Root/drivers/devfreq/devfreq.c

1/*
2 * devfreq: Generic Dynamic Voltage and Frequency Scaling (DVFS) Framework
3 * for Non-CPU Devices.
4 *
5 * Copyright (C) 2011 Samsung Electronics
6 * MyungJoo Ham <myungjoo.ham@samsung.com>
7 *
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.
11 */
12
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>
28#include "governor.h"
29
30struct class *devfreq_class;
31
32/*
33 * devfreq_work periodically monitors every registered device.
34 * The minimum polling interval is one jiffy. The polling interval is
35 * determined by the minimum polling period among all polling devfreq
36 * devices. The resolution of polling interval is one jiffy.
37 */
38static bool polling;
39static struct workqueue_struct *devfreq_wq;
40static struct delayed_work devfreq_work;
41
42/* wait removing if this is to be removed */
43static struct devfreq *wait_remove_device;
44
45/* The list of all device-devfreq */
46static LIST_HEAD(devfreq_list);
47static DEFINE_MUTEX(devfreq_list_lock);
48
49/**
50 * find_device_devfreq() - find devfreq struct using device pointer
51 * @dev: device pointer used to lookup device devfreq.
52 *
53 * Search the list of device devfreqs and return the matched device's
54 * devfreq info. devfreq_list_lock should be held by the caller.
55 */
56static struct devfreq *find_device_devfreq(struct device *dev)
57{
58    struct devfreq *tmp_devfreq;
59
60    if (unlikely(IS_ERR_OR_NULL(dev))) {
61        pr_err("DEVFREQ: %s: Invalid parameters\n", __func__);
62        return ERR_PTR(-EINVAL);
63    }
64    WARN(!mutex_is_locked(&devfreq_list_lock),
65         "devfreq_list_lock must be locked.");
66
67    list_for_each_entry(tmp_devfreq, &devfreq_list, node) {
68        if (tmp_devfreq->dev.parent == dev)
69            return tmp_devfreq;
70    }
71
72    return ERR_PTR(-ENODEV);
73}
74
75/**
76 * update_devfreq() - Reevaluate the device and configure frequency.
77 * @devfreq: the devfreq instance.
78 *
79 * Note: Lock devfreq->lock before calling update_devfreq
80 * This function is exported for governors.
81 */
82int update_devfreq(struct devfreq *devfreq)
83{
84    unsigned long freq;
85    int err = 0;
86    u32 flags = 0;
87
88    if (!mutex_is_locked(&devfreq->lock)) {
89        WARN(true, "devfreq->lock must be locked by the caller.\n");
90        return -EINVAL;
91    }
92
93    /* Reevaluate the proper frequency */
94    err = devfreq->governor->get_target_freq(devfreq, &freq);
95    if (err)
96        return err;
97
98    /*
99     * Adjust the freuqency with user freq and QoS.
100     *
101     * List from the highest proiority
102     * max_freq (probably called by thermal when it's too hot)
103     * min_freq
104     */
105
106    if (devfreq->min_freq && freq < devfreq->min_freq) {
107        freq = devfreq->min_freq;
108        flags &= ~DEVFREQ_FLAG_LEAST_UPPER_BOUND; /* Use GLB */
109    }
110    if (devfreq->max_freq && freq > devfreq->max_freq) {
111        freq = devfreq->max_freq;
112        flags |= DEVFREQ_FLAG_LEAST_UPPER_BOUND; /* Use LUB */
113    }
114
115    err = devfreq->profile->target(devfreq->dev.parent, &freq, flags);
116    if (err)
117        return err;
118
119    devfreq->previous_freq = freq;
120    return err;
121}
122
123/**
124 * devfreq_notifier_call() - Notify that the device frequency requirements
125 * has been changed out of devfreq framework.
126 * @nb the notifier_block (supposed to be devfreq->nb)
127 * @type not used
128 * @devp not used
129 *
130 * Called by a notifier that uses devfreq->nb.
