[v6,2/3] clk: introduce the common clock framework

Message ID 1331366064-1273-3-git-send-email-mturquette@linaro.org
State New
Headers show

Commit Message

Mike Turquette March 10, 2012, 7:54 a.m.
The common clock framework defines a common struct clk useful across
most platforms as well as an implementation of the clk api that drivers
can use safely for managing clocks.

The net result is consolidation of many different struct clk definitions
and platform-specific clock framework implementations.

This patch introduces the common struct clk, struct clk_ops and an
implementation of the well-known clock api in include/clk/clk.h.
Platforms may define their own hardware-specific clock structure and
their own clock operation callbacks, so long as it wraps an instance of
struct clk_hw.

See Documentation/clk.txt for more details.

This patch is based on the work of Jeremy Kerr, which in turn was based
on the work of Ben Herrenschmidt.

Signed-off-by: Mike Turquette <mturquette@linaro.org>
Signed-off-by: Mike Turquette <mturquette@ti.com>
Cc: Russell King <linux@arm.linux.org.uk>
Cc: Jeremy Kerr <jeremy.kerr@canonical.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Arnd Bergman <arnd.bergmann@linaro.org>
Cc: Paul Walmsley <paul@pwsan.com>
Cc: Shawn Guo <shawn.guo@freescale.com>
Cc: Sascha Hauer <s.hauer@pengutronix.de>
Cc: Richard Zhao <richard.zhao@linaro.org>
Cc: Saravana Kannan <skannan@codeaurora.org>
Cc: Magnus Damm <magnus.damm@gmail.com>
Cc: Rob Herring <rob.herring@calxeda.com>
Cc: Mark Brown <broonie@opensource.wolfsonmicro.com>
Cc: Linus Walleij <linus.walleij@stericsson.com>
Cc: Stephen Boyd <sboyd@codeaurora.org>
Cc: Amit Kucheria <amit.kucheria@linaro.org>
Cc: Deepak Saxena <dsaxena@linaro.org>
Cc: Grant Likely <grant.likely@secretlab.ca>
Cc: Andrew Lunn <andrew@lunn.ch>
---
Changes since v5:
 * new CONFIG_COMMON_CLK_DISABLE_UNUSED feature
  * results in a new clk_op callback, .is_enabled
 * new helpers
  * __clk_get_prepare_count
  * __clk_get_enable_count
  * __clk_is_enabled
 * fix bug in __clk_get_rate for orphan clocks

 drivers/clk/Kconfig          |   39 ++
 drivers/clk/Makefile         |    1 +
 drivers/clk/clk.c            | 1424 ++++++++++++++++++++++++++++++++++++++++++
 include/linux/clk-private.h  |   68 ++
 include/linux/clk-provider.h |  171 +++++
 include/linux/clk.h          |   68 ++-
 6 files changed, 1766 insertions(+), 5 deletions(-)
 create mode 100644 drivers/clk/clk.c
 create mode 100644 include/linux/clk-private.h
 create mode 100644 include/linux/clk-provider.h

Comments

Thomas Gleixner March 10, 2012, 10:51 a.m. | #1
On Fri, 9 Mar 2012, Mike Turquette wrote:
> +inline unsigned long __clk_get_enable_count(struct clk *clk)
> +{
> +	return !clk ? -EINVAL : clk->enable_count;

Returning negative error codes in a function with a return value
unsigned long is a bit strange at least. Shouldn't that be long ?

> +#ifndef __LINUX_CLK_PRIVATE_H
> +#define __LINUX_CLK_PRIVATE_H
> +
> +#include <linux/clk-provider.h>
> +#include <linux/list.h>
> +
> +/*
> + * WARNING: Do not include clk-private.h from any file that implements struct
> + * clk_ops.  Doing so is a layering violation!
> + *
> + * This header exists only to allow for statically initialized clock data.  Any
> + * static clock data must be defined in a separate file from the logic that
> + * implements the clock operations for that same data.

Now the question is whether you should provide a data structure which
is explicitely used for static initialization and instead of having
struct clk static you register the static initializer structure, which
would be initdata. I don't think that anything needs clocks before the
memory allocators are up and running. The clocks which are necessary
to get that far have to be enabled in the boot loader anyway.

The static initialization question should not hold off this set from
being merged, though settling it before growing users would be nice.

Otherwise this is a very well done infrastructure implementation!
Thanks a lot Mike!

Reviewed-by: Thomas Gleixner <tglx@linutronix.de>
Andrew Lunn March 10, 2012, 5:51 p.m. | #2
On Fri, Mar 09, 2012 at 11:54:23PM -0800, Mike Turquette wrote:
> The common clock framework defines a common struct clk useful across
> most platforms as well as an implementation of the clk api that drivers
> can use safely for managing clocks.

Hi Mike

Please feel free to add:

Tested-by: Andrew Lunn <andrew@lunn.ch>

	   Andrew
Richard Zhao March 11, 2012, 7:52 a.m. | #3
Looks like you didn't take my comments for v5.
http://www.spinics.net/lists/arm-kernel/msg162903.html 

Regards
Richard
Sascha Hauer March 11, 2012, 11:34 a.m. | #4
Hi Mike,

I was about to give my tested-by when I decided to test the set_rate
function. Unfortunately this is broken for several reasons. I'll try
to come up with a fixup series later the day.

