2 * linux/kernel/time/tick-broadcast.c
4 * This file contains functions which emulate a local clock-event
5 * device via a broadcast event source.
7 * Copyright(C) 2005-2006, Thomas Gleixner <tglx@linutronix.de>
8 * Copyright(C) 2005-2007, Red Hat, Inc., Ingo Molnar
9 * Copyright(C) 2006-2007, Timesys Corp., Thomas Gleixner
11 * This code is licenced under the GPL version 2. For details see
12 * kernel-base/COPYING.
14 #include <linux/cpu.h>
15 #include <linux/err.h>
16 #include <linux/hrtimer.h>
17 #include <linux/irq.h>
18 #include <linux/percpu.h>
19 #include <linux/profile.h>
20 #include <linux/sched.h>
21 #include <linux/tick.h>
23 #include "tick-internal.h"
26 * Broadcast support for broken x86 hardware, where the local apic
27 * timer stops in C3 state.
30 struct tick_device tick_broadcast_device;
31 static cpumask_t tick_broadcast_mask;
32 static DEFINE_SPINLOCK(tick_broadcast_lock);
35 * Debugging: see timer_list.c
37 struct tick_device *tick_get_broadcast_device(void)
39 return &tick_broadcast_device;
42 cpumask_t *tick_get_broadcast_mask(void)
44 return &tick_broadcast_mask;
48 * Start the device in periodic mode
50 static void tick_broadcast_start_periodic(struct clock_event_device *bc)
52 if (bc && bc->mode == CLOCK_EVT_MODE_SHUTDOWN)
53 tick_setup_periodic(bc, 1);
57 * Check, if the device can be utilized as broadcast device:
59 int tick_check_broadcast_device(struct clock_event_device *dev)
61 if (tick_broadcast_device.evtdev ||
62 (dev->features & CLOCK_EVT_FEAT_C3STOP))
65 clockevents_exchange_device(NULL, dev);
66 tick_broadcast_device.evtdev = dev;
67 if (!cpus_empty(tick_broadcast_mask))
68 tick_broadcast_start_periodic(dev);
73 * Check, if the device is the broadcast device
75 int tick_is_broadcast_device(struct clock_event_device *dev)
77 return (dev && tick_broadcast_device.evtdev == dev);
81 * Check, if the device is disfunctional and a place holder, which
82 * needs to be handled by the broadcast device.
84 int tick_device_uses_broadcast(struct clock_event_device *dev, int cpu)
89 spin_lock_irqsave(&tick_broadcast_lock, flags);
92 * Devices might be registered with both periodic and oneshot
93 * mode disabled. This signals, that the device needs to be
94 * operated from the broadcast device and is a placeholder for
95 * the cpu local device.
97 if (!tick_device_is_functional(dev)) {
98 dev->event_handler = tick_handle_periodic;
99 cpu_set(cpu, tick_broadcast_mask);
100 tick_broadcast_start_periodic(tick_broadcast_device.evtdev);
104 spin_unlock_irqrestore(&tick_broadcast_lock, flags);
109 * Broadcast the event to the cpus, which are set in the mask
111 int tick_do_broadcast(cpumask_t mask)
113 int ret = 0, cpu = smp_processor_id();
114 struct tick_device *td;
117 * Check, if the current cpu is in the mask
119 if (cpu_isset(cpu, mask)) {
120 cpu_clear(cpu, mask);
121 td = &per_cpu(tick_cpu_device, cpu);
122 td->evtdev->event_handler(td->evtdev);
126 if (!cpus_empty(mask)) {
128 * It might be necessary to actually check whether the devices
129 * have different broadcast functions. For now, just use the
130 * one of the first device. This works as long as we have this
131 * misfeature only on x86 (lapic)
133 cpu = first_cpu(mask);
134 td = &per_cpu(tick_cpu_device, cpu);
135 td->evtdev->broadcast(mask);
142 * Periodic broadcast:
143 * - invoke the broadcast handlers
145 static void tick_do_periodic_broadcast(void)
149 spin_lock(&tick_broadcast_lock);
151 cpus_and(mask, cpu_online_map, tick_broadcast_mask);
152 tick_do_broadcast(mask);
154 spin_unlock(&tick_broadcast_lock);
158 * Event handler for periodic broadcast ticks
160 static void tick_handle_periodic_broadcast(struct clock_event_device *dev)
162 dev->next_event.tv64 = KTIME_MAX;
164 tick_do_periodic_broadcast();
167 * The device is in periodic mode. No reprogramming necessary:
169 if (dev->mode == CLOCK_EVT_MODE_PERIODIC)
173 * Setup the next period for devices, which do not have
177 ktime_t next = ktime_add(dev->next_event, tick_period);
179 if (!clockevents_program_event(dev, next, ktime_get()))
181 tick_do_periodic_broadcast();
186 * Powerstate information: The system enters/leaves a state, where
187 * affected devices might stop
189 static void tick_do_broadcast_on_off(void *why)
191 struct clock_event_device *bc, *dev;
192 struct tick_device *td;
193 unsigned long flags, *reason = why;
196 spin_lock_irqsave(&tick_broadcast_lock, flags);
198 cpu = smp_processor_id();
199 td = &per_cpu(tick_cpu_device, cpu);
201 bc = tick_broadcast_device.evtdev;
204 * Is the device in broadcast mode forever or is it not
205 * affected by the powerstate ?
