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1// SPDX-License-Identifier: GPL-2.0
2/*
3 * This file contains the base functions to manage periodic tick
4 * related events.
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/nmi.h>
15#include <linux/percpu.h>
16#include <linux/profile.h>
17#include <linux/sched.h>
18#include <linux/module.h>
19#include <trace/events/power.h>
20
21#include <asm/irq_regs.h>
22
23#include "tick-internal.h"
24
25/*
26 * Tick devices
27 */
28DEFINE_PER_CPU(struct tick_device, tick_cpu_device);
29/*
30 * Tick next event: keeps track of the tick time. It's updated by the
31 * CPU which handles the tick and protected by jiffies_lock. There is
32 * no requirement to write hold the jiffies seqcount for it.
33 */
34ktime_t tick_next_period;
35
36/*
37 * tick_do_timer_cpu is a timer core internal variable which holds the CPU NR
38 * which is responsible for calling do_timer(), i.e. the timekeeping stuff. This
39 * variable has two functions:
40 *
41 * 1) Prevent a thundering herd issue of a gazillion of CPUs trying to grab the
42 * timekeeping lock all at once. Only the CPU which is assigned to do the
43 * update is handling it.
44 *
45 * 2) Hand off the duty in the NOHZ idle case by setting the value to
46 * TICK_DO_TIMER_NONE, i.e. a non existing CPU. So the next cpu which looks
47 * at it will take over and keep the time keeping alive. The handover
48 * procedure also covers cpu hotplug.
49 */
50int tick_do_timer_cpu __read_mostly = TICK_DO_TIMER_BOOT;
51#ifdef CONFIG_NO_HZ_FULL
52/*
53 * tick_do_timer_boot_cpu indicates the boot CPU temporarily owns
54 * tick_do_timer_cpu and it should be taken over by an eligible secondary
55 * when one comes online.
56 */
57static int tick_do_timer_boot_cpu __read_mostly = -1;
58#endif
59
60/*
61 * Debugging: see timer_list.c
62 */
63struct tick_device *tick_get_device(int cpu)
64{
65 return &per_cpu(tick_cpu_device, cpu);
66}
67
68/**
69 * tick_is_oneshot_available - check for a oneshot capable event device
70 */
71int tick_is_oneshot_available(void)
72{
73 struct clock_event_device *dev = __this_cpu_read(tick_cpu_device.evtdev);
74
75 if (!dev || !(dev->features & CLOCK_EVT_FEAT_ONESHOT))
76 return 0;
77 if (!(dev->features & CLOCK_EVT_FEAT_C3STOP))
78 return 1;
79 return tick_broadcast_oneshot_available();
80}
81
82/*
83 * Periodic tick
84 */
85static void tick_periodic(int cpu)
86{
87 if (tick_do_timer_cpu == cpu) {
88 raw_spin_lock(&jiffies_lock);
89 write_seqcount_begin(&jiffies_seq);
90
91 /* Keep track of the next tick event */
92 tick_next_period = ktime_add_ns(tick_next_period, TICK_NSEC);
93
94 do_timer(1);
95 write_seqcount_end(&jiffies_seq);
96 raw_spin_unlock(&jiffies_lock);
97 update_wall_time();
98 }
99
100 update_process_times(user_mode(get_irq_regs()));
101 profile_tick(CPU_PROFILING);
102}
103
104/*
105 * Event handler for periodic ticks
106 */
107void tick_handle_periodic(struct clock_event_device *dev)
108{
109 int cpu = smp_processor_id();
110 ktime_t next = dev->next_event;
111
112 tick_periodic(cpu);
113
114#if defined(CONFIG_HIGH_RES_TIMERS) || defined(CONFIG_NO_HZ_COMMON)
115 /*
116 * The cpu might have transitioned to HIGHRES or NOHZ mode via
117 * update_process_times() -> run_local_timers() ->
118 * hrtimer_run_queues().
119 */
120 if (dev->event_handler != tick_handle_periodic)
121 return;
122#endif
123
124 if (!clockevent_state_oneshot(dev))
125 return;
126 for (;;) {
127 /*
128 * Setup the next period for devices, which do not have
129 * periodic mode:
130 */
131 next = ktime_add_ns(next, TICK_NSEC);
132
133 if (!clockevents_program_event(dev, next, false))
134 return;
135 /*
136 * Have to be careful here. If we're in oneshot mode,
137 * before we call tick_periodic() in a loop, we need
138 * to be sure we're using a real hardware clocksource.
139 * Otherwise we could get trapped in an infinite
140 * loop, as the tick_periodic() increments jiffies,
141 * which then will increment time, possibly causing
142 * the loop to trigger again and again.