On Fri, Mar 09, 2012 at 11:54:23PM -0800, Mike Turquette wrote:
> +
> +/**
> + * DOC: Using the CLK_SET_RATE_PARENT flag
> + *
> + * __clk_set_rate changes the child's rate before the parent's to more
> + * easily handle failure conditions.
> + *
> + * This means clk might run out of spec for a short time if its rate is
> + * increased before the parent's rate is updated.
> + *
> + * To prevent this consider setting the CLK_SET_RATE_GATE flag on any
> + * clk where you also set the CLK_SET_RATE_PARENT flag
> + *
> + * PRE_RATE_CHANGE notifications are supposed to stack as a rate change
> + * request propagates up the clk tree.  This reflects the different
> + * rates that a downstream clk might experience if left enabled while
> + * upstream parents change their rates.
> + */
> +static struct clk *__clk_set_rate(struct clk *clk, unsigned long rate)
> +{
> +	struct clk *fail_clk = NULL;
> +	int ret = NOTIFY_DONE;
> +	unsigned long old_rate = clk->rate;
> +	unsigned long new_rate;
> +	unsigned long parent_old_rate;
> +	unsigned long parent_new_rate = 0;
> +	struct clk *child;
> +	struct hlist_node *tmp;
> +
> +	/* bail early if we can't change rate while clk is enabled */
> +	if ((clk->flags & CLK_SET_RATE_GATE) && clk->enable_count)
> +		return clk;
> +
> +	/* find the new rate and see if parent rate should change too */
> +	WARN_ON(!clk->ops->round_rate);
> +
> +	new_rate = clk->ops->round_rate(clk->hw, rate, &parent_new_rate);

You don't need a WARN_ON when you derefence clk->ops->round_rate anyway.
Also, even when the current clock does not have a set_rate function it
can still change its rate when the CLK_SET_RATE_PARENT is set.

> +
> +	/* NOTE: pre-rate change notifications will stack */
> +	if (clk->notifier_count)
> +		ret = __clk_notify(clk, PRE_RATE_CHANGE, clk->rate, new_rate);
> +
> +	if (ret == NOTIFY_BAD)
> +		return clk;
> +
> +	/* speculate rate changes down the tree */
> +	hlist_for_each_entry(child, tmp, &clk->children, child_node) {
> +		ret = __clk_speculate_rates(child, new_rate);
> +		if (ret == NOTIFY_BAD)
> +			return clk;
> +	}
> +
> +	/* change the rate of this clk */
> +	if (clk->ops->set_rate)
> +		ret = clk->ops->set_rate(clk->hw, new_rate);

I don't know the reason why you change the child clock before the parent
clock, but it cannot work since this clock will change its rate based on
the old parent rate and not the new one.

There are more things, as said I'll try to come up with a fixup series.

Sascha
Mike Turquette March 11, 2012, 9:02 p.m. | #5
On Sat, Mar 10, 2012 at 11:52 PM, Richard Zhao <richard.zhao@linaro.org> wrote:
> Looks like you didn't take my comments for v5.
> http://www.spinics.net/lists/arm-kernel/msg162903.html

Sorry Richard, that one slipped through the cracks.  I'll publish a
new version tomorrow with some of those fixes.  Some of the others
(such as multiple pre-rate change notifiers) I won't take in, but we
can discuss more.

Regards,
Mike

>
> Regards
> Richard
Mike Turquette March 11, 2012, 9:24 p.m. | #6
On Sun, Mar 11, 2012 at 4:34 AM, Sascha Hauer <s.hauer@pengutronix.de> wrote:
> Hi Mike,
>
> I was about to give my tested-by when I decided to test the set_rate
> function. Unfortunately this is broken for several reasons. I'll try
> to come up with a fixup series later the day.

I haven't tested clk_set_rate since V4, but I also haven't changed the
code appreciably.  I'll retest on my end also.

> On Fri, Mar 09, 2012 at 11:54:23PM -0800, Mike Turquette wrote:
>> +     /* find the new rate and see if parent rate should change too */
>> +     WARN_ON(!clk->ops->round_rate);
>> +
>> +     new_rate = clk->ops->round_rate(clk->hw, rate, &parent_new_rate);
>
> You don't need a WARN_ON when you derefence clk->ops->round_rate anyway.

Agreed that the WARN_ON should not be there.

The v6 Documentation/clk.txt states that .round_rate is mandatory for
clocks that can adjust their rate, but I need to clarify this a bit
more.  Ideally we want to be able to call clk_set_rate on any clock
and get a changed rate (if possible) by either adjusting that clocks
rate direction (e.g. a PLL or an adjustable divider) or by propagating
__clk_set_rate up the parents (assuming of course that
CLK_SET_RATE_PARENT flag is set appropriately).

> Also, even when the current clock does not have a set_rate function it
> can still change its rate when the CLK_SET_RATE_PARENT is set.

Correct.  I'll clean this up and make the documentation a bit more
verbose on when .set_rate/.round_rate/.recalc_rate are mandatory.

