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>
20 #include "tick-internal.h"
22 /* The registered clock event devices */
23 static LIST_HEAD(clockevent_devices);
24 static LIST_HEAD(clockevents_released);
25 /* Protection for the above */
26 static DEFINE_RAW_SPINLOCK(clockevents_lock);
29 * clockevents_delta2ns - Convert a latch value (device ticks) to nanoseconds
30 * @latch: value to convert
31 * @evt: pointer to clock event device descriptor
33 * Math helper, returns latch value converted to nanoseconds (bound checked)
35 u64 clockevent_delta2ns(unsigned long latch, struct clock_event_device *evt)
37 u64 clc = (u64) latch << evt->shift;
39 if (unlikely(!evt->mult)) {
44 do_div(clc, evt->mult);
52 EXPORT_SYMBOL_GPL(clockevent_delta2ns);
55 * clockevents_set_mode - set the operating mode of a clock event device
56 * @dev: device to modify
59 * Must be called with interrupts disabled !
61 void clockevents_set_mode(struct clock_event_device *dev,
62 enum clock_event_mode mode)
64 if (dev->mode != mode) {
65 dev->set_mode(mode, dev);
69 * A nsec2cyc multiplicator of 0 is invalid and we'd crash
70 * on it, so fix it up and emit a warning:
72 if (mode == CLOCK_EVT_MODE_ONESHOT) {
73 if (unlikely(!dev->mult)) {
82 * clockevents_shutdown - shutdown the device and clear next_event
83 * @dev: device to shutdown
85 void clockevents_shutdown(struct clock_event_device *dev)
87 clockevents_set_mode(dev, CLOCK_EVT_MODE_SHUTDOWN);
88 dev->next_event.tv64 = KTIME_MAX;
91 #ifdef CONFIG_GENERIC_CLOCKEVENTS_MIN_ADJUST
93 /* Limit min_delta to a jiffie */
94 #define MIN_DELTA_LIMIT (NSEC_PER_SEC / HZ)
97 * clockevents_increase_min_delta - raise minimum delta of a clock event device
98 * @dev: device to increase the minimum delta
100 * Returns 0 on success, -ETIME when the minimum delta reached the limit.
102 static int clockevents_increase_min_delta(struct clock_event_device *dev)
104 /* Nothing to do if we already reached the limit */
105 if (dev->min_delta_ns >= MIN_DELTA_LIMIT) {
106 printk(KERN_WARNING "CE: Reprogramming failure. Giving up\n");
107 dev->next_event.tv64 = KTIME_MAX;
111 if (dev->min_delta_ns < 5000)
112 dev->min_delta_ns = 5000;
114 dev->min_delta_ns += dev->min_delta_ns >> 1;
116 if (dev->min_delta_ns > MIN_DELTA_LIMIT)
117 dev->min_delta_ns = MIN_DELTA_LIMIT;
119 printk(KERN_WARNING "CE: %s increased min_delta_ns to %llu nsec\n",
120 dev->name ? dev->name : "?",
121 (unsigned long long) dev->min_delta_ns);
126 * clockevents_program_min_delta - Set clock event device to the minimum delay.
127 * @dev: device to program
129 * Returns 0 on success, -ETIME when the retry loop failed.
131 static int clockevents_program_min_delta(struct clock_event_device *dev)
133 unsigned long long clc;
138 delta = dev->min_delta_ns;
139 dev->next_event = ktime_add_ns(ktime_get(), delta);
141 if (dev->mode == CLOCK_EVT_MODE_SHUTDOWN)
145 clc = ((unsigned long long) delta * dev->mult) >> dev->shift;
146 if (dev->set_next_event((unsigned long) clc, dev) == 0)
151 * We tried 3 times to program the device with the
152 * given min_delta_ns. Try to increase the minimum
153 * delta, if that fails as well get out of here.
155 if (clockevents_increase_min_delta(dev))
162 #else /* CONFIG_GENERIC_CLOCKEVENTS_MIN_ADJUST */
165 * clockevents_program_min_delta - Set clock event device to the minimum delay.
166 * @dev: device to program
168 * Returns 0 on success, -ETIME when the retry loop failed.
