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_switch_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(!clockevent_state_oneshot(dev),
140 "Current state: %d\n",
141 clockevent_get_state(dev)))
144 if (dev->set_state_oneshot_stopped)
145 return dev->set_state_oneshot_stopped(dev);
155 * clockevents_switch_state - set the operating state of a clock event device
156 * @dev: device to modify
159 * Must be called with interrupts disabled !
161 void clockevents_switch_state(struct clock_event_device *dev,
162 enum clock_event_state state)
164 if (clockevent_get_state(dev) != state) {
165 if (__clockevents_switch_state(dev, state))
168 clockevent_set_state(dev, state);
171 * A nsec2cyc multiplicator of 0 is invalid and we'd crash
172 * on it, so fix it up and emit a warning:
174 if (clockevent_state_oneshot(dev)) {
175 if (unlikely(!dev->mult)) {
184 * clockevents_shutdown - shutdown the device and clear next_event
185 * @dev: device to shutdown
187 void clockevents_shutdown(struct clock_event_device *dev)
189 clockevents_switch_state(dev, CLOCK_EVT_STATE_SHUTDOWN);
190 dev->next_event.tv64 = KTIME_MAX;
194 * clockevents_tick_resume - Resume the tick device before using it again
195 * @dev: device to resume
197 int clockevents_tick_resume(struct clock_event_device *dev)
202 dev->set_mode(CLOCK_EVT_MODE_RESUME, dev);
203 dev->mode = CLOCK_EVT_MODE_RESUME;
204 } else if (dev->tick_resume) {
205 ret = dev->tick_resume(dev);
211 #ifdef CONFIG_GENERIC_CLOCKEVENTS_MIN_ADJUST
213 /* Limit min_delta to a jiffie */
214 #define MIN_DELTA_LIMIT (NSEC_PER_SEC / HZ)
217 * clockevents_increase_min_delta - raise minimum delta of a clock event device
218 * @dev: device to increase the minimum delta
220 * Returns 0 on success, -ETIME when the minimum delta reached the limit.
222 static int clockevents_increase_min_delta(struct clock_event_device *dev)
224 /* Nothing to do if we already reached the limit */
225 if (dev->min_delta_ns >= MIN_DELTA_LIMIT) {
226 printk_deferred(KERN_WARNING
227 "CE: Reprogramming failure. Giving up\n");
228 dev->next_event.tv64 = KTIME_MAX;
232 if (dev->min_delta_ns < 5000)
233 dev->min_delta_ns = 5000;
235 dev->min_delta_ns += dev->min_delta_ns >> 1;
237 if (dev->min_delta_ns > MIN_DELTA_LIMIT)
238 dev->min_delta_ns = MIN_DELTA_LIMIT;
240 printk_deferred(KERN_WARNING
241 "CE: %s increased min_delta_ns to %llu nsec\n",
242 dev->name ? dev->name : "?",
243 (unsigned long long) dev->min_delta_ns);
248 * clockevents_program_min_delta - Set clock event device to the minimum delay.
249 * @dev: device to program
251 * Returns 0 on success, -ETIME when the retry loop failed.
253 static int clockevents_program_min_delta(struct clock_event_device *dev)
255 unsigned long long clc;
260 delta = dev->min_delta_ns;
261 dev->next_event = ktime_add_ns(ktime_get(), delta);
263 if (clockevent_state_shutdown(dev))
267 clc = ((unsigned long long) delta * dev->mult) >> dev->shift;
268 if (dev->set_next_event((unsigned long) clc, dev) == 0)
273 * We tried 3 times to program the device with the
274 * given min_delta_ns. Try to increase the minimum
275 * delta, if that fails as well get out of here.
277 if (clockevents_increase_min_delta(dev))
284 #else /* CONFIG_GENERIC_CLOCKEVENTS_MIN_ADJUST */
287 * clockevents_program_min_delta - Set clock event device to the minimum delay.
288 * @dev: device to program
290 * Returns 0 on success, -ETIME when the retry loop failed.
292 static int clockevents_program_min_delta(struct clock_event_device *dev)
294 unsigned long long clc;
297 delta = dev->min_delta_ns;
298 dev->next_event = ktime_add_ns(ktime_get(), delta);
300 if (clockevent_state_shutdown(dev))
304 clc = ((unsigned long long) delta * dev->mult) >> dev->shift;
305 return dev->set_next_event((unsigned long) clc, dev);
308 #endif /* CONFIG_GENERIC_CLOCKEVENTS_MIN_ADJUST */
311 * clockevents_program_event - Reprogram the clock event device.
