xref: /openbmc/linux/drivers/cpuidle/cpuidle.c (revision 4800cd83)
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 
24 DEFINE_PER_CPU(struct cpuidle_device *, cpuidle_devices);
25 
26 DEFINE_MUTEX(cpuidle_lock);
27 LIST_HEAD(cpuidle_detected_devices);
28 static void (*pm_idle_old)(void);
29 
30 static int enabled_devices;
31 
32 #if defined(CONFIG_ARCH_HAS_CPU_IDLE_WAIT)
33 static void cpuidle_kick_cpus(void)
34 {
35 	cpu_idle_wait();
36 }
37 #elif defined(CONFIG_SMP)
38 # error "Arch needs cpu_idle_wait() equivalent here"
39 #else /* !CONFIG_ARCH_HAS_CPU_IDLE_WAIT && !CONFIG_SMP */
40 static void cpuidle_kick_cpus(void) {}
41 #endif
42 
43 static int __cpuidle_register_device(struct cpuidle_device *dev);
44 
45 /**
46  * cpuidle_idle_call - the main idle loop
47  *
48  * NOTE: no locks or semaphores should be used here
49  */
50 static void cpuidle_idle_call(void)
51 {
52 	struct cpuidle_device *dev = __this_cpu_read(cpuidle_devices);
53 	struct cpuidle_state *target_state;
54 	int next_state;
55 
56 	/* check if the device is ready */
57 	if (!dev || !dev->enabled) {
58 		if (pm_idle_old)
59 			pm_idle_old();
60 		else
61 #if defined(CONFIG_ARCH_HAS_DEFAULT_IDLE)
62 			default_idle();
63 #else
64 			local_irq_enable();
65 #endif
66 		return;
67 	}
68 
69 #if 0
70 	/* shows regressions, re-enable for 2.6.29 */
71 	/*
72 	 * run any timers that can be run now, at this point
73 	 * before calculating the idle duration etc.
74 	 */
75 	hrtimer_peek_ahead_timers();
76 #endif
77 
78 	/*
79 	 * Call the device's prepare function before calling the
80 	 * governor's select function.  ->prepare gives the device's
81 	 * cpuidle driver a chance to update any dynamic information
82 	 * of its cpuidle states for the current idle period, e.g.
83 	 * state availability, latencies, residencies, etc.
84 	 */
85 	if (dev->prepare)
86 		dev->prepare(dev);
87 
88 	/* ask the governor for the next state */
89 	next_state = cpuidle_curr_governor->select(dev);
90 	if (need_resched()) {
91 		local_irq_enable();
92 		return;
93 	}
94 
95 	target_state = &dev->states[next_state];
96 
97 	/* enter the state and update stats */
98 	dev->last_state = target_state;
99 
100 	trace_power_start(POWER_CSTATE, next_state, dev->cpu);
101 	trace_cpu_idle(next_state, dev->cpu);
102 
103 	dev->last_residency = target_state->enter(dev, target_state);
104 
105 	trace_power_end(dev->cpu);
106 	trace_cpu_idle(PWR_EVENT_EXIT, dev->cpu);
107 
108 	if (dev->last_state)
109 		target_state = dev->last_state;
110 
111 	target_state->time += (unsigned long long)dev->last_residency;
112 	target_state->usage++;
113 
114 	/* give the governor an opportunity to reflect on the outcome */
115 	if (cpuidle_curr_governor->reflect)
116 		cpuidle_curr_governor->reflect(dev);
117 }
118 
119 /**
120  * cpuidle_install_idle_handler - installs the cpuidle idle loop handler
121  */
122 void cpuidle_install_idle_handler(void)
123 {
124 	if (enabled_devices && (pm_idle != cpuidle_idle_call)) {
125 		/* Make sure all changes finished before we switch to new idle */
126 		smp_wmb();
127 		pm_idle = cpuidle_idle_call;
128 	}
129 }
130 
131 /**
132  * cpuidle_uninstall_idle_handler - uninstalls the cpuidle idle loop handler
133  */
134 void cpuidle_uninstall_idle_handler(void)
135 {
136 	if (enabled_devices && pm_idle_old && (pm_idle != pm_idle_old)) {
137 		pm_idle = pm_idle_old;
138 		cpuidle_kick_cpus();
139 	}
140 }
141 
142 /**
143  * cpuidle_pause_and_lock - temporarily disables CPUIDLE
144  */
145 void cpuidle_pause_and_lock(void)
146 {
147 	mutex_lock(&cpuidle_lock);
148 	cpuidle_uninstall_idle_handler();
149 }
150 
151 EXPORT_SYMBOL_GPL(cpuidle_pause_and_lock);
152 
153 /**
154  * cpuidle_resume_and_unlock - resumes CPUIDLE operation
