xref: /openbmc/linux/drivers/cpuidle/cpuidle.c (revision d0b73b48) 
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 
25 DEFINE_PER_CPU(struct cpuidle_device *, cpuidle_devices);
26 
27 DEFINE_MUTEX(cpuidle_lock);
28 LIST_HEAD(cpuidle_detected_devices);
29 
30 static int enabled_devices;
31 static int off __read_mostly;
32 static int initialized __read_mostly;
33 
34 int cpuidle_disabled(void)
35 {
36 	return off;
37 }
38 void disable_cpuidle(void)
39 {
40 	off = 1;
41 }
42 
43 static int __cpuidle_register_device(struct cpuidle_device *dev);
44 
45 static 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 
52 static 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 
58 typedef int (*cpuidle_enter_t)(struct cpuidle_device *dev,
59 			       struct cpuidle_driver *drv, int index);
60 
61 static 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  */
68 int 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;
73 
74 	if (!drv)
75 		return -ENODEV;
76 
77 	/* Find lowest-power state that supports long-term idle */
78 	for (i = drv->state_count - 1; i >= CPUIDLE_DRIVER_STATE_START; i--)
79 		if (drv->states[i].enter_dead)
80 			return drv->states[i].enter_dead(dev, i);
81 
82 	return -ENODEV;
83 }
84 
85 /**
86  * cpuidle_enter_state - enter the state and update stats
87  * @dev: cpuidle device for this cpu
88  * @drv: cpuidle driver for this cpu
89  * @next_state: index into drv->states of the state to enter
90  */
91 int cpuidle_enter_state(struct cpuidle_device *dev, struct cpuidle_driver *drv,
92 		int next_state)
93 {
94 	int entered_state;
95 
96 	entered_state = cpuidle_enter_ops(dev, drv, next_state);
97 
98 	if (entered_state >= 0) {
99 		/* Update cpuidle counters */
100 		/* This can be moved to within driver enter routine
101 		 * but that results in multiple copies of same code.
102 		 */
103 		dev->states_usage[entered_state].time += dev->last_residency;
104 		dev->states_usage[entered_state].usage++;
105 	} else {
106 		dev->last_residency = 0;
107 	}
108 
109 	return entered_state;
110 }
111 
112 /**
113  * cpuidle_idle_call - the main idle loop
114  *
115  * NOTE: no locks or semaphores should be used here
116  * return non-zero on failure
117  */
118 int cpuidle_idle_call(void)
119 {
120 	struct cpuidle_device *dev = __this_cpu_read(cpuidle_devices);
121 	struct cpuidle_driver *drv;
122 	int next_state, entered_state;
123 
124 	if (off)
125 		return -ENODEV;
126 
127 	if (!initialized)
128 		return -ENODEV;
129 
130 	/* check if the device is ready */
131 	if (!dev || !dev->enabled)
132 		return -EBUSY;
133 
134 	drv = cpuidle_get_cpu_driver(dev);
135 
136 	/* ask the governor for the next state */
137 	next_state = cpuidle_curr_governor->select(drv, dev);
138 	if (need_resched()) {
139 		dev->last_residency = 0;
140 		/* give the governor an opportunity to reflect on the outcome */
141 		if (cpuidle_curr_governor->reflect)
142 			cpuidle_curr_governor->reflect(dev, next_state);
143 		local_irq_enable();
144 		return 0;
145 	}
146 
147 	trace_power_start_rcuidle(POWER_CSTATE, next_state, dev->cpu);
148 	trace_cpu_idle_rcuidle(next_state, dev->cpu);
149 
150 	if (cpuidle_state_is_coupled(dev, drv, next_state))
151 		entered_state = cpuidle_enter_state_coupled(dev, drv,
152 							    next_state);
153 	else
154 		entered_state = cpuidle_enter_state(dev, drv, next_state);
155 
156 	trace_power_end_rcuidle(dev->cpu);
157 	trace_cpu_idle_rcuidle(PWR_EVENT_EXIT, dev->cpu);
158 
159 	/* give the governor an opportunity to reflect on the outcome */
160 	if (cpuidle_curr_governor->reflect)
161 		cpuidle_curr_governor->reflect(dev, entered_state);
