1/*
2 * cpuidle.c - core cpuidle infrastructure
3 *
4 * (C) 2006-2007 Venkatesh Pallipadi <venkatesh.pallipadi@intel.com>
5 * Shaohua Li <shaohua.li@intel.com>
6 * Adam Belay <abelay@novell.com>
7 *
8 * This code is licenced under the GPL.
9 */
10
11#include "linux/percpu-defs.h"
12#include <linux/clockchips.h>
13#include <linux/kernel.h>
14#include <linux/mutex.h>
15#include <linux/sched.h>
16#include <linux/sched/clock.h>
17#include <linux/sched/idle.h>
18#include <linux/notifier.h>
19#include <linux/pm_qos.h>
20#include <linux/cpu.h>
21#include <linux/cpuidle.h>
22#include <linux/ktime.h>
23#include <linux/hrtimer.h>
24#include <linux/module.h>
25#include <linux/suspend.h>
26#include <linux/tick.h>
27#include <linux/mmu_context.h>
28#include <linux/context_tracking.h>
29#include <trace/events/power.h>
30
31#include "cpuidle.h"
32
33DEFINE_PER_CPU(struct cpuidle_device *, cpuidle_devices);
34DEFINE_PER_CPU(struct cpuidle_device, cpuidle_dev);
35
36DEFINE_MUTEX(cpuidle_lock);
37LIST_HEAD(cpuidle_detected_devices);
38
39static int enabled_devices;
40static int off __read_mostly;
41static int initialized __read_mostly;
42
43int cpuidle_disabled(void)
44{
45 return off;
46}
47void disable_cpuidle(void)
48{
49 off = 1;
50}
51
52bool cpuidle_not_available(struct cpuidle_driver *drv,
53 struct cpuidle_device *dev)
54{
55 return off || !initialized || !drv || !dev || !dev->enabled;
56}
57
58/**
59 * cpuidle_play_dead - cpu off-lining
60 *
61 * Returns in case of an error or no driver
62 */
63int cpuidle_play_dead(void)
64{
65 struct cpuidle_device *dev = __this_cpu_read(cpuidle_devices);
66 struct cpuidle_driver *drv = cpuidle_get_cpu_driver(dev);
67 int i;
68
69 if (!drv)
70 return -ENODEV;
71
72 for (i = drv->state_count - 1; i >= 0; i--) {
73 if (drv->states[i].enter_dead)
74 drv->states[i].enter_dead(dev, i);
75 }
76
77 /*
78 * If :enter_dead() is successful, it will never return, so reaching
79 * here means that all of them failed above or were not present.
80 */
81 return -ENODEV;
82}
83
84static int find_deepest_state(struct cpuidle_driver *drv,
85 struct cpuidle_device *dev,
86 u64 max_latency_ns,
87 unsigned int forbidden_flags,
88 bool s2idle)
89{
90 u64 latency_req = 0;
91 int i, ret = 0;
92
93 for (i = 1; i < drv->state_count; i++) {
94 struct cpuidle_state *s = &drv->states[i];
95
96 if (dev->states_usage[i].disable ||
97 s->exit_latency_ns <= latency_req ||
98 s->exit_latency_ns > max_latency_ns ||
99 (s->flags & forbidden_flags) ||
100 (s2idle && !s->enter_s2idle))
101 continue;
102
103 latency_req = s->exit_latency_ns;
104 ret = i;
105 }
106 return ret;
107}
108
109/**
110 * cpuidle_use_deepest_state - Set/unset governor override mode.
111 * @latency_limit_ns: Idle state exit latency limit (or no override if 0).
112 *
113 * If @latency_limit_ns is nonzero, set the current CPU to use the deepest idle
114 * state with exit latency within @latency_limit_ns (override governors going
115 * forward), or do not override governors if it is zero.