143 */
144 if (timekeeping_valid_for_hres())
145 tick_periodic(cpu);
146 }
147}
148
149/*
150 * Setup the device for a periodic tick
151 */
152void tick_setup_periodic(struct clock_event_device *dev, int broadcast)
153{
154 tick_set_periodic_handler(dev, broadcast);
155
156 /* Broadcast setup ? */
157 if (!tick_device_is_functional(dev))
158 return;
159
160 if ((dev->features & CLOCK_EVT_FEAT_PERIODIC) &&
161 !tick_broadcast_oneshot_active()) {
162 clockevents_switch_state(dev, CLOCK_EVT_STATE_PERIODIC);
163 } else {
164 unsigned int seq;
165 ktime_t next;
166
167 do {
168 seq = read_seqcount_begin(&jiffies_seq);
169 next = tick_next_period;
170 } while (read_seqcount_retry(&jiffies_seq, seq));
171
172 clockevents_switch_state(dev, CLOCK_EVT_STATE_ONESHOT);
173
174 for (;;) {
175 if (!clockevents_program_event(dev, next, false))
176 return;
177 next = ktime_add_ns(next, TICK_NSEC);
178 }
179 }
180}
181
182#ifdef CONFIG_NO_HZ_FULL
183static void giveup_do_timer(void *info)
184{
185 int cpu = *(unsigned int *)info;
186
187 WARN_ON(tick_do_timer_cpu != smp_processor_id());
188
189 tick_do_timer_cpu = cpu;
190}
191
192static void tick_take_do_timer_from_boot(void)
193{
194 int cpu = smp_processor_id();
195 int from = tick_do_timer_boot_cpu;
196
197 if (from >= 0 && from != cpu)
198 smp_call_function_single(from, giveup_do_timer, &cpu, 1);
199}
200#endif
201
202/*
203 * Setup the tick device
204 */
205static void tick_setup_device(struct tick_device *td,
206 struct clock_event_device *newdev, int cpu,
207 const struct cpumask *cpumask)
208{
209 void (*handler)(struct clock_event_device *) = NULL;
210 ktime_t next_event = 0;
211
212 /*
213 * First device setup ?
214 */
215 if (!td->evtdev) {
216 /*
217 * If no cpu took the do_timer update, assign it to
218 * this cpu:
219 */
220 if (tick_do_timer_cpu == TICK_DO_TIMER_BOOT) {
221 tick_do_timer_cpu = cpu;
222
223 tick_next_period = ktime_get();
224#ifdef CONFIG_NO_HZ_FULL
225 /*
226 * The boot CPU may be nohz_full, in which case set
227 * tick_do_timer_boot_cpu so the first housekeeping
228 * secondary that comes up will take do_timer from
229 * us.
230 */
231 if (tick_nohz_full_cpu(cpu))
232 tick_do_timer_boot_cpu = cpu;
233
234 } else if (tick_do_timer_boot_cpu != -1 &&
235 !tick_nohz_full_cpu(cpu)) {
236 tick_take_do_timer_from_boot();
237 tick_do_timer_boot_cpu = -1;
238 WARN_ON(tick_do_timer_cpu != cpu);
239#endif
240 }
241
242 /*
243 * Startup in periodic mode first.
244 */
245 td->mode = TICKDEV_MODE_PERIODIC;
246 } else {
247 handler = td->evtdev->event_handler;
248 next_event = td->evtdev->next_event;
249 td->evtdev->event_handler = clockevents_handle_noop;
250 }
251
252 td->evtdev = newdev;
253
254 /*
255 * When the device is not per cpu, pin the interrupt to the
256 * current cpu:
257 */
258 if (!cpumask_equal(newdev->cpumask, cpumask))
259 irq_set_affinity(newdev->irq, cpumask);
260
261 /*
262 * When global broadcasting is active, check if the current
263 * device is registered as a placeholder for broadcast mode.
264 * This allows us to handle this x86 misfeature in a generic
265 * way. This function also returns !=0 when we keep the
266 * current active broadcast state for this CPU.
