xref: /openbmc/linux/kernel/time/tick-common.c (revision 4800cd83) 
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 #include <linux/tick.h>
22 
23 #include <asm/irq_regs.h>
24 
25 #include "tick-internal.h"
26 
27 /*
28  * Tick devices
29  */
30 DEFINE_PER_CPU(struct tick_device, tick_cpu_device);
31 /*
32  * Tick next event: keeps track of the tick time
33  */
34 ktime_t tick_next_period;
35 ktime_t tick_period;
36 int tick_do_timer_cpu __read_mostly = TICK_DO_TIMER_BOOT;
37 static DEFINE_RAW_SPINLOCK(tick_device_lock);
38 
39 /*
40  * Debugging: see timer_list.c
41  */
42 struct tick_device *tick_get_device(int cpu)
43 {
44 	return &per_cpu(tick_cpu_device, cpu);
45 }
46 
47 /**
48  * tick_is_oneshot_available - check for a oneshot capable event device
49  */
50 int tick_is_oneshot_available(void)
51 {
52 	struct clock_event_device *dev = __this_cpu_read(tick_cpu_device.evtdev);
53 
54 	if (!dev || !(dev->features & CLOCK_EVT_FEAT_ONESHOT))
55 		return 0;
56 	if (!(dev->features & CLOCK_EVT_FEAT_C3STOP))
57 		return 1;
58 	return tick_broadcast_oneshot_available();
59 }
60 
61 /*
62  * Periodic tick
63  */
64 static void tick_periodic(int cpu)
65 {
66 	if (tick_do_timer_cpu == cpu) {
67 		write_seqlock(&xtime_lock);
68 
69 		/* Keep track of the next tick event */
70 		tick_next_period = ktime_add(tick_next_period, tick_period);
71 
72 		do_timer(1);
73 		write_sequnlock(&xtime_lock);
74 	}
75 
76 	update_process_times(user_mode(get_irq_regs()));
77 	profile_tick(CPU_PROFILING);
78 }
79 
80 /*
81  * Event handler for periodic ticks
82  */
83 void tick_handle_periodic(struct clock_event_device *dev)
84 {
85 	int cpu = smp_processor_id();
86 	ktime_t next;
87 
88 	tick_periodic(cpu);
89 
90 	if (dev->mode != CLOCK_EVT_MODE_ONESHOT)
91 		return;
92 	/*
93 	 * Setup the next period for devices, which do not have
94 	 * periodic mode:
95 	 */
96 	next = ktime_add(dev->next_event, tick_period);
97 	for (;;) {
98 		if (!clockevents_program_event(dev, next, ktime_get()))
99 			return;
100 		/*
101 		 * Have to be careful here. If we're in oneshot mode,
102 		 * before we call tick_periodic() in a loop, we need
103 		 * to be sure we're using a real hardware clocksource.
104 		 * Otherwise we could get trapped in an infinite
105 		 * loop, as the tick_periodic() increments jiffies,
106 		 * when then will increment time, posibly causing
107 		 * the loop to trigger again and again.
108 		 */
109 		if (timekeeping_valid_for_hres())
110 			tick_periodic(cpu);
111 		next = ktime_add(next, tick_period);
112 	}
113 }
114 
115 /*
116  * Setup the device for a periodic tick
117  */
118 void tick_setup_periodic(struct clock_event_device *dev, int broadcast)
119 {
120 	tick_set_periodic_handler(dev, broadcast);
121 
122 	/* Broadcast setup ? */
123 	if (!tick_device_is_functional(dev))
124 		return;
125 
126 	if ((dev->features & CLOCK_EVT_FEAT_PERIODIC) &&
127 	    !tick_broadcast_oneshot_active()) {
128 		clockevents_set_mode(dev, CLOCK_EVT_MODE_PERIODIC);
129 	} else {
130 		unsigned long seq;
131 		ktime_t next;
132 
133 		do {
134 			seq = read_seqbegin(&xtime_lock);
135 			next = tick_next_period;
136 		} while (read_seqretry(&xtime_lock, seq));
137 
138 		clockevents_set_mode(dev, CLOCK_EVT_MODE_ONESHOT);
139 
140 		for (;;) {
141 			if (!clockevents_program_event(dev, next, ktime_get()))
142 				return;
143 			next = ktime_add(next, tick_period);
144 		}
145 	}
146 }
147 
148 /*
149  * Setup the tick device
150  */
151 static void tick_setup_device(struct tick_device *td,
152 			      struct clock_event_device *newdev, int cpu,
153 			      const struct cpumask *cpumask)
154 {
155 	ktime_t next_event;
156 	void (*handler)(struct clock_event_device *) = NULL;
157 
158 	/*
159 	 * First device setup ?
