cpuidle.c revision 1aef40e288acfb3cc28ff77528b34ef66683bed6 
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_driver();
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 = cpuidle_get_driver();
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	/* ask the governor for the next state */
145	next_state = cpuidle_curr_governor->select(drv, dev);
146	if (need_resched()) {
147		local_irq_enable();
148		return 0;
149	}
150
151	trace_power_start_rcuidle(POWER_CSTATE, next_state, dev->cpu);
152	trace_cpu_idle_rcuidle(next_state, dev->cpu);
153
154	if (cpuidle_state_is_coupled(dev, drv, next_state))
155		entered_state = cpuidle_enter_state_coupled(dev, drv,
156							    next_state);
157	else
158		entered_state = cpuidle_enter_state(dev, drv, next_state);
159
160	trace_power_end_rcuidle(dev->cpu);
161	trace_cpu_idle_rcuidle(PWR_EVENT_EXIT, dev->cpu);
162
163	/* give the governor an opportunity to reflect on the outcome */
164	if (cpuidle_curr_governor->reflect)
165		cpuidle_curr_governor->reflect(dev, entered_state);
166
167	return 0;
168}
169
170/**
171 * cpuidle_install_idle_handler - installs the cpuidle idle loop handler
172 */
173void cpuidle_install_idle_handler(void)
174{
175	if (enabled_devices) {
176		/* Make sure all changes finished before we switch to new idle */
177		smp_wmb();
178		initialized = 1;
179	}
180}
181
182/**
183 * cpuidle_uninstall_idle_handler - uninstalls the cpuidle idle loop handler
184 */
185void cpuidle_uninstall_idle_handler(void)
186{
187	if (enabled_devices) {
188		initialized = 0;
189		kick_all_cpus_sync();
190	}
191}
192
193/**
194 * cpuidle_pause_and_lock - temporarily disables CPUIDLE
195 */
196void cpuidle_pause_and_lock(void)
197{
198	mutex_lock(&cpuidle_lock);
199	cpuidle_uninstall_idle_handler();
200}
201
202EXPORT_SYMBOL_GPL(cpuidle_pause_and_lock);
203
204/**
205 * cpuidle_resume_and_unlock - resumes CPUIDLE operation
206 */
207void cpuidle_resume_and_unlock(void)
208{
209	cpuidle_install_idle_handler();
210	mutex_unlock(&cpuidle_lock);
211}
212
213EXPORT_SYMBOL_GPL(cpuidle_resume_and_unlock);
214
215/* Currently used in suspend/resume path to suspend cpuidle */
216void cpuidle_pause(void)
217{
218	mutex_lock(&cpuidle_lock);
219	cpuidle_uninstall_idle_handler();
220	mutex_unlock(&cpuidle_lock);
221}
222
223/* Currently used in suspend/resume path to resume cpuidle */
224void cpuidle_resume(void)
225{
226	mutex_lock(&cpuidle_lock);
227	cpuidle_install_idle_handler();
228	mutex_unlock(&cpuidle_lock);
229}
230
231/**
232 * cpuidle_wrap_enter - performs timekeeping and irqen around enter function
233 * @dev: pointer to a valid cpuidle_device object
234 * @drv: pointer to a valid cpuidle_driver object
235 * @index: index of the target cpuidle state.