>
>> +
>> +     /* NOTE: pre-rate change notifications will stack */
>> +     if (clk->notifier_count)
>> +             ret = __clk_notify(clk, PRE_RATE_CHANGE, clk->rate, new_rate);
>> +
>> +     if (ret == NOTIFY_BAD)
>> +             return clk;
>> +
>> +     /* speculate rate changes down the tree */
>> +     hlist_for_each_entry(child, tmp, &clk->children, child_node) {
>> +             ret = __clk_speculate_rates(child, new_rate);
>> +             if (ret == NOTIFY_BAD)
>> +                     return clk;
>> +     }
>> +
>> +     /* change the rate of this clk */
>> +     if (clk->ops->set_rate)
>> +             ret = clk->ops->set_rate(clk->hw, new_rate);
>
> I don't know the reason why you change the child clock before the parent
> clock, but it cannot work since this clock will change its rate based on
> the old parent rate and not the new one.

This depends on the .round_rate implementation, which I admit to
having lost some sleep over.  A clever .round_rate will request the
"intermediate" rate for a clock when propagating a request to change
the parent rate later on.  Take for instance the following:

pll @ 200MHz (locked)
    |
parent @ 100MHz (can divide by 1 or 2; currently divider is 2)
    |
child @ 25MHz (can divide by 2 or 4; currently divider is 4)

If we want child to run at 100MHz then the desirable configuration
would be to have parent divide-by-1 and child divide-by-2.  When we
call,

clk_set_rate(child, 100MHz);

Its .round_rate should return 50MHz, and &parent_new_rate should be
200MHz.  So 50MHz is an "intermediate" rate, but it gets us the
divider we want.  And in fact 50MHz reflects reality because that will
be the rate of child until the parent propagation completes and we can
adjust parent's dividers.  (this is one reason why I prefer for
pre-rate change notifiers to stack on top of each other).

So now that &parent_new_rate is > 0, __clk_set_rate will propagate the
request up and parent's .round_rate will simply return 200MHz and
leave it's own &parent_new_rate at 0.  This will change from
divide-by-2 to divide-by-1 and from this highest point in the tree we
will propagate post-rate change notifiers downstream, as part of the
recalc_rate tree walk.

I have tested this with OMAP4's CPUfreq driver and I think, while
complicated, it is a sound way to approach the problem.  Maybe the API
can be cleaned up, if you have any suggestions.

Regards,
Mike

>
> There are more things, as said I'll try to come up with a fixup series.
>
> Sascha
>
> --
> Pengutronix e.K.                           |                             |
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Mike Turquette March 13, 2012, 10:41 p.m. | #7
On Tue, Mar 13, 2012 at 2:48 PM, Rob Herring <robherring2@gmail.com> wrote:
> Mike,
>
> On 03/10/2012 01:54 AM, Mike Turquette wrote:
>> The common clock framework defines a common struct clk useful across
>> most platforms as well as an implementation of the clk api that drivers
>> can use safely for managing clocks.
>>
>> The net result is consolidation of many different struct clk definitions
>> and platform-specific clock framework implementations.
>>
>> This patch introduces the common struct clk, struct clk_ops and an
>> implementation of the well-known clock api in include/clk/clk.h.
>> Platforms may define their own hardware-specific clock structure and
>> their own clock operation callbacks, so long as it wraps an instance of
>> struct clk_hw.
>>
>> See Documentation/clk.txt for more details.
>>
>> This patch is based on the work of Jeremy Kerr, which in turn was based
>> on the work of Ben Herrenschmidt.
>>
>> Signed-off-by: Mike Turquette <mturquette@linaro.org>
>> Signed-off-by: Mike Turquette <mturquette@ti.com>
>> Cc: Russell King <linux@arm.linux.org.uk>
>> Cc: Jeremy Kerr <jeremy.kerr@canonical.com>
>> Cc: Thomas Gleixner <tglx@linutronix.de>
>> Cc: Arnd Bergman <arnd.bergmann@linaro.org>
>> Cc: Paul Walmsley <paul@pwsan.com>
>> Cc: Shawn Guo <shawn.guo@freescale.com>
>> Cc: Sascha Hauer <s.hauer@pengutronix.de>
>> Cc: Richard Zhao <richard.zhao@linaro.org>
>> Cc: Saravana Kannan <skannan@codeaurora.org>
>> Cc: Magnus Damm <magnus.damm@gmail.com>
>> Cc: Rob Herring <rob.herring@calxeda.com>
>> Cc: Mark Brown <broonie@opensource.wolfsonmicro.com>
>> Cc: Linus Walleij <linus.walleij@stericsson.com>
>> Cc: Stephen Boyd <sboyd@codeaurora.org>
>> Cc: Amit Kucheria <amit.kucheria@linaro.org>
>> Cc: Deepak Saxena <dsaxena@linaro.org>
>> Cc: Grant Likely <grant.likely@secretlab.ca>
>> Cc: Andrew Lunn <andrew@lunn.ch>
>
> snip
>
>> +
>> +     /*
>> +      * walk the list of orphan clocks and reparent any that are children of
>> +      * this clock
>> +      */
>> +     hlist_for_each_entry(orphan, tmp, &clk_orphan_list, child_node)
>
> In __clk_init, this needs to be hlist_for_each_entry_safe as entries can
> be removed.

