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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 2007-2009 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/cpufreq.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);
static DEFINE_SPINLOCK(clockfw_lock);

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

/*
 * Retrieve a clock by name.
 *
 * Note that we first try to use device id on the bus
 * and clock name. If this fails, we try to use "<name>.<id>". If this fails,
 * we try to use clock name only.
 * The reference count to the clock's module owner ref count is incremented.
 */
struct clk *clk_get(struct device *dev, const char *id)
{
      struct clk *p, *clk = ERR_PTR(-ENOENT);
      int idno;
      const char *str;

      if (id == NULL)
            return clk;

      if (dev == NULL || dev->bus != &platform_bus_type)
            idno = -1;
      else
            idno = to_platform_device(dev)->id;

      mutex_lock(&clocks_mutex);

      list_for_each_entry(p, &clocks, node) {
            if (p->id == idno &&
                strcmp(id, p->name) == 0 && try_module_get(p->owner)) {
                  clk = p;
                  goto found;
            }
      }

      str = strrchr(id, '.');
      if (str) {
            int cnt = str - id;
            str++;
            idno = simple_strtol(str, NULL, 10);
            list_for_each_entry(p, &clocks, node) {
                  if (p->id == idno &&
                      strlen(p->name) == cnt &&
                      strncmp(id, p->name, cnt) == 0 &&
                      try_module_get(p->owner)) {
                        clk = p;
                        goto found;
                  }
            }
      }

      list_for_each_entry(p, &clocks, node) {
            if (strcmp(id, p->name) == 0 && try_module_get(p->owner)) {
                  clk = p;
                  goto found;
            }
      }

      printk(KERN_WARNING "clk: Unable to get requested clock: %s\n", id);

found:
      mutex_unlock(&clocks_mutex);

      return clk;
}
EXPORT_SYMBOL(clk_get);

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

      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)
{
      unsigned long flags;
      int ret = 0;

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

      spin_lock_irqsave(&clockfw_lock, flags);

      ret = __clk_enable(clk);

      spin_unlock_irqrestore(&clockfw_lock, flags);

#if defined(CONFIG_CPU_FREQ)
      if ((clk->flags & CPU_FREQ_TRIG_UPDATE)
          && (clk_get_usecount(clk) == 1))
            cpufreq_update_policy(0);
#endif
      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)
{
      unsigned long flags;

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

      spin_lock_irqsave(&clockfw_lock, flags);

      __clk_disable(clk);

      spin_unlock_irqrestore(&clockfw_lock, flags);

#if defined(CONFIG_CPU_FREQ)
      if ((clk->flags & CPU_FREQ_TRIG_UPDATE)
          && (clk_get_usecount(clk) == 0))
            cpufreq_update_policy(0);
#endif
}
EXPORT_SYMBOL(clk_disable);

/*!
 * @brief Function to get the usage count for the requested clock.
 *
 * This function returns the reference count for the clock.
 *
 * @param clk     Handle to clock to disable.
 *
 * @return Returns the usage count for the requested clock.
 */
int clk_get_usecount(struct clk *clk)
{
      if (clk == NULL || IS_ERR(clk))
            return 0;

      return clk->usecount;
}

EXPORT_SYMBOL(clk_get_usecount);

/* 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;

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

/* Decrement the clock's module reference count */
void clk_put(struct clk *clk)
{
      if (clk && !IS_ERR(clk))
            module_put(clk->owner);
}
EXPORT_SYMBOL(clk_put);

/* 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);

/* Propagate rate to children */
void propagate_rate(struct clk *tclk)
{
      struct clk *clkp;

      if (tclk == NULL || IS_ERR(tclk))
            return;

      pr_debug("mxc clock: finding children of %s-%d\n", tclk->name,
             tclk->id);
      list_for_each_entry(clkp, &clocks, node) {
            if (likely(clkp->parent != tclk))
                  continue;
            pr_debug("mxc clock: %s-%d: recalculating rate: old = %lu, ",
                   clkp->name, clkp->id, clkp->rate);
            if (likely((u32) clkp->recalc))
                  clkp->recalc(clkp);
            else
                  clkp->rate = tclk->rate;
            pr_debug("new = %lu\n", clkp->rate);
            propagate_rate(clkp);
      }
}

/* 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)
{
      unsigned long flags;
      int ret = -EINVAL;

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

      spin_lock_irqsave(&clockfw_lock, flags);

      ret = clk->set_rate(clk, rate);
      if (unlikely((ret == 0) && (clk->flags & RATE_PROPAGATES)))
            propagate_rate(clk);

      spin_unlock_irqrestore(&clockfw_lock, flags);

      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)
{
      unsigned long flags;
      int ret = -EINVAL;
      struct clk *prev_parent = clk->parent;

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

      if (clk->usecount != 0) {
            clk_enable(parent);
      }

      spin_lock_irqsave(&clockfw_lock, flags);
      ret = clk->set_parent(clk, parent);
      if (ret == 0) {
            clk->parent = parent;
            if (clk->recalc) {
                  clk->recalc(clk);
            } else {
                  clk->rate = parent->rate;
            }
            if (unlikely(clk->flags & RATE_PROPAGATES))
                  propagate_rate(clk);
      }
      spin_unlock_irqrestore(&clockfw_lock, flags);

      if (clk->usecount != 0) {
            clk_disable(prev_parent);
      }

      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);

/*
 * Add a new clock to the clock tree.
 */
int clk_register(struct clk *clk)
{
      if (clk == NULL || IS_ERR(clk))
            return -EINVAL;

      mutex_lock(&clocks_mutex);
      list_add(&clk->node, &clocks);
      mutex_unlock(&clocks_mutex);

      return 0;
}
EXPORT_SYMBOL(clk_register);

/* Remove a clock from the clock tree */
void clk_unregister(struct clk *clk)
{
      if (clk == NULL || IS_ERR(clk))
            return;

      mutex_lock(&clocks_mutex);
      list_del(&clk->node);
      mutex_unlock(&clocks_mutex);
}
EXPORT_SYMBOL(clk_unregister);

#ifdef CONFIG_PROC_FS
static int mxc_clock_read_proc(char *page, char **start, off_t off,
                        int count, int *eof, void *data)
{
      struct clk *clkp;
      char *p = page;
      int len;

      list_for_each_entry(clkp, &clocks, node) {
            p += sprintf(p, "%s-%d:\t\t%lu, %d", clkp->name, clkp->id,
                        clk_get_rate(clkp), clkp->usecount);
            if (clkp->parent)
                  p += sprintf(p, ", %s-%d\n", clkp->parent->name,
                             clkp->parent->id);
            else
                  p += sprintf(p, "\n");
      }

      len = (p - page) - off;
      if (len < 0)
            len = 0;

      *eof = (len <= count) ? 1 : 0;
      *start = page + off;

      return len;
}

static int __init mxc_setup_proc_entry(void)
{
      struct proc_dir_entry *res;

      res = create_proc_read_entry("cpu/clocks", 0, NULL,
                             mxc_clock_read_proc, NULL);
      if (!res) {
            printk(KERN_ERR "Failed to create proc/cpu/clocks\n");
            return -ENOMEM;
      }
      return 0;
}

late_initcall(mxc_setup_proc_entry);
#endif

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