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1/*
2 * Copyright (C) 2010-2011 Canonical Ltd <jeremy.kerr@canonical.com>
3 * Copyright (C) 2011-2012 Linaro Ltd <mturquette@linaro.org>
4 *
5 * This program is free software; you can redistribute it and/or modify
6 * it under the terms of the GNU General Public License version 2 as
7 * published by the Free Software Foundation.
8 *
9 * Standard functionality for the common clock API. See Documentation/clk.txt
10 */
11
12#include <linux/clk-private.h>
13#include <linux/module.h>
14#include <linux/mutex.h>
15#include <linux/spinlock.h>
16#include <linux/err.h>
17#include <linux/list.h>
18#include <linux/slab.h>
19
20static DEFINE_SPINLOCK(enable_lock);
21static DEFINE_MUTEX(prepare_lock);
22
23static HLIST_HEAD(clk_root_list);
24static HLIST_HEAD(clk_orphan_list);
25static LIST_HEAD(clk_notifier_list);
26
27/*** debugfs support ***/
28
29#ifdef CONFIG_COMMON_CLK_DEBUG
30#include <linux/debugfs.h>
31
32static struct dentry *rootdir;
33static struct dentry *orphandir;
34static int inited = 0;
35
36/* caller must hold prepare_lock */
37static int clk_debug_create_one(struct clk *clk, struct dentry *pdentry)
38{
39 struct dentry *d;
40 int ret = -ENOMEM;
41
42 if (!clk || !pdentry) {
43 ret = -EINVAL;
44 goto out;
45 }
46
47 d = debugfs_create_dir(clk->name, pdentry);
48 if (!d)
49 goto out;
50
51 clk->dentry = d;
52
53 d = debugfs_create_u32("clk_rate", S_IRUGO, clk->dentry,
54 (u32 *)&clk->rate);
55 if (!d)
56 goto err_out;
57
58 d = debugfs_create_x32("clk_flags", S_IRUGO, clk->dentry,
59 (u32 *)&clk->flags);
60 if (!d)
61 goto err_out;
62
63 d = debugfs_create_u32("clk_prepare_count", S_IRUGO, clk->dentry,
64 (u32 *)&clk->prepare_count);
65 if (!d)
66 goto err_out;
67
68 d = debugfs_create_u32("clk_enable_count", S_IRUGO, clk->dentry,
69 (u32 *)&clk->enable_count);
70 if (!d)
71 goto err_out;
72
73 d = debugfs_create_u32("clk_notifier_count", S_IRUGO, clk->dentry,
74 (u32 *)&clk->notifier_count);
75 if (!d)
76 goto err_out;
77
78 ret = 0;
79 goto out;
80
81err_out:
82 debugfs_remove(clk->dentry);
83out:
84 return ret;
85}
86
87/* caller must hold prepare_lock */
88static int clk_debug_create_subtree(struct clk *clk, struct dentry *pdentry)
89{
90 struct clk *child;
91 struct hlist_node *tmp;
92 int ret = -EINVAL;;
93
94 if (!clk || !pdentry)
95 goto out;
96
97 ret = clk_debug_create_one(clk, pdentry);
98
99 if (ret)
100 goto out;
101
102 hlist_for_each_entry(child, tmp, &clk->children, child_node)
103 clk_debug_create_subtree(child, clk->dentry);
104
105 ret = 0;
106out:
107 return ret;
108}
109
110/**
111 * clk_debug_register - add a clk node to the debugfs clk tree
112 * @clk: the clk being added to the debugfs clk tree
113 *
114 * Dynamically adds a clk to the debugfs clk tree if debugfs has been
115 * initialized. Otherwise it bails out early since the debugfs clk tree
116 * will be created lazily by clk_debug_init as part of a late_initcall.
117 *
118 * Caller must hold prepare_lock. Only clk_init calls this function (so
119 * far) so this is taken care.
120 */
121static int clk_debug_register(struct clk *clk)
122{
123 struct clk *parent;
124 struct dentry *pdentry;
125 int ret = 0;
126
127 if (!inited)
128 goto out;
129
130 parent = clk->parent;
131
132 /*
133 * Check to see if a clk is a root clk. Also check that it is
134 * safe to add this clk to debugfs
135 */
136 if (!parent)
137 if (clk->flags & CLK_IS_ROOT)
138 pdentry = rootdir;
139 else
140 pdentry = orphandir;
141 else
142 if (parent->dentry)
143 pdentry = parent->dentry;
144 else
145 goto out;
146
147 ret = clk_debug_create_subtree(clk, pdentry);
148
149out:
150 return ret;
151}
152
153/**
154 * clk_debug_init - lazily create the debugfs clk tree visualization
155 *
156 * clks are often initialized very early during boot before memory can
157 * be dynamically allocated and well before debugfs is setup.
158 * clk_debug_init walks the clk tree hierarchy while holding
159 * prepare_lock and creates the topology as part of a late_initcall,
160 * thus insuring that clks initialized very early will still be
161 * represented in the debugfs clk tree. This function should only be
162 * called once at boot-time, and all other clks added dynamically will
163 * be done so with clk_debug_register.
