summaryrefslogtreecommitdiff
path: root/drivers/base/power/clock_ops.c
blob: 84d5acb6301b751152ae6f28af5a76f0b1df16c0 (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
607
608
609
610
611
612
613
614
615
616
617
618
619
620
621
622
623
624
625
626
627
628
629
630
631
632
633
634
635
636
637
638
639
640
641
642
643
644
645
646
647
648
649
650
651
652
653
654
655
656
657
658
659
660
661
662
663
664
665
666
667
668
669
670
671
672
673
674
675
676
677
678
679
680
681
682
683
684
685
686
687
688
689
690
691
692
693
694
695
696
697
698
699
700
701
702
703
704
705
706
707
708
709
710
711
712
713
714
715
716
717
718
719
720
721
722
723
724
725
726
727
728
729
730
731
732
733
734
735
736
737
738
739
740
741
742
743
744
745
746
747
748
749
750
751
752
753
754
755
756
757
758
759
760
761
762
763
764
765
766
767
768
769
770
771
772
773
774
775
776
777
778
779
780
781
782
783
784
785
786
787
788
// SPDX-License-Identifier: GPL-2.0
/*
 * drivers/base/power/clock_ops.c - Generic clock manipulation PM callbacks
 *
 * Copyright (c) 2011 Rafael J. Wysocki <rjw@sisk.pl>, Renesas Electronics Corp.
 */

#include <linux/kernel.h>
#include <linux/device.h>
#include <linux/io.h>
#include <linux/pm.h>
#include <linux/pm_clock.h>
#include <linux/clk.h>
#include <linux/clkdev.h>
#include <linux/of_clk.h>
#include <linux/slab.h>
#include <linux/err.h>
#include <linux/pm_domain.h>
#include <linux/pm_runtime.h>

#ifdef CONFIG_PM_CLK

enum pce_status {
	PCE_STATUS_NONE = 0,
	PCE_STATUS_ACQUIRED,
	PCE_STATUS_PREPARED,
	PCE_STATUS_ENABLED,
	PCE_STATUS_ERROR,
};

struct pm_clock_entry {
	struct list_head node;
	char *con_id;
	struct clk *clk;
	enum pce_status status;
	bool enabled_when_prepared;
};

/**
 * pm_clk_list_lock - ensure exclusive access for modifying the PM clock
 *		      entry list.
 * @psd: pm_subsys_data instance corresponding to the PM clock entry list
 *	 and clk_op_might_sleep count to be modified.
 *
 * Get exclusive access before modifying the PM clock entry list and the
 * clock_op_might_sleep count to guard against concurrent modifications.
 * This also protects against a concurrent clock_op_might_sleep and PM clock
 * entry list usage in pm_clk_suspend()/pm_clk_resume() that may or may not
 * happen in atomic context, hence both the mutex and the spinlock must be
 * taken here.
 */
static void pm_clk_list_lock(struct pm_subsys_data *psd)
	__acquires(&psd->lock)
{
	mutex_lock(&psd->clock_mutex);
	spin_lock_irq(&psd->lock);
}

/**
 * pm_clk_list_unlock - counterpart to pm_clk_list_lock().
 * @psd: the same pm_subsys_data instance previously passed to
 *	 pm_clk_list_lock().
 */
static void pm_clk_list_unlock(struct pm_subsys_data *psd)
	__releases(&psd->lock)
{
	spin_unlock_irq(&psd->lock);
	mutex_unlock(&psd->clock_mutex);
}

/**
 * pm_clk_op_lock - ensure exclusive access for performing clock operations.
 * @psd: pm_subsys_data instance corresponding to the PM clock entry list
 *	 and clk_op_might_sleep count being used.
 * @flags: stored irq flags.
 * @fn: string for the caller function's name.
 *
 * This is used by pm_clk_suspend() and pm_clk_resume() to guard
 * against concurrent modifications to the clock entry list and the
 * clock_op_might_sleep count. If clock_op_might_sleep is != 0 then
 * only the mutex can be locked and those functions can only be used in
 * non atomic context. If clock_op_might_sleep == 0 then these functions
 * may be used in any context and only the spinlock can be locked.
 * Returns -EINVAL if called in atomic context when clock ops might sleep.
 */
static int pm_clk_op_lock(struct pm_subsys_data *psd, unsigned long *flags,
			  const char *fn)
	/* sparse annotations don't work here as exit state isn't static */
{
	bool atomic_context = in_atomic() || irqs_disabled();

try_again:
	spin_lock_irqsave(&psd->lock, *flags);
	if (!psd->clock_op_might_sleep) {
		/* the __release is there to work around sparse limitations */
		__release(&psd->lock);
		return 0;
	}

