summaryrefslogtreecommitdiffstats
path: root/drivers/devfreq/devfreq.c
blob: c189b82f5ececeddc29f97e62bc948ffb3f31961 (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
552
553
554
555
556
557
558
559
560
561
562
563
564
565
566
567
568
569
570
571
572
573
574
575
576
577
578
579
580
581
582
583
584
585
586
587
588
589
590
591
592
593
594
595
596
597
598
599
600
601
602
603
604
605
606
/*
 * devfreq: Generic Dynamic Voltage and Frequency Scaling (DVFS) Framework
 *	    for Non-CPU Devices.
 *
 * Copyright (C) 2011 Samsung Electronics
 *	MyungJoo Ham <myungjoo.ham@samsung.com>
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License version 2 as
 * published by the Free Software Foundation.
 */

#include <linux/kernel.h>
#include <linux/sched.h>
#include <linux/errno.h>
#include <linux/err.h>
#include <linux/init.h>
#include <linux/module.h>
#include <linux/slab.h>
#include <linux/stat.h>
#include <linux/opp.h>
#include <linux/devfreq.h>
#include <linux/workqueue.h>
#include <linux/platform_device.h>
#include <linux/list.h>
#include <linux/printk.h>
#include <linux/hrtimer.h>
#include "governor.h"

struct class *devfreq_class;

/*
 * devfreq_work periodically monitors every registered device.
 * The minimum polling interval is one jiffy. The polling interval is
 * determined by the minimum polling period among all polling devfreq
 * devices. The resolution of polling interval is one jiffy.
 */
static bool polling;
static struct workqueue_struct *devfreq_wq;
static struct delayed_work devfreq_work;

/* wait removing if this is to be removed */
static struct devfreq *wait_remove_device;

/* The list of all device-devfreq */
static LIST_HEAD(devfreq_list);
static DEFINE_MUTEX(devfreq_list_lock);

/**
 * find_device_devfreq() - find devfreq struct using device pointer
 * @dev:	device pointer used to lookup device devfreq.
 *
 * Search the list of device devfreqs and return the matched device's
 * devfreq info. devfreq_list_lock should be held by the caller.
 */
static struct devfreq *find_device_devfreq(struct device *dev)
{
	struct devfreq *tmp_devfreq;

	if (unlikely(IS_ERR_OR_NULL(dev))) {
		pr_err("DEVFREQ: %s: Invalid parameters\n", __func__);
		return ERR_PTR(-EINVAL);
	}
	WARN(!mutex_is_locked(&devfreq_list_lock),
	     "devfreq_list_lock must be locked.");

	list_for_each_entry(tmp_devfreq, &devfreq_list, node) {
		if (tmp_devfreq->dev.parent == dev)
			return tmp_devfreq;
	}

	return ERR_PTR(-ENODEV);
}

/**
 * update_devfreq() - Reevaluate the device and configure frequency.
 * @devfreq:	the devfreq instance.
 *
 * Note: Lock devfreq->lock before calling update_devfreq
 *	 This function is exported for governors.
 */
int update_devfreq(struct devfreq *devfreq)
{
	unsigned long freq;
	int err = 0;

	if (!mutex_is_locked(&devfreq->lock)) {
		WARN(true, "devfreq->lock must be locked by the caller.\n");
		return -EINVAL;
	}

	/* Reevaluate the proper frequency */
	err = devfreq->governor->get_target_freq(devfreq, &freq);
	if (err)
		return err;

	err = devfreq->profile->target(devfreq->dev.parent, &freq);
	if (err)
		return err;

	devfreq->previous_freq = freq;
	return err;
}

/**
 * devfreq_notifier_call() - Notify that the device frequency requirements
 *			   has been changed out of devfreq framework.
 * @nb		the notifier_block (supposed to be devfreq->nb)
 * @type	not used
 * @devp	not used
 *
 * Called by a notifier that uses devfreq->nb.
 */
static int devfreq_notifier_call(struct notifier_block *nb, unsigned long type,
				 void *devp)
{
	struct devfreq *devfreq = container_of(nb, struct devfreq, nb);
	int ret;

