cpuidle.c revision 4202735e8ab6ecfb0381631a0d0b58fefe0bd4e2 
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_params.h>
16#include <linux/cpu.h>
17#include <linux/cpuidle.h>
18#include <linux/ktime.h>
19#include <linux/hrtimer.h>
20#include <trace/events/power.h>
21
22#include "cpuidle.h"
23
24DEFINE_PER_CPU(struct cpuidle_device *, cpuidle_devices);
25
26DEFINE_MUTEX(cpuidle_lock);
27LIST_HEAD(cpuidle_detected_devices);
28
29static int enabled_devices;
30static int off __read_mostly;
31static int initialized __read_mostly;
32
33int cpuidle_disabled(void)
34{
35	return off;
36}
37void disable_cpuidle(void)
38{
39	off = 1;
40}
41
42#if defined(CONFIG_ARCH_HAS_CPU_IDLE_WAIT)
43static void cpuidle_kick_cpus(void)
44{
45	cpu_idle_wait();
46}
47#elif defined(CONFIG_SMP)
48# error "Arch needs cpu_idle_wait() equivalent here"
49#else /* !CONFIG_ARCH_HAS_CPU_IDLE_WAIT && !CONFIG_SMP */
50static void cpuidle_kick_cpus(void) {}
51#endif
52
53static int __cpuidle_register_device(struct cpuidle_device *dev);
54
55/**
56 * cpuidle_idle_call - the main idle loop
57 *
58 * NOTE: no locks or semaphores should be used here
59 * return non-zero on failure
60 */
61int cpuidle_idle_call(void)
62{
63	struct cpuidle_device *dev = __this_cpu_read(cpuidle_devices);
64	struct cpuidle_state *target_state;
65	int next_state, entered_state;
66
67	if (off)
68		return -ENODEV;
69
70	if (!initialized)
71		return -ENODEV;
72
73	/* check if the device is ready */
74	if (!dev || !dev->enabled)
75		return -EBUSY;
76
77#if 0
78	/* shows regressions, re-enable for 2.6.29 */
79	/*
80	 * run any timers that can be run now, at this point
81	 * before calculating the idle duration etc.
82	 */
83	hrtimer_peek_ahead_timers();
84#endif
85
86	/* ask the governor for the next state */
87	next_state = cpuidle_curr_governor->select(dev);
88	if (need_resched()) {
89		local_irq_enable();
90		return 0;
91	}
92
93	target_state = &dev->states[next_state];
94
95	trace_power_start(POWER_CSTATE, next_state, dev->cpu);
96	trace_cpu_idle(next_state, dev->cpu);
97
98	entered_state = target_state->enter(dev, next_state);
99
100	trace_power_end(dev->cpu);
101	trace_cpu_idle(PWR_EVENT_EXIT, dev->cpu);
102
103	if (entered_state >= 0) {
104		/* Update cpuidle counters */
105		/* This can be moved to within driver enter routine
106		 * but that results in multiple copies of same code.
107		 */
108		dev->states_usage[entered_state].time +=
109				(unsigned long long)dev->last_residency;
110		dev->states_usage[entered_state].usage++;
111	}
112
113	/* give the governor an opportunity to reflect on the outcome */
114	if (cpuidle_curr_governor->reflect)
115		cpuidle_curr_governor->reflect(dev, entered_state);
116
117	return 0;
118}
119
120/**
121 * cpuidle_install_idle_handler - installs the cpuidle idle loop handler
122 */
123void cpuidle_install_idle_handler(void)
124{
125	if (enabled_devices) {
126		/* Make sure all changes finished before we switch to new idle */
127		smp_wmb();
128		initialized = 1;
129	}
130}
131
132/**
133 * cpuidle_uninstall_idle_handler - uninstalls the cpuidle idle loop handler
134 */
135void cpuidle_uninstall_idle_handler(void)
136{
137	if (enabled_devices) {
138		initialized = 0;
139		cpuidle_kick_cpus();
140	}
141}
142
143/**
144 * cpuidle_pause_and_lock - temporarily disables CPUIDLE
145 */
146void cpuidle_pause_and_lock(void)
147{
148	mutex_lock(&cpuidle_lock);
149	cpuidle_uninstall_idle_handler();
150}
151
152EXPORT_SYMBOL_GPL(cpuidle_pause_and_lock);
153
154/**
155 * cpuidle_resume_and_unlock - resumes CPUIDLE operation
156 */
157void cpuidle_resume_and_unlock(void)
158{
159	cpuidle_install_idle_handler();
160	mutex_unlock(&cpuidle_lock);
