// SPDX-License-Identifier: GPL-2.0
/*
 * Copyright (C) 2010-2011 Canonical Ltd <jeremy.kerr@canonical.com>
 * Copyright (C) 2011-2012 Linaro Ltd <mturquette@linaro.org>
 *
 * Standard functionality for the common clock API.  See Documentation/driver-api/clk.rst
 */

#include <linux/clk.h>
#include <linux/clk-provider.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/pm_runtime.h>
#include <linux/sched.h>
#include <linux/clkdev.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);

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

/***    private data structures    ***/

struct clk_parent_map {
        const struct clk_hw     *hw;
        struct clk_core         *core;
        const char              *fw_name;
        const char              *name;
        int                     index;
};

struct clk_core {
        const char              *name;
        const struct clk_ops    *ops;
        struct clk_hw           *hw;
        struct module           *owner;
        struct device           *dev;
        struct device_node      *of_node;
        struct clk_core         *parent;
        struct clk_parent_map   *parents;
        u8                      num_parents;
        u8                      new_parent_index;
        unsigned long           rate;
        unsigned long           req_rate;
        unsigned long           new_rate;
        struct clk_core         *new_parent;
        struct clk_core         *new_child;
        unsigned long           flags;
        bool                    orphan;
        bool                    rpm_enabled;
        unsigned int            enable_count;
        unsigned int            prepare_count;
        unsigned int            protect_count;
        unsigned long           min_rate;
        unsigned long           max_rate;
        unsigned long           accuracy;
        int                     phase;
        struct clk_duty         duty;
        struct hlist_head       children;
        struct hlist_node       child_node;
        struct hlist_head       clks;
        unsigned int            notifier_count;
#ifdef CONFIG_DEBUG_FS
        struct dentry           *dentry;
        struct hlist_node       debug_node;
#endif
        struct kref             ref;
};

#define CREATE_TRACE_POINTS
#include <trace/events/clk.h>

struct clk {
        struct clk_core *core;
        struct device *dev;
        const char *dev_id;
        const char *con_id;
        unsigned long min_rate;
        unsigned long max_rate;
        unsigned int exclusive_count;
        struct hlist_node clks_node;
};

/***           runtime pm          ***/
static int clk_pm_runtime_get(struct clk_core *core)
{
        int ret;

        if (!core->rpm_enabled)
                return 0;

        ret = pm_runtime_get_sync(core->dev);
        if (ret < 0) {
                pm_runtime_put_noidle(core->dev);
                return ret;
        }
        return 0;
}

static void clk_pm_runtime_put(struct clk_core *core)
{
        if (!core->rpm_enabled)
                return;

        pm_runtime_put_sync(core->dev);
}

/***           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)
        __acquires(enable_lock)
{
        unsigned long flags;

        /*
         * On UP systems, spin_trylock_irqsave() always returns true, even if
         * we already hold the lock. So, in that case, we rely only on
         * reference counting.
         */
        if (!IS_ENABLED(CONFIG_SMP) ||
            !spin_trylock_irqsave(&enable_lock, flags)) {
                if (enable_owner == current) {
                        enable_refcnt++;
                        __acquire(enable_lock);
                        if (!IS_ENABLED(CONFIG_SMP))
                                local_save_flags(flags);
                        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)
        __releases(enable_lock)
{
        WARN_ON_ONCE(enable_owner != current);
        WARN_ON_ONCE(enable_refcnt == 0);

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

static bool clk_core_rate_is_protected(struct clk_core *core)
{
        return core->protect_count;
}

static bool clk_core_is_prepared(struct clk_core *core)
{
        bool ret = false;

        /*
         * .is_prepared is optional for clocks that can prepare
         * fall back to software usage counter if it is missing
         */
        if (!core->ops->is_prepared)
                return core->prepare_count;

        if (!clk_pm_runtime_get(core)) {
                ret = core->ops->is_prepared(core->hw);
                clk_pm_runtime_put(core);
        }

        return ret;
}

static bool clk_core_is_enabled(struct clk_core *core)
{
        bool ret = false;

        /*
         * .is_enabled is only mandatory for clocks that gate
         * fall back to software usage counter if .is_enabled is missing
         */
        if (!core->ops->is_enabled)
                return core->enable_count;