116 */
117void cpuidle_use_deepest_state(u64 latency_limit_ns)
118{
119 struct cpuidle_device *dev;
120
121 preempt_disable();
122 dev = cpuidle_get_device();
123 if (dev)
124 dev->forced_idle_latency_limit_ns = latency_limit_ns;
125 preempt_enable();
126}
127
128/**
129 * cpuidle_find_deepest_state - Find the deepest available idle state.
130 * @drv: cpuidle driver for the given CPU.
131 * @dev: cpuidle device for the given CPU.
132 * @latency_limit_ns: Idle state exit latency limit
133 *
134 * Return: the index of the deepest available idle state.
135 */
136int cpuidle_find_deepest_state(struct cpuidle_driver *drv,
137 struct cpuidle_device *dev,
138 u64 latency_limit_ns)
139{
140 return find_deepest_state(drv, dev, max_latency_ns: latency_limit_ns, forbidden_flags: 0, s2idle: false);
141}
142
143#ifdef CONFIG_SUSPEND
144static noinstr void enter_s2idle_proper(struct cpuidle_driver *drv,
145 struct cpuidle_device *dev, int index)
146{
147 struct cpuidle_state *target_state = &drv->states[index];
148 ktime_t time_start, time_end;
149
150 instrumentation_begin();
151
152 time_start = ns_to_ktime(ns: local_clock_noinstr());
153
154 tick_freeze();
155 /*
156 * The state used here cannot be a "coupled" one, because the "coupled"
157 * cpuidle mechanism enables interrupts and doing that with timekeeping
158 * suspended is generally unsafe.
159 */
160 stop_critical_timings();
161 if (!(target_state->flags & CPUIDLE_FLAG_RCU_IDLE)) {
162 ct_cpuidle_enter();
163 /* Annotate away the indirect call */
164 instrumentation_begin();
165 }
166 target_state->enter_s2idle(dev, drv, index);
167 if (WARN_ON_ONCE(!irqs_disabled()))
168 raw_local_irq_disable();
169 if (!(target_state->flags & CPUIDLE_FLAG_RCU_IDLE)) {
170 instrumentation_end();
171 ct_cpuidle_exit();
172 }
173 tick_unfreeze();
174 start_critical_timings();
175
176 time_end = ns_to_ktime(ns: local_clock_noinstr());
177
178 dev->states_usage[index].s2idle_time += ktime_us_delta(later: time_end, earlier: time_start);
179 dev->states_usage[index].s2idle_usage++;
180 instrumentation_end();
181}
182
183/**
184 * cpuidle_enter_s2idle - Enter an idle state suitable for suspend-to-idle.
185 * @drv: cpuidle driver for the given CPU.
186 * @dev: cpuidle device for the given CPU.
187 * @latency_limit_ns: Idle state exit latency limit
188 *
189 * If there are states with the ->enter_s2idle callback, find the deepest of
190 * them and enter it with frozen tick.
191 */
192int cpuidle_enter_s2idle(struct cpuidle_driver *drv, struct cpuidle_device *dev,
193 u64 latency_limit_ns)
194{
195 int index;
196
197 /*
198 * Find the deepest state with ->enter_s2idle present that meets the
199 * specified latency limit, which guarantees that interrupts won't be
200 * enabled when it exits and allows the tick to be frozen safely.
201 */
202 index = find_deepest_state(drv, dev, max_latency_ns: latency_limit_ns, forbidden_flags: 0, s2idle: true);
203 if (index > 0) {
204 enter_s2idle_proper(drv, dev, index);
205 local_irq_enable();
206 }
207 return index;
208}
209#endif /* CONFIG_SUSPEND */
210
211/**
212 * cpuidle_enter_state - enter the state and update stats
213 * @dev: cpuidle device for this cpu
214 * @drv: cpuidle driver for this cpu
215 * @index: index into the states table in @drv of the state to enter
216 */
217noinstr int cpuidle_enter_state(struct cpuidle_device *dev,
218 struct cpuidle_driver *drv,
219 int index)
220{
221 int entered_state;
222
223 struct cpuidle_state *target_state = &drv->states[index];
224 bool broadcast = !!(target_state->flags & CPUIDLE_FLAG_TIMER_STOP);
225 ktime_t time_start, time_end;
226
227 instrumentation_begin();
228
229 /*
230 * Tell the time framework to switch to a broadcast timer because our
231 * local timer will be shut down. If a local timer is used from another
232 * CPU as a broadcast timer, this call may fail if it is not available.
