1 // SPDX-License-Identifier: GPL-2.0
2 /*
3  * This file contains functions which emulate a local clock-event
4  * device via a broadcast event source.
5  *
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
9  */
10 #include <linux/cpu.h>
11 #include <linux/err.h>
12 #include <linux/hrtimer.h>
13 #include <linux/interrupt.h>
14 #include <linux/percpu.h>
15 #include <linux/profile.h>
16 #include <linux/sched.h>
17 #include <linux/smp.h>
18 #include <linux/module.h>
19 
20 #include "tick-internal.h"
21 
22 /*
23  * Broadcast support for broken x86 hardware, where the local apic
24  * timer stops in C3 state.
25  */
26 
27 static struct tick_device tick_broadcast_device;
28 static cpumask_var_t tick_broadcast_mask __cpumask_var_read_mostly;
29 static cpumask_var_t tick_broadcast_on __cpumask_var_read_mostly;
30 static cpumask_var_t tmpmask __cpumask_var_read_mostly;
31 static int tick_broadcast_forced;
32 
33 static __cacheline_aligned_in_smp DEFINE_RAW_SPINLOCK(tick_broadcast_lock);
34 
35 #ifdef CONFIG_TICK_ONESHOT
36 static DEFINE_PER_CPU(struct clock_event_device *, tick_oneshot_wakeup_device);
37 
38 static void tick_broadcast_setup_oneshot(struct clock_event_device *bc);
39 static void tick_broadcast_clear_oneshot(int cpu);
40 static void tick_resume_broadcast_oneshot(struct clock_event_device *bc);
41 # ifdef CONFIG_HOTPLUG_CPU
42 static void tick_broadcast_oneshot_offline(unsigned int cpu);
43 # endif
44 #else
tick_broadcast_setup_oneshot(struct clock_event_device * bc)45 static inline void tick_broadcast_setup_oneshot(struct clock_event_device *bc) { BUG(); }
tick_broadcast_clear_oneshot(int cpu)46 static inline void tick_broadcast_clear_oneshot(int cpu) { }
tick_resume_broadcast_oneshot(struct clock_event_device * bc)47 static inline void tick_resume_broadcast_oneshot(struct clock_event_device *bc) { }
48 # ifdef CONFIG_HOTPLUG_CPU
tick_broadcast_oneshot_offline(unsigned int cpu)49 static inline void tick_broadcast_oneshot_offline(unsigned int cpu) { }
50 # endif
51 #endif
52 
53 /*
54  * Debugging: see timer_list.c
55  */
tick_get_broadcast_device(void)56 struct tick_device *tick_get_broadcast_device(void)
57 {
58 	return &tick_broadcast_device;
59 }
60 
tick_get_broadcast_mask(void)61 struct cpumask *tick_get_broadcast_mask(void)
62 {
63 	return tick_broadcast_mask;
64 }
65 
66 static struct clock_event_device *tick_get_oneshot_wakeup_device(int cpu);
67 
tick_get_wakeup_device(int cpu)68 const struct clock_event_device *tick_get_wakeup_device(int cpu)
69 {
70 	return tick_get_oneshot_wakeup_device(cpu);
71 }
72 
73 /*
74  * Start the device in periodic mode
75  */
tick_broadcast_start_periodic(struct clock_event_device * bc)76 static void tick_broadcast_start_periodic(struct clock_event_device *bc)
77 {
78 	if (bc)
79 		tick_setup_periodic(bc, 1);
80 }
81 
82 /*
83  * Check, if the device can be utilized as broadcast device:
84  */
tick_check_broadcast_device(struct clock_event_device * curdev,struct clock_event_device * newdev)85 static bool tick_check_broadcast_device(struct clock_event_device *curdev,
86 					struct clock_event_device *newdev)
87 {
88 	if ((newdev->features & CLOCK_EVT_FEAT_DUMMY) ||
89 	    (newdev->features & CLOCK_EVT_FEAT_PERCPU) ||
90 	    (newdev->features & CLOCK_EVT_FEAT_C3STOP))
91 		return false;
92 
93 	if (tick_broadcast_device.mode == TICKDEV_MODE_ONESHOT &&
94 	    !(newdev->features & CLOCK_EVT_FEAT_ONESHOT))
95 		return false;
96 
97 	return !curdev || newdev->rating > curdev->rating;
98 }
99 
100 #ifdef CONFIG_TICK_ONESHOT
tick_get_oneshot_wakeup_device(int cpu)101 static struct clock_event_device *tick_get_oneshot_wakeup_device(int cpu)
102 {
103 	return per_cpu(tick_oneshot_wakeup_device, cpu);
104 }
105 
tick_oneshot_wakeup_handler(struct clock_event_device * wd)106 static void tick_oneshot_wakeup_handler(struct clock_event_device *wd)
107 {
108 	/*
109 	 * If we woke up early and the tick was reprogrammed in the
110 	 * meantime then this may be spurious but harmless.