162 
163 	return 0;
164 }
165 
166 /**
167  * cpuidle_install_idle_handler - installs the cpuidle idle loop handler
168  */
169 void cpuidle_install_idle_handler(void)
170 {
171 	if (enabled_devices) {
172 		/* Make sure all changes finished before we switch to new idle */
173 		smp_wmb();
174 		initialized = 1;
175 	}
176 }
177 
178 /**
179  * cpuidle_uninstall_idle_handler - uninstalls the cpuidle idle loop handler
180  */
181 void cpuidle_uninstall_idle_handler(void)
182 {
183 	if (enabled_devices) {
184 		initialized = 0;
185 		kick_all_cpus_sync();
186 	}
187 }
188 
189 /**
190  * cpuidle_pause_and_lock - temporarily disables CPUIDLE
191  */
192 void cpuidle_pause_and_lock(void)
193 {
194 	mutex_lock(&cpuidle_lock);
195 	cpuidle_uninstall_idle_handler();
196 }
197 
198 EXPORT_SYMBOL_GPL(cpuidle_pause_and_lock);
199 
200 /**
201  * cpuidle_resume_and_unlock - resumes CPUIDLE operation
202  */
203 void cpuidle_resume_and_unlock(void)
204 {
205 	cpuidle_install_idle_handler();
206 	mutex_unlock(&cpuidle_lock);
207 }
208 
209 EXPORT_SYMBOL_GPL(cpuidle_resume_and_unlock);
210 
211 /* Currently used in suspend/resume path to suspend cpuidle */
212 void cpuidle_pause(void)
213 {
214 	mutex_lock(&cpuidle_lock);
215 	cpuidle_uninstall_idle_handler();
216 	mutex_unlock(&cpuidle_lock);
217 }
218 
219 /* Currently used in suspend/resume path to resume cpuidle */
220 void cpuidle_resume(void)
221 {
222 	mutex_lock(&cpuidle_lock);
223 	cpuidle_install_idle_handler();
224 	mutex_unlock(&cpuidle_lock);
225 }
226 
227 /**
228  * cpuidle_wrap_enter - performs timekeeping and irqen around enter function
229  * @dev: pointer to a valid cpuidle_device object
230  * @drv: pointer to a valid cpuidle_driver object
231  * @index: index of the target cpuidle state.
232  */
233 int cpuidle_wrap_enter(struct cpuidle_device *dev,
234 				struct cpuidle_driver *drv, int index,
235 				int (*enter)(struct cpuidle_device *dev,
236 					struct cpuidle_driver *drv, int index))
237 {
238 	ktime_t time_start, time_end;
239 	s64 diff;
240 
241 	time_start = ktime_get();
242 
243 	index = enter(dev, drv, index);
244 
245 	time_end = ktime_get();
246 
247 	local_irq_enable();
248 
249 	diff = ktime_to_us(ktime_sub(time_end, time_start));
250 	if (diff > INT_MAX)
251 		diff = INT_MAX;
252 
253 	dev->last_residency = (int) diff;
254 
255 	return index;
256 }
257 
258 #ifdef CONFIG_ARCH_HAS_CPU_RELAX
259 static int poll_idle(struct cpuidle_device *dev,
260 		struct cpuidle_driver *drv, int index)
261 {
262 	ktime_t	t1, t2;
263 	s64 diff;
264 
265 	t1 = ktime_get();
266 	local_irq_enable();
267 	while (!need_resched())
268 		cpu_relax();
269 
270 	t2 = ktime_get();
271 	diff = ktime_to_us(ktime_sub(t2, t1));
272 	if (diff > INT_MAX)
273 		diff = INT_MAX;
274 
275 	dev->last_residency = (int) diff;
276 
277 	return index;
278 }
279 
280 static void poll_idle_init(struct cpuidle_driver *drv)
281 {
282 	struct cpuidle_state *state = &drv->states[0];
283 
284 	snprintf(state->name, CPUIDLE_NAME_LEN, "POLL");
285 	snprintf(state->desc, CPUIDLE_DESC_LEN, "CPUIDLE CORE POLL IDLE");
286 	state->exit_latency = 0;
287 	state->target_residency = 0;
288 	state->power_usage = -1;
289 	state->flags = 0;
290 	state->enter = poll_idle;
291 	state->disabled = false;
292 }
293 #else
294 static void poll_idle_init(struct cpuidle_driver *drv) {}
295 #endif /* CONFIG_ARCH_HAS_CPU_RELAX */
296 
297 /**
298  * cpuidle_enable_device - enables idle PM for a CPU
299  * @dev: the CPU
300  *
301  * This function must be called between cpuidle_pause_and_lock and
302  * cpuidle_resume_and_unlock when used externally.