	mutex_lock(&devfreq->lock);
	ret = update_devfreq(devfreq);
	mutex_unlock(&devfreq->lock);

	return ret;
}

/**
 * _remove_devfreq() - Remove devfreq from the device.
 * @devfreq:	the devfreq struct
 * @skip:	skip calling device_unregister().
 *
 * Note that the caller should lock devfreq->lock before calling
 * this. _remove_devfreq() will unlock it and free devfreq
 * internally. devfreq_list_lock should be locked by the caller
 * as well (not relased at return)
 *
 * Lock usage:
 * devfreq->lock: locked before call.
 *		  unlocked at return (and freed)
 * devfreq_list_lock: locked before call.
 *		      kept locked at return.
 *		      if devfreq is centrally polled.
 *
 * Freed memory:
 * devfreq
 */
static void _remove_devfreq(struct devfreq *devfreq, bool skip)
{
	if (!mutex_is_locked(&devfreq->lock)) {
		WARN(true, "devfreq->lock must be locked by the caller.\n");
		return;
	}
	if (!devfreq->governor->no_central_polling &&
	    !mutex_is_locked(&devfreq_list_lock)) {
		WARN(true, "devfreq_list_lock must be locked by the caller.\n");
		return;
	}

	if (devfreq->being_removed)
		return;

	devfreq->being_removed = true;

	if (devfreq->profile->exit)
		devfreq->profile->exit(devfreq->dev.parent);

	if (devfreq->governor->exit)
		devfreq->governor->exit(devfreq);

	if (!skip && get_device(&devfreq->dev)) {
		device_unregister(&devfreq->dev);
		put_device(&devfreq->dev);
	}

	if (!devfreq->governor->no_central_polling)
		list_del(&devfreq->node);

	mutex_unlock(&devfreq->lock);
	mutex_destroy(&devfreq->lock);

	kfree(devfreq);
}

/**
 * devfreq_dev_release() - Callback for struct device to release the device.
 * @dev:	the devfreq device
 *
 * This calls _remove_devfreq() if _remove_devfreq() is not called.
 * Note that devfreq_dev_release() could be called by _remove_devfreq() as
 * well as by others unregistering the device.
 */
static void devfreq_dev_release(struct device *dev)
{
	struct devfreq *devfreq = to_devfreq(dev);
	bool central_polling = !devfreq->governor->no_central_polling;

	/*
	 * If devfreq_dev_release() was called by device_unregister() of
	 * _remove_devfreq(), we cannot mutex_lock(&devfreq->lock) and
	 * being_removed is already set. This also partially checks the case
	 * where devfreq_dev_release() is called from a thread other than
	 * the one called _remove_devfreq(); however, this case is
	 * dealt completely with another following being_removed check.
	 *
	 * Because being_removed is never being
	 * unset, we do not need to worry about race conditions on
	 * being_removed.
	 */
	if (devfreq->being_removed)
		return;

	if (central_polling)
		mutex_lock(&devfreq_list_lock);

	mutex_lock(&devfreq->lock);

	/*
	 * Check being_removed flag again for the case where
	 * devfreq_dev_release() was called in a thread other than the one
	 * possibly called _remove_devfreq().
	 */
	if (devfreq->being_removed) {
		mutex_unlock(&devfreq->lock);
		goto out;
	}

	/* devfreq->lock is unlocked and removed in _removed_devfreq() */
	_remove_devfreq(devfreq, true);

out:
	if (central_polling)
		mutex_unlock(&devfreq_list_lock);
}

/**
 * devfreq_monitor() - Periodically poll devfreq objects.
 * @work: the work struct used to run devfreq_monitor periodically.
 *
 */
static void devfreq_monitor(struct work_struct *work)
{
	static unsigned long last_polled_at;
	struct devfreq *devfreq, *tmp;
	int error;
	unsigned long jiffies_passed;
	unsigned long next_jiffies = ULONG_MAX, now = jiffies;
	struct device *dev;