111 	 */
112 	tick_receive_broadcast();
113 }
114 
tick_set_oneshot_wakeup_device(struct clock_event_device * newdev,int cpu)115 static bool tick_set_oneshot_wakeup_device(struct clock_event_device *newdev,
116 					   int cpu)
117 {
118 	struct clock_event_device *curdev = tick_get_oneshot_wakeup_device(cpu);
119 
120 	if (!newdev)
121 		goto set_device;
122 
123 	if ((newdev->features & CLOCK_EVT_FEAT_DUMMY) ||
124 	    (newdev->features & CLOCK_EVT_FEAT_C3STOP))
125 		 return false;
126 
127 	if (!(newdev->features & CLOCK_EVT_FEAT_PERCPU) ||
128 	    !(newdev->features & CLOCK_EVT_FEAT_ONESHOT))
129 		return false;
130 
131 	if (!cpumask_equal(newdev->cpumask, cpumask_of(cpu)))
132 		return false;
133 
134 	if (curdev && newdev->rating <= curdev->rating)
135 		return false;
136 
137 	if (!try_module_get(newdev->owner))
138 		return false;
139 
140 	newdev->event_handler = tick_oneshot_wakeup_handler;
141 set_device:
142 	clockevents_exchange_device(curdev, newdev);
143 	per_cpu(tick_oneshot_wakeup_device, cpu) = newdev;
144 	return true;
145 }
146 #else
tick_get_oneshot_wakeup_device(int cpu)147 static struct clock_event_device *tick_get_oneshot_wakeup_device(int cpu)
148 {
149 	return NULL;
150 }
151 
tick_set_oneshot_wakeup_device(struct clock_event_device * newdev,int cpu)152 static bool tick_set_oneshot_wakeup_device(struct clock_event_device *newdev,
153 					   int cpu)
154 {
155 	return false;
156 }
157 #endif
158 
159 /*
160  * Conditionally install/replace broadcast device
161  */
tick_install_broadcast_device(struct clock_event_device * dev,int cpu)162 void tick_install_broadcast_device(struct clock_event_device *dev, int cpu)
163 {
164 	struct clock_event_device *cur = tick_broadcast_device.evtdev;
165 
166 	if (tick_set_oneshot_wakeup_device(dev, cpu))
167 		return;
168 
169 	if (!tick_check_broadcast_device(cur, dev))
170 		return;
171 
172 	if (!try_module_get(dev->owner))
173 		return;
174 
175 	clockevents_exchange_device(cur, dev);
176 	if (cur)
177 		cur->event_handler = clockevents_handle_noop;
178 	tick_broadcast_device.evtdev = dev;
179 	if (!cpumask_empty(tick_broadcast_mask))
180 		tick_broadcast_start_periodic(dev);
181 
182 	if (!(dev->features & CLOCK_EVT_FEAT_ONESHOT))
183 		return;
184 
185 	/*
186 	 * If the system already runs in oneshot mode, switch the newly
187 	 * registered broadcast device to oneshot mode explicitly.
188 	 */
189 	if (tick_broadcast_oneshot_active()) {
190 		tick_broadcast_switch_to_oneshot();
191 		return;
192 	}
193 
194 	/*
195 	 * Inform all cpus about this. We might be in a situation
196 	 * where we did not switch to oneshot mode because the per cpu
197 	 * devices are affected by CLOCK_EVT_FEAT_C3STOP and the lack
198 	 * of a oneshot capable broadcast device. Without that
199 	 * notification the systems stays stuck in periodic mode
200 	 * forever.
201 	 */
202 	tick_clock_notify();
203 }
204 
205 /*
206  * Check, if the device is the broadcast device
207  */
tick_is_broadcast_device(struct clock_event_device * dev)208 int tick_is_broadcast_device(struct clock_event_device *dev)
209 {
210 	return (dev && tick_broadcast_device.evtdev == dev);
211 }
212 
tick_broadcast_update_freq(struct clock_event_device * dev,u32 freq)213 int tick_broadcast_update_freq(struct clock_event_device *dev, u32 freq)
214 {
215 	int ret = -ENODEV;
216 
217 	if (tick_is_broadcast_device(dev)) {
218 		raw_spin_lock(&tick_broadcast_lock);
219 		ret = __clockevents_update_freq(dev, freq);
220 		raw_spin_unlock(&tick_broadcast_lock);
221 	}
222 	return ret;
223 }
224 
225 
err_broadcast(const struct cpumask * mask)226 static void err_broadcast(const struct cpumask *mask)
227 {
228 	pr_crit_once("Failed to broadcast timer tick. Some CPUs may be unresponsive.\n");
229 }
230 
tick_device_setup_broadcast_func(struct clock_event_device * dev)231 static void tick_device_setup_broadcast_func(struct clock_event_device *dev)
232 {
233 	if (!dev->broadcast)
234 		dev->broadcast = tick_broadcast;
235 	if (!dev->broadcast) {
236 		pr_warn_once("%s depends on broadcast, but no broadcast function available\n",
237 			     dev->name);
238 		dev->broadcast = err_broadcast;
239 	}
240 }
241 
242 /*
243  * Check, if the device is dysfunctional and a placeholder, which
244  * needs to be handled by the broadcast device.
245  */
tick_device_uses_broadcast(struct clock_event_device * dev,int cpu)246 int tick_device_uses_broadcast(struct clock_event_device *dev, int cpu)
247 {
248 	struct clock_event_device *bc = tick_broadcast_device.evtdev;
249 	unsigned long flags;
250 	int ret = 0;
251 
252 	raw_spin_lock_irqsave(&tick_broadcast_lock, flags);
253 
254 	/*
255 	 * Devices might be registered with both periodic and oneshot
256 	 * mode disabled. This signals, that the device needs to be
257 	 * operated from the broadcast device and is a placeholder for
258 	 * the cpu local device.
259 	 */
260 	if (!tick_device_is_functional(dev)) {
261 		dev->event_handler = tick_handle_periodic;
262 		tick_device_setup_broadcast_func(dev);
263 		cpumask_set_cpu(cpu, tick_broadcast_mask);
264 		if (tick_broadcast_device.mode == TICKDEV_MODE_PERIODIC)
265 			tick_broadcast_start_periodic(bc);
266 		else
267 			tick_broadcast_setup_oneshot(bc);
268 		ret = 1;
269 	} else {
270 		/*
271 		 * Clear the broadcast bit for this cpu if the
272 		 * device is not power state affected.
273 		 */
274 		if (!(dev->features & CLOCK_EVT_FEAT_C3STOP))
275 			cpumask_clear_cpu(cpu, tick_broadcast_mask);
276 		else
277 			tick_device_setup_broadcast_func(dev);
278 
279 		/*
280 		 * Clear the broadcast bit if the CPU is not in
281 		 * periodic broadcast on state.
