Merge tag 'common-clk-api' of git://git.kernel.org/pub/scm/linux/kernel/git/arm/arm-soc

Pull "drivers/clk: common clock framework" from Olof Johansson:
 "This branch contains patches from Mike Turquette adding a common clock
  framework to be shared across platforms.  This is part of the work
  towards building a common zImage for several ARM platforms."

* tag 'common-clk-api' of git://git.kernel.org/pub/scm/linux/kernel/git/arm/arm-soc:
  clk: make CONFIG_COMMON_CLK invisible
  clk: basic clock hardware types
  clk: introduce the common clock framework
  Documentation: common clk API

Documentation/clk.txt

+		The Common Clk Framework
+		Mike Turquette <mturquette@ti.com>
+
+This document endeavours to explain the common clk framework details,
+and how to port a platform over to this framework.  It is not yet a
+detailed explanation of the clock api in include/linux/clk.h, but
+perhaps someday it will include that information.
+
+	Part 1 - introduction and interface split
+
+The common clk framework is an interface to control the clock nodes
+available on various devices today.  This may come in the form of clock
+gating, rate adjustment, muxing or other operations.  This framework is
+enabled with the CONFIG_COMMON_CLK option.
+
+The interface itself is divided into two halves, each shielded from the
+details of its counterpart.  First is the common definition of struct
+clk which unifies the framework-level accounting and infrastructure that
+has traditionally been duplicated across a variety of platforms.  Second
+is a common implementation of the clk.h api, defined in
+drivers/clk/clk.c.  Finally there is struct clk_ops, whose operations
+are invoked by the clk api implementation.
+
+The second half of the interface is comprised of the hardware-specific
+callbacks registered with struct clk_ops and the corresponding
+hardware-specific structures needed to model a particular clock.  For
+the remainder of this document any reference to a callback in struct
+clk_ops, such as .enable or .set_rate, implies the hardware-specific
+implementation of that code.  Likewise, references to struct clk_foo
+serve as a convenient shorthand for the implementation of the
+hardware-specific bits for the hypothetical "foo" hardware.
+
+Tying the two halves of this interface together is struct clk_hw, which
+is defined in struct clk_foo and pointed to within struct clk.  This
+allows easy for navigation between the two discrete halves of the common
+clock interface.
+
+	Part 2 - common data structures and api
+
+Below is the common struct clk definition from
+include/linux/clk-private.h, modified for brevity:
+
+	struct clk {
+		const char		*name;
+		const struct clk_ops	*ops;
+		struct clk_hw		*hw;
+		char			**parent_names;
+		struct clk		**parents;
+		struct clk		*parent;
+		struct hlist_head	children;
+		struct hlist_node	child_node;
+		...
+	};
+
+The members above make up the core of the clk tree topology.  The clk
+api itself defines several driver-facing functions which operate on
+struct clk.  That api is documented in include/linux/clk.h.
+
+Platforms and devices utilizing the common struct clk use the struct
+clk_ops pointer in struct clk to perform the hardware-specific parts of
+the operations defined in clk.h:
+
+	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);
+	};
+
+	Part 3 - hardware clk implementations
+
+The strength of the common struct clk comes from its .ops and .hw pointers
+which abstract the details of struct clk from the hardware-specific bits, and
+vice versa.  To illustrate consider the simple gateable clk implementation in
+drivers/clk/clk-gate.c:
+
+struct clk_gate {
+	struct clk_hw	hw;
+	void __iomem    *reg;
+	u8              bit_idx;
+	...
+};
+
+struct clk_gate contains struct clk_hw hw as well as hardware-specific
+knowledge about which register and bit controls this clk's gating.
+Nothing about clock topology or accounting, such as enable_count or
+notifier_count, is needed here.  That is all handled by the common
+framework code and struct clk.
+
+Let's walk through enabling this clk from driver code:
+
+	struct clk *clk;
+	clk = clk_get(NULL, "my_gateable_clk");
+
+	clk_prepare(clk);
+	clk_enable(clk);
+
+The call graph for clk_enable is very simple:
+
+clk_enable(clk);
+	clk->ops->enable(clk->hw);
+	[resolves to...]
+		clk_gate_enable(hw);
+		[resolves struct clk gate with to_clk_gate(hw)]
+			clk_gate_set_bit(gate);
+
+And the definition of clk_gate_set_bit:
+
