1 /*
2 * linux/kernel/time/tick-common.c
3 *
4 * This file contains the base functions to manage periodic tick
5 * related events.
6 *
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
10 *
11 * This code is licenced under the GPL version 2. For details see
12 * kernel-base/COPYING.
13 */
14 #include <linux/cpu.h>
15 #include <linux/err.h>
16 #include <linux/hrtimer.h>
17 #include <linux/interrupt.h>
18 #include <linux/percpu.h>
19 #include <linux/profile.h>
20 #include <linux/sched.h>
21
22 #include <asm/irq_regs.h>
23
24 #include "tick-internal.h"
25
26 /*
27 * Tick devices
28 */
29 DEFINE_PER_CPU(struct tick_device, tick_cpu_device);
30 /*
31 * Tick next event: keeps track of the tick time
32 */
33 ktime_t tick_next_period;
34 ktime_t tick_period;
35 int tick_do_timer_cpu __read_mostly = TICK_DO_TIMER_BOOT;
36 static DEFINE_RAW_SPINLOCK(tick_device_lock);
37
38 /*
39 * Debugging: see timer_list.c
40 */
tick_get_device(int cpu)41 struct tick_device *tick_get_device(int cpu)
42 {
43 return &per_cpu(tick_cpu_device, cpu);
44 }
45
46 /**
47 * tick_is_oneshot_available - check for a oneshot capable event device
48 */
tick_is_oneshot_available(void)49 int tick_is_oneshot_available(void)
50 {
51 struct clock_event_device *dev = __this_cpu_read(tick_cpu_device.evtdev);
52
53 if (!dev || !(dev->features & CLOCK_EVT_FEAT_ONESHOT))
54 return 0;
55 if (!(dev->features & CLOCK_EVT_FEAT_C3STOP))
56 return 1;
57 return tick_broadcast_oneshot_available();
58 }
59
60 /*
61 * Periodic tick
62 */
tick_periodic(int cpu)63 static void tick_periodic(int cpu)
64 {
65 if (tick_do_timer_cpu == cpu) {
66 write_seqlock(&jiffies_lock);
67
68 /* Keep track of the next tick event */
69 tick_next_period = ktime_add(tick_next_period, tick_period);
70
71 do_timer(1);
72 write_sequnlock(&jiffies_lock);
73 }
74
75 update_process_times(user_mode(get_irq_regs()));
76 profile_tick(CPU_PROFILING);
77 }
78
79 /*
80 * Event handler for periodic ticks
81 */
tick_handle_periodic(struct clock_event_device * dev)82 void tick_handle_periodic(struct clock_event_device *dev)
83 {
84 int cpu = smp_processor_id();
85 ktime_t next;
86
87 tick_periodic(cpu);
88
89 if (dev->mode != CLOCK_EVT_MODE_ONESHOT)
90 return;
91 /*
92 * Setup the next period for devices, which do not have
93 * periodic mode:
94 */
95 next = ktime_add(dev->next_event, tick_period);
96 for (;;) {
97 if (!clockevents_program_event(dev, next, false))
98 return;
99 /*
100 * Have to be careful here. If we're in oneshot mode,
101 * before we call tick_periodic() in a loop, we need
102 * to be sure we're using a real hardware clocksource.
103 * Otherwise we could get trapped in an infinite
104 * loop, as the tick_periodic() increments jiffies,
105 * when then will increment time, posibly causing
106 * the loop to trigger again and again.
107 */
108 if (timekeeping_valid_for_hres())
109 tick_periodic(cpu);
110 next = ktime_add(next, tick_period);
111 }
112 }
113
114 /*
115 * Setup the device for a periodic tick
116 */
tick_setup_periodic(struct clock_event_device * dev,int broadcast)117 void tick_setup_periodic(struct clock_event_device *dev, int broadcast)
118 {
119 tick_set_periodic_handler(dev, broadcast);
120
121 /* Broadcast setup ? */
122 if (!tick_device_is_functional(dev))
123 return;
124
125 if ((dev->features & CLOCK_EVT_FEAT_PERIODIC) &&
126 !tick_broadcast_oneshot_active()) {
127 clockevents_set_mode(dev, CLOCK_EVT_MODE_PERIODIC);
128 } else {
129 unsigned long seq;
130 ktime_t next;
131
132 do {
133 seq = read_seqbegin(&jiffies_lock);
134 next = tick_next_period;
135 } while (read_seqretry(&jiffies_lock, seq));
136
137 clockevents_set_mode(dev, CLOCK_EVT_MODE_ONESHOT);
138
139 for (;;) {
140 if (!clockevents_program_event(dev, next, false))
141 return;
142 next = ktime_add(next, tick_period);
143 }
144 }
145 }
146
147 /*
148 * Setup the tick device
149 */
tick_setup_device(struct tick_device * td,struct clock_event_device * newdev,int cpu,const struct cpumask * cpumask)150 static void tick_setup_device(struct tick_device *td,
151 struct clock_event_device *newdev, int cpu,
152 const struct cpumask *cpumask)
153 {
154 ktime_t next_event;
155 void (*handler)(struct clock_event_device *) = NULL;
156
157 /*
158 * First device setup ?
