clk: Change clk_ops->determine_rate to return a clk_hw as the best parent

[linux.git] / drivers / clk / clk.c

/*
 * 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/clk/clk-conf.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>
#include <linux/device.h>
#include <linux/init.h>
#include <linux/sched.h>

#include "clk.h"

static DEFINE_SPINLOCK(enable_lock);
static DEFINE_MUTEX(prepare_lock);

static struct task_struct *prepare_owner;
static struct task_struct *enable_owner;

static int prepare_refcnt;
static int enable_refcnt;

static HLIST_HEAD(clk_root_list);
static HLIST_HEAD(clk_orphan_list);
static LIST_HEAD(clk_notifier_list);

/***           locking             ***/
static void clk_prepare_lock(void)
{
        if (!mutex_trylock(&prepare_lock)) {
                if (prepare_owner == current) {
                        prepare_refcnt++;
                        return;
                }
                mutex_lock(&prepare_lock);
        }
        WARN_ON_ONCE(prepare_owner != NULL);
        WARN_ON_ONCE(prepare_refcnt != 0);
        prepare_owner = current;
        prepare_refcnt = 1;
}

static void clk_prepare_unlock(void)
{
        WARN_ON_ONCE(prepare_owner != current);
        WARN_ON_ONCE(prepare_refcnt == 0);

        if (--prepare_refcnt)
                return;
        prepare_owner = NULL;
        mutex_unlock(&prepare_lock);
}

static unsigned long clk_enable_lock(void)
{
        unsigned long flags;

        if (!spin_trylock_irqsave(&enable_lock, flags)) {
                if (enable_owner == current) {
                        enable_refcnt++;
                        return flags;
                }
                spin_lock_irqsave(&enable_lock, flags);
        }
        WARN_ON_ONCE(enable_owner != NULL);
        WARN_ON_ONCE(enable_refcnt != 0);
        enable_owner = current;
        enable_refcnt = 1;
        return flags;
}

static void clk_enable_unlock(unsigned long flags)
{
        WARN_ON_ONCE(enable_owner != current);
        WARN_ON_ONCE(enable_refcnt == 0);

        if (--enable_refcnt)
                return;
        enable_owner = NULL;
        spin_unlock_irqrestore(&enable_lock, flags);
}

/***        debugfs support        ***/

#ifdef CONFIG_DEBUG_FS
#include <linux/debugfs.h>

static struct dentry *rootdir;
static int inited = 0;
static DEFINE_MUTEX(clk_debug_lock);
static HLIST_HEAD(clk_debug_list);

static struct hlist_head *all_lists[] = {
        &clk_root_list,
        &clk_orphan_list,
        NULL,
};

static struct hlist_head *orphan_list[] = {
        &clk_orphan_list,
        NULL,
};

static void clk_summary_show_one(struct seq_file *s, struct clk *c, int level)
{
        if (!c)
                return;

        seq_printf(s, "%*s%-*s %11d %12d %11lu %10lu %-3d\n",
                   level * 3 + 1, "",
                   30 - level * 3, c->name,
                   c->enable_count, c->prepare_count, clk_get_rate(c),
                   clk_get_accuracy(c), clk_get_phase(c));
}

static void clk_summary_show_subtree(struct seq_file *s, struct clk *c,
                                     int level)
{
        struct clk *child;

        if (!c)
                return;

        clk_summary_show_one(s, c, level);

        hlist_for_each_entry(child, &c->children, child_node)
                clk_summary_show_subtree(s, child, level + 1);
}

static int clk_summary_show(struct seq_file *s, void *data)
{
        struct clk *c;
        struct hlist_head **lists = (struct hlist_head **)s->private;

        seq_puts(s, "   clock                         enable_cnt  prepare_cnt        rate   accuracy   phase\n");
        seq_puts(s, "----------------------------------------------------------------------------------------\n");

        clk_prepare_lock();

        for (; *lists; lists++)
                hlist_for_each_entry(c, *lists, child_node)
                        clk_summary_show_subtree(s, c, 0);

        clk_prepare_unlock();

        return 0;
}


static int clk_summary_open(struct inode *inode, struct file *file)
{
        return single_open(file, clk_summary_show, inode->i_private);
}

static const struct file_operations clk_summary_fops = {
        .open           = clk_summary_open,
        .read           = seq_read,
        .llseek         = seq_lseek,
        .release        = single_release,
};

static void clk_dump_one(struct seq_file *s, struct clk *c, int level)
{
        if (!c)
                return;

        seq_printf(s, "\"%s\": { ", c->name);
        seq_printf(s, "\"enable_count\": %d,", c->enable_count);
        seq_printf(s, "\"prepare_count\": %d,", c->prepare_count);
        seq_printf(s, "\"rate\": %lu", clk_get_rate(c));
        seq_printf(s, "\"accuracy\": %lu", clk_get_accuracy(c));
        seq_printf(s, "\"phase\": %d", clk_get_phase(c));
}

static void clk_dump_subtree(struct seq_file *s, struct clk *c, int level)
{
        struct clk *child;

        if (!c)
                return;

        clk_dump_one(s, c, level);

        hlist_for_each_entry(child, &c->children, child_node) {
                seq_printf(s, ",");
                clk_dump_subtree(s, child, level + 1);
        }

        seq_printf(s, "}");
}

static int clk_dump(struct seq_file *s, void *data)
{
        struct clk *c;
        bool first_node = true;
        struct hlist_head **lists = (struct hlist_head **)s->private;

        seq_printf(s, "{");

        clk_prepare_lock();

        for (; *lists; lists++) {
                hlist_for_each_entry(c, *lists, child_node) {
                        if (!first_node)
                                seq_puts(s, ",");
                        first_node = false;
                        clk_dump_subtree(s, c, 0);
                }
        }

        clk_prepare_unlock();

        seq_printf(s, "}");
        return 0;
}


static int clk_dump_open(struct inode *inode, struct file *file)
{
        return single_open(file, clk_dump, inode->i_private);
}

static const struct file_operations clk_dump_fops = {
        .open           = clk_dump_open,
        .read           = seq_read,
        .llseek         = seq_lseek,
        .release        = single_release,
};

/* 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_u32("clk_accuracy", S_IRUGO, clk->dentry,
                        (u32 *)&clk->accuracy);
        if (!d)
                goto err_out;

        d = debugfs_create_u32("clk_phase", S_IRUGO, clk->dentry,
                        (u32 *)&clk->phase);
        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;

        if (clk->ops->debug_init) {
                ret = clk->ops->debug_init(clk->hw, clk->dentry);
                if (ret)
                        goto err_out;
        }

        ret = 0;
        goto out;

err_out:
        debugfs_remove_recursive(clk->dentry);
        clk->dentry = NULL;
out:
        return ret;
}