312 * @dev: device to program
313 * @expires: absolute expiry time (monotonic clock)
314 * @force: program minimum delay if expires can not be set
316 * Returns 0 on success, -ETIME when the event is in the past.
318 int clockevents_program_event(struct clock_event_device *dev, ktime_t expires,
321 unsigned long long clc;
325 if (unlikely(expires.tv64 < 0)) {
330 dev->next_event = expires;
332 if (clockevent_state_shutdown(dev))
335 /* We must be in ONESHOT state here */
336 WARN_ONCE(!clockevent_state_oneshot(dev), "Current state: %d\n",
337 clockevent_get_state(dev));
339 /* Shortcut for clockevent devices that can deal with ktime. */
340 if (dev->features & CLOCK_EVT_FEAT_KTIME)
341 return dev->set_next_ktime(expires, dev);
343 delta = ktime_to_ns(ktime_sub(expires, ktime_get()));
345 return force ? clockevents_program_min_delta(dev) : -ETIME;
347 delta = min(delta, (int64_t) dev->max_delta_ns);
348 delta = max(delta, (int64_t) dev->min_delta_ns);
350 clc = ((unsigned long long) delta * dev->mult) >> dev->shift;
351 rc = dev->set_next_event((unsigned long) clc, dev);
353 return (rc && force) ? clockevents_program_min_delta(dev) : rc;
357 * Called after a notify add to make devices available which were
358 * released from the notifier call.
360 static void clockevents_notify_released(void)
362 struct clock_event_device *dev;
364 while (!list_empty(&clockevents_released)) {
365 dev = list_entry(clockevents_released.next,
366 struct clock_event_device, list);
367 list_del(&dev->list);
368 list_add(&dev->list, &clockevent_devices);
369 tick_check_new_device(dev);
374 * Try to install a replacement clock event device
376 static int clockevents_replace(struct clock_event_device *ced)
378 struct clock_event_device *dev, *newdev = NULL;
380 list_for_each_entry(dev, &clockevent_devices, list) {
381 if (dev == ced || !clockevent_state_detached(dev))
384 if (!tick_check_replacement(newdev, dev))
387 if (!try_module_get(dev->owner))
391 module_put(newdev->owner);
395 tick_install_replacement(newdev);
396 list_del_init(&ced->list);
398 return newdev ? 0 : -EBUSY;
402 * Called with clockevents_mutex and clockevents_lock held
404 static int __clockevents_try_unbind(struct clock_event_device *ced, int cpu)
406 /* Fast track. Device is unused */
407 if (clockevent_state_detached(ced)) {
408 list_del_init(&ced->list);
412 return ced == per_cpu(tick_cpu_device, cpu).evtdev ? -EAGAIN : -EBUSY;
416 * SMP function call to unbind a device
418 static void __clockevents_unbind(void *arg)
420 struct ce_unbind *cu = arg;
423 raw_spin_lock(&clockevents_lock);
424 res = __clockevents_try_unbind(cu->ce, smp_processor_id());
426 res = clockevents_replace(cu->ce);
428 raw_spin_unlock(&clockevents_lock);
432 * Issues smp function call to unbind a per cpu device. Called with
433 * clockevents_mutex held.
435 static int clockevents_unbind(struct clock_event_device *ced, int cpu)
437 struct ce_unbind cu = { .ce = ced, .res = -ENODEV };
439 smp_call_function_single(cpu, __clockevents_unbind, &cu, 1);
444 * Unbind a clockevents device.