170 static int clockevents_program_min_delta(struct clock_event_device *dev)
172 unsigned long long clc;
175 delta = dev->min_delta_ns;
176 dev->next_event = ktime_add_ns(ktime_get(), delta);
178 if (dev->mode == CLOCK_EVT_MODE_SHUTDOWN)
182 clc = ((unsigned long long) delta * dev->mult) >> dev->shift;
183 return dev->set_next_event((unsigned long) clc, dev);
186 #endif /* CONFIG_GENERIC_CLOCKEVENTS_MIN_ADJUST */
189 * clockevents_program_event - Reprogram the clock event device.
190 * @dev: device to program
191 * @expires: absolute expiry time (monotonic clock)
192 * @force: program minimum delay if expires can not be set
194 * Returns 0 on success, -ETIME when the event is in the past.
196 int clockevents_program_event(struct clock_event_device *dev, ktime_t expires,
199 unsigned long long clc;
203 if (unlikely(expires.tv64 < 0)) {
208 dev->next_event = expires;
210 if (dev->mode == CLOCK_EVT_MODE_SHUTDOWN)
213 /* Shortcut for clockevent devices that can deal with ktime. */
214 if (dev->features & CLOCK_EVT_FEAT_KTIME)
215 return dev->set_next_ktime(expires, dev);
217 delta = ktime_to_ns(ktime_sub(expires, ktime_get()));
219 return force ? clockevents_program_min_delta(dev) : -ETIME;
221 delta = min(delta, (int64_t) dev->max_delta_ns);
222 delta = max(delta, (int64_t) dev->min_delta_ns);
224 clc = ((unsigned long long) delta * dev->mult) >> dev->shift;
225 rc = dev->set_next_event((unsigned long) clc, dev);
227 return (rc && force) ? clockevents_program_min_delta(dev) : rc;
231 * Called after a notify add to make devices available which were
232 * released from the notifier call.
234 static void clockevents_notify_released(void)
236 struct clock_event_device *dev;
238 while (!list_empty(&clockevents_released)) {
239 dev = list_entry(clockevents_released.next,
240 struct clock_event_device, list);
241 list_del(&dev->list);
242 list_add(&dev->list, &clockevent_devices);
243 tick_check_new_device(dev);
248 * clockevents_register_device - register a clock event device
249 * @dev: device to register
251 void clockevents_register_device(struct clock_event_device *dev)
255 BUG_ON(dev->mode != CLOCK_EVT_MODE_UNUSED);
257 WARN_ON(num_possible_cpus() > 1);
258 dev->cpumask = cpumask_of(smp_processor_id());
261 raw_spin_lock_irqsave(&clockevents_lock, flags);
263 list_add(&dev->list, &clockevent_devices);
264 tick_check_new_device(dev);
265 clockevents_notify_released();
267 raw_spin_unlock_irqrestore(&clockevents_lock, flags);
269 EXPORT_SYMBOL_GPL(clockevents_register_device);
271 void clockevents_config(struct clock_event_device *dev, u32 freq)
275 if (!(dev->features & CLOCK_EVT_FEAT_ONESHOT))
279 * Calculate the maximum number of seconds we can sleep. Limit
280 * to 10 minutes for hardware which can program more than
281 * 32bit ticks so we still get reasonable conversion values.
283 sec = dev->max_delta_ticks;
287 else if (sec > 600 && dev->max_delta_ticks > UINT_MAX)
290 clockevents_calc_mult_shift(dev, freq, sec);
291 dev->min_delta_ns = clockevent_delta2ns(dev->min_delta_ticks, dev);
292 dev->max_delta_ns = clockevent_delta2ns(dev->max_delta_ticks, dev);
296 * clockevents_config_and_register - Configure and register a clock event device
297 * @dev: device to register
298 * @freq: The clock frequency
299 * @min_delta: The minimum clock ticks to program in oneshot mode
300 * @max_delta: The maximum clock ticks to program in oneshot mode
302 * min/max_delta can be 0 for devices which do not support oneshot mode.