	/* Initially last_polled_at = 0, polling every device at bootup */
	jiffies_passed = now - last_polled_at;
	last_polled_at = now;
	if (jiffies_passed == 0)
		jiffies_passed = 1;

	mutex_lock(&devfreq_list_lock);
	list_for_each_entry_safe(devfreq, tmp, &devfreq_list, node) {
		mutex_lock(&devfreq->lock);
		dev = devfreq->dev.parent;

		/* Do not remove tmp for a while */
		wait_remove_device = tmp;

		if (devfreq->governor->no_central_polling ||
		    devfreq->next_polling == 0) {
			mutex_unlock(&devfreq->lock);
			continue;
		}
		mutex_unlock(&devfreq_list_lock);

		/*
		 * Reduce more next_polling if devfreq_wq took an extra
		 * delay. (i.e., CPU has been idled.)
		 */
		if (devfreq->next_polling <= jiffies_passed) {
			error = update_devfreq(devfreq);

			/* Remove a devfreq with an error. */
			if (error && error != -EAGAIN) {

				dev_err(dev, "Due to update_devfreq error(%d), devfreq(%s) is removed from the device\n",
					error, devfreq->governor->name);

				/*
				 * Unlock devfreq before locking the list
				 * in order to avoid deadlock with
				 * find_device_devfreq or others
				 */
				mutex_unlock(&devfreq->lock);
				mutex_lock(&devfreq_list_lock);
				/* Check if devfreq is already removed */
				if (IS_ERR(find_device_devfreq(dev)))
					continue;
				mutex_lock(&devfreq->lock);
				/* This unlocks devfreq->lock and free it */
				_remove_devfreq(devfreq, false);
				continue;
			}
			devfreq->next_polling = devfreq->polling_jiffies;
		} else {
			devfreq->next_polling -= jiffies_passed;
		}

		if (devfreq->next_polling)
			next_jiffies = (next_jiffies > devfreq->next_polling) ?
					devfreq->next_polling : next_jiffies;

		mutex_unlock(&devfreq->lock);
		mutex_lock(&devfreq_list_lock);
	}
	wait_remove_device = NULL;
	mutex_unlock(&devfreq_list_lock);

	if (next_jiffies > 0 && next_jiffies < ULONG_MAX) {
		polling = true;
		queue_delayed_work(devfreq_wq, &devfreq_work, next_jiffies);
	} else {
		polling = false;
	}
}

/**
 * devfreq_add_device() - Add devfreq feature to the device
 * @dev:	the device to add devfreq feature.
 * @profile:	device-specific profile to run devfreq.
 * @governor:	the policy to choose frequency.
 * @data:	private data for the governor. The devfreq framework does not
 *		touch this value.
 */
struct devfreq *devfreq_add_device(struct device *dev,
				   struct devfreq_dev_profile *profile,
				   const struct devfreq_governor *governor,
				   void *data)
{
	struct devfreq *devfreq;
	int err = 0;

	if (!dev || !profile || !governor) {
		dev_err(dev, "%s: Invalid parameters.\n", __func__);
		return ERR_PTR(-EINVAL);
	}


	if (!governor->no_central_polling) {
		mutex_lock(&devfreq_list_lock);
		devfreq = find_device_devfreq(dev);
		mutex_unlock(&devfreq_list_lock);
		if (!IS_ERR(devfreq)) {
			dev_err(dev, "%s: Unable to create devfreq for the device. It already has one.\n", __func__);
			err = -EINVAL;
			goto err_out;
		}
	}

	devfreq = kzalloc(sizeof(struct devfreq), GFP_KERNEL);
	if (!devfreq) {
		dev_err(dev, "%s: Unable to create devfreq for the device\n",
			__func__);
		err = -ENOMEM;
		goto err_out;
	}