+static void clk_gate_set_bit(struct clk_gate *gate)
+{
+	u32 reg;
+
+	reg = __raw_readl(gate->reg);
+	reg |= BIT(gate->bit_idx);
+	writel(reg, gate->reg);
+}
+
+Note that to_clk_gate is defined as:
+
+#define to_clk_gate(_hw) container_of(_hw, struct clk_gate, clk)
+
+This pattern of abstraction is used for every clock hardware
+representation.
+
+	Part 4 - supporting your own clk hardware
+
+When implementing support for a new type of clock it only necessary to
+include the following header:
+
+#include <linux/clk-provider.h>
+
+include/linux/clk.h is included within that header and clk-private.h
+must never be included from the code which implements the operations for
+a clock.  More on that below in Part 5.
+
+To construct a clk hardware structure for your platform you must define
+the following:
+
+struct clk_foo {
+	struct clk_hw hw;
+	... hardware specific data goes here ...
+};
+
+To take advantage of your data you'll need to support valid operations
+for your clk:
+
+struct clk_ops clk_foo_ops {
+	.enable		= &clk_foo_enable;
+	.disable	= &clk_foo_disable;
+};
+
+Implement the above functions using container_of:
+
+#define to_clk_foo(_hw) container_of(_hw, struct clk_foo, hw)
+
+int clk_foo_enable(struct clk_hw *hw)
+{
+	struct clk_foo *foo;
+
+	foo = to_clk_foo(hw);
+
+	... perform magic on foo ...
+
+	return 0;
+};
+
+Below is a matrix detailing which clk_ops are mandatory based upon the
+hardware capbilities of that clock.  A cell marked as "y" means
+mandatory, a cell marked as "n" implies that either including that
+callback is invalid or otherwise uneccesary.  Empty cells are either
+optional or must be evaluated on a case-by-case basis.
+
+                           clock hardware characteristics
+	     -----------------------------------------------------------
+             | gate | change rate | single parent | multiplexer | root |
+             |------|-------------|---------------|-------------|------|
+.prepare     |      |             |               |             |      |
+.unprepare   |      |             |               |             |      |
+             |      |             |               |             |      |
+.enable      | y    |             |               |             |      |
+.disable     | y    |             |               |             |      |
+.is_enabled  | y    |             |               |             |      |
+             |      |             |               |             |      |
+.recalc_rate |      | y           |               |             |      |
+.round_rate  |      | y           |               |             |      |
+.set_rate    |      | y           |               |             |      |
+             |      |             |               |             |      |
+.set_parent  |      |             | n             | y           | n    |
+.get_parent  |      |             | n             | y           | n    |
+             |      |             |               |             |      |
+.init        |      |             |               |             |      |
+	     -----------------------------------------------------------
+
+Finally, register your clock at run-time with a hardware-specific
+registration function.  This function simply populates struct clk_foo's
+data and then passes the common struct clk parameters to the framework
+with a call to:
+
+clk_register(...)
+
+See the basic clock types in drivers/clk/clk-*.c for examples.
+
+	Part 5 - static initialization of clock data
+
+For platforms with many clocks (often numbering into the hundreds) it
+may be desirable to statically initialize some clock data.  This
+presents a problem since the definition of struct clk should be hidden
+from everyone except for the clock core in drivers/clk/clk.c.
+
+To get around this problem struct clk's definition is exposed in
+include/linux/clk-private.h along with some macros for more easily
+initializing instances of the basic clock types.  These clocks must
+still be initialized with the common clock framework via a call to
+__clk_init.
+
+clk-private.h must NEVER be included by code which implements struct
+clk_ops callbacks, nor must it be included by any logic which pokes
+around inside of struct clk at run-time.  To do so is a layering
+violation.
+
+To better enforce this policy, always follow this simple rule: any
+statically initialized clock data MUST be defined in a separate file
+from the logic that implements its ops.  Basically separate the logic
+from the data and all is well.