Thanks for the catch Rob.  I'll take this in.

Regards,
Mike

>
> Rob
>
> _______________________________________________
> linaro-dev mailing list
> linaro-dev@lists.linaro.org
> http://lists.linaro.org/mailman/listinfo/linaro-dev

Patch

diff --git a/drivers/clk/Kconfig b/drivers/clk/Kconfig
index 9b3cd08..31ceb27 100644
--- a/drivers/clk/Kconfig
+++ b/drivers/clk/Kconfig
@@ -8,3 +8,42 @@  config HAVE_CLK_PREPARE
 
 config HAVE_MACH_CLKDEV
 	bool
+
+menuconfig COMMON_CLK
+	bool "Common Clock Framework"
+	select HAVE_CLK_PREPARE
+	---help---
+	  The common clock framework is a single definition of struct
+	  clk, useful across many platforms, as well as an
+	  implementation of the clock API in include/linux/clk.h.
+	  Architectures utilizing the common struct clk should select
+	  this automatically, but it may be necessary to manually select
+	  this option for loadable modules requiring the common clock
+	  framework.
+
+	  If in doubt, say "N".
+
+if COMMON_CLK
+
+config COMMON_CLK_DISABLE_UNUSED
+	bool "Disabled unused clocks at boot"
+	depends on COMMON_CLK
+	---help---
+	  Traverses the entire clock tree and disables any clocks that are
+	  enabled in hardware but have not been enabled by any device drivers.
+	  This saves power and keeps the software model of the clock in line
+	  with reality.
+
+	  If in doubt, say "N".
+
+config COMMON_CLK_DEBUG
+	bool "DebugFS representation of clock tree"
+	depends on COMMON_CLK
+	---help---
+	  Creates a directory hierchy in debugfs for visualizing the clk
+	  tree structure.  Each directory contains read-only members
+	  that export information specific to that clk node: clk_rate,
+	  clk_flags, clk_prepare_count, clk_enable_count &
+	  clk_notifier_count.
+
+endif
diff --git a/drivers/clk/Makefile b/drivers/clk/Makefile
index 07613fa..ff362c4 100644
--- a/drivers/clk/Makefile
+++ b/drivers/clk/Makefile
@@ -1,2 +1,3 @@ 
 
