cpuidle.c revision f757397097d0713c949af76dccabb65a2785782e 
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/latency.h>
16#include <linux/cpu.h>
17#include <linux/cpuidle.h>
18
19#include "cpuidle.h"
20
21DEFINE_PER_CPU(struct cpuidle_device *, cpuidle_devices);
22
23DEFINE_MUTEX(cpuidle_lock);
24LIST_HEAD(cpuidle_detected_devices);
25static void (*pm_idle_old)(void);
26
27static int enabled_devices;
28
29/**
30 * cpuidle_idle_call - the main idle loop
31 *
32 * NOTE: no locks or semaphores should be used here
33 */
34static void cpuidle_idle_call(void)
35{
36	struct cpuidle_device *dev = __get_cpu_var(cpuidle_devices);
37	struct cpuidle_state *target_state;
38	int next_state;
39
40	/* check if the device is ready */
41	if (!dev || !dev->enabled) {
42		if (pm_idle_old)
43			pm_idle_old();
44		else
45			local_irq_enable();
46		return;
47	}
48
49	/* ask the governor for the next state */
50	next_state = cpuidle_curr_governor->select(dev);
51	if (need_resched())
52		return;
53	target_state = &dev->states[next_state];
54
55	/* enter the state and update stats */
56	dev->last_residency = target_state->enter(dev, target_state);
57	dev->last_state = target_state;
58	target_state->time += dev->last_residency;
59	target_state->usage++;
60
61	/* give the governor an opportunity to reflect on the outcome */
62	if (cpuidle_curr_governor->reflect)
63		cpuidle_curr_governor->reflect(dev);
64}
65
66/**
67 * cpuidle_install_idle_handler - installs the cpuidle idle loop handler
68 */
69void cpuidle_install_idle_handler(void)
70{
71	if (enabled_devices && (pm_idle != cpuidle_idle_call)) {
72		/* Make sure all changes finished before we switch to new idle */
73		smp_wmb();
74		pm_idle = cpuidle_idle_call;
75	}
76}
77
78/**
79 * cpuidle_uninstall_idle_handler - uninstalls the cpuidle idle loop handler
80 */
81void cpuidle_uninstall_idle_handler(void)
82{
83	if (enabled_devices && (pm_idle != pm_idle_old)) {
84		pm_idle = pm_idle_old;
85		cpuidle_kick_cpus();
86	}
87}
88
89/**
90 * cpuidle_pause_and_lock - temporarily disables CPUIDLE
91 */
92void cpuidle_pause_and_lock(void)
93{
94	mutex_lock(&cpuidle_lock);
95	cpuidle_uninstall_idle_handler();
96}
97
98EXPORT_SYMBOL_GPL(cpuidle_pause_and_lock);
99
100/**
101 * cpuidle_resume_and_unlock - resumes CPUIDLE operation
102 */
103void cpuidle_resume_and_unlock(void)
104{
105	cpuidle_install_idle_handler();
106	mutex_unlock(&cpuidle_lock);
107}
108
109EXPORT_SYMBOL_GPL(cpuidle_resume_and_unlock);
110
111/**
112 * cpuidle_enable_device - enables idle PM for a CPU
113 * @dev: the CPU
114 *
115 * This function must be called between cpuidle_pause_and_lock and
116 * cpuidle_resume_and_unlock when used externally.
117 */
118int cpuidle_enable_device(struct cpuidle_device *dev)
119{
120	int ret, i;
121
122	if (dev->enabled)
123		return 0;
124	if (!cpuidle_curr_driver || !cpuidle_curr_governor)
125		return -EIO;
126	if (!dev->state_count)
127		return -EINVAL;
128
129	if ((ret = cpuidle_add_state_sysfs(dev)))
130		return ret;
131
132	if (cpuidle_curr_governor->enable &&
133	    (ret = cpuidle_curr_governor->enable(dev)))
134		goto fail_sysfs;
135
136	for (i = 0; i < dev->state_count; i++) {
137		dev->states[i].usage = 0;
138		dev->states[i].time = 0;
139	}
140	dev->last_residency = 0;
141	dev->last_state = NULL;
142
143	smp_wmb();
144
145	dev->enabled = 1;
146
147	enabled_devices++;
148	return 0;
149
150fail_sysfs:
151	cpuidle_remove_state_sysfs(dev);
152
153	return ret;
154}
155
156EXPORT_SYMBOL_GPL(cpuidle_enable_device);
157
158/**
159 * cpuidle_disable_device - disables idle PM for a CPU
160 * @dev: the CPU
161 *
162 * This function must be called between cpuidle_pause_and_lock and
163 * cpuidle_resume_and_unlock when used externally.