/**
 * clk_debug_register - add a clk node to the debugfs clk tree
 * @clk: the clk being added to the debugfs clk tree
 *
 * Dynamically adds a clk to the debugfs clk tree if debugfs has been
 * initialized.  Otherwise it bails out early since the debugfs clk tree
 * will be created lazily by clk_debug_init as part of a late_initcall.
 */
static int clk_debug_register(struct clk *clk)
{
        int ret = 0;

        mutex_lock(&clk_debug_lock);
        hlist_add_head(&clk->debug_node, &clk_debug_list);

        if (!inited)
                goto unlock;

        ret = clk_debug_create_one(clk, rootdir);
unlock:
        mutex_unlock(&clk_debug_lock);

        return ret;
}

 /**
 * clk_debug_unregister - remove a clk node from the debugfs clk tree
 * @clk: the clk being removed from the debugfs clk tree
 *
 * Dynamically removes a clk and all it's children clk nodes from the
 * debugfs clk tree if clk->dentry points to debugfs created by
 * clk_debug_register in __clk_init.
 */
static void clk_debug_unregister(struct clk *clk)
{
        mutex_lock(&clk_debug_lock);
        if (!clk->dentry)
                goto out;

        hlist_del_init(&clk->debug_node);
        debugfs_remove_recursive(clk->dentry);
        clk->dentry = NULL;
out:
        mutex_unlock(&clk_debug_lock);
}

struct dentry *clk_debugfs_add_file(struct clk_hw *hw, char *name, umode_t mode,
                                void *data, const struct file_operations *fops)
{
        struct dentry *d = NULL;

        if (hw->clk->dentry)
                d = debugfs_create_file(name, mode, hw->clk->dentry, data, fops);

        return d;
}
EXPORT_SYMBOL_GPL(clk_debugfs_add_file);

/**
 * clk_debug_init - lazily create the debugfs clk tree visualization
 *
 * clks are often initialized very early during boot before memory can
 * be dynamically allocated and well before debugfs is setup.
 * clk_debug_init walks the clk tree hierarchy while holding
 * prepare_lock and creates the topology as part of a late_initcall,
 * thus insuring that clks initialized very early will still be
 * represented in the debugfs clk tree.  This function should only be
 * called once at boot-time, and all other clks added dynamically will
 * be done so with clk_debug_register.
 */
static int __init clk_debug_init(void)
{
        struct clk *clk;
        struct dentry *d;

        rootdir = debugfs_create_dir("clk", NULL);

        if (!rootdir)
                return -ENOMEM;

        d = debugfs_create_file("clk_summary", S_IRUGO, rootdir, &all_lists,
                                &clk_summary_fops);
        if (!d)
                return -ENOMEM;

        d = debugfs_create_file("clk_dump", S_IRUGO, rootdir, &all_lists,
                                &clk_dump_fops);
        if (!d)
                return -ENOMEM;

        d = debugfs_create_file("clk_orphan_summary", S_IRUGO, rootdir,
                                &orphan_list, &clk_summary_fops);
        if (!d)
                return -ENOMEM;

        d = debugfs_create_file("clk_orphan_dump", S_IRUGO, rootdir,
                                &orphan_list, &clk_dump_fops);
        if (!d)
                return -ENOMEM;

        mutex_lock(&clk_debug_lock);
        hlist_for_each_entry(clk, &clk_debug_list, debug_node)
                clk_debug_create_one(clk, rootdir);

        inited = 1;
        mutex_unlock(&clk_debug_lock);

        return 0;
}
late_initcall(clk_debug_init);
#else
static inline int clk_debug_register(struct clk *clk) { return 0; }
static inline void clk_debug_reparent(struct clk *clk, struct clk *new_parent)
{
}
static inline void clk_debug_unregister(struct clk *clk)
{
}
#endif

/* caller must hold prepare_lock */
static void clk_unprepare_unused_subtree(struct clk *clk)
{
        struct clk *child;

        if (!clk)
                return;

        hlist_for_each_entry(child, &clk->children, child_node)
                clk_unprepare_unused_subtree(child);

        if (clk->prepare_count)
                return;

        if (clk->flags & CLK_IGNORE_UNUSED)
                return;

        if (__clk_is_prepared(clk)) {
                if (clk->ops->unprepare_unused)
                        clk->ops->unprepare_unused(clk->hw);
                else if (clk->ops->unprepare)
                        clk->ops->unprepare(clk->hw);
        }
}

/* caller must hold prepare_lock */
static void clk_disable_unused_subtree(struct clk *clk)
{
        struct clk *child;
        unsigned long flags;

        if (!clk)
                goto out;

        hlist_for_each_entry(child, &clk->children, child_node)
                clk_disable_unused_subtree(child);

        flags = clk_enable_lock();

        if (clk->enable_count)
                goto unlock_out;

        if (clk->flags & CLK_IGNORE_UNUSED)
                goto unlock_out;

        /*
         * some gate clocks have special needs during the disable-unused
         * sequence.  call .disable_unused if available, otherwise fall
         * back to .disable
         */
        if (__clk_is_enabled(clk)) {
                if (clk->ops->disable_unused)
                        clk->ops->disable_unused(clk->hw);
                else if (clk->ops->disable)
                        clk->ops->disable(clk->hw);
        }

unlock_out:
        clk_enable_unlock(flags);

out:
        return;
}

static bool clk_ignore_unused;
static int __init clk_ignore_unused_setup(char *__unused)
{
        clk_ignore_unused = true;
        return 1;
}
__setup("clk_ignore_unused", clk_ignore_unused_setup);

static int clk_disable_unused(void)
{
        struct clk *clk;

        if (clk_ignore_unused) {
                pr_warn("clk: Not disabling unused clocks\n");
                return 0;
        }

        clk_prepare_lock();

        hlist_for_each_entry(clk, &clk_root_list, child_node)
                clk_disable_unused_subtree(clk);

        hlist_for_each_entry(clk, &clk_orphan_list, child_node)
                clk_disable_unused_subtree(clk);

        hlist_for_each_entry(clk, &clk_root_list, child_node)
                clk_unprepare_unused_subtree(clk);

        hlist_for_each_entry(clk, &clk_orphan_list, child_node)
                clk_unprepare_unused_subtree(clk);

        clk_prepare_unlock();

        return 0;
}
late_initcall_sync(clk_disable_unused);

/***    helper functions   ***/

const char *__clk_get_name(struct clk *clk)
{
        return !clk ? NULL : clk->name;
}
EXPORT_SYMBOL_GPL(__clk_get_name);

struct clk_hw *__clk_get_hw(struct clk *clk)
{
        return !clk ? NULL : clk->hw;
}
EXPORT_SYMBOL_GPL(__clk_get_hw);

u8 __clk_get_num_parents(struct clk *clk)
{
        return !clk ? 0 : clk->num_parents;
}
EXPORT_SYMBOL_GPL(__clk_get_num_parents);

struct clk *__clk_get_parent(struct clk *clk)
{
        return !clk ? NULL : clk->parent;
}
EXPORT_SYMBOL_GPL(__clk_get_parent);

struct clk *clk_get_parent_by_index(struct clk *clk, u8 index)
{
        if (!clk || index >= clk->num_parents)
                return NULL;
        else if (!clk->parents)
                return __clk_lookup(clk->parent_names[index]);
        else if (!clk->parents[index])
                return clk->parents[index] =
                        __clk_lookup(clk->parent_names[index]);
        else
                return clk->parents[index];
}
EXPORT_SYMBOL_GPL(clk_get_parent_by_index);

unsigned int __clk_get_enable_count(struct clk *clk)
{
        return !clk ? 0 : clk->enable_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;
}
EXPORT_SYMBOL_GPL(__clk_get_rate);

static unsigned long __clk_get_accuracy(struct clk *clk)
{
        if (!clk)
                return 0;

        return clk->accuracy;
}

unsigned long __clk_get_flags(struct clk *clk)
{
        return !clk ? 0 : clk->flags;
}
EXPORT_SYMBOL_GPL(__clk_get_flags);

bool __clk_is_prepared(struct clk *clk)
{
        int ret;

        if (!clk)
                return false;