164 */
165static int __init clk_debug_init(void)
166{
167 struct clk *clk;
168 struct hlist_node *tmp;
169
170 rootdir = debugfs_create_dir("clk", NULL);
171
172 if (!rootdir)
173 return -ENOMEM;
174
175 orphandir = debugfs_create_dir("orphans", rootdir);
176
177 if (!orphandir)
178 return -ENOMEM;
179
180 mutex_lock(&prepare_lock);
181
182 hlist_for_each_entry(clk, tmp, &clk_root_list, child_node)
183 clk_debug_create_subtree(clk, rootdir);
184
185 hlist_for_each_entry(clk, tmp, &clk_orphan_list, child_node)
186 clk_debug_create_subtree(clk, orphandir);
187
188 inited = 1;
189
190 mutex_unlock(&prepare_lock);
191
192 return 0;
193}
194late_initcall(clk_debug_init);
195#else
196static inline int clk_debug_register(struct clk *clk) { return 0; }
197#endif
198
199/* caller must hold prepare_lock */
200static void clk_disable_unused_subtree(struct clk *clk)
201{
202 struct clk *child;
203 struct hlist_node *tmp;
204 unsigned long flags;
205
206 if (!clk)
207 goto out;
208
209 hlist_for_each_entry(child, tmp, &clk->children, child_node)
210 clk_disable_unused_subtree(child);
211
212 spin_lock_irqsave(&enable_lock, flags);
213
214 if (clk->enable_count)
215 goto unlock_out;
216
217 if (clk->flags & CLK_IGNORE_UNUSED)
218 goto unlock_out;
219
220 if (__clk_is_enabled(clk) && clk->ops->disable)
221 clk->ops->disable(clk->hw);
222
223unlock_out:
224 spin_unlock_irqrestore(&enable_lock, flags);
225
226out:
227 return;
228}
229
230static int clk_disable_unused(void)
231{
232 struct clk *clk;
233 struct hlist_node *tmp;
234
235 mutex_lock(&prepare_lock);
236
237 hlist_for_each_entry(clk, tmp, &clk_root_list, child_node)
238 clk_disable_unused_subtree(clk);
239
240 hlist_for_each_entry(clk, tmp, &clk_orphan_list, child_node)
241 clk_disable_unused_subtree(clk);
242
243 mutex_unlock(&prepare_lock);
244
245 return 0;
246}
247late_initcall(clk_disable_unused);
248
249/*** helper functions ***/
250
251inline const char *__clk_get_name(struct clk *clk)
252{
253 return !clk ? NULL : clk->name;
254}
255
256inline struct clk_hw *__clk_get_hw(struct clk *clk)
257{
258 return !clk ? NULL : clk->hw;
259}
260
261inline u8 __clk_get_num_parents(struct clk *clk)
262{
263 return !clk ? -EINVAL : clk->num_parents;
264}
265
266inline struct clk *__clk_get_parent(struct clk *clk)
267{
268 return !clk ? NULL : clk->parent;
269}
270
271inline int __clk_get_enable_count(struct clk *clk)
272{
273 return !clk ? -EINVAL : clk->enable_count;
274}
275
276inline int __clk_get_prepare_count(struct clk *clk)
277{
278 return !clk ? -EINVAL : clk->prepare_count;
279}
280
281unsigned long __clk_get_rate(struct clk *clk)
282{
283 unsigned long ret;
284
285 if (!clk) {
286 ret = 0;
287 goto out;
288 }
289
290 ret = clk->rate;
291
292 if (clk->flags & CLK_IS_ROOT)
293 goto out;
294
295 if (!clk->parent)
296 ret = 0;
297
298out:
299 return ret;
300}
301
302inline unsigned long __clk_get_flags(struct clk *clk)
303{
304 return !clk ? -EINVAL : clk->flags;
305}
306
307int __clk_is_enabled(struct clk *clk)
308{
309 int ret;
310
311 if (!clk)
312 return -EINVAL;
313
314 /*
315 * .is_enabled is only mandatory for clocks that gate
316 * fall back to software usage counter if .is_enabled is missing
317 */
318 if (!clk->ops->is_enabled) {
319 ret = clk->enable_count ? 1 : 0;
320 goto out;
321 }
322
323 ret = clk->ops->is_enabled(clk->hw);
324out:
325 return ret;
326}
327
328static struct clk *__clk_lookup_subtree(const char *name, struct clk *clk)
329{
330 struct clk *child;
331 struct clk *ret;
332 struct hlist_node *tmp;
333
334 if (!strcmp(clk->name, name))
335 return clk;
336
337 hlist_for_each_entry(child, tmp, &clk->children, child_node) {
338 ret = __clk_lookup_subtree(name, child);
339 if (ret)
340 return ret;
341 }
342
343 return NULL;
344}
345
346struct clk *__clk_lookup(const char *name)
347{
348 struct clk *root_clk;
349 struct clk *ret;
350 struct hlist_node *tmp;
351
352 if (!name)
353 return NULL;
354
355 /* search the 'proper' clk tree first */
356 hlist_for_each_entry(root_clk, tmp, &clk_root_list, child_node) {
357 ret = __clk_lookup_subtree(name, root_clk);
358 if (ret)
359 return ret;
360 }
361
362 /* if not found, then search the orphan tree */
363 hlist_for_each_entry(root_clk, tmp, &clk_orphan_list, child_node) {
364 ret = __clk_lookup_subtree(name, root_clk);
365 if (ret)
366 return ret;
367 }
368
369 return NULL;
370}
371
372/*** clk api ***/
373
374void __clk_unprepare(struct clk *clk)
375{
376 if (!clk)
377 return;
378
379 if (WARN_ON(clk->prepare_count == 0))
380 return;
381
382 if (--clk->prepare_count > 0)
383 return;
384
385 WARN_ON(clk->enable_count > 0);
386
387 if (clk->ops->unprepare)
388 clk->ops->unprepare(clk->hw);
389
390 __clk_unprepare(clk->parent);
391}
392
393/**
394 * clk_unprepare - undo preparation of a clock source
395 * @clk: the clk being unprepare
396 *
397 * clk_unprepare may sleep, which differentiates it from clk_disable. In a
398 * simple case, clk_unprepare can be used instead of clk_disable to gate a clk
399 * if the operation may sleep. One example is a clk which is accessed over
400 * I2c. In the complex case a clk gate operation may require a fast and a slow
401 * part. It is this reason that clk_unprepare and clk_disable are not mutually
402 * exclusive. In fact clk_disable must be called before clk_unprepare.
403 */
404void clk_unprepare(struct clk *clk)
405{
406 mutex_lock(&prepare_lock);
407 __clk_unprepare(clk);
408 mutex_unlock(&prepare_lock);
409}
410EXPORT_SYMBOL_GPL(clk_unprepare);
411
412int __clk_prepare(struct clk *clk)
413{
414 int ret = 0;
415
416 if (!clk)
417 return 0;
418
419 if (clk->prepare_count == 0) {
420 ret = __clk_prepare(clk->parent);
421 if (ret)
422 return ret;
423
424 if (clk->ops->prepare) {
425 ret = clk->ops->prepare(clk->hw);
426 if (ret) {
427 __clk_unprepare(clk->parent);
428 return ret;
429 }
430 }
431 }
432
433 clk->prepare_count++;
434
435 return 0;
436}
437
438/**
439 * clk_prepare - prepare a clock source
440 * @clk: the clk being prepared
441 *
442 * clk_prepare may sleep, which differentiates it from clk_enable. In a simple
443 * case, clk_prepare can be used instead of clk_enable to ungate a clk if the
444 * operation may sleep. One example is a clk which is accessed over I2c. In
445 * the complex case a clk ungate operation may require a fast and a slow part.