	/* bail out if in atomic context */
	if (atomic_context) {
		pr_err("%s: atomic context with clock_ops_might_sleep = %d",
		       fn, psd->clock_op_might_sleep);
		spin_unlock_irqrestore(&psd->lock, *flags);
		might_sleep();
		return -EPERM;
	}

	/* we must switch to the mutex */
	spin_unlock_irqrestore(&psd->lock, *flags);
	mutex_lock(&psd->clock_mutex);

	/*
	 * There was a possibility for psd->clock_op_might_sleep
	 * to become 0 above. Keep the mutex only if not the case.
	 */
	if (likely(psd->clock_op_might_sleep))
		return 0;

	mutex_unlock(&psd->clock_mutex);
	goto try_again;
}

/**
 * pm_clk_op_unlock - counterpart to pm_clk_op_lock().
 * @psd: the same pm_subsys_data instance previously passed to
 *	 pm_clk_op_lock().
 * @flags: irq flags provided by pm_clk_op_lock().
 */
static void pm_clk_op_unlock(struct pm_subsys_data *psd, unsigned long *flags)
	/* sparse annotations don't work here as entry state isn't static */
{
	if (psd->clock_op_might_sleep) {
		mutex_unlock(&psd->clock_mutex);
	} else {
		/* the __acquire is there to work around sparse limitations */
		__acquire(&psd->lock);
		spin_unlock_irqrestore(&psd->lock, *flags);
	}
}

/**
 * pm_clk_enable - Enable a clock, reporting any errors
 * @dev: The device for the given clock
 * @ce: PM clock entry corresponding to the clock.
 */
static inline void __pm_clk_enable(struct device *dev, struct pm_clock_entry *ce)
{
	int ret;

	switch (ce->status) {
	case PCE_STATUS_ACQUIRED:
		ret = clk_prepare_enable(ce->clk);
		break;
	case PCE_STATUS_PREPARED:
		ret = clk_enable(ce->clk);
		break;
	default:
		return;
	}
	if (!ret)
		ce->status = PCE_STATUS_ENABLED;
	else
		dev_err(dev, "%s: failed to enable clk %p, error %d\n",
			__func__, ce->clk, ret);
}

/**
 * pm_clk_acquire - Acquire a device clock.
 * @dev: Device whose clock is to be acquired.
 * @ce: PM clock entry corresponding to the clock.
 */
static void pm_clk_acquire(struct device *dev, struct pm_clock_entry *ce)
{
	if (!ce->clk)
		ce->clk = clk_get(dev, ce->con_id);
	if (IS_ERR(ce->clk)) {
		ce->status = PCE_STATUS_ERROR;
		return;
	} else if (clk_is_enabled_when_prepared(ce->clk)) {
		/* we defer preparing the clock in that case */
		ce->status = PCE_STATUS_ACQUIRED;
		ce->enabled_when_prepared = true;
	} else if (clk_prepare(ce->clk)) {
		ce->status = PCE_STATUS_ERROR;
		dev_err(dev, "clk_prepare() failed\n");
		return;
	} else {
		ce->status = PCE_STATUS_PREPARED;
	}
	dev_dbg(dev, "Clock %pC con_id %s managed by runtime PM.\n",
		ce->clk, ce->con_id);
}

static int __pm_clk_add(struct device *dev, const char *con_id,
			struct clk *clk)
{
	struct pm_subsys_data *psd = dev_to_psd(dev);
	struct pm_clock_entry *ce;

	if (!psd)
		return -EINVAL;

	ce = kzalloc(sizeof(*ce), GFP_KERNEL);
	if (!ce)
		return -ENOMEM;

	if (con_id) {
		ce->con_id = kstrdup(con_id, GFP_KERNEL);
		if (!ce->con_id) {
			kfree(ce);
			return -ENOMEM;
		}
	} else {
		if (IS_ERR(clk)) {
			kfree(ce);
			return -ENOENT;
		}
		ce->clk = clk;
	}

	pm_clk_acquire(dev, ce);

	pm_clk_list_lock(psd);
	list_add_tail(&ce->node, &psd->clock_list);
	if (ce->enabled_when_prepared)
		psd->clock_op_might_sleep++;
	pm_clk_list_unlock(psd);
	return 0;
}