 obj-$(CONFIG_CLKDEV_LOOKUP)	+= clkdev.o
+obj-$(CONFIG_COMMON_CLK)	+= clk.o
diff --git a/drivers/clk/clk.c b/drivers/clk/clk.c
new file mode 100644
index 0000000..c7c3bc5
--- /dev/null
+++ b/drivers/clk/clk.c
@@ -0,0 +1,1424 @@ 
+/*
+ * 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; }
+#endif /* CONFIG_COMMON_CLK_DEBUG */
+
+#ifdef CONFIG_COMMON_CLK_DISABLE_UNUSED
+/* 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);
+#else
+static inline int clk_disable_unused(struct clk *clk) { return 0; }
+#endif /* CONFIG_COMMON_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 unsigned long __clk_get_enable_count(struct clk *clk)
+{
+	return !clk ? -EINVAL : clk->enable_count;
+}
+
+inline unsigned long __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) {
+		ret = -EINVAL;
+		goto out;
+	}
+
+	ret = clk->rate;
+
+	if (clk->flags & CLK_IS_ROOT)
+		goto out;
+
+	if (!clk->parent)
+		ret = -ENODEV;
+
+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;
+
+	/* 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);
+
+	if (clk->parent)
+		__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) {
+		if (clk->parent)
+			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
+ * clk is NULL then returns -EINVAL.
+ */
+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)
+{
+	if (!clk && !clk->ops->round_rate)
+		return -EINVAL;
+
+	return clk->ops->round_rate(clk->hw, rate, NULL);
+}
+
+/**
+ * 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 rate passed in is returned.
+ */
+long clk_round_rate(struct clk *clk, unsigned long rate)
+{
+	unsigned long ret = rate;
+
+	mutex_lock(&prepare_lock);
+	if (clk && clk->ops->round_rate)
+		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 operation then
+ * propagation of that subtree stops and all of that clks children will not
+ * have their rates updated.
+ *
+ * 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.
+ *
+ * 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)
+		goto out;
+
+	new_rate = clk->ops->recalc_rate(clk->hw, 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;
+}
+
+/**
+ * DOC: Using the CLK_SET_RATE_PARENT flag
+ *
+ * __clk_set_rate changes the child's rate before the parent's to more
+ * easily handle failure conditions.
+ *
+ * This means clk might run out of spec for a short time if its rate is
+ * increased before the parent's rate is updated.
+ *
+ * To prevent this consider setting the CLK_SET_RATE_GATE flag on any
+ * clk where you also set the CLK_SET_RATE_PARENT flag
+ *
+ * PRE_RATE_CHANGE notifications are supposed to stack as a rate change
+ * request propagates up the clk tree.  This reflects the different
+ * rates that a downstream clk might experience if left enabled while
+ * upstream parents change their rates.
+ */
+static struct clk *__clk_set_rate(struct clk *clk, unsigned long rate)
+{
+	struct clk *fail_clk = NULL;
+	int ret = NOTIFY_DONE;
+	unsigned long old_rate = clk->rate;
+	unsigned long new_rate;
+	unsigned long parent_old_rate;
+	unsigned long parent_new_rate = 0;
+	struct clk *child;
+	struct hlist_node *tmp;
+
+	/* bail early if we can't change rate while clk is enabled */
+	if ((clk->flags & CLK_SET_RATE_GATE) && clk->enable_count)
+		return clk;
+
+	/* find the new rate and see if parent rate should change too */
+	WARN_ON(!clk->ops->round_rate);
+
+	new_rate = clk->ops->round_rate(clk->hw, rate, &parent_new_rate);
+
+	/* NOTE: pre-rate change notifications will stack */
+	if (clk->notifier_count)
+		ret = __clk_notify(clk, PRE_RATE_CHANGE, clk->rate, new_rate);
+
+	if (ret == NOTIFY_BAD)
+		return clk;
+
+	/* speculate rate changes down the tree */
+	hlist_for_each_entry(child, tmp, &clk->children, child_node) {
+		ret = __clk_speculate_rates(child, new_rate);
+		if (ret == NOTIFY_BAD)
+			return clk;
+	}
+
+	/* change the rate of this clk */
+	if (clk->ops->set_rate)
+		ret = clk->ops->set_rate(clk->hw, new_rate);
+
+	if (ret == NOTIFY_BAD)
+		return clk;
+
+	/*
+	 * change the rate of the parent clk if necessary
+	 *
+	 * hitting the nested 'if' path implies we have hit a .set_rate
+	 * failure somewhere upstream while propagating __clk_set_rate
+	 * up the clk tree.  roll back the clk rates one by one and
+	 * return the pointer to the clk that failed.  clk_set_rate will
+	 * use the pointer to propagate a rate-change abort notifier
+	 * from the "highest" point.
+	 */
+	if ((clk->flags & CLK_SET_RATE_PARENT) && parent_new_rate) {
+		parent_old_rate = clk->parent->rate;
+		fail_clk = __clk_set_rate(clk->parent, parent_new_rate);
+
+		/* roll back changes if parent rate change failed */
+		if (fail_clk) {
+			pr_warn("%s: failed to set parent %s rate to %lu\n",
+					__func__, fail_clk->name,
+					parent_new_rate);
+
+			/*
+			 * Send PRE_RATE_CHANGE notifiers down the tree
+			 * again, since we're rolling back the rate
+			 * changes due to the abort.
+			 *
+			 * Ignore any NOTIFY_BAD's since this *is* the
+			 * exception handler.
+			 *
+			 * NOTE: pre-rate change notifications will stack
+			 */
+			__clk_speculate_rates(clk, clk->parent->rate);
+
+			clk->ops->set_rate(clk->hw, old_rate);
+		}
+		return fail_clk;
+	}
+
+	/*
+	 * set clk's rate & recalculate the rates of clk's children
+	 *
+	 * hitting this path implies we have successfully finished
+	 * propagating recursive calls to __clk_set_rate up the clk tree
+	 * (if necessary) and it is safe to propagate __clk_recalc_rates
+	 * and post-rate change notifiers down the clk tree from this
+	 * point.
+	 */
+	__clk_recalc_rates(clk, POST_RATE_CHANGE);
+
+	return NULL;
+}
+
+/**
+ * clk_set_rate - specify a new rate for clk
+ * @clk: the clk whose rate is being changed
+ * @rate: the new rate for clk
+ *
+ * In the simplest case clk_set_rate will only change the rate of clk.
+ *
+ * If clk has the CLK_SET_RATE_GATE flag set and it is enabled this call
+ * will fail; only when the clk is disabled will it be able to change
+ * its rate.
+ *
+ * Setting the CLK_SET_RATE_PARENT flag allows clk_set_rate to
+ * recursively 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 0 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.  If there is a failure during upstream
+ * propagation then clk_set_rate will unwind and restore each clk's rate
+ * that had been successfully changed.  Afterwards a rate change abort