160 	 */
161 	if (!td->evtdev) {
162 		/*
163 		 * If no cpu took the do_timer update, assign it to
164 		 * this cpu:
165 		 */
166 		if (tick_do_timer_cpu == TICK_DO_TIMER_BOOT) {
167 			tick_do_timer_cpu = cpu;
168 			tick_next_period = ktime_get();
169 			tick_period = ktime_set(0, NSEC_PER_SEC / HZ);
170 		}
171 
172 		/*
173 		 * Startup in periodic mode first.
174 		 */
175 		td->mode = TICKDEV_MODE_PERIODIC;
176 	} else {
177 		handler = td->evtdev->event_handler;
178 		next_event = td->evtdev->next_event;
179 		td->evtdev->event_handler = clockevents_handle_noop;
180 	}
181 
182 	td->evtdev = newdev;
183 
184 	/*
185 	 * When the device is not per cpu, pin the interrupt to the
186 	 * current cpu:
187 	 */
188 	if (!cpumask_equal(newdev->cpumask, cpumask))
189 		irq_set_affinity(newdev->irq, cpumask);
190 
191 	/*
192 	 * When global broadcasting is active, check if the current
193 	 * device is registered as a placeholder for broadcast mode.
194 	 * This allows us to handle this x86 misfeature in a generic
195 	 * way.
196 	 */
197 	if (tick_device_uses_broadcast(newdev, cpu))
198 		return;
199 
200 	if (td->mode == TICKDEV_MODE_PERIODIC)
201 		tick_setup_periodic(newdev, 0);
202 	else
203 		tick_setup_oneshot(newdev, handler, next_event);
204 }
205 
206 /*
207  * Check, if the new registered device should be used.
208  */
209 static int tick_check_new_device(struct clock_event_device *newdev)
210 {
211 	struct clock_event_device *curdev;
212 	struct tick_device *td;
213 	int cpu, ret = NOTIFY_OK;
214 	unsigned long flags;
215 
216 	raw_spin_lock_irqsave(&tick_device_lock, flags);
217 
218 	cpu = smp_processor_id();
219 	if (!cpumask_test_cpu(cpu, newdev->cpumask))
220 		goto out_bc;
221 
222 	td = &per_cpu(tick_cpu_device, cpu);
223 	curdev = td->evtdev;
224 
225 	/* cpu local device ? */
226 	if (!cpumask_equal(newdev->cpumask, cpumask_of(cpu))) {
227 
228 		/*
229 		 * If the cpu affinity of the device interrupt can not
230 		 * be set, ignore it.
231 		 */
232 		if (!irq_can_set_affinity(newdev->irq))
233 			goto out_bc;
234 
235 		/*
236 		 * If we have a cpu local device already, do not replace it
237 		 * by a non cpu local device
238 		 */
239 		if (curdev && cpumask_equal(curdev->cpumask, cpumask_of(cpu)))
240 			goto out_bc;
241 	}
242 
243 	/*
244 	 * If we have an active device, then check the rating and the oneshot
245 	 * feature.
246 	 */
247 	if (curdev) {
248 		/*
249 		 * Prefer one shot capable devices !
250 		 */
251 		if ((curdev->features & CLOCK_EVT_FEAT_ONESHOT) &&
252 		    !(newdev->features & CLOCK_EVT_FEAT_ONESHOT))
253 			goto out_bc;
254 		/*
255 		 * Check the rating
256 		 */
257 		if (curdev->rating >= newdev->rating)
258 			goto out_bc;
259 	}
260 
261 	/*
262 	 * Replace the eventually existing device by the new
263 	 * device. If the current device is the broadcast device, do
264 	 * not give it back to the clockevents layer !
265 	 */
266 	if (tick_is_broadcast_device(curdev)) {
267 		clockevents_shutdown(curdev);
268 		curdev = NULL;
269 	}
270 	clockevents_exchange_device(curdev, newdev);
271 	tick_setup_device(td, newdev, cpu, cpumask_of(cpu));
272 	if (newdev->features & CLOCK_EVT_FEAT_ONESHOT)
273 		tick_oneshot_notify();
274 
275 	raw_spin_unlock_irqrestore(&tick_device_lock, flags);
276 	return NOTIFY_STOP;
277 
278 out_bc:
279 	/*
280 	 * Can the new device be used as a broadcast device ?
281 	 */
282 	if (tick_check_broadcast_device(newdev))
283 		ret = NOTIFY_STOP;
284 
285 	raw_spin_unlock_irqrestore(&tick_device_lock, flags);
286 
287 	return ret;
288 }
289 
290 /*
291  * Transfer the do_timer job away from a dying cpu.