/**
 * pm_clk_add - Start using a device clock for power management.
 * @dev: Device whose clock is going to be used for power management.
 * @con_id: Connection ID of the clock.
 *
 * Add the clock represented by @con_id to the list of clocks used for
 * the power management of @dev.
 */
int pm_clk_add(struct device *dev, const char *con_id)
{
	return __pm_clk_add(dev, con_id, NULL);
}
EXPORT_SYMBOL_GPL(pm_clk_add);

/**
 * pm_clk_add_clk - Start using a device clock for power management.
 * @dev: Device whose clock is going to be used for power management.
 * @clk: Clock pointer
 *
 * Add the clock to the list of clocks used for the power management of @dev.
 * The power-management code will take control of the clock reference, so
 * callers should not call clk_put() on @clk after this function sucessfully
 * returned.
 */
int pm_clk_add_clk(struct device *dev, struct clk *clk)
{
	return __pm_clk_add(dev, NULL, clk);
}
EXPORT_SYMBOL_GPL(pm_clk_add_clk);


/**
 * of_pm_clk_add_clk - Start using a device clock for power management.
 * @dev: Device whose clock is going to be used for power management.
 * @name: Name of clock that is going to be used for power management.
 *
 * Add the clock described in the 'clocks' device-tree node that matches
 * with the 'name' provided, to the list of clocks used for the power
 * management of @dev. On success, returns 0. Returns a negative error
 * code if the clock is not found or cannot be added.
 */
int of_pm_clk_add_clk(struct device *dev, const char *name)
{
	struct clk *clk;
	int ret;

	if (!dev || !dev->of_node || !name)
		return -EINVAL;

	clk = of_clk_get_by_name(dev->of_node, name);
	if (IS_ERR(clk))
		return PTR_ERR(clk);

	ret = pm_clk_add_clk(dev, clk);
	if (ret) {
		clk_put(clk);
		return ret;
	}

	return 0;
}
EXPORT_SYMBOL_GPL(of_pm_clk_add_clk);

/**
 * of_pm_clk_add_clks - Start using device clock(s) for power management.
 * @dev: Device whose clock(s) is going to be used for power management.
 *
 * Add a series of clocks described in the 'clocks' device-tree node for
 * a device to the list of clocks used for the power management of @dev.
 * On success, returns the number of clocks added. Returns a negative
 * error code if there are no clocks in the device node for the device
 * or if adding a clock fails.
 */
int of_pm_clk_add_clks(struct device *dev)
{
	struct clk **clks;
	int i, count;
	int ret;

	if (!dev || !dev->of_node)
		return -EINVAL;

	count = of_clk_get_parent_count(dev->of_node);
	if (count <= 0)
		return -ENODEV;

	clks = kcalloc(count, sizeof(*clks), GFP_KERNEL);
	if (!clks)
		return -ENOMEM;

	for (i = 0; i < count; i++) {
		clks[i] = of_clk_get(dev->of_node, i);
		if (IS_ERR(clks[i])) {
			ret = PTR_ERR(clks[i]);
			goto error;
		}

		ret = pm_clk_add_clk(dev, clks[i]);
		if (ret) {
			clk_put(clks[i]);
			goto error;
		}
	}

	kfree(clks);

	return i;

error:
	while (i--)
		pm_clk_remove_clk(dev, clks[i]);

	kfree(clks);

	return ret;
}
EXPORT_SYMBOL_GPL(of_pm_clk_add_clks);