+ * notification will be propagated downstream, starting from the clk
+ * that failed.
+ *
+ * At the end of all of the rate setting, clk_set_rate internally calls
+ * __clk_recalc_rates and propagates the rate changes downstream,
+ * starting from the highest clk whose rate was changed.  This has the
+ * added benefit of propagating post-rate change notifiers.
+ *
+ * Note that while post-rate change and rate change abort notifications
+ * are guaranteed to be sent to a clk only once per call to
+ * clk_set_rate, pre-change notifications will be sent for every clk
+ * whose rate is changed.  Stacking pre-change notifications is noisy
+ * for the drivers subscribed to them, but this allows drivers to react
+ * to intermediate clk rate changes up until the point where the final
+ * rate is achieved at the end of upstream propagation.
+ *
+ * Returns 0 on success, -EERROR otherwise.
+ */
+int clk_set_rate(struct clk *clk, unsigned long rate)
+{
+	struct clk *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;
+
+	fail_clk = __clk_set_rate(clk, rate);
+	if (fail_clk) {
+		pr_warn("%s: failed to set %s rate\n", __func__,
+				fail_clk->name);
+		__clk_recalc_rates(clk, ABORT_RATE_CHANGE);
+		ret = -EIO;
+	}
+
+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.
+ *
+ * Any struct clk passed into __clk_init must have the following members
+ * populated:
+ * 	.name
+ * 	.ops
+ * 	.hw
+ * 	.parent_names
+ * 	.num_parents
+ * 	.flags
+ *
+ * Essentially, everything that would normally be passed into clk_register is
+ * assumed to be initialized already in __clk_init.  The other members may be
+ * populated, but are optional.
+ *
+ * __clk_init 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.
+ */
+void __clk_init(struct device *dev, struct clk *clk)
+{
+	int i;
+	struct clk *orphan;
+	struct hlist_node *tmp;
+
+	if (!clk)
+		return;
+
+	mutex_lock(&prepare_lock);
+
+	/* check to see if a clock with this name is already registered */
+	if (__clk_lookup(clk->name))
+		goto out;
+
+	/*
+	 * 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(orphan, tmp, &clk_orphan_list, child_node)
+		__clk_reparent(orphan, __clk_init_parent(orphan));
+
+	/*
+	 * 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);
+
+	return;
+}
+
+/**
+ * clk_register - allocate a new clock, register it and return an opaque cookie
+ * @dev: device that is registering this clock
+ * @name: clock name
+ * @ops: operations this clock supports
+ * @hw: link to hardware-specific clock data
+ * @parent_names: array of string names for all possible parents
+ * @num_parents: number of possible parents
+ * @flags: framework-level hints and quirks
+ *
+ * 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
+ * rest of the clock API.
+ */
+struct clk *clk_register(struct device *dev, const char *name,
+		const struct clk_ops *ops, struct clk_hw *hw,
+		char **parent_names, u8 num_parents, unsigned long flags)
+{
+	struct clk *clk;
+
+	clk = kzalloc(sizeof(*clk), GFP_KERNEL);
+	if (!clk)
+		return NULL;
+
+	clk->name = name;
+	clk->ops = ops;
+	clk->hw = hw;
+	clk->flags = flags;
+	clk->parent_names = parent_names;
+	clk->num_parents = num_parents;
+	hw->clk = clk;
+
+	__clk_init(dev, clk);
+
+	return clk;
+}
+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.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);
diff --git a/include/linux/clk-private.h b/include/linux/clk-private.h
new file mode 100644
index 0000000..33bf6a7
--- /dev/null
+++ b/include/linux/clk-private.h
@@ -0,0 +1,68 @@ 
+/*
+ *  linux/include/linux/clk-private.h
+ *
+ *  Copyright (c) 2010-2011 Jeremy Kerr <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.
+ */
+#ifndef __LINUX_CLK_PRIVATE_H
+#define __LINUX_CLK_PRIVATE_H
+
+#include <linux/clk-provider.h>
+#include <linux/list.h>
+
+/*
+ * WARNING: Do not include clk-private.h from any file that implements struct
+ * clk_ops.  Doing so is a layering violation!
+ *
+ * This header exists only to allow for statically initialized clock data.  Any
+ * static clock data must be defined in a separate file from the logic that
+ * implements the clock operations for that same data.
+ */
+
+#ifdef CONFIG_COMMON_CLK
+
+struct clk {
+	const char		*name;
+	const struct clk_ops	*ops;
+	struct clk_hw		*hw;
+	struct clk		*parent;
+	char			**parent_names;
+	struct clk		**parents;
+	u8			num_parents;
+	unsigned long		rate;
+	unsigned long		flags;
+	unsigned int		enable_count;
+	unsigned int		prepare_count;
+	struct hlist_head	children;
+	struct hlist_node	child_node;
+	unsigned int		notifier_count;
+#ifdef CONFIG_COMMON_CLK_DEBUG
+	struct dentry		*dentry;
+#endif
+};
+
+/**
+ * __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.
+ *
+ * Any struct clk passed into __clk_init must have the following members
+ * populated:
+ * 	.name
+ * 	.ops
+ * 	.hw
+ * 	.parent_names
+ * 	.num_parents
+ * 	.flags
+ */
+void __clk_init(struct device *dev, struct clk *clk);
+
+#endif /* CONFIG_COMMON_CLK */
+#endif /* CLK_PRIVATE_H */
diff --git a/include/linux/clk-provider.h b/include/linux/clk-provider.h
new file mode 100644
index 0000000..09dea1f
--- /dev/null
+++ b/include/linux/clk-provider.h
@@ -0,0 +1,171 @@ 
+/*
+ *  linux/include/linux/clk-provider.h
+ *
+ *  Copyright (c) 2010-2011 Jeremy Kerr <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.
+ */
+#ifndef __LINUX_CLK_PROVIDER_H
+#define __LINUX_CLK_PROVIDER_H
+
+#include <linux/clk.h>
+
+#ifdef CONFIG_COMMON_CLK
+
+/**
+ * struct clk_hw - handle for traversing from a struct clk to its corresponding
+ * hardware-specific structure.  struct clk_hw should be declared within struct
+ * clk_foo and then referenced by the struct clk instance that uses struct
+ * clk_foo's clk_ops
+ *
+ * clk: pointer to the struct clk instance that points back to this struct
+ * clk_hw instance
+ */
+struct clk_hw {
+	struct clk *clk;
+};
+
+/*
+ * flags used across common struct clk.  these flags should only affect the
+ * top-level framework.  custom flags for dealing with hardware specifics
+ * belong in struct clk_foo
+ */
+#define CLK_SET_RATE_GATE	BIT(0) /* must be gated across rate change */
+#define CLK_SET_PARENT_GATE	BIT(1) /* must be gated across re-parent */
+#define CLK_SET_RATE_PARENT	BIT(2) /* propagate rate change up one level */