292  *
293  * Called with interrupts disabled.
294  */
295 static void tick_handover_do_timer(int *cpup)
296 {
297 	if (*cpup == tick_do_timer_cpu) {
298 		int cpu = cpumask_first(cpu_online_mask);
299 
300 		tick_do_timer_cpu = (cpu < nr_cpu_ids) ? cpu :
301 			TICK_DO_TIMER_NONE;
302 	}
303 }
304 
305 /*
306  * Shutdown an event device on a given cpu:
307  *
308  * This is called on a life CPU, when a CPU is dead. So we cannot
309  * access the hardware device itself.
310  * We just set the mode and remove it from the lists.
311  */
312 static void tick_shutdown(unsigned int *cpup)
313 {
314 	struct tick_device *td = &per_cpu(tick_cpu_device, *cpup);
315 	struct clock_event_device *dev = td->evtdev;
316 	unsigned long flags;
317 
318 	raw_spin_lock_irqsave(&tick_device_lock, flags);
319 	td->mode = TICKDEV_MODE_PERIODIC;
320 	if (dev) {
321 		/*
322 		 * Prevent that the clock events layer tries to call
323 		 * the set mode function!
324 		 */
325 		dev->mode = CLOCK_EVT_MODE_UNUSED;
326 		clockevents_exchange_device(dev, NULL);
327 		td->evtdev = NULL;
328 	}
329 	raw_spin_unlock_irqrestore(&tick_device_lock, flags);
330 }
331 
332 static void tick_suspend(void)
333 {
334 	struct tick_device *td = &__get_cpu_var(tick_cpu_device);
335 	unsigned long flags;
336 
337 	raw_spin_lock_irqsave(&tick_device_lock, flags);
338 	clockevents_shutdown(td->evtdev);
339 	raw_spin_unlock_irqrestore(&tick_device_lock, flags);
340 }
341 
342 static void tick_resume(void)
343 {
344 	struct tick_device *td = &__get_cpu_var(tick_cpu_device);
345 	unsigned long flags;
346 	int broadcast = tick_resume_broadcast();
347 
348 	raw_spin_lock_irqsave(&tick_device_lock, flags);
349 	clockevents_set_mode(td->evtdev, CLOCK_EVT_MODE_RESUME);
350 
351 	if (!broadcast) {
352 		if (td->mode == TICKDEV_MODE_PERIODIC)
353 			tick_setup_periodic(td->evtdev, 0);
354 		else
355 			tick_resume_oneshot();
356 	}
357 	raw_spin_unlock_irqrestore(&tick_device_lock, flags);
358 }
359 
360 /*
361  * Notification about clock event devices
362  */
363 static int tick_notify(struct notifier_block *nb, unsigned long reason,
364 			       void *dev)
365 {
366 	switch (reason) {
367 
368 	case CLOCK_EVT_NOTIFY_ADD:
369 		return tick_check_new_device(dev);
370 
371 	case CLOCK_EVT_NOTIFY_BROADCAST_ON:
372 	case CLOCK_EVT_NOTIFY_BROADCAST_OFF:
373 	case CLOCK_EVT_NOTIFY_BROADCAST_FORCE:
374 		tick_broadcast_on_off(reason, dev);
375 		break;
376 
377 	case CLOCK_EVT_NOTIFY_BROADCAST_ENTER:
378 	case CLOCK_EVT_NOTIFY_BROADCAST_EXIT:
379 		tick_broadcast_oneshot_control(reason);
380 		break;
381 
382 	case CLOCK_EVT_NOTIFY_CPU_DYING:
383 		tick_handover_do_timer(dev);
384 		break;
385 
386 	case CLOCK_EVT_NOTIFY_CPU_DEAD:
387 		tick_shutdown_broadcast_oneshot(dev);
388 		tick_shutdown_broadcast(dev);
389 		tick_shutdown(dev);
390 		break;
391 
392 	case CLOCK_EVT_NOTIFY_SUSPEND:
393 		tick_suspend();
394 		tick_suspend_broadcast();
395 		break;
396 
397 	case CLOCK_EVT_NOTIFY_RESUME:
398 		tick_resume();
399 		break;
400 
401 	default:
402 		break;
403 	}
404 
405 	return NOTIFY_OK;
406 }
407 
408 static struct notifier_block tick_notifier = {
409 	.notifier_call = tick_notify,
410 };
411 
412 /**
413  * tick_init - initialize the tick control
414  *
415  * Register the notifier with the clockevents framework
416  */
417 void __init tick_init(void)
418 {
419 	clockevents_register_notifier(&tick_notifier);
420 }
421