2 * devfreq: Generic Dynamic Voltage and Frequency Scaling (DVFS) Framework
5 * Copyright (C) 2011 Samsung Electronics
6 * MyungJoo Ham <myungjoo.ham@samsung.com>
8 * This program is free software; you can redistribute it and/or modify
9 * it under the terms of the GNU General Public License version 2 as
10 * published by the Free Software Foundation.
13 #include <linux/kernel.h>
14 #include <linux/sched.h>
15 #include <linux/errno.h>
16 #include <linux/err.h>
17 #include <linux/init.h>
18 #include <linux/module.h>
19 #include <linux/slab.h>
20 #include <linux/stat.h>
21 #include <linux/opp.h>
22 #include <linux/devfreq.h>
23 #include <linux/workqueue.h>
24 #include <linux/platform_device.h>
25 #include <linux/list.h>
26 #include <linux/printk.h>
27 #include <linux/hrtimer.h>
30 static struct class *devfreq_class;
33 * devfreq core provides delayed work based load monitoring helper
34 * functions. Governors can use these or can implement their own
35 * monitoring mechanism.
37 static struct workqueue_struct *devfreq_wq;
39 /* The list of all device-devfreq */
40 static LIST_HEAD(devfreq_list);
41 static DEFINE_MUTEX(devfreq_list_lock);
44 * find_device_devfreq() - find devfreq struct using device pointer
45 * @dev: device pointer used to lookup device devfreq.
47 * Search the list of device devfreqs and return the matched device's
48 * devfreq info. devfreq_list_lock should be held by the caller.
50 static struct devfreq *find_device_devfreq(struct device *dev)
52 struct devfreq *tmp_devfreq;
54 if (unlikely(IS_ERR_OR_NULL(dev))) {
55 pr_err("DEVFREQ: %s: Invalid parameters\n", __func__);
56 return ERR_PTR(-EINVAL);
58 WARN(!mutex_is_locked(&devfreq_list_lock),
59 "devfreq_list_lock must be locked.");
61 list_for_each_entry(tmp_devfreq, &devfreq_list, node) {
62 if (tmp_devfreq->dev.parent == dev)
66 return ERR_PTR(-ENODEV);
69 /* Load monitoring helper functions for governors use */
72 * update_devfreq() - Reevaluate the device and configure frequency.
73 * @devfreq: the devfreq instance.
75 * Note: Lock devfreq->lock before calling update_devfreq
76 * This function is exported for governors.
78 int update_devfreq(struct devfreq *devfreq)
84 if (!mutex_is_locked(&devfreq->lock)) {
85 WARN(true, "devfreq->lock must be locked by the caller.\n");
89 /* Reevaluate the proper frequency */
90 err = devfreq->governor->get_target_freq(devfreq, &freq);
95 * Adjust the freuqency with user freq and QoS.
97 * List from the highest proiority
98 * max_freq (probably called by thermal when it's too hot)
102 if (devfreq->min_freq && freq < devfreq->min_freq) {
103 freq = devfreq->min_freq;
104 flags &= ~DEVFREQ_FLAG_LEAST_UPPER_BOUND; /* Use GLB */
106 if (devfreq->max_freq && freq > devfreq->max_freq) {
107 freq = devfreq->max_freq;
108 flags |= DEVFREQ_FLAG_LEAST_UPPER_BOUND; /* Use LUB */
111 err = devfreq->profile->target(devfreq->dev.parent, &freq, flags);
115 devfreq->previous_freq = freq;
120 * devfreq_monitor() - Periodically poll devfreq objects.
121 * @work: the work struct used to run devfreq_monitor periodically.
124 static void devfreq_monitor(struct work_struct *work)
127 struct devfreq *devfreq = container_of(work,
128 struct devfreq, work.work);
130 mutex_lock(&devfreq->lock);
131 err = update_devfreq(devfreq);
133 dev_err(&devfreq->dev, "dvfs failed with (%d) error\n", err);
135 queue_delayed_work(devfreq_wq, &devfreq->work,
136 msecs_to_jiffies(devfreq->profile->polling_ms));
137 mutex_unlock(&devfreq->lock);
141 * devfreq_monitor_start() - Start load monitoring of devfreq instance
142 * @devfreq: the devfreq instance.
