clk.c 37.3 KB
Newer Older
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
/*
 * Copyright (C) 2010-2011 Canonical Ltd <jeremy.kerr@canonical.com>
 * Copyright (C) 2011-2012 Linaro Ltd <mturquette@linaro.org>
 *
 * 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.
 *
 * Standard functionality for the common clock API.  See Documentation/clk.txt
 */

#include <linux/clk-private.h>
#include <linux/module.h>
#include <linux/mutex.h>
#include <linux/spinlock.h>
#include <linux/err.h>
#include <linux/list.h>
#include <linux/slab.h>

static DEFINE_SPINLOCK(enable_lock);
static DEFINE_MUTEX(prepare_lock);

static HLIST_HEAD(clk_root_list);
static HLIST_HEAD(clk_orphan_list);
static LIST_HEAD(clk_notifier_list);

/***        debugfs support        ***/

#ifdef CONFIG_COMMON_CLK_DEBUG
#include <linux/debugfs.h>

static struct dentry *rootdir;
static struct dentry *orphandir;
static int inited = 0;

/* caller must hold prepare_lock */
static int clk_debug_create_one(struct clk *clk, struct dentry *pdentry)
{
	struct dentry *d;
	int ret = -ENOMEM;

	if (!clk || !pdentry) {
		ret = -EINVAL;
		goto out;
	}

	d = debugfs_create_dir(clk->name, pdentry);
	if (!d)
		goto out;

	clk->dentry = d;

	d = debugfs_create_u32("clk_rate", S_IRUGO, clk->dentry,
			(u32 *)&clk->rate);
	if (!d)
		goto err_out;

	d = debugfs_create_x32("clk_flags", S_IRUGO, clk->dentry,
			(u32 *)&clk->flags);
	if (!d)
		goto err_out;

	d = debugfs_create_u32("clk_prepare_count", S_IRUGO, clk->dentry,
			(u32 *)&clk->prepare_count);
	if (!d)
		goto err_out;

	d = debugfs_create_u32("clk_enable_count", S_IRUGO, clk->dentry,
			(u32 *)&clk->enable_count);
	if (!d)
		goto err_out;

	d = debugfs_create_u32("clk_notifier_count", S_IRUGO, clk->dentry,
			(u32 *)&clk->notifier_count);
	if (!d)
		goto err_out;

	ret = 0;
	goto out;

err_out:
	debugfs_remove(clk->dentry);
out:
	return ret;
}

/* caller must hold prepare_lock */
static int clk_debug_create_subtree(struct clk *clk, struct dentry *pdentry)
{
	struct clk *child;
	struct hlist_node *tmp;
	int ret = -EINVAL;;

	if (!clk || !pdentry)
		goto out;

	ret = clk_debug_create_one(clk, pdentry);

	if (ret)
		goto out;

	hlist_for_each_entry(child, tmp, &clk->children, child_node)
		clk_debug_create_subtree(child, clk->dentry);

	ret = 0;
out:
	return ret;
}

/**
 * clk_debug_register - add a clk node to the debugfs clk tree
 * @clk: the clk being added to the debugfs clk tree
 *
 * Dynamically adds a clk to the debugfs clk tree if debugfs has been
 * initialized.  Otherwise it bails out early since the debugfs clk tree
 * will be created lazily by clk_debug_init as part of a late_initcall.
 *
 * Caller must hold prepare_lock.  Only clk_init calls this function (so
 * far) so this is taken care.
 */
static int clk_debug_register(struct clk *clk)
{
	struct clk *parent;
	struct dentry *pdentry;
	int ret = 0;

	if (!inited)
		goto out;

	parent = clk->parent;

	/*
	 * Check to see if a clk is a root clk.  Also check that it is
	 * safe to add this clk to debugfs
	 */
	if (!parent)
		if (clk->flags & CLK_IS_ROOT)
			pdentry = rootdir;
		else
			pdentry = orphandir;
	else
		if (parent->dentry)
			pdentry = parent->dentry;
		else
			goto out;

	ret = clk_debug_create_subtree(clk, pdentry);

out:
	return ret;
}

/**
 * clk_debug_init - lazily create the debugfs clk tree visualization
 *
 * clks are often initialized very early during boot before memory can
 * be dynamically allocated and well before debugfs is setup.
 * clk_debug_init walks the clk tree hierarchy while holding
 * prepare_lock and creates the topology as part of a late_initcall,
 * thus insuring that clks initialized very early will still be
 * represented in the debugfs clk tree.  This function should only be
 * called once at boot-time, and all other clks added dynamically will
 * be done so with clk_debug_register.
 */
static int __init clk_debug_init(void)
{
	struct clk *clk;
	struct hlist_node *tmp;

	rootdir = debugfs_create_dir("clk", NULL);

	if (!rootdir)
		return -ENOMEM;

	orphandir = debugfs_create_dir("orphans", rootdir);

	if (!orphandir)
		return -ENOMEM;

	mutex_lock(&prepare_lock);

	hlist_for_each_entry(clk, tmp, &clk_root_list, child_node)
		clk_debug_create_subtree(clk, rootdir);

	hlist_for_each_entry(clk, tmp, &clk_orphan_list, child_node)
		clk_debug_create_subtree(clk, orphandir);

	inited = 1;

	mutex_unlock(&prepare_lock);

	return 0;
}
late_initcall(clk_debug_init);
#else
static inline int clk_debug_register(struct clk *clk) { return 0; }
197
#endif
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

/* caller must hold prepare_lock */
static void clk_disable_unused_subtree(struct clk *clk)
{
	struct clk *child;
	struct hlist_node *tmp;
	unsigned long flags;

	if (!clk)
		goto out;

	hlist_for_each_entry(child, tmp, &clk->children, child_node)
		clk_disable_unused_subtree(child);

	spin_lock_irqsave(&enable_lock, flags);

	if (clk->enable_count)
		goto unlock_out;

	if (clk->flags & CLK_IGNORE_UNUSED)
		goto unlock_out;

	if (__clk_is_enabled(clk) && clk->ops->disable)
		clk->ops->disable(clk->hw);

unlock_out:
	spin_unlock_irqrestore(&enable_lock, flags);

out:
	return;
}

static int clk_disable_unused(void)
{
	struct clk *clk;
	struct hlist_node *tmp;

	mutex_lock(&prepare_lock);

	hlist_for_each_entry(clk, tmp, &clk_root_list, child_node)
		clk_disable_unused_subtree(clk);

	hlist_for_each_entry(clk, tmp, &clk_orphan_list, child_node)
		clk_disable_unused_subtree(clk);

	mutex_unlock(&prepare_lock);

	return 0;
}
late_initcall(clk_disable_unused);

