cpuidle.c revision b032bf70df2e43149ce2b4e9a865b076c6140753 
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
20#include "cpuidle.h"
21
22DEFINE_PER_CPU(struct cpuidle_device *, cpuidle_devices);
23
24DEFINE_MUTEX(cpuidle_lock);
25LIST_HEAD(cpuidle_detected_devices);
26static void (*pm_idle_old)(void);
27
28static int enabled_devices;
29
30#if defined(CONFIG_ARCH_HAS_CPU_IDLE_WAIT)
31static void cpuidle_kick_cpus(void)
32{
33	cpu_idle_wait();
34}
35#elif defined(CONFIG_SMP)
36# error "Arch needs cpu_idle_wait() equivalent here"
37#else /* !CONFIG_ARCH_HAS_CPU_IDLE_WAIT && !CONFIG_SMP */
38static void cpuidle_kick_cpus(void) {}
39#endif
40
41static int __cpuidle_register_device(struct cpuidle_device *dev);
42
43/**
44 * cpuidle_idle_call - the main idle loop
45 *
46 * NOTE: no locks or semaphores should be used here
47 */
48static void cpuidle_idle_call(void)
49{
50	struct cpuidle_device *dev = __get_cpu_var(cpuidle_devices);
51	struct cpuidle_state *target_state;
52	int next_state;
53
54	/* check if the device is ready */
55	if (!dev || !dev->enabled) {
56		if (pm_idle_old)
57			pm_idle_old();
58		else
59			local_irq_enable();
60		return;
61	}
62
63	/* ask the governor for the next state */
64	next_state = cpuidle_curr_governor->select(dev);
65	if (need_resched())
66		return;
67	target_state = &dev->states[next_state];
68
69	/* enter the state and update stats */
70	dev->last_residency = target_state->enter(dev, target_state);
71	dev->last_state = target_state;
72	target_state->time += (unsigned long long)dev->last_residency;
73	target_state->usage++;
74
75	/* give the governor an opportunity to reflect on the outcome */
76	if (cpuidle_curr_governor->reflect)
77		cpuidle_curr_governor->reflect(dev);
78}
79
80/**
81 * cpuidle_install_idle_handler - installs the cpuidle idle loop handler
82 */
83void cpuidle_install_idle_handler(void)
84{
85	if (enabled_devices && (pm_idle != cpuidle_idle_call)) {
86		/* Make sure all changes finished before we switch to new idle */
87		smp_wmb();
88		pm_idle = cpuidle_idle_call;
89	}
90}
91
92/**
93 * cpuidle_uninstall_idle_handler - uninstalls the cpuidle idle loop handler
94 */
95void cpuidle_uninstall_idle_handler(void)
96{
97	if (enabled_devices && pm_idle_old && (pm_idle != pm_idle_old)) {
98		pm_idle = pm_idle_old;
99		cpuidle_kick_cpus();
100	}
101}
102
103/**
104 * cpuidle_pause_and_lock - temporarily disables CPUIDLE
105 */
106void cpuidle_pause_and_lock(void)
107{
108	mutex_lock(&cpuidle_lock);
109	cpuidle_uninstall_idle_handler();
110}
111
112EXPORT_SYMBOL_GPL(cpuidle_pause_and_lock);
113
114/**
115 * cpuidle_resume_and_unlock - resumes CPUIDLE operation
116 */
117void cpuidle_resume_and_unlock(void)
118{
119	cpuidle_install_idle_handler();
120	mutex_unlock(&cpuidle_lock);
121}
122
123EXPORT_SYMBOL_GPL(cpuidle_resume_and_unlock);
124
125/**
126 * cpuidle_enable_device - enables idle PM for a CPU
127 * @dev: the CPU
128 *
129 * This function must be called between cpuidle_pause_and_lock and
130 * cpuidle_resume_and_unlock when used externally.
131 */
132int cpuidle_enable_device(struct cpuidle_device *dev)
133{
134	int ret, i;
135
136	if (dev->enabled)
137		return 0;
138	if (!cpuidle_curr_driver || !cpuidle_curr_governor)
139		return -EIO;
140	if (!dev->state_count)
141		return -EINVAL;
142
143	if (dev->registered == 0) {
144		ret = __cpuidle_register_device(dev);
145		if (ret)
146			return ret;
147	}
148
149	if ((ret = cpuidle_add_state_sysfs(dev)))
150		return ret;
151
152	if (cpuidle_curr_governor->enable &&
153	    (ret = cpuidle_curr_governor->enable(dev)))
154		goto fail_sysfs;
155
156	for (i = 0; i < dev->state_count; i++) {
157		dev->states[i].usage = 0;
158		dev->states[i].time = 0;
159	}
160	dev->last_residency = 0;
161	dev->last_state = NULL;
162
163	smp_wmb();
164
165	dev->enabled = 1;
166
167	enabled_devices++;
168	return 0;
169
170fail_sysfs:
171	cpuidle_remove_state_sysfs(dev);
172
173	return ret;
174}
175
176EXPORT_SYMBOL_GPL(cpuidle_enable_device);
177
178/**
179 * cpuidle_disable_device - disables idle PM for a CPU
180 * @dev: the CPU
181 *
182 * This function must be called between cpuidle_pause_and_lock and
183 * cpuidle_resume_and_unlock when used externally.