446 * It is this reason that clk_prepare and clk_enable are not mutually
447 * exclusive. In fact clk_prepare must be called before clk_enable.
448 * Returns 0 on success, -EERROR otherwise.
449 */
450int clk_prepare(struct clk *clk)
451{
452 int ret;
453
454 mutex_lock(&prepare_lock);
455 ret = __clk_prepare(clk);
456 mutex_unlock(&prepare_lock);
457
458 return ret;
459}
460EXPORT_SYMBOL_GPL(clk_prepare);
461
462static void __clk_disable(struct clk *clk)
463{
464 if (!clk)
465 return;
466
467 if (WARN_ON(clk->enable_count == 0))
468 return;
469
470 if (--clk->enable_count > 0)
471 return;
472
473 if (clk->ops->disable)
474 clk->ops->disable(clk->hw);
475
476 __clk_disable(clk->parent);
477}
478
479/**
480 * clk_disable - gate a clock
481 * @clk: the clk being gated
482 *
483 * clk_disable must not sleep, which differentiates it from clk_unprepare. In
484 * a simple case, clk_disable can be used instead of clk_unprepare to gate a
485 * clk if the operation is fast and will never sleep. One example is a
486 * SoC-internal clk which is controlled via simple register writes. In the
487 * complex case a clk gate operation may require a fast and a slow part. It is
488 * this reason that clk_unprepare and clk_disable are not mutually exclusive.
489 * In fact clk_disable must be called before clk_unprepare.
490 */
491void clk_disable(struct clk *clk)
492{
493 unsigned long flags;
494
495 spin_lock_irqsave(&enable_lock, flags);
496 __clk_disable(clk);
497 spin_unlock_irqrestore(&enable_lock, flags);
498}
499EXPORT_SYMBOL_GPL(clk_disable);
500
501static int __clk_enable(struct clk *clk)
502{
503 int ret = 0;
504
505 if (!clk)
506 return 0;
507
508 if (WARN_ON(clk->prepare_count == 0))
509 return -ESHUTDOWN;
510
511 if (clk->enable_count == 0) {
512 ret = __clk_enable(clk->parent);
513
514 if (ret)
515 return ret;
516
517 if (clk->ops->enable) {
518 ret = clk->ops->enable(clk->hw);
519 if (ret) {
520 __clk_disable(clk->parent);
521 return ret;
522 }
523 }
524 }
525
526 clk->enable_count++;
527 return 0;
528}
529
530/**
531 * clk_enable - ungate a clock
532 * @clk: the clk being ungated
533 *
534 * clk_enable must not sleep, which differentiates it from clk_prepare. In a
535 * simple case, clk_enable can be used instead of clk_prepare to ungate a clk
536 * if the operation will never sleep. One example is a SoC-internal clk which
537 * is controlled via simple register writes. In the complex case a clk ungate
538 * operation may require a fast and a slow part. It is this reason that
539 * clk_enable and clk_prepare are not mutually exclusive. In fact clk_prepare
540 * must be called before clk_enable. Returns 0 on success, -EERROR
541 * otherwise.
542 */
543int clk_enable(struct clk *clk)
544{
545 unsigned long flags;
546 int ret;
547
548 spin_lock_irqsave(&enable_lock, flags);
549 ret = __clk_enable(clk);
550 spin_unlock_irqrestore(&enable_lock, flags);
551
552 return ret;
553}
554EXPORT_SYMBOL_GPL(clk_enable);
555
556/**
557 * clk_get_rate - return the rate of clk
558 * @clk: the clk whose rate is being returned
559 *
560 * Simply returns the cached rate of the clk. Does not query the hardware. If
561 * clk is NULL then returns 0.
562 */
563unsigned long clk_get_rate(struct clk *clk)
564{
565 unsigned long rate;
566
567 mutex_lock(&prepare_lock);
568 rate = __clk_get_rate(clk);
569 mutex_unlock(&prepare_lock);
570
571 return rate;
572}
573EXPORT_SYMBOL_GPL(clk_get_rate);
574
575/**
576 * __clk_round_rate - round the given rate for a clk
577 * @clk: round the rate of this clock
578 *
579 * Caller must hold prepare_lock. Useful for clk_ops such as .set_rate
580 */
581unsigned long __clk_round_rate(struct clk *clk, unsigned long rate)
582{
583 unsigned long parent_rate = 0;
584
585 if (!clk)
586 return -EINVAL;
587
588 if (!clk->ops->round_rate) {
589 if (clk->flags & CLK_SET_RATE_PARENT)
590 return __clk_round_rate(clk->parent, rate);
591 else
592 return clk->rate;
593 }
594
595 if (clk->parent)
596 parent_rate = clk->parent->rate;
597
598 return clk->ops->round_rate(clk->hw, rate, &parent_rate);
599}
600
601/**
602 * clk_round_rate - round the given rate for a clk
603 * @clk: the clk for which we are rounding a rate
604 * @rate: the rate which is to be rounded
605 *
606 * Takes in a rate as input and rounds it to a rate that the clk can actually
607 * use which is then returned. If clk doesn't support round_rate operation
608 * then the parent rate is returned.
609 */
610long clk_round_rate(struct clk *clk, unsigned long rate)
611{
612 unsigned long ret;
613
614 mutex_lock(&prepare_lock);
615 ret = __clk_round_rate(clk, rate);
616 mutex_unlock(&prepare_lock);
617
618 return ret;
619}
620EXPORT_SYMBOL_GPL(clk_round_rate);
621
622/**
623 * __clk_notify - call clk notifier chain
624 * @clk: struct clk * that is changing rate
625 * @msg: clk notifier type (see include/linux/clk.h)
626 * @old_rate: old clk rate
627 * @new_rate: new clk rate
628 *
629 * Triggers a notifier call chain on the clk rate-change notification
630 * for 'clk'. Passes a pointer to the struct clk and the previous
631 * and current rates to the notifier callback. Intended to be called by
632 * internal clock code only. Returns NOTIFY_DONE from the last driver
633 * called if all went well, or NOTIFY_STOP or NOTIFY_BAD immediately if
634 * a driver returns that.