        /*
         * .is_prepared is optional for clocks that can prepare
         * fall back to software usage counter if it is missing
         */
        if (!clk->ops->is_prepared) {
                ret = clk->prepare_count ? 1 : 0;
                goto out;
        }

        ret = clk->ops->is_prepared(clk->hw);
out:
        return !!ret;
}

bool __clk_is_enabled(struct clk *clk)
{
        int ret;

        if (!clk)
                return false;

        /*
         * .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;
}
EXPORT_SYMBOL_GPL(__clk_is_enabled);

static struct clk *__clk_lookup_subtree(const char *name, struct clk *clk)
{
        struct clk *child;
        struct clk *ret;

        if (!strcmp(clk->name, name))
                return clk;

        hlist_for_each_entry(child, &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;

        if (!name)
                return NULL;

        /* search the 'proper' clk tree first */
        hlist_for_each_entry(root_clk, &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, &clk_orphan_list, child_node) {
                ret = __clk_lookup_subtree(name, root_clk);
                if (ret)
                        return ret;
        }

        return NULL;
}

/*
 * Helper for finding best parent to provide a given frequency. This can be used
 * directly as a determine_rate callback (e.g. for a mux), or from a more
 * complex clock that may combine a mux with other operations.
 */
long __clk_mux_determine_rate(struct clk_hw *hw, unsigned long rate,
                              unsigned long *best_parent_rate,
                              struct clk_hw **best_parent_p)
{
        struct clk *clk = hw->clk, *parent, *best_parent = NULL;
        int i, num_parents;
        unsigned long parent_rate, best = 0;

        /* if NO_REPARENT flag set, pass through to current parent */
        if (clk->flags & CLK_SET_RATE_NO_REPARENT) {
                parent = clk->parent;
                if (clk->flags & CLK_SET_RATE_PARENT)
                        best = __clk_round_rate(parent, rate);
                else if (parent)
                        best = __clk_get_rate(parent);
                else
                        best = __clk_get_rate(clk);
                goto out;
        }

        /* find the parent that can provide the fastest rate <= rate */
        num_parents = clk->num_parents;
        for (i = 0; i < num_parents; i++) {
                parent = clk_get_parent_by_index(clk, i);
                if (!parent)
                        continue;
                if (clk->flags & CLK_SET_RATE_PARENT)
                        parent_rate = __clk_round_rate(parent, rate);
                else
                        parent_rate = __clk_get_rate(parent);
                if (parent_rate <= rate && parent_rate > best) {
                        best_parent = parent;
                        best = parent_rate;
                }
        }

out:
        if (best_parent)
                *best_parent_p = best_parent->hw;
        *best_parent_rate = best;

        return best;
}
EXPORT_SYMBOL_GPL(__clk_mux_determine_rate);

/***        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);
}

/**
 * clk_unprepare - undo preparation of a clock source
 * @clk: the clk being unprepared
 *
 * clk_unprepare may sleep, which differentiates it from clk_disable.  In a
 * simple case, clk_unprepare can be used instead of clk_disable to gate a clk
 * if the operation may sleep.  One example is a clk which is accessed over
 * I2c.  In the complex case a clk gate operation may require a fast and a slow
 * part.  It is this reason that clk_unprepare and clk_disable are not mutually
 * exclusive.  In fact clk_disable must be called before clk_unprepare.
 */
void clk_unprepare(struct clk *clk)
{
        if (IS_ERR_OR_NULL(clk))
                return;

        clk_prepare_lock();
        __clk_unprepare(clk);
        clk_prepare_unlock();
}
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;
}

/**
 * clk_prepare - prepare a clock source
 * @clk: the clk being prepared
 *
 * clk_prepare may sleep, which differentiates it from clk_enable.  In a simple
 * case, clk_prepare can be used instead of clk_enable to ungate a clk if the
 * operation may sleep.  One example is a clk which is accessed over I2c.  In
 * the complex case a clk ungate operation may require a fast and a slow part.
 * It is this reason that clk_prepare and clk_enable are not mutually
 * exclusive.  In fact clk_prepare must be called before clk_enable.
 * Returns 0 on success, -EERROR otherwise.
 */
int clk_prepare(struct clk *clk)
{
        int ret;

        clk_prepare_lock();
        ret = __clk_prepare(clk);
        clk_prepare_unlock();

        return ret;
}
EXPORT_SYMBOL_GPL(clk_prepare);

static void __clk_disable(struct clk *clk)
{
        if (!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);
}

/**
 * clk_disable - gate a clock
 * @clk: the clk being gated
 *
 * clk_disable must not sleep, which differentiates it from clk_unprepare.  In
 * a simple case, clk_disable can be used instead of clk_unprepare to gate a
 * clk if the operation is fast and will never sleep.  One example is a
 * SoC-internal clk which is controlled via simple register writes.  In the
 * complex case a clk gate operation may require a fast and a slow part.  It is
 * this reason that clk_unprepare and clk_disable are not mutually exclusive.
 * In fact clk_disable must be called before clk_unprepare.
 */
void clk_disable(struct clk *clk)
{
        unsigned long flags;

        if (IS_ERR_OR_NULL(clk))
                return;

        flags = clk_enable_lock();
        __clk_disable(clk);
        clk_enable_unlock(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;
}

/**
 * clk_enable - ungate a clock
 * @clk: the clk being ungated
 *
 * clk_enable must not sleep, which differentiates it from clk_prepare.  In a
 * simple case, clk_enable can be used instead of clk_prepare to ungate a clk
 * if the operation will never sleep.  One example is a SoC-internal clk which
 * is controlled via simple register writes.  In the complex case a clk ungate
 * operation may require a fast and a slow part.  It is this reason that
 * clk_enable and clk_prepare are not mutually exclusive.  In fact clk_prepare
 * must be called before clk_enable.  Returns 0 on success, -EERROR
 * otherwise.
 */
int clk_enable(struct clk *clk)
{
        unsigned long flags;
        int ret;

        flags = clk_enable_lock();
        ret = __clk_enable(clk);
        clk_enable_unlock(flags);

        return ret;
}
EXPORT_SYMBOL_GPL(clk_enable);

/**
 * __clk_round_rate - round the given rate for a clk
 * @clk: round the rate of this clock
 * @rate: the rate which is to be rounded
 *
 * Caller must hold prepare_lock.  Useful for clk_ops such as .set_rate
 */
unsigned long __clk_round_rate(struct clk *clk, unsigned long rate)
{
        unsigned long parent_rate = 0;
        struct clk *parent;
        struct clk_hw *parent_hw;

        if (!clk)
                return 0;

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

        if (clk->ops->determine_rate) {
                parent_hw = parent ? parent->hw : NULL;
                return clk->ops->determine_rate(clk->hw, rate, &parent_rate,
                                                &parent_hw);
        } else if (clk->ops->round_rate)
                return clk->ops->round_rate(clk->hw, rate, &parent_rate);
        else if (clk->flags & CLK_SET_RATE_PARENT)
                return __clk_round_rate(clk->parent, rate);
        else
                return clk->rate;
}
EXPORT_SYMBOL_GPL(__clk_round_rate);