144 * Helper function for starting devfreq device load monitoing. By
145 * default delayed work based monitoring is supported. Function
146 * to be called from governor in response to DEVFREQ_GOV_START
147 * event when device is added to devfreq framework.
149 void devfreq_monitor_start(struct devfreq *devfreq)
151 INIT_DEFERRABLE_WORK(&devfreq->work, devfreq_monitor);
152 if (devfreq->profile->polling_ms)
153 queue_delayed_work(devfreq_wq, &devfreq->work,
154 msecs_to_jiffies(devfreq->profile->polling_ms));
158 * devfreq_monitor_stop() - Stop load monitoring of a devfreq instance
159 * @devfreq: the devfreq instance.
161 * Helper function to stop devfreq device load monitoing. Function
162 * to be called from governor in response to DEVFREQ_GOV_STOP
163 * event when device is removed from devfreq framework.
165 void devfreq_monitor_stop(struct devfreq *devfreq)
167 cancel_delayed_work_sync(&devfreq->work);
171 * devfreq_monitor_suspend() - Suspend load monitoring of a devfreq instance
172 * @devfreq: the devfreq instance.
174 * Helper function to suspend devfreq device load monitoing. Function
175 * to be called from governor in response to DEVFREQ_GOV_SUSPEND
176 * event or when polling interval is set to zero.
178 * Note: Though this function is same as devfreq_monitor_stop(),
179 * intentionally kept separate to provide hooks for collecting
180 * transition statistics.
182 void devfreq_monitor_suspend(struct devfreq *devfreq)
184 mutex_lock(&devfreq->lock);
185 if (devfreq->stop_polling) {
186 mutex_unlock(&devfreq->lock);
190 devfreq->stop_polling = true;
191 mutex_unlock(&devfreq->lock);
192 cancel_delayed_work_sync(&devfreq->work);
196 * devfreq_monitor_resume() - Resume load monitoring of a devfreq instance
197 * @devfreq: the devfreq instance.
199 * Helper function to resume devfreq device load monitoing. Function
200 * to be called from governor in response to DEVFREQ_GOV_RESUME
201 * event or when polling interval is set to non-zero.
203 void devfreq_monitor_resume(struct devfreq *devfreq)
205 mutex_lock(&devfreq->lock);
206 if (!devfreq->stop_polling)
209 if (!delayed_work_pending(&devfreq->work) &&
210 devfreq->profile->polling_ms)
211 queue_delayed_work(devfreq_wq, &devfreq->work,
212 msecs_to_jiffies(devfreq->profile->polling_ms));
213 devfreq->stop_polling = false;
216 mutex_unlock(&devfreq->lock);
220 * devfreq_interval_update() - Update device devfreq monitoring interval
221 * @devfreq: the devfreq instance.
222 * @delay: new polling interval to be set.
224 * Helper function to set new load monitoring polling interval. Function
225 * to be called from governor in response to DEVFREQ_GOV_INTERVAL event.
227 void devfreq_interval_update(struct devfreq *devfreq, unsigned int *delay)
229 unsigned int cur_delay = devfreq->profile->polling_ms;
230 unsigned int new_delay = *delay;
232 mutex_lock(&devfreq->lock);
233 devfreq->profile->polling_ms = new_delay;
235 if (devfreq->stop_polling)
238 /* if new delay is zero, stop polling */
240 mutex_unlock(&devfreq->lock);
241 cancel_delayed_work_sync(&devfreq->work);
245 /* if current delay is zero, start polling with new delay */
247 queue_delayed_work(devfreq_wq, &devfreq->work,
248 msecs_to_jiffies(devfreq->profile->polling_ms));
252 /* if current delay is greater than new delay, restart polling */
253 if (cur_delay > new_delay) {
254 mutex_unlock(&devfreq->lock);
255 cancel_delayed_work_sync(&devfreq->work);
256 mutex_lock(&devfreq->lock);
257 if (!devfreq->stop_polling)
258 queue_delayed_work(devfreq_wq, &devfreq->work,
259 msecs_to_jiffies(devfreq->profile->polling_ms));
262 mutex_unlock(&devfreq->lock);
266 * devfreq_notifier_call() - Notify that the device frequency requirements
267 * has been changed out of devfreq framework.