303  */
304 int cpuidle_enable_device(struct cpuidle_device *dev)
305 {
306 	int ret, i;
307 	struct cpuidle_driver *drv;
308 
309 	if (!dev)
310 		return -EINVAL;
311 
312 	if (dev->enabled)
313 		return 0;
314 
315 	drv = cpuidle_get_cpu_driver(dev);
316 
317 	if (!drv || !cpuidle_curr_governor)
318 		return -EIO;
319 
320 	if (!dev->state_count)
321 		dev->state_count = drv->state_count;
322 
323 	if (dev->registered == 0) {
324 		ret = __cpuidle_register_device(dev);
325 		if (ret)
326 			return ret;
327 	}
328 
329 	cpuidle_enter_ops = drv->en_core_tk_irqen ?
330 		cpuidle_enter_tk : cpuidle_enter;
331 
332 	poll_idle_init(drv);
333 
334 	ret = cpuidle_add_device_sysfs(dev);
335 	if (ret)
336 		return ret;
337 
338 	if (cpuidle_curr_governor->enable &&
339 	    (ret = cpuidle_curr_governor->enable(drv, dev)))
340 		goto fail_sysfs;
341 
342 	for (i = 0; i < dev->state_count; i++) {
343 		dev->states_usage[i].usage = 0;
344 		dev->states_usage[i].time = 0;
345 	}
346 	dev->last_residency = 0;
347 
348 	smp_wmb();
349 
350 	dev->enabled = 1;
351 
352 	enabled_devices++;
353 	return 0;
354 
355 fail_sysfs:
356 	cpuidle_remove_device_sysfs(dev);
357 
358 	return ret;
359 }
360 
361 EXPORT_SYMBOL_GPL(cpuidle_enable_device);
362 
363 /**
364  * cpuidle_disable_device - disables idle PM for a CPU
365  * @dev: the CPU
366  *
367  * This function must be called between cpuidle_pause_and_lock and
368  * cpuidle_resume_and_unlock when used externally.
369  */
370 void cpuidle_disable_device(struct cpuidle_device *dev)
371 {
372 	struct cpuidle_driver *drv = cpuidle_get_cpu_driver(dev);
373 
374 	if (!dev || !dev->enabled)
375 		return;
376 
377 	if (!drv || !cpuidle_curr_governor)
378 		return;
379 
380 	dev->enabled = 0;
381 
382 	if (cpuidle_curr_governor->disable)
383 		cpuidle_curr_governor->disable(drv, dev);
384 
385 	cpuidle_remove_device_sysfs(dev);
386 	enabled_devices--;
387 }
388 
389 EXPORT_SYMBOL_GPL(cpuidle_disable_device);
390 
391 /**
392  * __cpuidle_register_device - internal register function called before register
393  * and enable routines
394  * @dev: the cpu
395  *
396  * cpuidle_lock mutex must be held before this is called
397  */
398 static int __cpuidle_register_device(struct cpuidle_device *dev)
399 {
400 	int ret;
401 	struct cpuidle_driver *drv = cpuidle_get_cpu_driver(dev);
402 
403 	if (!try_module_get(drv->owner))
404 		return -EINVAL;
405 
406 	per_cpu(cpuidle_devices, dev->cpu) = dev;
407 	list_add(&dev->device_list, &cpuidle_detected_devices);
408 	ret = cpuidle_add_sysfs(dev);
409 	if (ret)
410 		goto err_sysfs;
411 
412 	ret = cpuidle_coupled_register_device(dev);
413 	if (ret)
414 		goto err_coupled;
415 
416 	dev->registered = 1;
417 	return 0;
418 
419 err_coupled:
420 	cpuidle_remove_sysfs(dev);
421 err_sysfs:
