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 <= (1U << 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);
98 * clockevents_set_mode - set the operating mode of a clock event device
99 * @dev: device to modify
102 * Must be called with interrupts disabled !
104 void clockevents_set_mode(struct clock_event_device *dev,
105 enum clock_event_mode mode)
107 if (dev->mode != mode) {
108 dev->set_mode(mode, dev);
112 * A nsec2cyc multiplicator of 0 is invalid and we'd crash
113 * on it, so fix it up and emit a warning:
115 if (mode == CLOCK_EVT_MODE_ONESHOT) {
116 if (unlikely(!dev->mult)) {
125 * clockevents_shutdown - shutdown the device and clear next_event
126 * @dev: device to shutdown
128 void clockevents_shutdown(struct clock_event_device *dev)
130 clockevents_set_mode(dev, CLOCK_EVT_MODE_SHUTDOWN);
131 dev->next_event.tv64 = KTIME_MAX;
134 #ifdef CONFIG_GENERIC_CLOCKEVENTS_MIN_ADJUST
136 /* Limit min_delta to a jiffie */
137 #define MIN_DELTA_LIMIT (NSEC_PER_SEC / HZ)
140 * clockevents_increase_min_delta - raise minimum delta of a clock event device
141 * @dev: device to increase the minimum delta
143 * Returns 0 on success, -ETIME when the minimum delta reached the limit.
145 static int clockevents_increase_min_delta(struct clock_event_device *dev)
147 /* Nothing to do if we already reached the limit */
148 if (dev->min_delta_ns >= MIN_DELTA_LIMIT) {
149 printk_deferred(KERN_WARNING
150 "CE: Reprogramming failure. Giving up\n");
151 dev->next_event.tv64 = KTIME_MAX;
155 if (dev->min_delta_ns < 5000)
156 dev->min_delta_ns = 5000;
158 dev->min_delta_ns += dev->min_delta_ns >> 1;
160 if (dev->min_delta_ns > MIN_DELTA_LIMIT)
161 dev->min_delta_ns = MIN_DELTA_LIMIT;
163 printk_deferred(KERN_WARNING
164 "CE: %s increased min_delta_ns to %llu nsec\n",
165 dev->name ? dev->name : "?",
166 (unsigned long long) dev->min_delta_ns);
171 * clockevents_program_min_delta - Set clock event device to the minimum delay.
172 * @dev: device to program
174 * Returns 0 on success, -ETIME when the retry loop failed.
176 static int clockevents_program_min_delta(struct clock_event_device *dev)
178 unsigned long long clc;
183 delta = dev->min_delta_ns;
184 dev->next_event = ktime_add_ns(ktime_get(), delta);
186 if (dev->mode == CLOCK_EVT_MODE_SHUTDOWN)
190 clc = ((unsigned long long) delta * dev->mult) >> dev->shift;
191 if (dev->set_next_event((unsigned long) clc, dev) == 0)
196 * We tried 3 times to program the device with the
197 * given min_delta_ns. Try to increase the minimum
198 * delta, if that fails as well get out of here.
200 if (clockevents_increase_min_delta(dev))
207 #else /* CONFIG_GENERIC_CLOCKEVENTS_MIN_ADJUST */
210 * clockevents_program_min_delta - Set clock event device to the minimum delay.
211 * @dev: device to program
213 * Returns 0 on success, -ETIME when the retry loop failed.
215 static int clockevents_program_min_delta(struct clock_event_device *dev)
217 unsigned long long clc;
220 delta = dev->min_delta_ns;
221 dev->next_event = ktime_add_ns(ktime_get(), delta);
223 if (dev->mode == CLOCK_EVT_MODE_SHUTDOWN)
227 clc = ((unsigned long long) delta * dev->mult) >> dev->shift;
228 return dev->set_next_event((unsigned long) clc, dev);
231 #endif /* CONFIG_GENERIC_CLOCKEVENTS_MIN_ADJUST */
234 * clockevents_program_event - Reprogram the clock event device.
235 * @dev: device to program
236 * @expires: absolute expiry time (monotonic clock)
237 * @force: program minimum delay if expires can not be set
239 * Returns 0 on success, -ETIME when the event is in the past.