184 */
185void cpuidle_disable_device(struct cpuidle_device *dev)
186{
187	if (!dev->enabled)
188		return;
189	if (!cpuidle_curr_driver || !cpuidle_curr_governor)
190		return;
191
192	dev->enabled = 0;
193
194	if (cpuidle_curr_governor->disable)
195		cpuidle_curr_governor->disable(dev);
196
197	cpuidle_remove_state_sysfs(dev);
198	enabled_devices--;
199}
200
201EXPORT_SYMBOL_GPL(cpuidle_disable_device);
202
203#ifdef CONFIG_ARCH_HAS_CPU_RELAX
204static int poll_idle(struct cpuidle_device *dev, struct cpuidle_state *st)
205{
206	ktime_t	t1, t2;
207	s64 diff;
208	int ret;
209
210	t1 = ktime_get();
211	local_irq_enable();
212	while (!need_resched())
213		cpu_relax();
214
215	t2 = ktime_get();
216	diff = ktime_to_us(ktime_sub(t2, t1));
217	if (diff > INT_MAX)
218		diff = INT_MAX;
219
220	ret = (int) diff;
221	return ret;
222}
223
224static void poll_idle_init(struct cpuidle_device *dev)
225{
226	struct cpuidle_state *state = &dev->states[0];
227
228	cpuidle_set_statedata(state, NULL);
229
230	snprintf(state->name, CPUIDLE_NAME_LEN, "C0");
231	snprintf(state->desc, CPUIDLE_DESC_LEN, "CPUIDLE CORE POLL IDLE");
232	state->exit_latency = 0;
233	state->target_residency = 0;
234	state->power_usage = -1;
235	state->flags = CPUIDLE_FLAG_POLL;
236	state->enter = poll_idle;
237}
238#else
239static void poll_idle_init(struct cpuidle_device *dev) {}
240#endif /* CONFIG_ARCH_HAS_CPU_RELAX */
241
242/**
243 * __cpuidle_register_device - internal register function called before register
244 * and enable routines
245 * @dev: the cpu
246 *
247 * cpuidle_lock mutex must be held before this is called
248 */
249static int __cpuidle_register_device(struct cpuidle_device *dev)
250{
251	int ret;
252	struct sys_device *sys_dev = get_cpu_sysdev((unsigned long)dev->cpu);
253
254	if (!sys_dev)
255		return -EINVAL;
256	if (!try_module_get(cpuidle_curr_driver->owner))
257		return -EINVAL;
258
259	init_completion(&dev->kobj_unregister);
260
261	poll_idle_init(dev);
262
263	per_cpu(cpuidle_devices, dev->cpu) = dev;
264	list_add(&dev->device_list, &cpuidle_detected_devices);
265	if ((ret = cpuidle_add_sysfs(sys_dev))) {
266		module_put(cpuidle_curr_driver->owner);
267		return ret;
268	}
269
270	dev->registered = 1;
271	return 0;
272}
273
274/**
275 * cpuidle_register_device - registers a CPU's idle PM feature
276 * @dev: the cpu
277 */
278int cpuidle_register_device(struct cpuidle_device *dev)
279{
280	int ret;
281
282	mutex_lock(&cpuidle_lock);
283
284	if ((ret = __cpuidle_register_device(dev))) {
285		mutex_unlock(&cpuidle_lock);
286		return ret;
287	}
288
289	cpuidle_enable_device(dev);
290	cpuidle_install_idle_handler();
291
292	mutex_unlock(&cpuidle_lock);
293
294	return 0;
295
296}
297
298EXPORT_SYMBOL_GPL(cpuidle_register_device);
299
300/**
301 * cpuidle_unregister_device - unregisters a CPU's idle PM feature
302 * @dev: the cpu
303 */
304void cpuidle_unregister_device(struct cpuidle_device *dev)
305{
306	struct sys_device *sys_dev = get_cpu_sysdev((unsigned long)dev->cpu);
307
308	if (dev->registered == 0)
309		return;
310
311	cpuidle_pause_and_lock();
312
313	cpuidle_disable_device(dev);
314
315	cpuidle_remove_sysfs(sys_dev);
316	list_del(&dev->device_list);
317	wait_for_completion(&dev->kobj_unregister);
318	per_cpu(cpuidle_devices, dev->cpu) = NULL;
319
320	cpuidle_resume_and_unlock();
321
322	module_put(cpuidle_curr_driver->owner);
323}
324
325EXPORT_SYMBOL_GPL(cpuidle_unregister_device);
326
327#ifdef CONFIG_SMP
328
329static void smp_callback(void *v)
330{
331	/* we already woke the CPU up, nothing more to do */
332}
333
334/*
335 * This function gets called when a part of the kernel has a new latency
336 * requirement.  This means we need to get all processors out of their C-state,
337 * and then recalculate a new suitable C-state. Just do a cross-cpu IPI; that
338 * wakes them all right up.
339 */
340static int cpuidle_latency_notify(struct notifier_block *b,
341		unsigned long l, void *v)
342{
343	smp_call_function(smp_callback, NULL, 1);
344	return NOTIFY_OK;
345}
346
347static struct notifier_block cpuidle_latency_notifier = {
348	.notifier_call = cpuidle_latency_notify,
349};
350
351static inline void latency_notifier_init(struct notifier_block *n)
352{
353	pm_qos_add_notifier(PM_QOS_CPU_DMA_LATENCY, n);
354}
355
356#else /* CONFIG_SMP */
357
358#define latency_notifier_init(x) do { } while (0)
359
360#endif /* CONFIG_SMP */
361
362/**
363 * cpuidle_init - core initializer
364 */
365static int __init cpuidle_init(void)
366{
367	int ret;
368
369	pm_idle_old = pm_idle;
370
371	ret = cpuidle_add_class_sysfs(&cpu_sysdev_class);
372	if (ret)
373		return ret;
374
375	latency_notifier_init(&cpuidle_latency_notifier);
376
377	return 0;
378}
379
380core_initcall(cpuidle_init);
381