161}
162
163EXPORT_SYMBOL_GPL(cpuidle_resume_and_unlock);
164
165#ifdef CONFIG_ARCH_HAS_CPU_RELAX
166static int poll_idle(struct cpuidle_device *dev, int index)
167{
168	ktime_t	t1, t2;
169	s64 diff;
170
171	t1 = ktime_get();
172	local_irq_enable();
173	while (!need_resched())
174		cpu_relax();
175
176	t2 = ktime_get();
177	diff = ktime_to_us(ktime_sub(t2, t1));
178	if (diff > INT_MAX)
179		diff = INT_MAX;
180
181	dev->last_residency = (int) diff;
182
183	return index;
184}
185
186static void poll_idle_init(struct cpuidle_device *dev)
187{
188	struct cpuidle_state *state = &dev->states[0];
189	struct cpuidle_state_usage *state_usage = &dev->states_usage[0];
190
191	cpuidle_set_statedata(state_usage, NULL);
192
193	snprintf(state->name, CPUIDLE_NAME_LEN, "POLL");
194	snprintf(state->desc, CPUIDLE_DESC_LEN, "CPUIDLE CORE POLL IDLE");
195	state->exit_latency = 0;
196	state->target_residency = 0;
197	state->power_usage = -1;
198	state->flags = 0;
199	state->enter = poll_idle;
200}
201#else
202static void poll_idle_init(struct cpuidle_device *dev) {}
203#endif /* CONFIG_ARCH_HAS_CPU_RELAX */
204
205/**
206 * cpuidle_enable_device - enables idle PM for a CPU
207 * @dev: the CPU
208 *
209 * This function must be called between cpuidle_pause_and_lock and
210 * cpuidle_resume_and_unlock when used externally.
211 */
212int cpuidle_enable_device(struct cpuidle_device *dev)
213{
214	int ret, i;
215
216	if (dev->enabled)
217		return 0;
218	if (!cpuidle_get_driver() || !cpuidle_curr_governor)
219		return -EIO;
220	if (!dev->state_count)
221		return -EINVAL;
222
223	if (dev->registered == 0) {
224		ret = __cpuidle_register_device(dev);
225		if (ret)
226			return ret;
227	}
228
229	poll_idle_init(dev);
230
231	if ((ret = cpuidle_add_state_sysfs(dev)))
232		return ret;
233
234	if (cpuidle_curr_governor->enable &&
235	    (ret = cpuidle_curr_governor->enable(dev)))
236		goto fail_sysfs;
237
238	for (i = 0; i < dev->state_count; i++) {
239		dev->states_usage[i].usage = 0;
240		dev->states_usage[i].time = 0;
241	}
242	dev->last_residency = 0;
243
244	smp_wmb();
245
246	dev->enabled = 1;
247
248	enabled_devices++;
249	return 0;
250
251fail_sysfs:
252	cpuidle_remove_state_sysfs(dev);
253
254	return ret;
255}
256
257EXPORT_SYMBOL_GPL(cpuidle_enable_device);
258
259/**
260 * cpuidle_disable_device - disables idle PM for a CPU
261 * @dev: the CPU
262 *
263 * This function must be called between cpuidle_pause_and_lock and
264 * cpuidle_resume_and_unlock when used externally.
265 */
266void cpuidle_disable_device(struct cpuidle_device *dev)
267{
268	if (!dev->enabled)
269		return;
270	if (!cpuidle_get_driver() || !cpuidle_curr_governor)
271		return;
272
273	dev->enabled = 0;
274
275	if (cpuidle_curr_governor->disable)
276		cpuidle_curr_governor->disable(dev);
277
278	cpuidle_remove_state_sysfs(dev);
279	enabled_devices--;
280}
281
282EXPORT_SYMBOL_GPL(cpuidle_disable_device);
283
284/**
285 * __cpuidle_register_device - internal register function called before register
286 * and enable routines
287 * @dev: the cpu
288 *
289 * cpuidle_lock mutex must be held before this is called
290 */
291static int __cpuidle_register_device(struct cpuidle_device *dev)
292{
293	int ret;
294	struct sys_device *sys_dev = get_cpu_sysdev((unsigned long)dev->cpu);
295	struct cpuidle_driver *cpuidle_driver = cpuidle_get_driver();
296
297	if (!sys_dev)
298		return -EINVAL;
299	if (!try_module_get(cpuidle_driver->owner))
300		return -EINVAL;
301
302	init_completion(&dev->kobj_unregister);
303
304	/*
305	 * cpuidle driver should set the dev->power_specified bit
306	 * before registering the device if the driver provides
307	 * power_usage numbers.