207 if (!dev || !tick_device_is_functional(dev) ||
208 !(dev->features & CLOCK_EVT_FEAT_C3STOP))
211 if (*reason == CLOCK_EVT_NOTIFY_BROADCAST_ON) {
212 if (!cpu_isset(cpu, tick_broadcast_mask)) {
213 cpu_set(cpu, tick_broadcast_mask);
214 if (td->mode == TICKDEV_MODE_PERIODIC)
215 clockevents_set_mode(dev,
216 CLOCK_EVT_MODE_SHUTDOWN);
219 if (cpu_isset(cpu, tick_broadcast_mask)) {
220 cpu_clear(cpu, tick_broadcast_mask);
221 if (td->mode == TICKDEV_MODE_PERIODIC)
222 tick_setup_periodic(dev, 0);
226 if (cpus_empty(tick_broadcast_mask))
227 clockevents_set_mode(bc, CLOCK_EVT_MODE_SHUTDOWN);
229 if (tick_broadcast_device.mode == TICKDEV_MODE_PERIODIC)
230 tick_broadcast_start_periodic(bc);
232 tick_broadcast_setup_oneshot(bc);
235 spin_unlock_irqrestore(&tick_broadcast_lock, flags);
239 * Powerstate information: The system enters/leaves a state, where
240 * affected devices might stop.
242 void tick_broadcast_on_off(unsigned long reason, int *oncpu)
247 tick_do_broadcast_on_off(&reason);
249 smp_call_function_single(*oncpu, tick_do_broadcast_on_off,
255 * Set the periodic handler depending on broadcast on/off
257 void tick_set_periodic_handler(struct clock_event_device *dev, int broadcast)
260 dev->event_handler = tick_handle_periodic;
262 dev->event_handler = tick_handle_periodic_broadcast;
266 * Remove a CPU from broadcasting
268 void tick_shutdown_broadcast(unsigned int *cpup)
270 struct clock_event_device *bc;
272 unsigned int cpu = *cpup;
274 spin_lock_irqsave(&tick_broadcast_lock, flags);
276 bc = tick_broadcast_device.evtdev;
277 cpu_clear(cpu, tick_broadcast_mask);
279 if (tick_broadcast_device.mode == TICKDEV_MODE_PERIODIC) {
280 if (bc && cpus_empty(tick_broadcast_mask))
281 clockevents_set_mode(bc, CLOCK_EVT_MODE_SHUTDOWN);
284 spin_unlock_irqrestore(&tick_broadcast_lock, flags);
287 #ifdef CONFIG_TICK_ONESHOT
289 static cpumask_t tick_broadcast_oneshot_mask;
292 * Debugging: see timer_list.c
294 cpumask_t *tick_get_broadcast_oneshot_mask(void)
296 return &tick_broadcast_oneshot_mask;
299 static int tick_broadcast_set_event(ktime_t expires, int force)
301 struct clock_event_device *bc = tick_broadcast_device.evtdev;
302 ktime_t now = ktime_get();
306 res = clockevents_program_event(bc, expires, now);
310 expires = ktime_add(now, ktime_set(0, bc->min_delta_ns));
315 * Reprogram the broadcast device:
317 * Called with tick_broadcast_lock held and interrupts disabled.