/**
 * clk_round_rate - round the given rate for a clk
 * @clk: the clk for which we are rounding a rate
 * @rate: the rate which is to be rounded
 *
 * Takes in a rate as input and rounds it to a rate that the clk can actually
 * use which is then returned.  If clk doesn't support round_rate operation
 * then the parent rate is returned.
 */
long clk_round_rate(struct clk *clk, unsigned long rate)
{
        unsigned long ret;

        clk_prepare_lock();
        ret = __clk_round_rate(clk, rate);
        clk_prepare_unlock();

        return ret;
}
EXPORT_SYMBOL_GPL(clk_round_rate);

/**
 * __clk_notify - call clk notifier chain
 * @clk: struct clk * that is changing rate
 * @msg: clk notifier type (see include/linux/clk.h)
 * @old_rate: old clk rate
 * @new_rate: new clk rate
 *
 * Triggers a notifier call chain on the clk rate-change notification
 * for 'clk'.  Passes a pointer to the struct clk and the previous
 * and current rates to the notifier callback.  Intended to be called by
 * internal clock code only.  Returns NOTIFY_DONE from the last driver
 * called if all went well, or NOTIFY_STOP or NOTIFY_BAD immediately if
 * a driver returns that.
 */
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;
}

/**
 * __clk_recalc_accuracies
 * @clk: first clk in the subtree
 *
 * Walks the subtree of clks starting with clk and recalculates accuracies as
 * it goes.  Note that if a clk does not implement the .recalc_accuracy
 * callback then it is assumed that the clock will take on the accuracy of it's
 * parent.
 *
 * Caller must hold prepare_lock.
 */
static void __clk_recalc_accuracies(struct clk *clk)
{
        unsigned long parent_accuracy = 0;
        struct clk *child;

        if (clk->parent)
                parent_accuracy = clk->parent->accuracy;

        if (clk->ops->recalc_accuracy)
                clk->accuracy = clk->ops->recalc_accuracy(clk->hw,
                                                          parent_accuracy);
        else
                clk->accuracy = parent_accuracy;

        hlist_for_each_entry(child, &clk->children, child_node)
                __clk_recalc_accuracies(child);
}

/**
 * clk_get_accuracy - return the accuracy of clk
 * @clk: the clk whose accuracy is being returned
 *
 * Simply returns the cached accuracy of the clk, unless
 * CLK_GET_ACCURACY_NOCACHE flag is set, which means a recalc_rate will be
 * issued.
 * If clk is NULL then returns 0.
 */
long clk_get_accuracy(struct clk *clk)
{
        unsigned long accuracy;

        clk_prepare_lock();
        if (clk && (clk->flags & CLK_GET_ACCURACY_NOCACHE))
                __clk_recalc_accuracies(clk);

        accuracy = __clk_get_accuracy(clk);
        clk_prepare_unlock();

        return accuracy;
}
EXPORT_SYMBOL_GPL(clk_get_accuracy);

static unsigned long clk_recalc(struct clk *clk, unsigned long parent_rate)
{
        if (clk->ops->recalc_rate)
                return clk->ops->recalc_rate(clk->hw, parent_rate);
        return parent_rate;
}

/**
 * __clk_recalc_rates
 * @clk: first clk in the subtree
 * @msg: notification type (see include/linux/clk.h)
 *
 * Walks the subtree of clks starting with clk and recalculates rates as it
 * goes.  Note that if a clk does not implement the .recalc_rate callback then
 * it is assumed that the clock will take on the rate of its parent.
 *
 * clk_recalc_rates also propagates the POST_RATE_CHANGE notification,
 * if necessary.
 *
 * Caller must hold prepare_lock.
 */
static void __clk_recalc_rates(struct clk *clk, unsigned long msg)
{
        unsigned long old_rate;
        unsigned long parent_rate = 0;
        struct clk *child;

        old_rate = clk->rate;

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

        clk->rate = clk_recalc(clk, 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, &clk->children, child_node)
                __clk_recalc_rates(child, msg);
}

/**
 * clk_get_rate - return the rate of clk
 * @clk: the clk whose rate is being returned
 *
 * Simply returns the cached rate of the clk, unless CLK_GET_RATE_NOCACHE flag
 * is set, which means a recalc_rate will be issued.
 * If clk is NULL then returns 0.
 */
unsigned long clk_get_rate(struct clk *clk)
{
        unsigned long rate;

        clk_prepare_lock();

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

        rate = __clk_get_rate(clk);
        clk_prepare_unlock();

        return rate;
}
EXPORT_SYMBOL_GPL(clk_get_rate);

static int clk_fetch_parent_index(struct clk *clk, struct clk *parent)
{
        int i;

        if (!clk->parents) {
                clk->parents = kcalloc(clk->num_parents,
                                        sizeof(struct clk *), GFP_KERNEL);
                if (!clk->parents)
                        return -ENOMEM;
        }

        /*
         * 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[i] == parent)
                        return i;

                if (clk->parents[i])
                        continue;

                if (!strcmp(clk->parent_names[i], parent->name)) {
                        clk->parents[i] = __clk_lookup(parent->name);
                        return i;
                }
        }

        return -EINVAL;
}

static void clk_reparent(struct clk *clk, struct clk *new_parent)
{
        hlist_del(&clk->child_node);

        if (new_parent) {
                /* avoid duplicate POST_RATE_CHANGE notifications */
                if (new_parent->new_child == clk)
                        new_parent->new_child = NULL;

                hlist_add_head(&clk->child_node, &new_parent->children);
        } else {
                hlist_add_head(&clk->child_node, &clk_orphan_list);
        }

        clk->parent = new_parent;
}

static struct clk *__clk_set_parent_before(struct clk *clk, struct clk *parent)
{
        unsigned long flags;
        struct clk *old_parent = clk->parent;

        /*
         * Migrate prepare state between parents and prevent race with
         * clk_enable().
         *
         * If the clock is not prepared, then a race with
         * clk_enable/disable() is impossible since we already have the
         * prepare lock (future calls to clk_enable() need to be preceded by
         * a clk_prepare()).
         *
         * If the clock is prepared, migrate the prepared state to the new
         * parent and also protect against a race with clk_enable() by
         * forcing the clock and the new parent on.  This ensures that all
         * future calls to clk_enable() are practically NOPs with respect to
         * hardware and software states.
         *
         * See also: Comment for clk_set_parent() below.
         */
        if (clk->prepare_count) {
                __clk_prepare(parent);
                clk_enable(parent);
                clk_enable(clk);
        }

        /* update the clk tree topology */
        flags = clk_enable_lock();
        clk_reparent(clk, parent);
        clk_enable_unlock(flags);

        return old_parent;
}

static void __clk_set_parent_after(struct clk *clk, struct clk *parent,
                struct clk *old_parent)
{
        /*
         * Finish the migration of prepare state and undo the changes done
         * for preventing a race with clk_enable().
         */
        if (clk->prepare_count) {
                clk_disable(clk);
                clk_disable(old_parent);
                __clk_unprepare(old_parent);
        }
}

static int __clk_set_parent(struct clk *clk, struct clk *parent, u8 p_index)
{
        unsigned long flags;
        int ret = 0;
        struct clk *old_parent;

        old_parent = __clk_set_parent_before(clk, parent);

        /* change clock input source */
        if (parent && clk->ops->set_parent)
                ret = clk->ops->set_parent(clk->hw, p_index);

        if (ret) {
                flags = clk_enable_lock();
                clk_reparent(clk, old_parent);
                clk_enable_unlock(flags);

                if (clk->prepare_count) {
                        clk_disable(clk);
                        clk_disable(parent);
                        __clk_unprepare(parent);
                }
                return ret;
        }