        /*
         * Check if clock controller's device is runtime active before
         * calling .is_enabled callback. If not, assume that clock is
         * disabled, because we might be called from atomic context, from
         * which pm_runtime_get() is not allowed.
         * This function is called mainly from clk_disable_unused_subtree,
         * which ensures proper runtime pm activation of controller before
         * taking enable spinlock, but the below check is needed if one tries
         * to call it from other places.
         */
        if (core->rpm_enabled) {
                pm_runtime_get_noresume(core->dev);
                if (!pm_runtime_active(core->dev)) {
                        ret = false;
                        goto done;
                }
        }

        ret = core->ops->is_enabled(core->hw);
done:
        if (core->rpm_enabled)
                pm_runtime_put(core->dev);

        return ret;
}

/***    helper functions   ***/

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

const char *clk_hw_get_name(const struct clk_hw *hw)
{
        return hw->core->name;
}
EXPORT_SYMBOL_GPL(clk_hw_get_name);

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

unsigned int clk_hw_get_num_parents(const struct clk_hw *hw)
{
        return hw->core->num_parents;
}
EXPORT_SYMBOL_GPL(clk_hw_get_num_parents);

struct clk_hw *clk_hw_get_parent(const struct clk_hw *hw)
{
        return hw->core->parent ? hw->core->parent->hw : NULL;
}
EXPORT_SYMBOL_GPL(clk_hw_get_parent);

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

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

        hlist_for_each_entry(child, &core->children, child_node) {
                ret = __clk_lookup_subtree(name, child);
                if (ret)
                        return ret;
        }

        return NULL;
}

static struct clk_core *clk_core_lookup(const char *name)
{
        struct clk_core *root_clk;
        struct clk_core *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;
}

#ifdef CONFIG_OF
static int of_parse_clkspec(const struct device_node *np, int index,
                            const char *name, struct of_phandle_args *out_args);
static struct clk_hw *
of_clk_get_hw_from_clkspec(struct of_phandle_args *clkspec);
#else
static inline int of_parse_clkspec(const struct device_node *np, int index,
                                   const char *name,
                                   struct of_phandle_args *out_args)
{
        return -ENOENT;
}
static inline struct clk_hw *
of_clk_get_hw_from_clkspec(struct of_phandle_args *clkspec)
{
        return ERR_PTR(-ENOENT);
}
#endif

/**
 * clk_core_get - Find the clk_core parent of a clk
 * @core: clk to find parent of
 * @p_index: parent index to search for
 *
 * This is the preferred method for clk providers to find the parent of a
 * clk when that parent is external to the clk controller. The parent_names
 * array is indexed and treated as a local name matching a string in the device
 * node's 'clock-names' property or as the 'con_id' matching the device's
 * dev_name() in a clk_lookup. This allows clk providers to use their own
 * namespace instead of looking for a globally unique parent string.
 *
 * For example the following DT snippet would allow a clock registered by the
 * clock-controller@c001 that has a clk_init_data::parent_data array
 * with 'xtal' in the 'name' member to find the clock provided by the
 * clock-controller@f00abcd without needing to get the globally unique name of
 * the xtal clk.
 *
 *      parent: clock-controller@f00abcd {
 *              reg = <0xf00abcd 0xabcd>;
 *              #clock-cells = <0>;
 *      };
 *
 *      clock-controller@c001 {
 *              reg = <0xc001 0xf00d>;
 *              clocks = <&parent>;
 *              clock-names = "xtal";
 *              #clock-cells = <1>;
 *      };
 *
 * Returns: -ENOENT when the provider can't be found or the clk doesn't
 * exist in the provider or the name can't be found in the DT node or
 * in a clkdev lookup. NULL when the provider knows about the clk but it
 * isn't provided on this system.
 * A valid clk_core pointer when the clk can be found in the provider.
 */
static struct clk_core *clk_core_get(struct clk_core *core, u8 p_index)
{
        const char *name = core->parents[p_index].fw_name;
        int index = core->parents[p_index].index;
        struct clk_hw *hw = ERR_PTR(-ENOENT);
        struct device *dev = core->dev;
        const char *dev_id = dev ? dev_name(dev) : NULL;
        struct device_node *np = core->of_node;
        struct of_phandle_args clkspec;

        if (np && (name || index >= 0) &&
            !of_parse_clkspec(np, index, name, &clkspec)) {
                hw = of_clk_get_hw_from_clkspec(&clkspec);
                of_node_put(clkspec.np);
        } else if (name) {
                /*
                 * If the DT search above couldn't find the provider fallback to
                 * looking up via clkdev based clk_lookups.
                 */
                hw = clk_find_hw(dev_id, name);
        }

