cpuidle.c revision a474a515497ef3566cfc17a2cab3d54d6d50ff1c 
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 += dev->last_residency;
113		dev->states_usage[entered_state].usage++;
114	} else {
115		dev->last_residency = 0;
116	}
117
118	return entered_state;
119}
120
121/**
122 * cpuidle_idle_call - the main idle loop
123 *
124 * NOTE: no locks or semaphores should be used here
125 * return non-zero on failure
126 */
127int cpuidle_idle_call(void)
128{
129	struct cpuidle_device *dev = __this_cpu_read(cpuidle_devices);
130	struct cpuidle_driver *drv;
131	int next_state, entered_state;
132
133	if (off)
134		return -ENODEV;
135
136	if (!initialized)
137		return -ENODEV;
138
139	/* check if the device is ready */
140	if (!dev || !dev->enabled)
141		return -EBUSY;
142
143	drv = cpuidle_get_cpu_driver(dev);
144
145	/* ask the governor for the next state */
146	next_state = cpuidle_curr_governor->select(drv, dev);
147	if (need_resched()) {
148		dev->last_residency = 0;
149		/* give the governor an opportunity to reflect on the outcome */
150		if (cpuidle_curr_governor->reflect)
151			cpuidle_curr_governor->reflect(dev, next_state);
152		local_irq_enable();
153		return 0;
154	}
155
156	trace_power_start_rcuidle(POWER_CSTATE, next_state, dev->cpu);
157	trace_cpu_idle_rcuidle(next_state, dev->cpu);
158
159	if (cpuidle_state_is_coupled(dev, drv, next_state))
160		entered_state = cpuidle_enter_state_coupled(dev, drv,
161							    next_state);
162	else
163		entered_state = cpuidle_enter_state(dev, drv, next_state);
164
165	trace_power_end_rcuidle(dev->cpu);
166	trace_cpu_idle_rcuidle(PWR_EVENT_EXIT, dev->cpu);
167
168	/* give the governor an opportunity to reflect on the outcome */
169	if (cpuidle_curr_governor->reflect)
170		cpuidle_curr_governor->reflect(dev, entered_state);
171
172	return 0;
173}
174
175/**
176 * cpuidle_install_idle_handler - installs the cpuidle idle loop handler
177 */
178void cpuidle_install_idle_handler(void)
179{
180	if (enabled_devices) {
181		/* Make sure all changes finished before we switch to new idle */
182		smp_wmb();
183		initialized = 1;
184	}
185}
186
187/**
188 * cpuidle_uninstall_idle_handler - uninstalls the cpuidle idle loop handler
189 */
190void cpuidle_uninstall_idle_handler(void)
191{
192	if (enabled_devices) {
193		initialized = 0;
194		kick_all_cpus_sync();
195	}
196}
197
198/**
199 * cpuidle_pause_and_lock - temporarily disables CPUIDLE
200 */
201void cpuidle_pause_and_lock(void)
202{
203	mutex_lock(&cpuidle_lock);
204	cpuidle_uninstall_idle_handler();
205}
206
207EXPORT_SYMBOL_GPL(cpuidle_pause_and_lock);
208
209/**
210 * cpuidle_resume_and_unlock - resumes CPUIDLE operation
211 */
212void cpuidle_resume_and_unlock(void)
213{
214	cpuidle_install_idle_handler();
215	mutex_unlock(&cpuidle_lock);
216}
217
218EXPORT_SYMBOL_GPL(cpuidle_resume_and_unlock);
219
220/* Currently used in suspend/resume path to suspend cpuidle */
221void cpuidle_pause(void)
222{
223	mutex_lock(&cpuidle_lock);
224	cpuidle_uninstall_idle_handler();
225	mutex_unlock(&cpuidle_lock);
226}
227
228/* Currently used in suspend/resume path to resume cpuidle */
229void cpuidle_resume(void)
230{
231	mutex_lock(&cpuidle_lock);
232	cpuidle_install_idle_handler();
233	mutex_unlock(&cpuidle_lock);
234}
235
236/**
237 * cpuidle_wrap_enter - performs timekeeping and irqen around enter function
238 * @dev: pointer to a valid cpuidle_device object
239 * @drv: pointer to a valid cpuidle_driver object
240 * @index: index of the target cpuidle state.