drivers/clk/Kconfig

@@ -8,3 +8,40 @@ config HAVE_CLK_PREPARE
 
 config HAVE_MACH_CLKDEV
 	bool
+
+config COMMON_CLK
+	bool
+	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 option.
+
+menu "Common Clock Framework"
+	depends on 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
+	select DEBUG_FS
+	---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.
+
+endmenu

drivers/clk/Makefile

 
 obj-$(CONFIG_CLKDEV_LOOKUP)	+= clkdev.o
+obj-$(CONFIG_COMMON_CLK)	+= clk.o clk-fixed-rate.o clk-gate.o \
+				   clk-mux.o clk-divider.o

drivers/clk/clk-divider.c

+/*
+ * Copyright (C) 2011 Sascha Hauer, Pengutronix <s.hauer@pengutronix.de>
+ * Copyright (C) 2011 Richard Zhao, Linaro <richard.zhao@linaro.org>
+ * Copyright (C) 2011-2012 Mike Turquette, 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.
+ *
+ * Adjustable divider clock implementation
+ */
+
+#include <linux/clk-provider.h>
+#include <linux/module.h>
+#include <linux/slab.h>
+#include <linux/io.h>
+#include <linux/err.h>
+#include <linux/string.h>
+
+/*
+ * DOC: basic adjustable divider clock that cannot gate
+ *
+ * Traits of this clock:
+ * prepare - clk_prepare only ensures that parents are prepared
+ * enable - clk_enable only ensures that parents are enabled
+ * rate - rate is adjustable.  clk->rate = parent->rate / divisor
+ * parent - fixed parent.  No clk_set_parent support
+ */
+
+#define to_clk_divider(_hw) container_of(_hw, struct clk_divider, hw)
+
+#define div_mask(d)	((1 << (d->width)) - 1)
+
+static unsigned long clk_divider_recalc_rate(struct clk_hw *hw,
+		unsigned long parent_rate)
+{
+	struct clk_divider *divider = to_clk_divider(hw);
+	unsigned int div;
+
+	div = readl(divider->reg) >> divider->shift;
+	div &= div_mask(divider);
+
+	if (!(divider->flags & CLK_DIVIDER_ONE_BASED))
+		div++;
+
+	return parent_rate / div;
+}
+EXPORT_SYMBOL_GPL(clk_divider_recalc_rate);
+
+/*
+ * The reverse of DIV_ROUND_UP: The maximum number which
+ * divided by m is r
+ */
+#define MULT_ROUND_UP(r, m) ((r) * (m) + (m) - 1)
+
+static int clk_divider_bestdiv(struct clk_hw *hw, unsigned long rate,
+		unsigned long *best_parent_rate)
+{
+	struct clk_divider *divider = to_clk_divider(hw);
+	int i, bestdiv = 0;
+	unsigned long parent_rate, best = 0, now, maxdiv;
+
+	if (!rate)
+		rate = 1;
+
+	maxdiv = (1 << divider->width);
+
+	if (divider->flags & CLK_DIVIDER_ONE_BASED)
+		maxdiv--;
+
+	if (!best_parent_rate) {
+		parent_rate = __clk_get_rate(__clk_get_parent(hw->clk));
+		bestdiv = DIV_ROUND_UP(parent_rate, rate);
+		bestdiv = bestdiv == 0 ? 1 : bestdiv;
+		bestdiv = bestdiv > maxdiv ? maxdiv : bestdiv;
+		return bestdiv;
+	}
+
+	/*
+	 * The maximum divider we can use without overflowing
+	 * unsigned long in rate * i below
+	 */
+	maxdiv = min(ULONG_MAX / rate, maxdiv);
+
+	for (i = 1; i <= maxdiv; i++) {
+		parent_rate = __clk_round_rate(__clk_get_parent(hw->clk),
+				MULT_ROUND_UP(rate, i));
+		now = parent_rate / i;
+		if (now <= rate && now > best) {
+			bestdiv = i;
+			best = now;
+			*best_parent_rate = parent_rate;
+		}
+	}
+
+	if (!bestdiv) {
+		bestdiv = (1 << divider->width);
+		if (divider->flags & CLK_DIVIDER_ONE_BASED)
+			bestdiv--;
+		*best_parent_rate = __clk_round_rate(__clk_get_parent(hw->clk), 1);
+	}
+
+	return bestdiv;
+}
+
+static long clk_divider_round_rate(struct clk_hw *hw, unsigned long rate,
+				unsigned long *prate)
+{
+	int div;
+	div = clk_divider_bestdiv(hw, rate, prate);
+
+	if (prate)
+		return *prate / div;
+	else {
+		unsigned long r;
+		r = __clk_get_rate(__clk_get_parent(hw->clk));
+		return r / div;
+	}
+}
+EXPORT_SYMBOL_GPL(clk_divider_round_rate);
+
+static int clk_divider_set_rate(struct clk_hw *hw, unsigned long rate)
+{
+	struct clk_divider *divider = to_clk_divider(hw);
+	unsigned int div;
+	unsigned long flags = 0;
+	u32 val;
+
+	div = __clk_get_rate(__clk_get_parent(hw->clk)) / rate;
+
+	if (!(divider->flags & CLK_DIVIDER_ONE_BASED))
+		div--;
+
+	if (div > div_mask(divider))
+		div = div_mask(divider);
+
+	if (divider->lock)
+		spin_lock_irqsave(divider->lock, flags);
+
+	val = readl(divider->reg);
+	val &= ~(div_mask(divider) << divider->shift);
+	val |= div << divider->shift;
+	writel(val, divider->reg);
+
+	if (divider->lock)
+		spin_unlock_irqrestore(divider->lock, flags);
+
+	return 0;
+}
+EXPORT_SYMBOL_GPL(clk_divider_set_rate);
+
+struct clk_ops clk_divider_ops = {
+	.recalc_rate = clk_divider_recalc_rate,
+	.round_rate = clk_divider_round_rate,
+	.set_rate = clk_divider_set_rate,
+};
+EXPORT_SYMBOL_GPL(clk_divider_ops);
+
+struct clk *clk_register_divider(struct device *dev, const char *name,
+		const char *parent_name, unsigned long flags,
+		void __iomem *reg, u8 shift, u8 width,
+		u8 clk_divider_flags, spinlock_t *lock)
+{
+	struct clk_divider *div;
+	struct clk *clk;
+
+	div = kzalloc(sizeof(struct clk_divider), GFP_KERNEL);
+
+	if (!div) {
+		pr_err("%s: could not allocate divider clk\n", __func__);
+		return NULL;
+	}
+
+	/* struct clk_divider assignments */
+	div->reg = reg;
+	div->shift = shift;
+	div->width = width;
+	div->flags = clk_divider_flags;
+	div->lock = lock;
+
+	if (parent_name) {
+		div->parent[0] = kstrdup(parent_name, GFP_KERNEL);
+		if (!div->parent[0])
+			goto out;
+	}
+
+	clk = clk_register(dev, name,
+			&clk_divider_ops, &div->hw,
+			div->parent,
+			(parent_name ? 1 : 0),
+			flags);
+	if (clk)
+		return clk;
+
+out:
+	kfree(div->parent[0]);
+	kfree(div);
+
+	return NULL;
+}