241 int clockevents_program_event(struct clock_event_device *dev, ktime_t expires,
244 unsigned long long clc;
248 if (unlikely(expires.tv64 < 0)) {
253 dev->next_event = expires;
255 if (dev->mode == CLOCK_EVT_MODE_SHUTDOWN)
258 /* Shortcut for clockevent devices that can deal with ktime. */
259 if (dev->features & CLOCK_EVT_FEAT_KTIME)
260 return dev->set_next_ktime(expires, dev);
262 delta = ktime_to_ns(ktime_sub(expires, ktime_get()));
264 return force ? clockevents_program_min_delta(dev) : -ETIME;
266 delta = min(delta, (int64_t) dev->max_delta_ns);
267 delta = max(delta, (int64_t) dev->min_delta_ns);
269 clc = ((unsigned long long) delta * dev->mult) >> dev->shift;
270 rc = dev->set_next_event((unsigned long) clc, dev);
272 return (rc && force) ? clockevents_program_min_delta(dev) : rc;
276 * Called after a notify add to make devices available which were
277 * released from the notifier call.
279 static void clockevents_notify_released(void)
281 struct clock_event_device *dev;
283 while (!list_empty(&clockevents_released)) {
284 dev = list_entry(clockevents_released.next,
285 struct clock_event_device, list);
286 list_del(&dev->list);
287 list_add(&dev->list, &clockevent_devices);
288 tick_check_new_device(dev);
293 * Try to install a replacement clock event device
295 static int clockevents_replace(struct clock_event_device *ced)
297 struct clock_event_device *dev, *newdev = NULL;
299 list_for_each_entry(dev, &clockevent_devices, list) {
300 if (dev == ced || dev->mode != CLOCK_EVT_MODE_UNUSED)
303 if (!tick_check_replacement(newdev, dev))
306 if (!try_module_get(dev->owner))
310 module_put(newdev->owner);
314 tick_install_replacement(newdev);
315 list_del_init(&ced->list);
317 return newdev ? 0 : -EBUSY;
321 * Called with clockevents_mutex and clockevents_lock held
323 static int __clockevents_try_unbind(struct clock_event_device *ced, int cpu)
325 /* Fast track. Device is unused */
326 if (ced->mode == CLOCK_EVT_MODE_UNUSED) {
327 list_del_init(&ced->list);
331 return ced == per_cpu(tick_cpu_device, cpu).evtdev ? -EAGAIN : -EBUSY;
335 * SMP function call to unbind a device
337 static void __clockevents_unbind(void *arg)
339 struct ce_unbind *cu = arg;
342 raw_spin_lock(&clockevents_lock);
343 res = __clockevents_try_unbind(cu->ce, smp_processor_id());
345 res = clockevents_replace(cu->ce);
347 raw_spin_unlock(&clockevents_lock);
351 * Issues smp function call to unbind a per cpu device. Called with
352 * clockevents_mutex held.
354 static int clockevents_unbind(struct clock_event_device *ced, int cpu)
356 struct ce_unbind cu = { .ce = ced, .res = -ENODEV };
358 smp_call_function_single(cpu, __clockevents_unbind, &cu, 1);
363 * Unbind a clockevents device.
365 int clockevents_unbind_device(struct clock_event_device *ced, int cpu)
369 mutex_lock(&clockevents_mutex);
370 ret = clockevents_unbind(ced, cpu);
371 mutex_unlock(&clockevents_mutex);
374 EXPORT_SYMBOL_GPL(clockevents_unbind);
377 * clockevents_register_device - register a clock event device
378 * @dev: device to register
380 void clockevents_register_device(struct clock_event_device *dev)
384 BUG_ON(dev->mode != CLOCK_EVT_MODE_UNUSED);
386 WARN_ON(num_possible_cpus() > 1);
387 dev->cpumask = cpumask_of(smp_processor_id());
390 raw_spin_lock_irqsave(&clockevents_lock, flags);
392 list_add(&dev->list, &clockevent_devices);
393 tick_check_new_device(dev);
394 clockevents_notify_released();
396 raw_spin_unlock_irqrestore(&clockevents_lock, flags);
398 EXPORT_SYMBOL_GPL(clockevents_register_device);
400 void clockevents_config(struct clock_event_device *dev, u32 freq)
404 if (!(dev->features & CLOCK_EVT_FEAT_ONESHOT))
408 * Calculate the maximum number of seconds we can sleep. Limit
409 * to 10 minutes for hardware which can program more than
410 * 32bit ticks so we still get reasonable conversion values.