        if (IS_ERR(hw))
                return ERR_CAST(hw);

        return hw->core;
}

static void clk_core_fill_parent_index(struct clk_core *core, u8 index)
{
        struct clk_parent_map *entry = &core->parents[index];
        struct clk_core *parent;

        if (entry->hw) {
                parent = entry->hw->core;
                /*
                 * We have a direct reference but it isn't registered yet?
                 * Orphan it and let clk_reparent() update the orphan status
                 * when the parent is registered.
                 */
                if (!parent)
                        parent = ERR_PTR(-EPROBE_DEFER);
        } else {
                parent = clk_core_get(core, index);
                if (PTR_ERR(parent) == -ENOENT && entry->name)
                        parent = clk_core_lookup(entry->name);
        }

        /* Only cache it if it's not an error */
        if (!IS_ERR(parent))
                entry->core = parent;
}

static struct clk_core *clk_core_get_parent_by_index(struct clk_core *core,
                                                         u8 index)
{
        if (!core || index >= core->num_parents || !core->parents)
                return NULL;

        if (!core->parents[index].core)
                clk_core_fill_parent_index(core, index);

        return core->parents[index].core;
}

struct clk_hw *
clk_hw_get_parent_by_index(const struct clk_hw *hw, unsigned int index)
{
        struct clk_core *parent;

        parent = clk_core_get_parent_by_index(hw->core, index);

        return !parent ? NULL : parent->hw;
}
EXPORT_SYMBOL_GPL(clk_hw_get_parent_by_index);

unsigned int __clk_get_enable_count(struct clk *clk)
{
        return !clk ? 0 : clk->core->enable_count;
}

static unsigned long clk_core_get_rate_nolock(struct clk_core *core)
{
        if (!core)
                return 0;

        if (!core->num_parents || core->parent)
                return core->rate;

        /*
         * Clk must have a parent because num_parents > 0 but the parent isn't
         * known yet. Best to return 0 as the rate of this clk until we can
         * properly recalc the rate based on the parent's rate.
         */
        return 0;
}

unsigned long clk_hw_get_rate(const struct clk_hw *hw)
{
        return clk_core_get_rate_nolock(hw->core);
}
EXPORT_SYMBOL_GPL(clk_hw_get_rate);

static unsigned long clk_core_get_accuracy_no_lock(struct clk_core *core)
{
        if (!core)
                return 0;

        return core->accuracy;
}

unsigned long clk_hw_get_flags(const struct clk_hw *hw)
{
        return hw->core->flags;
}
EXPORT_SYMBOL_GPL(clk_hw_get_flags);

bool clk_hw_is_prepared(const struct clk_hw *hw)
{
        return clk_core_is_prepared(hw->core);
}
EXPORT_SYMBOL_GPL(clk_hw_is_prepared);

bool clk_hw_rate_is_protected(const struct clk_hw *hw)
{
        return clk_core_rate_is_protected(hw->core);
}
EXPORT_SYMBOL_GPL(clk_hw_rate_is_protected);

bool clk_hw_is_enabled(const struct clk_hw *hw)
{
        return clk_core_is_enabled(hw->core);
}
EXPORT_SYMBOL_GPL(clk_hw_is_enabled);

bool __clk_is_enabled(struct clk *clk)
{
        if (!clk)
                return false;

        return clk_core_is_enabled(clk->core);
}
EXPORT_SYMBOL_GPL(__clk_is_enabled);

static bool mux_is_better_rate(unsigned long rate, unsigned long now,
                           unsigned long best, unsigned long flags)
{
        if (flags & CLK_MUX_ROUND_CLOSEST)
                return abs(now - rate) < abs(best - rate);

        return now <= rate && now > best;
}

int clk_mux_determine_rate_flags(struct clk_hw *hw,
                                 struct clk_rate_request *req,
                                 unsigned long flags)
{
        struct clk_core *core = hw->core, *parent, *best_parent = NULL;
        int i, num_parents, ret;
        unsigned long best = 0;
        struct clk_rate_request parent_req = *req;