267 */
268 if (tick_device_uses_broadcast(newdev, cpu))
269 return;
270
271 if (td->mode == TICKDEV_MODE_PERIODIC)
272 tick_setup_periodic(newdev, 0);
273 else
274 tick_setup_oneshot(newdev, handler, next_event);
275}
276
277void tick_install_replacement(struct clock_event_device *newdev)
278{
279 struct tick_device *td = this_cpu_ptr(&tick_cpu_device);
280 int cpu = smp_processor_id();
281
282 clockevents_exchange_device(td->evtdev, newdev);
283 tick_setup_device(td, newdev, cpu, cpumask_of(cpu));
284 if (newdev->features & CLOCK_EVT_FEAT_ONESHOT)
285 tick_oneshot_notify();
286}
287
288static bool tick_check_percpu(struct clock_event_device *curdev,
289 struct clock_event_device *newdev, int cpu)
290{
291 if (!cpumask_test_cpu(cpu, newdev->cpumask))
292 return false;
293 if (cpumask_equal(newdev->cpumask, cpumask_of(cpu)))
294 return true;
295 /* Check if irq affinity can be set */
296 if (newdev->irq >= 0 && !irq_can_set_affinity(newdev->irq))
297 return false;
298 /* Prefer an existing cpu local device */
299 if (curdev && cpumask_equal(curdev->cpumask, cpumask_of(cpu)))
300 return false;
301 return true;
302}
303
304static bool tick_check_preferred(struct clock_event_device *curdev,
305 struct clock_event_device *newdev)
306{
307 /* Prefer oneshot capable device */
308 if (!(newdev->features & CLOCK_EVT_FEAT_ONESHOT)) {
309 if (curdev && (curdev->features & CLOCK_EVT_FEAT_ONESHOT))
310 return false;
311 if (tick_oneshot_mode_active())
312 return false;
313 }
314
315 /*
316 * Use the higher rated one, but prefer a CPU local device with a lower
317 * rating than a non-CPU local device
318 */
319 return !curdev ||
320 newdev->rating > curdev->rating ||
321 !cpumask_equal(curdev->cpumask, newdev->cpumask);
322}
323
324/*
325 * Check whether the new device is a better fit than curdev. curdev
326 * can be NULL !
327 */
328bool tick_check_replacement(struct clock_event_device *curdev,
329 struct clock_event_device *newdev)
330{
331 if (!tick_check_percpu(curdev, newdev, smp_processor_id()))
332 return false;
333
334 return tick_check_preferred(curdev, newdev);
335}
336
337/*
338 * Check, if the new registered device should be used. Called with
339 * clockevents_lock held and interrupts disabled.
340 */
341void tick_check_new_device(struct clock_event_device *newdev)
342{
343 struct clock_event_device *curdev;
344 struct tick_device *td;
345 int cpu;
346
347 cpu = smp_processor_id();
348 td = &per_cpu(tick_cpu_device, cpu);
349 curdev = td->evtdev;
350
351 if (!tick_check_replacement(curdev, newdev))
352 goto out_bc;
353
354 if (!try_module_get(newdev->owner))
355 return;
356
357 /*
358 * Replace the eventually existing device by the new
359 * device. If the current device is the broadcast device, do
360 * not give it back to the clockevents layer !
361 */
362 if (tick_is_broadcast_device(curdev)) {
363 clockevents_shutdown(curdev);
364 curdev = NULL;
365 }
366 clockevents_exchange_device(curdev, newdev);
367 tick_setup_device(td, newdev, cpu, cpumask_of(cpu));
368 if (newdev->features & CLOCK_EVT_FEAT_ONESHOT)
369 tick_oneshot_notify();
370 return;
371
372out_bc:
373 /*
374 * Can the new device be used as a broadcast device ?
375 */
376 tick_install_broadcast_device(newdev, cpu);
377}
378
379/**
380 * tick_broadcast_oneshot_control - Enter/exit broadcast oneshot mode
381 * @state: The target state (enter/exit)
382 *
383 * The system enters/leaves a state, where affected devices might stop
384 * Returns 0 on success, -EBUSY if the cpu is used to broadcast wakeups.
385 *
386 * Called with interrupts disabled, so clockevents_lock is not
387 * required here because the local clock event device cannot go away
388 * under us.
389 */
390int tick_broadcast_oneshot_control(enum tick_broadcast_state state)
391{
392 struct tick_device *td = this_cpu_ptr(&tick_cpu_device);
393
394 if (!(td->evtdev->features & CLOCK_EVT_FEAT_C3STOP))
395 return 0;
396
397 return __tick_broadcast_oneshot_control(state);
398}
399EXPORT_SYMBOL_GPL(tick_broadcast_oneshot_control);
400
401#ifdef CONFIG_HOTPLUG_CPU
402/*
403 * Transfer the do_timer job away from a dying cpu.
404 *
405 * Called with interrupts disabled. No locking required. If
406 * tick_do_timer_cpu is owned by this cpu, nothing can change it.
407 */
408void tick_handover_do_timer(void)
409{
410 if (tick_do_timer_cpu == smp_processor_id())
411 tick_do_timer_cpu = cpumask_first(cpu_online_mask);
412}
413
414/*
415 * Shutdown an event device on a given cpu:
416 *
417 * This is called on a life CPU, when a CPU is dead. So we cannot
418 * access the hardware device itself.
419 * We just set the mode and remove it from the lists.
420 */
421void tick_shutdown(unsigned int cpu)
422{
423 struct tick_device *td = &per_cpu(tick_cpu_device, cpu);
424 struct clock_event_device *dev = td->evtdev;
425
426 td->mode = TICKDEV_MODE_PERIODIC;
427 if (dev) {
428 /*
429 * Prevent that the clock events layer tries to call
430 * the set mode function!