412 sec = dev->max_delta_ticks;
416 else if (sec > 600 && dev->max_delta_ticks > UINT_MAX)
419 clockevents_calc_mult_shift(dev, freq, sec);
420 dev->min_delta_ns = cev_delta2ns(dev->min_delta_ticks, dev, false);
421 dev->max_delta_ns = cev_delta2ns(dev->max_delta_ticks, dev, true);
425 * clockevents_config_and_register - Configure and register a clock event device
426 * @dev: device to register
427 * @freq: The clock frequency
428 * @min_delta: The minimum clock ticks to program in oneshot mode
429 * @max_delta: The maximum clock ticks to program in oneshot mode
431 * min/max_delta can be 0 for devices which do not support oneshot mode.
433 void clockevents_config_and_register(struct clock_event_device *dev,
434 u32 freq, unsigned long min_delta,
435 unsigned long max_delta)
437 dev->min_delta_ticks = min_delta;
438 dev->max_delta_ticks = max_delta;
439 clockevents_config(dev, freq);
440 clockevents_register_device(dev);
442 EXPORT_SYMBOL_GPL(clockevents_config_and_register);
444 int __clockevents_update_freq(struct clock_event_device *dev, u32 freq)
446 clockevents_config(dev, freq);
448 if (dev->mode == CLOCK_EVT_MODE_ONESHOT)
449 return clockevents_program_event(dev, dev->next_event, false);
451 if (dev->mode == CLOCK_EVT_MODE_PERIODIC)
452 dev->set_mode(CLOCK_EVT_MODE_PERIODIC, dev);
458 * clockevents_update_freq - Update frequency and reprogram a clock event device.
459 * @dev: device to modify
460 * @freq: new device frequency
462 * Reconfigure and reprogram a clock event device in oneshot
463 * mode. Must be called on the cpu for which the device delivers per
464 * cpu timer events. If called for the broadcast device the core takes
465 * care of serialization.
467 * Returns 0 on success, -ETIME when the event is in the past.
469 int clockevents_update_freq(struct clock_event_device *dev, u32 freq)
474 local_irq_save(flags);
475 ret = tick_broadcast_update_freq(dev, freq);
477 ret = __clockevents_update_freq(dev, freq);
478 local_irq_restore(flags);
483 * Noop handler when we shut down an event device
485 void clockevents_handle_noop(struct clock_event_device *dev)
490 * clockevents_exchange_device - release and request clock devices
491 * @old: device to release (can be NULL)
492 * @new: device to request (can be NULL)
494 * Called from the notifier chain. clockevents_lock is held already
496 void clockevents_exchange_device(struct clock_event_device *old,
497 struct clock_event_device *new)
501 local_irq_save(flags);
503 * Caller releases a clock event device. We queue it into the
504 * released list and do a notify add later.
507 module_put(old->owner);
508 clockevents_set_mode(old, CLOCK_EVT_MODE_UNUSED);
509 list_del(&old->list);
510 list_add(&old->list, &clockevents_released);
514 BUG_ON(new->mode != CLOCK_EVT_MODE_UNUSED);
515 clockevents_shutdown(new);
517 local_irq_restore(flags);
521 * clockevents_suspend - suspend clock devices
523 void clockevents_suspend(void)
525 struct clock_event_device *dev;
527 list_for_each_entry_reverse(dev, &clockevent_devices, list)
533 * clockevents_resume - resume clock devices
535 void clockevents_resume(void)
537 struct clock_event_device *dev;
539 list_for_each_entry(dev, &clockevent_devices, list)
544 #ifdef CONFIG_GENERIC_CLOCKEVENTS
546 * clockevents_notify - notification about relevant events
547 * Returns 0 on success, any other value on error
549 int clockevents_notify(unsigned long reason, void *arg)
551 struct clock_event_device *dev, *tmp;
555 raw_spin_lock_irqsave(&clockevents_lock, flags);
558 case CLOCK_EVT_NOTIFY_BROADCAST_ON:
559 case CLOCK_EVT_NOTIFY_BROADCAST_OFF:
560 case CLOCK_EVT_NOTIFY_BROADCAST_FORCE:
561 tick_broadcast_on_off(reason, arg);
564 case CLOCK_EVT_NOTIFY_BROADCAST_ENTER:
565 case CLOCK_EVT_NOTIFY_BROADCAST_EXIT:
566 ret = tick_broadcast_oneshot_control(reason);
569 case CLOCK_EVT_NOTIFY_CPU_DYING:
570 tick_handover_do_timer(arg);
573 case CLOCK_EVT_NOTIFY_SUSPEND:
575 tick_suspend_broadcast();
578 case CLOCK_EVT_NOTIFY_RESUME:
582 case CLOCK_EVT_NOTIFY_CPU_DEAD:
583 tick_shutdown_broadcast_oneshot(arg);
584 tick_shutdown_broadcast(arg);
587 * Unregister the clock event devices which were
588 * released from the users in the notify chain.