159 */
160 if (!td->evtdev) {
161 /*
162 * If no cpu took the do_timer update, assign it to
163 * this cpu:
164 */
165 if (tick_do_timer_cpu == TICK_DO_TIMER_BOOT) {
166 if (!tick_nohz_full_cpu(cpu))
167 tick_do_timer_cpu = cpu;
168 else
169 tick_do_timer_cpu = TICK_DO_TIMER_NONE;
170 tick_next_period = ktime_get();
171 tick_period = ktime_set(0, NSEC_PER_SEC / HZ);
172 }
173
174 /*
175 * Startup in periodic mode first.
176 */
177 td->mode = TICKDEV_MODE_PERIODIC;
178 } else {
179 handler = td->evtdev->event_handler;
180 next_event = td->evtdev->next_event;
181 td->evtdev->event_handler = clockevents_handle_noop;
182 }
183
184 td->evtdev = newdev;
185
186 /*
187 * When the device is not per cpu, pin the interrupt to the
188 * current cpu:
189 */
190 if (!cpumask_equal(newdev->cpumask, cpumask))
191 irq_set_affinity(newdev->irq, cpumask);
192
193 /*
194 * When global broadcasting is active, check if the current
195 * device is registered as a placeholder for broadcast mode.
196 * This allows us to handle this x86 misfeature in a generic
197 * way.
198 */
199 if (tick_device_uses_broadcast(newdev, cpu))
200 return;
201
202 if (td->mode == TICKDEV_MODE_PERIODIC)
203 tick_setup_periodic(newdev, 0);
204 else
205 tick_setup_oneshot(newdev, handler, next_event);
206 }
207
208 /*
209 * Check, if the new registered device should be used.
210 */
tick_check_new_device(struct clock_event_device * newdev)211 static int tick_check_new_device(struct clock_event_device *newdev)
212 {
213 struct clock_event_device *curdev;
214 struct tick_device *td;
215 int cpu, ret = NOTIFY_OK;
216 unsigned long flags;
217
218 raw_spin_lock_irqsave(&tick_device_lock, flags);
219
220 cpu = smp_processor_id();
221 if (!cpumask_test_cpu(cpu, newdev->cpumask))
222 goto out_bc;
223
224 td = &per_cpu(tick_cpu_device, cpu);
225 curdev = td->evtdev;
226
227 /* cpu local device ? */
228 if (!cpumask_equal(newdev->cpumask, cpumask_of(cpu))) {
229
230 /*
231 * If the cpu affinity of the device interrupt can not
232 * be set, ignore it.
233 */
234 if (!irq_can_set_affinity(newdev->irq))
235 goto out_bc;
236
237 /*
238 * If we have a cpu local device already, do not replace it
239 * by a non cpu local device
240 */
241 if (curdev && cpumask_equal(curdev->cpumask, cpumask_of(cpu)))
242 goto out_bc;
243 }
244
245 /*
246 * If we have an active device, then check the rating and the oneshot
247 * feature.
248 */
249 if (curdev) {
250 /*
251 * Prefer one shot capable devices !
252 */
253 if ((curdev->features & CLOCK_EVT_FEAT_ONESHOT) &&
254 !(newdev->features & CLOCK_EVT_FEAT_ONESHOT))
255 goto out_bc;
256 /*
257 * Check the rating
258 */
259 if (curdev->rating >= newdev->rating)
260 goto out_bc;
261 }
262
263 /*
264 * Replace the eventually existing device by the new
265 * device. If the current device is the broadcast device, do
266 * not give it back to the clockevents layer !
267 */
268 if (tick_is_broadcast_device(curdev)) {
269 clockevents_shutdown(curdev);
270 curdev = NULL;
271 }
272 clockevents_exchange_device(curdev, newdev);
273 tick_setup_device(td, newdev, cpu, cpumask_of(cpu));
274 if (newdev->features & CLOCK_EVT_FEAT_ONESHOT)
275 tick_oneshot_notify();
276
277 raw_spin_unlock_irqrestore(&tick_device_lock, flags);
278 return NOTIFY_STOP;
279
280 out_bc:
281 /*
282 * Can the new device be used as a broadcast device ?
283 */
284 if (tick_check_broadcast_device(newdev))
285 ret = NOTIFY_STOP;
286
287 raw_spin_unlock_irqrestore(&tick_device_lock, flags);
288
289 return ret;
290 }
291
292 /*
293 * Transfer the do_timer job away from a dying cpu.
