cpuidle.c revision bf4d1b5ddb78f86078ac6ae0415802d5f0c68f92 
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/kernel.h>
12#include <linux/mutex.h>
13#include <linux/sched.h>
14#include <linux/notifier.h>
15#include <linux/pm_qos.h>
16#include <linux/cpu.h>
17#include <linux/cpuidle.h>
18#include <linux/ktime.h>
19#include <linux/hrtimer.h>
20#include <linux/module.h>
21#include <trace/events/power.h>
22
23#include "cpuidle.h"
24
25DEFINE_PER_CPU(struct cpuidle_device *, cpuidle_devices);
26
27DEFINE_MUTEX(cpuidle_lock);
28LIST_HEAD(cpuidle_detected_devices);
29
30static int enabled_devices;
31static int off __read_mostly;
32static int initialized __read_mostly;
33
34int cpuidle_disabled(void)
35{
36	return off;
37}
38void disable_cpuidle(void)
39{
40	off = 1;
41}
42
43static int __cpuidle_register_device(struct cpuidle_device *dev);
44
45static inline int cpuidle_enter(struct cpuidle_device *dev,
46				struct cpuidle_driver *drv, int index)
47{
48	struct cpuidle_state *target_state = &drv->states[index];
49	return target_state->enter(dev, drv, index);
50}
51
52static inline int cpuidle_enter_tk(struct cpuidle_device *dev,
53			       struct cpuidle_driver *drv, int index)
54{
55	return cpuidle_wrap_enter(dev, drv, index, cpuidle_enter);
56}
57
58typedef int (*cpuidle_enter_t)(struct cpuidle_device *dev,
59			       struct cpuidle_driver *drv, int index);
60
61static cpuidle_enter_t cpuidle_enter_ops;
62
63/**
64 * cpuidle_play_dead - cpu off-lining
65 *
66 * Returns in case of an error or no driver
67 */
68int cpuidle_play_dead(void)
69{
70	struct cpuidle_device *dev = __this_cpu_read(cpuidle_devices);
71	struct cpuidle_driver *drv = cpuidle_get_cpu_driver(dev);
72	int i, dead_state = -1;
73	int power_usage = -1;
74
75	if (!drv)
76		return -ENODEV;
77
78	/* Find lowest-power state that supports long-term idle */
79	for (i = CPUIDLE_DRIVER_STATE_START; i < drv->state_count; i++) {
80		struct cpuidle_state *s = &drv->states[i];
81
82		if (s->power_usage < power_usage && s->enter_dead) {
83			power_usage = s->power_usage;
84			dead_state = i;
85		}
86	}
87
88	if (dead_state != -1)
89		return drv->states[dead_state].enter_dead(dev, dead_state);
90
91	return -ENODEV;
92}
93
94/**
95 * cpuidle_enter_state - enter the state and update stats
96 * @dev: cpuidle device for this cpu
97 * @drv: cpuidle driver for this cpu
98 * @next_state: index into drv->states of the state to enter
99 */
100int cpuidle_enter_state(struct cpuidle_device *dev, struct cpuidle_driver *drv,
101		int next_state)
102{
103	int entered_state;
104
105	entered_state = cpuidle_enter_ops(dev, drv, next_state);
106
107	if (entered_state >= 0) {
108		/* Update cpuidle counters */
109		/* This can be moved to within driver enter routine
110		 * but that results in multiple copies of same code.