590 list_for_each_entry_safe(dev, tmp, &clockevents_released, list)
591 list_del(&dev->list);
593 * Now check whether the CPU has left unused per cpu devices
596 list_for_each_entry_safe(dev, tmp, &clockevent_devices, list) {
597 if (cpumask_test_cpu(cpu, dev->cpumask) &&
598 cpumask_weight(dev->cpumask) == 1 &&
599 !tick_is_broadcast_device(dev)) {
600 BUG_ON(dev->mode != CLOCK_EVT_MODE_UNUSED);
601 list_del(&dev->list);
608 raw_spin_unlock_irqrestore(&clockevents_lock, flags);
611 EXPORT_SYMBOL_GPL(clockevents_notify);
614 struct bus_type clockevents_subsys = {
615 .name = "clockevents",
616 .dev_name = "clockevent",
619 static DEFINE_PER_CPU(struct device, tick_percpu_dev);
620 static struct tick_device *tick_get_tick_dev(struct device *dev);
622 static ssize_t sysfs_show_current_tick_dev(struct device *dev,
623 struct device_attribute *attr,
626 struct tick_device *td;
629 raw_spin_lock_irq(&clockevents_lock);
630 td = tick_get_tick_dev(dev);
631 if (td && td->evtdev)
632 count = snprintf(buf, PAGE_SIZE, "%s\n", td->evtdev->name);
633 raw_spin_unlock_irq(&clockevents_lock);
636 static DEVICE_ATTR(current_device, 0444, sysfs_show_current_tick_dev, NULL);
638 /* We don't support the abomination of removable broadcast devices */
639 static ssize_t sysfs_unbind_tick_dev(struct device *dev,
640 struct device_attribute *attr,
641 const char *buf, size_t count)
643 char name[CS_NAME_LEN];
644 ssize_t ret = sysfs_get_uname(buf, name, count);
645 struct clock_event_device *ce;
651 mutex_lock(&clockevents_mutex);
652 raw_spin_lock_irq(&clockevents_lock);
653 list_for_each_entry(ce, &clockevent_devices, list) {
654 if (!strcmp(ce->name, name)) {
655 ret = __clockevents_try_unbind(ce, dev->id);
659 raw_spin_unlock_irq(&clockevents_lock);
661 * We hold clockevents_mutex, so ce can't go away
664 ret = clockevents_unbind(ce, dev->id);
665 mutex_unlock(&clockevents_mutex);
666 return ret ? ret : count;
668 static DEVICE_ATTR(unbind_device, 0200, NULL, sysfs_unbind_tick_dev);
670 #ifdef CONFIG_GENERIC_CLOCKEVENTS_BROADCAST
671 static struct device tick_bc_dev = {
672 .init_name = "broadcast",
674 .bus = &clockevents_subsys,
677 static struct tick_device *tick_get_tick_dev(struct device *dev)
679 return dev == &tick_bc_dev ? tick_get_broadcast_device() :
680 &per_cpu(tick_cpu_device, dev->id);
683 static __init int tick_broadcast_init_sysfs(void)
685 int err = device_register(&tick_bc_dev);
688 err = device_create_file(&tick_bc_dev, &dev_attr_current_device);
692 static struct tick_device *tick_get_tick_dev(struct device *dev)
694 return &per_cpu(tick_cpu_device, dev->id);
696 static inline int tick_broadcast_init_sysfs(void) { return 0; }
699 static int __init tick_init_sysfs(void)
703 for_each_possible_cpu(cpu) {
704 struct device *dev = &per_cpu(tick_percpu_dev, cpu);
708 dev->bus = &clockevents_subsys;
709 err = device_register(dev);
711 err = device_create_file(dev, &dev_attr_current_device);
713 err = device_create_file(dev, &dev_attr_unbind_device);
717 return tick_broadcast_init_sysfs();
720 static int __init clockevents_init_sysfs(void)
722 int err = subsys_system_register(&clockevents_subsys, NULL);
725 err = tick_init_sysfs();
728 device_initcall(clockevents_init_sysfs);
731 #endif /* GENERIC_CLOCK_EVENTS */