233 */
234 if (broadcast && tick_broadcast_enter()) {
235 index = find_deepest_state(drv, dev, max_latency_ns: target_state->exit_latency_ns,
236 CPUIDLE_FLAG_TIMER_STOP, s2idle: false);
237
238 target_state = &drv->states[index];
239 broadcast = false;
240 }
241
242 if (target_state->flags & CPUIDLE_FLAG_TLB_FLUSHED)
243 leave_mm();
244
245 /* Take note of the planned idle state. */
246 sched_idle_set_state(idle_state: target_state);
247
248 trace_cpu_idle(state: index, cpu_id: dev->cpu);
249 time_start = ns_to_ktime(ns: local_clock_noinstr());
250
251 stop_critical_timings();
252 if (!(target_state->flags & CPUIDLE_FLAG_RCU_IDLE)) {
253 ct_cpuidle_enter();
254 /* Annotate away the indirect call */
255 instrumentation_begin();
256 }
257
258 /*
259 * NOTE!!
260 *
261 * For cpuidle_state::enter() methods that do *NOT* set
262 * CPUIDLE_FLAG_RCU_IDLE RCU will be disabled here and these functions
263 * must be marked either noinstr or __cpuidle.
264 *
265 * For cpuidle_state::enter() methods that *DO* set
266 * CPUIDLE_FLAG_RCU_IDLE this isn't required, but they must mark the
267 * function calling ct_cpuidle_enter() as noinstr/__cpuidle and all
268 * functions called within the RCU-idle region.
269 */
270 entered_state = target_state->enter(dev, drv, index);
271
272 if (WARN_ONCE(!irqs_disabled(), "%ps leaked IRQ state", target_state->enter))
273 raw_local_irq_disable();
274
275 if (!(target_state->flags & CPUIDLE_FLAG_RCU_IDLE)) {
276 instrumentation_end();
277 ct_cpuidle_exit();
278 }
279 start_critical_timings();
280
281 sched_clock_idle_wakeup_event();
282 time_end = ns_to_ktime(ns: local_clock_noinstr());
283 trace_cpu_idle(PWR_EVENT_EXIT, cpu_id: dev->cpu);
284
285 /* The cpu is no longer idle or about to enter idle. */
286 sched_idle_set_state(NULL);
287
288 if (broadcast)
289 tick_broadcast_exit();
290
291 if (!cpuidle_state_is_coupled(drv, state: index))
292 local_irq_enable();
293
294 if (entered_state >= 0) {
295 s64 diff, delay = drv->states[entered_state].exit_latency_ns;
296 int i;
297
298 /*
299 * Update cpuidle counters
300 * This can be moved to within driver enter routine,
301 * but that results in multiple copies of same code.
302 */
303 diff = ktime_sub(time_end, time_start);
304
305 dev->last_residency_ns = diff;
306 dev->states_usage[entered_state].time_ns += diff;
307 dev->states_usage[entered_state].usage++;
308
309 if (diff < drv->states[entered_state].target_residency_ns) {
310 for (i = entered_state - 1; i >= 0; i--) {
311 if (dev->states_usage[i].disable)
312 continue;
313
314 /* Shallower states are enabled, so update. */
315 dev->states_usage[entered_state].above++;
316 trace_cpu_idle_miss(cpu_id: dev->cpu, state: entered_state, below: false);
317 break;
318 }
319 } else if (diff > delay) {
320 for (i = entered_state + 1; i < drv->state_count; i++) {
321 if (dev->states_usage[i].disable)
322 continue;
323
324 /*
325 * Update if a deeper state would have been a
326 * better match for the observed idle duration.