	mutex_init(&devfreq->lock);
	mutex_lock(&devfreq->lock);
	devfreq->dev.parent = dev;
	devfreq->dev.class = devfreq_class;
	devfreq->dev.release = devfreq_dev_release;
	devfreq->profile = profile;
	devfreq->governor = governor;
	devfreq->previous_freq = profile->initial_freq;
	devfreq->data = data;
	devfreq->next_polling = devfreq->polling_jiffies
			      = msecs_to_jiffies(devfreq->profile->polling_ms);
	devfreq->nb.notifier_call = devfreq_notifier_call;

	dev_set_name(&devfreq->dev, dev_name(dev));
	err = device_register(&devfreq->dev);
	if (err) {
		put_device(&devfreq->dev);
		goto err_dev;
	}

	if (governor->init)
		err = governor->init(devfreq);
	if (err)
		goto err_init;

	mutex_unlock(&devfreq->lock);

	if (governor->no_central_polling)
		goto out;

	mutex_lock(&devfreq_list_lock);

	list_add(&devfreq->node, &devfreq_list);

	if (devfreq_wq && devfreq->next_polling && !polling) {
		polling = true;
		queue_delayed_work(devfreq_wq, &devfreq_work,
				   devfreq->next_polling);
	}
	mutex_unlock(&devfreq_list_lock);
out:
	return devfreq;

err_init:
	device_unregister(&devfreq->dev);
err_dev:
	mutex_unlock(&devfreq->lock);
	kfree(devfreq);
err_out:
	return ERR_PTR(err);
}

/**
 * devfreq_remove_device() - Remove devfreq feature from a device.
 * @devfreq	the devfreq instance to be removed
 */
int devfreq_remove_device(struct devfreq *devfreq)
{
	bool central_polling;

	if (!devfreq)
		return -EINVAL;

	central_polling = !devfreq->governor->no_central_polling;

	if (central_polling) {
		mutex_lock(&devfreq_list_lock);
		while (wait_remove_device == devfreq) {
			mutex_unlock(&devfreq_list_lock);
			schedule();
			mutex_lock(&devfreq_list_lock);
		}
	}

	mutex_lock(&devfreq->lock);
	_remove_devfreq(devfreq, false); /* it unlocks devfreq->lock */

	if (central_polling)
		mutex_unlock(&devfreq_list_lock);

	return 0;
}

static ssize_t show_governor(struct device *dev,
			     struct device_attribute *attr, char *buf)
{
	return sprintf(buf, "%s\n", to_devfreq(dev)->governor->name);
}

static ssize_t show_freq(struct device *dev,
			 struct device_attribute *attr, char *buf)
{
	return sprintf(buf, "%lu\n", to_devfreq(dev)->previous_freq);
}

static ssize_t show_polling_interval(struct device *dev,
				     struct device_attribute *attr, char *buf)
{
	return sprintf(buf, "%d\n", to_devfreq(dev)->profile->polling_ms);
}

static ssize_t store_polling_interval(struct device *dev,
				      struct device_attribute *attr,
				      const char *buf, size_t count)
{
	struct devfreq *df = to_devfreq(dev);
	unsigned int value;
	int ret;

	ret = sscanf(buf, "%u", &value);
	if (ret != 1)
		goto out;

	mutex_lock(&df->lock);
	df->profile->polling_ms = value;
	df->next_polling = df->polling_jiffies
			 = msecs_to_jiffies(value);
	mutex_unlock(&df->lock);

	ret = count;

	if (df->governor->no_central_polling)
		goto out;

	mutex_lock(&devfreq_list_lock);
	if (df->next_polling > 0 && !polling) {
		polling = true;
		queue_delayed_work(devfreq_wq, &devfreq_work,
				   df->next_polling);
	}
	mutex_unlock(&devfreq_list_lock);
out:
	return ret;
}

