clk.c

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/*
 * Copyright (C) 2010-2011 Canonical Ltd <[email protected]>
 * Copyright (C) 2011-2012 Linaro Ltd <[email protected]>
 *
 * 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>
#include <linux/of.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;
}

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;
}

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

/* 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);

/***    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 = 0;
        goto out;
    }

    ret = clk->rate;

    if (clk->flags & CLK_IS_ROOT)
        goto out;

    if (!clk->parent)
        ret = 0;

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);
}

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;
}

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(IS_ERR(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);
}

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;
}

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);

unsigned long __clk_round_rate(struct clk *clk, unsigned long rate)
{
    unsigned long parent_rate = 0;

    if (!clk)
        return -EINVAL;

    if (!clk->ops->round_rate) {
        if (clk->flags & CLK_SET_RATE_PARENT)
            return __clk_round_rate(clk->parent, rate);
        else
            return clk->rate;
    }

    if (clk->parent)
        parent_rate = clk->parent->rate;

    return clk->ops->round_rate(clk->hw, rate, &parent_rate);
}

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);

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;
}

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);
}

unsigned long clk_get_rate(struct clk *clk)
{
    unsigned long rate;

    mutex_lock(&prepare_lock);

    if (clk && (clk->flags & CLK_GET_RATE_NOCACHE))
        __clk_recalc_rates(clk, 0);

    rate = __clk_get_rate(clk);
    mutex_unlock(&prepare_lock);

    return rate;
}
EXPORT_SYMBOL_GPL(clk_get_rate);

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 = 0;
    unsigned long new_rate;

    /* sanity */
    if (IS_ERR_OR_NULL(clk))
        return NULL;

    /* save parent rate, if it exists */
    if (clk->parent)
        best_parent_rate = clk->parent->rate;

    /* never propagate up to the parent */
    if (!(clk->flags & CLK_SET_RATE_PARENT)) {
        if (!clk->ops->round_rate) {
            clk->new_rate = clk->rate;
            return NULL;
        }
        new_rate = clk->ops->round_rate(clk->hw, rate, &best_parent_rate);
        goto out;
    }

    /* need clk->parent from here on out */
    if (!clk->parent) {
        pr_debug("%s: %s has NULL parent\n", __func__, clk->name);
        return NULL;
    }

    if (!clk->ops->round_rate) {
        top = clk_calc_new_rates(clk->parent, rate);
        new_rate = clk->parent->new_rate;

        goto out;
    }

    new_rate = clk->ops->round_rate(clk->hw, rate, &best_parent_rate);

    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;
    unsigned long best_parent_rate = 0;
    struct hlist_node *tmp;

    old_rate = clk->rate;

    if (clk->parent)
        best_parent_rate = clk->parent->rate;

    if (clk->ops->set_rate)
        clk->ops->set_rate(clk->hw, clk->new_rate, best_parent_rate);

    if (clk->ops->recalc_rate)
        clk->rate = clk->ops->recalc_rate(clk->hw, best_parent_rate);
    else
        clk->rate = best_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);
}

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;

    if ((clk->flags & CLK_SET_RATE_GATE) && clk->prepare_count) {
        ret = -EBUSY;
        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);

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 =
            kzalloc((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;

    if (!clk->parents)
        clk->parents = kzalloc((sizeof(struct clk*) * clk->num_parents),
                                GFP_KERNEL);

    /*
     * find index of new parent clock using cached parent ptrs,
     * or if not yet cached, use string name comparison and cache
     * them now to avoid future calls to __clk_lookup.
     */
    for (i = 0; i < clk->num_parents; i++) {
        if (clk->parents && clk->parents[i] == parent)
            break;
        else if (!strcmp(clk->parent_names[i], parent->name)) {
            if (clk->parents)
                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;
}

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);

int __clk_init(struct device *dev, struct clk *clk)
{
    int i, ret = 0;
    struct clk *orphan;
    struct hlist_node *tmp, *tmp2;

    if (!clk)
        return -EINVAL;

    mutex_lock(&prepare_lock);

    /* check to see if a clock with this name is already registered */
    if (__clk_lookup(clk->name)) {
        pr_debug("%s: clk %s already initialized\n",
                __func__, clk->name);
        ret = -EEXIST;
        goto out;
    }

    /* check that clk_ops are sane.  See Documentation/clk.txt */
    if (clk->ops->set_rate &&
            !(clk->ops->round_rate && clk->ops->recalc_rate)) {
        pr_warning("%s: %s must implement .round_rate & .recalc_rate\n",
                __func__, clk->name);
        ret = -EINVAL;
        goto out;
    }

    if (clk->ops->set_parent && !clk->ops->get_parent) {
        pr_warning("%s: %s must implement .get_parent & .set_parent\n",
                __func__, clk->name);
        ret = -EINVAL;
        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 > 1 && !clk->parents) {
        clk->parents = kzalloc((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 ret;
}

struct clk *__clk_register(struct device *dev, struct clk_hw *hw)
{
    int ret;
    struct clk *clk;

    clk = hw->clk;
    clk->name = hw->init->name;
    clk->ops = hw->init->ops;
    clk->hw = hw;
    clk->flags = hw->init->flags;
    clk->parent_names = hw->init->parent_names;
    clk->num_parents = hw->init->num_parents;

    ret = __clk_init(dev, clk);
    if (ret)
        return ERR_PTR(ret);

    return clk;
}
EXPORT_SYMBOL_GPL(__clk_register);

struct clk *clk_register(struct device *dev, struct clk_hw *hw)
{
    int i, ret;
    struct clk *clk;

    clk = kzalloc(sizeof(*clk), GFP_KERNEL);
    if (!clk) {
        pr_err("%s: could not allocate clk\n", __func__);
        ret = -ENOMEM;
        goto fail_out;
    }

    clk->name = kstrdup(hw->init->name, GFP_KERNEL);
    if (!clk->name) {
        pr_err("%s: could not allocate clk->name\n", __func__);
        ret = -ENOMEM;
        goto fail_name;
    }
    clk->ops = hw->init->ops;
    clk->hw = hw;
    clk->flags = hw->init->flags;
    clk->num_parents = hw->init->num_parents;
    hw->clk = clk;