+#define CLK_IGNORE_UNUSED	BIT(3) /* do not gate even if unused */
+#define CLK_IS_ROOT		BIT(4) /* root clk, has no parent */
+
+/**
+ * struct clk_ops -  Callback operations for hardware clocks; these are to
+ * be provided by the clock implementation, and will be called by drivers
+ * through the clk_* api.
+ *
+ * @prepare:	Prepare the clock for enabling. This must not return until
+ * 		the clock is fully prepared, and it's safe to call clk_enable.
+ * 		This callback is intended to allow clock implementations to
+ * 		do any initialisation that may sleep. Called with
+ * 		prepare_lock held.
+ *
+ * @unprepare:	Release the clock from its prepared state. This will typically
+ * 		undo any work done in the @prepare callback. Called with
+ * 		prepare_lock held.
+ *
+ * @enable:	Enable the clock atomically. This must not return until the
+ * 		clock is generating a valid clock signal, usable by consumer
+ * 		devices. Called with enable_lock held. This function must not
+ * 		sleep.
+ *
+ * @disable:	Disable the clock atomically. Called with enable_lock held.
+ * 		This function must not sleep.
+ *
+ * @recalc_rate	Recalculate the rate of this clock, by quering hardware.  The
+ * 		parent rate is an input parameter.  It is up to the caller to
+ * 		insure that the prepare_mutex is held across this call.
+ * 		Returns the calculated rate.  Optional, but recommended - if
+ * 		this op is not set then clock rate will be initialized to 0.
+ *
+ * @round_rate:	Given a target rate as input, returns the closest rate actually
+ * 		supported by the clock.
+ *
+ * @get_parent:	Queries the hardware to determine the parent of a clock.  The
+ * 		return value is a u8 which specifies the index corresponding to
+ * 		the parent clock.  This index can be applied to either the
+ * 		.parent_names or .parents arrays.  In short, this function
+ * 		translates the parent value read from hardware into an array
+ * 		index.  Currently only called when the clock is initialized by
+ * 		__clk_init.  This callback is mandatory for clocks with
+ * 		multiple parents.  It is optional (and unnecessary) for clocks
+ * 		with 0 or 1 parents.
+ *
+ * @set_parent:	Change the input source of this clock; for clocks with multiple
+ * 		possible parents specify a new parent by passing in the index
+ * 		as a u8 corresponding to the parent in either the .parent_names
+ * 		or .parents arrays.  This function in affect translates an
+ * 		array index into the value programmed into the hardware.
+ * 		Returns 0 on success, -EERROR otherwise.
+ *
+ * @set_rate:	Change the rate of this clock. If this callback returns
+ * 		CLK_SET_RATE_PARENT, the rate change will be propagated to the
+ * 		parent clock (which may propagate again if the parent clock
+ * 		also sets this flag). The requested rate of the parent is
+ * 		passed back from the callback in the second 'unsigned long *'
+ * 		argument.  Note that it is up to the hardware clock's set_rate
+ * 		implementation to insure that clocks do not run out of spec
+ * 		when propgating the call to set_rate up to the parent.  One way
+ * 		to do this is to gate the clock (via clk_disable and/or
+ * 		clk_unprepare) before calling clk_set_rate, then ungating it
+ * 		afterward.  If your clock also has the CLK_GATE_SET_RATE flag
+ * 		set then this will insure safety.  Returns 0 on success,
+ * 		-EERROR otherwise.
+ *
+ * The clk_enable/clk_disable and clk_prepare/clk_unprepare pairs allow
+ * implementations to split any work between atomic (enable) and sleepable
+ * (prepare) contexts.  If enabling a clock requires code that might sleep,
+ * this must be done in clk_prepare.  Clock enable code that will never be
+ * called in a sleepable context may be implement in clk_enable.
+ *
+ * Typically, drivers will call clk_prepare when a clock may be needed later
+ * (eg. when a device is opened), and clk_enable when the clock is actually
+ * required (eg. from an interrupt). Note that clk_prepare MUST have been
+ * called before clk_enable.
+ */
+struct clk_ops {
+	int		(*prepare)(struct clk_hw *hw);
+	void		(*unprepare)(struct clk_hw *hw);
+	int		(*enable)(struct clk_hw *hw);
+	void		(*disable)(struct clk_hw *hw);
+	int		(*is_enabled)(struct clk_hw *hw);
+	unsigned long	(*recalc_rate)(struct clk_hw *hw,
+					unsigned long parent_rate);
+	long		(*round_rate)(struct clk_hw *hw, unsigned long,
+					unsigned long *);
+	int		(*set_parent)(struct clk_hw *hw, u8 index);
+	u8		(*get_parent)(struct clk_hw *hw);
+	int		(*set_rate)(struct clk_hw *hw, unsigned long);
+	void		(*init)(struct clk_hw *hw);
+};
+
+
+/**
+ * clk_register - allocate a new clock, register it and return an opaque cookie
+ * @dev: device that is registering this clock
+ * @name: clock name
+ * @ops: operations this clock supports
+ * @hw: link to hardware-specific clock data
+ * @parent_names: array of string names for all possible parents
+ * @num_parents: number of possible parents
+ * @flags: framework-level hints and quirks
+ *
+ * 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
+ * rest of the clock API.
+ */
+struct clk *clk_register(struct device *dev, const char *name,
+		const struct clk_ops *ops, struct clk_hw *hw,
+		char **parent_names, u8 num_parents, unsigned long flags);
+
+/* helper functions */
+const char *__clk_get_name(struct clk *clk);
+struct clk_hw *__clk_get_hw(struct clk *clk);
+u8 __clk_get_num_parents(struct clk *clk);
+struct clk *__clk_get_parent(struct clk *clk);
+unsigned long __clk_get_rate(struct clk *clk);
+unsigned long __clk_get_flags(struct clk *clk);
+int __clk_is_enabled(struct clk *clk);
+struct clk *__clk_lookup(const char *name);
+
+/*
+ * FIXME clock api without lock protection
+ */
+int __clk_prepare(struct clk *clk);
+void __clk_unprepare(struct clk *clk);
+void __clk_reparent(struct clk *clk, struct clk *new_parent);
+unsigned long __clk_round_rate(struct clk *clk, unsigned long rate);
+
+#endif /* CONFIG_COMMON_CLK */
+#endif /* CLK_PROVIDER_H */
diff --git a/include/linux/clk.h b/include/linux/clk.h
index b9d46fa..b025272 100644
--- a/include/linux/clk.h
+++ b/include/linux/clk.h
@@ -3,6 +3,7 @@ 
  *
  *  Copyright (C) 2004 ARM Limited.
  *  Written by Deep Blue Solutions Limited.
+ *  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
@@ -12,18 +13,75 @@ 
 #define __LINUX_CLK_H
 