/***    helper functions   ***/

inline const char *__clk_get_name(struct clk *clk)
{
	return !clk ? NULL : clk->name;
}

inline struct clk_hw *__clk_get_hw(struct clk *clk)
{
	return !clk ? NULL : clk->hw;
}

inline u8 __clk_get_num_parents(struct clk *clk)
{
	return !clk ? -EINVAL : clk->num_parents;
}

inline struct clk *__clk_get_parent(struct clk *clk)
{
	return !clk ? NULL : clk->parent;
}

inline int __clk_get_enable_count(struct clk *clk)
{
	return !clk ? -EINVAL : clk->enable_count;
}

inline int __clk_get_prepare_count(struct clk *clk)
{
	return !clk ? -EINVAL : clk->prepare_count;
}

unsigned long __clk_get_rate(struct clk *clk)
{
	unsigned long ret;

	if (!clk) {
286
		ret = 0;
287 288 289 290 291 292 293 294 295
		goto out;
	}

	ret = clk->rate;

	if (clk->flags & CLK_IS_ROOT)
		goto out;

	if (!clk->parent)
296
		ret = 0;
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

out:
	return ret;
}

inline unsigned long __clk_get_flags(struct clk *clk)
{
	return !clk ? -EINVAL : clk->flags;
}

int __clk_is_enabled(struct clk *clk)
{
	int ret;

	if (!clk)
		return -EINVAL;

	/*
	 * .is_enabled is only mandatory for clocks that gate
	 * fall back to software usage counter if .is_enabled is missing
	 */
	if (!clk->ops->is_enabled) {
		ret = clk->enable_count ? 1 : 0;
		goto out;
	}

	ret = clk->ops->is_enabled(clk->hw);
out:
	return ret;
}

static struct clk *__clk_lookup_subtree(const char *name, struct clk *clk)
{
	struct clk *child;
	struct clk *ret;
	struct hlist_node *tmp;

	if (!strcmp(clk->name, name))
		return clk;

	hlist_for_each_entry(child, tmp, &clk->children, child_node) {
		ret = __clk_lookup_subtree(name, child);
		if (ret)
			return ret;
	}

	return NULL;
}

struct clk *__clk_lookup(const char *name)
{
	struct clk *root_clk;
	struct clk *ret;
	struct hlist_node *tmp;

	if (!name)
		return NULL;

	/* search the 'proper' clk tree first */
	hlist_for_each_entry(root_clk, tmp, &clk_root_list, child_node) {
		ret = __clk_lookup_subtree(name, root_clk);
		if (ret)
			return ret;
	}

	/* if not found, then search the orphan tree */
	hlist_for_each_entry(root_clk, tmp, &clk_orphan_list, child_node) {
		ret = __clk_lookup_subtree(name, root_clk);
		if (ret)
			return ret;
	}

	return NULL;
}

/***        clk api        ***/

void __clk_unprepare(struct clk *clk)
{
	if (!clk)
		return;

	if (WARN_ON(clk->prepare_count == 0))
		return;

	if (--clk->prepare_count > 0)
		return;

	WARN_ON(clk->enable_count > 0);

	if (clk->ops->unprepare)
		clk->ops->unprepare(clk->hw);

	__clk_unprepare(clk->parent);
}

/**
 * clk_unprepare - undo preparation of a clock source
 * @clk: the clk being unprepare
 *
 * clk_unprepare may sleep, which differentiates it from clk_disable.  In a
 * simple case, clk_unprepare can be used instead of clk_disable to gate a clk
 * if the operation may sleep.  One example is a clk which is accessed over
 * I2c.  In the complex case a clk gate operation may require a fast and a slow
 * part.  It is this reason that clk_unprepare and clk_disable are not mutually
 * exclusive.  In fact clk_disable must be called before clk_unprepare.
 */
void clk_unprepare(struct clk *clk)
{
	mutex_lock(&prepare_lock);
	__clk_unprepare(clk);
	mutex_unlock(&prepare_lock);
}
EXPORT_SYMBOL_GPL(clk_unprepare);

int __clk_prepare(struct clk *clk)
{
	int ret = 0;

	if (!clk)
		return 0;

	if (clk->prepare_count == 0) {
		ret = __clk_prepare(clk->parent);
		if (ret)
			return ret;

		if (clk->ops->prepare) {
			ret = clk->ops->prepare(clk->hw);
			if (ret) {
				__clk_unprepare(clk->parent);
				return ret;
			}
		}
	}

	clk->prepare_count++;

	return 0;
}

/**
 * clk_prepare - prepare a clock source
 * @clk: the clk being prepared
 *
 * clk_prepare may sleep, which differentiates it from clk_enable.  In a simple
 * case, clk_prepare can be used instead of clk_enable to ungate a clk if the
 * operation may sleep.  One example is a clk which is accessed over I2c.  In
 * the complex case a clk ungate operation may require a fast and a slow part.
 * It is this reason that clk_prepare and clk_enable are not mutually
 * exclusive.  In fact clk_prepare must be called before clk_enable.
 * Returns 0 on success, -EERROR otherwise.
 */
int clk_prepare(struct clk *clk)
{
	int ret;

	mutex_lock(&prepare_lock);
	ret = __clk_prepare(clk);
	mutex_unlock(&prepare_lock);

	return ret;
}
EXPORT_SYMBOL_GPL(clk_prepare);

static void __clk_disable(struct clk *clk)
{
	if (!clk)
		return;

	if (WARN_ON(clk->enable_count == 0))
		return;

	if (--clk->enable_count > 0)
		return;

	if (clk->ops->disable)
		clk->ops->disable(clk->hw);