282 		 */
283 		if (!cpumask_test_cpu(cpu, tick_broadcast_on))
284 			cpumask_clear_cpu(cpu, tick_broadcast_mask);
285 
286 		switch (tick_broadcast_device.mode) {
287 		case TICKDEV_MODE_ONESHOT:
288 			/*
289 			 * If the system is in oneshot mode we can
290 			 * unconditionally clear the oneshot mask bit,
291 			 * because the CPU is running and therefore
292 			 * not in an idle state which causes the power
293 			 * state affected device to stop. Let the
294 			 * caller initialize the device.
295 			 */
296 			tick_broadcast_clear_oneshot(cpu);
297 			ret = 0;
298 			break;
299 
300 		case TICKDEV_MODE_PERIODIC:
301 			/*
302 			 * If the system is in periodic mode, check
303 			 * whether the broadcast device can be
304 			 * switched off now.
305 			 */
306 			if (cpumask_empty(tick_broadcast_mask) && bc)
307 				clockevents_shutdown(bc);
308 			/*
309 			 * If we kept the cpu in the broadcast mask,
310 			 * tell the caller to leave the per cpu device
311 			 * in shutdown state. The periodic interrupt
312 			 * is delivered by the broadcast device, if
313 			 * the broadcast device exists and is not
314 			 * hrtimer based.
315 			 */
316 			if (bc && !(bc->features & CLOCK_EVT_FEAT_HRTIMER))
317 				ret = cpumask_test_cpu(cpu, tick_broadcast_mask);
318 			break;
319 		default:
320 			break;
321 		}
322 	}
323 	raw_spin_unlock_irqrestore(&tick_broadcast_lock, flags);
324 	return ret;
325 }
326 
tick_receive_broadcast(void)327 int tick_receive_broadcast(void)
328 {
329 	struct tick_device *td = this_cpu_ptr(&tick_cpu_device);
330 	struct clock_event_device *evt = td->evtdev;
331 
332 	if (!evt)
333 		return -ENODEV;
334 
335 	if (!evt->event_handler)
336 		return -EINVAL;
337 
338 	evt->event_handler(evt);
339 	return 0;
340 }
341 
342 /*
343  * Broadcast the event to the cpus, which are set in the mask (mangled).
344  */
tick_do_broadcast(struct cpumask * mask)345 static bool tick_do_broadcast(struct cpumask *mask)
346 {
347 	int cpu = smp_processor_id();
348 	struct tick_device *td;
349 	bool local = false;
350 
351 	/*
352 	 * Check, if the current cpu is in the mask
353 	 */
354 	if (cpumask_test_cpu(cpu, mask)) {
355 		struct clock_event_device *bc = tick_broadcast_device.evtdev;
356 
357 		cpumask_clear_cpu(cpu, mask);
358 		/*
359 		 * We only run the local handler, if the broadcast
360 		 * device is not hrtimer based. Otherwise we run into
361 		 * a hrtimer recursion.
362 		 *
363 		 * local timer_interrupt()
364 		 *   local_handler()
365 		 *     expire_hrtimers()
366 		 *       bc_handler()
367 		 *         local_handler()
368 		 *	     expire_hrtimers()
369 		 */
370 		local = !(bc->features & CLOCK_EVT_FEAT_HRTIMER);
371 	}
372 
373 	if (!cpumask_empty(mask)) {
374 		/*
375 		 * It might be necessary to actually check whether the devices
376 		 * have different broadcast functions. For now, just use the
377 		 * one of the first device. This works as long as we have this
378 		 * misfeature only on x86 (lapic)
379 		 */
380 		td = &per_cpu(tick_cpu_device, cpumask_first(mask));
381 		td->evtdev->broadcast(mask);
382 	}
383 	return local;
384 }
385 
386 /*
387  * Periodic broadcast:
388  * - invoke the broadcast handlers
389  */
tick_do_periodic_broadcast(void)390 static bool tick_do_periodic_broadcast(void)
391 {
392 	cpumask_and(tmpmask, cpu_online_mask, tick_broadcast_mask);
393 	return tick_do_broadcast(tmpmask);
394 }
395 
396 /*
397  * Event handler for periodic broadcast ticks
398  */
tick_handle_periodic_broadcast(struct clock_event_device * dev)399 static void tick_handle_periodic_broadcast(struct clock_event_device *dev)
400 {
401 	struct tick_device *td = this_cpu_ptr(&tick_cpu_device);
402 	bool bc_local;
403 
404 	raw_spin_lock(&tick_broadcast_lock);
405 
406 	/* Handle spurious interrupts gracefully */
407 	if (clockevent_state_shutdown(tick_broadcast_device.evtdev)) {
408 		raw_spin_unlock(&tick_broadcast_lock);
409 		return;
410 	}
411 
412 	bc_local = tick_do_periodic_broadcast();
413 
414 	if (clockevent_state_oneshot(dev)) {
415 		ktime_t next = ktime_add_ns(dev->next_event, TICK_NSEC);
416 
417 		clockevents_program_event(dev, next, true);
418 	}
419 	raw_spin_unlock(&tick_broadcast_lock);
420 
421 	/*
422 	 * We run the handler of the local cpu after dropping
423 	 * tick_broadcast_lock because the handler might deadlock when
424 	 * trying to switch to oneshot mode.
425 	 */
426 	if (bc_local)
427 		td->evtdev->event_handler(td->evtdev);
428 }
429 
430 /**
431  * tick_broadcast_control - Enable/disable or force broadcast mode
432  * @mode:	The selected broadcast mode
433  *
434  * Called when the system enters a state where affected tick devices
435  * might stop. Note: TICK_BROADCAST_FORCE cannot be undone.
436  */
tick_broadcast_control(enum tick_broadcast_mode mode)437 void tick_broadcast_control(enum tick_broadcast_mode mode)
438 {
439 	struct clock_event_device *bc, *dev;
440 	struct tick_device *td;
441 	int cpu, bc_stopped;
442 	unsigned long flags;
443 
444 	/* Protects also the local clockevent device. */
445 	raw_spin_lock_irqsave(&tick_broadcast_lock, flags);
446 	td = this_cpu_ptr(&tick_cpu_device);
447 	dev = td->evtdev;
448 
449 	/*
450 	 * Is the device not affected by the powerstate ?