236 */
237int cpuidle_wrap_enter(struct cpuidle_device *dev,
238				struct cpuidle_driver *drv, int index,
239				int (*enter)(struct cpuidle_device *dev,
240					struct cpuidle_driver *drv, int index))
241{
242	ktime_t time_start, time_end;
243	s64 diff;
244
245	time_start = ktime_get();
246
247	index = enter(dev, drv, index);
248
249	time_end = ktime_get();
250
251	local_irq_enable();
252
253	diff = ktime_to_us(ktime_sub(time_end, time_start));
254	if (diff > INT_MAX)
255		diff = INT_MAX;
256
257	dev->last_residency = (int) diff;
258
259	return index;
260}
261
262#ifdef CONFIG_ARCH_HAS_CPU_RELAX
263static int poll_idle(struct cpuidle_device *dev,
264		struct cpuidle_driver *drv, int index)
265{
266	ktime_t	t1, t2;
267	s64 diff;
268
269	t1 = ktime_get();
270	local_irq_enable();
271	while (!need_resched())
272		cpu_relax();
273
274	t2 = ktime_get();
275	diff = ktime_to_us(ktime_sub(t2, t1));
276	if (diff > INT_MAX)
277		diff = INT_MAX;
278
279	dev->last_residency = (int) diff;
280
281	return index;
282}
283
284static void poll_idle_init(struct cpuidle_driver *drv)
285{
286	struct cpuidle_state *state = &drv->states[0];
287
288	snprintf(state->name, CPUIDLE_NAME_LEN, "POLL");
289	snprintf(state->desc, CPUIDLE_DESC_LEN, "CPUIDLE CORE POLL IDLE");
290	state->exit_latency = 0;
291	state->target_residency = 0;
292	state->power_usage = -1;
293	state->flags = 0;
294	state->enter = poll_idle;
295	state->disabled = false;
296}
297#else
298static void poll_idle_init(struct cpuidle_driver *drv) {}
299#endif /* CONFIG_ARCH_HAS_CPU_RELAX */
300
301/**
302 * cpuidle_enable_device - enables idle PM for a CPU
303 * @dev: the CPU
304 *
305 * This function must be called between cpuidle_pause_and_lock and
306 * cpuidle_resume_and_unlock when used externally.
307 */
308int cpuidle_enable_device(struct cpuidle_device *dev)
309{
310	int ret, i;
311	struct cpuidle_driver *drv = cpuidle_get_driver();
312
313	if (!dev)
314		return -EINVAL;
315
316	if (dev->enabled)
317		return 0;
318	if (!drv || !cpuidle_curr_governor)
319		return -EIO;
320	if (!dev->state_count)
321		dev->state_count = drv->state_count;
322
323	if (dev->registered == 0) {
324		ret = __cpuidle_register_device(dev);
325		if (ret)
326			return ret;
327	}
328
329	cpuidle_enter_ops = drv->en_core_tk_irqen ?
330		cpuidle_enter_tk : cpuidle_enter;
331
332	poll_idle_init(drv);
333
334	if ((ret = cpuidle_add_state_sysfs(dev)))
335		return ret;
336
337	if (cpuidle_curr_governor->enable &&
338	    (ret = cpuidle_curr_governor->enable(drv, dev)))
339		goto fail_sysfs;
340
341	for (i = 0; i < dev->state_count; i++) {
342		dev->states_usage[i].usage = 0;
343		dev->states_usage[i].time = 0;
344	}
345	dev->last_residency = 0;
346
347	smp_wmb();
348
349	dev->enabled = 1;
350
351	enabled_devices++;
352	return 0;
353
354fail_sysfs:
355	cpuidle_remove_state_sysfs(dev);
356
357	return ret;
358}
359
360EXPORT_SYMBOL_GPL(cpuidle_enable_device);
361
362/**
363 * cpuidle_disable_device - disables idle PM for a CPU
364 * @dev: the CPU
365 *
366 * This function must be called between cpuidle_pause_and_lock and
367 * cpuidle_resume_and_unlock when used externally.