431 */
432 clockevent_set_state(dev, CLOCK_EVT_STATE_DETACHED);
433 clockevents_exchange_device(dev, NULL);
434 dev->event_handler = clockevents_handle_noop;
435 td->evtdev = NULL;
436 }
437}
438#endif
439
440/**
441 * tick_suspend_local - Suspend the local tick device
442 *
443 * Called from the local cpu for freeze with interrupts disabled.
444 *
445 * No locks required. Nothing can change the per cpu device.
446 */
447void tick_suspend_local(void)
448{
449 struct tick_device *td = this_cpu_ptr(&tick_cpu_device);
450
451 clockevents_shutdown(td->evtdev);
452}
453
454/**
455 * tick_resume_local - Resume the local tick device
456 *
457 * Called from the local CPU for unfreeze or XEN resume magic.
458 *
459 * No locks required. Nothing can change the per cpu device.
460 */
461void tick_resume_local(void)
462{
463 struct tick_device *td = this_cpu_ptr(&tick_cpu_device);
464 bool broadcast = tick_resume_check_broadcast();
465
466 clockevents_tick_resume(td->evtdev);
467 if (!broadcast) {
468 if (td->mode == TICKDEV_MODE_PERIODIC)
469 tick_setup_periodic(td->evtdev, 0);
470 else
471 tick_resume_oneshot();
472 }
473
474 /*
475 * Ensure that hrtimers are up to date and the clockevents device
476 * is reprogrammed correctly when high resolution timers are
477 * enabled.
478 */
479 hrtimers_resume_local();
480}
481
482/**
483 * tick_suspend - Suspend the tick and the broadcast device
484 *
485 * Called from syscore_suspend() via timekeeping_suspend with only one
486 * CPU online and interrupts disabled or from tick_unfreeze() under
487 * tick_freeze_lock.
488 *
489 * No locks required. Nothing can change the per cpu device.
490 */
491void tick_suspend(void)
492{
493 tick_suspend_local();
494 tick_suspend_broadcast();
495}
496
497/**
498 * tick_resume - Resume the tick and the broadcast device
499 *
500 * Called from syscore_resume() via timekeeping_resume with only one
501 * CPU online and interrupts disabled.
502 *
503 * No locks required. Nothing can change the per cpu device.
504 */
505void tick_resume(void)
506{
507 tick_resume_broadcast();
508 tick_resume_local();
509}
510
511#ifdef CONFIG_SUSPEND
512static DEFINE_RAW_SPINLOCK(tick_freeze_lock);
513static unsigned int tick_freeze_depth;
514
515/**
516 * tick_freeze - Suspend the local tick and (possibly) timekeeping.
517 *
518 * Check if this is the last online CPU executing the function and if so,
519 * suspend timekeeping. Otherwise suspend the local tick.
520 *
521 * Call with interrupts disabled. Must be balanced with %tick_unfreeze().
522 * Interrupts must not be enabled before the subsequent %tick_unfreeze().
523 */
524void tick_freeze(void)
525{
526 raw_spin_lock(&tick_freeze_lock);
527
528 tick_freeze_depth++;
529 if (tick_freeze_depth == num_online_cpus()) {
530 trace_suspend_resume(TPS("timekeeping_freeze"),
531 smp_processor_id(), true);
532 system_state = SYSTEM_SUSPEND;
533 sched_clock_suspend();
534 timekeeping_suspend();
535 } else {
536 tick_suspend_local();
537 }
538
539 raw_spin_unlock(&tick_freeze_lock);
540}
541
542/**
543 * tick_unfreeze - Resume the local tick and (possibly) timekeeping.
544 *
545 * Check if this is the first CPU executing the function and if so, resume
546 * timekeeping. Otherwise resume the local tick.
547 *
548 * Call with interrupts disabled. Must be balanced with %tick_freeze().
549 * Interrupts must not be enabled after the preceding %tick_freeze().
550 */
551void tick_unfreeze(void)
552{
553 raw_spin_lock(&tick_freeze_lock);
554
555 if (tick_freeze_depth == num_online_cpus()) {
556 timekeeping_resume();
557 sched_clock_resume();
558 system_state = SYSTEM_RUNNING;
559 trace_suspend_resume(TPS("timekeeping_freeze"),
560 smp_processor_id(), false);
561 } else {
562 touch_softlockup_watchdog();
563 tick_resume_local();
564 }
565
566 tick_freeze_depth--;
567
568 raw_spin_unlock(&tick_freeze_lock);
569}
570#endif /* CONFIG_SUSPEND */
571
572/**
573 * tick_init - initialize the tick control
574 */
575void __init tick_init(void)
576{
577 tick_broadcast_init();
578 tick_nohz_init();
579}
1// SPDX-License-Identifier: GPL-2.0
2/*
3 * This file contains the base functions to manage periodic tick
4 * related events.