    /* allocate local copy in case parent_names is __initdata */
    clk->parent_names = kzalloc((sizeof(char*) * clk->num_parents),
            GFP_KERNEL);

    if (!clk->parent_names) {
        pr_err("%s: could not allocate clk->parent_names\n", __func__);
        ret = -ENOMEM;
        goto fail_parent_names;
    }


    /* copy each string name in case parent_names is __initdata */
    for (i = 0; i < clk->num_parents; i++) {
        clk->parent_names[i] = kstrdup(hw->init->parent_names[i],
                        GFP_KERNEL);
        if (!clk->parent_names[i]) {
            pr_err("%s: could not copy parent_names\n", __func__);
            ret = -ENOMEM;
            goto fail_parent_names_copy;
        }
    }

    ret = __clk_init(dev, clk);
    if (!ret)
        return clk;

fail_parent_names_copy:
    while (--i >= 0)
        kfree(clk->parent_names[i]);
    kfree(clk->parent_names);
fail_parent_names:
    kfree(clk->name);
fail_name:
    kfree(clk);
fail_out:
    return ERR_PTR(ret);
}
EXPORT_SYMBOL_GPL(clk_register);

void clk_unregister(struct clk *clk) {}
EXPORT_SYMBOL_GPL(clk_unregister);

/***        clk rate change notifiers        ***/

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);

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);

#ifdef CONFIG_OF

struct of_clk_provider {
    struct list_head link;

    struct device_node *node;
    struct clk *(*get)(struct of_phandle_args *clkspec, void *data);
    void *data;
};

static LIST_HEAD(of_clk_providers);
static DEFINE_MUTEX(of_clk_lock);

struct clk *of_clk_src_simple_get(struct of_phandle_args *clkspec,
                     void *data)
{
    return data;
}
EXPORT_SYMBOL_GPL(of_clk_src_simple_get);

struct clk *of_clk_src_onecell_get(struct of_phandle_args *clkspec, void *data)
{
    struct clk_onecell_data *clk_data = data;
    unsigned int idx = clkspec->args[0];

    if (idx >= clk_data->clk_num) {
        pr_err("%s: invalid clock index %d\n", __func__, idx);
        return ERR_PTR(-EINVAL);
    }

    return clk_data->clks[idx];
}
EXPORT_SYMBOL_GPL(of_clk_src_onecell_get);

int of_clk_add_provider(struct device_node *np,
            struct clk *(*clk_src_get)(struct of_phandle_args *clkspec,
                           void *data),
            void *data)
{
    struct of_clk_provider *cp;

    cp = kzalloc(sizeof(struct of_clk_provider), GFP_KERNEL);
    if (!cp)
        return -ENOMEM;

    cp->node = of_node_get(np);
    cp->data = data;
    cp->get = clk_src_get;

    mutex_lock(&of_clk_lock);
    list_add(&cp->link, &of_clk_providers);
    mutex_unlock(&of_clk_lock);
    pr_debug("Added clock from %s\n", np->full_name);

    return 0;
}
EXPORT_SYMBOL_GPL(of_clk_add_provider);

void of_clk_del_provider(struct device_node *np)
{
    struct of_clk_provider *cp;

    mutex_lock(&of_clk_lock);
    list_for_each_entry(cp, &of_clk_providers, link) {
        if (cp->node == np) {
            list_del(&cp->link);
            of_node_put(cp->node);
            kfree(cp);
            break;
        }
    }
    mutex_unlock(&of_clk_lock);
}
EXPORT_SYMBOL_GPL(of_clk_del_provider);

struct clk *of_clk_get_from_provider(struct of_phandle_args *clkspec)
{
    struct of_clk_provider *provider;
    struct clk *clk = ERR_PTR(-ENOENT);

    /* Check if we have such a provider in our array */
    mutex_lock(&of_clk_lock);
    list_for_each_entry(provider, &of_clk_providers, link) {
        if (provider->node == clkspec->np)
            clk = provider->get(clkspec, provider->data);
        if (!IS_ERR(clk))
            break;
    }
    mutex_unlock(&of_clk_lock);

    return clk;
}

const char *of_clk_get_parent_name(struct device_node *np, int index)
{
    struct of_phandle_args clkspec;
    const char *clk_name;
    int rc;

    if (index < 0)
        return NULL;

    rc = of_parse_phandle_with_args(np, "clocks", "#clock-cells", index,
                    &clkspec);
    if (rc)
        return NULL;

    if (of_property_read_string_index(clkspec.np, "clock-output-names",
                      clkspec.args_count ? clkspec.args[0] : 0,
                      &clk_name) < 0)
        clk_name = clkspec.np->name;

    of_node_put(clkspec.np);
    return clk_name;
}
EXPORT_SYMBOL_GPL(of_clk_get_parent_name);

void __init of_clk_init(const struct of_device_id *matches)
{
    struct device_node *np;

    for_each_matching_node(np, matches) {
        const struct of_device_id *match = of_match_node(matches, np);
        of_clk_init_cb_t clk_init_cb = match->data;
        clk_init_cb(np);
    }
}
#endif