static ssize_t show_central_polling(struct device *dev,
				    struct device_attribute *attr, char *buf)
{
	return sprintf(buf, "%d\n",
		       !to_devfreq(dev)->governor->no_central_polling);
}

static struct device_attribute devfreq_attrs[] = {
	__ATTR(governor, S_IRUGO, show_governor, NULL),
	__ATTR(cur_freq, S_IRUGO, show_freq, NULL),
	__ATTR(central_polling, S_IRUGO, show_central_polling, NULL),
	__ATTR(polling_interval, S_IRUGO | S_IWUSR, show_polling_interval,
	       store_polling_interval),
	{ },
};

/**
 * devfreq_start_polling() - Initialize data structure for devfreq framework and
 *			   start polling registered devfreq devices.
 */
static int __init devfreq_start_polling(void)
{
	mutex_lock(&devfreq_list_lock);
	polling = false;
	devfreq_wq = create_freezable_workqueue("devfreq_wq");
	INIT_DELAYED_WORK_DEFERRABLE(&devfreq_work, devfreq_monitor);
	mutex_unlock(&devfreq_list_lock);

	devfreq_monitor(&devfreq_work.work);
	return 0;
}
late_initcall(devfreq_start_polling);

static int __init devfreq_init(void)
{
	devfreq_class = class_create(THIS_MODULE, "devfreq");
	if (IS_ERR(devfreq_class)) {
		pr_err("%s: couldn't create class\n", __FILE__);
		return PTR_ERR(devfreq_class);
	}
	devfreq_class->dev_attrs = devfreq_attrs;
	return 0;
}
subsys_initcall(devfreq_init);

static void __exit devfreq_exit(void)
{
	class_destroy(devfreq_class);
}
module_exit(devfreq_exit);

/*
 * The followings are helper functions for devfreq user device drivers with
 * OPP framework.
 */

/**
 * devfreq_recommended_opp() - Helper function to get proper OPP for the
 *			     freq value given to target callback.
 * @dev		The devfreq user device. (parent of devfreq)
 * @freq	The frequency given to target function
 *
 */
struct opp *devfreq_recommended_opp(struct device *dev, unsigned long *freq)
{
	struct opp *opp = opp_find_freq_ceil(dev, freq);

	if (opp == ERR_PTR(-ENODEV))
		opp = opp_find_freq_floor(dev, freq);
	return opp;
}

/**
 * devfreq_register_opp_notifier() - Helper function to get devfreq notified
 *				   for any changes in the OPP availability
 *				   changes
 * @dev		The devfreq user device. (parent of devfreq)
 * @devfreq	The devfreq object.
 */
int devfreq_register_opp_notifier(struct device *dev, struct devfreq *devfreq)
{
	struct srcu_notifier_head *nh = opp_get_notifier(dev);

	if (IS_ERR(nh))
		return PTR_ERR(nh);
	return srcu_notifier_chain_register(nh, &devfreq->nb);
}

/**
 * devfreq_unregister_opp_notifier() - Helper function to stop getting devfreq
 *				     notified for any changes in the OPP
 *				     availability changes anymore.
 * @dev		The devfreq user device. (parent of devfreq)
 * @devfreq	The devfreq object.
 *
 * At exit() callback of devfreq_dev_profile, this must be included if
 * devfreq_recommended_opp is used.
 */
int devfreq_unregister_opp_notifier(struct device *dev, struct devfreq *devfreq)
{
	struct srcu_notifier_head *nh = opp_get_notifier(dev);

	if (IS_ERR(nh))
		return PTR_ERR(nh);
	return srcu_notifier_chain_unregister(nh, &devfreq->nb);
}

MODULE_AUTHOR("MyungJoo Ham <myungjoo.ham@samsung.com>");
MODULE_DESCRIPTION("devfreq class support");
MODULE_LICENSE("GPL");
OpenPOWER on IntegriCloud