        __clk_set_parent_after(clk, parent, old_parent);

        return 0;
}

/**
 * __clk_speculate_rates
 * @clk: first clk in the subtree
 * @parent_rate: the "future" rate of clk's parent
 *
 * Walks the subtree of clks starting with clk, speculating rates as it
 * goes and firing off PRE_RATE_CHANGE notifications as necessary.
 *
 * Unlike clk_recalc_rates, clk_speculate_rates exists only for sending
 * pre-rate change notifications and returns early if no clks in the
 * subtree have subscribed to the notifications.  Note that if a clk does not
 * implement the .recalc_rate callback then it is assumed that the clock will
 * take on the rate of its parent.
 *
 * Caller must hold prepare_lock.
 */
static int __clk_speculate_rates(struct clk *clk, unsigned long parent_rate)
{
        struct clk *child;
        unsigned long new_rate;
        int ret = NOTIFY_DONE;

        new_rate = clk_recalc(clk, parent_rate);

        /* abort rate change if a driver returns NOTIFY_BAD or NOTIFY_STOP */
        if (clk->notifier_count)
                ret = __clk_notify(clk, PRE_RATE_CHANGE, clk->rate, new_rate);

        if (ret & NOTIFY_STOP_MASK) {
                pr_debug("%s: clk notifier callback for clock %s aborted with error %d\n",
                                __func__, clk->name, ret);
                goto out;
        }

        hlist_for_each_entry(child, &clk->children, child_node) {
                ret = __clk_speculate_rates(child, new_rate);
                if (ret & NOTIFY_STOP_MASK)
                        break;
        }

out:
        return ret;
}

static void clk_calc_subtree(struct clk *clk, unsigned long new_rate,
                             struct clk *new_parent, u8 p_index)
{
        struct clk *child;

        clk->new_rate = new_rate;
        clk->new_parent = new_parent;
        clk->new_parent_index = p_index;
        /* include clk in new parent's PRE_RATE_CHANGE notifications */
        clk->new_child = NULL;
        if (new_parent && new_parent != clk->parent)
                new_parent->new_child = clk;

        hlist_for_each_entry(child, &clk->children, child_node) {
                child->new_rate = clk_recalc(child, new_rate);
                clk_calc_subtree(child, child->new_rate, NULL, 0);
        }
}

/*
 * 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;
        struct clk *old_parent, *parent;
        struct clk_hw *parent_hw;
        unsigned long best_parent_rate = 0;
        unsigned long new_rate;
        int p_index = 0;

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

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

        /* find the closest rate and parent clk/rate */
        if (clk->ops->determine_rate) {
                parent_hw = parent ? parent->hw : NULL;
                new_rate = clk->ops->determine_rate(clk->hw, rate,
                                                    &best_parent_rate,
                                                    &parent_hw);
                parent = parent_hw->clk;
        } else if (clk->ops->round_rate) {
                new_rate = clk->ops->round_rate(clk->hw, rate,
                                                &best_parent_rate);
        } else if (!parent || !(clk->flags & CLK_SET_RATE_PARENT)) {
                /* pass-through clock without adjustable parent */
                clk->new_rate = clk->rate;
                return NULL;
        } else {
                /* pass-through clock with adjustable parent */
                top = clk_calc_new_rates(parent, rate);
                new_rate = parent->new_rate;
                goto out;
        }

        /* some clocks must be gated to change parent */
        if (parent != old_parent &&
            (clk->flags & CLK_SET_PARENT_GATE) && clk->prepare_count) {
                pr_debug("%s: %s not gated but wants to reparent\n",
                         __func__, clk->name);
                return NULL;
        }

        /* try finding the new parent index */
        if (parent) {
                p_index = clk_fetch_parent_index(clk, parent);
                if (p_index < 0) {
                        pr_debug("%s: clk %s can not be parent of clk %s\n",
                                 __func__, parent->name, clk->name);
                        return NULL;
                }
        }

        if ((clk->flags & CLK_SET_RATE_PARENT) && parent &&
            best_parent_rate != parent->rate)
                top = clk_calc_new_rates(parent, best_parent_rate);

out:
        clk_calc_subtree(clk, new_rate, parent, p_index);

        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 clk *child, *tmp_clk, *fail_clk = NULL;
        int ret = NOTIFY_DONE;

        if (clk->rate == clk->new_rate)
                return NULL;

        if (clk->notifier_count) {
                ret = __clk_notify(clk, event, clk->rate, clk->new_rate);
                if (ret & NOTIFY_STOP_MASK)
                        fail_clk = clk;
        }

        hlist_for_each_entry(child, &clk->children, child_node) {
                /* Skip children who will be reparented to another clock */
                if (child->new_parent && child->new_parent != clk)
                        continue;
                tmp_clk = clk_propagate_rate_change(child, event);
                if (tmp_clk)
                        fail_clk = tmp_clk;
        }

        /* handle the new child who might not be in clk->children yet */
        if (clk->new_child) {
                tmp_clk = clk_propagate_rate_change(clk->new_child, event);
                if (tmp_clk)
                        fail_clk = tmp_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;
        struct hlist_node *tmp;
        unsigned long old_rate;
        unsigned long best_parent_rate = 0;
        bool skip_set_rate = false;
        struct clk *old_parent;

        old_rate = clk->rate;

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

        if (clk->new_parent && clk->new_parent != clk->parent) {
                old_parent = __clk_set_parent_before(clk, clk->new_parent);

                if (clk->ops->set_rate_and_parent) {
                        skip_set_rate = true;
                        clk->ops->set_rate_and_parent(clk->hw, clk->new_rate,
                                        best_parent_rate,
                                        clk->new_parent_index);
                } else if (clk->ops->set_parent) {
                        clk->ops->set_parent(clk->hw, clk->new_parent_index);
                }

                __clk_set_parent_after(clk, clk->new_parent, old_parent);
        }

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

        clk->rate = clk_recalc(clk, best_parent_rate);

        if (clk->notifier_count && old_rate != clk->rate)
                __clk_notify(clk, POST_RATE_CHANGE, old_rate, clk->rate);

        /*
         * Use safe iteration, as change_rate can actually swap parents
         * for certain clock types.
         */
        hlist_for_each_entry_safe(child, tmp, &clk->children, child_node) {
                /* Skip children who will be reparented to another clock */
                if (child->new_parent && child->new_parent != clk)
                        continue;
                clk_change_rate(child);
        }

        /* handle the new child who might not be in clk->children yet */
        if (clk->new_child)
                clk_change_rate(clk->new_child);
}

/**
 * clk_set_rate - specify a new rate for clk
 * @clk: the clk whose rate is being changed
 * @rate: the new rate for clk
 *
 * In the simplest case clk_set_rate will only adjust the rate of clk.
 *
 * Setting the CLK_SET_RATE_PARENT flag allows the rate change operation to
 * propagate up to clk's parent; whether or not this happens depends on the
 * outcome of clk's .round_rate implementation.  If *parent_rate is unchanged
 * after calling .round_rate then upstream parent propagation is ignored.  If
 * *parent_rate comes back with a new rate for clk's parent then we propagate
 * up to clk's parent and set its rate.  Upward propagation will continue
 * until either a clk does not support the CLK_SET_RATE_PARENT flag or
 * .round_rate stops requesting changes to clk's parent_rate.
 *
 * Rate changes are accomplished via tree traversal that also recalculates the
 * rates for the clocks and fires off POST_RATE_CHANGE notifiers.
 *
 * Returns 0 on success, -EERROR otherwise.
 */
int clk_set_rate(struct clk *clk, unsigned long rate)
{
        struct clk *top, *fail_clk;
        int ret = 0;

        if (!clk)
                return 0;

