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/notifier.h>
19 #include <linux/smp.h>
20 #include <linux/sysdev.h>
22 #include "tick-internal.h"
24 /* The registered clock event devices */
25 static LIST_HEAD(clockevent_devices);
26 static LIST_HEAD(clockevents_released);
28 /* Notification for clock events */
29 static RAW_NOTIFIER_HEAD(clockevents_chain);
31 /* Protection for the above */
32 static DEFINE_RAW_SPINLOCK(clockevents_lock);
35 * clockevents_delta2ns - Convert a latch value (device ticks) to nanoseconds
36 * @latch: value to convert
37 * @evt: pointer to clock event device descriptor
39 * Math helper, returns latch value converted to nanoseconds (bound checked)
41 u64 clockevent_delta2ns(unsigned long latch, struct clock_event_device *evt)
43 u64 clc = (u64) latch << evt->shift;
45 if (unlikely(!evt->mult)) {
50 do_div(clc, evt->mult);
58 EXPORT_SYMBOL_GPL(clockevent_delta2ns);
61 * clockevents_set_mode - set the operating mode of a clock event device
62 * @dev: device to modify
65 * Must be called with interrupts disabled !
67 void clockevents_set_mode(struct clock_event_device *dev,
68 enum clock_event_mode mode)
70 if (dev->mode != mode) {
71 dev->set_mode(mode, dev);
75 * A nsec2cyc multiplicator of 0 is invalid and we'd crash
76 * on it, so fix it up and emit a warning:
78 if (mode == CLOCK_EVT_MODE_ONESHOT) {
79 if (unlikely(!dev->mult)) {
88 * clockevents_shutdown - shutdown the device and clear next_event
89 * @dev: device to shutdown
91 void clockevents_shutdown(struct clock_event_device *dev)
93 clockevents_set_mode(dev, CLOCK_EVT_MODE_SHUTDOWN);
94 dev->next_event.tv64 = KTIME_MAX;
98 * clockevents_program_event - Reprogram the clock event device.
99 * @expires: absolute expiry time (monotonic clock)
101 * Returns 0 on success, -ETIME when the event is in the past.
103 int clockevents_program_event(struct clock_event_device *dev, ktime_t expires,
106 unsigned long long clc;
109 if (unlikely(expires.tv64 < 0)) {
114 delta = ktime_to_ns(ktime_sub(expires, now));
119 dev->next_event = expires;
121 if (dev->mode == CLOCK_EVT_MODE_SHUTDOWN)
124 if (delta > dev->max_delta_ns)
125 delta = dev->max_delta_ns;
126 if (delta < dev->min_delta_ns)
127 delta = dev->min_delta_ns;
129 clc = delta * dev->mult;
132 return dev->set_next_event((unsigned long) clc, dev);
136 * clockevents_register_notifier - register a clock events change listener
138 int clockevents_register_notifier(struct notifier_block *nb)
143 raw_spin_lock_irqsave(&clockevents_lock, flags);
144 ret = raw_notifier_chain_register(&clockevents_chain, nb);
145 raw_spin_unlock_irqrestore(&clockevents_lock, flags);
151 * Notify about a clock event change. Called with clockevents_lock
154 static void clockevents_do_notify(unsigned long reason, void *dev)
156 raw_notifier_call_chain(&clockevents_chain, reason, dev);
160 * Called after a notify add to make devices available which were
161 * released from the notifier call.
163 static void clockevents_notify_released(void)
165 struct clock_event_device *dev;
167 while (!list_empty(&clockevents_released)) {
168 dev = list_entry(clockevents_released.next,
169 struct clock_event_device, list);
170 list_del(&dev->list);
171 list_add(&dev->list, &clockevent_devices);
172 clockevents_do_notify(CLOCK_EVT_NOTIFY_ADD, dev);
177 * clockevents_register_device - register a clock event device
178 * @dev: device to register
180 void clockevents_register_device(struct clock_event_device *dev)
184 BUG_ON(dev->mode != CLOCK_EVT_MODE_UNUSED);
186 WARN_ON(num_possible_cpus() > 1);
187 dev->cpumask = cpumask_of(smp_processor_id());
190 raw_spin_lock_irqsave(&clockevents_lock, flags);
192 list_add(&dev->list, &clockevent_devices);
193 clockevents_do_notify(CLOCK_EVT_NOTIFY_ADD, dev);
194 clockevents_notify_released();
196 raw_spin_unlock_irqrestore(&clockevents_lock, flags);
198 EXPORT_SYMBOL_GPL(clockevents_register_device);
200 static void clockevents_config(struct clock_event_device *dev,
205 if (!(dev->features & CLOCK_EVT_FEAT_ONESHOT))
209 * Calculate the maximum number of seconds we can sleep. Limit
210 * to 10 minutes for hardware which can program more than
211 * 32bit ticks so we still get reasonable conversion values.