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/nmi.h>
15#include <linux/percpu.h>
16#include <linux/profile.h>
17#include <linux/sched.h>
18#include <linux/module.h>
19#include <trace/events/power.h>
20
21#include <asm/irq_regs.h>
22
23#include "tick-internal.h"
24
25/*
26 * Tick devices
27 */
28DEFINE_PER_CPU(struct tick_device, tick_cpu_device);
29/*
30 * Tick next event: keeps track of the tick time. It's updated by the
31 * CPU which handles the tick and protected by jiffies_lock. There is
32 * no requirement to write hold the jiffies seqcount for it.
33 */
34ktime_t tick_next_period;
35
36/*
37 * tick_do_timer_cpu is a timer core internal variable which holds the CPU NR
38 * which is responsible for calling do_timer(), i.e. the timekeeping stuff. This
39 * variable has two functions:
40 *
41 * 1) Prevent a thundering herd issue of a gazillion of CPUs trying to grab the
42 * timekeeping lock all at once. Only the CPU which is assigned to do the
43 * update is handling it.
44 *
45 * 2) Hand off the duty in the NOHZ idle case by setting the value to
46 * TICK_DO_TIMER_NONE, i.e. a non existing CPU. So the next cpu which looks
47 * at it will take over and keep the time keeping alive. The handover
48 * procedure also covers cpu hotplug.
49 */
50int tick_do_timer_cpu __read_mostly = TICK_DO_TIMER_BOOT;
51#ifdef CONFIG_NO_HZ_FULL
52/*
53 * tick_do_timer_boot_cpu indicates the boot CPU temporarily owns
54 * tick_do_timer_cpu and it should be taken over by an eligible secondary
55 * when one comes online.
56 */
57static int tick_do_timer_boot_cpu __read_mostly = -1;
58#endif
59
60/*
61 * Debugging: see timer_list.c
62 */
63struct tick_device *tick_get_device(int cpu)
64{
65 return &per_cpu(tick_cpu_device, cpu);
66}
67
68/**
69 * tick_is_oneshot_available - check for a oneshot capable event device
70 */
71int tick_is_oneshot_available(void)
72{
73 struct clock_event_device *dev = __this_cpu_read(tick_cpu_device.evtdev);
74
75 if (!dev || !(dev->features & CLOCK_EVT_FEAT_ONESHOT))
76 return 0;
77 if (!(dev->features & CLOCK_EVT_FEAT_C3STOP))
78 return 1;
79 return tick_broadcast_oneshot_available();
80}
81
82/*
83 * Periodic tick
84 */
85static void tick_periodic(int cpu)
86{
87 if (tick_do_timer_cpu == cpu) {
88 raw_spin_lock(&jiffies_lock);
89 write_seqcount_begin(&jiffies_seq);
90
91 /* Keep track of the next tick event */
92 tick_next_period = ktime_add_ns(tick_next_period, TICK_NSEC);
93
94 do_timer(1);
95 write_seqcount_end(&jiffies_seq);
96 raw_spin_unlock(&jiffies_lock);
97 update_wall_time();
98 }
99
100 update_process_times(user_mode(get_irq_regs()));
101 profile_tick(CPU_PROFILING);
102}
103
104/*
105 * Event handler for periodic ticks
106 */
107void tick_handle_periodic(struct clock_event_device *dev)
108{
109 int cpu = smp_processor_id();
110 ktime_t next = dev->next_event;
111
112 tick_periodic(cpu);
113
114#if defined(CONFIG_HIGH_RES_TIMERS) || defined(CONFIG_NO_HZ_COMMON)
115 /*
116 * The cpu might have transitioned to HIGHRES or NOHZ mode via
117 * update_process_times() -> run_local_timers() ->
118 * hrtimer_run_queues().
119 */
120 if (dev->event_handler != tick_handle_periodic)
121 return;
122#endif
123
124 if (!clockevent_state_oneshot(dev))
125 return;
126 for (;;) {
127 /*
128 * Setup the next period for devices, which do not have
129 * periodic mode:
130 */
131 next = ktime_add_ns(next, TICK_NSEC);
132
133 if (!clockevents_program_event(dev, next, false))
134 return;
135 /*
136 * Have to be careful here. If we're in oneshot mode,
137 * before we call tick_periodic() in a loop, we need
138 * to be sure we're using a real hardware clocksource.
139 * Otherwise we could get trapped in an infinite
140 * loop, as the tick_periodic() increments jiffies,
141 * which then will increment time, possibly causing
142 * the loop to trigger again and again.