446 int clockevents_unbind_device(struct clock_event_device *ced, int cpu)
450 mutex_lock(&clockevents_mutex);
451 ret = clockevents_unbind(ced, cpu);
452 mutex_unlock(&clockevents_mutex);
455 EXPORT_SYMBOL_GPL(clockevents_unbind_device);
457 /* Sanity check of state transition callbacks */
458 static int clockevents_sanity_check(struct clock_event_device *dev)
460 /* Legacy set_mode() callback */
462 /* We shouldn't be supporting new modes now */
463 WARN_ON(dev->set_state_periodic || dev->set_state_oneshot ||
464 dev->set_state_shutdown || dev->tick_resume ||
465 dev->set_state_oneshot_stopped);
467 BUG_ON(dev->mode != CLOCK_EVT_MODE_UNUSED);
471 if (dev->features & CLOCK_EVT_FEAT_DUMMY)
474 /* New state-specific callbacks */
475 if (!dev->set_state_shutdown)
478 if ((dev->features & CLOCK_EVT_FEAT_PERIODIC) &&
479 !dev->set_state_periodic)
482 if ((dev->features & CLOCK_EVT_FEAT_ONESHOT) &&
483 !dev->set_state_oneshot)
490 * clockevents_register_device - register a clock event device
491 * @dev: device to register
493 void clockevents_register_device(struct clock_event_device *dev)
497 BUG_ON(clockevents_sanity_check(dev));
499 /* Initialize state to DETACHED */
500 clockevent_set_state(dev, CLOCK_EVT_STATE_DETACHED);
503 WARN_ON(num_possible_cpus() > 1);
504 dev->cpumask = cpumask_of(smp_processor_id());
507 raw_spin_lock_irqsave(&clockevents_lock, flags);
509 list_add(&dev->list, &clockevent_devices);
510 tick_check_new_device(dev);
511 clockevents_notify_released();
513 raw_spin_unlock_irqrestore(&clockevents_lock, flags);
515 EXPORT_SYMBOL_GPL(clockevents_register_device);
517 void clockevents_config(struct clock_event_device *dev, u32 freq)
521 if (!(dev->features & CLOCK_EVT_FEAT_ONESHOT))
525 * Calculate the maximum number of seconds we can sleep. Limit
526 * to 10 minutes for hardware which can program more than
527 * 32bit ticks so we still get reasonable conversion values.
529 sec = dev->max_delta_ticks;
533 else if (sec > 600 && dev->max_delta_ticks > UINT_MAX)
536 clockevents_calc_mult_shift(dev, freq, sec);
537 dev->min_delta_ns = cev_delta2ns(dev->min_delta_ticks, dev, false);
538 dev->max_delta_ns = cev_delta2ns(dev->max_delta_ticks, dev, true);
542 * clockevents_config_and_register - Configure and register a clock event device
543 * @dev: device to register
544 * @freq: The clock frequency
545 * @min_delta: The minimum clock ticks to program in oneshot mode
546 * @max_delta: The maximum clock ticks to program in oneshot mode
548 * min/max_delta can be 0 for devices which do not support oneshot mode.
550 void clockevents_config_and_register(struct clock_event_device *dev,
551 u32 freq, unsigned long min_delta,
552 unsigned long max_delta)
554 dev->min_delta_ticks = min_delta;
555 dev->max_delta_ticks = max_delta;
556 clockevents_config(dev, freq);
557 clockevents_register_device(dev);
559 EXPORT_SYMBOL_GPL(clockevents_config_and_register);
561 int __clockevents_update_freq(struct clock_event_device *dev, u32 freq)
563 clockevents_config(dev, freq);
565 if (clockevent_state_oneshot(dev))
566 return clockevents_program_event(dev, dev->next_event, false);
568 if (clockevent_state_periodic(dev))
569 return __clockevents_switch_state(dev, CLOCK_EVT_STATE_PERIODIC);
575 * clockevents_update_freq - Update frequency and reprogram a clock event device.
576 * @dev: device to modify
577 * @freq: new device frequency
579 * Reconfigure and reprogram a clock event device in oneshot
580 * mode. Must be called on the cpu for which the device delivers per
581 * cpu timer events. If called for the broadcast device the core takes
582 * care of serialization.
584 * Returns 0 on success, -ETIME when the event is in the past.
586 int clockevents_update_freq(struct clock_event_device *dev, u32 freq)
591 local_irq_save(flags);
592 ret = tick_broadcast_update_freq(dev, freq);
594 ret = __clockevents_update_freq(dev, freq);
595 local_irq_restore(flags);
600 * Noop handler when we shut down an event device
602 void clockevents_handle_noop(struct clock_event_device *dev)
607 * clockevents_exchange_device - release and request clock devices
608 * @old: device to release (can be NULL)
609 * @new: device to request (can be NULL)
611 * Called from various tick functions with clockevents_lock held and
612 * interrupts disabled.
614 void clockevents_exchange_device(struct clock_event_device *old,
615 struct clock_event_device *new)
618 * Caller releases a clock event device. We queue it into the
619 * released list and do a notify add later.
622 module_put(old->owner);
623 clockevents_switch_state(old, CLOCK_EVT_STATE_DETACHED);
624 list_del(&old->list);
625 list_add(&old->list, &clockevents_released);
629 BUG_ON(!clockevent_state_detached(new));
630 clockevents_shutdown(new);
635 * clockevents_suspend - suspend clock devices
637 void clockevents_suspend(void)
639 struct clock_event_device *dev;
641 list_for_each_entry_reverse(dev, &clockevent_devices, list)
642 if (dev->suspend && !clockevent_state_detached(dev))
647 * clockevents_resume - resume clock devices
649 void clockevents_resume(void)
651 struct clock_event_device *dev;
653 list_for_each_entry(dev, &clockevent_devices, list)
654 if (dev->resume && !clockevent_state_detached(dev))
658 #ifdef CONFIG_HOTPLUG_CPU
660 * tick_cleanup_dead_cpu - Cleanup the tick and clockevents of a dead cpu
662 void tick_cleanup_dead_cpu(int cpu)
664 struct clock_event_device *dev, *tmp;
667 raw_spin_lock_irqsave(&clockevents_lock, flags);
669 tick_shutdown_broadcast_oneshot(cpu);
670 tick_shutdown_broadcast(cpu);
673 * Unregister the clock event devices which were
674 * released from the users in the notify chain.