327 */
328 if (diff - delay >= drv->states[i].target_residency_ns) {
329 dev->states_usage[entered_state].below++;
330 trace_cpu_idle_miss(cpu_id: dev->cpu, state: entered_state, below: true);
331 }
332
333 break;
334 }
335 }
336 } else {
337 dev->last_residency_ns = 0;
338 dev->states_usage[index].rejected++;
339 }
340
341 instrumentation_end();
342
343 return entered_state;
344}
345
346/**
347 * cpuidle_select - ask the cpuidle framework to choose an idle state
348 *
349 * @drv: the cpuidle driver
350 * @dev: the cpuidle device
351 * @stop_tick: indication on whether or not to stop the tick
352 *
353 * Returns the index of the idle state. The return value must not be negative.
354 *
355 * The memory location pointed to by @stop_tick is expected to be written the
356 * 'false' boolean value if the scheduler tick should not be stopped before
357 * entering the returned state.
358 */
359int cpuidle_select(struct cpuidle_driver *drv, struct cpuidle_device *dev,
360 bool *stop_tick)
361{
362 return cpuidle_curr_governor->select(drv, dev, stop_tick);
363}
364
365/**
366 * cpuidle_enter - enter into the specified idle state
367 *
368 * @drv: the cpuidle driver tied with the cpu
369 * @dev: the cpuidle device
370 * @index: the index in the idle state table
371 *
372 * Returns the index in the idle state, < 0 in case of error.
373 * The error code depends on the backend driver
374 */
375int cpuidle_enter(struct cpuidle_driver *drv, struct cpuidle_device *dev,
376 int index)
377{
378 int ret = 0;
379
380 /*
381 * Store the next hrtimer, which becomes either next tick or the next
382 * timer event, whatever expires first. Additionally, to make this data
383 * useful for consumers outside cpuidle, we rely on that the governor's
384 * ->select() callback have decided, whether to stop the tick or not.
385 */
386 WRITE_ONCE(dev->next_hrtimer, tick_nohz_get_next_hrtimer());
387
388 if (cpuidle_state_is_coupled(drv, state: index))
389 ret = cpuidle_enter_state_coupled(dev, drv, next_state: index);
390 else
391 ret = cpuidle_enter_state(dev, drv, index);
392
393 WRITE_ONCE(dev->next_hrtimer, 0);
394 return ret;
395}
396
397/**
398 * cpuidle_reflect - tell the underlying governor what was the state
399 * we were in
400 *
401 * @dev : the cpuidle device
402 * @index: the index in the idle state table
403 *
404 */
405void cpuidle_reflect(struct cpuidle_device *dev, int index)
406{
407 if (cpuidle_curr_governor->reflect && index >= 0)
408 cpuidle_curr_governor->reflect(dev, index);
409}
410
411/*
412 * Min polling interval of 10usec is a guess. It is assuming that
413 * for most users, the time for a single ping-pong workload like
414 * perf bench pipe would generally complete within 10usec but
415 * this is hardware dependent. Actual time can be estimated with
416 *
417 * perf bench sched pipe -l 10000
418 *
419 * Run multiple times to avoid cpufreq effects.