        /* prevent racing with updates to the clock topology */
        clk_prepare_lock();

        /* bail early if nothing to do */
        if (rate == clk_get_rate(clk))
                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_debug("%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);

out:
        clk_prepare_unlock();

        return ret;
}
EXPORT_SYMBOL_GPL(clk_set_rate);

/**
 * clk_get_parent - return the parent of a clk
 * @clk: the clk whose parent gets returned
 *
 * Simply returns clk->parent.  Returns NULL if clk is NULL.
 */
struct clk *clk_get_parent(struct clk *clk)
{
        struct clk *parent;

        clk_prepare_lock();
        parent = __clk_get_parent(clk);
        clk_prepare_unlock();

        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))
                        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 =
                        kcalloc(clk->num_parents, sizeof(struct clk *),
                                        GFP_KERNEL);

        ret = clk_get_parent_by_index(clk, index);

out:
        return ret;
}

void __clk_reparent(struct clk *clk, struct clk *new_parent)
{
        clk_reparent(clk, new_parent);
        __clk_recalc_accuracies(clk);
        __clk_recalc_rates(clk, POST_RATE_CHANGE);
}

/**
 * clk_set_parent - switch the parent of a mux clk
 * @clk: the mux clk whose input we are switching
 * @parent: the new input to clk
 *
 * Re-parent clk to use parent as its new input source.  If clk is in
 * prepared state, the clk will get enabled for the duration of this call. If
 * that's not acceptable for a specific clk (Eg: the consumer can't handle
 * that, the reparenting is glitchy in hardware, etc), use the
 * CLK_SET_PARENT_GATE flag to allow reparenting only when clk is unprepared.
 *
 * After successfully changing clk's parent clk_set_parent will update the
 * clk topology, sysfs topology and propagate rate recalculation via
 * __clk_recalc_rates.
 *
 * Returns 0 on success, -EERROR otherwise.
 */
int clk_set_parent(struct clk *clk, struct clk *parent)
{
        int ret = 0;
        int p_index = 0;
        unsigned long p_rate = 0;

        if (!clk)
                return 0;

        /* verify ops for for multi-parent clks */
        if ((clk->num_parents > 1) && (!clk->ops->set_parent))
                return -ENOSYS;

        /* prevent racing with updates to the clock topology */
        clk_prepare_lock();

        if (clk->parent == parent)
                goto out;

        /* check that we are allowed to re-parent if the clock is in use */
        if ((clk->flags & CLK_SET_PARENT_GATE) && clk->prepare_count) {
                ret = -EBUSY;
                goto out;
        }

        /* try finding the new parent index */
        if (parent) {
                p_index = clk_fetch_parent_index(clk, parent);
                p_rate = parent->rate;
                if (p_index < 0) {
                        pr_debug("%s: clk %s can not be parent of clk %s\n",
                                        __func__, parent->name, clk->name);
                        ret = p_index;
                        goto out;
                }
        }

        /* propagate PRE_RATE_CHANGE notifications */
        ret = __clk_speculate_rates(clk, p_rate);

        /* abort if a driver objects */
        if (ret & NOTIFY_STOP_MASK)
                goto out;

        /* do the re-parent */
        ret = __clk_set_parent(clk, parent, p_index);

        /* propagate rate an accuracy recalculation accordingly */
        if (ret) {
                __clk_recalc_rates(clk, ABORT_RATE_CHANGE);
        } else {
                __clk_recalc_rates(clk, POST_RATE_CHANGE);
                __clk_recalc_accuracies(clk);
        }

out:
        clk_prepare_unlock();

        return ret;
}
EXPORT_SYMBOL_GPL(clk_set_parent);

/**
 * clk_set_phase - adjust the phase shift of a clock signal
 * @clk: clock signal source
 * @degrees: number of degrees the signal is shifted
 *
 * Shifts the phase of a clock signal by the specified
 * degrees. Returns 0 on success, -EERROR otherwise.
 *
 * This function makes no distinction about the input or reference
 * signal that we adjust the clock signal phase against. For example
 * phase locked-loop clock signal generators we may shift phase with
 * respect to feedback clock signal input, but for other cases the
 * clock phase may be shifted with respect to some other, unspecified
 * signal.
 *
 * Additionally the concept of phase shift does not propagate through
 * the clock tree hierarchy, which sets it apart from clock rates and
 * clock accuracy. A parent clock phase attribute does not have an
 * impact on the phase attribute of a child clock.
 */
int clk_set_phase(struct clk *clk, int degrees)
{
        int ret = 0;

        if (!clk)
                goto out;

        /* sanity check degrees */
        degrees %= 360;
        if (degrees < 0)
                degrees += 360;

        clk_prepare_lock();

        if (!clk->ops->set_phase)
                goto out_unlock;

        ret = clk->ops->set_phase(clk->hw, degrees);

        if (!ret)
                clk->phase = degrees;

out_unlock:
        clk_prepare_unlock();

out:
        return ret;
}

/**
 * clk_get_phase - return the phase shift of a clock signal
 * @clk: clock signal source
 *
 * Returns the phase shift of a clock node in degrees, otherwise returns
 * -EERROR.
 */
int clk_get_phase(struct clk *clk)
{
        int ret = 0;

        if (!clk)
                goto out;

        clk_prepare_lock();
        ret = clk->phase;
        clk_prepare_unlock();

out:
        return ret;
}

/**
 * __clk_init - initialize the data structures in a struct clk
 * @dev:        device initializing this clk, placeholder for now
 * @clk:        clk being initialized
 *
 * Initializes the lists in struct clk, queries the hardware for the
 * parent and rate and sets them both.
 */
int __clk_init(struct device *dev, struct clk *clk)
{
        int i, ret = 0;
        struct clk *orphan;
        struct hlist_node *tmp2;

        if (!clk)
                return -EINVAL;

        clk_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->determine_rate) &&
              clk->ops->recalc_rate)) {
                pr_warning("%s: %s must implement .round_rate or .determine_rate in addition to .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;
        }

        if (clk->ops->set_rate_and_parent &&
                        !(clk->ops->set_parent && clk->ops->set_rate)) {
                pr_warn("%s: %s must implement .set_parent & .set_rate\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 = kcalloc(clk->num_parents, sizeof(struct clk *),
                                        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 accuracy.  The preferred method is to use
         * .recalc_accuracy. For simple clocks and lazy developers the default
         * fallback is to use the parent's accuracy.  If a clock doesn't have a
         * parent (or is orphaned) then accuracy is set to zero (perfect
         * clock).
         */
        if (clk->ops->recalc_accuracy)
                clk->accuracy = clk->ops->recalc_accuracy(clk->hw,
                                        __clk_get_accuracy(clk->parent));
        else if (clk->parent)
                clk->accuracy = clk->parent->accuracy;
        else
                clk->accuracy = 0;

        /*
         * Set clk's phase.
         * Since a phase is by definition relative to its parent, just
         * query the current clock phase, or just assume it's in phase.
         */
        if (clk->ops->get_phase)
                clk->phase = clk->ops->get_phase(clk->hw);
        else
                clk->phase = 0;