111		 */
112		dev->states_usage[entered_state].time +=
113				(unsigned long long)dev->last_residency;
114		dev->states_usage[entered_state].usage++;
115	} else {
116		dev->last_residency = 0;
117	}
118
119	return entered_state;
120}
121
122/**
123 * cpuidle_idle_call - the main idle loop
124 *
125 * NOTE: no locks or semaphores should be used here
126 * return non-zero on failure
127 */
128int cpuidle_idle_call(void)
129{
130	struct cpuidle_device *dev = __this_cpu_read(cpuidle_devices);
131	struct cpuidle_driver *drv;
132	int next_state, entered_state;
133
134	if (off)
135		return -ENODEV;
136
137	if (!initialized)
138		return -ENODEV;
139
140	/* check if the device is ready */
141	if (!dev || !dev->enabled)
142		return -EBUSY;
143
144	drv = cpuidle_get_cpu_driver(dev);
145
146	/* ask the governor for the next state */
147	next_state = cpuidle_curr_governor->select(drv, dev);
148	if (need_resched()) {
149		dev->last_residency = 0;
150		/* give the governor an opportunity to reflect on the outcome */
151		if (cpuidle_curr_governor->reflect)
152			cpuidle_curr_governor->reflect(dev, next_state);
153		local_irq_enable();
154		return 0;
155	}
156
157	trace_power_start_rcuidle(POWER_CSTATE, next_state, dev->cpu);
158	trace_cpu_idle_rcuidle(next_state, dev->cpu);
159
160	if (cpuidle_state_is_coupled(dev, drv, next_state))
161		entered_state = cpuidle_enter_state_coupled(dev, drv,
162							    next_state);
163	else
164		entered_state = cpuidle_enter_state(dev, drv, next_state);
165
166	trace_power_end_rcuidle(dev->cpu);
167	trace_cpu_idle_rcuidle(PWR_EVENT_EXIT, dev->cpu);
168
169	/* give the governor an opportunity to reflect on the outcome */
170	if (cpuidle_curr_governor->reflect)
171		cpuidle_curr_governor->reflect(dev, entered_state);
172
173	return 0;
174}
175
176/**
177 * cpuidle_install_idle_handler - installs the cpuidle idle loop handler
178 */
179void cpuidle_install_idle_handler(void)
180{
181	if (enabled_devices) {
182		/* Make sure all changes finished before we switch to new idle */
183		smp_wmb();
184		initialized = 1;
185	}
186}
187
188/**
189 * cpuidle_uninstall_idle_handler - uninstalls the cpuidle idle loop handler
190 */
191void cpuidle_uninstall_idle_handler(void)
192{
193	if (enabled_devices) {
194		initialized = 0;
195		kick_all_cpus_sync();
196	}
197}
198
199/**
200 * cpuidle_pause_and_lock - temporarily disables CPUIDLE
201 */
202void cpuidle_pause_and_lock(void)
203{
204	mutex_lock(&cpuidle_lock);
205	cpuidle_uninstall_idle_handler();
206}
207
208EXPORT_SYMBOL_GPL(cpuidle_pause_and_lock);
209
210/**
211 * cpuidle_resume_and_unlock - resumes CPUIDLE operation
212 */
213void cpuidle_resume_and_unlock(void)
214{
215	cpuidle_install_idle_handler();
216	mutex_unlock(&cpuidle_lock);
217}
218
219EXPORT_SYMBOL_GPL(cpuidle_resume_and_unlock);
220
221/* Currently used in suspend/resume path to suspend cpuidle */
222void cpuidle_pause(void)
223{
224	mutex_lock(&cpuidle_lock);
225	cpuidle_uninstall_idle_handler();
226	mutex_unlock(&cpuidle_lock);
227}
228
229/* Currently used in suspend/resume path to resume cpuidle */
230void cpuidle_resume(void)
231{
232	mutex_lock(&cpuidle_lock);
233	cpuidle_install_idle_handler();
234	mutex_unlock(&cpuidle_lock);
235}
236
237/**
238 * cpuidle_wrap_enter - performs timekeeping and irqen around enter function
239 * @dev: pointer to a valid cpuidle_device object
240 * @drv: pointer to a valid cpuidle_driver object
241 * @index: index of the target cpuidle state.
