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clk: provide prepare/unprepare functions

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As discussed previously, there's the need on some platforms to run some
parts of clk_enable() in contexts which can schedule.  The solution
which was agreed upon was to provide clk_prepare() and clk_unprepare()
to contain this parts, while clk_enable() and clk_disable() perform
the atomic part.

This patch provides a common definition for clk_prepare() and
clk_unprepare() in linux/clk.h, and provides an upgrade path for
existing implementation and drivers: drivers can start using
clk_prepare() and clk_unprepare() once this patch is merged without
having to wait for platform support.  Platforms can then start to
provide these additional functions.

Eventually, HAVE_CLK_PREPARE will be removed from the kernel, and
everyone will have to provide these new APIs.

Acked-by: Saravana Kannan <skannan@codeaurora.org>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>
This commit is contained in:
Russell King 2011-09-22 11:30:50 +01:00
parent 6cfa6279ed
commit 40d3e0f494
1 changed files with 43 additions and 0 deletions
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43
include/linux/clk.h
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@ -11,6 +11,8 @@
#ifndef __LINUX_CLK_H
#define __LINUX_CLK_H
#include <linux/kernel.h>
struct device;
/*
@ -40,12 +42,32 @@ struct clk;
*/
struct clk *clk_get(struct device *dev, const char *id);
/**
* clk_prepare - prepare a clock source
* @clk: clock source
*
* This prepares the clock source for use.
*
* Must not be called from within atomic context.
*/
#ifdef CONFIG_HAVE_CLK_PREPARE
int clk_prepare(struct clk *clk);
#else
static inline int clk_prepare(struct clk *clk)
{
might_sleep();
return 0;
}
#endif
/**
* clk_enable - inform the system when the clock source should be running.
* @clk: clock source
*
* If the clock can not be enabled/disabled, this should return success.
*
* May be called from atomic contexts.
*
* Returns success (0) or negative errno.
*/
int clk_enable(struct clk *clk);
@ -57,6 +79,8 @@ int clk_enable(struct clk *clk);
* Inform the system that a clock source is no longer required by
* a driver and may be shut down.
*
* May be called from atomic contexts.
*
* Implementation detail: if the clock source is shared between
* multiple drivers, clk_enable() calls must be balanced by the
* same number of clk_disable() calls for the clock source to be
@ -64,6 +88,25 @@ int clk_enable(struct clk *clk);
*/
void clk_disable(struct clk *clk);
/**
* clk_unprepare - undo preparation of a clock source
* @clk: clock source
*
* This undoes a previously prepared clock. The caller must balance
* the number of prepare and unprepare calls.
*
* Must not be called from within atomic context.
*/
#ifdef CONFIG_HAVE_CLK_PREPARE
void clk_unprepare(struct clk *clk);
#else
static inline void clk_unprepare(struct clk *clk)
{
might_sleep();
}
#endif
/**
* clk_get_rate - obtain the current clock rate (in Hz) for a clock source.
* This is only valid once the clock source has been enabled.