        /*
         * 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;

        clk_debug_register(clk);
        /*
         * walk the list of orphan clocks and reparent any that are children of
         * this clock
         */
        hlist_for_each_entry_safe(orphan, tmp2, &clk_orphan_list, child_node) {
                if (orphan->num_parents && orphan->ops->get_parent) {
                        i = orphan->ops->get_parent(orphan->hw);
                        if (!strcmp(clk->name, orphan->parent_names[i]))
                                __clk_reparent(orphan, clk);
                        continue;
                }

                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 its use is discouraged.
         */
        if (clk->ops->init)
                clk->ops->init(clk->hw);

        kref_init(&clk->ref);
out:
        clk_prepare_unlock();

        return ret;
}

/**
 * __clk_register - register a clock and return a cookie.
 *
 * Same as clk_register, except that the .clk field inside hw shall point to a
 * preallocated (generally statically allocated) struct clk. None of the fields
 * of the struct clk need to be initialized.
 *
 * The data pointed to by .init and .clk field shall NOT be marked as init
 * data.
 *
 * __clk_register is only exposed via clk-private.h and is intended for use with
 * very large numbers of clocks that need to be statically initialized.  It is
 * a layering violation to include clk-private.h from any code which implements
 * a clock's .ops; as such any statically initialized clock data MUST be in a
 * separate C file from the logic that implements its operations.  Returns 0
 * on success, otherwise an error code.
 */
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;
        if (dev && dev->driver)
                clk->owner = dev->driver->owner;
        else
                clk->owner = NULL;

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

        return clk;
}
EXPORT_SYMBOL_GPL(__clk_register);

/**
 * clk_register - allocate a new clock, register it and return an opaque cookie
 * @dev: device that is registering this clock
 * @hw: link to hardware-specific clock data
 *
 * clk_register is the primary interface for populating the clock tree with new
 * clock nodes.  It returns a pointer to the newly allocated struct clk which
 * cannot be dereferenced by driver code but may be used in conjuction with the
 * rest of the clock API.  In the event of an error clk_register will return an
 * error code; drivers must test for an error code after calling 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;
        if (dev && dev->driver)
                clk->owner = dev->driver->owner;
        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 = kcalloc(clk->num_parents, sizeof(char *),
                                        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);

/*
 * Free memory allocated for a clock.
 * Caller must hold prepare_lock.
 */
static void __clk_release(struct kref *ref)
{
        struct clk *clk = container_of(ref, struct clk, ref);
        int i = clk->num_parents;

        kfree(clk->parents);
        while (--i >= 0)
                kfree(clk->parent_names[i]);

        kfree(clk->parent_names);
        kfree(clk->name);
        kfree(clk);
}

/*
 * Empty clk_ops for unregistered clocks. These are used temporarily
 * after clk_unregister() was called on a clock and until last clock
 * consumer calls clk_put() and the struct clk object is freed.
 */
static int clk_nodrv_prepare_enable(struct clk_hw *hw)
{
        return -ENXIO;
}

static void clk_nodrv_disable_unprepare(struct clk_hw *hw)
{
        WARN_ON_ONCE(1);
}

static int clk_nodrv_set_rate(struct clk_hw *hw, unsigned long rate,
                                        unsigned long parent_rate)
{
        return -ENXIO;
}

static int clk_nodrv_set_parent(struct clk_hw *hw, u8 index)
{
        return -ENXIO;
}

static const struct clk_ops clk_nodrv_ops = {
        .enable         = clk_nodrv_prepare_enable,
        .disable        = clk_nodrv_disable_unprepare,
        .prepare        = clk_nodrv_prepare_enable,
        .unprepare      = clk_nodrv_disable_unprepare,
        .set_rate       = clk_nodrv_set_rate,
        .set_parent     = clk_nodrv_set_parent,
};

/**
 * clk_unregister - unregister a currently registered clock
 * @clk: clock to unregister
 */
void clk_unregister(struct clk *clk)
{
        unsigned long flags;

        if (!clk || WARN_ON_ONCE(IS_ERR(clk)))
                return;

        clk_debug_unregister(clk);

        clk_prepare_lock();

        if (clk->ops == &clk_nodrv_ops) {
                pr_err("%s: unregistered clock: %s\n", __func__, clk->name);
                return;
        }
        /*
         * Assign empty clock ops for consumers that might still hold
         * a reference to this clock.
         */
        flags = clk_enable_lock();
        clk->ops = &clk_nodrv_ops;
        clk_enable_unlock(flags);

        if (!hlist_empty(&clk->children)) {
                struct clk *child;
                struct hlist_node *t;

                /* Reparent all children to the orphan list. */
                hlist_for_each_entry_safe(child, t, &clk->children, child_node)
                        clk_set_parent(child, NULL);
        }

        hlist_del_init(&clk->child_node);

        if (clk->prepare_count)
                pr_warn("%s: unregistering prepared clock: %s\n",
                                        __func__, clk->name);
        kref_put(&clk->ref, __clk_release);

        clk_prepare_unlock();
}
EXPORT_SYMBOL_GPL(clk_unregister);

static void devm_clk_release(struct device *dev, void *res)
{
        clk_unregister(*(struct clk **)res);
}

/**
 * devm_clk_register - resource managed clk_register()
 * @dev: device that is registering this clock
 * @hw: link to hardware-specific clock data
 *
 * Managed clk_register(). Clocks returned from this function are
 * automatically clk_unregister()ed on driver detach. See clk_register() for
 * more information.
 */
struct clk *devm_clk_register(struct device *dev, struct clk_hw *hw)
{
        struct clk *clk;
        struct clk **clkp;

        clkp = devres_alloc(devm_clk_release, sizeof(*clkp), GFP_KERNEL);
        if (!clkp)
                return ERR_PTR(-ENOMEM);

        clk = clk_register(dev, hw);
        if (!IS_ERR(clk)) {
                *clkp = clk;
                devres_add(dev, clkp);
        } else {
                devres_free(clkp);
        }

        return clk;
}
EXPORT_SYMBOL_GPL(devm_clk_register);

static int devm_clk_match(struct device *dev, void *res, void *data)
{
        struct clk *c = res;
        if (WARN_ON(!c))
                return 0;
        return c == data;
}

/**
 * devm_clk_unregister - resource managed clk_unregister()
 * @clk: clock to unregister
 *
 * Deallocate a clock allocated with devm_clk_register(). Normally
 * this function will not need to be called and the resource management
 * code will ensure that the resource is freed.
 */
void devm_clk_unregister(struct device *dev, struct clk *clk)
{
        WARN_ON(devres_release(dev, devm_clk_release, devm_clk_match, clk));
}
EXPORT_SYMBOL_GPL(devm_clk_unregister);

