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clock.c

/*
 * Based on arch/arm/plat-omap/clock.c
 *
 * Copyright (C) 2004 - 2005 Nokia corporation
 * Written by Tuukka Tikkanen <tuukka.tikkanen@elektrobit.com>
 * Modified for omap shared clock framework by Tony Lindgren <tony@atomide.com>
 * Copyright 2007 Freescale Semiconductor, Inc. All Rights Reserved.
 * Copyright 2008 Juergen Beisert, kernel@pengutronix.de
 *
 * This program is free software; you can redistribute it and/or
 * modify it under the terms of the GNU General Public License
 * as published by the Free Software Foundation; either version 2
 * of the License, or (at your option) any later version.
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write to the Free Software
 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston,
 * MA  02110-1301, USA.
 */

/* #define DEBUG */

#include <linux/clk.h>
#include <linux/err.h>
#include <linux/errno.h>
#include <linux/init.h>
#include <linux/io.h>
#include <linux/kernel.h>
#include <linux/list.h>
#include <linux/module.h>
#include <linux/mutex.h>
#include <linux/platform_device.h>
#include <linux/proc_fs.h>
#include <linux/semaphore.h>
#include <linux/string.h>

#include <mach/clock.h>

static LIST_HEAD(clocks);
static DEFINE_MUTEX(clocks_mutex);

/*-------------------------------------------------------------------------
 * Standard clock functions defined in include/linux/clk.h
 *-------------------------------------------------------------------------*/

static void __clk_disable(struct clk *clk)
{
      if (clk == NULL || IS_ERR(clk))
            return;
      WARN_ON(!clk->usecount);

      if (!(--clk->usecount)) {
            if (clk->disable)
                  clk->disable(clk);
            __clk_disable(clk->parent);
            __clk_disable(clk->secondary);
      }
}

static int __clk_enable(struct clk *clk)
{
      if (clk == NULL || IS_ERR(clk))
            return -EINVAL;

      if (clk->usecount++ == 0) {
            __clk_enable(clk->parent);
            __clk_enable(clk->secondary);

            if (clk->enable)
                  clk->enable(clk);
      }
      return 0;
}

/* This function increments the reference count on the clock and enables the
 * clock if not already enabled. The parent clock tree is recursively enabled
 */
int clk_enable(struct clk *clk)
{
      int ret = 0;

      if (clk == NULL || IS_ERR(clk))
            return -EINVAL;

      mutex_lock(&clocks_mutex);
      ret = __clk_enable(clk);
      mutex_unlock(&clocks_mutex);

      return ret;
}
EXPORT_SYMBOL(clk_enable);

/* This function decrements the reference count on the clock and disables
 * the clock when reference count is 0. The parent clock tree is
 * recursively disabled
 */
void clk_disable(struct clk *clk)
{
      if (clk == NULL || IS_ERR(clk))
            return;

      mutex_lock(&clocks_mutex);
      __clk_disable(clk);
      mutex_unlock(&clocks_mutex);
}
EXPORT_SYMBOL(clk_disable);

/* Retrieve the *current* clock rate. If the clock itself
 * does not provide a special calculation routine, ask
 * its parent and so on, until one is able to return
 * a valid clock rate
 */
unsigned long clk_get_rate(struct clk *clk)
{
      if (clk == NULL || IS_ERR(clk))
            return 0UL;

      if (clk->get_rate)
            return clk->get_rate(clk);

      return clk_get_rate(clk->parent);
}
EXPORT_SYMBOL(clk_get_rate);

/* Round the requested clock rate to the nearest supported
 * rate that is less than or equal to the requested rate.
 * This is dependent on the clock's current parent.
 */
long clk_round_rate(struct clk *clk, unsigned long rate)
{
      if (clk == NULL || IS_ERR(clk) || !clk->round_rate)
            return 0;

      return clk->round_rate(clk, rate);
}
EXPORT_SYMBOL(clk_round_rate);

/* Set the clock to the requested clock rate. The rate must
 * match a supported rate exactly based on what clk_round_rate returns
 */
int clk_set_rate(struct clk *clk, unsigned long rate)
{
      int ret = -EINVAL;

      if (clk == NULL || IS_ERR(clk) || clk->set_rate == NULL || rate == 0)
            return ret;

      mutex_lock(&clocks_mutex);
      ret = clk->set_rate(clk, rate);
      mutex_unlock(&clocks_mutex);

      return ret;
}
EXPORT_SYMBOL(clk_set_rate);

/* Set the clock's parent to another clock source */
int clk_set_parent(struct clk *clk, struct clk *parent)
{
      int ret = -EINVAL;
      struct clk *old;

      if (clk == NULL || IS_ERR(clk) || parent == NULL ||
          IS_ERR(parent) || clk->set_parent == NULL)
            return ret;

      if (clk->usecount)
            clk_enable(parent);

      mutex_lock(&clocks_mutex);
      ret = clk->set_parent(clk, parent);
      if (ret == 0) {
            old = clk->parent;
            clk->parent = parent;
      } else {
            old = parent;
      }
      mutex_unlock(&clocks_mutex);

      if (clk->usecount)
            clk_disable(old);

      return ret;
}
EXPORT_SYMBOL(clk_set_parent);

/* Retrieve the clock's parent clock source */
struct clk *clk_get_parent(struct clk *clk)
{
      struct clk *ret = NULL;

      if (clk == NULL || IS_ERR(clk))
            return ret;

      return clk->parent;
}
EXPORT_SYMBOL(clk_get_parent);

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