Documentation: common clk API

[linux.git] / include / linux / clk.h

/*
 *  linux/include/linux/clk.h
 *
 *  Copyright (C) 2004 ARM Limited.
 *  Written by Deep Blue Solutions Limited.
 *
 * 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_H
#define __LINUX_CLK_H

#include <linux/kernel.h>

struct device;

/*
 * The base API.
 */


/*
 * struct clk - an machine class defined object / cookie.
 */
struct clk;

/**
 * clk_get - lookup and obtain a reference to a clock producer.
 * @dev: device for clock "consumer"
 * @id: clock comsumer ID
 *
 * Returns a struct clk corresponding to the clock producer, or
 * valid IS_ERR() condition containing errno.  The implementation
 * uses @dev and @id to determine the clock consumer, and thereby
 * the clock producer.  (IOW, @id may be identical strings, but
 * clk_get may return different clock producers depending on @dev.)
 *
 * Drivers must assume that the clock source is not enabled.
 *
 * clk_get should not be called from within interrupt context.
 */
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);

/**
 * clk_disable - inform the system when the clock source is no longer required.
 * @clk: clock source
 *
 * 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
 * disabled.
 */
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_prepare_enable helps cases using clk_enable in non-atomic context. */
static inline int clk_prepare_enable(struct clk *clk)
{
	int ret;

	ret = clk_prepare(clk);
	if (ret)
		return ret;
	ret = clk_enable(clk);
	if (ret)
		clk_unprepare(clk);

	return ret;
}

/* clk_disable_unprepare helps cases using clk_disable in non-atomic context. */
static inline void clk_disable_unprepare(struct clk *clk)
{
	clk_disable(clk);
	clk_unprepare(clk);
}

/**
 * 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.
 * @clk: clock source
 */
unsigned long clk_get_rate(struct clk *clk);

/**
 * clk_put	- "free" the clock source
 * @clk: clock source
 *
 * Note: drivers must ensure that all clk_enable calls made on this
 * clock source are balanced by clk_disable calls prior to calling
 * this function.
 *
 * clk_put should not be called from within interrupt context.
 */
void clk_put(struct clk *clk);


/*
 * The remaining APIs are optional for machine class support.
 */


/**
 * clk_round_rate - adjust a rate to the exact rate a clock can provide
 * @clk: clock source
 * @rate: desired clock rate in Hz
 *
 * Returns rounded clock rate in Hz, or negative errno.
 */
long clk_round_rate(struct clk *clk, unsigned long rate);
 
/**
 * clk_set_rate - set the clock rate for a clock source
 * @clk: clock source
 * @rate: desired clock rate in Hz
 *
 * Returns success (0) or negative errno.
 */
int clk_set_rate(struct clk *clk, unsigned long rate);
 
/**
 * clk_set_parent - set the parent clock source for this clock
 * @clk: clock source
 * @parent: parent clock source
 *
 * Returns success (0) or negative errno.
 */
int clk_set_parent(struct clk *clk, struct clk *parent);

/**
 * clk_get_parent - get the parent clock source for this clock
 * @clk: clock source
 *
 * Returns struct clk corresponding to parent clock source, or
 * valid IS_ERR() condition containing errno.
 */
struct clk *clk_get_parent(struct clk *clk);

/**
 * clk_get_sys - get a clock based upon the device name
 * @dev_id: device name
 * @con_id: connection ID
 *
 * Returns a struct clk corresponding to the clock producer, or
 * valid IS_ERR() condition containing errno.  The implementation
 * uses @dev_id and @con_id to determine the clock consumer, and
 * thereby the clock producer. In contrast to clk_get() this function
 * takes the device name instead of the device itself for identification.
 *
 * Drivers must assume that the clock source is not enabled.
 *
 * clk_get_sys should not be called from within interrupt context.
 */
struct clk *clk_get_sys(const char *dev_id, const char *con_id);

/**
 * clk_add_alias - add a new clock alias
 * @alias: name for clock alias
 * @alias_dev_name: device name
 * @id: platform specific clock name
 * @dev: device
 *
 * Allows using generic clock names for drivers by adding a new alias.
 * Assumes clkdev, see clkdev.h for more info.
 */
int clk_add_alias(const char *alias, const char *alias_dev_name, char *id,
			struct device *dev);

#endif