368 */
369void cpuidle_disable_device(struct cpuidle_device *dev)
370{
371	if (!dev || !dev->enabled)
372		return;
373	if (!cpuidle_get_driver() || !cpuidle_curr_governor)
374		return;
375
376	dev->enabled = 0;
377
378	if (cpuidle_curr_governor->disable)
379		cpuidle_curr_governor->disable(cpuidle_get_driver(), dev);
380
381	cpuidle_remove_state_sysfs(dev);
382	enabled_devices--;
383}
384
385EXPORT_SYMBOL_GPL(cpuidle_disable_device);
386
387/**
388 * __cpuidle_register_device - internal register function called before register
389 * and enable routines
390 * @dev: the cpu
391 *
392 * cpuidle_lock mutex must be held before this is called
393 */
394static int __cpuidle_register_device(struct cpuidle_device *dev)
395{
396	int ret;
397	struct cpuidle_driver *cpuidle_driver = cpuidle_get_driver();
398
399	if (!try_module_get(cpuidle_driver->owner))
400		return -EINVAL;
401
402	init_completion(&dev->kobj_unregister);
403
404	per_cpu(cpuidle_devices, dev->cpu) = dev;
405	list_add(&dev->device_list, &cpuidle_detected_devices);
406	ret = cpuidle_add_sysfs(dev);
407	if (ret)
408		goto err_sysfs;
409
410	ret = cpuidle_coupled_register_device(dev);
411	if (ret)
412		goto err_coupled;
413
414	dev->registered = 1;
415	return 0;
416
417err_coupled:
418	cpuidle_remove_sysfs(dev);
419	wait_for_completion(&dev->kobj_unregister);
420err_sysfs:
421	list_del(&dev->device_list);
422	per_cpu(cpuidle_devices, dev->cpu) = NULL;
423	module_put(cpuidle_driver->owner);
424	return ret;
425}
426
427/**
428 * cpuidle_register_device - registers a CPU's idle PM feature
429 * @dev: the cpu
430 */
431int cpuidle_register_device(struct cpuidle_device *dev)
432{
433	int ret;
434
435	if (!dev)
436		return -EINVAL;
437
438	mutex_lock(&cpuidle_lock);
439
440	if ((ret = __cpuidle_register_device(dev))) {
441		mutex_unlock(&cpuidle_lock);
442		return ret;
443	}
444
445	cpuidle_enable_device(dev);
446	cpuidle_install_idle_handler();
447
448	mutex_unlock(&cpuidle_lock);
449
450	return 0;
451
452}
453
454EXPORT_SYMBOL_GPL(cpuidle_register_device);
455
456/**
457 * cpuidle_unregister_device - unregisters a CPU's idle PM feature
458 * @dev: the cpu
459 */
460void cpuidle_unregister_device(struct cpuidle_device *dev)
461{
462	struct cpuidle_driver *cpuidle_driver = cpuidle_get_driver();
463
464	if (dev->registered == 0)
465		return;
466
467	cpuidle_pause_and_lock();
468
469	cpuidle_disable_device(dev);
470
471	cpuidle_remove_sysfs(dev);
472	list_del(&dev->device_list);
473	wait_for_completion(&dev->kobj_unregister);
474	per_cpu(cpuidle_devices, dev->cpu) = NULL;
475
476	cpuidle_coupled_unregister_device(dev);
477
478	cpuidle_resume_and_unlock();
479
480	module_put(cpuidle_driver->owner);
481}
482
483EXPORT_SYMBOL_GPL(cpuidle_unregister_device);
484
485#ifdef CONFIG_SMP
486
487static void smp_callback(void *v)
488{
489	/* we already woke the CPU up, nothing more to do */
490}
491
492/*
493 * This function gets called when a part of the kernel has a new latency
494 * requirement.  This means we need to get all processors out of their C-state,
495 * and then recalculate a new suitable C-state. Just do a cross-cpu IPI; that
496 * wakes them all right up.
497 */
498static int cpuidle_latency_notify(struct notifier_block *b,
499		unsigned long l, void *v)
500{
501	smp_call_function(smp_callback, NULL, 1);
502	return NOTIFY_OK;
503}
504
505static struct notifier_block cpuidle_latency_notifier = {
506	.notifier_call = cpuidle_latency_notify,
507};
508
509static inline void latency_notifier_init(struct notifier_block *n)
510{
511	pm_qos_add_notifier(PM_QOS_CPU_DMA_LATENCY, n);
512}
513
514#else /* CONFIG_SMP */
515
516#define latency_notifier_init(x) do { } while (0)
517
518#endif /* CONFIG_SMP */
519
520/**
521 * cpuidle_init - core initializer
522 */
523static int __init cpuidle_init(void)
524{
525	int ret;
526
527	if (cpuidle_disabled())
528		return -ENODEV;
529
530	ret = cpuidle_add_interface(cpu_subsys.dev_root);
531	if (ret)
532		return ret;
533
534	latency_notifier_init(&cpuidle_latency_notifier);
535
536	return 0;
537}
538
539module_param(off, int, 0444);
540core_initcall(cpuidle_init);
541