143 */
144 if (timekeeping_valid_for_hres())
145 tick_periodic(cpu);
146 }
147}
148
149/*
150 * Setup the device for a periodic tick
151 */
152void tick_setup_periodic(struct clock_event_device *dev, int broadcast)
153{
154 tick_set_periodic_handler(dev, broadcast);
155
156 /* Broadcast setup ? */
157 if (!tick_device_is_functional(dev))
158 return;
159
160 if ((dev->features & CLOCK_EVT_FEAT_PERIODIC) &&
161 !tick_broadcast_oneshot_active()) {
162 clockevents_switch_state(dev, CLOCK_EVT_STATE_PERIODIC);
163 } else {
164 unsigned int seq;
165 ktime_t next;
166
167 do {
168 seq = read_seqcount_begin(&jiffies_seq);
169 next = tick_next_period;
170 } while (read_seqcount_retry(&jiffies_seq, seq));
171
172 clockevents_switch_state(dev, CLOCK_EVT_STATE_ONESHOT);
173
174 for (;;) {
175 if (!clockevents_program_event(dev, next, false))
176 return;
177 next = ktime_add_ns(next, TICK_NSEC);
178 }
179 }
180}
181
182#ifdef CONFIG_NO_HZ_FULL
183static void giveup_do_timer(void *info)
184{
185 int cpu = *(unsigned int *)info;
186
187 WARN_ON(tick_do_timer_cpu != smp_processor_id());
188
189 tick_do_timer_cpu = cpu;
190}
191
192static void tick_take_do_timer_from_boot(void)
193{
194 int cpu = smp_processor_id();
195 int from = tick_do_timer_boot_cpu;
196
197 if (from >= 0 && from != cpu)
198 smp_call_function_single(from, giveup_do_timer, &cpu, 1);
199}
200#endif
201
202/*
203 * Setup the tick device
204 */
205static void tick_setup_device(struct tick_device *td,
206 struct clock_event_device *newdev, int cpu,
207 const struct cpumask *cpumask)
208{
209 void (*handler)(struct clock_event_device *) = NULL;
210 ktime_t next_event = 0;
211
212 /*
213 * First device setup ?
214 */
215 if (!td->evtdev) {
216 /*
217 * If no cpu took the do_timer update, assign it to
218 * this cpu:
219 */
220 if (tick_do_timer_cpu == TICK_DO_TIMER_BOOT) {
221 tick_do_timer_cpu = cpu;
222
223 tick_next_period = ktime_get();
224#ifdef CONFIG_NO_HZ_FULL
225 /*
226 * The boot CPU may be nohz_full, in which case set
227 * tick_do_timer_boot_cpu so the first housekeeping
228 * secondary that comes up will take do_timer from
229 * us.
230 */
231 if (tick_nohz_full_cpu(cpu))
232 tick_do_timer_boot_cpu = cpu;
233
234 } else if (tick_do_timer_boot_cpu != -1 &&
235 !tick_nohz_full_cpu(cpu)) {
236 tick_take_do_timer_from_boot();
237 tick_do_timer_boot_cpu = -1;
238 WARN_ON(tick_do_timer_cpu != cpu);
239#endif
240 }
241
242 /*
243 * Startup in periodic mode first.
244 */
245 td->mode = TICKDEV_MODE_PERIODIC;
246 } else {
247 handler = td->evtdev->event_handler;
248 next_event = td->evtdev->next_event;
249 td->evtdev->event_handler = clockevents_handle_noop;
250 }
251
252 td->evtdev = newdev;
253
254 /*
255 * When the device is not per cpu, pin the interrupt to the
256 * current cpu:
257 */
258 if (!cpumask_equal(newdev->cpumask, cpumask))
259 irq_set_affinity(newdev->irq, cpumask);
260
261 /*
262 * When global broadcasting is active, check if the current
263 * device is registered as a placeholder for broadcast mode.
264 * This allows us to handle this x86 misfeature in a generic
265 * way. This function also returns !=0 when we keep the
266 * current active broadcast state for this CPU.