451 	 */
452 	if (!dev || !(dev->features & CLOCK_EVT_FEAT_C3STOP))
453 		goto out;
454 
455 	if (!tick_device_is_functional(dev))
456 		goto out;
457 
458 	cpu = smp_processor_id();
459 	bc = tick_broadcast_device.evtdev;
460 	bc_stopped = cpumask_empty(tick_broadcast_mask);
461 
462 	switch (mode) {
463 	case TICK_BROADCAST_FORCE:
464 		tick_broadcast_forced = 1;
465 		fallthrough;
466 	case TICK_BROADCAST_ON:
467 		cpumask_set_cpu(cpu, tick_broadcast_on);
468 		if (!cpumask_test_and_set_cpu(cpu, tick_broadcast_mask)) {
469 			/*
470 			 * Only shutdown the cpu local device, if:
471 			 *
472 			 * - the broadcast device exists
473 			 * - the broadcast device is not a hrtimer based one
474 			 * - the broadcast device is in periodic mode to
475 			 *   avoid a hiccup during switch to oneshot mode
476 			 */
477 			if (bc && !(bc->features & CLOCK_EVT_FEAT_HRTIMER) &&
478 			    tick_broadcast_device.mode == TICKDEV_MODE_PERIODIC)
479 				clockevents_shutdown(dev);
480 		}
481 		break;
482 
483 	case TICK_BROADCAST_OFF:
484 		if (tick_broadcast_forced)
485 			break;
486 		cpumask_clear_cpu(cpu, tick_broadcast_on);
487 		if (cpumask_test_and_clear_cpu(cpu, tick_broadcast_mask)) {
488 			if (tick_broadcast_device.mode ==
489 			    TICKDEV_MODE_PERIODIC)
490 				tick_setup_periodic(dev, 0);
491 		}
492 		break;
493 	}
494 
495 	if (bc) {
496 		if (cpumask_empty(tick_broadcast_mask)) {
497 			if (!bc_stopped)
498 				clockevents_shutdown(bc);
499 		} else if (bc_stopped) {
500 			if (tick_broadcast_device.mode == TICKDEV_MODE_PERIODIC)
501 				tick_broadcast_start_periodic(bc);
502 			else
503 				tick_broadcast_setup_oneshot(bc);
504 		}
505 	}
506 out:
507 	raw_spin_unlock_irqrestore(&tick_broadcast_lock, flags);
508 }
509 EXPORT_SYMBOL_GPL(tick_broadcast_control);
510 
511 /*
512  * Set the periodic handler depending on broadcast on/off
513  */
tick_set_periodic_handler(struct clock_event_device * dev,int broadcast)514 void tick_set_periodic_handler(struct clock_event_device *dev, int broadcast)
515 {
516 	if (!broadcast)
517 		dev->event_handler = tick_handle_periodic;
518 	else
519 		dev->event_handler = tick_handle_periodic_broadcast;
520 }
521 
522 #ifdef CONFIG_HOTPLUG_CPU
tick_shutdown_broadcast(void)523 static void tick_shutdown_broadcast(void)
524 {
525 	struct clock_event_device *bc = tick_broadcast_device.evtdev;
526 
527 	if (tick_broadcast_device.mode == TICKDEV_MODE_PERIODIC) {
528 		if (bc && cpumask_empty(tick_broadcast_mask))
529 			clockevents_shutdown(bc);
530 	}
531 }
532 
533 /*
534  * Remove a CPU from broadcasting
535  */
tick_broadcast_offline(unsigned int cpu)536 void tick_broadcast_offline(unsigned int cpu)
537 {
538 	raw_spin_lock(&tick_broadcast_lock);
539 	cpumask_clear_cpu(cpu, tick_broadcast_mask);
540 	cpumask_clear_cpu(cpu, tick_broadcast_on);
541 	tick_broadcast_oneshot_offline(cpu);
542 	tick_shutdown_broadcast();
543 	raw_spin_unlock(&tick_broadcast_lock);
544 }
545 
546 #endif
547 
tick_suspend_broadcast(void)548 void tick_suspend_broadcast(void)
549 {
550 	struct clock_event_device *bc;
551 	unsigned long flags;
552 
553 	raw_spin_lock_irqsave(&tick_broadcast_lock, flags);
554 
555 	bc = tick_broadcast_device.evtdev;
556 	if (bc)
557 		clockevents_shutdown(bc);
558 
559 	raw_spin_unlock_irqrestore(&tick_broadcast_lock, flags);
560 }
561 
562 /*
563  * This is called from tick_resume_local() on a resuming CPU. That's
564  * called from the core resume function, tick_unfreeze() and the magic XEN
565  * resume hackery.
566  *
567  * In none of these cases the broadcast device mode can change and the
568  * bit of the resuming CPU in the broadcast mask is safe as well.