635 */
636static int __clk_notify(struct clk *clk, unsigned long msg,
637 unsigned long old_rate, unsigned long new_rate)
638{
639 struct clk_notifier *cn;
640 struct clk_notifier_data cnd;
641 int ret = NOTIFY_DONE;
642
643 cnd.clk = clk;
644 cnd.old_rate = old_rate;
645 cnd.new_rate = new_rate;
646
647 list_for_each_entry(cn, &clk_notifier_list, node) {
648 if (cn->clk == clk) {
649 ret = srcu_notifier_call_chain(&cn->notifier_head, msg,
650 &cnd);
651 break;
652 }
653 }
654
655 return ret;
656}
657
658/**
659 * __clk_recalc_rates
660 * @clk: first clk in the subtree
661 * @msg: notification type (see include/linux/clk.h)
662 *
663 * Walks the subtree of clks starting with clk and recalculates rates as it
664 * goes. Note that if a clk does not implement the .recalc_rate callback then
665 * it is assumed that the clock will take on the rate of it's parent.
666 *
667 * clk_recalc_rates also propagates the POST_RATE_CHANGE notification,
668 * if necessary.
669 *
670 * Caller must hold prepare_lock.
671 */
672static void __clk_recalc_rates(struct clk *clk, unsigned long msg)
673{
674 unsigned long old_rate;
675 unsigned long parent_rate = 0;
676 struct hlist_node *tmp;
677 struct clk *child;
678
679 old_rate = clk->rate;
680
681 if (clk->parent)
682 parent_rate = clk->parent->rate;
683
684 if (clk->ops->recalc_rate)
685 clk->rate = clk->ops->recalc_rate(clk->hw, parent_rate);
686 else
687 clk->rate = parent_rate;
688
689 /*
690 * ignore NOTIFY_STOP and NOTIFY_BAD return values for POST_RATE_CHANGE
691 * & ABORT_RATE_CHANGE notifiers
692 */
693 if (clk->notifier_count && msg)
694 __clk_notify(clk, msg, old_rate, clk->rate);
695
696 hlist_for_each_entry(child, tmp, &clk->children, child_node)
697 __clk_recalc_rates(child, msg);
698}
699
700/**
701 * __clk_speculate_rates
702 * @clk: first clk in the subtree
703 * @parent_rate: the "future" rate of clk's parent
704 *
705 * Walks the subtree of clks starting with clk, speculating rates as it
706 * goes and firing off PRE_RATE_CHANGE notifications as necessary.
707 *
708 * Unlike clk_recalc_rates, clk_speculate_rates exists only for sending
709 * pre-rate change notifications and returns early if no clks in the
710 * subtree have subscribed to the notifications. Note that if a clk does not
711 * implement the .recalc_rate callback then it is assumed that the clock will
712 * take on the rate of it's parent.
713 *
714 * Caller must hold prepare_lock.
715 */
716static int __clk_speculate_rates(struct clk *clk, unsigned long parent_rate)
717{
718 struct hlist_node *tmp;
719 struct clk *child;
720 unsigned long new_rate;
721 int ret = NOTIFY_DONE;
722
723 if (clk->ops->recalc_rate)
724 new_rate = clk->ops->recalc_rate(clk->hw, parent_rate);
725 else
726 new_rate = parent_rate;
727
728 /* abort the rate change if a driver returns NOTIFY_BAD */
729 if (clk->notifier_count)
730 ret = __clk_notify(clk, PRE_RATE_CHANGE, clk->rate, new_rate);
731
732 if (ret == NOTIFY_BAD)
733 goto out;
734
735 hlist_for_each_entry(child, tmp, &clk->children, child_node) {
736 ret = __clk_speculate_rates(child, new_rate);
737 if (ret == NOTIFY_BAD)
738 break;
739 }
740
741out:
742 return ret;
743}
744
745static void clk_calc_subtree(struct clk *clk, unsigned long new_rate)
746{
747 struct clk *child;
748 struct hlist_node *tmp;
749
750 clk->new_rate = new_rate;
751
752 hlist_for_each_entry(child, tmp, &clk->children, child_node) {
753 if (child->ops->recalc_rate)
754 child->new_rate = child->ops->recalc_rate(child->hw, new_rate);
755 else
756 child->new_rate = new_rate;
757 clk_calc_subtree(child, child->new_rate);
758 }
759}
760
761/*
762 * calculate the new rates returning the topmost clock that has to be
763 * changed.
764 */
765static struct clk *clk_calc_new_rates(struct clk *clk, unsigned long rate)
766{
767 struct clk *top = clk;
768 unsigned long best_parent_rate = 0;
769 unsigned long new_rate;
770
771 /* sanity */
772 if (IS_ERR_OR_NULL(clk))
773 return NULL;
774
775 /* save parent rate, if it exists */
776 if (clk->parent)
777 best_parent_rate = clk->parent->rate;
778
779 /* never propagate up to the parent */
780 if (!(clk->flags & CLK_SET_RATE_PARENT)) {
781 if (!clk->ops->round_rate) {
782 clk->new_rate = clk->rate;
783 return NULL;
784 }
785 new_rate = clk->ops->round_rate(clk->hw, rate, &best_parent_rate);
786 goto out;
787 }
788
789 /* need clk->parent from here on out */
790 if (!clk->parent) {
791 pr_debug("%s: %s has NULL parent\n", __func__, clk->name);
792 return NULL;
793 }
794
795 if (!clk->ops->round_rate) {
796 top = clk_calc_new_rates(clk->parent, rate);
797 new_rate = clk->parent->new_rate;
798
799 goto out;
800 }
801
802 new_rate = clk->ops->round_rate(clk->hw, rate, &best_parent_rate);
803
804 if (best_parent_rate != clk->parent->rate) {
805 top = clk_calc_new_rates(clk->parent, best_parent_rate);
806
807 goto out;
808 }
809
810out:
811 clk_calc_subtree(clk, new_rate);
812
813 return top;
814}
815
816/*
817 * Notify about rate changes in a subtree. Always walk down the whole tree
818 * so that in case of an error we can walk down the whole tree again and
819 * abort the change.