267 */
268 if (tick_device_uses_broadcast(newdev, cpu))
269 return;
270
271 if (td->mode == TICKDEV_MODE_PERIODIC)
272 tick_setup_periodic(newdev, 0);
273 else
274 tick_setup_oneshot(newdev, handler, next_event);
275}
276
277void tick_install_replacement(struct clock_event_device *newdev)
278{
279 struct tick_device *td = this_cpu_ptr(&tick_cpu_device);
280 int cpu = smp_processor_id();
281
282 clockevents_exchange_device(td->evtdev, newdev);
283 tick_setup_device(td, newdev, cpu, cpumask_of(cpu));
284 if (newdev->features & CLOCK_EVT_FEAT_ONESHOT)
285 tick_oneshot_notify();
286}
287
288static bool tick_check_percpu(struct clock_event_device *curdev,
289 struct clock_event_device *newdev, int cpu)
290{
291 if (!cpumask_test_cpu(cpu, newdev->cpumask))
292 return false;
293 if (cpumask_equal(newdev->cpumask, cpumask_of(cpu)))
294 return true;
295 /* Check if irq affinity can be set */
296 if (newdev->irq >= 0 && !irq_can_set_affinity(newdev->irq))
297 return false;
298 /* Prefer an existing cpu local device */
299 if (curdev && cpumask_equal(curdev->cpumask, cpumask_of(cpu)))
300 return false;
301 return true;
302}
303
304static bool tick_check_preferred(struct clock_event_device *curdev,
305 struct clock_event_device *newdev)
306{
307 /* Prefer oneshot capable device */
308 if (!(newdev->features & CLOCK_EVT_FEAT_ONESHOT)) {
309 if (curdev && (curdev->features & CLOCK_EVT_FEAT_ONESHOT))
310 return false;
311 if (tick_oneshot_mode_active())
312 return false;
313 }
314
315 /*
316 * Use the higher rated one, but prefer a CPU local device with a lower
317 * rating than a non-CPU local device
318 */
319 return !curdev ||
320 newdev->rating > curdev->rating ||
321 !cpumask_equal(curdev->cpumask, newdev->cpumask);
322}
323
324/*
325 * Check whether the new device is a better fit than curdev. curdev
326 * can be NULL !
327 */
328bool tick_check_replacement(struct clock_event_device *curdev,
329 struct clock_event_device *newdev)
330{
331 if (!tick_check_percpu(curdev, newdev, smp_processor_id()))
332 return false;
333
334 return tick_check_preferred(curdev, newdev);
335}
336
337/*
338 * Check, if the new registered device should be used. Called with
339 * clockevents_lock held and interrupts disabled.
340 */
341void tick_check_new_device(struct clock_event_device *newdev)
342{
343 struct clock_event_device *curdev;
344 struct tick_device *td;
345 int cpu;
346
347 cpu = smp_processor_id();
348 td = &per_cpu(tick_cpu_device, cpu);
349 curdev = td->evtdev;
350
351 if (!tick_check_replacement(curdev, newdev))
352 goto out_bc;
353
354 if (!try_module_get(newdev->owner))
355 return;
356
357 /*
358 * Replace the eventually existing device by the new
359 * device. If the current device is the broadcast device, do
360 * not give it back to the clockevents layer !
361 */
362 if (tick_is_broadcast_device(curdev)) {
363 clockevents_shutdown(curdev);
364 curdev = NULL;
365 }
366 clockevents_exchange_device(curdev, newdev);
367 tick_setup_device(td, newdev, cpu, cpumask_of(cpu));
368 if (newdev->features & CLOCK_EVT_FEAT_ONESHOT)
369 tick_oneshot_notify();
370 return;
371
372out_bc:
373 /*
374 * Can the new device be used as a broadcast device ?
375 */
376 tick_install_broadcast_device(newdev, cpu);
377}
378
379/**
380 * tick_broadcast_oneshot_control - Enter/exit broadcast oneshot mode
381 * @state: The target state (enter/exit)
382 *
383 * The system enters/leaves a state, where affected devices might stop
384 * Returns 0 on success, -EBUSY if the cpu is used to broadcast wakeups.
385 *
386 * Called with interrupts disabled, so clockevents_lock is not
387 * required here because the local clock event device cannot go away
388 * under us.
389 */
390int tick_broadcast_oneshot_control(enum tick_broadcast_state state)
391{
392 struct tick_device *td = this_cpu_ptr(&tick_cpu_device);
393
394 if (!(td->evtdev->features & CLOCK_EVT_FEAT_C3STOP))
395 return 0;
396
397 return __tick_broadcast_oneshot_control(state);
398}
399EXPORT_SYMBOL_GPL(tick_broadcast_oneshot_control);
400
401#ifdef CONFIG_HOTPLUG_CPU
402/*
403 * Transfer the do_timer job away from a dying cpu.
404 *
405 * Called with interrupts disabled. No locking required. If
406 * tick_do_timer_cpu is owned by this cpu, nothing can change it.
407 */
408void tick_handover_do_timer(void)
409{
410 if (tick_do_timer_cpu == smp_processor_id())
411 tick_do_timer_cpu = cpumask_first(cpu_online_mask);
412}
413
414/*
415 * Shutdown an event device on a given cpu:
416 *
417 * This is called on a life CPU, when a CPU is dead. So we cannot
418 * access the hardware device itself.
419 * We just set the mode and remove it from the lists.