131 */
132static int devfreq_notifier_call(struct notifier_block *nb, unsigned long type,
133                 void *devp)
134{
135    struct devfreq *devfreq = container_of(nb, struct devfreq, nb);
136    int ret;
137
138    mutex_lock(&devfreq->lock);
139    ret = update_devfreq(devfreq);
140    mutex_unlock(&devfreq->lock);
141
142    return ret;
143}
144
145/**
146 * _remove_devfreq() - Remove devfreq from the device.
147 * @devfreq: the devfreq struct
148 * @skip: skip calling device_unregister().
149 *
150 * Note that the caller should lock devfreq->lock before calling
151 * this. _remove_devfreq() will unlock it and free devfreq
152 * internally. devfreq_list_lock should be locked by the caller
153 * as well (not relased at return)
154 *
155 * Lock usage:
156 * devfreq->lock: locked before call.
157 * unlocked at return (and freed)
158 * devfreq_list_lock: locked before call.
159 * kept locked at return.
160 * if devfreq is centrally polled.
161 *
162 * Freed memory:
163 * devfreq
164 */
165static void _remove_devfreq(struct devfreq *devfreq, bool skip)
166{
167    if (!mutex_is_locked(&devfreq->lock)) {
168        WARN(true, "devfreq->lock must be locked by the caller.\n");
169        return;
170    }
171    if (!devfreq->governor->no_central_polling &&
172        !mutex_is_locked(&devfreq_list_lock)) {
173        WARN(true, "devfreq_list_lock must be locked by the caller.\n");
174        return;
175    }
176
177    if (devfreq->being_removed)
178        return;
179
180    devfreq->being_removed = true;
181
182    if (devfreq->profile->exit)
183        devfreq->profile->exit(devfreq->dev.parent);
184
185    if (devfreq->governor->exit)
186        devfreq->governor->exit(devfreq);
187
188    if (!skip && get_device(&devfreq->dev)) {
189        device_unregister(&devfreq->dev);
190        put_device(&devfreq->dev);
191    }
192
193    if (!devfreq->governor->no_central_polling)
194        list_del(&devfreq->node);
195
196    mutex_unlock(&devfreq->lock);
197    mutex_destroy(&devfreq->lock);
198
199    kfree(devfreq);
200}
201
202/**
203 * devfreq_dev_release() - Callback for struct device to release the device.
204 * @dev: the devfreq device
205 *
206 * This calls _remove_devfreq() if _remove_devfreq() is not called.
207 * Note that devfreq_dev_release() could be called by _remove_devfreq() as
208 * well as by others unregistering the device.
209 */
210static void devfreq_dev_release(struct device *dev)
211{
212    struct devfreq *devfreq = to_devfreq(dev);
213    bool central_polling = !devfreq->governor->no_central_polling;
214
215    /*
216     * If devfreq_dev_release() was called by device_unregister() of
217     * _remove_devfreq(), we cannot mutex_lock(&devfreq->lock) and
218     * being_removed is already set. This also partially checks the case
219     * where devfreq_dev_release() is called from a thread other than
220     * the one called _remove_devfreq(); however, this case is
221     * dealt completely with another following being_removed check.
222     *
223     * Because being_removed is never being
224     * unset, we do not need to worry about race conditions on
225     * being_removed.
226     */
227    if (devfreq->being_removed)
228        return;
229
230    if (central_polling)
231        mutex_lock(&devfreq_list_lock);
232
233    mutex_lock(&devfreq->lock);
234
235    /*
236     * Check being_removed flag again for the case where
237     * devfreq_dev_release() was called in a thread other than the one
238     * possibly called _remove_devfreq().
239     */
240    if (devfreq->being_removed) {
241        mutex_unlock(&devfreq->lock);
242        goto out;
243    }
244
245    /* devfreq->lock is unlocked and removed in _removed_devfreq() */
246    _remove_devfreq(devfreq, true);
247
248out:
249    if (central_polling)
250        mutex_unlock(&devfreq_list_lock);
251}
252
253/**
254 * devfreq_monitor() - Periodically poll devfreq objects.