/*
 * clkdev helpers
 */
int __clk_get(struct clk *clk)
{
        if (clk) {
                if (!try_module_get(clk->owner))
                        return 0;

                kref_get(&clk->ref);
        }
        return 1;
}

void __clk_put(struct clk *clk)
{
        struct module *owner;

        if (!clk || WARN_ON_ONCE(IS_ERR(clk)))
                return;

        clk_prepare_lock();
        owner = clk->owner;
        kref_put(&clk->ref, __clk_release);
        clk_prepare_unlock();

        module_put(owner);
}

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

/**
 * clk_notifier_register - add a clk rate change notifier
 * @clk: struct clk * to watch
 * @nb: struct notifier_block * with callback info
 *
 * Request notification when clk's rate changes.  This uses an SRCU
 * notifier because we want it to block and notifier unregistrations are
 * uncommon.  The callbacks associated with the notifier must not
 * re-enter into the clk framework by calling any top-level clk APIs;
 * this will cause a nested prepare_lock mutex.
 *
 * In all notification cases cases (pre, post and abort rate change) the
 * original clock rate is passed to the callback via struct
 * clk_notifier_data.old_rate and the new frequency is passed via struct
 * clk_notifier_data.new_rate.
 *
 * clk_notifier_register() must be called from non-atomic context.
 * Returns -EINVAL if called with null arguments, -ENOMEM upon
 * allocation failure; otherwise, passes along the return value of
 * srcu_notifier_chain_register().
 */
int clk_notifier_register(struct clk *clk, struct notifier_block *nb)
{
        struct clk_notifier *cn;
        int ret = -ENOMEM;

        if (!clk || !nb)
                return -EINVAL;

        clk_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:
        clk_prepare_unlock();

        return ret;
}
EXPORT_SYMBOL_GPL(clk_notifier_register);

/**
 * clk_notifier_unregister - remove a clk rate change notifier
 * @clk: struct clk *
 * @nb: struct notifier_block * with callback info
 *
 * Request no further notification for changes to 'clk' and frees memory
 * allocated in clk_notifier_register.
 *
 * Returns -EINVAL if called with null arguments; otherwise, passes
 * along the return value of srcu_notifier_chain_unregister().
 */
int clk_notifier_unregister(struct clk *clk, struct notifier_block *nb)
{
        struct clk_notifier *cn = NULL;
        int ret = -EINVAL;

        if (!clk || !nb)
                return -EINVAL;

        clk_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);
                        list_del(&cn->node);
                        kfree(cn);
                }

        } else {
                ret = -ENOENT;
        }

        clk_prepare_unlock();

        return ret;
}
EXPORT_SYMBOL_GPL(clk_notifier_unregister);

#ifdef CONFIG_OF
/**
 * struct of_clk_provider - Clock provider registration structure
 * @link: Entry in global list of clock providers
 * @node: Pointer to device tree node of clock provider
 * @get: Get clock callback.  Returns NULL or a struct clk for the
 *       given clock specifier
 * @data: context pointer to be passed into @get callback
 */
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 const struct of_device_id __clk_of_table_sentinel
        __used __section(__clk_of_table_end);

static LIST_HEAD(of_clk_providers);
static DEFINE_MUTEX(of_clk_mutex);

/* of_clk_provider list locking helpers */
void of_clk_lock(void)
{
        mutex_lock(&of_clk_mutex);
}

void of_clk_unlock(void)
{
        mutex_unlock(&of_clk_mutex);
}

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);

/**
 * of_clk_add_provider() - Register a clock provider for a node
 * @np: Device node pointer associated with clock provider
 * @clk_src_get: callback for decoding clock
 * @data: context pointer for @clk_src_get callback.
 */
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;
        int ret;

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

        ret = of_clk_set_defaults(np, true);
        if (ret < 0)
                of_clk_del_provider(np);

        return ret;
}
EXPORT_SYMBOL_GPL(of_clk_add_provider);

/**
 * of_clk_del_provider() - Remove a previously registered clock provider
 * @np: Device node pointer associated with clock provider
 */
void of_clk_del_provider(struct device_node *np)
{
        struct of_clk_provider *cp;

        mutex_lock(&of_clk_mutex);
        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_mutex);
}
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(-EPROBE_DEFER);

        /* Check if we have such a provider in our array */
        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;
        }

        return clk;
}

struct clk *of_clk_get_from_provider(struct of_phandle_args *clkspec)
{
        struct clk *clk;

        mutex_lock(&of_clk_mutex);
        clk = __of_clk_get_from_provider(clkspec);
        mutex_unlock(&of_clk_mutex);

        return clk;
}

int of_clk_get_parent_count(struct device_node *np)
{
        return of_count_phandle_with_args(np, "clocks", "#clock-cells");
}
EXPORT_SYMBOL_GPL(of_clk_get_parent_count);

const char *of_clk_get_parent_name(struct device_node *np, int index)
{
        struct of_phandle_args clkspec;
        struct property *prop;
        const char *clk_name;
        const __be32 *vp;
        u32 pv;
        int rc;
        int count;

        if (index < 0)
                return NULL;

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

        index = clkspec.args_count ? clkspec.args[0] : 0;
        count = 0;

        /* if there is an indices property, use it to transfer the index
         * specified into an array offset for the clock-output-names property.
         */
        of_property_for_each_u32(clkspec.np, "clock-indices", prop, vp, pv) {
                if (index == pv) {
                        index = count;
                        break;
                }
                count++;
        }

        if (of_property_read_string_index(clkspec.np, "clock-output-names",
                                          index,
                                          &clk_name) < 0)
                clk_name = clkspec.np->name;

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

struct clock_provider {
        of_clk_init_cb_t clk_init_cb;
        struct device_node *np;
        struct list_head node;
};

static LIST_HEAD(clk_provider_list);

/*
 * This function looks for a parent clock. If there is one, then it
 * checks that the provider for this parent clock was initialized, in
 * this case the parent clock will be ready.
 */
static int parent_ready(struct device_node *np)
{
        int i = 0;

        while (true) {
                struct clk *clk = of_clk_get(np, i);

                /* this parent is ready we can check the next one */
                if (!IS_ERR(clk)) {
                        clk_put(clk);
                        i++;
                        continue;
                }

                /* at least one parent is not ready, we exit now */
                if (PTR_ERR(clk) == -EPROBE_DEFER)
                        return 0;

                /*
                 * Here we make assumption that the device tree is
                 * written correctly. So an error means that there is
                 * no more parent. As we didn't exit yet, then the
                 * previous parent are ready. If there is no clock
                 * parent, no need to wait for them, then we can
                 * consider their absence as being ready
                 */
                return 1;
        }
}

/**
 * of_clk_init() - Scan and init clock providers from the DT
 * @matches: array of compatible values and init functions for providers.
 *
 * This function scans the device tree for matching clock providers
 * and calls their initialization functions. It also does it by trying
 * to follow the dependencies.
 */
void __init of_clk_init(const struct of_device_id *matches)
{
        const struct of_device_id *match;
        struct device_node *np;
        struct clock_provider *clk_provider, *next;
        bool is_init_done;
        bool force = false;

        if (!matches)
                matches = &__clk_of_table;

        /* First prepare the list of the clocks providers */
        for_each_matching_node_and_match(np, matches, &match) {
                struct clock_provider *parent =
                        kzalloc(sizeof(struct clock_provider),  GFP_KERNEL);

                parent->clk_init_cb = match->data;
                parent->np = np;
                list_add_tail(&parent->node, &clk_provider_list);
        }

        while (!list_empty(&clk_provider_list)) {
                is_init_done = false;
                list_for_each_entry_safe(clk_provider, next,
                                        &clk_provider_list, node) {
                        if (force || parent_ready(clk_provider->np)) {

                                clk_provider->clk_init_cb(clk_provider->np);
                                of_clk_set_defaults(clk_provider->np, true);

                                list_del(&clk_provider->node);
                                kfree(clk_provider);
                                is_init_done = true;
                        }
                }

                /*
                 * We didn't manage to initialize any of the
                 * remaining providers during the last loop, so now we
                 * initialize all the remaining ones unconditionally
                 * in case the clock parent was not mandatory
                 */
                if (!is_init_done)
                        force = true;
        }
}
#endif