268 * @nb: the notifier_block (supposed to be devfreq->nb)
272 * Called by a notifier that uses devfreq->nb.
274 static int devfreq_notifier_call(struct notifier_block *nb, unsigned long type,
277 struct devfreq *devfreq = container_of(nb, struct devfreq, nb);
280 mutex_lock(&devfreq->lock);
281 ret = update_devfreq(devfreq);
282 mutex_unlock(&devfreq->lock);
288 * _remove_devfreq() - Remove devfreq from the devfreq list and
289 release its resources.
290 * @devfreq: the devfreq struct
291 * @skip: skip calling device_unregister().
293 static void _remove_devfreq(struct devfreq *devfreq, bool skip)
295 mutex_lock(&devfreq_list_lock);
296 if (IS_ERR(find_device_devfreq(devfreq->dev.parent))) {
297 mutex_unlock(&devfreq_list_lock);
298 dev_warn(&devfreq->dev, "releasing devfreq which doesn't exist\n");
301 list_del(&devfreq->node);
302 mutex_unlock(&devfreq_list_lock);
304 devfreq->governor->event_handler(devfreq, DEVFREQ_GOV_STOP, NULL);
306 if (devfreq->profile->exit)
307 devfreq->profile->exit(devfreq->dev.parent);
309 if (!skip && get_device(&devfreq->dev)) {
310 device_unregister(&devfreq->dev);
311 put_device(&devfreq->dev);
314 mutex_destroy(&devfreq->lock);
319 * devfreq_dev_release() - Callback for struct device to release the device.
320 * @dev: the devfreq device
322 * This calls _remove_devfreq() if _remove_devfreq() is not called.
323 * Note that devfreq_dev_release() could be called by _remove_devfreq() as
324 * well as by others unregistering the device.
326 static void devfreq_dev_release(struct device *dev)
328 struct devfreq *devfreq = to_devfreq(dev);
330 _remove_devfreq(devfreq, true);
334 * devfreq_add_device() - Add devfreq feature to the device
335 * @dev: the device to add devfreq feature.
336 * @profile: device-specific profile to run devfreq.
337 * @governor: the policy to choose frequency.
338 * @data: private data for the governor. The devfreq framework does not
341 struct devfreq *devfreq_add_device(struct device *dev,
342 struct devfreq_dev_profile *profile,
343 const struct devfreq_governor *governor,
346 struct devfreq *devfreq;
349 if (!dev || !profile || !governor) {
350 dev_err(dev, "%s: Invalid parameters.\n", __func__);
351 return ERR_PTR(-EINVAL);
354 mutex_lock(&devfreq_list_lock);
355 devfreq = find_device_devfreq(dev);
356 mutex_unlock(&devfreq_list_lock);
357 if (!IS_ERR(devfreq)) {
358 dev_err(dev, "%s: Unable to create devfreq for the device. It already has one.\n", __func__);
363 devfreq = kzalloc(sizeof(struct devfreq), GFP_KERNEL);
365 dev_err(dev, "%s: Unable to create devfreq for the device\n",
371 mutex_init(&devfreq->lock);
372 mutex_lock(&devfreq->lock);
373 devfreq->dev.parent = dev;
374 devfreq->dev.class = devfreq_class;
375 devfreq->dev.release = devfreq_dev_release;
376 devfreq->profile = profile;
377 devfreq->governor = governor;
378 devfreq->previous_freq = profile->initial_freq;
379 devfreq->data = data;
380 devfreq->nb.notifier_call = devfreq_notifier_call;
382 dev_set_name(&devfreq->dev, dev_name(dev));
383 err = device_register(&devfreq->dev);
385 put_device(&devfreq->dev);
386 mutex_unlock(&devfreq->lock);
390 mutex_unlock(&devfreq->lock);
392 mutex_lock(&devfreq_list_lock);
393 list_add(&devfreq->node, &devfreq_list);
394 mutex_unlock(&devfreq_list_lock);
396 err = devfreq->governor->event_handler(devfreq,
397 DEVFREQ_GOV_START, NULL);
399 dev_err(dev, "%s: Unable to start governor for the device\n",
407 list_del(&devfreq->node);
408 device_unregister(&devfreq->dev);
414 EXPORT_SYMBOL(devfreq_add_device);
417 * devfreq_remove_device() - Remove devfreq feature from a device.