	__clk_disable(clk->parent);
}

/**
 * clk_disable - gate a clock
 * @clk: the clk being gated
 *
 * clk_disable must not sleep, which differentiates it from clk_unprepare.  In
 * a simple case, clk_disable can be used instead of clk_unprepare to gate a
 * clk if the operation is fast and will never sleep.  One example is a
 * SoC-internal clk which is controlled via simple register writes.  In the
 * complex case a clk gate operation may require a fast and a slow part.  It is
 * this reason that clk_unprepare and clk_disable are not mutually exclusive.
 * In fact clk_disable must be called before clk_unprepare.
 */
void clk_disable(struct clk *clk)
{
	unsigned long flags;

	spin_lock_irqsave(&enable_lock, flags);
	__clk_disable(clk);
	spin_unlock_irqrestore(&enable_lock, flags);
}
EXPORT_SYMBOL_GPL(clk_disable);

static int __clk_enable(struct clk *clk)
{
	int ret = 0;

	if (!clk)
		return 0;

	if (WARN_ON(clk->prepare_count == 0))
		return -ESHUTDOWN;

	if (clk->enable_count == 0) {
		ret = __clk_enable(clk->parent);

		if (ret)
			return ret;

		if (clk->ops->enable) {
			ret = clk->ops->enable(clk->hw);
			if (ret) {
				__clk_disable(clk->parent);
				return ret;
			}
		}
	}

	clk->enable_count++;
	return 0;
}

/**
 * clk_enable - ungate a clock
 * @clk: the clk being ungated
 *
 * clk_enable must not sleep, which differentiates it from clk_prepare.  In a
 * simple case, clk_enable can be used instead of clk_prepare to ungate a clk
 * if the operation will never sleep.  One example is a SoC-internal clk which
 * is controlled via simple register writes.  In the complex case a clk ungate
 * operation may require a fast and a slow part.  It is this reason that
 * clk_enable and clk_prepare are not mutually exclusive.  In fact clk_prepare
 * must be called before clk_enable.  Returns 0 on success, -EERROR
 * otherwise.
 */
int clk_enable(struct clk *clk)
{
	unsigned long flags;
	int ret;

	spin_lock_irqsave(&enable_lock, flags);
	ret = __clk_enable(clk);
	spin_unlock_irqrestore(&enable_lock, flags);

	return ret;
}
EXPORT_SYMBOL_GPL(clk_enable);

/**
 * clk_get_rate - return the rate of clk
 * @clk: the clk whose rate is being returned
 *
 * Simply returns the cached rate of the clk.  Does not query the hardware.  If
561
 * clk is NULL then returns 0.
562 563 564 565 566 567 568 569 570 571 572 573 574 575 576 577 578 579 580 581 582
 */
unsigned long clk_get_rate(struct clk *clk)
{
	unsigned long rate;

	mutex_lock(&prepare_lock);
	rate = __clk_get_rate(clk);
	mutex_unlock(&prepare_lock);

	return rate;
}
EXPORT_SYMBOL_GPL(clk_get_rate);

/**
 * __clk_round_rate - round the given rate for a clk
 * @clk: round the rate of this clock
 *
 * Caller must hold prepare_lock.  Useful for clk_ops such as .set_rate
 */
unsigned long __clk_round_rate(struct clk *clk, unsigned long rate)
{
583
	unsigned long parent_rate = 0;
584 585 586 587

	if (!clk)
		return -EINVAL;

588 589 590 591 592 593
	if (!clk->ops->round_rate) {
		if (clk->flags & CLK_SET_RATE_PARENT)
			return __clk_round_rate(clk->parent, rate);
		else
			return clk->rate;
	}
594

595 596 597 598
	if (clk->parent)
		parent_rate = clk->parent->rate;

	return clk->ops->round_rate(clk->hw, rate, &parent_rate);
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
}

/**
 * clk_round_rate - round the given rate for a clk
 * @clk: the clk for which we are rounding a rate
 * @rate: the rate which is to be rounded
 *
 * Takes in a rate as input and rounds it to a rate that the clk can actually
 * use which is then returned.  If clk doesn't support round_rate operation
 * then the parent rate is returned.
 */
long clk_round_rate(struct clk *clk, unsigned long rate)
{
	unsigned long ret;

	mutex_lock(&prepare_lock);
	ret = __clk_round_rate(clk, rate);
	mutex_unlock(&prepare_lock);

	return ret;
}
EXPORT_SYMBOL_GPL(clk_round_rate);

/**
 * __clk_notify - call clk notifier chain
 * @clk: struct clk * that is changing rate
 * @msg: clk notifier type (see include/linux/clk.h)
 * @old_rate: old clk rate
 * @new_rate: new clk rate
 *
 * Triggers a notifier call chain on the clk rate-change notification
 * for 'clk'.  Passes a pointer to the struct clk and the previous
 * and current rates to the notifier callback.  Intended to be called by
 * internal clock code only.  Returns NOTIFY_DONE from the last driver
 * called if all went well, or NOTIFY_STOP or NOTIFY_BAD immediately if
 * a driver returns that.
 */
static int __clk_notify(struct clk *clk, unsigned long msg,
		unsigned long old_rate, unsigned long new_rate)
{
	struct clk_notifier *cn;
	struct clk_notifier_data cnd;
	int ret = NOTIFY_DONE;

	cnd.clk = clk;
	cnd.old_rate = old_rate;
	cnd.new_rate = new_rate;

	list_for_each_entry(cn, &clk_notifier_list, node) {
		if (cn->clk == clk) {
			ret = srcu_notifier_call_chain(&cn->notifier_head, msg,
					&cnd);
			break;
		}
	}

	return ret;
}

/**
 * __clk_recalc_rates
 * @clk: first clk in the subtree
 * @msg: notification type (see include/linux/clk.h)
 *
 * Walks the subtree of clks starting with clk and recalculates rates as it
 * goes.  Note that if a clk does not implement the .recalc_rate callback then
 * it is assumed that the clock will take on the rate of it's parent.
 *
 * clk_recalc_rates also propagates the POST_RATE_CHANGE notification,
 * if necessary.
 *
 * Caller must hold prepare_lock.
 */
static void __clk_recalc_rates(struct clk *clk, unsigned long msg)
{
	unsigned long old_rate;
	unsigned long parent_rate = 0;
	struct hlist_node *tmp;
	struct clk *child;

	old_rate = clk->rate;

	if (clk->parent)
		parent_rate = clk->parent->rate;

	if (clk->ops->recalc_rate)
		clk->rate = clk->ops->recalc_rate(clk->hw, parent_rate);
	else
		clk->rate = parent_rate;