255 * @work: the work struct used to run devfreq_monitor periodically.
256 *
257 */
258static void devfreq_monitor(struct work_struct *work)
259{
260    static unsigned long last_polled_at;
261    struct devfreq *devfreq, *tmp;
262    int error;
263    unsigned long jiffies_passed;
264    unsigned long next_jiffies = ULONG_MAX, now = jiffies;
265    struct device *dev;
266
267    /* Initially last_polled_at = 0, polling every device at bootup */
268    jiffies_passed = now - last_polled_at;
269    last_polled_at = now;
270    if (jiffies_passed == 0)
271        jiffies_passed = 1;
272
273    mutex_lock(&devfreq_list_lock);
274    list_for_each_entry_safe(devfreq, tmp, &devfreq_list, node) {
275        mutex_lock(&devfreq->lock);
276        dev = devfreq->dev.parent;
277
278        /* Do not remove tmp for a while */
279        wait_remove_device = tmp;
280
281        if (devfreq->governor->no_central_polling ||
282            devfreq->next_polling == 0) {
283            mutex_unlock(&devfreq->lock);
284            continue;
285        }
286        mutex_unlock(&devfreq_list_lock);
287
288        /*
289         * Reduce more next_polling if devfreq_wq took an extra
290         * delay. (i.e., CPU has been idled.)
291         */
292        if (devfreq->next_polling <= jiffies_passed) {
293            error = update_devfreq(devfreq);
294
295            /* Remove a devfreq with an error. */
296            if (error && error != -EAGAIN) {
297
298                dev_err(dev, "Due to update_devfreq error(%d), devfreq(%s) is removed from the device\n",
299                    error, devfreq->governor->name);
300
301                /*
302                 * Unlock devfreq before locking the list
303                 * in order to avoid deadlock with
304                 * find_device_devfreq or others
305                 */
306                mutex_unlock(&devfreq->lock);
307                mutex_lock(&devfreq_list_lock);
308                /* Check if devfreq is already removed */
309                if (IS_ERR(find_device_devfreq(dev)))
310                    continue;
311                mutex_lock(&devfreq->lock);
312                /* This unlocks devfreq->lock and free it */
313                _remove_devfreq(devfreq, false);
314                continue;
315            }
316            devfreq->next_polling = devfreq->polling_jiffies;
317        } else {
318            devfreq->next_polling -= jiffies_passed;
319        }
320
321        if (devfreq->next_polling)
322            next_jiffies = (next_jiffies > devfreq->next_polling) ?
323                    devfreq->next_polling : next_jiffies;
324
325        mutex_unlock(&devfreq->lock);
326        mutex_lock(&devfreq_list_lock);
327    }
328    wait_remove_device = NULL;
329    mutex_unlock(&devfreq_list_lock);
330
331    if (next_jiffies > 0 && next_jiffies < ULONG_MAX) {
332        polling = true;
333        queue_delayed_work(devfreq_wq, &devfreq_work, next_jiffies);
334    } else {
335        polling = false;
336    }
337}
338
339/**
340 * devfreq_add_device() - Add devfreq feature to the device
341 * @dev: the device to add devfreq feature.
342 * @profile: device-specific profile to run devfreq.
343 * @governor: the policy to choose frequency.
344 * @data: private data for the governor. The devfreq framework does not
345 * touch this value.