418 * @devfreq: the devfreq instance to be removed
420 int devfreq_remove_device(struct devfreq *devfreq)
425 _remove_devfreq(devfreq, false);
429 EXPORT_SYMBOL(devfreq_remove_device);
432 * devfreq_suspend_device() - Suspend devfreq of a device.
433 * @devfreq the devfreq instance to be suspended
435 int devfreq_suspend_device(struct devfreq *devfreq)
440 return devfreq->governor->event_handler(devfreq,
441 DEVFREQ_GOV_SUSPEND, NULL);
443 EXPORT_SYMBOL(devfreq_suspend_device);
446 * devfreq_resume_device() - Resume devfreq of a device.
447 * @devfreq the devfreq instance to be resumed
449 int devfreq_resume_device(struct devfreq *devfreq)
454 return devfreq->governor->event_handler(devfreq,
455 DEVFREQ_GOV_RESUME, NULL);
457 EXPORT_SYMBOL(devfreq_resume_device);
459 static ssize_t show_governor(struct device *dev,
460 struct device_attribute *attr, char *buf)
462 return sprintf(buf, "%s\n", to_devfreq(dev)->governor->name);
465 static ssize_t show_freq(struct device *dev,
466 struct device_attribute *attr, char *buf)
469 struct devfreq *devfreq = to_devfreq(dev);
471 if (devfreq->profile->get_cur_freq &&
472 !devfreq->profile->get_cur_freq(devfreq->dev.parent, &freq))
473 return sprintf(buf, "%lu\n", freq);
475 return sprintf(buf, "%lu\n", devfreq->previous_freq);
478 static ssize_t show_target_freq(struct device *dev,
479 struct device_attribute *attr, char *buf)
481 return sprintf(buf, "%lu\n", to_devfreq(dev)->previous_freq);
484 static ssize_t show_polling_interval(struct device *dev,
485 struct device_attribute *attr, char *buf)
487 return sprintf(buf, "%d\n", to_devfreq(dev)->profile->polling_ms);
490 static ssize_t store_polling_interval(struct device *dev,
491 struct device_attribute *attr,
492 const char *buf, size_t count)
494 struct devfreq *df = to_devfreq(dev);
498 ret = sscanf(buf, "%u", &value);
502 df->governor->event_handler(df, DEVFREQ_GOV_INTERVAL, &value);
508 static ssize_t store_min_freq(struct device *dev, struct device_attribute *attr,
509 const char *buf, size_t count)
511 struct devfreq *df = to_devfreq(dev);
516 ret = sscanf(buf, "%lu", &value);
520 mutex_lock(&df->lock);
522 if (value && max && value > max) {
527 df->min_freq = value;
531 mutex_unlock(&df->lock);
535 static ssize_t show_min_freq(struct device *dev, struct device_attribute *attr,
538 return sprintf(buf, "%lu\n", to_devfreq(dev)->min_freq);
541 static ssize_t store_max_freq(struct device *dev, struct device_attribute *attr,
542 const char *buf, size_t count)
544 struct devfreq *df = to_devfreq(dev);
549 ret = sscanf(buf, "%lu", &value);
553 mutex_lock(&df->lock);
555 if (value && min && value < min) {
560 df->max_freq = value;
564 mutex_unlock(&df->lock);
568 static ssize_t show_max_freq(struct device *dev, struct device_attribute *attr,
571 return sprintf(buf, "%lu\n", to_devfreq(dev)->max_freq);
574 static struct device_attribute devfreq_attrs[] = {
575 __ATTR(governor, S_IRUGO, show_governor, NULL),
576 __ATTR(cur_freq, S_IRUGO, show_freq, NULL),