569  */
tick_resume_check_broadcast(void)570 bool tick_resume_check_broadcast(void)
571 {
572 	if (tick_broadcast_device.mode == TICKDEV_MODE_ONESHOT)
573 		return false;
574 	else
575 		return cpumask_test_cpu(smp_processor_id(), tick_broadcast_mask);
576 }
577 
tick_resume_broadcast(void)578 void tick_resume_broadcast(void)
579 {
580 	struct clock_event_device *bc;
581 	unsigned long flags;
582 
583 	raw_spin_lock_irqsave(&tick_broadcast_lock, flags);
584 
585 	bc = tick_broadcast_device.evtdev;
586 
587 	if (bc) {
588 		clockevents_tick_resume(bc);
589 
590 		switch (tick_broadcast_device.mode) {
591 		case TICKDEV_MODE_PERIODIC:
592 			if (!cpumask_empty(tick_broadcast_mask))
593 				tick_broadcast_start_periodic(bc);
594 			break;
595 		case TICKDEV_MODE_ONESHOT:
596 			if (!cpumask_empty(tick_broadcast_mask))
597 				tick_resume_broadcast_oneshot(bc);
598 			break;
599 		}
600 	}
601 	raw_spin_unlock_irqrestore(&tick_broadcast_lock, flags);
602 }
603 
604 #ifdef CONFIG_TICK_ONESHOT
605 
606 static cpumask_var_t tick_broadcast_oneshot_mask __cpumask_var_read_mostly;
607 static cpumask_var_t tick_broadcast_pending_mask __cpumask_var_read_mostly;
608 static cpumask_var_t tick_broadcast_force_mask __cpumask_var_read_mostly;
609 
610 /*
611  * Exposed for debugging: see timer_list.c
612  */
tick_get_broadcast_oneshot_mask(void)613 struct cpumask *tick_get_broadcast_oneshot_mask(void)
614 {
615 	return tick_broadcast_oneshot_mask;
616 }
617 
618 /*
619  * Called before going idle with interrupts disabled. Checks whether a
620  * broadcast event from the other core is about to happen. We detected
621  * that in tick_broadcast_oneshot_control(). The callsite can use this
622  * to avoid a deep idle transition as we are about to get the
623  * broadcast IPI right away.
624  */
tick_check_broadcast_expired(void)625 int tick_check_broadcast_expired(void)
626 {
627 	return cpumask_test_cpu(smp_processor_id(), tick_broadcast_force_mask);
628 }
629 
630 /*
631  * Set broadcast interrupt affinity
632  */
tick_broadcast_set_affinity(struct clock_event_device * bc,const struct cpumask * cpumask)633 static void tick_broadcast_set_affinity(struct clock_event_device *bc,
634 					const struct cpumask *cpumask)
635 {
636 	if (!(bc->features & CLOCK_EVT_FEAT_DYNIRQ))
637 		return;
638 
639 	if (cpumask_equal(bc->cpumask, cpumask))
640 		return;
641 
642 	bc->cpumask = cpumask;
643 	irq_set_affinity(bc->irq, bc->cpumask);
644 }
645 
tick_broadcast_set_event(struct clock_event_device * bc,int cpu,ktime_t expires)646 static void tick_broadcast_set_event(struct clock_event_device *bc, int cpu,
647 				     ktime_t expires)
648 {
649 	if (!clockevent_state_oneshot(bc))
650 		clockevents_switch_state(bc, CLOCK_EVT_STATE_ONESHOT);
651 
652 	clockevents_program_event(bc, expires, 1);
653 	tick_broadcast_set_affinity(bc, cpumask_of(cpu));
654 }
655 
tick_resume_broadcast_oneshot(struct clock_event_device * bc)656 static void tick_resume_broadcast_oneshot(struct clock_event_device *bc)
657 {
658 	clockevents_switch_state(bc, CLOCK_EVT_STATE_ONESHOT);
659 }
660 
661 /*
662  * Called from irq_enter() when idle was interrupted to reenable the
663  * per cpu device.
664  */
tick_check_oneshot_broadcast_this_cpu(void)665 void tick_check_oneshot_broadcast_this_cpu(void)
666 {
667 	if (cpumask_test_cpu(smp_processor_id(), tick_broadcast_oneshot_mask)) {
668 		struct tick_device *td = this_cpu_ptr(&tick_cpu_device);
669 
670 		/*
671 		 * We might be in the middle of switching over from
672 		 * periodic to oneshot. If the CPU has not yet
673 		 * switched over, leave the device alone.
674 		 */
675 		if (td->mode == TICKDEV_MODE_ONESHOT) {
676 			clockevents_switch_state(td->evtdev,
677 					      CLOCK_EVT_STATE_ONESHOT);
678 		}
679 	}
680 }
681 
682 /*
683  * Handle oneshot mode broadcasting
684  */
tick_handle_oneshot_broadcast(struct clock_event_device * dev)685 static void tick_handle_oneshot_broadcast(struct clock_event_device *dev)
686 {
687 	struct tick_device *td;
688 	ktime_t now, next_event;
689 	int cpu, next_cpu = 0;
690 	bool bc_local;
691 
692 	raw_spin_lock(&tick_broadcast_lock);
693 	dev->next_event = KTIME_MAX;
694 	next_event = KTIME_MAX;
695 	cpumask_clear(tmpmask);
696 	now = ktime_get();
697 	/* Find all expired events */
698 	for_each_cpu(cpu, tick_broadcast_oneshot_mask) {
699 		/*
700 		 * Required for !SMP because for_each_cpu() reports
701 		 * unconditionally CPU0 as set on UP kernels.
702 		 */
703 		if (!IS_ENABLED(CONFIG_SMP) &&
704 		    cpumask_empty(tick_broadcast_oneshot_mask))
705 			break;
706 
707 		td = &per_cpu(tick_cpu_device, cpu);
708 		if (td->evtdev->next_event <= now) {
709 			cpumask_set_cpu(cpu, tmpmask);
710 			/*
711 			 * Mark the remote cpu in the pending mask, so
712 			 * it can avoid reprogramming the cpu local
713 			 * timer in tick_broadcast_oneshot_control().
714 			 */
715 			cpumask_set_cpu(cpu, tick_broadcast_pending_mask);
716 		} else if (td->evtdev->next_event < next_event) {
717 			next_event = td->evtdev->next_event;
718 			next_cpu = cpu;
719 		}
720 	}
721 
722 	/*
723 	 * Remove the current cpu from the pending mask. The event is
724 	 * delivered immediately in tick_do_broadcast() !
725 	 */
726 	cpumask_clear_cpu(smp_processor_id(), tick_broadcast_pending_mask);
727 
728 	/* Take care of enforced broadcast requests */
729 	cpumask_or(tmpmask, tmpmask, tick_broadcast_force_mask);
730 	cpumask_clear(tick_broadcast_force_mask);
731 
732 	/*
733 	 * Sanity check. Catch the case where we try to broadcast to
734 	 * offline cpus.