/**
 * __pm_clk_remove - Destroy PM clock entry.
 * @ce: PM clock entry to destroy.
 */
static void __pm_clk_remove(struct pm_clock_entry *ce)
{
	if (!ce)
		return;

	switch (ce->status) {
	case PCE_STATUS_ENABLED:
		clk_disable(ce->clk);
		fallthrough;
	case PCE_STATUS_PREPARED:
		clk_unprepare(ce->clk);
		fallthrough;
	case PCE_STATUS_ACQUIRED:
	case PCE_STATUS_ERROR:
		if (!IS_ERR(ce->clk))
			clk_put(ce->clk);
		break;
	default:
		break;
	}

	kfree(ce->con_id);
	kfree(ce);
}

/**
 * pm_clk_remove - Stop using a device clock for power management.
 * @dev: Device whose clock should not be used for PM any more.
 * @con_id: Connection ID of the clock.
 *
 * Remove the clock represented by @con_id from the list of clocks used for
 * the power management of @dev.
 */
void pm_clk_remove(struct device *dev, const char *con_id)
{
	struct pm_subsys_data *psd = dev_to_psd(dev);
	struct pm_clock_entry *ce;

	if (!psd)
		return;

	pm_clk_list_lock(psd);

	list_for_each_entry(ce, &psd->clock_list, node) {
		if (!con_id && !ce->con_id)
			goto remove;
		else if (!con_id || !ce->con_id)
			continue;
		else if (!strcmp(con_id, ce->con_id))
			goto remove;
	}

	pm_clk_list_unlock(psd);
	return;

 remove:
	list_del(&ce->node);
	if (ce->enabled_when_prepared)
		psd->clock_op_might_sleep--;
	pm_clk_list_unlock(psd);

	__pm_clk_remove(ce);
}
EXPORT_SYMBOL_GPL(pm_clk_remove);

/**
 * pm_clk_remove_clk - Stop using a device clock for power management.
 * @dev: Device whose clock should not be used for PM any more.
 * @clk: Clock pointer
 *
 * Remove the clock pointed to by @clk from the list of clocks used for
 * the power management of @dev.
 */
void pm_clk_remove_clk(struct device *dev, struct clk *clk)
{
	struct pm_subsys_data *psd = dev_to_psd(dev);
	struct pm_clock_entry *ce;

	if (!psd || !clk)
		return;

	pm_clk_list_lock(psd);

	list_for_each_entry(ce, &psd->clock_list, node) {
		if (clk == ce->clk)
			goto remove;
	}

	pm_clk_list_unlock(psd);
	return;

 remove:
	list_del(&ce->node);
	if (ce->enabled_when_prepared)
		psd->clock_op_might_sleep--;
	pm_clk_list_unlock(psd);

	__pm_clk_remove(ce);
}
EXPORT_SYMBOL_GPL(pm_clk_remove_clk);

/**
 * pm_clk_init - Initialize a device's list of power management clocks.
 * @dev: Device to initialize the list of PM clocks for.
 *
 * Initialize the lock and clock_list members of the device's pm_subsys_data
 * object, set the count of clocks that might sleep to 0.
 */
void pm_clk_init(struct device *dev)
{
	struct pm_subsys_data *psd = dev_to_psd(dev);
	if (psd) {
		INIT_LIST_HEAD(&psd->clock_list);
		mutex_init(&psd->clock_mutex);
		psd->clock_op_might_sleep = 0;
	}
}
EXPORT_SYMBOL_GPL(pm_clk_init);

/**
 * pm_clk_create - Create and initialize a device's list of PM clocks.
 * @dev: Device to create and initialize the list of PM clocks for.
 *
 * Allocate a struct pm_subsys_data object, initialize its lock and clock_list
 * members and make the @dev's power.subsys_data field point to it.
 */
int pm_clk_create(struct device *dev)
{
	return dev_pm_get_subsys_data(dev);
}
EXPORT_SYMBOL_GPL(pm_clk_create);

/**
 * pm_clk_destroy - Destroy a device's list of power management clocks.
 * @dev: Device to destroy the list of PM clocks for.
 *
 * Clear the @dev's power.subsys_data field, remove the list of clock entries
 * from the struct pm_subsys_data object pointed to by it before and free
 * that object.
 */
void pm_clk_destroy(struct device *dev)
{
	struct pm_subsys_data *psd = dev_to_psd(dev);
	struct pm_clock_entry *ce, *c;
	struct list_head list;

	if (!psd)
		return;