346 */
347struct devfreq *devfreq_add_device(struct device *dev,
348                   struct devfreq_dev_profile *profile,
349                   const struct devfreq_governor *governor,
350                   void *data)
351{
352    struct devfreq *devfreq;
353    int err = 0;
354
355    if (!dev || !profile || !governor) {
356        dev_err(dev, "%s: Invalid parameters.\n", __func__);
357        return ERR_PTR(-EINVAL);
358    }
359
360
361    if (!governor->no_central_polling) {
362        mutex_lock(&devfreq_list_lock);
363        devfreq = find_device_devfreq(dev);
364        mutex_unlock(&devfreq_list_lock);
365        if (!IS_ERR(devfreq)) {
366            dev_err(dev, "%s: Unable to create devfreq for the device. It already has one.\n", __func__);
367            err = -EINVAL;
368            goto err_out;
369        }
370    }
371
372    devfreq = kzalloc(sizeof(struct devfreq), GFP_KERNEL);
373    if (!devfreq) {
374        dev_err(dev, "%s: Unable to create devfreq for the device\n",
375            __func__);
376        err = -ENOMEM;
377        goto err_out;
378    }
379
380    mutex_init(&devfreq->lock);
381    mutex_lock(&devfreq->lock);
382    devfreq->dev.parent = dev;
383    devfreq->dev.class = devfreq_class;
384    devfreq->dev.release = devfreq_dev_release;
385    devfreq->profile = profile;
386    devfreq->governor = governor;
387    devfreq->previous_freq = profile->initial_freq;
388    devfreq->data = data;
389    devfreq->next_polling = devfreq->polling_jiffies
390                  = msecs_to_jiffies(devfreq->profile->polling_ms);
391    devfreq->nb.notifier_call = devfreq_notifier_call;
392
393    dev_set_name(&devfreq->dev, dev_name(dev));
394    err = device_register(&devfreq->dev);
395    if (err) {
396        put_device(&devfreq->dev);
397        goto err_dev;
398    }
399
400    if (governor->init)
401        err = governor->init(devfreq);
402    if (err)
403        goto err_init;
404
405    mutex_unlock(&devfreq->lock);
406
407    if (governor->no_central_polling)
408        goto out;
409
410    mutex_lock(&devfreq_list_lock);
411
412    list_add(&devfreq->node, &devfreq_list);
413
414    if (devfreq_wq && devfreq->next_polling && !polling) {
415        polling = true;
416        queue_delayed_work(devfreq_wq, &devfreq_work,
417                   devfreq->next_polling);
418    }
419    mutex_unlock(&devfreq_list_lock);
420out:
421    return devfreq;
422
423err_init:
424    device_unregister(&devfreq->dev);
425err_dev:
426    mutex_unlock(&devfreq->lock);
427    kfree(devfreq);
428err_out:
429    return ERR_PTR(err);
430}
431
432/**
433 * devfreq_remove_device() - Remove devfreq feature from a device.
434 * @devfreq the devfreq instance to be removed
435 */
436int devfreq_remove_device(struct devfreq *devfreq)
437{
438    bool central_polling;
439
440    if (!devfreq)
441        return -EINVAL;
442
443    central_polling = !devfreq->governor->no_central_polling;
444
445    if (central_polling) {
446        mutex_lock(&devfreq_list_lock);
447        while (wait_remove_device == devfreq) {
448            mutex_unlock(&devfreq_list_lock);
449            schedule();
450            mutex_lock(&devfreq_list_lock);
451        }
452    }
453
454    mutex_lock(&devfreq->lock);
455    _remove_devfreq(devfreq, false); /* it unlocks devfreq->lock */
456
457    if (central_polling)
458        mutex_unlock(&devfreq_list_lock);
459
460    return 0;
461}
462
463static ssize_t show_governor(struct device *dev,
464                 struct device_attribute *attr, char *buf)
465{
466    return sprintf(buf, "%s\n", to_devfreq(dev)->governor->name);
467}
468
469static ssize_t show_freq(struct device *dev,
470             struct device_attribute *attr, char *buf)
471{
472    return sprintf(buf, "%lu\n", to_devfreq(dev)->previous_freq);