735 	 */
736 	if (WARN_ON_ONCE(!cpumask_subset(tmpmask, cpu_online_mask)))
737 		cpumask_and(tmpmask, tmpmask, cpu_online_mask);
738 
739 	/*
740 	 * Wakeup the cpus which have an expired event.
741 	 */
742 	bc_local = tick_do_broadcast(tmpmask);
743 
744 	/*
745 	 * Two reasons for reprogram:
746 	 *
747 	 * - The global event did not expire any CPU local
748 	 * events. This happens in dyntick mode, as the maximum PIT
749 	 * delta is quite small.
750 	 *
751 	 * - There are pending events on sleeping CPUs which were not
752 	 * in the event mask
753 	 */
754 	if (next_event != KTIME_MAX)
755 		tick_broadcast_set_event(dev, next_cpu, next_event);
756 
757 	raw_spin_unlock(&tick_broadcast_lock);
758 
759 	if (bc_local) {
760 		td = this_cpu_ptr(&tick_cpu_device);
761 		td->evtdev->event_handler(td->evtdev);
762 	}
763 }
764 
broadcast_needs_cpu(struct clock_event_device * bc,int cpu)765 static int broadcast_needs_cpu(struct clock_event_device *bc, int cpu)
766 {
767 	if (!(bc->features & CLOCK_EVT_FEAT_HRTIMER))
768 		return 0;
769 	if (bc->next_event == KTIME_MAX)
770 		return 0;
771 	return bc->bound_on == cpu ? -EBUSY : 0;
772 }
773 
broadcast_shutdown_local(struct clock_event_device * bc,struct clock_event_device * dev)774 static void broadcast_shutdown_local(struct clock_event_device *bc,
775 				     struct clock_event_device *dev)
776 {
777 	/*
778 	 * For hrtimer based broadcasting we cannot shutdown the cpu
779 	 * local device if our own event is the first one to expire or
780 	 * if we own the broadcast timer.
781 	 */
782 	if (bc->features & CLOCK_EVT_FEAT_HRTIMER) {
783 		if (broadcast_needs_cpu(bc, smp_processor_id()))
784 			return;
785 		if (dev->next_event < bc->next_event)
786 			return;
787 	}
788 	clockevents_switch_state(dev, CLOCK_EVT_STATE_SHUTDOWN);
789 }
790 
___tick_broadcast_oneshot_control(enum tick_broadcast_state state,struct tick_device * td,int cpu)791 static int ___tick_broadcast_oneshot_control(enum tick_broadcast_state state,
792 					     struct tick_device *td,
793 					     int cpu)
794 {
795 	struct clock_event_device *bc, *dev = td->evtdev;
796 	int ret = 0;
797 	ktime_t now;
798 
799 	raw_spin_lock(&tick_broadcast_lock);
800 	bc = tick_broadcast_device.evtdev;
801 
802 	if (state == TICK_BROADCAST_ENTER) {
803 		/*
804 		 * If the current CPU owns the hrtimer broadcast
805 		 * mechanism, it cannot go deep idle and we do not add
806 		 * the CPU to the broadcast mask. We don't have to go
807 		 * through the EXIT path as the local timer is not
808 		 * shutdown.
809 		 */
810 		ret = broadcast_needs_cpu(bc, cpu);
811 		if (ret)
812 			goto out;
813 
814 		/*
815 		 * If the broadcast device is in periodic mode, we
816 		 * return.
817 		 */
818 		if (tick_broadcast_device.mode == TICKDEV_MODE_PERIODIC) {
819 			/* If it is a hrtimer based broadcast, return busy */
820 			if (bc->features & CLOCK_EVT_FEAT_HRTIMER)
821 				ret = -EBUSY;
822 			goto out;
823 		}
824 
825 		if (!cpumask_test_and_set_cpu(cpu, tick_broadcast_oneshot_mask)) {
826 			WARN_ON_ONCE(cpumask_test_cpu(cpu, tick_broadcast_pending_mask));
827 
828 			/* Conditionally shut down the local timer. */
829 			broadcast_shutdown_local(bc, dev);
830 
831 			/*
832 			 * We only reprogram the broadcast timer if we
833 			 * did not mark ourself in the force mask and
834 			 * if the cpu local event is earlier than the
835 			 * broadcast event. If the current CPU is in
836 			 * the force mask, then we are going to be
837 			 * woken by the IPI right away; we return
838 			 * busy, so the CPU does not try to go deep
839 			 * idle.
840 			 */
841 			if (cpumask_test_cpu(cpu, tick_broadcast_force_mask)) {
842 				ret = -EBUSY;
843 			} else if (dev->next_event < bc->next_event) {
844 				tick_broadcast_set_event(bc, cpu, dev->next_event);
845 				/*
846 				 * In case of hrtimer broadcasts the
847 				 * programming might have moved the
848 				 * timer to this cpu. If yes, remove
849 				 * us from the broadcast mask and
850 				 * return busy.
851 				 */
852 				ret = broadcast_needs_cpu(bc, cpu);
853 				if (ret) {
854 					cpumask_clear_cpu(cpu,
855 						tick_broadcast_oneshot_mask);
856 				}
857 			}
858 		}
859 	} else {
860 		if (cpumask_test_and_clear_cpu(cpu, tick_broadcast_oneshot_mask)) {
861 			clockevents_switch_state(dev, CLOCK_EVT_STATE_ONESHOT);
862 			/*
863 			 * The cpu which was handling the broadcast
864 			 * timer marked this cpu in the broadcast
865 			 * pending mask and fired the broadcast
866 			 * IPI. So we are going to handle the expired
867 			 * event anyway via the broadcast IPI
868 			 * handler. No need to reprogram the timer
869 			 * with an already expired event.
870 			 */
871 			if (cpumask_test_and_clear_cpu(cpu,
872 				       tick_broadcast_pending_mask))
873 				goto out;
874 
875 			/*
876 			 * Bail out if there is no next event.