	/*
	 * ignore NOTIFY_STOP and NOTIFY_BAD return values for POST_RATE_CHANGE
	 * & ABORT_RATE_CHANGE notifiers
	 */
	if (clk->notifier_count && msg)
		__clk_notify(clk, msg, old_rate, clk->rate);

	hlist_for_each_entry(child, tmp, &clk->children, child_node)
		__clk_recalc_rates(child, msg);
}

/**
 * __clk_speculate_rates
 * @clk: first clk in the subtree
 * @parent_rate: the "future" rate of clk's parent
 *
 * Walks the subtree of clks starting with clk, speculating rates as it
 * goes and firing off PRE_RATE_CHANGE notifications as necessary.
 *
 * Unlike clk_recalc_rates, clk_speculate_rates exists only for sending
 * pre-rate change notifications and returns early if no clks in the
 * subtree have subscribed to the notifications.  Note that if a clk does not
 * implement the .recalc_rate callback then it is assumed that the clock will
 * take on the rate of it's parent.
 *
 * Caller must hold prepare_lock.
 */
static int __clk_speculate_rates(struct clk *clk, unsigned long parent_rate)
{
	struct hlist_node *tmp;
	struct clk *child;
	unsigned long new_rate;
	int ret = NOTIFY_DONE;

	if (clk->ops->recalc_rate)
		new_rate = clk->ops->recalc_rate(clk->hw, parent_rate);
	else
		new_rate = parent_rate;

	/* abort the rate change if a driver returns NOTIFY_BAD */
	if (clk->notifier_count)
		ret = __clk_notify(clk, PRE_RATE_CHANGE, clk->rate, new_rate);

	if (ret == NOTIFY_BAD)
		goto out;

	hlist_for_each_entry(child, tmp, &clk->children, child_node) {
		ret = __clk_speculate_rates(child, new_rate);
		if (ret == NOTIFY_BAD)
			break;
	}

out:
	return ret;
}

static void clk_calc_subtree(struct clk *clk, unsigned long new_rate)
{
	struct clk *child;
	struct hlist_node *tmp;

	clk->new_rate = new_rate;

	hlist_for_each_entry(child, tmp, &clk->children, child_node) {
		if (child->ops->recalc_rate)
			child->new_rate = child->ops->recalc_rate(child->hw, new_rate);
		else
			child->new_rate = new_rate;
		clk_calc_subtree(child, child->new_rate);
	}
}

/*
 * calculate the new rates returning the topmost clock that has to be
 * changed.
 */
static struct clk *clk_calc_new_rates(struct clk *clk, unsigned long rate)
{
	struct clk *top = clk;
768
	unsigned long best_parent_rate = 0;
769 770
	unsigned long new_rate;

771 772 773 774
	/* sanity */
	if (IS_ERR_OR_NULL(clk))
		return NULL;

775 776 777 778
	/* save parent rate, if it exists */
	if (clk->parent)
		best_parent_rate = clk->parent->rate;

779 780 781 782 783 784
	/* never propagate up to the parent */
	if (!(clk->flags & CLK_SET_RATE_PARENT)) {
		if (!clk->ops->round_rate) {
			clk->new_rate = clk->rate;
			return NULL;
		}
785 786
		new_rate = clk->ops->round_rate(clk->hw, rate, &best_parent_rate);
		goto out;
787 788 789 790 791
	}

	/* need clk->parent from here on out */
	if (!clk->parent) {
		pr_debug("%s: %s has NULL parent\n", __func__, clk->name);
792 793 794
		return NULL;
	}

795
	if (!clk->ops->round_rate) {
796
		top = clk_calc_new_rates(clk->parent, rate);
797
		new_rate = clk->parent->new_rate;
798 799 800 801

		goto out;
	}

802
	new_rate = clk->ops->round_rate(clk->hw, rate, &best_parent_rate);
803 804 805 806 807 808 809 810 811 812 813 814 815 816 817 818 819 820 821 822 823 824 825 826 827 828 829 830 831 832 833 834 835 836 837 838 839 840 841 842 843 844 845 846 847 848 849 850 851 852 853 854 855 856 857

	if (best_parent_rate != clk->parent->rate) {
		top = clk_calc_new_rates(clk->parent, best_parent_rate);

		goto out;
	}

out:
	clk_calc_subtree(clk, new_rate);

	return top;
}

/*
 * Notify about rate changes in a subtree. Always walk down the whole tree
 * so that in case of an error we can walk down the whole tree again and
 * abort the change.
 */
static struct clk *clk_propagate_rate_change(struct clk *clk, unsigned long event)
{
	struct hlist_node *tmp;
	struct clk *child, *fail_clk = NULL;
	int ret = NOTIFY_DONE;

	if (clk->rate == clk->new_rate)
		return 0;

	if (clk->notifier_count) {
		ret = __clk_notify(clk, event, clk->rate, clk->new_rate);
		if (ret == NOTIFY_BAD)
			fail_clk = clk;
	}

	hlist_for_each_entry(child, tmp, &clk->children, child_node) {
		clk = clk_propagate_rate_change(child, event);
		if (clk)
			fail_clk = clk;
	}

	return fail_clk;
}

/*
 * walk down a subtree and set the new rates notifying the rate
 * change on the way
 */
static void clk_change_rate(struct clk *clk)
{
	struct clk *child;
	unsigned long old_rate;
	struct hlist_node *tmp;

	old_rate = clk->rate;

	if (clk->ops->set_rate)
S
Shawn Guo 已提交
858
		clk->ops->set_rate(clk->hw, clk->new_rate, clk->parent->rate);
859 860 861 862 863 864 865 866 867 868 869 870 871 872 873 874 875 876 877

	if (clk->ops->recalc_rate)
		clk->rate = clk->ops->recalc_rate(clk->hw,
				clk->parent->rate);
	else
		clk->rate = clk->parent->rate;

	if (clk->notifier_count && old_rate != clk->rate)
		__clk_notify(clk, POST_RATE_CHANGE, old_rate, clk->rate);

	hlist_for_each_entry(child, tmp, &clk->children, child_node)
		clk_change_rate(child);
}