	INIT_LIST_HEAD(&list);

	pm_clk_list_lock(psd);

	list_for_each_entry_safe_reverse(ce, c, &psd->clock_list, node)
		list_move(&ce->node, &list);
	psd->clock_op_might_sleep = 0;

	pm_clk_list_unlock(psd);

	dev_pm_put_subsys_data(dev);

	list_for_each_entry_safe_reverse(ce, c, &list, node) {
		list_del(&ce->node);
		__pm_clk_remove(ce);
	}
}
EXPORT_SYMBOL_GPL(pm_clk_destroy);

/**
 * pm_clk_suspend - Disable clocks in a device's PM clock list.
 * @dev: Device to disable the clocks for.
 */
int pm_clk_suspend(struct device *dev)
{
	struct pm_subsys_data *psd = dev_to_psd(dev);
	struct pm_clock_entry *ce;
	unsigned long flags;
	int ret;

	dev_dbg(dev, "%s()\n", __func__);

	if (!psd)
		return 0;

	ret = pm_clk_op_lock(psd, &flags, __func__);
	if (ret)
		return ret;

	list_for_each_entry_reverse(ce, &psd->clock_list, node) {
		if (ce->status == PCE_STATUS_ENABLED) {
			if (ce->enabled_when_prepared) {
				clk_disable_unprepare(ce->clk);
				ce->status = PCE_STATUS_ACQUIRED;
			} else {
				clk_disable(ce->clk);
				ce->status = PCE_STATUS_PREPARED;
			}
		}
	}

	pm_clk_op_unlock(psd, &flags);

	return 0;
}
EXPORT_SYMBOL_GPL(pm_clk_suspend);

/**
 * pm_clk_resume - Enable clocks in a device's PM clock list.
 * @dev: Device to enable the clocks for.
 */
int pm_clk_resume(struct device *dev)
{
	struct pm_subsys_data *psd = dev_to_psd(dev);
	struct pm_clock_entry *ce;
	unsigned long flags;
	int ret;

	dev_dbg(dev, "%s()\n", __func__);

	if (!psd)
		return 0;

	ret = pm_clk_op_lock(psd, &flags, __func__);
	if (ret)
		return ret;

	list_for_each_entry(ce, &psd->clock_list, node)
		__pm_clk_enable(dev, ce);

	pm_clk_op_unlock(psd, &flags);

	return 0;
}
EXPORT_SYMBOL_GPL(pm_clk_resume);

/**
 * pm_clk_notify - Notify routine for device addition and removal.
 * @nb: Notifier block object this function is a member of.
 * @action: Operation being carried out by the caller.
 * @data: Device the routine is being run for.
 *
 * For this function to work, @nb must be a member of an object of type
 * struct pm_clk_notifier_block containing all of the requisite data.
 * Specifically, the pm_domain member of that object is copied to the device's
 * pm_domain field and its con_ids member is used to populate the device's list
 * of PM clocks, depending on @action.
 *
 * If the device's pm_domain field is already populated with a value different
 * from the one stored in the struct pm_clk_notifier_block object, the function
 * does nothing.
 */
static int pm_clk_notify(struct notifier_block *nb,
				 unsigned long action, void *data)
{
	struct pm_clk_notifier_block *clknb;
	struct device *dev = data;
	char **con_id;
	int error;

	dev_dbg(dev, "%s() %ld\n", __func__, action);

	clknb = container_of(nb, struct pm_clk_notifier_block, nb);

	switch (action) {
	case BUS_NOTIFY_ADD_DEVICE:
		if (dev->pm_domain)
			break;

		error = pm_clk_create(dev);
		if (error)
			break;

		dev_pm_domain_set(dev, clknb->pm_domain);
		if (clknb->con_ids[0]) {
			for (con_id = clknb->con_ids; *con_id; con_id++)
				pm_clk_add(dev, *con_id);
		} else {
			pm_clk_add(dev, NULL);
		}

		break;
	case BUS_NOTIFY_DEL_DEVICE:
		if (dev->pm_domain != clknb->pm_domain)
			break;

		dev_pm_domain_set(dev, NULL);
		pm_clk_destroy(dev);
		break;
	}

	return 0;
}

int pm_clk_runtime_suspend(struct device *dev)
{
	int ret;