473}
474
475static ssize_t show_polling_interval(struct device *dev,
476                     struct device_attribute *attr, char *buf)
477{
478    return sprintf(buf, "%d\n", to_devfreq(dev)->profile->polling_ms);
479}
480
481static ssize_t store_polling_interval(struct device *dev,
482                      struct device_attribute *attr,
483                      const char *buf, size_t count)
484{
485    struct devfreq *df = to_devfreq(dev);
486    unsigned int value;
487    int ret;
488
489    ret = sscanf(buf, "%u", &value);
490    if (ret != 1)
491        goto out;
492
493    mutex_lock(&df->lock);
494    df->profile->polling_ms = value;
495    df->next_polling = df->polling_jiffies
496             = msecs_to_jiffies(value);
497    mutex_unlock(&df->lock);
498
499    ret = count;
500
501    if (df->governor->no_central_polling)
502        goto out;
503
504    mutex_lock(&devfreq_list_lock);
505    if (df->next_polling > 0 && !polling) {
506        polling = true;
507        queue_delayed_work(devfreq_wq, &devfreq_work,
508                   df->next_polling);
509    }
510    mutex_unlock(&devfreq_list_lock);
511out:
512    return ret;
513}
514
515static ssize_t show_central_polling(struct device *dev,
516                    struct device_attribute *attr, char *buf)
517{
518    return sprintf(buf, "%d\n",
519               !to_devfreq(dev)->governor->no_central_polling);
520}
521
522static ssize_t store_min_freq(struct device *dev, struct device_attribute *attr,
523                  const char *buf, size_t count)
524{
525    struct devfreq *df = to_devfreq(dev);
526    unsigned long value;
527    int ret;
528    unsigned long max;
529
530    ret = sscanf(buf, "%lu", &value);
531    if (ret != 1)
532        goto out;
533
534    mutex_lock(&df->lock);
535    max = df->max_freq;
536    if (value && max && value > max) {
537        ret = -EINVAL;
538        goto unlock;
539    }
540
541    df->min_freq = value;
542    update_devfreq(df);
543    ret = count;
544unlock:
545    mutex_unlock(&df->lock);
546out:
547    return ret;
548}
549
550static ssize_t show_min_freq(struct device *dev, struct device_attribute *attr,
551                 char *buf)
552{
553    return sprintf(buf, "%lu\n", to_devfreq(dev)->min_freq);
554}
555
556static ssize_t store_max_freq(struct device *dev, struct device_attribute *attr,
557                  const char *buf, size_t count)
558{
559    struct devfreq *df = to_devfreq(dev);
560    unsigned long value;
561    int ret;
562    unsigned long min;
563
564    ret = sscanf(buf, "%lu", &value);
565    if (ret != 1)
566        goto out;
567
568    mutex_lock(&df->lock);
569    min = df->min_freq;
570    if (value && min && value < min) {
571        ret = -EINVAL;
572        goto unlock;
573    }
574
575    df->max_freq = value;
576    update_devfreq(df);
577    ret = count;
578unlock:
579    mutex_unlock(&df->lock);
580out:
581    return ret;
582}
583
584static ssize_t show_max_freq(struct device *dev, struct device_attribute *attr,
585                 char *buf)
586{
587    return sprintf(buf, "%lu\n", to_devfreq(dev)->max_freq);
588}
589
590static struct device_attribute devfreq_attrs[] = {
591    __ATTR(governor, S_IRUGO, show_governor, NULL),
592    __ATTR(cur_freq, S_IRUGO, show_freq, NULL),
593    __ATTR(central_polling, S_IRUGO, show_central_polling, NULL),
594    __ATTR(polling_interval, S_IRUGO | S_IWUSR, show_polling_interval,
595           store_polling_interval),
596    __ATTR(min_freq, S_IRUGO | S_IWUSR, show_min_freq, store_min_freq),
597    __ATTR(max_freq, S_IRUGO | S_IWUSR, show_max_freq, store_max_freq),
598    { },
599};
600
601/**
602 * devfreq_start_polling() - Initialize data structure for devfreq framework and
603 * start polling registered devfreq devices.