/**
 * clk_set_rate - specify a new rate for clk
 * @clk: the clk whose rate is being changed
 * @rate: the new rate for clk
 *
878
 * In the simplest case clk_set_rate will only adjust the rate of clk.
879
 *
880 881 882 883 884 885 886 887
 * Setting the CLK_SET_RATE_PARENT flag allows the rate change operation to
 * propagate up to clk's parent; whether or not this happens depends on the
 * outcome of clk's .round_rate implementation.  If *parent_rate is unchanged
 * after calling .round_rate then upstream parent propagation is ignored.  If
 * *parent_rate comes back with a new rate for clk's parent then we propagate
 * up to clk's parent and set it's rate.  Upward propagation will continue
 * until either a clk does not support the CLK_SET_RATE_PARENT flag or
 * .round_rate stops requesting changes to clk's parent_rate.
888
 *
889 890
 * Rate changes are accomplished via tree traversal that also recalculates the
 * rates for the clocks and fires off POST_RATE_CHANGE notifiers.
891 892 893 894 895 896 897 898 899 900 901 902 903 904 905
 *
 * Returns 0 on success, -EERROR otherwise.
 */
int clk_set_rate(struct clk *clk, unsigned long rate)
{
	struct clk *top, *fail_clk;
	int ret = 0;

	/* prevent racing with updates to the clock topology */
	mutex_lock(&prepare_lock);

	/* bail early if nothing to do */
	if (rate == clk->rate)
		goto out;

906 907 908 909 910
	if ((clk->flags & CLK_SET_RATE_GATE) && __clk_is_enabled(clk)) {
		ret = -EBUSY;
		goto out;
	}

911 912 913 914 915 916 917 918 919 920 921 922 923 924 925 926 927 928 929 930 931 932 933 934 935 936 937 938 939 940 941 942 943 944 945 946 947 948 949 950 951 952 953 954 955 956 957 958 959 960 961 962 963 964 965 966 967 968 969 970 971 972 973 974 975 976 977 978 979 980 981 982 983 984 985 986 987 988 989 990 991 992 993 994 995 996 997 998 999 1000 1001 1002 1003 1004 1005 1006 1007 1008 1009 1010 1011 1012 1013 1014 1015 1016 1017 1018 1019 1020 1021 1022 1023 1024 1025 1026 1027 1028 1029 1030 1031 1032 1033 1034 1035 1036 1037 1038 1039 1040 1041 1042 1043 1044 1045 1046 1047 1048 1049 1050 1051 1052 1053 1054 1055 1056 1057 1058 1059 1060 1061 1062 1063 1064 1065 1066 1067 1068 1069 1070 1071 1072 1073 1074 1075 1076 1077 1078 1079 1080 1081 1082 1083 1084 1085 1086 1087 1088 1089 1090 1091 1092 1093 1094 1095 1096 1097 1098 1099 1100 1101 1102 1103 1104 1105 1106 1107 1108 1109 1110 1111 1112 1113 1114 1115 1116 1117 1118 1119 1120 1121 1122 1123 1124 1125 1126 1127 1128 1129 1130 1131 1132 1133 1134 1135 1136 1137 1138 1139 1140 1141 1142 1143 1144 1145 1146 1147 1148 1149 1150 1151 1152 1153 1154 1155 1156 1157 1158 1159 1160 1161 1162 1163 1164 1165 1166 1167 1168 1169 1170 1171 1172 1173 1174 1175 1176 1177 1178 1179 1180
	/* calculate new rates and get the topmost changed clock */
	top = clk_calc_new_rates(clk, rate);
	if (!top) {
		ret = -EINVAL;
		goto out;
	}

	/* notify that we are about to change rates */
	fail_clk = clk_propagate_rate_change(top, PRE_RATE_CHANGE);
	if (fail_clk) {
		pr_warn("%s: failed to set %s rate\n", __func__,
				fail_clk->name);
		clk_propagate_rate_change(top, ABORT_RATE_CHANGE);
		ret = -EBUSY;
		goto out;
	}

	/* change the rates */
	clk_change_rate(top);

	mutex_unlock(&prepare_lock);

	return 0;
out:
	mutex_unlock(&prepare_lock);

	return ret;
}
EXPORT_SYMBOL_GPL(clk_set_rate);

/**
 * clk_get_parent - return the parent of a clk
 * @clk: the clk whose parent gets returned
 *
 * Simply returns clk->parent.  Returns NULL if clk is NULL.
 */
struct clk *clk_get_parent(struct clk *clk)
{
	struct clk *parent;

	mutex_lock(&prepare_lock);
	parent = __clk_get_parent(clk);
	mutex_unlock(&prepare_lock);

	return parent;
}
EXPORT_SYMBOL_GPL(clk_get_parent);

/*
 * .get_parent is mandatory for clocks with multiple possible parents.  It is
 * optional for single-parent clocks.  Always call .get_parent if it is
 * available and WARN if it is missing for multi-parent clocks.
 *
 * For single-parent clocks without .get_parent, first check to see if the
 * .parents array exists, and if so use it to avoid an expensive tree
 * traversal.  If .parents does not exist then walk the tree with __clk_lookup.
 */
static struct clk *__clk_init_parent(struct clk *clk)
{
	struct clk *ret = NULL;
	u8 index;

	/* handle the trivial cases */

	if (!clk->num_parents)
		goto out;

	if (clk->num_parents == 1) {
		if (IS_ERR_OR_NULL(clk->parent))
			ret = clk->parent = __clk_lookup(clk->parent_names[0]);
		ret = clk->parent;
		goto out;
	}

	if (!clk->ops->get_parent) {
		WARN(!clk->ops->get_parent,
			"%s: multi-parent clocks must implement .get_parent\n",
			__func__);
		goto out;
	};

	/*
	 * Do our best to cache parent clocks in clk->parents.  This prevents
	 * unnecessary and expensive calls to __clk_lookup.  We don't set
	 * clk->parent here; that is done by the calling function
	 */

	index = clk->ops->get_parent(clk->hw);

	if (!clk->parents)
		clk->parents =
			kmalloc((sizeof(struct clk*) * clk->num_parents),
					GFP_KERNEL);

	if (!clk->parents)
		ret = __clk_lookup(clk->parent_names[index]);
	else if (!clk->parents[index])
		ret = clk->parents[index] =
			__clk_lookup(clk->parent_names[index]);
	else
		ret = clk->parents[index];

out:
	return ret;
}

void __clk_reparent(struct clk *clk, struct clk *new_parent)
{
#ifdef CONFIG_COMMON_CLK_DEBUG
	struct dentry *d;
	struct dentry *new_parent_d;
#endif

	if (!clk || !new_parent)
		return;

	hlist_del(&clk->child_node);

	if (new_parent)
		hlist_add_head(&clk->child_node, &new_parent->children);
	else
		hlist_add_head(&clk->child_node, &clk_orphan_list);