drivers/clk/clk-fixed-rate.c

+/*
+ * Copyright (C) 2010-2011 Canonical Ltd <jeremy.kerr@canonical.com>
+ * Copyright (C) 2011-2012 Mike Turquette, 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.
+ *
+ * Fixed rate clock implementation
+ */
+
+#include <linux/clk-provider.h>
+#include <linux/module.h>
+#include <linux/slab.h>
+#include <linux/io.h>
+#include <linux/err.h>
+
+/*
+ * DOC: basic fixed-rate clock that cannot gate
+ *
+ * Traits of this clock:
+ * prepare - clk_(un)prepare only ensures parents are prepared
+ * enable - clk_enable only ensures parents are enabled
+ * rate - rate is always a fixed value.  No clk_set_rate support
+ * parent - fixed parent.  No clk_set_parent support
+ */
+
+#define to_clk_fixed_rate(_hw) container_of(_hw, struct clk_fixed_rate, hw)
+
+static unsigned long clk_fixed_rate_recalc_rate(struct clk_hw *hw,
+		unsigned long parent_rate)
+{
+	return to_clk_fixed_rate(hw)->fixed_rate;
+}
+EXPORT_SYMBOL_GPL(clk_fixed_rate_recalc_rate);
+
+struct clk_ops clk_fixed_rate_ops = {
+	.recalc_rate = clk_fixed_rate_recalc_rate,
+};
+EXPORT_SYMBOL_GPL(clk_fixed_rate_ops);
+
+struct clk *clk_register_fixed_rate(struct device *dev, const char *name,
+		const char *parent_name, unsigned long flags,
+		unsigned long fixed_rate)
+{
+	struct clk_fixed_rate *fixed;
+	char **parent_names = NULL;
+	u8 len;
+
+	fixed = kzalloc(sizeof(struct clk_fixed_rate), GFP_KERNEL);
+
+	if (!fixed) {
+		pr_err("%s: could not allocate fixed clk\n", __func__);
+		return ERR_PTR(-ENOMEM);
+	}
+
+	/* struct clk_fixed_rate assignments */
+	fixed->fixed_rate = fixed_rate;
+
+	if (parent_name) {
+		parent_names = kmalloc(sizeof(char *), GFP_KERNEL);
+
+		if (! parent_names)
+			goto out;
+
+		len = sizeof(char) * strlen(parent_name);
+
+		parent_names[0] = kmalloc(len, GFP_KERNEL);
+
+		if (!parent_names[0])
+			goto out;
+
+		strncpy(parent_names[0], parent_name, len);
+	}
+
+out:
+	return clk_register(dev, name,
+			&clk_fixed_rate_ops, &fixed->hw,
+			parent_names,
+			(parent_name ? 1 : 0),
+			flags);
+}