604 */
605static int __init devfreq_start_polling(void)
606{
607    mutex_lock(&devfreq_list_lock);
608    polling = false;
609    devfreq_wq = create_freezable_workqueue("devfreq_wq");
610    INIT_DELAYED_WORK_DEFERRABLE(&devfreq_work, devfreq_monitor);
611    mutex_unlock(&devfreq_list_lock);
612
613    devfreq_monitor(&devfreq_work.work);
614    return 0;
615}
616late_initcall(devfreq_start_polling);
617
618static int __init devfreq_init(void)
619{
620    devfreq_class = class_create(THIS_MODULE, "devfreq");
621    if (IS_ERR(devfreq_class)) {
622        pr_err("%s: couldn't create class\n", __FILE__);
623        return PTR_ERR(devfreq_class);
624    }
625    devfreq_class->dev_attrs = devfreq_attrs;
626    return 0;
627}
628subsys_initcall(devfreq_init);
629
630static void __exit devfreq_exit(void)
631{
632    class_destroy(devfreq_class);
633}
634module_exit(devfreq_exit);
635
636/*
637 * The followings are helper functions for devfreq user device drivers with
638 * OPP framework.
639 */
640
641/**
642 * devfreq_recommended_opp() - Helper function to get proper OPP for the
643 * freq value given to target callback.
644 * @dev The devfreq user device. (parent of devfreq)
645 * @freq The frequency given to target function
646 * @flags Flags handed from devfreq framework.
647 *
648 */
649struct opp *devfreq_recommended_opp(struct device *dev, unsigned long *freq,
650                    u32 flags)
651{
652    struct opp *opp;
653
654    if (flags & DEVFREQ_FLAG_LEAST_UPPER_BOUND) {
655        /* The freq is an upper bound. opp should be lower */
656        opp = opp_find_freq_floor(dev, freq);
657
658        /* If not available, use the closest opp */
659        if (opp == ERR_PTR(-ENODEV))
660            opp = opp_find_freq_ceil(dev, freq);
661    } else {
662        /* The freq is an lower bound. opp should be higher */
663        opp = opp_find_freq_ceil(dev, freq);
664
665        /* If not available, use the closest opp */
666        if (opp == ERR_PTR(-ENODEV))
667            opp = opp_find_freq_floor(dev, freq);
668    }
669
670    return opp;
671}
672
673/**
674 * devfreq_register_opp_notifier() - Helper function to get devfreq notified
675 * for any changes in the OPP availability
676 * changes
677 * @dev The devfreq user device. (parent of devfreq)
678 * @devfreq The devfreq object.
679 */
680int devfreq_register_opp_notifier(struct device *dev, struct devfreq *devfreq)
681{
682    struct srcu_notifier_head *nh = opp_get_notifier(dev);
683
684    if (IS_ERR(nh))
685        return PTR_ERR(nh);
686    return srcu_notifier_chain_register(nh, &devfreq->nb);
687}
688
689/**
690 * devfreq_unregister_opp_notifier() - Helper function to stop getting devfreq
691 * notified for any changes in the OPP
692 * availability changes anymore.
693 * @dev The devfreq user device. (parent of devfreq)
694 * @devfreq The devfreq object.
695 *
696 * At exit() callback of devfreq_dev_profile, this must be included if
697 * devfreq_recommended_opp is used.
698 */
699int devfreq_unregister_opp_notifier(struct device *dev, struct devfreq *devfreq)
700{
701    struct srcu_notifier_head *nh = opp_get_notifier(dev);
702
703    if (IS_ERR(nh))
704        return PTR_ERR(nh);
705    return srcu_notifier_chain_unregister(nh, &devfreq->nb);
706}
707
708MODULE_AUTHOR("MyungJoo Ham <myungjoo.ham@samsung.com>");
709MODULE_DESCRIPTION("devfreq class support");
710MODULE_LICENSE("GPL");
711

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