877 			 */
878 			if (dev->next_event == KTIME_MAX)
879 				goto out;
880 			/*
881 			 * If the pending bit is not set, then we are
882 			 * either the CPU handling the broadcast
883 			 * interrupt or we got woken by something else.
884 			 *
885 			 * We are no longer in the broadcast mask, so
886 			 * if the cpu local expiry time is already
887 			 * reached, we would reprogram the cpu local
888 			 * timer with an already expired event.
889 			 *
890 			 * This can lead to a ping-pong when we return
891 			 * to idle and therefore rearm the broadcast
892 			 * timer before the cpu local timer was able
893 			 * to fire. This happens because the forced
894 			 * reprogramming makes sure that the event
895 			 * will happen in the future and depending on
896 			 * the min_delta setting this might be far
897 			 * enough out that the ping-pong starts.
898 			 *
899 			 * If the cpu local next_event has expired
900 			 * then we know that the broadcast timer
901 			 * next_event has expired as well and
902 			 * broadcast is about to be handled. So we
903 			 * avoid reprogramming and enforce that the
904 			 * broadcast handler, which did not run yet,
905 			 * will invoke the cpu local handler.
906 			 *
907 			 * We cannot call the handler directly from
908 			 * here, because we might be in a NOHZ phase
909 			 * and we did not go through the irq_enter()
910 			 * nohz fixups.
911 			 */
912 			now = ktime_get();
913 			if (dev->next_event <= now) {
914 				cpumask_set_cpu(cpu, tick_broadcast_force_mask);
915 				goto out;
916 			}
917 			/*
918 			 * We got woken by something else. Reprogram
919 			 * the cpu local timer device.
920 			 */
921 			tick_program_event(dev->next_event, 1);
922 		}
923 	}
924 out:
925 	raw_spin_unlock(&tick_broadcast_lock);
926 	return ret;
927 }
928 
tick_oneshot_wakeup_control(enum tick_broadcast_state state,struct tick_device * td,int cpu)929 static int tick_oneshot_wakeup_control(enum tick_broadcast_state state,
930 				       struct tick_device *td,
931 				       int cpu)
932 {
933 	struct clock_event_device *dev, *wd;
934 
935 	dev = td->evtdev;
936 	if (td->mode != TICKDEV_MODE_ONESHOT)
937 		return -EINVAL;
938 
939 	wd = tick_get_oneshot_wakeup_device(cpu);
940 	if (!wd)
941 		return -ENODEV;
942 
943 	switch (state) {
944 	case TICK_BROADCAST_ENTER:
945 		clockevents_switch_state(dev, CLOCK_EVT_STATE_ONESHOT_STOPPED);
946 		clockevents_switch_state(wd, CLOCK_EVT_STATE_ONESHOT);
947 		clockevents_program_event(wd, dev->next_event, 1);
948 		break;
949 	case TICK_BROADCAST_EXIT:
950 		/* We may have transitioned to oneshot mode while idle */
951 		if (clockevent_get_state(wd) != CLOCK_EVT_STATE_ONESHOT)
952 			return -ENODEV;
953 	}
954 
955 	return 0;
956 }
957 
__tick_broadcast_oneshot_control(enum tick_broadcast_state state)958 int __tick_broadcast_oneshot_control(enum tick_broadcast_state state)
959 {
960 	struct tick_device *td = this_cpu_ptr(&tick_cpu_device);
961 	int cpu = smp_processor_id();
962 
963 	if (!tick_oneshot_wakeup_control(state, td, cpu))
964 		return 0;
965 
966 	if (tick_broadcast_device.evtdev)
967 		return ___tick_broadcast_oneshot_control(state, td, cpu);
968 
969 	/*
970 	 * If there is no broadcast or wakeup device, tell the caller not
971 	 * to go into deep idle.
972 	 */
973 	return -EBUSY;
974 }
975 
976 /*
977  * Reset the one shot broadcast for a cpu
978  *
979  * Called with tick_broadcast_lock held
980  */
tick_broadcast_clear_oneshot(int cpu)981 static void tick_broadcast_clear_oneshot(int cpu)
982 {
983 	cpumask_clear_cpu(cpu, tick_broadcast_oneshot_mask);
984 	cpumask_clear_cpu(cpu, tick_broadcast_pending_mask);
985 }
986 
tick_broadcast_init_next_event(struct cpumask * mask,ktime_t expires)987 static void tick_broadcast_init_next_event(struct cpumask *mask,
988 					   ktime_t expires)
989 {
990 	struct tick_device *td;
991 	int cpu;
992 
993 	for_each_cpu(cpu, mask) {
994 		td = &per_cpu(tick_cpu_device, cpu);
995 		if (td->evtdev)
996 			td->evtdev->next_event = expires;
997 	}
998 }
999 
tick_get_next_period(void)1000 static inline ktime_t tick_get_next_period(void)
1001 {
1002 	ktime_t next;
1003 
1004 	/*
1005 	 * Protect against concurrent updates (store /load tearing on
1006 	 * 32bit). It does not matter if the time is already in the
1007 	 * past. The broadcast device which is about to be programmed will
1008 	 * fire in any case.
1009 	 */
1010 	raw_spin_lock(&jiffies_lock);
1011 	next = tick_next_period;
1012 	raw_spin_unlock(&jiffies_lock);
1013 	return next;
1014 }
1015 
1016 /**
1017  * tick_broadcast_setup_oneshot - setup the broadcast device
1018  */
tick_broadcast_setup_oneshot(struct clock_event_device * bc)1019 static void tick_broadcast_setup_oneshot(struct clock_event_device *bc)
1020 {
1021 	int cpu = smp_processor_id();
1022 
1023 	if (!bc)
1024 		return;
1025 
1026 	/* Set it up only once ! */
1027 	if (bc->event_handler != tick_handle_oneshot_broadcast) {
1028 		int was_periodic = clockevent_state_periodic(bc);
1029 
1030 		bc->event_handler = tick_handle_oneshot_broadcast;
1031 
1032 		/*
1033 		 * We must be careful here. There might be other CPUs
1034 		 * waiting for periodic broadcast. We need to set the
1035 		 * oneshot_mask bits for those and program the
1036 		 * broadcast device to fire.