	dev_dbg(dev, "%s\n", __func__);

	ret = pm_generic_runtime_suspend(dev);
	if (ret) {
		dev_err(dev, "failed to suspend device\n");
		return ret;
	}

	ret = pm_clk_suspend(dev);
	if (ret) {
		dev_err(dev, "failed to suspend clock\n");
		pm_generic_runtime_resume(dev);
		return ret;
	}

	return 0;
}
EXPORT_SYMBOL_GPL(pm_clk_runtime_suspend);

int pm_clk_runtime_resume(struct device *dev)
{
	int ret;

	dev_dbg(dev, "%s\n", __func__);

	ret = pm_clk_resume(dev);
	if (ret) {
		dev_err(dev, "failed to resume clock\n");
		return ret;
	}

	return pm_generic_runtime_resume(dev);
}
EXPORT_SYMBOL_GPL(pm_clk_runtime_resume);

#else /* !CONFIG_PM_CLK */

/**
 * enable_clock - Enable a device clock.
 * @dev: Device whose clock is to be enabled.
 * @con_id: Connection ID of the clock.
 */
static void enable_clock(struct device *dev, const char *con_id)
{
	struct clk *clk;

	clk = clk_get(dev, con_id);
	if (!IS_ERR(clk)) {
		clk_prepare_enable(clk);
		clk_put(clk);
		dev_info(dev, "Runtime PM disabled, clock forced on.\n");
	}
}

/**
 * disable_clock - Disable a device clock.
 * @dev: Device whose clock is to be disabled.
 * @con_id: Connection ID of the clock.
 */
static void disable_clock(struct device *dev, const char *con_id)
{
	struct clk *clk;

	clk = clk_get(dev, con_id);
	if (!IS_ERR(clk)) {
		clk_disable_unprepare(clk);
		clk_put(clk);
		dev_info(dev, "Runtime PM disabled, clock forced off.\n");
	}
}

/**
 * pm_clk_notify - Notify routine for device addition and removal.
 * @nb: Notifier block object this function is a member of.
 * @action: Operation being carried out by the caller.
 * @data: Device the routine is being run for.
 *
 * For this function to work, @nb must be a member of an object of type
 * struct pm_clk_notifier_block containing all of the requisite data.
 * Specifically, the con_ids member of that object is used to enable or disable
 * the device's clocks, depending on @action.
 */
static int pm_clk_notify(struct notifier_block *nb,
				 unsigned long action, void *data)
{
	struct pm_clk_notifier_block *clknb;
	struct device *dev = data;
	char **con_id;

	dev_dbg(dev, "%s() %ld\n", __func__, action);

	clknb = container_of(nb, struct pm_clk_notifier_block, nb);

	switch (action) {
	case BUS_NOTIFY_BIND_DRIVER:
		if (clknb->con_ids[0]) {
			for (con_id = clknb->con_ids; *con_id; con_id++)
				enable_clock(dev, *con_id);
		} else {
			enable_clock(dev, NULL);
		}
		break;
	case BUS_NOTIFY_DRIVER_NOT_BOUND:
	case BUS_NOTIFY_UNBOUND_DRIVER:
		if (clknb->con_ids[0]) {
			for (con_id = clknb->con_ids; *con_id; con_id++)
				disable_clock(dev, *con_id);
		} else {
			disable_clock(dev, NULL);
		}
		break;
	}

	return 0;
}

#endif /* !CONFIG_PM_CLK */

/**
 * pm_clk_add_notifier - Add bus type notifier for power management clocks.
 * @bus: Bus type to add the notifier to.
 * @clknb: Notifier to be added to the given bus type.
 *
 * The nb member of @clknb is not expected to be initialized and its
 * notifier_call member will be replaced with pm_clk_notify().  However,
 * the remaining members of @clknb should be populated prior to calling this
 * routine.
 */
void pm_clk_add_notifier(struct bus_type *bus,
				 struct pm_clk_notifier_block *clknb)
{
	if (!bus || !clknb)
		return;

	clknb->nb.notifier_call = pm_clk_notify;
	bus_register_notifier(bus, &clknb->nb);
}
EXPORT_SYMBOL_GPL(pm_clk_add_notifier);