304 void clockevents_config_and_register(struct clock_event_device *dev,
305 u32 freq, unsigned long min_delta,
306 unsigned long max_delta)
308 dev->min_delta_ticks = min_delta;
309 dev->max_delta_ticks = max_delta;
310 clockevents_config(dev, freq);
311 clockevents_register_device(dev);
313 EXPORT_SYMBOL_GPL(clockevents_config_and_register);
316 * clockevents_update_freq - Update frequency and reprogram a clock event device.
317 * @dev: device to modify
318 * @freq: new device frequency
320 * Reconfigure and reprogram a clock event device in oneshot
321 * mode. Must be called on the cpu for which the device delivers per
322 * cpu timer events with interrupts disabled! Returns 0 on success,
323 * -ETIME when the event is in the past.
325 int clockevents_update_freq(struct clock_event_device *dev, u32 freq)
327 clockevents_config(dev, freq);
329 if (dev->mode != CLOCK_EVT_MODE_ONESHOT)
332 return clockevents_program_event(dev, dev->next_event, false);
336 * Noop handler when we shut down an event device
338 void clockevents_handle_noop(struct clock_event_device *dev)
343 * clockevents_exchange_device - release and request clock devices
344 * @old: device to release (can be NULL)
345 * @new: device to request (can be NULL)
347 * Called from the notifier chain. clockevents_lock is held already
349 void clockevents_exchange_device(struct clock_event_device *old,
350 struct clock_event_device *new)
354 local_irq_save(flags);
356 * Caller releases a clock event device. We queue it into the
357 * released list and do a notify add later.
360 clockevents_set_mode(old, CLOCK_EVT_MODE_UNUSED);
361 list_del(&old->list);
362 list_add(&old->list, &clockevents_released);
366 BUG_ON(new->mode != CLOCK_EVT_MODE_UNUSED);
367 clockevents_shutdown(new);
369 local_irq_restore(flags);
373 * clockevents_suspend - suspend clock devices
375 void clockevents_suspend(void)
377 struct clock_event_device *dev;
379 list_for_each_entry_reverse(dev, &clockevent_devices, list)
385 * clockevents_resume - resume clock devices
387 void clockevents_resume(void)
389 struct clock_event_device *dev;
391 list_for_each_entry(dev, &clockevent_devices, list)
396 #ifdef CONFIG_GENERIC_CLOCKEVENTS
398 * clockevents_notify - notification about relevant events
399 * Returns 0 on success, any other value on error
401 int clockevents_notify(unsigned long reason, void *arg)
403 struct clock_event_device *dev, *tmp;
407 raw_spin_lock_irqsave(&clockevents_lock, flags);
410 case CLOCK_EVT_NOTIFY_BROADCAST_ON:
411 case CLOCK_EVT_NOTIFY_BROADCAST_OFF:
412 case CLOCK_EVT_NOTIFY_BROADCAST_FORCE:
413 tick_broadcast_on_off(reason, arg);
416 case CLOCK_EVT_NOTIFY_BROADCAST_ENTER:
417 case CLOCK_EVT_NOTIFY_BROADCAST_EXIT:
418 ret = tick_broadcast_oneshot_control(reason);
421 case CLOCK_EVT_NOTIFY_CPU_DYING:
422 tick_handover_do_timer(arg);
425 case CLOCK_EVT_NOTIFY_SUSPEND:
427 tick_suspend_broadcast();
430 case CLOCK_EVT_NOTIFY_RESUME:
434 case CLOCK_EVT_NOTIFY_CPU_DEAD:
435 tick_shutdown_broadcast_oneshot(arg);
436 tick_shutdown_broadcast(arg);
439 * Unregister the clock event devices which were
440 * released from the users in the notify chain.
442 list_for_each_entry_safe(dev, tmp, &clockevents_released, list)
443 list_del(&dev->list);
445 * Now check whether the CPU has left unused per cpu devices
448 list_for_each_entry_safe(dev, tmp, &clockevent_devices, list) {
449 if (cpumask_test_cpu(cpu, dev->cpumask) &&
450 cpumask_weight(dev->cpumask) == 1 &&
451 !tick_is_broadcast_device(dev)) {
452 BUG_ON(dev->mode != CLOCK_EVT_MODE_UNUSED);
453 list_del(&dev->list);
460 raw_spin_unlock_irqrestore(&clockevents_lock, flags);
463 EXPORT_SYMBOL_GPL(clockevents_notify);