577 __ATTR(target_freq, S_IRUGO, show_target_freq, NULL),
578 __ATTR(polling_interval, S_IRUGO | S_IWUSR, show_polling_interval,
579 store_polling_interval),
580 __ATTR(min_freq, S_IRUGO | S_IWUSR, show_min_freq, store_min_freq),
581 __ATTR(max_freq, S_IRUGO | S_IWUSR, show_max_freq, store_max_freq),
585 static int __init devfreq_init(void)
587 devfreq_class = class_create(THIS_MODULE, "devfreq");
588 if (IS_ERR(devfreq_class)) {
589 pr_err("%s: couldn't create class\n", __FILE__);
590 return PTR_ERR(devfreq_class);
593 devfreq_wq = create_freezable_workqueue("devfreq_wq");
594 if (IS_ERR(devfreq_wq)) {
595 class_destroy(devfreq_class);
596 pr_err("%s: couldn't create workqueue\n", __FILE__);
597 return PTR_ERR(devfreq_wq);
599 devfreq_class->dev_attrs = devfreq_attrs;
603 subsys_initcall(devfreq_init);
605 static void __exit devfreq_exit(void)
607 class_destroy(devfreq_class);
608 destroy_workqueue(devfreq_wq);
610 module_exit(devfreq_exit);
613 * The followings are helper functions for devfreq user device drivers with
618 * devfreq_recommended_opp() - Helper function to get proper OPP for the
619 * freq value given to target callback.
620 * @dev: The devfreq user device. (parent of devfreq)
621 * @freq: The frequency given to target function
622 * @flags: Flags handed from devfreq framework.
625 struct opp *devfreq_recommended_opp(struct device *dev, unsigned long *freq,
630 if (flags & DEVFREQ_FLAG_LEAST_UPPER_BOUND) {
631 /* The freq is an upper bound. opp should be lower */
632 opp = opp_find_freq_floor(dev, freq);
634 /* If not available, use the closest opp */
635 if (opp == ERR_PTR(-ERANGE))
636 opp = opp_find_freq_ceil(dev, freq);
638 /* The freq is an lower bound. opp should be higher */
639 opp = opp_find_freq_ceil(dev, freq);
641 /* If not available, use the closest opp */
642 if (opp == ERR_PTR(-ERANGE))
643 opp = opp_find_freq_floor(dev, freq);
650 * devfreq_register_opp_notifier() - Helper function to get devfreq notified
651 * for any changes in the OPP availability
653 * @dev: The devfreq user device. (parent of devfreq)
654 * @devfreq: The devfreq object.
656 int devfreq_register_opp_notifier(struct device *dev, struct devfreq *devfreq)
658 struct srcu_notifier_head *nh = opp_get_notifier(dev);
662 return srcu_notifier_chain_register(nh, &devfreq->nb);
666 * devfreq_unregister_opp_notifier() - Helper function to stop getting devfreq
667 * notified for any changes in the OPP
668 * availability changes anymore.
669 * @dev: The devfreq user device. (parent of devfreq)
670 * @devfreq: The devfreq object.
672 * At exit() callback of devfreq_dev_profile, this must be included if
673 * devfreq_recommended_opp is used.
675 int devfreq_unregister_opp_notifier(struct device *dev, struct devfreq *devfreq)
677 struct srcu_notifier_head *nh = opp_get_notifier(dev);
681 return srcu_notifier_chain_unregister(nh, &devfreq->nb);
684 MODULE_AUTHOR("MyungJoo Ham <myungjoo.ham@samsung.com>");
685 MODULE_DESCRIPTION("devfreq class support");
686 MODULE_LICENSE("GPL");