155  */
156 void cpuidle_resume_and_unlock(void)
157 {
158 	cpuidle_install_idle_handler();
159 	mutex_unlock(&cpuidle_lock);
160 }
161 
162 EXPORT_SYMBOL_GPL(cpuidle_resume_and_unlock);
163 
164 #ifdef CONFIG_ARCH_HAS_CPU_RELAX
165 static int poll_idle(struct cpuidle_device *dev, struct cpuidle_state *st)
166 {
167 	ktime_t	t1, t2;
168 	s64 diff;
169 	int ret;
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 	ret = (int) diff;
182 	return ret;
183 }
184 
185 static void poll_idle_init(struct cpuidle_device *dev)
186 {
187 	struct cpuidle_state *state = &dev->states[0];
188 
189 	cpuidle_set_statedata(state, NULL);
190 
191 	snprintf(state->name, CPUIDLE_NAME_LEN, "POLL");
192 	snprintf(state->desc, CPUIDLE_DESC_LEN, "CPUIDLE CORE POLL IDLE");
193 	state->exit_latency = 0;
194 	state->target_residency = 0;
195 	state->power_usage = -1;
196 	state->flags = 0;
197 	state->enter = poll_idle;
198 }
199 #else
200 static void poll_idle_init(struct cpuidle_device *dev) {}
201 #endif /* CONFIG_ARCH_HAS_CPU_RELAX */
202 
203 /**
204  * cpuidle_enable_device - enables idle PM for a CPU
205  * @dev: the CPU
206  *
207  * This function must be called between cpuidle_pause_and_lock and
208  * cpuidle_resume_and_unlock when used externally.
209  */
210 int cpuidle_enable_device(struct cpuidle_device *dev)
211 {
212 	int ret, i;
213 
214 	if (dev->enabled)
215 		return 0;
216 	if (!cpuidle_get_driver() || !cpuidle_curr_governor)
217 		return -EIO;
218 	if (!dev->state_count)
219 		return -EINVAL;
220 
221 	if (dev->registered == 0) {
222 		ret = __cpuidle_register_device(dev);
223 		if (ret)
224 			return ret;
225 	}
226 
227 	poll_idle_init(dev);
228 
229 	if ((ret = cpuidle_add_state_sysfs(dev)))
230 		return ret;
231 
232 	if (cpuidle_curr_governor->enable &&
233 	    (ret = cpuidle_curr_governor->enable(dev)))
234 		goto fail_sysfs;
235 
236 	for (i = 0; i < dev->state_count; i++) {
237 		dev->states[i].usage = 0;
238 		dev->states[i].time = 0;
239 	}
240 	dev->last_residency = 0;
241 	dev->last_state = NULL;
242 
243 	smp_wmb();
244 
245 	dev->enabled = 1;
246 
247 	enabled_devices++;
248 	return 0;
249 
250 fail_sysfs:
251 	cpuidle_remove_state_sysfs(dev);
252 
253 	return ret;
254 }
255 
256 EXPORT_SYMBOL_GPL(cpuidle_enable_device);
257 
258 /**
259  * cpuidle_disable_device - disables idle PM for a CPU
260  * @dev: the CPU
261  *
262  * This function must be called between cpuidle_pause_and_lock and
263  * cpuidle_resume_and_unlock when used externally.
264  */
265 void cpuidle_disable_device(struct cpuidle_device *dev)
266 {
267 	if (!dev->enabled)
268 		return;
269 	if (!cpuidle_get_driver() || !cpuidle_curr_governor)
270 		return;
271 
272 	dev->enabled = 0;
273 
274 	if (cpuidle_curr_governor->disable)
275 		cpuidle_curr_governor->disable(dev);
276 
277 	cpuidle_remove_state_sysfs(dev);
278 	enabled_devices--;
279 }
280 
281 EXPORT_SYMBOL_GPL(cpuidle_disable_device);
282 
283 /**
284  * __cpuidle_register_device - internal register function called before register
285  * and enable routines
286  * @dev: the cpu
287  *
288  * cpuidle_lock mutex must be held before this is called
289  */
290 static int __cpuidle_register_device(struct cpuidle_device *dev)
291 {
292 	int ret;
293 	struct sys_device *sys_dev = get_cpu_sysdev((unsigned long)dev->cpu);
294 	struct cpuidle_driver *cpuidle_driver = cpuidle_get_driver();
295 
296 	if (!sys_dev)
297 		return -EINVAL;
298 	if (!try_module_get(cpuidle_driver->owner))
299 		return -EINVAL;
300 
301 	init_completion(&dev->kobj_unregister);
302 
303 	/*
304 	 * cpuidle driver should set the dev->power_specified bit
305 	 * before registering the device if the driver provides
306 	 * power_usage numbers.