drivers/clk/clk-gate.c

+/*
+ * Copyright (C) 2010-2011 Canonical Ltd <jeremy.kerr@canonical.com>
+ * Copyright (C) 2011-2012 Mike Turquette, 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.
+ *
+ * Gated clock implementation
+ */
+
+#include <linux/clk-provider.h>
+#include <linux/module.h>
+#include <linux/slab.h>
+#include <linux/io.h>
+#include <linux/err.h>
+#include <linux/string.h>
+
+/**
+ * DOC: basic gatable clock which can gate and ungate it's ouput
+ *
+ * Traits of this clock:
+ * prepare - clk_(un)prepare only ensures parent is (un)prepared
+ * enable - clk_enable and clk_disable are functional & control gating
+ * rate - inherits rate from parent.  No clk_set_rate support
+ * parent - fixed parent.  No clk_set_parent support
+ */
+
+#define to_clk_gate(_hw) container_of(_hw, struct clk_gate, hw)
+
+static void clk_gate_set_bit(struct clk_gate *gate)
+{
+	u32 reg;
+	unsigned long flags = 0;
+
+	if (gate->lock)
+		spin_lock_irqsave(gate->lock, flags);
+
+	reg = readl(gate->reg);
+	reg |= BIT(gate->bit_idx);
+	writel(reg, gate->reg);
+
+	if (gate->lock)
+		spin_unlock_irqrestore(gate->lock, flags);
+}
+
+static void clk_gate_clear_bit(struct clk_gate *gate)
+{
+	u32 reg;
+	unsigned long flags = 0;
+
+	if (gate->lock)
+		spin_lock_irqsave(gate->lock, flags);
+
+	reg = readl(gate->reg);
+	reg &= ~BIT(gate->bit_idx);
+	writel(reg, gate->reg);
+
+	if (gate->lock)
+		spin_unlock_irqrestore(gate->lock, flags);
+}
+
+static int clk_gate_enable(struct clk_hw *hw)
+{
+	struct clk_gate *gate = to_clk_gate(hw);
+
+	if (gate->flags & CLK_GATE_SET_TO_DISABLE)
+		clk_gate_clear_bit(gate);
+	else
+		clk_gate_set_bit(gate);
+
+	return 0;
+}
+EXPORT_SYMBOL_GPL(clk_gate_enable);
+
+static void clk_gate_disable(struct clk_hw *hw)
+{
+	struct clk_gate *gate = to_clk_gate(hw);
+
+	if (gate->flags & CLK_GATE_SET_TO_DISABLE)
+		clk_gate_set_bit(gate);
+	else
+		clk_gate_clear_bit(gate);
+}
+EXPORT_SYMBOL_GPL(clk_gate_disable);
+
+static int clk_gate_is_enabled(struct clk_hw *hw)
+{
+	u32 reg;
+	struct clk_gate *gate = to_clk_gate(hw);
+
+	reg = readl(gate->reg);
+
+	/* if a set bit disables this clk, flip it before masking */
+	if (gate->flags & CLK_GATE_SET_TO_DISABLE)
+		reg ^= BIT(gate->bit_idx);
+
+	reg &= BIT(gate->bit_idx);
+
+	return reg ? 1 : 0;
+}
+EXPORT_SYMBOL_GPL(clk_gate_is_enabled);
+
+struct clk_ops clk_gate_ops = {
+	.enable = clk_gate_enable,
+	.disable = clk_gate_disable,
+	.is_enabled = clk_gate_is_enabled,
+};
+EXPORT_SYMBOL_GPL(clk_gate_ops);
+
+struct clk *clk_register_gate(struct device *dev, const char *name,
+		const char *parent_name, unsigned long flags,
+		void __iomem *reg, u8 bit_idx,
+		u8 clk_gate_flags, spinlock_t *lock)
+{
+	struct clk_gate *gate;
+	struct clk *clk;
+
+	gate = kzalloc(sizeof(struct clk_gate), GFP_KERNEL);
+
+	if (!gate) {
+		pr_err("%s: could not allocate gated clk\n", __func__);
+		return NULL;
+	}
+
+	/* struct clk_gate assignments */
+	gate->reg = reg;
+	gate->bit_idx = bit_idx;
+	gate->flags = clk_gate_flags;
+	gate->lock = lock;
+
+	if (parent_name) {
+		gate->parent[0] = kstrdup(parent_name, GFP_KERNEL);
+		if (!gate->parent[0])
+			goto out;
+	}
+
+	clk = clk_register(dev, name,
+			&clk_gate_ops, &gate->hw,
+			gate->parent,
+			(parent_name ? 1 : 0),
+			flags);
+	if (clk)
+		return clk;
+out:
+	kfree(gate->parent[0]);
+	kfree(gate);
+
+	return NULL;
+}