241 */
242int cpuidle_wrap_enter(struct cpuidle_device *dev,
243				struct cpuidle_driver *drv, int index,
244				int (*enter)(struct cpuidle_device *dev,
245					struct cpuidle_driver *drv, int index))
246{
247	ktime_t time_start, time_end;
248	s64 diff;
249
250	time_start = ktime_get();
251
252	index = enter(dev, drv, index);
253
254	time_end = ktime_get();
255
256	local_irq_enable();
257
258	diff = ktime_to_us(ktime_sub(time_end, time_start));
259	if (diff > INT_MAX)
260		diff = INT_MAX;
261
262	dev->last_residency = (int) diff;
263
264	return index;
265}
266
267#ifdef CONFIG_ARCH_HAS_CPU_RELAX
268static int poll_idle(struct cpuidle_device *dev,
269		struct cpuidle_driver *drv, int index)
270{
271	ktime_t	t1, t2;
272	s64 diff;
273
274	t1 = ktime_get();
275	local_irq_enable();
276	while (!need_resched())
277		cpu_relax();
278
279	t2 = ktime_get();
280	diff = ktime_to_us(ktime_sub(t2, t1));
281	if (diff > INT_MAX)
282		diff = INT_MAX;
283
284	dev->last_residency = (int) diff;
285
286	return index;
287}
288
289static void poll_idle_init(struct cpuidle_driver *drv)
290{
291	struct cpuidle_state *state = &drv->states[0];
292
293	snprintf(state->name, CPUIDLE_NAME_LEN, "POLL");
294	snprintf(state->desc, CPUIDLE_DESC_LEN, "CPUIDLE CORE POLL IDLE");
295	state->exit_latency = 0;
296	state->target_residency = 0;
297	state->power_usage = -1;
298	state->flags = 0;
299	state->enter = poll_idle;
300	state->disabled = false;
301}
302#else
303static void poll_idle_init(struct cpuidle_driver *drv) {}
304#endif /* CONFIG_ARCH_HAS_CPU_RELAX */
305
306/**
307 * cpuidle_enable_device - enables idle PM for a CPU
308 * @dev: the CPU
309 *
310 * This function must be called between cpuidle_pause_and_lock and
311 * cpuidle_resume_and_unlock when used externally.
312 */
313int cpuidle_enable_device(struct cpuidle_device *dev)
314{
315	int ret, i;
316	struct cpuidle_driver *drv;
317
318	if (!dev)
319		return -EINVAL;
320
321	if (dev->enabled)
322		return 0;
323
324	drv = cpuidle_get_cpu_driver(dev);
325
326	if (!drv || !cpuidle_curr_governor)
327		return -EIO;
328
329	if (!dev->state_count)
330		dev->state_count = drv->state_count;
331
332	if (dev->registered == 0) {
333		ret = __cpuidle_register_device(dev);
334		if (ret)
335			return ret;
336	}
337
338	cpuidle_enter_ops = drv->en_core_tk_irqen ?
339		cpuidle_enter_tk : cpuidle_enter;
340
341	poll_idle_init(drv);
342
343	ret = cpuidle_add_device_sysfs(dev);
344	if (ret)
345		return ret;
346
347	if (cpuidle_curr_governor->enable &&
348	    (ret = cpuidle_curr_governor->enable(drv, dev)))
349		goto fail_sysfs;
350
351	for (i = 0; i < dev->state_count; i++) {
352		dev->states_usage[i].usage = 0;
353		dev->states_usage[i].time = 0;
354	}
355	dev->last_residency = 0;
356
357	smp_wmb();
358
359	dev->enabled = 1;
360
361	enabled_devices++;
362	return 0;
363
364fail_sysfs:
365	cpuidle_remove_device_sysfs(dev);
366
367	return ret;
368}
369
370EXPORT_SYMBOL_GPL(cpuidle_enable_device);
371
372/**
373 * cpuidle_disable_device - disables idle PM for a CPU
374 * @dev: the CPU
375 *
376 * This function must be called between cpuidle_pause_and_lock and
377 * cpuidle_resume_and_unlock when used externally.