820 */
821static struct clk *clk_propagate_rate_change(struct clk *clk, unsigned long event)
822{
823 struct hlist_node *tmp;
824 struct clk *child, *fail_clk = NULL;
825 int ret = NOTIFY_DONE;
826
827 if (clk->rate == clk->new_rate)
828 return 0;
829
830 if (clk->notifier_count) {
831 ret = __clk_notify(clk, event, clk->rate, clk->new_rate);
832 if (ret == NOTIFY_BAD)
833 fail_clk = clk;
834 }
835
836 hlist_for_each_entry(child, tmp, &clk->children, child_node) {
837 clk = clk_propagate_rate_change(child, event);
838 if (clk)
839 fail_clk = clk;
840 }
841
842 return fail_clk;
843}
844
845/*
846 * walk down a subtree and set the new rates notifying the rate
847 * change on the way
848 */
849static void clk_change_rate(struct clk *clk)
850{
851 struct clk *child;
852 unsigned long old_rate;
853 unsigned long best_parent_rate = 0;
854 struct hlist_node *tmp;
855
856 old_rate = clk->rate;
857
858 if (clk->parent)
859 best_parent_rate = clk->parent->rate;
860
861 if (clk->ops->set_rate)
862 clk->ops->set_rate(clk->hw, clk->new_rate, best_parent_rate);
863
864 if (clk->ops->recalc_rate)
865 clk->rate = clk->ops->recalc_rate(clk->hw, best_parent_rate);
866 else
867 clk->rate = best_parent_rate;
868
869 if (clk->notifier_count && old_rate != clk->rate)
870 __clk_notify(clk, POST_RATE_CHANGE, old_rate, clk->rate);
871
872 hlist_for_each_entry(child, tmp, &clk->children, child_node)
873 clk_change_rate(child);
874}
875
876/**
877 * clk_set_rate - specify a new rate for clk
878 * @clk: the clk whose rate is being changed
879 * @rate: the new rate for clk
880 *
881 * In the simplest case clk_set_rate will only adjust the rate of clk.
882 *
883 * Setting the CLK_SET_RATE_PARENT flag allows the rate change operation to
884 * propagate up to clk's parent; whether or not this happens depends on the
885 * outcome of clk's .round_rate implementation. If *parent_rate is unchanged
886 * after calling .round_rate then upstream parent propagation is ignored. If
887 * *parent_rate comes back with a new rate for clk's parent then we propagate
888 * up to clk's parent and set it's rate. Upward propagation will continue
889 * until either a clk does not support the CLK_SET_RATE_PARENT flag or
890 * .round_rate stops requesting changes to clk's parent_rate.
891 *
892 * Rate changes are accomplished via tree traversal that also recalculates the
893 * rates for the clocks and fires off POST_RATE_CHANGE notifiers.
894 *
895 * Returns 0 on success, -EERROR otherwise.
896 */
897int clk_set_rate(struct clk *clk, unsigned long rate)
898{
899 struct clk *top, *fail_clk;
900 int ret = 0;
901
902 /* prevent racing with updates to the clock topology */
903 mutex_lock(&prepare_lock);
904
905 /* bail early if nothing to do */
906 if (rate == clk->rate)
907 goto out;
908
909 if ((clk->flags & CLK_SET_RATE_GATE) && clk->prepare_count) {
910 ret = -EBUSY;
911 goto out;
912 }
913
914 /* calculate new rates and get the topmost changed clock */
915 top = clk_calc_new_rates(clk, rate);
916 if (!top) {
917 ret = -EINVAL;
918 goto out;
919 }
920
921 /* notify that we are about to change rates */
922 fail_clk = clk_propagate_rate_change(top, PRE_RATE_CHANGE);
923 if (fail_clk) {
924 pr_warn("%s: failed to set %s rate\n", __func__,
925 fail_clk->name);
926 clk_propagate_rate_change(top, ABORT_RATE_CHANGE);
927 ret = -EBUSY;
928 goto out;
929 }
930
931 /* change the rates */
932 clk_change_rate(top);
933
934 mutex_unlock(&prepare_lock);
935
936 return 0;
937out:
938 mutex_unlock(&prepare_lock);
939
940 return ret;
941}
942EXPORT_SYMBOL_GPL(clk_set_rate);
943
944/**
945 * clk_get_parent - return the parent of a clk
946 * @clk: the clk whose parent gets returned
947 *
948 * Simply returns clk->parent. Returns NULL if clk is NULL.
949 */
950struct clk *clk_get_parent(struct clk *clk)
951{
952 struct clk *parent;
953
954 mutex_lock(&prepare_lock);
955 parent = __clk_get_parent(clk);
956 mutex_unlock(&prepare_lock);
957
958 return parent;
959}
960EXPORT_SYMBOL_GPL(clk_get_parent);
961
962/*
963 * .get_parent is mandatory for clocks with multiple possible parents. It is
964 * optional for single-parent clocks. Always call .get_parent if it is
965 * available and WARN if it is missing for multi-parent clocks.
966 *
967 * For single-parent clocks without .get_parent, first check to see if the
968 * .parents array exists, and if so use it to avoid an expensive tree
969 * traversal. If .parents does not exist then walk the tree with __clk_lookup.
970 */
971static struct clk *__clk_init_parent(struct clk *clk)
972{
973 struct clk *ret = NULL;
974 u8 index;
975
976 /* handle the trivial cases */
977
978 if (!clk->num_parents)
979 goto out;
980
981 if (clk->num_parents == 1) {
982 if (IS_ERR_OR_NULL(clk->parent))
983 ret = clk->parent = __clk_lookup(clk->parent_names[0]);
984 ret = clk->parent;
985 goto out;
986 }
987
988 if (!clk->ops->get_parent) {
989 WARN(!clk->ops->get_parent,
990 "%s: multi-parent clocks must implement .get_parent\n",
991 __func__);
992 goto out;
993 };
994
995 /*
996 * Do our best to cache parent clocks in clk->parents. This prevents
997 * unnecessary and expensive calls to __clk_lookup. We don't set
998 * clk->parent here; that is done by the calling function
999 */
1000
1001 index = clk->ops->get_parent(clk->hw);
1002
1003 if (!clk->parents)
1004 clk->parents =
1005 kzalloc((sizeof(struct clk*) * clk->num_parents),
1006 GFP_KERNEL);
1007
1008 if (!clk->parents)
1009 ret = __clk_lookup(clk->parent_names[index]);
1010 else if (!clk->parents[index])
1011 ret = clk->parents[index] =
1012 __clk_lookup(clk->parent_names[index]);
1013 else
1014 ret = clk->parents[index];
1015
1016out:
1017 return ret;
1018}
1019
1020void __clk_reparent(struct clk *clk, struct clk *new_parent)
1021{
1022#ifdef CONFIG_COMMON_CLK_DEBUG
1023 struct dentry *d;
1024 struct dentry *new_parent_d;
1025#endif
1026
1027 if (!clk || !new_parent)
1028 return;
1029
1030 hlist_del(&clk->child_node);
1031
1032 if (new_parent)
1033 hlist_add_head(&clk->child_node, &new_parent->children);
1034 else
1035 hlist_add_head(&clk->child_node, &clk_orphan_list);
1036
1037#ifdef CONFIG_COMMON_CLK_DEBUG
1038 if (!inited)
1039 goto out;
1040
1041 if (new_parent)
1042 new_parent_d = new_parent->dentry;
1043 else
1044 new_parent_d = orphandir;
1045
1046 d = debugfs_rename(clk->dentry->d_parent, clk->dentry,
1047 new_parent_d, clk->name);
1048 if (d)
1049 clk->dentry = d;
1050 else
1051 pr_debug("%s: failed to rename debugfs entry for %s\n",
1052 __func__, clk->name);
1053out:
1054#endif
1055
1056 clk->parent = new_parent;
1057
1058 __clk_recalc_rates(clk, POST_RATE_CHANGE);
1059}
1060
1061static int __clk_set_parent(struct clk *clk, struct clk *parent)
1062{
1063 struct clk *old_parent;
1064 unsigned long flags;
1065 int ret = -EINVAL;
1066 u8 i;
1067
1068 old_parent = clk->parent;
1069
1070 if (!clk->parents)
1071 clk->parents = kzalloc((sizeof(struct clk*) * clk->num_parents),
1072 GFP_KERNEL);
1073
1074 /*
1075 * find index of new parent clock using cached parent ptrs,
1076 * or if not yet cached, use string name comparison and cache
1077 * them now to avoid future calls to __clk_lookup.