294 *
295 * Called with interrupts disabled.
296 */
tick_handover_do_timer(int * cpup)297 static void tick_handover_do_timer(int *cpup)
298 {
299 if (*cpup == tick_do_timer_cpu) {
300 int cpu = cpumask_first(cpu_online_mask);
301
302 tick_do_timer_cpu = (cpu < nr_cpu_ids) ? cpu :
303 TICK_DO_TIMER_NONE;
304 }
305 }
306
307 /*
308 * Shutdown an event device on a given cpu:
309 *
310 * This is called on a life CPU, when a CPU is dead. So we cannot
311 * access the hardware device itself.
312 * We just set the mode and remove it from the lists.
313 */
tick_shutdown(unsigned int * cpup)314 static void tick_shutdown(unsigned int *cpup)
315 {
316 struct tick_device *td = &per_cpu(tick_cpu_device, *cpup);
317 struct clock_event_device *dev = td->evtdev;
318 unsigned long flags;
319
320 raw_spin_lock_irqsave(&tick_device_lock, flags);
321 td->mode = TICKDEV_MODE_PERIODIC;
322 if (dev) {
323 /*
324 * Prevent that the clock events layer tries to call
325 * the set mode function!
326 */
327 dev->mode = CLOCK_EVT_MODE_UNUSED;
328 clockevents_exchange_device(dev, NULL);
329 dev->event_handler = clockevents_handle_noop;
330 td->evtdev = NULL;
331 }
332 raw_spin_unlock_irqrestore(&tick_device_lock, flags);
333 }
334
tick_suspend(void)335 static void tick_suspend(void)
336 {
337 struct tick_device *td = &__get_cpu_var(tick_cpu_device);
338 unsigned long flags;
339
340 raw_spin_lock_irqsave(&tick_device_lock, flags);
341 clockevents_shutdown(td->evtdev);
342 raw_spin_unlock_irqrestore(&tick_device_lock, flags);
343 }
344
tick_resume(void)345 static void tick_resume(void)
346 {
347 struct tick_device *td = &__get_cpu_var(tick_cpu_device);
348 unsigned long flags;
349 int broadcast = tick_resume_broadcast();
350
351 raw_spin_lock_irqsave(&tick_device_lock, flags);
352 clockevents_set_mode(td->evtdev, CLOCK_EVT_MODE_RESUME);
353
354 if (!broadcast) {
355 if (td->mode == TICKDEV_MODE_PERIODIC)
356 tick_setup_periodic(td->evtdev, 0);
357 else
358 tick_resume_oneshot();
359 }
360 raw_spin_unlock_irqrestore(&tick_device_lock, flags);
361 }
362
363 /*
364 * Notification about clock event devices
365 */
tick_notify(struct notifier_block * nb,unsigned long reason,void * dev)366 static int tick_notify(struct notifier_block *nb, unsigned long reason,
367 void *dev)
368 {
369 switch (reason) {
370
371 case CLOCK_EVT_NOTIFY_ADD:
372 return tick_check_new_device(dev);
373
374 case CLOCK_EVT_NOTIFY_BROADCAST_ON:
375 case CLOCK_EVT_NOTIFY_BROADCAST_OFF:
376 case CLOCK_EVT_NOTIFY_BROADCAST_FORCE:
377 tick_broadcast_on_off(reason, dev);
378 break;
379
380 case CLOCK_EVT_NOTIFY_BROADCAST_ENTER:
381 case CLOCK_EVT_NOTIFY_BROADCAST_EXIT:
382 tick_broadcast_oneshot_control(reason);
383 break;
384
385 case CLOCK_EVT_NOTIFY_CPU_DYING:
386 tick_handover_do_timer(dev);
387 break;
388
389 case CLOCK_EVT_NOTIFY_CPU_DEAD:
390 tick_shutdown_broadcast_oneshot(dev);
391 tick_shutdown_broadcast(dev);
392 tick_shutdown(dev);
393 break;
394
395 case CLOCK_EVT_NOTIFY_SUSPEND:
396 tick_suspend();
397 tick_suspend_broadcast();
398 break;
399
400 case CLOCK_EVT_NOTIFY_RESUME:
401 tick_resume();
402 break;
403
404 default:
405 break;
406 }
407
408 return NOTIFY_OK;
409 }
410
411 static struct notifier_block tick_notifier = {
412 .notifier_call = tick_notify,
413 };
414
415 /**
416 * tick_init - initialize the tick control
417 *
418 * Register the notifier with the clockevents framework
419 */
tick_init(void)420 void __init tick_init(void)
421 {
422 clockevents_register_notifier(&tick_notifier);
423 tick_broadcast_init();
424 }
425