378 */
379void cpuidle_disable_device(struct cpuidle_device *dev)
380{
381	struct cpuidle_driver *drv = cpuidle_get_cpu_driver(dev);
382
383	if (!dev || !dev->enabled)
384		return;
385
386	if (!drv || !cpuidle_curr_governor)
387		return;
388
389	dev->enabled = 0;
390
391	if (cpuidle_curr_governor->disable)
392		cpuidle_curr_governor->disable(drv, dev);
393
394	cpuidle_remove_device_sysfs(dev);
395	enabled_devices--;
396}
397
398EXPORT_SYMBOL_GPL(cpuidle_disable_device);
399
400/**
401 * __cpuidle_register_device - internal register function called before register
402 * and enable routines
403 * @dev: the cpu
404 *
405 * cpuidle_lock mutex must be held before this is called
406 */
407static int __cpuidle_register_device(struct cpuidle_device *dev)
408{
409	int ret;
410	struct cpuidle_driver *drv = cpuidle_get_cpu_driver(dev);
411
412	if (!try_module_get(drv->owner))
413		return -EINVAL;
414
415	per_cpu(cpuidle_devices, dev->cpu) = dev;
416	list_add(&dev->device_list, &cpuidle_detected_devices);
417	ret = cpuidle_add_sysfs(dev);
418	if (ret)
419		goto err_sysfs;
420
421	ret = cpuidle_coupled_register_device(dev);
422	if (ret)
423		goto err_coupled;
424
425	dev->registered = 1;
426	return 0;
427
428err_coupled:
429	cpuidle_remove_sysfs(dev);
430err_sysfs:
431	list_del(&dev->device_list);
432	per_cpu(cpuidle_devices, dev->cpu) = NULL;
433	module_put(drv->owner);
434	return ret;
435}
436
437/**
438 * cpuidle_register_device - registers a CPU's idle PM feature
439 * @dev: the cpu
440 */
441int cpuidle_register_device(struct cpuidle_device *dev)
442{
443	int ret;
444
445	if (!dev)
446		return -EINVAL;
447
448	mutex_lock(&cpuidle_lock);
449
450	if ((ret = __cpuidle_register_device(dev))) {
451		mutex_unlock(&cpuidle_lock);
452		return ret;
453	}
454
455	cpuidle_enable_device(dev);
456	cpuidle_install_idle_handler();
457
458	mutex_unlock(&cpuidle_lock);
459
460	return 0;
461
462}
463
464EXPORT_SYMBOL_GPL(cpuidle_register_device);
465
466/**
467 * cpuidle_unregister_device - unregisters a CPU's idle PM feature
468 * @dev: the cpu
469 */
470void cpuidle_unregister_device(struct cpuidle_device *dev)
471{
472	struct cpuidle_driver *drv = cpuidle_get_cpu_driver(dev);
473
474	if (dev->registered == 0)
475		return;
476
477	cpuidle_pause_and_lock();
478
479	cpuidle_disable_device(dev);
480
481	cpuidle_remove_sysfs(dev);
482	list_del(&dev->device_list);
483	per_cpu(cpuidle_devices, dev->cpu) = NULL;
484
485	cpuidle_coupled_unregister_device(dev);
486
487	cpuidle_resume_and_unlock();
488
489	module_put(drv->owner);
490}
491
492EXPORT_SYMBOL_GPL(cpuidle_unregister_device);
493
494#ifdef CONFIG_SMP
495
496static void smp_callback(void *v)
497{
498	/* we already woke the CPU up, nothing more to do */
499}
500
501/*
502 * This function gets called when a part of the kernel has a new latency
503 * requirement.  This means we need to get all processors out of their C-state,
504 * and then recalculate a new suitable C-state. Just do a cross-cpu IPI; that
505 * wakes them all right up.
506 */
507static int cpuidle_latency_notify(struct notifier_block *b,
508		unsigned long l, void *v)
509{
510	smp_call_function(smp_callback, NULL, 1);
511	return NOTIFY_OK;
512}
513
514static struct notifier_block cpuidle_latency_notifier = {
515	.notifier_call = cpuidle_latency_notify,
516};
517
518static inline void latency_notifier_init(struct notifier_block *n)
519{
520	pm_qos_add_notifier(PM_QOS_CPU_DMA_LATENCY, n);
521}
522
523#else /* CONFIG_SMP */
524
525#define latency_notifier_init(x) do { } while (0)
526
527#endif /* CONFIG_SMP */
528
529/**
530 * cpuidle_init - core initializer
531 */
532static int __init cpuidle_init(void)
533{
534	int ret;
535
536	if (cpuidle_disabled())
537		return -ENODEV;
538
539	ret = cpuidle_add_interface(cpu_subsys.dev_root);
540	if (ret)
541		return ret;
542
543	latency_notifier_init(&cpuidle_latency_notifier);
544
545	return 0;
546}
547
548module_param(off, int, 0444);
549core_initcall(cpuidle_init);
550