drivers/clk/clk-mux.c

+/*
+ * Copyright (C) 2011 Sascha Hauer, Pengutronix <s.hauer@pengutronix.de>
+ * Copyright (C) 2011 Richard Zhao, Linaro <richard.zhao@linaro.org>
+ * Copyright (C) 2011-2012 Mike Turquette, 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.
+ *
+ * Simple multiplexer clock implementation
+ */
+
+#include <linux/clk.h>
+#include <linux/clk-provider.h>
+#include <linux/module.h>
+#include <linux/slab.h>
+#include <linux/io.h>
+#include <linux/err.h>
+
+/*
+ * DOC: basic adjustable multiplexer clock that cannot gate
+ *
+ * Traits of this clock:
+ * prepare - clk_prepare only ensures that parents are prepared
+ * enable - clk_enable only ensures that parents are enabled
+ * rate - rate is only affected by parent switching.  No clk_set_rate support
+ * parent - parent is adjustable through clk_set_parent
+ */
+
+#define to_clk_mux(_hw) container_of(_hw, struct clk_mux, hw)
+
+static u8 clk_mux_get_parent(struct clk_hw *hw)
+{
+	struct clk_mux *mux = to_clk_mux(hw);
+	u32 val;
+
+	/*
+	 * FIXME need a mux-specific flag to determine if val is bitwise or numeric
+	 * e.g. sys_clkin_ck's clksel field is 3 bits wide, but ranges from 0x1
+	 * to 0x7 (index starts at one)
+	 * OTOH, pmd_trace_clk_mux_ck uses a separate bit for each clock, so
+	 * val = 0x4 really means "bit 2, index starts at bit 0"
+	 */
+	val = readl(mux->reg) >> mux->shift;
+	val &= (1 << mux->width) - 1;
+
+	if (val && (mux->flags & CLK_MUX_INDEX_BIT))
+		val = ffs(val) - 1;
+
+	if (val && (mux->flags & CLK_MUX_INDEX_ONE))
+		val--;
+
+	if (val >= __clk_get_num_parents(hw->clk))
+		return -EINVAL;
+
+	return val;
+}
+EXPORT_SYMBOL_GPL(clk_mux_get_parent);
+
+static int clk_mux_set_parent(struct clk_hw *hw, u8 index)
+{
+	struct clk_mux *mux = to_clk_mux(hw);
+	u32 val;
+	unsigned long flags = 0;
+
+	if (mux->flags & CLK_MUX_INDEX_BIT)
+		index = (1 << ffs(index));
+
+	if (mux->flags & CLK_MUX_INDEX_ONE)
+		index++;
+
+	if (mux->lock)
+		spin_lock_irqsave(mux->lock, flags);
+
+	val = readl(mux->reg);
+	val &= ~(((1 << mux->width) - 1) << mux->shift);
+	val |= index << mux->shift;
+	writel(val, mux->reg);
+
+	if (mux->lock)
+		spin_unlock_irqrestore(mux->lock, flags);
+
+	return 0;
+}
+EXPORT_SYMBOL_GPL(clk_mux_set_parent);
+
+struct clk_ops clk_mux_ops = {
+	.get_parent = clk_mux_get_parent,
+	.set_parent = clk_mux_set_parent,
+};
+EXPORT_SYMBOL_GPL(clk_mux_ops);
+
+struct clk *clk_register_mux(struct device *dev, const char *name,
+		char **parent_names, u8 num_parents, unsigned long flags,
+		void __iomem *reg, u8 shift, u8 width,
+		u8 clk_mux_flags, spinlock_t *lock)
+{
+	struct clk_mux *mux;
+
+	mux = kmalloc(sizeof(struct clk_mux), GFP_KERNEL);
+
+	if (!mux) {
+		pr_err("%s: could not allocate mux clk\n", __func__);
+		return ERR_PTR(-ENOMEM);
+	}
+
+	/* struct clk_mux assignments */
+	mux->reg = reg;
+	mux->shift = shift;
+	mux->width = width;
+	mux->flags = clk_mux_flags;
+	mux->lock = lock;
+
+	return clk_register(dev, name, &clk_mux_ops, &mux->hw,
+			parent_names, num_parents, flags);
+}

drivers/clk/clk.c

+/*
+ * 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 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) {
+		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;
+
+	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
+ * 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)
+{
+	unsigned long unused;
+
+	if (!clk)
+		return -EINVAL;
+
+	if (!clk->ops->round_rate)
+		return clk->rate;
+
+	if (clk->flags & CLK_SET_RATE_PARENT)
+		return clk->ops->round_rate(clk->hw, rate, &unused);
+	else
+		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 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;
+	unsigned long best_parent_rate = clk->parent->rate;
+	unsigned long new_rate;
+
+	if (!clk->ops->round_rate && !(clk->flags & CLK_SET_RATE_PARENT)) {
+		clk->new_rate = clk->rate;
+		return NULL;
+	}
+
+	if (!clk->ops->round_rate && (clk->flags & CLK_SET_RATE_PARENT)) {
+		top = clk_calc_new_rates(clk->parent, rate);
+		new_rate = clk->new_rate = clk->parent->new_rate;
+
+		goto out;
+	}
+
+	if (clk->flags & CLK_SET_RATE_PARENT)
+		new_rate = clk->ops->round_rate(clk->hw, rate, &best_parent_rate);
+	else
+		new_rate = clk->ops->round_rate(clk->hw, rate, NULL);
+
+	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)
+		clk->ops->set_rate(clk->hw, clk->new_rate);
+
+	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
+ *
+ * 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 *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;
+
+	/* 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.
+ *
+ * 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, *tmp2;
+
+	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;
+
+	/* 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);
+
+	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_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);