#ifdef CONFIG_COMMON_CLK_DEBUG
	if (!inited)
		goto out;

	if (new_parent)
		new_parent_d = new_parent->dentry;
	else
		new_parent_d = orphandir;

	d = debugfs_rename(clk->dentry->d_parent, clk->dentry,
			new_parent_d, clk->name);
	if (d)
		clk->dentry = d;
	else
		pr_debug("%s: failed to rename debugfs entry for %s\n",
				__func__, clk->name);
out:
#endif

	clk->parent = new_parent;

	__clk_recalc_rates(clk, POST_RATE_CHANGE);
}

static int __clk_set_parent(struct clk *clk, struct clk *parent)
{
	struct clk *old_parent;
	unsigned long flags;
	int ret = -EINVAL;
	u8 i;

	old_parent = clk->parent;

	/* find index of new parent clock using cached parent ptrs */
	for (i = 0; i < clk->num_parents; i++)
		if (clk->parents[i] == parent)
			break;

	/*
	 * find index of new parent clock using string name comparison
	 * also try to cache the parent to avoid future calls to __clk_lookup
	 */
	if (i == clk->num_parents)
		for (i = 0; i < clk->num_parents; i++)
			if (!strcmp(clk->parent_names[i], parent->name)) {
				clk->parents[i] = __clk_lookup(parent->name);
				break;
			}

	if (i == clk->num_parents) {
		pr_debug("%s: clock %s is not a possible parent of clock %s\n",
				__func__, parent->name, clk->name);
		goto out;
	}

	/* migrate prepare and enable */
	if (clk->prepare_count)
		__clk_prepare(parent);

	/* FIXME replace with clk_is_enabled(clk) someday */
	spin_lock_irqsave(&enable_lock, flags);
	if (clk->enable_count)
		__clk_enable(parent);
	spin_unlock_irqrestore(&enable_lock, flags);

	/* change clock input source */
	ret = clk->ops->set_parent(clk->hw, i);

	/* clean up old prepare and enable */
	spin_lock_irqsave(&enable_lock, flags);
	if (clk->enable_count)
		__clk_disable(old_parent);
	spin_unlock_irqrestore(&enable_lock, flags);

	if (clk->prepare_count)
		__clk_unprepare(old_parent);

out:
	return ret;
}

/**
 * clk_set_parent - switch the parent of a mux clk
 * @clk: the mux clk whose input we are switching
 * @parent: the new input to clk
 *
 * Re-parent clk to use parent as it's new input source.  If clk has the
 * CLK_SET_PARENT_GATE flag set then clk must be gated for this
 * operation to succeed.  After successfully changing clk's parent
 * clk_set_parent will update the clk topology, sysfs topology and
 * propagate rate recalculation via __clk_recalc_rates.  Returns 0 on
 * success, -EERROR otherwise.
 */
int clk_set_parent(struct clk *clk, struct clk *parent)
{
	int ret = 0;

	if (!clk || !clk->ops)
		return -EINVAL;

	if (!clk->ops->set_parent)
		return -ENOSYS;

	/* prevent racing with updates to the clock topology */
	mutex_lock(&prepare_lock);

	if (clk->parent == parent)
		goto out;

	/* propagate PRE_RATE_CHANGE notifications */
	if (clk->notifier_count)
		ret = __clk_speculate_rates(clk, parent->rate);

	/* abort if a driver objects */
	if (ret == NOTIFY_STOP)
		goto out;

	/* only re-parent if the clock is not in use */
	if ((clk->flags & CLK_SET_PARENT_GATE) && clk->prepare_count)
		ret = -EBUSY;
	else
		ret = __clk_set_parent(clk, parent);

	/* propagate ABORT_RATE_CHANGE if .set_parent failed */
	if (ret) {
		__clk_recalc_rates(clk, ABORT_RATE_CHANGE);
		goto out;
	}

	/* propagate rate recalculation downstream */
	__clk_reparent(clk, parent);

out:
	mutex_unlock(&prepare_lock);

	return ret;
}
EXPORT_SYMBOL_GPL(clk_set_parent);

/**
 * __clk_init - initialize the data structures in a struct clk
 * @dev:	device initializing this clk, placeholder for now
 * @clk:	clk being initialized
 *
 * Initializes the lists in struct clk, queries the hardware for the
 * parent and rate and sets them both.
 */
1181
int __clk_init(struct device *dev, struct clk *clk)
1182
{
1183
	int i, ret = 0;
1184 1185 1186 1187
	struct clk *orphan;
	struct hlist_node *tmp, *tmp2;

	if (!clk)
1188
		return -EINVAL;
1189 1190 1191 1192

	mutex_lock(&prepare_lock);

	/* check to see if a clock with this name is already registered */
1193 1194 1195 1196
	if (__clk_lookup(clk->name)) {
		pr_debug("%s: clk %s already initialized\n",
				__func__, clk->name);
		ret = -EEXIST;
1197
		goto out;
1198
	}
1199

1200 1201 1202 1203 1204
	/* check that clk_ops are sane.  See Documentation/clk.txt */
	if (clk->ops->set_rate &&
			!(clk->ops->round_rate && clk->ops->recalc_rate)) {
		pr_warning("%s: %s must implement .round_rate & .recalc_rate\n",
				__func__, clk->name);
1205
		ret = -EINVAL;
1206 1207 1208 1209 1210 1211
		goto out;
	}

	if (clk->ops->set_parent && !clk->ops->get_parent) {
		pr_warning("%s: %s must implement .get_parent & .set_parent\n",
				__func__, clk->name);
1212
		ret = -EINVAL;
1213 1214 1215
		goto out;
	}

1216 1217 1218 1219 1220 1221 1222 1223 1224 1225 1226 1227 1228 1229 1230 1231 1232 1233 1234 1235 1236 1237 1238 1239 1240 1241 1242 1243 1244 1245 1246 1247 1248 1249 1250 1251 1252 1253 1254 1255 1256 1257 1258 1259 1260 1261 1262 1263 1264 1265 1266 1267 1268 1269 1270 1271 1272 1273 1274 1275 1276 1277 1278 1279 1280 1281 1282 1283 1284 1285 1286 1287 1288 1289 1290 1291 1292 1293 1294 1295 1296 1297 1298 1299 1300 1301 1302 1303 1304 1305 1306 1307
	/* throw a WARN if any entries in parent_names are NULL */
	for (i = 0; i < clk->num_parents; i++)
		WARN(!clk->parent_names[i],
				"%s: invalid NULL in %s's .parent_names\n",
				__func__, clk->name);