420 */
421#define CPUIDLE_POLL_MIN 10000
422#define CPUIDLE_POLL_MAX (TICK_NSEC / 16)
423
424/**
425 * cpuidle_poll_time - return amount of time to poll for,
426 * governors can override dev->poll_limit_ns if necessary
427 *
428 * @drv: the cpuidle driver tied with the cpu
429 * @dev: the cpuidle device
430 *
431 */
432__cpuidle u64 cpuidle_poll_time(struct cpuidle_driver *drv,
433 struct cpuidle_device *dev)
434{
435 int i;
436 u64 limit_ns;
437
438 BUILD_BUG_ON(CPUIDLE_POLL_MIN > CPUIDLE_POLL_MAX);
439
440 if (dev->poll_limit_ns)
441 return dev->poll_limit_ns;
442
443 limit_ns = CPUIDLE_POLL_MAX;
444 for (i = 1; i < drv->state_count; i++) {
445 u64 state_limit;
446
447 if (dev->states_usage[i].disable)
448 continue;
449
450 state_limit = drv->states[i].target_residency_ns;
451 if (state_limit < CPUIDLE_POLL_MIN)
452 continue;
453
454 limit_ns = min_t(u64, state_limit, CPUIDLE_POLL_MAX);
455 break;
456 }
457
458 dev->poll_limit_ns = limit_ns;
459
460 return dev->poll_limit_ns;
461}
462
463/**
464 * cpuidle_install_idle_handler - installs the cpuidle idle loop handler
465 */
466void cpuidle_install_idle_handler(void)
467{
468 if (enabled_devices) {
469 /* Make sure all changes finished before we switch to new idle */
470 smp_wmb();
471 initialized = 1;
472 }
473}
474
475/**
476 * cpuidle_uninstall_idle_handler - uninstalls the cpuidle idle loop handler
477 */
478void cpuidle_uninstall_idle_handler(void)
479{
480 if (enabled_devices) {
481 initialized = 0;
482 wake_up_all_idle_cpus();
483 }
484
485 /*
486 * Make sure external observers (such as the scheduler)
487 * are done looking at pointed idle states.
488 */
489 synchronize_rcu();
490}
491
492/**
493 * cpuidle_pause_and_lock - temporarily disables CPUIDLE
494 */
495void cpuidle_pause_and_lock(void)
496{
497 mutex_lock(&cpuidle_lock);
498 cpuidle_uninstall_idle_handler();
499}
500
501EXPORT_SYMBOL_GPL(cpuidle_pause_and_lock);
502
503/**
504 * cpuidle_resume_and_unlock - resumes CPUIDLE operation
505 */
506void cpuidle_resume_and_unlock(void)
507{
508 cpuidle_install_idle_handler();
509 mutex_unlock(lock: &cpuidle_lock);
510}
511
512EXPORT_SYMBOL_GPL(cpuidle_resume_and_unlock);
513
514/* Currently used in suspend/resume path to suspend cpuidle */
515void cpuidle_pause(void)
516{
517 mutex_lock(&cpuidle_lock);
518 cpuidle_uninstall_idle_handler();
519 mutex_unlock(lock: &cpuidle_lock);
520}
521
522/* Currently used in suspend/resume path to resume cpuidle */
523void cpuidle_resume(void)
524{
525 mutex_lock(&cpuidle_lock);
526 cpuidle_install_idle_handler();
527 mutex_unlock(lock: &cpuidle_lock);
528}
529
530/**
531 * cpuidle_enable_device - enables idle PM for a CPU
532 * @dev: the CPU
533 *
534 * This function must be called between cpuidle_pause_and_lock and
535 * cpuidle_resume_and_unlock when used externally.
536 */
537int cpuidle_enable_device(struct cpuidle_device *dev)
538{
539 int ret;
540 struct cpuidle_driver *drv;
541
542 if (!dev)
543 return -EINVAL;
544
545 if (dev->enabled)
546 return 0;
547
548 if (!cpuidle_curr_governor)
549 return -EIO;
550
551 drv = cpuidle_get_cpu_driver(dev);
552
553 if (!drv)
554 return -EIO;
555
556 if (!dev->registered)
557 return -EINVAL;
558
559 ret = cpuidle_add_device_sysfs(device: dev);
560 if (ret)
561 return ret;
562
563 if (cpuidle_curr_governor->enable) {
564 ret = cpuidle_curr_governor->enable(drv, dev);
565 if (ret)
566 goto fail_sysfs;
567 }
568
569 smp_wmb();
570
571 dev->enabled = 1;
572
573 enabled_devices++;
574 return 0;
575
576fail_sysfs:
577 cpuidle_remove_device_sysfs(device: dev);
578
579 return ret;
580}
581
582EXPORT_SYMBOL_GPL(cpuidle_enable_device);
583
584/**
585 * cpuidle_disable_device - disables idle PM for a CPU
586 * @dev: the CPU
587 *
588 * This function must be called between cpuidle_pause_and_lock and
589 * cpuidle_resume_and_unlock when used externally.