242 */
243int cpuidle_wrap_enter(struct cpuidle_device *dev,
244				struct cpuidle_driver *drv, int index,
245				int (*enter)(struct cpuidle_device *dev,
246					struct cpuidle_driver *drv, int index))
247{
248	ktime_t time_start, time_end;
249	s64 diff;
250
251	time_start = ktime_get();
252
253	index = enter(dev, drv, index);
254
255	time_end = ktime_get();
256
257	local_irq_enable();
258
259	diff = ktime_to_us(ktime_sub(time_end, time_start));
260	if (diff > INT_MAX)
261		diff = INT_MAX;
262
263	dev->last_residency = (int) diff;
264
265	return index;
266}
267
268#ifdef CONFIG_ARCH_HAS_CPU_RELAX
269static int poll_idle(struct cpuidle_device *dev,
270		struct cpuidle_driver *drv, int index)
271{
272	ktime_t	t1, t2;
273	s64 diff;
274
275	t1 = ktime_get();
276	local_irq_enable();
277	while (!need_resched())
278		cpu_relax();
279
280	t2 = ktime_get();
281	diff = ktime_to_us(ktime_sub(t2, t1));
282	if (diff > INT_MAX)
283		diff = INT_MAX;
284
285	dev->last_residency = (int) diff;
286
287	return index;
288}
289
290static void poll_idle_init(struct cpuidle_driver *drv)
291{
292	struct cpuidle_state *state = &drv->states[0];
293
294	snprintf(state->name, CPUIDLE_NAME_LEN, "POLL");
295	snprintf(state->desc, CPUIDLE_DESC_LEN, "CPUIDLE CORE POLL IDLE");
296	state->exit_latency = 0;
297	state->target_residency = 0;
298	state->power_usage = -1;
299	state->flags = 0;
300	state->enter = poll_idle;
301	state->disabled = false;
302}
303#else
304static void poll_idle_init(struct cpuidle_driver *drv) {}
305#endif /* CONFIG_ARCH_HAS_CPU_RELAX */
306
307/**
308 * cpuidle_enable_device - enables idle PM for a CPU
309 * @dev: the CPU
310 *
311 * This function must be called between cpuidle_pause_and_lock and
312 * cpuidle_resume_and_unlock when used externally.
313 */
314int cpuidle_enable_device(struct cpuidle_device *dev)
315{
316	int ret, i;
317	struct cpuidle_driver *drv;
318
319	if (!dev)
320		return -EINVAL;
321
322	if (dev->enabled)
323		return 0;
324
325	drv = cpuidle_get_cpu_driver(dev);
326
327	if (!drv || !cpuidle_curr_governor)
328		return -EIO;
329
330	if (!dev->state_count)
331		dev->state_count = drv->state_count;
332
333	if (dev->registered == 0) {
334		ret = __cpuidle_register_device(dev);
335		if (ret)
336			return ret;
337	}
338
339	cpuidle_enter_ops = drv->en_core_tk_irqen ?
340		cpuidle_enter_tk : cpuidle_enter;
341
342	poll_idle_init(drv);
343
344	ret = cpuidle_add_device_sysfs(dev);
345	if (ret)
346		return ret;
347
348	if (cpuidle_curr_governor->enable &&
349	    (ret = cpuidle_curr_governor->enable(drv, dev)))
350		goto fail_sysfs;
351
352	for (i = 0; i < dev->state_count; i++) {
353		dev->states_usage[i].usage = 0;
354		dev->states_usage[i].time = 0;
355	}
356	dev->last_residency = 0;
357
358	smp_wmb();
359
360	dev->enabled = 1;
361
362	enabled_devices++;
363	return 0;
364
365fail_sysfs:
366	cpuidle_remove_device_sysfs(dev);
367
368	return ret;
369}
370
371EXPORT_SYMBOL_GPL(cpuidle_enable_device);
372
373/**
374 * cpuidle_disable_device - disables idle PM for a CPU
375 * @dev: the CPU
376 *
377 * This function must be called between cpuidle_pause_and_lock and
378 * cpuidle_resume_and_unlock when used externally.