	/*
	 * Allocate an array of struct clk *'s to avoid unnecessary string
	 * look-ups of clk's possible parents.  This can fail for clocks passed
	 * in to clk_init during early boot; thus any access to clk->parents[]
	 * must always check for a NULL pointer and try to populate it if
	 * necessary.
	 *
	 * If clk->parents is not NULL we skip this entire block.  This allows
	 * for clock drivers to statically initialize clk->parents.
	 */
	if (clk->num_parents && !clk->parents) {
		clk->parents = kmalloc((sizeof(struct clk*) * clk->num_parents),
				GFP_KERNEL);
		/*
		 * __clk_lookup returns NULL for parents that have not been
		 * clk_init'd; thus any access to clk->parents[] must check
		 * for a NULL pointer.  We can always perform lazy lookups for
		 * missing parents later on.
		 */
		if (clk->parents)
			for (i = 0; i < clk->num_parents; i++)
				clk->parents[i] =
					__clk_lookup(clk->parent_names[i]);
	}

	clk->parent = __clk_init_parent(clk);

	/*
	 * Populate clk->parent if parent has already been __clk_init'd.  If
	 * parent has not yet been __clk_init'd then place clk in the orphan
	 * list.  If clk has set the CLK_IS_ROOT flag then place it in the root
	 * clk list.
	 *
	 * Every time a new clk is clk_init'd then we walk the list of orphan
	 * clocks and re-parent any that are children of the clock currently
	 * being clk_init'd.
	 */
	if (clk->parent)
		hlist_add_head(&clk->child_node,
				&clk->parent->children);
	else if (clk->flags & CLK_IS_ROOT)
		hlist_add_head(&clk->child_node, &clk_root_list);
	else
		hlist_add_head(&clk->child_node, &clk_orphan_list);

	/*
	 * Set clk's rate.  The preferred method is to use .recalc_rate.  For
	 * simple clocks and lazy developers the default fallback is to use the
	 * parent's rate.  If a clock doesn't have a parent (or is orphaned)
	 * then rate is set to zero.
	 */
	if (clk->ops->recalc_rate)
		clk->rate = clk->ops->recalc_rate(clk->hw,
				__clk_get_rate(clk->parent));
	else if (clk->parent)
		clk->rate = clk->parent->rate;
	else
		clk->rate = 0;

	/*
	 * walk the list of orphan clocks and reparent any that are children of
	 * this clock
	 */
	hlist_for_each_entry_safe(orphan, tmp, tmp2, &clk_orphan_list, child_node)
		for (i = 0; i < orphan->num_parents; i++)
			if (!strcmp(clk->name, orphan->parent_names[i])) {
				__clk_reparent(orphan, clk);
				break;
			}

	/*
	 * optional platform-specific magic
	 *
	 * The .init callback is not used by any of the basic clock types, but
	 * exists for weird hardware that must perform initialization magic.
	 * Please consider other ways of solving initialization problems before
	 * using this callback, as it's use is discouraged.
	 */
	if (clk->ops->init)
		clk->ops->init(clk->hw);

	clk_debug_register(clk);

out:
	mutex_unlock(&prepare_lock);

1308
	return ret;
1309 1310
}

1311 1312 1313 1314 1315 1316 1317 1318 1319 1320 1321 1322 1323 1324 1325 1326 1327 1328 1329 1330 1331 1332 1333 1334 1335 1336 1337 1338 1339 1340 1341 1342 1343 1344 1345 1346 1347 1348
/**
 * __clk_register - register a clock and return a cookie.
 *
 * Same as clk_register, except that the .clk field inside hw shall point to a
 * preallocated (generally statically allocated) struct clk. None of the fields
 * of the struct clk need to be initialized.
 *
 * The data pointed to by .init and .clk field shall NOT be marked as init
 * data.
 *
 * __clk_register is only exposed via clk-private.h and is intended for use with
 * very large numbers of clocks that need to be statically initialized.  It is
 * a layering violation to include clk-private.h from any code which implements
 * a clock's .ops; as such any statically initialized clock data MUST be in a
 * separate C file from the logic that implements it's operations.  Returns 0
 * on success, otherwise an error code.
 */
struct clk *__clk_register(struct device *dev, struct clk_hw *hw)
{
	int ret;
	struct clk *clk;

	clk = hw->clk;
	clk->name = hw->init->name;
	clk->ops = hw->init->ops;
	clk->hw = hw;
	clk->flags = hw->init->flags;
	clk->parent_names = hw->init->parent_names;
	clk->num_parents = hw->init->num_parents;

	ret = __clk_init(dev, clk);
	if (ret)
		return ERR_PTR(ret);

	return clk;
}
EXPORT_SYMBOL_GPL(__clk_register);

1349 1350 1351 1352 1353 1354 1355 1356
/**
 * clk_register - allocate a new clock, register it and return an opaque cookie
 * @dev: device that is registering this clock
 * @hw: link to hardware-specific clock data
 *
 * clk_register is the primary interface for populating the clock tree with new
 * clock nodes.  It returns a pointer to the newly allocated struct clk which
 * cannot be dereferenced by driver code but may be used in conjuction with the
1357 1358
 * rest of the clock API.  In the event of an error clk_register will return an
 * error code; drivers must test for an error code after calling clk_register.
1359
 */
1360
struct clk *clk_register(struct device *dev, struct clk_hw *hw)
1361
{
1362
	int i, ret;
1363 1364 1365
	struct clk *clk;

	clk = kzalloc(sizeof(*clk), GFP_KERNEL);
1366 1367 1368 1369 1370
	if (!clk) {
		pr_err("%s: could not allocate clk\n", __func__);
		ret = -ENOMEM;
		goto fail_out;
	}
1371