420 */
421void tick_shutdown(unsigned int cpu)
422{
423 struct tick_device *td = &per_cpu(tick_cpu_device, cpu);
424 struct clock_event_device *dev = td->evtdev;
425
426 td->mode = TICKDEV_MODE_PERIODIC;
427 if (dev) {
428 /*
429 * Prevent that the clock events layer tries to call
430 * the set mode function!
431 */
432 clockevent_set_state(dev, CLOCK_EVT_STATE_DETACHED);
433 clockevents_exchange_device(dev, NULL);
434 dev->event_handler = clockevents_handle_noop;
435 td->evtdev = NULL;
436 }
437}
438#endif
439
440/**
441 * tick_suspend_local - Suspend the local tick device
442 *
443 * Called from the local cpu for freeze with interrupts disabled.
444 *
445 * No locks required. Nothing can change the per cpu device.
446 */
447void tick_suspend_local(void)
448{
449 struct tick_device *td = this_cpu_ptr(&tick_cpu_device);
450
451 clockevents_shutdown(td->evtdev);
452}
453
454/**
455 * tick_resume_local - Resume the local tick device
456 *
457 * Called from the local CPU for unfreeze or XEN resume magic.
458 *
459 * No locks required. Nothing can change the per cpu device.
460 */
461void tick_resume_local(void)
462{
463 struct tick_device *td = this_cpu_ptr(&tick_cpu_device);
464 bool broadcast = tick_resume_check_broadcast();
465
466 clockevents_tick_resume(td->evtdev);
467 if (!broadcast) {
468 if (td->mode == TICKDEV_MODE_PERIODIC)
469 tick_setup_periodic(td->evtdev, 0);
470 else
471 tick_resume_oneshot();
472 }
473}
474
475/**
476 * tick_suspend - Suspend the tick and the broadcast device
477 *
478 * Called from syscore_suspend() via timekeeping_suspend with only one
479 * CPU online and interrupts disabled or from tick_unfreeze() under
480 * tick_freeze_lock.
481 *
482 * No locks required. Nothing can change the per cpu device.
483 */
484void tick_suspend(void)
485{
486 tick_suspend_local();
487 tick_suspend_broadcast();
488}
489
490/**
491 * tick_resume - Resume the tick and the broadcast device
492 *
493 * Called from syscore_resume() via timekeeping_resume with only one
494 * CPU online and interrupts disabled.
495 *
496 * No locks required. Nothing can change the per cpu device.
497 */
498void tick_resume(void)
499{
500 tick_resume_broadcast();
501 tick_resume_local();
502}
503
504#ifdef CONFIG_SUSPEND
505static DEFINE_RAW_SPINLOCK(tick_freeze_lock);
506static unsigned int tick_freeze_depth;
507
508/**
509 * tick_freeze - Suspend the local tick and (possibly) timekeeping.
510 *
511 * Check if this is the last online CPU executing the function and if so,
512 * suspend timekeeping. Otherwise suspend the local tick.
513 *
514 * Call with interrupts disabled. Must be balanced with %tick_unfreeze().
515 * Interrupts must not be enabled before the subsequent %tick_unfreeze().
516 */
517void tick_freeze(void)
518{
519 raw_spin_lock(&tick_freeze_lock);
520
521 tick_freeze_depth++;
522 if (tick_freeze_depth == num_online_cpus()) {
523 trace_suspend_resume(TPS("timekeeping_freeze"),
524 smp_processor_id(), true);
525 system_state = SYSTEM_SUSPEND;
526 sched_clock_suspend();
527 timekeeping_suspend();
528 } else {
529 tick_suspend_local();
530 }
531
532 raw_spin_unlock(&tick_freeze_lock);
533}
534
535/**
536 * tick_unfreeze - Resume the local tick and (possibly) timekeeping.
537 *
538 * Check if this is the first CPU executing the function and if so, resume
539 * timekeeping. Otherwise resume the local tick.
540 *
541 * Call with interrupts disabled. Must be balanced with %tick_freeze().
542 * Interrupts must not be enabled after the preceding %tick_freeze().
543 */
544void tick_unfreeze(void)
545{
546 raw_spin_lock(&tick_freeze_lock);
547
548 if (tick_freeze_depth == num_online_cpus()) {
549 timekeeping_resume();
550 sched_clock_resume();
551 system_state = SYSTEM_RUNNING;
552 trace_suspend_resume(TPS("timekeeping_freeze"),
553 smp_processor_id(), false);
554 } else {
555 touch_softlockup_watchdog();
556 tick_resume_local();
557 }
558
559 tick_freeze_depth--;
560
561 raw_spin_unlock(&tick_freeze_lock);
562}
563#endif /* CONFIG_SUSPEND */
564
565/**
566 * tick_init - initialize the tick control
567 */
568void __init tick_init(void)
569{
570 tick_broadcast_init();
571 tick_nohz_init();
572}