308	 *
309	 * For those devices whose ->power_specified is not set,
310	 * we fill in power_usage with decreasing values as the
311	 * cpuidle code has an implicit assumption that state Cn
312	 * uses less power than C(n-1).
313	 *
314	 * With CONFIG_ARCH_HAS_CPU_RELAX, C0 is already assigned
315	 * an power value of -1.  So we use -2, -3, etc, for other
316	 * c-states.
317	 */
318	if (!dev->power_specified) {
319		int i;
320		for (i = CPUIDLE_DRIVER_STATE_START; i < dev->state_count; i++)
321			dev->states[i].power_usage = -1 - i;
322	}
323
324	per_cpu(cpuidle_devices, dev->cpu) = dev;
325	list_add(&dev->device_list, &cpuidle_detected_devices);
326	if ((ret = cpuidle_add_sysfs(sys_dev))) {
327		module_put(cpuidle_driver->owner);
328		return ret;
329	}
330
331	dev->registered = 1;
332	return 0;
333}
334
335/**
336 * cpuidle_register_device - registers a CPU's idle PM feature
337 * @dev: the cpu
338 */
339int cpuidle_register_device(struct cpuidle_device *dev)
340{
341	int ret;
342
343	mutex_lock(&cpuidle_lock);
344
345	if ((ret = __cpuidle_register_device(dev))) {
346		mutex_unlock(&cpuidle_lock);
347		return ret;
348	}
349
350	cpuidle_enable_device(dev);
351	cpuidle_install_idle_handler();
352
353	mutex_unlock(&cpuidle_lock);
354
355	return 0;
356
357}
358
359EXPORT_SYMBOL_GPL(cpuidle_register_device);
360
361/**
362 * cpuidle_unregister_device - unregisters a CPU's idle PM feature
363 * @dev: the cpu
364 */
365void cpuidle_unregister_device(struct cpuidle_device *dev)
366{
367	struct sys_device *sys_dev = get_cpu_sysdev((unsigned long)dev->cpu);
368	struct cpuidle_driver *cpuidle_driver = cpuidle_get_driver();
369
370	if (dev->registered == 0)
371		return;
372
373	cpuidle_pause_and_lock();
374
375	cpuidle_disable_device(dev);
376
377	cpuidle_remove_sysfs(sys_dev);
378	list_del(&dev->device_list);
379	wait_for_completion(&dev->kobj_unregister);
380	per_cpu(cpuidle_devices, dev->cpu) = NULL;
381
382	cpuidle_resume_and_unlock();
383
384	module_put(cpuidle_driver->owner);
385}
386
387EXPORT_SYMBOL_GPL(cpuidle_unregister_device);
388
389#ifdef CONFIG_SMP
390
391static void smp_callback(void *v)
392{
393	/* we already woke the CPU up, nothing more to do */
394}
395
396/*
397 * This function gets called when a part of the kernel has a new latency
398 * requirement.  This means we need to get all processors out of their C-state,
399 * and then recalculate a new suitable C-state. Just do a cross-cpu IPI; that
400 * wakes them all right up.
401 */
402static int cpuidle_latency_notify(struct notifier_block *b,
403		unsigned long l, void *v)
404{
405	smp_call_function(smp_callback, NULL, 1);
406	return NOTIFY_OK;
407}
408
409static struct notifier_block cpuidle_latency_notifier = {
410	.notifier_call = cpuidle_latency_notify,
411};
412
413static inline void latency_notifier_init(struct notifier_block *n)
414{
415	pm_qos_add_notifier(PM_QOS_CPU_DMA_LATENCY, n);
416}
417
418#else /* CONFIG_SMP */
419
420#define latency_notifier_init(x) do { } while (0)
421
422#endif /* CONFIG_SMP */
423
424/**
425 * cpuidle_init - core initializer
426 */
427static int __init cpuidle_init(void)
428{
429	int ret;
430
431	if (cpuidle_disabled())
432		return -ENODEV;
433
434	ret = cpuidle_add_class_sysfs(&cpu_sysdev_class);
435	if (ret)
436		return ret;
437
438	latency_notifier_init(&cpuidle_latency_notifier);
439
440	return 0;
441}
442
443module_param(off, int, 0444);
444core_initcall(cpuidle_init);
445