1372 1373 1374 1375 1376 1377 1378
	clk->name = kstrdup(hw->init->name, GFP_KERNEL);
	if (!clk->name) {
		pr_err("%s: could not allocate clk->name\n", __func__);
		ret = -ENOMEM;
		goto fail_name;
	}
	clk->ops = hw->init->ops;
1379
	clk->hw = hw;
1380 1381
	clk->flags = hw->init->flags;
	clk->num_parents = hw->init->num_parents;
1382 1383
	hw->clk = clk;

1384
	/* allocate local copy in case parent_names is __initdata */
1385
	clk->parent_names = kzalloc((sizeof(char*) * clk->num_parents),
1386 1387 1388 1389 1390 1391 1392 1393 1394 1395
			GFP_KERNEL);

	if (!clk->parent_names) {
		pr_err("%s: could not allocate clk->parent_names\n", __func__);
		ret = -ENOMEM;
		goto fail_parent_names;
	}


	/* copy each string name in case parent_names is __initdata */
1396 1397 1398
	for (i = 0; i < clk->num_parents; i++) {
		clk->parent_names[i] = kstrdup(hw->init->parent_names[i],
						GFP_KERNEL);
1399 1400 1401 1402 1403 1404 1405 1406 1407 1408
		if (!clk->parent_names[i]) {
			pr_err("%s: could not copy parent_names\n", __func__);
			ret = -ENOMEM;
			goto fail_parent_names_copy;
		}
	}

	ret = __clk_init(dev, clk);
	if (!ret)
		return clk;
1409

1410 1411 1412 1413 1414
fail_parent_names_copy:
	while (--i >= 0)
		kfree(clk->parent_names[i]);
	kfree(clk->parent_names);
fail_parent_names:
1415 1416
	kfree(clk->name);
fail_name:
1417 1418 1419
	kfree(clk);
fail_out:
	return ERR_PTR(ret);
1420 1421 1422 1423 1424 1425 1426 1427 1428 1429 1430 1431 1432 1433 1434 1435 1436 1437 1438 1439 1440 1441 1442 1443 1444 1445 1446 1447 1448 1449 1450 1451 1452 1453 1454 1455 1456 1457 1458 1459 1460 1461 1462 1463 1464 1465 1466 1467 1468 1469 1470 1471 1472 1473 1474 1475 1476 1477 1478 1479 1480 1481 1482 1483 1484 1485 1486 1487 1488 1489 1490 1491 1492 1493 1494 1495 1496 1497 1498 1499 1500 1501 1502 1503 1504 1505 1506 1507 1508 1509 1510 1511 1512 1513 1514 1515 1516 1517 1518 1519 1520 1521 1522 1523 1524 1525 1526 1527 1528 1529 1530 1531 1532 1533 1534 1535 1536 1537
}
EXPORT_SYMBOL_GPL(clk_register);

/***        clk rate change notifiers        ***/

/**
 * clk_notifier_register - add a clk rate change notifier
 * @clk: struct clk * to watch
 * @nb: struct notifier_block * with callback info
 *
 * Request notification when clk's rate changes.  This uses an SRCU
 * notifier because we want it to block and notifier unregistrations are
 * uncommon.  The callbacks associated with the notifier must not
 * re-enter into the clk framework by calling any top-level clk APIs;
 * this will cause a nested prepare_lock mutex.
 *
 * Pre-change notifier callbacks will be passed the current, pre-change
 * rate of the clk via struct clk_notifier_data.old_rate.  The new,
 * post-change rate of the clk is passed via struct
 * clk_notifier_data.new_rate.
 *
 * Post-change notifiers will pass the now-current, post-change rate of
 * the clk in both struct clk_notifier_data.old_rate and struct
 * clk_notifier_data.new_rate.
 *
 * Abort-change notifiers are effectively the opposite of pre-change
 * notifiers: the original pre-change clk rate is passed in via struct
 * clk_notifier_data.new_rate and the failed post-change rate is passed
 * in via struct clk_notifier_data.old_rate.
 *
 * clk_notifier_register() must be called from non-atomic context.
 * Returns -EINVAL if called with null arguments, -ENOMEM upon
 * allocation failure; otherwise, passes along the return value of
 * srcu_notifier_chain_register().
 */
int clk_notifier_register(struct clk *clk, struct notifier_block *nb)
{
	struct clk_notifier *cn;
	int ret = -ENOMEM;

	if (!clk || !nb)
		return -EINVAL;

	mutex_lock(&prepare_lock);

	/* search the list of notifiers for this clk */
	list_for_each_entry(cn, &clk_notifier_list, node)
		if (cn->clk == clk)
			break;

	/* if clk wasn't in the notifier list, allocate new clk_notifier */
	if (cn->clk != clk) {
		cn = kzalloc(sizeof(struct clk_notifier), GFP_KERNEL);
		if (!cn)
			goto out;

		cn->clk = clk;
		srcu_init_notifier_head(&cn->notifier_head);

		list_add(&cn->node, &clk_notifier_list);
	}

	ret = srcu_notifier_chain_register(&cn->notifier_head, nb);

	clk->notifier_count++;

out:
	mutex_unlock(&prepare_lock);

	return ret;
}
EXPORT_SYMBOL_GPL(clk_notifier_register);

/**
 * clk_notifier_unregister - remove a clk rate change notifier
 * @clk: struct clk *
 * @nb: struct notifier_block * with callback info
 *
 * Request no further notification for changes to 'clk' and frees memory
 * allocated in clk_notifier_register.
 *
 * Returns -EINVAL if called with null arguments; otherwise, passes
 * along the return value of srcu_notifier_chain_unregister().
 */
int clk_notifier_unregister(struct clk *clk, struct notifier_block *nb)
{
	struct clk_notifier *cn = NULL;
	int ret = -EINVAL;

	if (!clk || !nb)
		return -EINVAL;

	mutex_lock(&prepare_lock);

	list_for_each_entry(cn, &clk_notifier_list, node)
		if (cn->clk == clk)
			break;

	if (cn->clk == clk) {
		ret = srcu_notifier_chain_unregister(&cn->notifier_head, nb);

		clk->notifier_count--;

		/* XXX the notifier code should handle this better */
		if (!cn->notifier_head.head) {
			srcu_cleanup_notifier_head(&cn->notifier_head);
			kfree(cn);
		}

	} else {
		ret = -ENOENT;
	}

	mutex_unlock(&prepare_lock);

	return ret;
}
EXPORT_SYMBOL_GPL(clk_notifier_unregister);