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 /* The registered clock event devices */
23 static LIST_HEAD(clockevent_devices);
24 static LIST_HEAD(clockevents_released);
26 /* Notification for clock events */
27 static RAW_NOTIFIER_HEAD(clockevents_chain);
29 /* Protection for the above */
30 static DEFINE_SPINLOCK(clockevents_lock);
33 * clockevents_delta2ns - Convert a latch value (device ticks) to nanoseconds
34 * @latch: value to convert
35 * @evt: pointer to clock event device descriptor
37 * Math helper, returns latch value converted to nanoseconds (bound checked)
39 unsigned long clockevent_delta2ns(unsigned long latch,
40 struct clock_event_device *evt)
42 u64 clc = ((u64) latch << evt->shift);
44 if (unlikely(!evt->mult)) {
49 do_div(clc, evt->mult);
55 return (unsigned long) clc;
59 * clockevents_set_mode - set the operating mode of a clock event device
60 * @dev: device to modify
63 * Must be called with interrupts disabled !
65 void clockevents_set_mode(struct clock_event_device *dev,
66 enum clock_event_mode mode)
68 if (dev->mode != mode) {
69 dev->set_mode(mode, dev);
75 * clockevents_shutdown - shutdown the device and clear next_event
76 * @dev: device to shutdown
78 void clockevents_shutdown(struct clock_event_device *dev)
80 clockevents_set_mode(dev, CLOCK_EVT_MODE_SHUTDOWN);
81 dev->next_event.tv64 = KTIME_MAX;
85 * clockevents_program_event - Reprogram the clock event device.
86 * @expires: absolute expiry time (monotonic clock)
88 * Returns 0 on success, -ETIME when the event is in the past.
90 int clockevents_program_event(struct clock_event_device *dev, ktime_t expires,
93 unsigned long long clc;
96 if (unlikely(expires.tv64 < 0)) {
101 delta = ktime_to_ns(ktime_sub(expires, now));
106 dev->next_event = expires;
108 if (dev->mode == CLOCK_EVT_MODE_SHUTDOWN)
111 if (delta > dev->max_delta_ns)
112 delta = dev->max_delta_ns;
113 if (delta < dev->min_delta_ns)
114 delta = dev->min_delta_ns;
116 clc = delta * dev->mult;
119 return dev->set_next_event((unsigned long) clc, dev);
123 * clockevents_register_notifier - register a clock events change listener
125 int clockevents_register_notifier(struct notifier_block *nb)
129 spin_lock(&clockevents_lock);
130 ret = raw_notifier_chain_register(&clockevents_chain, nb);
131 spin_unlock(&clockevents_lock);
137 * Notify about a clock event change. Called with clockevents_lock
140 static void clockevents_do_notify(unsigned long reason, void *dev)
142 raw_notifier_call_chain(&clockevents_chain, reason, dev);
146 * Called after a notify add to make devices available which were
147 * released from the notifier call.
149 static void clockevents_notify_released(void)
151 struct clock_event_device *dev;
153 while (!list_empty(&clockevents_released)) {
154 dev = list_entry(clockevents_released.next,
155 struct clock_event_device, list);
156 list_del(&dev->list);
157 list_add(&dev->list, &clockevent_devices);
158 clockevents_do_notify(CLOCK_EVT_NOTIFY_ADD, dev);
163 * clockevents_register_device - register a clock event device
164 * @dev: device to register
166 void clockevents_register_device(struct clock_event_device *dev)
168 BUG_ON(dev->mode != CLOCK_EVT_MODE_UNUSED);
169 BUG_ON(!dev->cpumask);
172 * A nsec2cyc multiplicator of 0 is invalid and we'd crash
173 * on it, so fix it up and emit a warning:
175 if (unlikely(!dev->mult)) {
180 spin_lock(&clockevents_lock);
182 list_add(&dev->list, &clockevent_devices);
183 clockevents_do_notify(CLOCK_EVT_NOTIFY_ADD, dev);
184 clockevents_notify_released();
186 spin_unlock(&clockevents_lock);
190 * Noop handler when we shut down an event device
192 void clockevents_handle_noop(struct clock_event_device *dev)
197 * clockevents_exchange_device - release and request clock devices
198 * @old: device to release (can be NULL)
199 * @new: device to request (can be NULL)
201 * Called from the notifier chain. clockevents_lock is held already
203 void clockevents_exchange_device(struct clock_event_device *old,
204 struct clock_event_device *new)
208 local_irq_save(flags);
210 * Caller releases a clock event device. We queue it into the
211 * released list and do a notify add later.
214 clockevents_set_mode(old, CLOCK_EVT_MODE_UNUSED);
215 list_del(&old->list);
216 list_add(&old->list, &clockevents_released);
220 BUG_ON(new->mode != CLOCK_EVT_MODE_UNUSED);
221 clockevents_shutdown(new);
223 local_irq_restore(flags);
226 #ifdef CONFIG_GENERIC_CLOCKEVENTS
228 * clockevents_notify - notification about relevant events
230 void clockevents_notify(unsigned long reason, void *arg)
232 struct list_head *node, *tmp;
234 spin_lock(&clockevents_lock);
235 clockevents_do_notify(reason, arg);
238 case CLOCK_EVT_NOTIFY_CPU_DEAD:
240 * Unregister the clock event devices which were
241 * released from the users in the notify chain.
243 list_for_each_safe(node, tmp, &clockevents_released)
249 spin_unlock(&clockevents_lock);
251 EXPORT_SYMBOL_GPL(clockevents_notify);