422 	list_del(&dev->device_list);
423 	per_cpu(cpuidle_devices, dev->cpu) = NULL;
424 	module_put(drv->owner);
425 	return ret;
426 }
427 
428 /**
429  * cpuidle_register_device - registers a CPU's idle PM feature
430  * @dev: the cpu
431  */
432 int cpuidle_register_device(struct cpuidle_device *dev)
433 {
434 	int ret;
435 
436 	if (!dev)
437 		return -EINVAL;
438 
439 	mutex_lock(&cpuidle_lock);
440 
441 	if ((ret = __cpuidle_register_device(dev))) {
442 		mutex_unlock(&cpuidle_lock);
443 		return ret;
444 	}
445 
446 	cpuidle_enable_device(dev);
447 	cpuidle_install_idle_handler();
448 
449 	mutex_unlock(&cpuidle_lock);
450 
451 	return 0;
452 
453 }
454 
455 EXPORT_SYMBOL_GPL(cpuidle_register_device);
456 
457 /**
458  * cpuidle_unregister_device - unregisters a CPU's idle PM feature
459  * @dev: the cpu
460  */
461 void cpuidle_unregister_device(struct cpuidle_device *dev)
462 {
463 	struct cpuidle_driver *drv = cpuidle_get_cpu_driver(dev);
464 
465 	if (dev->registered == 0)
466 		return;
467 
468 	cpuidle_pause_and_lock();
469 
470 	cpuidle_disable_device(dev);
471 
472 	cpuidle_remove_sysfs(dev);
473 	list_del(&dev->device_list);
474 	per_cpu(cpuidle_devices, dev->cpu) = NULL;
475 
476 	cpuidle_coupled_unregister_device(dev);
477 
478 	cpuidle_resume_and_unlock();
479 
480 	module_put(drv->owner);
481 }
482 
483 EXPORT_SYMBOL_GPL(cpuidle_unregister_device);
484 
485 #ifdef CONFIG_SMP
486 
487 static void smp_callback(void *v)
488 {
489 	/* we already woke the CPU up, nothing more to do */
490 }
491 
492 /*
493  * This function gets called when a part of the kernel has a new latency
494  * requirement.  This means we need to get all processors out of their C-state,
495  * and then recalculate a new suitable C-state. Just do a cross-cpu IPI; that
496  * wakes them all right up.
497  */
498 static int cpuidle_latency_notify(struct notifier_block *b,
499 		unsigned long l, void *v)
500 {
501 	smp_call_function(smp_callback, NULL, 1);
502 	return NOTIFY_OK;
503 }
504 
505 static struct notifier_block cpuidle_latency_notifier = {
506 	.notifier_call = cpuidle_latency_notify,
507 };
508 
509 static inline void latency_notifier_init(struct notifier_block *n)
510 {
511 	pm_qos_add_notifier(PM_QOS_CPU_DMA_LATENCY, n);
512 }
513 
514 #else /* CONFIG_SMP */
515 
516 #define latency_notifier_init(x) do { } while (0)
517 
518 #endif /* CONFIG_SMP */
519 
520 /**
521  * cpuidle_init - core initializer
522  */
523 static int __init cpuidle_init(void)
524 {
525 	int ret;
526 
527 	if (cpuidle_disabled())
528 		return -ENODEV;
529 
530 	ret = cpuidle_add_interface(cpu_subsys.dev_root);
531 	if (ret)
532 		return ret;
533 
534 	latency_notifier_init(&cpuidle_latency_notifier);
535 
536 	return 0;
537 }
538 
539 module_param(off, int, 0444);
540 core_initcall(cpuidle_init);
541