676 list_for_each_entry_safe(dev, tmp, &clockevents_released, list)
677 list_del(&dev->list);
679 * Now check whether the CPU has left unused per cpu devices
681 list_for_each_entry_safe(dev, tmp, &clockevent_devices, list) {
682 if (cpumask_test_cpu(cpu, dev->cpumask) &&
683 cpumask_weight(dev->cpumask) == 1 &&
684 !tick_is_broadcast_device(dev)) {
685 BUG_ON(!clockevent_state_detached(dev));
686 list_del(&dev->list);
689 raw_spin_unlock_irqrestore(&clockevents_lock, flags);
694 struct bus_type clockevents_subsys = {
695 .name = "clockevents",
696 .dev_name = "clockevent",
699 static DEFINE_PER_CPU(struct device, tick_percpu_dev);
700 static struct tick_device *tick_get_tick_dev(struct device *dev);
702 static ssize_t sysfs_show_current_tick_dev(struct device *dev,
703 struct device_attribute *attr,
706 struct tick_device *td;
709 raw_spin_lock_irq(&clockevents_lock);
710 td = tick_get_tick_dev(dev);
711 if (td && td->evtdev)
712 count = snprintf(buf, PAGE_SIZE, "%s\n", td->evtdev->name);
713 raw_spin_unlock_irq(&clockevents_lock);
716 static DEVICE_ATTR(current_device, 0444, sysfs_show_current_tick_dev, NULL);
718 /* We don't support the abomination of removable broadcast devices */
719 static ssize_t sysfs_unbind_tick_dev(struct device *dev,
720 struct device_attribute *attr,
721 const char *buf, size_t count)
723 char name[CS_NAME_LEN];
724 ssize_t ret = sysfs_get_uname(buf, name, count);
725 struct clock_event_device *ce;
731 mutex_lock(&clockevents_mutex);
732 raw_spin_lock_irq(&clockevents_lock);
733 list_for_each_entry(ce, &clockevent_devices, list) {
734 if (!strcmp(ce->name, name)) {
735 ret = __clockevents_try_unbind(ce, dev->id);
739 raw_spin_unlock_irq(&clockevents_lock);
741 * We hold clockevents_mutex, so ce can't go away
744 ret = clockevents_unbind(ce, dev->id);
745 mutex_unlock(&clockevents_mutex);
746 return ret ? ret : count;
748 static DEVICE_ATTR(unbind_device, 0200, NULL, sysfs_unbind_tick_dev);
750 #ifdef CONFIG_GENERIC_CLOCKEVENTS_BROADCAST
751 static struct device tick_bc_dev = {
752 .init_name = "broadcast",
754 .bus = &clockevents_subsys,
757 static struct tick_device *tick_get_tick_dev(struct device *dev)
759 return dev == &tick_bc_dev ? tick_get_broadcast_device() :
760 &per_cpu(tick_cpu_device, dev->id);
763 static __init int tick_broadcast_init_sysfs(void)
765 int err = device_register(&tick_bc_dev);
768 err = device_create_file(&tick_bc_dev, &dev_attr_current_device);
772 static struct tick_device *tick_get_tick_dev(struct device *dev)
774 return &per_cpu(tick_cpu_device, dev->id);
776 static inline int tick_broadcast_init_sysfs(void) { return 0; }
779 static int __init tick_init_sysfs(void)
783 for_each_possible_cpu(cpu) {
784 struct device *dev = &per_cpu(tick_percpu_dev, cpu);
788 dev->bus = &clockevents_subsys;
789 err = device_register(dev);
791 err = device_create_file(dev, &dev_attr_current_device);
793 err = device_create_file(dev, &dev_attr_unbind_device);
797 return tick_broadcast_init_sysfs();
800 static int __init clockevents_init_sysfs(void)
802 int err = subsys_system_register(&clockevents_subsys, NULL);
805 err = tick_init_sysfs();
808 device_initcall(clockevents_init_sysfs);