1078 */
1079 for (i = 0; i < clk->num_parents; i++) {
1080 if (clk->parents && clk->parents[i] == parent)
1081 break;
1082 else if (!strcmp(clk->parent_names[i], parent->name)) {
1083 if (clk->parents)
1084 clk->parents[i] = __clk_lookup(parent->name);
1085 break;
1086 }
1087 }
1088
1089 if (i == clk->num_parents) {
1090 pr_debug("%s: clock %s is not a possible parent of clock %s\n",
1091 __func__, parent->name, clk->name);
1092 goto out;
1093 }
1094
1095 /* migrate prepare and enable */
1096 if (clk->prepare_count)
1097 __clk_prepare(parent);
1098
1099 /* FIXME replace with clk_is_enabled(clk) someday */
1100 spin_lock_irqsave(&enable_lock, flags);
1101 if (clk->enable_count)
1102 __clk_enable(parent);
1103 spin_unlock_irqrestore(&enable_lock, flags);
1104
1105 /* change clock input source */
1106 ret = clk->ops->set_parent(clk->hw, i);
1107
1108 /* clean up old prepare and enable */
1109 spin_lock_irqsave(&enable_lock, flags);
1110 if (clk->enable_count)
1111 __clk_disable(old_parent);
1112 spin_unlock_irqrestore(&enable_lock, flags);
1113
1114 if (clk->prepare_count)
1115 __clk_unprepare(old_parent);
1116
1117out:
1118 return ret;
1119}
1120
1121/**
1122 * clk_set_parent - switch the parent of a mux clk
1123 * @clk: the mux clk whose input we are switching
1124 * @parent: the new input to clk
1125 *
1126 * Re-parent clk to use parent as it's new input source. If clk has the
1127 * CLK_SET_PARENT_GATE flag set then clk must be gated for this
1128 * operation to succeed. After successfully changing clk's parent
1129 * clk_set_parent will update the clk topology, sysfs topology and
1130 * propagate rate recalculation via __clk_recalc_rates. Returns 0 on
1131 * success, -EERROR otherwise.
1132 */
1133int clk_set_parent(struct clk *clk, struct clk *parent)
1134{
1135 int ret = 0;
1136
1137 if (!clk || !clk->ops)
1138 return -EINVAL;
1139
1140 if (!clk->ops->set_parent)
1141 return -ENOSYS;
1142
1143 /* prevent racing with updates to the clock topology */
1144 mutex_lock(&prepare_lock);
1145
1146 if (clk->parent == parent)
1147 goto out;
1148
1149 /* propagate PRE_RATE_CHANGE notifications */
1150 if (clk->notifier_count)
1151 ret = __clk_speculate_rates(clk, parent->rate);
1152
1153 /* abort if a driver objects */
1154 if (ret == NOTIFY_STOP)
1155 goto out;
1156
1157 /* only re-parent if the clock is not in use */
1158 if ((clk->flags & CLK_SET_PARENT_GATE) && clk->prepare_count)
1159 ret = -EBUSY;
1160 else
1161 ret = __clk_set_parent(clk, parent);
1162
1163 /* propagate ABORT_RATE_CHANGE if .set_parent failed */
1164 if (ret) {
1165 __clk_recalc_rates(clk, ABORT_RATE_CHANGE);
1166 goto out;
1167 }
1168
1169 /* propagate rate recalculation downstream */
1170 __clk_reparent(clk, parent);
1171
1172out:
1173 mutex_unlock(&prepare_lock);
1174
1175 return ret;
1176}
1177EXPORT_SYMBOL_GPL(clk_set_parent);
1178
1179/**
1180 * __clk_init - initialize the data structures in a struct clk
1181 * @dev: device initializing this clk, placeholder for now
1182 * @clk: clk being initialized
1183 *
1184 * Initializes the lists in struct clk, queries the hardware for the
1185 * parent and rate and sets them both.
1186 */
1187int __clk_init(struct device *dev, struct clk *clk)
1188{
1189 int i, ret = 0;
1190 struct clk *orphan;
1191 struct hlist_node *tmp, *tmp2;
1192
1193 if (!clk)
1194 return -EINVAL;
1195
1196 mutex_lock(&prepare_lock);
1197
1198 /* check to see if a clock with this name is already registered */
1199 if (__clk_lookup(clk->name)) {
1200 pr_debug("%s: clk %s already initialized\n",
1201 __func__, clk->name);
1202 ret = -EEXIST;
1203 goto out;
1204 }
1205
1206 /* check that clk_ops are sane. See Documentation/clk.txt */
1207 if (clk->ops->set_rate &&
1208 !(clk->ops->round_rate && clk->ops->recalc_rate)) {
1209 pr_warning("%s: %s must implement .round_rate & .recalc_rate\n",
1210 __func__, clk->name);
1211 ret = -EINVAL;
1212 goto out;
1213 }
1214
1215 if (clk->ops->set_parent && !clk->ops->get_parent) {
1216 pr_warning("%s: %s must implement .get_parent & .set_parent\n",
1217 __func__, clk->name);
1218 ret = -EINVAL;
1219 goto out;
1220 }
1221
1222 /* throw a WARN if any entries in parent_names are NULL */
1223 for (i = 0; i < clk->num_parents; i++)
1224 WARN(!clk->parent_names[i],
1225 "%s: invalid NULL in %s's .parent_names\n",
1226 __func__, clk->name);
1227
1228 /*
1229 * Allocate an array of struct clk *'s to avoid unnecessary string
1230 * look-ups of clk's possible parents. This can fail for clocks passed
1231 * in to clk_init during early boot; thus any access to clk->parents[]
1232 * must always check for a NULL pointer and try to populate it if
1233 * necessary.