164 */
165void cpuidle_disable_device(struct cpuidle_device *dev)
166{
167	if (!dev->enabled)
168		return;
169	if (!cpuidle_curr_driver || !cpuidle_curr_governor)
170		return;
171
172	dev->enabled = 0;
173
174	if (cpuidle_curr_governor->disable)
175		cpuidle_curr_governor->disable(dev);
176
177	cpuidle_remove_state_sysfs(dev);
178	enabled_devices--;
179}
180
181EXPORT_SYMBOL_GPL(cpuidle_disable_device);
182
183/**
184 * cpuidle_register_device - registers a CPU's idle PM feature
185 * @dev: the cpu
186 */
187int cpuidle_register_device(struct cpuidle_device *dev)
188{
189	int ret;
190	struct sys_device *sys_dev = get_cpu_sysdev((unsigned long)dev->cpu);
191
192	if (!sys_dev)
193		return -EINVAL;
194	if (!try_module_get(cpuidle_curr_driver->owner))
195		return -EINVAL;
196
197	init_completion(&dev->kobj_unregister);
198
199	mutex_lock(&cpuidle_lock);
200
201	per_cpu(cpuidle_devices, dev->cpu) = dev;
202	list_add(&dev->device_list, &cpuidle_detected_devices);
203	if ((ret = cpuidle_add_sysfs(sys_dev))) {
204		mutex_unlock(&cpuidle_lock);
205		module_put(cpuidle_curr_driver->owner);
206		return ret;
207	}
208
209	cpuidle_enable_device(dev);
210	cpuidle_install_idle_handler();
211
212	mutex_unlock(&cpuidle_lock);
213
214	return 0;
215
216}
217
218EXPORT_SYMBOL_GPL(cpuidle_register_device);
219
220/**
221 * cpuidle_unregister_device - unregisters a CPU's idle PM feature
222 * @dev: the cpu
223 */
224void cpuidle_unregister_device(struct cpuidle_device *dev)
225{
226	struct sys_device *sys_dev = get_cpu_sysdev((unsigned long)dev->cpu);
227
228	cpuidle_pause_and_lock();
229
230	cpuidle_disable_device(dev);
231
232	cpuidle_remove_sysfs(sys_dev);
233	list_del(&dev->device_list);
234	wait_for_completion(&dev->kobj_unregister);
235	per_cpu(cpuidle_devices, dev->cpu) = NULL;
236
237	cpuidle_resume_and_unlock();
238
239	module_put(cpuidle_curr_driver->owner);
240}
241
242EXPORT_SYMBOL_GPL(cpuidle_unregister_device);
243
244#ifdef CONFIG_SMP
245
246static void smp_callback(void *v)
247{
248	/* we already woke the CPU up, nothing more to do */
249}
250
251/*
252 * This function gets called when a part of the kernel has a new latency
253 * requirement.  This means we need to get all processors out of their C-state,
254 * and then recalculate a new suitable C-state. Just do a cross-cpu IPI; that
255 * wakes them all right up.
256 */
257static int cpuidle_latency_notify(struct notifier_block *b,
258		unsigned long l, void *v)
259{
260	smp_call_function(smp_callback, NULL, 0, 1);
261	return NOTIFY_OK;
262}
263
264static struct notifier_block cpuidle_latency_notifier = {
265	.notifier_call = cpuidle_latency_notify,
266};
267
268#define latency_notifier_init(x) do { register_latency_notifier(x); } while (0)
269
270#else /* CONFIG_SMP */
271
272#define latency_notifier_init(x) do { } while (0)
273
274#endif /* CONFIG_SMP */
275
276/**
277 * cpuidle_init - core initializer
278 */
279static int __init cpuidle_init(void)
280{
281	int ret;
282
283	pm_idle_old = pm_idle;
284
285	ret = cpuidle_add_class_sysfs(&cpu_sysdev_class);
286	if (ret)
287		return ret;
288
289	latency_notifier_init(&cpuidle_latency_notifier);
290
291	return 0;
292}
293
294core_initcall(cpuidle_init);
295