590 */
591void cpuidle_disable_device(struct cpuidle_device *dev)
592{
593 struct cpuidle_driver *drv = cpuidle_get_cpu_driver(dev);
594
595 if (!dev || !dev->enabled)
596 return;
597
598 if (!drv || !cpuidle_curr_governor)
599 return;
600
601 dev->enabled = 0;
602
603 if (cpuidle_curr_governor->disable)
604 cpuidle_curr_governor->disable(drv, dev);
605
606 cpuidle_remove_device_sysfs(device: dev);
607 enabled_devices--;
608}
609
610EXPORT_SYMBOL_GPL(cpuidle_disable_device);
611
612static void __cpuidle_unregister_device(struct cpuidle_device *dev)
613{
614 struct cpuidle_driver *drv = cpuidle_get_cpu_driver(dev);
615
616 list_del(entry: &dev->device_list);
617 per_cpu(cpuidle_devices, dev->cpu) = NULL;
618 module_put(module: drv->owner);
619
620 dev->registered = 0;
621}
622
623static void __cpuidle_device_init(struct cpuidle_device *dev)
624{
625 memset(dev->states_usage, 0, sizeof(dev->states_usage));
626 dev->last_residency_ns = 0;
627 dev->next_hrtimer = 0;
628}
629
630/**
631 * __cpuidle_register_device - internal register function called before register
632 * and enable routines
633 * @dev: the cpu
634 *
635 * cpuidle_lock mutex must be held before this is called
636 */
637static int __cpuidle_register_device(struct cpuidle_device *dev)
638{
639 struct cpuidle_driver *drv = cpuidle_get_cpu_driver(dev);
640 unsigned int cpu = dev->cpu;
641 int i, ret;
642
643 if (per_cpu(cpuidle_devices, cpu)) {
644 pr_info("CPU%d: cpuidle device already registered\n", cpu);
645 return -EEXIST;
646 }
647
648 if (!try_module_get(module: drv->owner))
649 return -EINVAL;
650
651 for (i = 0; i < drv->state_count; i++) {
652 if (drv->states[i].flags & CPUIDLE_FLAG_UNUSABLE)
653 dev->states_usage[i].disable |= CPUIDLE_STATE_DISABLED_BY_DRIVER;
654
655 if (drv->states[i].flags & CPUIDLE_FLAG_OFF)
656 dev->states_usage[i].disable |= CPUIDLE_STATE_DISABLED_BY_USER;
657 }
658
659 per_cpu(cpuidle_devices, cpu) = dev;
660 list_add(new: &dev->device_list, head: &cpuidle_detected_devices);
661
662 ret = cpuidle_coupled_register_device(dev);
663 if (ret)
664 __cpuidle_unregister_device(dev);
665 else
666 dev->registered = 1;
667
668 return ret;
669}
670
671/**
672 * cpuidle_register_device - registers a CPU's idle PM feature
673 * @dev: the cpu
674 */
675int cpuidle_register_device(struct cpuidle_device *dev)
676{
677 int ret = -EBUSY;
678
679 if (!dev)
680 return -EINVAL;
681
682 mutex_lock(&cpuidle_lock);
683
684 if (dev->registered)
685 goto out_unlock;
686
687 __cpuidle_device_init(dev);
688
689 ret = __cpuidle_register_device(dev);
690 if (ret)
691 goto out_unlock;
692
693 ret = cpuidle_add_sysfs(dev);
694 if (ret)
695 goto out_unregister;
696
697 ret = cpuidle_enable_device(dev);
698 if (ret)
699 goto out_sysfs;
700
701 cpuidle_install_idle_handler();
702
703out_unlock:
704 mutex_unlock(lock: &cpuidle_lock);
705
706 return ret;
707
708out_sysfs:
709 cpuidle_remove_sysfs(dev);
710out_unregister:
711 __cpuidle_unregister_device(dev);
712 goto out_unlock;
