xref: /openbmc/linux/kernel/time/tick-common.c (revision f35e839a) 
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  */
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  */
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  */
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  */
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  */
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  */
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  */
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  */
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  */
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 
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 
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  */
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  */
420 void __init tick_init(void)
421 {
422 	clockevents_register_notifier(&tick_notifier);
423 	tick_broadcast_init();
424 }
425