include/linux/clk-private.h

+/*
+ *  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		new_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
+};
+
+/*
+ * DOC: Basic clock implementations common to many platforms
+ *
+ * Each basic clock hardware type is comprised of a structure describing the
+ * clock hardware, implementations of the relevant callbacks in struct clk_ops,
+ * unique flags for that hardware type, a registration function and an
+ * alternative macro for static initialization
+ */
+
+extern struct clk_ops clk_fixed_rate_ops;
+
+#define DEFINE_CLK_FIXED_RATE(_name, _flags, _rate,		\
+				_fixed_rate_flags)		\
+	static struct clk _name;				\
+	static char *_name##_parent_names[] = {};		\
+	static struct clk_fixed_rate _name##_hw = {		\
+		.hw = {						\
+			.clk = &_name,				\
+		},						\
+		.fixed_rate = _rate,				\
+		.flags = _fixed_rate_flags,			\
+	};							\
+	static struct clk _name = {				\
+		.name = #_name,					\
+		.ops = &clk_fixed_rate_ops,			\
+		.hw = &_name##_hw.hw,				\
+		.parent_names = _name##_parent_names,		\
+		.num_parents =					\
+			ARRAY_SIZE(_name##_parent_names),	\
+		.flags = _flags,				\
+	};
+
+extern struct clk_ops clk_gate_ops;
+
+#define DEFINE_CLK_GATE(_name, _parent_name, _parent_ptr,	\
+				_flags, _reg, _bit_idx,		\
+				_gate_flags, _lock)		\
+	static struct clk _name;				\
+	static char *_name##_parent_names[] = {			\
+		_parent_name,					\
+	};							\
+	static struct clk *_name##_parents[] = {		\
+		_parent_ptr,					\
+	};							\
+	static struct clk_gate _name##_hw = {			\
+		.hw = {						\
+			.clk = &_name,				\
+		},						\
+		.reg = _reg,					\
+		.bit_idx = _bit_idx,				\
+		.flags = _gate_flags,				\
+		.lock = _lock,					\
+	};							\
+	static struct clk _name = {				\
+		.name = #_name,					\
+		.ops = &clk_gate_ops,				\
+		.hw = &_name##_hw.hw,				\
+		.parent_names = _name##_parent_names,		\
+		.num_parents =					\
+			ARRAY_SIZE(_name##_parent_names),	\
+		.parents = _name##_parents,			\
+		.flags = _flags,				\
+	};
+
+extern struct clk_ops clk_divider_ops;
+
+#define DEFINE_CLK_DIVIDER(_name, _parent_name, _parent_ptr,	\
+				_flags, _reg, _shift, _width,	\
+				_divider_flags, _lock)		\
+	static struct clk _name;				\
+	static char *_name##_parent_names[] = {			\
+		_parent_name,					\
+	};							\
+	static struct clk *_name##_parents[] = {		\
+		_parent_ptr,					\
+	};							\
+	static struct clk_divider _name##_hw = {		\
+		.hw = {						\
+			.clk = &_name,				\
+		},						\
+		.reg = _reg,					\
+		.shift = _shift,				\
+		.width = _width,				\
+		.flags = _divider_flags,			\
+		.lock = _lock,					\
+	};							\
+	static struct clk _name = {				\
+		.name = #_name,					\
+		.ops = &clk_divider_ops,			\
+		.hw = &_name##_hw.hw,				\
+		.parent_names = _name##_parent_names,		\
+		.num_parents =					\
+			ARRAY_SIZE(_name##_parent_names),	\
+		.parents = _name##_parents,			\
+		.flags = _flags,				\
+	};
+
+extern struct clk_ops clk_mux_ops;
+
+#define DEFINE_CLK_MUX(_name, _parent_names, _parents, _flags,	\
+				_reg, _shift, _width,		\
+				_mux_flags, _lock)		\
+	static struct clk _name;				\
+	static struct clk_mux _name##_hw = {			\
+		.hw = {						\
+			.clk = &_name,				\
+		},						\
+		.reg = _reg,					\
+		.shift = _shift,				\
+		.width = _width,				\
+		.flags = _mux_flags,				\
+		.lock = _lock,					\
+	};							\
+	static struct clk _name = {				\
+		.name = #_name,					\
+		.ops = &clk_mux_ops,				\
+		.hw = &_name##_hw.hw,				\
+		.parent_names = _parent_names,			\
+		.num_parents =					\
+			ARRAY_SIZE(_parent_names),		\
+		.parents = _parents,				\
+		.flags = _flags,				\
+	};
+
+/**
+ * __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
+ *
+ * It is not necessary to call clk_register if __clk_init is used directly with
+ * statically initialized clock data.
+ */
+void __clk_init(struct device *dev, struct clk *clk);
+
+#endif /* CONFIG_COMMON_CLK */
+#endif /* CLK_PRIVATE_H */