1234 *
1235 * If clk->parents is not NULL we skip this entire block. This allows
1236 * for clock drivers to statically initialize clk->parents.
1237 */
1238 if (clk->num_parents && !clk->parents) {
1239 clk->parents = kmalloc((sizeof(struct clk*) * clk->num_parents),
1240 GFP_KERNEL);
1241 /*
1242 * __clk_lookup returns NULL for parents that have not been
1243 * clk_init'd; thus any access to clk->parents[] must check
1244 * for a NULL pointer. We can always perform lazy lookups for
1245 * missing parents later on.
1246 */
1247 if (clk->parents)
1248 for (i = 0; i < clk->num_parents; i++)
1249 clk->parents[i] =
1250 __clk_lookup(clk->parent_names[i]);
1251 }
1252
1253 clk->parent = __clk_init_parent(clk);
1254
1255 /*
1256 * Populate clk->parent if parent has already been __clk_init'd. If
1257 * parent has not yet been __clk_init'd then place clk in the orphan
1258 * list. If clk has set the CLK_IS_ROOT flag then place it in the root
1259 * clk list.
1260 *
1261 * Every time a new clk is clk_init'd then we walk the list of orphan
1262 * clocks and re-parent any that are children of the clock currently
1263 * being clk_init'd.
1264 */
1265 if (clk->parent)
1266 hlist_add_head(&clk->child_node,
1267 &clk->parent->children);
1268 else if (clk->flags & CLK_IS_ROOT)
1269 hlist_add_head(&clk->child_node, &clk_root_list);
1270 else
1271 hlist_add_head(&clk->child_node, &clk_orphan_list);
1272
1273 /*
1274 * Set clk's rate. The preferred method is to use .recalc_rate. For
1275 * simple clocks and lazy developers the default fallback is to use the
1276 * parent's rate. If a clock doesn't have a parent (or is orphaned)
1277 * then rate is set to zero.
1278 */
1279 if (clk->ops->recalc_rate)
1280 clk->rate = clk->ops->recalc_rate(clk->hw,
1281 __clk_get_rate(clk->parent));
1282 else if (clk->parent)
1283 clk->rate = clk->parent->rate;
1284 else
1285 clk->rate = 0;
1286
1287 /*
1288 * walk the list of orphan clocks and reparent any that are children of
1289 * this clock
1290 */
1291 hlist_for_each_entry_safe(orphan, tmp, tmp2, &clk_orphan_list, child_node)
1292 for (i = 0; i < orphan->num_parents; i++)
1293 if (!strcmp(clk->name, orphan->parent_names[i])) {
1294 __clk_reparent(orphan, clk);
1295 break;
1296 }
1297
1298 /*
1299 * optional platform-specific magic
1300 *
1301 * The .init callback is not used by any of the basic clock types, but
1302 * exists for weird hardware that must perform initialization magic.
1303 * Please consider other ways of solving initialization problems before
1304 * using this callback, as it's use is discouraged.
1305 */
1306 if (clk->ops->init)
1307 clk->ops->init(clk->hw);
1308
1309 clk_debug_register(clk);
1310
1311out:
1312 mutex_unlock(&prepare_lock);
1313
1314 return ret;
1315}
1316
1317/**
1318 * __clk_register - register a clock and return a cookie.
1319 *
1320 * Same as clk_register, except that the .clk field inside hw shall point to a
1321 * preallocated (generally statically allocated) struct clk. None of the fields
1322 * of the struct clk need to be initialized.
1323 *
1324 * The data pointed to by .init and .clk field shall NOT be marked as init
1325 * data.
1326 *
1327 * __clk_register is only exposed via clk-private.h and is intended for use with
1328 * very large numbers of clocks that need to be statically initialized. It is
1329 * a layering violation to include clk-private.h from any code which implements
1330 * a clock's .ops; as such any statically initialized clock data MUST be in a
1331 * separate C file from the logic that implements it's operations. Returns 0
1332 * on success, otherwise an error code.
1333 */
1334struct clk *__clk_register(struct device *dev, struct clk_hw *hw)
1335{
1336 int ret;
1337 struct clk *clk;
1338
1339 clk = hw->clk;
1340 clk->name = hw->init->name;
1341 clk->ops = hw->init->ops;
1342 clk->hw = hw;
1343 clk->flags = hw->init->flags;
1344 clk->parent_names = hw->init->parent_names;
1345 clk->num_parents = hw->init->num_parents;
1346
1347 ret = __clk_init(dev, clk);
1348 if (ret)
1349 return ERR_PTR(ret);
1350
1351 return clk;
1352}
1353EXPORT_SYMBOL_GPL(__clk_register);
1354
1355/**
1356 * clk_register - allocate a new clock, register it and return an opaque cookie
1357 * @dev: device that is registering this clock
1358 * @hw: link to hardware-specific clock data
1359 *
1360 * clk_register is the primary interface for populating the clock tree with new
1361 * clock nodes. It returns a pointer to the newly allocated struct clk which
1362 * cannot be dereferenced by driver code but may be used in conjuction with the
1363 * rest of the clock API. In the event of an error clk_register will return an
1364 * error code; drivers must test for an error code after calling clk_register.
