 * Called from various tick functions with clockevents_lock held and
607 * interrupts disabled.
609 void clockevents_exchange_device(struct clock_event_device *old,
610 struct clock_event_device *new)
613 * Caller releases a clock event device. We queue it into the
614 * released list and do a notify add later.
617 module_put(old->owner);
618 clockevents_set_state(old, CLOCK_EVT_STATE_DETACHED);
619 list_del(&old->list);
620 list_add(&old->list, &clockevents_released);
624 BUG_ON(new->state != CLOCK_EVT_STATE_DETACHED);
625 clockevents_shutdown(new);
630 * clockevents_suspend - suspend clock devices
632 void clockevents_suspend(void)
634 struct clock_event_device *dev;
636 list_for_each_entry_reverse(dev, &clockevent_devices, list)
642 * clockevents_resume - resume clock devices
644 void clockevents_resume(void)
646 struct clock_event_device *dev;
648 list_for_each_entry(dev, &clockevent_devices, list)
653 #ifdef CONFIG_HOTPLUG_CPU
655 * tick_cleanup_dead_cpu - Cleanup the tick and clockevents of a dead cpu
657 void tick_cleanup_dead_cpu(int cpu)
659 struct clock_event_device *dev, *tmp;
662 raw_spin_lock_irqsave(&clockevents_lock, flags);
664 tick_shutdown_broadcast_oneshot(cpu);
665 tick_shutdown_broadcast(cpu);
668 * Unregister the clock event devices which were
669 * released from the users in the notify chain.
671 list_for_each_entry_safe(dev, tmp, &clockevents_released, list)
672 list_del(&dev->list);
674 * Now check whether the CPU has left unused per cpu devices
676 list_for_each_entry_safe(dev, tmp, &clockevent_devices, list) {
677 if (cpumask_test_cpu(cpu, dev->cpumask) &&
678 cpumask_weight(dev->cpumask) == 1 &&
679 !tick_is_broadcast_device(dev)) {
680 BUG_ON(dev->state != CLOCK_EVT_STATE_DETACHED);
681 list_del(&dev->list);
684 raw_spin_unlock_irqrestore(&clockevents_lock, flags);
689 struct bus_type clockevents_subsys = {
690 .name = "clockevents",
691 .dev_name = "clockevent",
694 static DEFINE_PER_CPU(struct device, tick_percpu_dev);
695 static struct tick_device *tick_get_tick_dev(struct device *dev);
697 static ssize_t sysfs_show_current_tick_dev(struct device *dev,
698 struct device_attribute *attr,
701 struct tick_device *td;
704 raw_spin_lock_irq(&clockevents_lock);
705 td = tick_get_tick_dev(dev);
706 if (td && td->evtdev)
707 count = snprintf(buf, PAGE_SIZE, "%s\n", td->evtdev->name);
708 raw_spin_unlock_irq(&clockevents_lock);
711 static DEVICE_ATTR(current_device, 0444, sysfs_show_current_tick_dev, NULL);
713 /* We don't support the abomination of removable broadcast devices */
714 static ssize_t sysfs_unbind_tick_dev(struct device *dev,
715 struct device_attribute *attr,
716 const char *buf, size_t count)
718 char name[CS_NAME_LEN];
719 ssize_t ret = sysfs_get_uname(buf, name, count);
720 struct clock_event_device *ce;
726 mutex_lock(&clockevents_mutex);
727 raw_spin_lock_irq(&clockevents_lock);
728 list_for_each_entry(ce, &clockevent_devices, list) {
729 if (!strcmp(ce->name, name)) {
730 ret = __clockevents_try_unbind(ce, dev->id);
734 raw_spin_unlock_irq(&clockevents_lock);
736 * We hold clockevents_mutex, so ce can't go away
739 ret = clockevents_unbind(ce, dev->id);
740 mutex_unlock(&clockevents_mutex);
741 return ret ? ret : count;
743 static DEVICE_ATTR(unbind_device, 0200, NULL, sysfs_unbind_tick_dev);
745 #ifdef CONFIG_GENERIC_CLOCKEVENTS_BROADCAST
746 static struct device tick_bc_dev = {
747 .init_name = "broadcast",
749 .bus = &clockevents_subsys,
752 static struct tick_device *tick_get_tick_dev(struct device *dev)
754 return dev == &tick_bc_dev ? tick_get_broadcast_device() :
755 &per_cpu(tick_cpu_device, dev->id);
758 static __init int tick_broadcast_init_sysfs(void)
760 int err = device_register(&tick_bc_dev);
763 err = device_create_file(&tick_bc_dev, &dev_attr_current_device);
767 static struct tick_device *tick_get_tick_dev(struct device *dev)
769 return &per_cpu(tick_cpu_device, dev->id);
771 static inline int tick_broadcast_init_sysfs(void) { return 0; }
774 static int __init tick_init_sysfs(void)
778 for_each_possible_cpu(cpu) {
779 struct device *dev = &per_cpu(tick_percpu_dev, cpu);
783 dev->bus = &clockevents_subsys;
784 err = device_register(dev);
786 err = device_create_file(dev, &dev_attr_current_device);
788 err = device_create_file(dev, &dev_attr_unbind_device);
792 return tick_broadcast_init_sysfs();
795 static int __init clockevents_init_sysfs(void)
797 int err = subsys_system_register(&clockevents_subsys, NULL);
800 err = tick_init_sysfs();
803 device_initcall(clockevents_init_sysfs);