319 static int tick_broadcast_reprogram(void)
321 ktime_t expires = { .tv64 = KTIME_MAX };
322 struct tick_device *td;
326 * Find the event which expires next:
328 for (cpu = first_cpu(tick_broadcast_oneshot_mask); cpu != NR_CPUS;
329 cpu = next_cpu(cpu, tick_broadcast_oneshot_mask)) {
330 td = &per_cpu(tick_cpu_device, cpu);
331 if (td->evtdev->next_event.tv64 < expires.tv64)
332 expires = td->evtdev->next_event;
335 if (expires.tv64 == KTIME_MAX)
338 return tick_broadcast_set_event(expires, 0);
342 * Handle oneshot mode broadcasting
344 static void tick_handle_oneshot_broadcast(struct clock_event_device *dev)
346 struct tick_device *td;
351 spin_lock(&tick_broadcast_lock);
353 dev->next_event.tv64 = KTIME_MAX;
354 mask = CPU_MASK_NONE;
356 /* Find all expired events */
357 for (cpu = first_cpu(tick_broadcast_oneshot_mask); cpu != NR_CPUS;
358 cpu = next_cpu(cpu, tick_broadcast_oneshot_mask)) {
359 td = &per_cpu(tick_cpu_device, cpu);
360 if (td->evtdev->next_event.tv64 <= now.tv64)
365 * Wakeup the cpus which have an expired event. The broadcast
366 * device is reprogrammed in the return from idle code.
368 if (!tick_do_broadcast(mask)) {
370 * The global event did not expire any CPU local
371 * events. This happens in dyntick mode, as the
372 * maximum PIT delta is quite small.
374 if (tick_broadcast_reprogram())
377 spin_unlock(&tick_broadcast_lock);
381 * Powerstate information: The system enters/leaves a state, where
382 * affected devices might stop
384 void tick_broadcast_oneshot_control(unsigned long reason)
386 struct clock_event_device *bc, *dev;
387 struct tick_device *td;
391 spin_lock_irqsave(&tick_broadcast_lock, flags);
394 * Periodic mode does not care about the enter/exit of power
397 if (tick_broadcast_device.mode == TICKDEV_MODE_PERIODIC)
400 bc = tick_broadcast_device.evtdev;
401 cpu = smp_processor_id();
402 td = &per_cpu(tick_cpu_device, cpu);
405 if (!(dev->features & CLOCK_EVT_FEAT_C3STOP))
408 if (reason == CLOCK_EVT_NOTIFY_BROADCAST_ENTER) {
409 if (!cpu_isset(cpu, tick_broadcast_oneshot_mask)) {
410 cpu_set(cpu, tick_broadcast_oneshot_mask);
411 clockevents_set_mode(dev, CLOCK_EVT_MODE_SHUTDOWN);
412 if (dev->next_event.tv64 < bc->next_event.tv64)
413 tick_broadcast_set_event(dev->next_event, 1);
416 if (cpu_isset(cpu, tick_broadcast_oneshot_mask)) {
417 cpu_clear(cpu, tick_broadcast_oneshot_mask);
418 clockevents_set_mode(dev, CLOCK_EVT_MODE_ONESHOT);
419 if (dev->next_event.tv64 != KTIME_MAX)
420 tick_program_event(dev->next_event, 1);
425 spin_unlock_irqrestore(&tick_broadcast_lock, flags);
429 * tick_broadcast_setup_highres - setup the broadcast device for highres
431 void tick_broadcast_setup_oneshot(struct clock_event_device *bc)
433 if (bc->mode != CLOCK_EVT_MODE_ONESHOT) {
434 bc->event_handler = tick_handle_oneshot_broadcast;
435 clockevents_set_mode(bc, CLOCK_EVT_MODE_ONESHOT);
436 bc->next_event.tv64 = KTIME_MAX;
441 * Select oneshot operating mode for the broadcast device
443 void tick_broadcast_switch_to_oneshot(void)
445 struct clock_event_device *bc;
448 spin_lock_irqsave(&tick_broadcast_lock, flags);
450 tick_broadcast_device.mode = TICKDEV_MODE_ONESHOT;
451 bc = tick_broadcast_device.evtdev;
453 tick_broadcast_setup_oneshot(bc);
454 spin_unlock_irqrestore(&tick_broadcast_lock, flags);
459 * Remove a dead CPU from broadcasting
461 void tick_shutdown_broadcast_oneshot(unsigned int *cpup)
463 struct clock_event_device *bc;
465 unsigned int cpu = *cpup;
467 spin_lock_irqsave(&tick_broadcast_lock, flags);
469 bc = tick_broadcast_device.evtdev;
470 cpu_clear(cpu, tick_broadcast_oneshot_mask);
472 if (tick_broadcast_device.mode == TICKDEV_MODE_ONESHOT) {
473 if (bc && cpus_empty(tick_broadcast_oneshot_mask))
474 clockevents_set_mode(bc, CLOCK_EVT_MODE_SHUTDOWN);
477 spin_unlock_irqrestore(&tick_broadcast_lock, flags);