213 sec = dev->max_delta_ticks;
217 else if (sec > 600 && dev->max_delta_ticks > UINT_MAX)
220 clockevents_calc_mult_shift(dev, freq, sec);
221 dev->min_delta_ns = clockevent_delta2ns(dev->min_delta_ticks, dev);
222 dev->max_delta_ns = clockevent_delta2ns(dev->max_delta_ticks, dev);
226 * clockevents_config_and_register - Configure and register a clock event device
227 * @dev: device to register
228 * @freq: The clock frequency
229 * @min_delta: The minimum clock ticks to program in oneshot mode
230 * @max_delta: The maximum clock ticks to program in oneshot mode
232 * min/max_delta can be 0 for devices which do not support oneshot mode.
234 void clockevents_config_and_register(struct clock_event_device *dev,
235 u32 freq, unsigned long min_delta,
236 unsigned long max_delta)
238 dev->min_delta_ticks = min_delta;
239 dev->max_delta_ticks = max_delta;
240 clockevents_config(dev, freq);
241 clockevents_register_device(dev);
245 * clockevents_update_freq - Update frequency and reprogram a clock event device.
246 * @dev: device to modify
247 * @freq: new device frequency
249 * Reconfigure and reprogram a clock event device in oneshot
250 * mode. Must be called on the cpu for which the device delivers per
251 * cpu timer events with interrupts disabled! Returns 0 on success,
252 * -ETIME when the event is in the past.
254 int clockevents_update_freq(struct clock_event_device *dev, u32 freq)
256 clockevents_config(dev, freq);
258 if (dev->mode != CLOCK_EVT_MODE_ONESHOT)
261 return clockevents_program_event(dev, dev->next_event, ktime_get());
265 * Noop handler when we shut down an event device
267 void clockevents_handle_noop(struct clock_event_device *dev)
272 * clockevents_exchange_device - release and request clock devices
273 * @old: device to release (can be NULL)
274 * @new: device to request (can be NULL)
276 * Called from the notifier chain. clockevents_lock is held already
278 void clockevents_exchange_device(struct clock_event_device *old,
279 struct clock_event_device *new)
283 local_irq_save(flags);
285 * Caller releases a clock event device. We queue it into the
286 * released list and do a notify add later.
289 clockevents_set_mode(old, CLOCK_EVT_MODE_UNUSED);
290 list_del(&old->list);
291 list_add(&old->list, &clockevents_released);
295 BUG_ON(new->mode != CLOCK_EVT_MODE_UNUSED);
296 clockevents_shutdown(new);
298 local_irq_restore(flags);
301 #ifdef CONFIG_GENERIC_CLOCKEVENTS
303 * clockevents_notify - notification about relevant events
305 void clockevents_notify(unsigned long reason, void *arg)
307 struct clock_event_device *dev, *tmp;
311 raw_spin_lock_irqsave(&clockevents_lock, flags);
312 clockevents_do_notify(reason, arg);
315 case CLOCK_EVT_NOTIFY_CPU_DEAD:
317 * Unregister the clock event devices which were
318 * released from the users in the notify chain.
320 list_for_each_entry_safe(dev, tmp, &clockevents_released, list)
321 list_del(&dev->list);
323 * Now check whether the CPU has left unused per cpu devices
326 list_for_each_entry_safe(dev, tmp, &clockevent_devices, list) {
327 if (cpumask_test_cpu(cpu, dev->cpumask) &&
328 cpumask_weight(dev->cpumask) == 1 &&
329 !tick_is_broadcast_device(dev)) {
330 BUG_ON(dev->mode != CLOCK_EVT_MODE_UNUSED);
331 list_del(&dev->list);
338 raw_spin_unlock_irqrestore(&clockevents_lock, flags);
340 EXPORT_SYMBOL_GPL(clockevents_notify);