 #include <linux/kernel.h>
+#include <linux/notifier.h>
 
 struct device;
 
-/*
- * The base API.
+struct clk;
+
+#ifdef CONFIG_COMMON_CLK
+
+/**
+ * DOC: clk notifier callback types
+ *
+ * PRE_RATE_CHANGE - called immediately before the clk rate is changed,
+ *     to indicate that the rate change will proceed.  Drivers must
+ *     immediately terminate any operations that will be affected by the
+ *     rate change.  Callbacks may either return NOTIFY_DONE or
+ *     NOTIFY_STOP.
+ *
+ * ABORT_RATE_CHANGE: called if the rate change failed for some reason
+ *     after PRE_RATE_CHANGE.  In this case, all registered notifiers on
+ *     the clk will be called with ABORT_RATE_CHANGE. Callbacks must
+ *     always return NOTIFY_DONE.
+ *
+ * POST_RATE_CHANGE - called after the clk rate change has successfully
+ *     completed.  Callbacks must always return NOTIFY_DONE.
+ *
  */
+#define PRE_RATE_CHANGE			BIT(0)
+#define POST_RATE_CHANGE		BIT(1)
+#define ABORT_RATE_CHANGE		BIT(2)
 
+/**
+ * struct clk_notifier - associate a clk with a notifier
+ * @clk: struct clk * to associate the notifier with
+ * @notifier_head: a blocking_notifier_head for this clk
+ * @node: linked list pointers
+ *
+ * A list of struct clk_notifier is maintained by the notifier code.
+ * An entry is created whenever code registers the first notifier on a
+ * particular @clk.  Future notifiers on that @clk are added to the
+ * @notifier_head.
+ */
+struct clk_notifier {
+	struct clk			*clk;
+	struct srcu_notifier_head	notifier_head;
+	struct list_head		node;
+};
 
-/*
- * struct clk - an machine class defined object / cookie.
+/**
+ * struct clk_notifier_data - rate data to pass to the notifier callback
+ * @clk: struct clk * being changed
+ * @old_rate: previous rate of this clk
+ * @new_rate: new rate of this clk
+ *
+ * For a pre-notifier, old_rate is the clk's rate before this rate
+ * change, and new_rate is what the rate will be in the future.  For a
+ * post-notifier, old_rate and new_rate are both set to the clk's
+ * current rate (this was done to optimize the implementation).
  */
-struct clk;
+struct clk_notifier_data {
+	struct clk		*clk;
+	unsigned long		old_rate;
+	unsigned long		new_rate;
+};
+
+int clk_notifier_register(struct clk *clk, struct notifier_block *nb);
+
+int clk_notifier_unregister(struct clk *clk, struct notifier_block *nb);
+
+#endif /* !CONFIG_COMMON_CLK */
 
 /**
  * clk_get - lookup and obtain a reference to a clock producer.