include/linux/clk-provider.h

+/*
+ *  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);
+};
+
+/*
+ * DOC: Basic clock implementations common to many platforms
+ *
+ * Each basic clock hardware type is comprised of a structure describing the
+ * clock hardware, implementations of the relevant callbacks in struct clk_ops,
+ * unique flags for that hardware type, a registration function and an
+ * alternative macro for static initialization
+ */
+
+/**
+ * struct clk_fixed_rate - fixed-rate clock
+ * @hw:		handle between common and hardware-specific interfaces
+ * @fixed_rate:	constant frequency of clock
+ */
+struct clk_fixed_rate {
+	struct		clk_hw hw;
+	unsigned long	fixed_rate;
+	u8		flags;
+};
+
+struct clk *clk_register_fixed_rate(struct device *dev, const char *name,
+		const char *parent_name, unsigned long flags,
+		unsigned long fixed_rate);
+
+/**
+ * struct clk_gate - gating clock
+ *
+ * @hw:		handle between common and hardware-specific interfaces
+ * @reg:	register controlling gate
+ * @bit_idx:	single bit controlling gate
+ * @flags:	hardware-specific flags
+ * @lock:	register lock
+ *
+ * Clock which can gate its output.  Implements .enable & .disable
+ *
+ * Flags:
+ * CLK_GATE_SET_DISABLE - by default this clock sets the bit at bit_idx to
+ * 	enable the clock.  Setting this flag does the opposite: setting the bit
+ * 	disable the clock and clearing it enables the clock
+ */
+struct clk_gate {
+	struct clk_hw hw;
+	void __iomem	*reg;
+	u8		bit_idx;
+	u8		flags;
+	spinlock_t	*lock;
+	char		*parent[1];
+};
+
+#define CLK_GATE_SET_TO_DISABLE		BIT(0)
+
+struct clk *clk_register_gate(struct device *dev, const char *name,
+		const char *parent_name, unsigned long flags,
+		void __iomem *reg, u8 bit_idx,
+		u8 clk_gate_flags, spinlock_t *lock);
+
+/**
+ * struct clk_divider - adjustable divider clock
+ *
+ * @hw:		handle between common and hardware-specific interfaces
+ * @reg:	register containing the divider
+ * @shift:	shift to the divider bit field
+ * @width:	width of the divider bit field
+ * @lock:	register lock
+ *
+ * Clock with an adjustable divider affecting its output frequency.  Implements
+ * .recalc_rate, .set_rate and .round_rate
+ *
+ * Flags:
+ * CLK_DIVIDER_ONE_BASED - by default the divisor is the value read from the
+ * 	register plus one.  If CLK_DIVIDER_ONE_BASED is set then the divider is
+ * 	the raw value read from the register, with the value of zero considered
+ * 	invalid
+ * CLK_DIVIDER_POWER_OF_TWO - clock divisor is 2 raised to the value read from
+ * 	the hardware register
+ */
+struct clk_divider {
+	struct clk_hw	hw;
+	void __iomem	*reg;
+	u8		shift;
+	u8		width;
+	u8		flags;
+	spinlock_t	*lock;
+	char		*parent[1];
+};
+
+#define CLK_DIVIDER_ONE_BASED		BIT(0)
+#define CLK_DIVIDER_POWER_OF_TWO	BIT(1)
+
+struct clk *clk_register_divider(struct device *dev, const char *name,
+		const char *parent_name, unsigned long flags,
+		void __iomem *reg, u8 shift, u8 width,
+		u8 clk_divider_flags, spinlock_t *lock);
+
+/**
+ * struct clk_mux - multiplexer clock
+ *
+ * @hw:		handle between common and hardware-specific interfaces
+ * @reg:	register controlling multiplexer
+ * @shift:	shift to multiplexer bit field
+ * @width:	width of mutliplexer bit field
+ * @num_clks:	number of parent clocks
+ * @lock:	register lock
+ *
+ * Clock with multiple selectable parents.  Implements .get_parent, .set_parent
+ * and .recalc_rate
+ *
+ * Flags:
+ * CLK_MUX_INDEX_ONE - register index starts at 1, not 0
+ * CLK_MUX_INDEX_BITWISE - register index is a single bit (power of two)
+ */
+struct clk_mux {
+	struct clk_hw	hw;
+	void __iomem	*reg;
+	u8		shift;
+	u8		width;
+	u8		flags;
+	spinlock_t	*lock;
+};
+
+#define CLK_MUX_INDEX_ONE		BIT(0)
+#define CLK_MUX_INDEX_BIT		BIT(1)
+
+struct clk *clk_register_mux(struct device *dev, const char *name,
+		char **parent_names, u8 num_parents, unsigned long flags,
+		void __iomem *reg, u8 shift, u8 width,
+		u8 clk_mux_flags, spinlock_t *lock);
+
+/**
+ * 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);
+inline int __clk_get_enable_count(struct clk *clk);
+inline int __clk_get_prepare_count(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 */

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.