1365 */
1366struct clk *clk_register(struct device *dev, struct clk_hw *hw)
1367{
1368 int i, ret;
1369 struct clk *clk;
1370
1371 clk = kzalloc(sizeof(*clk), GFP_KERNEL);
1372 if (!clk) {
1373 pr_err("%s: could not allocate clk\n", __func__);
1374 ret = -ENOMEM;
1375 goto fail_out;
1376 }
1377
1378 clk->name = kstrdup(hw->init->name, GFP_KERNEL);
1379 if (!clk->name) {
1380 pr_err("%s: could not allocate clk->name\n", __func__);
1381 ret = -ENOMEM;
1382 goto fail_name;
1383 }
1384 clk->ops = hw->init->ops;
1385 clk->hw = hw;
1386 clk->flags = hw->init->flags;
1387 clk->num_parents = hw->init->num_parents;
1388 hw->clk = clk;
1389
1390 /* allocate local copy in case parent_names is __initdata */
1391 clk->parent_names = kzalloc((sizeof(char*) * clk->num_parents),
1392 GFP_KERNEL);
1393
1394 if (!clk->parent_names) {
1395 pr_err("%s: could not allocate clk->parent_names\n", __func__);
1396 ret = -ENOMEM;
1397 goto fail_parent_names;
1398 }
1399
1400
1401 /* copy each string name in case parent_names is __initdata */
1402 for (i = 0; i < clk->num_parents; i++) {
1403 clk->parent_names[i] = kstrdup(hw->init->parent_names[i],
1404 GFP_KERNEL);
1405 if (!clk->parent_names[i]) {
1406 pr_err("%s: could not copy parent_names\n", __func__);
1407 ret = -ENOMEM;
1408 goto fail_parent_names_copy;
1409 }
1410 }
1411
1412 ret = __clk_init(dev, clk);
1413 if (!ret)
1414 return clk;
1415
1416fail_parent_names_copy:
1417 while (--i >= 0)
1418 kfree(clk->parent_names[i]);
1419 kfree(clk->parent_names);
1420fail_parent_names:
1421 kfree(clk->name);
1422fail_name:
1423 kfree(clk);
1424fail_out:
1425 return ERR_PTR(ret);
1426}
1427EXPORT_SYMBOL_GPL(clk_register);
1428
1429/**
1430 * clk_unregister - unregister a currently registered clock
1431 * @clk: clock to unregister
1432 *
1433 * Currently unimplemented.
1434 */
1435void clk_unregister(struct clk *clk) {}
1436EXPORT_SYMBOL_GPL(clk_unregister);
1437
1438/*** clk rate change notifiers ***/
1439
1440/**
1441 * clk_notifier_register - add a clk rate change notifier
1442 * @clk: struct clk * to watch
1443 * @nb: struct notifier_block * with callback info
1444 *
1445 * Request notification when clk's rate changes. This uses an SRCU
1446 * notifier because we want it to block and notifier unregistrations are
1447 * uncommon. The callbacks associated with the notifier must not
1448 * re-enter into the clk framework by calling any top-level clk APIs;
1449 * this will cause a nested prepare_lock mutex.
1450 *
1451 * Pre-change notifier callbacks will be passed the current, pre-change
1452 * rate of the clk via struct clk_notifier_data.old_rate. The new,
1453 * post-change rate of the clk is passed via struct
1454 * clk_notifier_data.new_rate.
1455 *
1456 * Post-change notifiers will pass the now-current, post-change rate of
1457 * the clk in both struct clk_notifier_data.old_rate and struct
1458 * clk_notifier_data.new_rate.
1459 *
1460 * Abort-change notifiers are effectively the opposite of pre-change
1461 * notifiers: the original pre-change clk rate is passed in via struct
1462 * clk_notifier_data.new_rate and the failed post-change rate is passed
1463 * in via struct clk_notifier_data.old_rate.
1464 *
1465 * clk_notifier_register() must be called from non-atomic context.
1466 * Returns -EINVAL if called with null arguments, -ENOMEM upon
1467 * allocation failure; otherwise, passes along the return value of
1468 * srcu_notifier_chain_register().
1469 */
1470int clk_notifier_register(struct clk *clk, struct notifier_block *nb)
1471{
1472 struct clk_notifier *cn;
1473 int ret = -ENOMEM;
1474
1475 if (!clk || !nb)
1476 return -EINVAL;
1477
1478 mutex_lock(&prepare_lock);
1479
1480 /* search the list of notifiers for this clk */
1481 list_for_each_entry(cn, &clk_notifier_list, node)
1482 if (cn->clk == clk)
1483 break;
1484
1485 /* if clk wasn't in the notifier list, allocate new clk_notifier */
1486 if (cn->clk != clk) {
1487 cn = kzalloc(sizeof(struct clk_notifier), GFP_KERNEL);
1488 if (!cn)
1489 goto out;
1490
1491 cn->clk = clk;
1492 srcu_init_notifier_head(&cn->notifier_head);
1493
1494 list_add(&cn->node, &clk_notifier_list);
1495 }
1496
1497 ret = srcu_notifier_chain_register(&cn->notifier_head, nb);
1498
1499 clk->notifier_count++;
1500
1501out:
1502 mutex_unlock(&prepare_lock);
1503
1504 return ret;
1505}
1506EXPORT_SYMBOL_GPL(clk_notifier_register);
1507
1508/**
1509 * clk_notifier_unregister - remove a clk rate change notifier
1510 * @clk: struct clk *
1511 * @nb: struct notifier_block * with callback info
1512 *
1513 * Request no further notification for changes to 'clk' and frees memory
1514 * allocated in clk_notifier_register.
1515 *
1516 * Returns -EINVAL if called with null arguments; otherwise, passes
1517 * along the return value of srcu_notifier_chain_unregister().
1518 */
1519int clk_notifier_unregister(struct clk *clk, struct notifier_block *nb)
1520{
1521 struct clk_notifier *cn = NULL;
1522 int ret = -EINVAL;
1523
1524 if (!clk || !nb)
1525 return -EINVAL;
1526
1527 mutex_lock(&prepare_lock);
1528
1529 list_for_each_entry(cn, &clk_notifier_list, node)
1530 if (cn->clk == clk)
1531 break;
1532
1533 if (cn->clk == clk) {
1534 ret = srcu_notifier_chain_unregister(&cn->notifier_head, nb);
1535
1536 clk->notifier_count--;
1537
1538 /* XXX the notifier code should handle this better */
1539 if (!cn->notifier_head.head) {
1540 srcu_cleanup_notifier_head(&cn->notifier_head);
1541 kfree(cn);
1542 }
1543
1544 } else {
1545 ret = -ENOENT;
1546 }
1547
1548 mutex_unlock(&prepare_lock);
1549
1550 return ret;
1551}
1552EXPORT_SYMBOL_GPL(clk_notifier_unregister);