379 */
380void cpuidle_disable_device(struct cpuidle_device *dev)
381{
382	struct cpuidle_driver *drv = cpuidle_get_cpu_driver(dev);
383
384	if (!dev || !dev->enabled)
385		return;
386
387	if (!drv || !cpuidle_curr_governor)
388		return;
389
390	dev->enabled = 0;
391
392	if (cpuidle_curr_governor->disable)
393		cpuidle_curr_governor->disable(drv, dev);
394
395	cpuidle_remove_device_sysfs(dev);
396	enabled_devices--;
397}
398
399EXPORT_SYMBOL_GPL(cpuidle_disable_device);
400
401/**
402 * __cpuidle_register_device - internal register function called before register
403 * and enable routines
404 * @dev: the cpu
405 *
406 * cpuidle_lock mutex must be held before this is called
407 */
408static int __cpuidle_register_device(struct cpuidle_device *dev)
409{
410	int ret;
411	struct cpuidle_driver *drv = cpuidle_get_cpu_driver(dev);
412
413	if (!try_module_get(drv->owner))
414		return -EINVAL;
415
416	per_cpu(cpuidle_devices, dev->cpu) = dev;
417	list_add(&dev->device_list, &cpuidle_detected_devices);
418	ret = cpuidle_add_sysfs(dev);
419	if (ret)
420		goto err_sysfs;
421
422	ret = cpuidle_coupled_register_device(dev);
423	if (ret)
424		goto err_coupled;
425
426	dev->registered = 1;
427	return 0;
428
429err_coupled:
430	cpuidle_remove_sysfs(dev);
431err_sysfs:
432	list_del(&dev->device_list);
433	per_cpu(cpuidle_devices, dev->cpu) = NULL;
434	module_put(drv->owner);
435	return ret;
436}
437
438/**
439 * cpuidle_register_device - registers a CPU's idle PM feature
440 * @dev: the cpu
441 */
442int cpuidle_register_device(struct cpuidle_device *dev)
443{
444	int ret;
445
446	if (!dev)
447		return -EINVAL;
448
449	mutex_lock(&cpuidle_lock);
450
451	if ((ret = __cpuidle_register_device(dev))) {
452		mutex_unlock(&cpuidle_lock);
453		return ret;
454	}
455
456	cpuidle_enable_device(dev);
457	cpuidle_install_idle_handler();
458
459	mutex_unlock(&cpuidle_lock);
460
461	return 0;
462
463}
464
465EXPORT_SYMBOL_GPL(cpuidle_register_device);
466
467/**
468 * cpuidle_unregister_device - unregisters a CPU's idle PM feature
469 * @dev: the cpu
470 */
471void cpuidle_unregister_device(struct cpuidle_device *dev)
472{
473	struct cpuidle_driver *drv = cpuidle_get_cpu_driver(dev);
474
475	if (dev->registered == 0)
476		return;
477
478	cpuidle_pause_and_lock();
479
480	cpuidle_disable_device(dev);
481
482	cpuidle_remove_sysfs(dev);
483	list_del(&dev->device_list);
484	per_cpu(cpuidle_devices, dev->cpu) = NULL;
485
486	cpuidle_coupled_unregister_device(dev);
487
488	cpuidle_resume_and_unlock();
489
490	module_put(drv->owner);
491}
492
493EXPORT_SYMBOL_GPL(cpuidle_unregister_device);
494
495#ifdef CONFIG_SMP
496
497static void smp_callback(void *v)
498{
499	/* we already woke the CPU up, nothing more to do */
500}
501
502/*
503 * This function gets called when a part of the kernel has a new latency
504 * requirement.  This means we need to get all processors out of their C-state,
505 * and then recalculate a new suitable C-state. Just do a cross-cpu IPI; that
506 * wakes them all right up.
507 */
508static int cpuidle_latency_notify(struct notifier_block *b,
509		unsigned long l, void *v)
510{
511	smp_call_function(smp_callback, NULL, 1);
512	return NOTIFY_OK;
513}
514
515static struct notifier_block cpuidle_latency_notifier = {
516	.notifier_call = cpuidle_latency_notify,
517};
518
519static inline void latency_notifier_init(struct notifier_block *n)
520{
521	pm_qos_add_notifier(PM_QOS_CPU_DMA_LATENCY, n);
522}
523
524#else /* CONFIG_SMP */
525
526#define latency_notifier_init(x) do { } while (0)
527
528#endif /* CONFIG_SMP */
529
530/**
531 * cpuidle_init - core initializer
532 */
533static int __init cpuidle_init(void)
534{
535	int ret;
536
537	if (cpuidle_disabled())
538		return -ENODEV;
539
540	ret = cpuidle_add_interface(cpu_subsys.dev_root);
541	if (ret)
542		return ret;
543
544	latency_notifier_init(&cpuidle_latency_notifier);
545
546	return 0;
547}
548
549module_param(off, int, 0444);
550core_initcall(cpuidle_init);
551