713}
714
715EXPORT_SYMBOL_GPL(cpuidle_register_device);
716
717/**
718 * cpuidle_unregister_device - unregisters a CPU's idle PM feature
719 * @dev: the cpu
720 */
721void cpuidle_unregister_device(struct cpuidle_device *dev)
722{
723 if (!dev || dev->registered == 0)
724 return;
725
726 cpuidle_pause_and_lock();
727
728 cpuidle_disable_device(dev);
729
730 cpuidle_remove_sysfs(dev);
731
732 __cpuidle_unregister_device(dev);
733
734 cpuidle_coupled_unregister_device(dev);
735
736 cpuidle_resume_and_unlock();
737}
738
739EXPORT_SYMBOL_GPL(cpuidle_unregister_device);
740
741/**
742 * cpuidle_unregister: unregister a driver and the devices. This function
743 * can be used only if the driver has been previously registered through
744 * the cpuidle_register function.
745 *
746 * @drv: a valid pointer to a struct cpuidle_driver
747 */
748void cpuidle_unregister(struct cpuidle_driver *drv)
749{
750 int cpu;
751 struct cpuidle_device *device;
752
753 for_each_cpu(cpu, drv->cpumask) {
754 device = &per_cpu(cpuidle_dev, cpu);
755 cpuidle_unregister_device(device);
756 }
757
758 cpuidle_unregister_driver(drv);
759}
760EXPORT_SYMBOL_GPL(cpuidle_unregister);
761
762/**
763 * cpuidle_register: registers the driver and the cpu devices with the
764 * coupled_cpus passed as parameter. This function is used for all common
765 * initialization pattern there are in the arch specific drivers. The
766 * devices is globally defined in this file.
767 *
768 * @drv : a valid pointer to a struct cpuidle_driver
769 * @coupled_cpus: a cpumask for the coupled states
770 *
771 * Returns 0 on success, < 0 otherwise
772 */
773int cpuidle_register(struct cpuidle_driver *drv,
774 const struct cpumask *const coupled_cpus)
775{
776 int ret, cpu;
777 struct cpuidle_device *device;
778
779 ret = cpuidle_register_driver(drv);
780 if (ret) {
781 pr_err("failed to register cpuidle driver\n");
782 return ret;
783 }
784
785 for_each_cpu(cpu, drv->cpumask) {
786 device = &per_cpu(cpuidle_dev, cpu);
787 device->cpu = cpu;
788
789#ifdef CONFIG_ARCH_NEEDS_CPU_IDLE_COUPLED
790 /*
791 * On multiplatform for ARM, the coupled idle states could be
792 * enabled in the kernel even if the cpuidle driver does not
793 * use it. Note, coupled_cpus is a struct copy.
794 */
795 if (coupled_cpus)
796 device->coupled_cpus = *coupled_cpus;
797#endif
798 ret = cpuidle_register_device(device);
799 if (!ret)
800 continue;
801
802 pr_err("Failed to register cpuidle device for cpu%d\n", cpu);
803
804 cpuidle_unregister(drv);
805 break;
806 }
807
808 return ret;
809}
810EXPORT_SYMBOL_GPL(cpuidle_register);
811
812/**
813 * cpuidle_init - core initializer
814 */
815static int __init cpuidle_init(void)
816{
817 if (cpuidle_disabled())
818 return -ENODEV;
819
820 return cpuidle_add_interface();
821}
822
823module_param(off, int, 0444);
824module_param_string(governor, param_governor, CPUIDLE_NAME_LEN, 0444);
825core_initcall(cpuidle_init);
826

source code of linux/drivers/cpuidle/cpuidle.c