1037 		 */
1038 		cpumask_copy(tmpmask, tick_broadcast_mask);
1039 		cpumask_clear_cpu(cpu, tmpmask);
1040 		cpumask_or(tick_broadcast_oneshot_mask,
1041 			   tick_broadcast_oneshot_mask, tmpmask);
1042 
1043 		if (was_periodic && !cpumask_empty(tmpmask)) {
1044 			ktime_t nextevt = tick_get_next_period();
1045 
1046 			clockevents_switch_state(bc, CLOCK_EVT_STATE_ONESHOT);
1047 			tick_broadcast_init_next_event(tmpmask, nextevt);
1048 			tick_broadcast_set_event(bc, cpu, nextevt);
1049 		} else
1050 			bc->next_event = KTIME_MAX;
1051 	} else {
1052 		/*
1053 		 * The first cpu which switches to oneshot mode sets
1054 		 * the bit for all other cpus which are in the general
1055 		 * (periodic) broadcast mask. So the bit is set and
1056 		 * would prevent the first broadcast enter after this
1057 		 * to program the bc device.
1058 		 */
1059 		tick_broadcast_clear_oneshot(cpu);
1060 	}
1061 }
1062 
1063 /*
1064  * Select oneshot operating mode for the broadcast device
1065  */
tick_broadcast_switch_to_oneshot(void)1066 void tick_broadcast_switch_to_oneshot(void)
1067 {
1068 	struct clock_event_device *bc;
1069 	unsigned long flags;
1070 
1071 	raw_spin_lock_irqsave(&tick_broadcast_lock, flags);
1072 
1073 	tick_broadcast_device.mode = TICKDEV_MODE_ONESHOT;
1074 	bc = tick_broadcast_device.evtdev;
1075 	if (bc)
1076 		tick_broadcast_setup_oneshot(bc);
1077 
1078 	raw_spin_unlock_irqrestore(&tick_broadcast_lock, flags);
1079 }
1080 
1081 #ifdef CONFIG_HOTPLUG_CPU
hotplug_cpu__broadcast_tick_pull(int deadcpu)1082 void hotplug_cpu__broadcast_tick_pull(int deadcpu)
1083 {
1084 	struct clock_event_device *bc;
1085 	unsigned long flags;
1086 
1087 	raw_spin_lock_irqsave(&tick_broadcast_lock, flags);
1088 	bc = tick_broadcast_device.evtdev;
1089 
1090 	if (bc && broadcast_needs_cpu(bc, deadcpu)) {
1091 		/* This moves the broadcast assignment to this CPU: */
1092 		clockevents_program_event(bc, bc->next_event, 1);
1093 	}
1094 	raw_spin_unlock_irqrestore(&tick_broadcast_lock, flags);
1095 }
1096 
1097 /*
1098  * Remove a dying CPU from broadcasting
1099  */
tick_broadcast_oneshot_offline(unsigned int cpu)1100 static void tick_broadcast_oneshot_offline(unsigned int cpu)
1101 {
1102 	if (tick_get_oneshot_wakeup_device(cpu))
1103 		tick_set_oneshot_wakeup_device(NULL, cpu);
1104 
1105 	/*
1106 	 * Clear the broadcast masks for the dead cpu, but do not stop
1107 	 * the broadcast device!
1108 	 */
1109 	cpumask_clear_cpu(cpu, tick_broadcast_oneshot_mask);
1110 	cpumask_clear_cpu(cpu, tick_broadcast_pending_mask);
1111 	cpumask_clear_cpu(cpu, tick_broadcast_force_mask);
1112 }
1113 #endif
1114 
1115 /*
1116  * Check, whether the broadcast device is in one shot mode
1117  */
tick_broadcast_oneshot_active(void)1118 int tick_broadcast_oneshot_active(void)
1119 {
1120 	return tick_broadcast_device.mode == TICKDEV_MODE_ONESHOT;
1121 }
1122 
1123 /*
1124  * Check whether the broadcast device supports oneshot.
1125  */
tick_broadcast_oneshot_available(void)1126 bool tick_broadcast_oneshot_available(void)
1127 {
1128 	struct clock_event_device *bc = tick_broadcast_device.evtdev;
1129 
1130 	return bc ? bc->features & CLOCK_EVT_FEAT_ONESHOT : false;
1131 }
1132 
1133 #else
__tick_broadcast_oneshot_control(enum tick_broadcast_state state)1134 int __tick_broadcast_oneshot_control(enum tick_broadcast_state state)
1135 {
1136 	struct clock_event_device *bc = tick_broadcast_device.evtdev;
1137 
1138 	if (!bc || (bc->features & CLOCK_EVT_FEAT_HRTIMER))
1139 		return -EBUSY;
1140 
1141 	return 0;
1142 }
1143 #endif
1144 
tick_broadcast_init(void)1145 void __init tick_broadcast_init(void)
1146 {
1147 	zalloc_cpumask_var(&tick_broadcast_mask, GFP_NOWAIT);
1148 	zalloc_cpumask_var(&tick_broadcast_on, GFP_NOWAIT);
1149 	zalloc_cpumask_var(&tmpmask, GFP_NOWAIT);
1150 #ifdef CONFIG_TICK_ONESHOT
1151 	zalloc_cpumask_var(&tick_broadcast_oneshot_mask, GFP_NOWAIT);
1152 	zalloc_cpumask_var(&tick_broadcast_pending_mask, GFP_NOWAIT);
1153 	zalloc_cpumask_var(&tick_broadcast_force_mask, GFP_NOWAIT);
1154 #endif
1155 }
1156