307 	 *
308 	 * For those devices whose ->power_specified is not set,
309 	 * we fill in power_usage with decreasing values as the
310 	 * cpuidle code has an implicit assumption that state Cn
311 	 * uses less power than C(n-1).
312 	 *
313 	 * With CONFIG_ARCH_HAS_CPU_RELAX, C0 is already assigned
314 	 * an power value of -1.  So we use -2, -3, etc, for other
315 	 * c-states.
316 	 */
317 	if (!dev->power_specified) {
318 		int i;
319 		for (i = CPUIDLE_DRIVER_STATE_START; i < dev->state_count; i++)
320 			dev->states[i].power_usage = -1 - i;
321 	}
322 
323 	per_cpu(cpuidle_devices, dev->cpu) = dev;
324 	list_add(&dev->device_list, &cpuidle_detected_devices);
325 	if ((ret = cpuidle_add_sysfs(sys_dev))) {
326 		module_put(cpuidle_driver->owner);
327 		return ret;
328 	}
329 
330 	dev->registered = 1;
331 	return 0;
332 }
333 
334 /**
335  * cpuidle_register_device - registers a CPU's idle PM feature
336  * @dev: the cpu
337  */
338 int cpuidle_register_device(struct cpuidle_device *dev)
339 {
340 	int ret;
341 
342 	mutex_lock(&cpuidle_lock);
343 
344 	if ((ret = __cpuidle_register_device(dev))) {
345 		mutex_unlock(&cpuidle_lock);
346 		return ret;
347 	}
348 
349 	cpuidle_enable_device(dev);
350 	cpuidle_install_idle_handler();
351 
352 	mutex_unlock(&cpuidle_lock);
353 
354 	return 0;
355 
356 }
357 
358 EXPORT_SYMBOL_GPL(cpuidle_register_device);
359 
360 /**
361  * cpuidle_unregister_device - unregisters a CPU's idle PM feature
362  * @dev: the cpu
363  */
364 void cpuidle_unregister_device(struct cpuidle_device *dev)
365 {
366 	struct sys_device *sys_dev = get_cpu_sysdev((unsigned long)dev->cpu);
367 	struct cpuidle_driver *cpuidle_driver = cpuidle_get_driver();
368 
369 	if (dev->registered == 0)
370 		return;
371 
372 	cpuidle_pause_and_lock();
373 
374 	cpuidle_disable_device(dev);
375 
376 	cpuidle_remove_sysfs(sys_dev);
377 	list_del(&dev->device_list);
378 	wait_for_completion(&dev->kobj_unregister);
379 	per_cpu(cpuidle_devices, dev->cpu) = NULL;
380 
381 	cpuidle_resume_and_unlock();
382 
383 	module_put(cpuidle_driver->owner);
384 }
385 
386 EXPORT_SYMBOL_GPL(cpuidle_unregister_device);
387 
388 #ifdef CONFIG_SMP
389 
390 static void smp_callback(void *v)
391 {
392 	/* we already woke the CPU up, nothing more to do */
393 }
394 
395 /*
396  * This function gets called when a part of the kernel has a new latency
397  * requirement.  This means we need to get all processors out of their C-state,
398  * and then recalculate a new suitable C-state. Just do a cross-cpu IPI; that
399  * wakes them all right up.
400  */
401 static int cpuidle_latency_notify(struct notifier_block *b,
402 		unsigned long l, void *v)
403 {
404 	smp_call_function(smp_callback, NULL, 1);
405 	return NOTIFY_OK;
406 }
407 
408 static struct notifier_block cpuidle_latency_notifier = {
409 	.notifier_call = cpuidle_latency_notify,
410 };
411 
412 static inline void latency_notifier_init(struct notifier_block *n)
413 {
414 	pm_qos_add_notifier(PM_QOS_CPU_DMA_LATENCY, n);
415 }
416 
417 #else /* CONFIG_SMP */
418 
419 #define latency_notifier_init(x) do { } while (0)
420 
421 #endif /* CONFIG_SMP */
422 
423 /**
424  * cpuidle_init - core initializer
425  */
426 static int __init cpuidle_init(void)
427 {
428 	int ret;
429 
430 	pm_idle_old = pm_idle;
431 
432 	ret = cpuidle_add_class_sysfs(&cpu_sysdev_class);
433 	if (ret)
434 		return ret;
435 
436 	latency_notifier_init(&cpuidle_latency_notifier);
437 
438 	return 0;
439 }
440 
441 core_initcall(cpuidle_init);
442