        /* if NO_REPARENT flag set, pass through to current parent */
        if (core->flags & CLK_SET_RATE_NO_REPARENT) {
                parent = core->parent;
                if (core->flags & CLK_SET_RATE_PARENT) {
                        ret = __clk_determine_rate(parent ? parent->hw : NULL,
                                                   &parent_req);
                        if (ret)
                                return ret;

                        best = parent_req.rate;
                } else if (parent) {
                        best = clk_core_get_rate_nolock(parent);
                } else {
                        best = clk_core_get_rate_nolock(core);
                }

                goto out;
        }

        /* find the parent that can provide the fastest rate <= rate */
        num_parents = core->num_parents;
        for (i = 0; i < num_parents; i++) {
                parent = clk_core_get_parent_by_index(core, i);
                if (!parent)
                        continue;

                if (core->flags & CLK_SET_RATE_PARENT) {
                        parent_req = *req;
                        ret = __clk_determine_rate(parent->hw, &parent_req);
                        if (ret)
                                continue;
                } else {
                        parent_req.rate = clk_core_get_rate_nolock(parent);
                }

                if (mux_is_better_rate(req->rate, parent_req.rate,
                                       best, flags)) {
                        best_parent = parent;
                        best = parent_req.rate;
                }
        }

        if (!best_parent)
                return -EINVAL;

out:
        if (best_parent)
                req->best_parent_hw = best_parent->hw;
        req->best_parent_rate = best;
        req->rate = best;

        return 0;
}
EXPORT_SYMBOL_GPL(clk_mux_determine_rate_flags);

struct clk *__clk_lookup(const char *name)
{
        struct clk_core *core = clk_core_lookup(name);

        return !core ? NULL : core->hw->clk;
}

static void clk_core_get_boundaries(struct clk_core *core,
                                    unsigned long *min_rate,
                                    unsigned long *max_rate)
{
        struct clk *clk_user;

        lockdep_assert_held(&prepare_lock);

        *min_rate = core->min_rate;
        *max_rate = core->max_rate;

        hlist_for_each_entry(clk_user, &core->clks, clks_node)
                *min_rate = max(*min_rate, clk_user->min_rate);

        hlist_for_each_entry(clk_user, &core->clks, clks_node)
                *max_rate = min(*max_rate, clk_user->max_rate);
}

void clk_hw_set_rate_range(struct clk_hw *hw, unsigned long min_rate,
                           unsigned long max_rate)
{
        hw->core->min_rate = min_rate;
        hw->core->max_rate = max_rate;
}
EXPORT_SYMBOL_GPL(clk_hw_set_rate_range);

/*
 * __clk_mux_determine_rate - clk_ops::determine_rate implementation for a mux type clk
 * @hw: mux type clk to determine rate on
 * @req: rate request, also used to return preferred parent and frequencies
 *
 * 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.
 *
 * Returns: 0 on success, -EERROR value on error
 */
int __clk_mux_determine_rate(struct clk_hw *hw,
                             struct clk_rate_request *req)
{
        return clk_mux_determine_rate_flags(hw, req, 0);
}
EXPORT_SYMBOL_GPL(__clk_mux_determine_rate);

int __clk_mux_determine_rate_closest(struct clk_hw *hw,
                                     struct clk_rate_request *req)
{
        return clk_mux_determine_rate_flags(hw, req, CLK_MUX_ROUND_CLOSEST);
}
EXPORT_SYMBOL_GPL(__clk_mux_determine_rate_closest);

/***        clk api        ***/

static void clk_core_rate_unprotect(struct clk_core *core)
{
        lockdep_assert_held(&prepare_lock);

        if (!core)
                return;

        if (WARN(core->protect_count == 0,
            "%s already unprotected\n", core->name))
                return;

        if (--core->protect_count > 0)
                return;

        clk_core_rate_unprotect(core->parent);
}

static int clk_core_rate_nuke_protect(struct clk_core *core)
{
        int ret;

        lockdep_assert_held(&prepare_lock);

        if (!core)
                return -EINVAL;

        if (core->protect_count == 0)
                return 0;

        ret = core->protect_count;
        core->protect_count = 1;
        clk_core_rate_unprotect(core);

        return ret;
}

/**
 * clk_rate_exclusive_put - release exclusivity over clock rate control
 * @clk: the clk over which the exclusivity is released
 *
 * clk_rate_exclusive_put() completes a critical section during which a clock
 * consumer cannot tolerate any other consumer making any operation on the
 * clock which could result in a rate change or rate glitch. Exclusive clocks
 * cannot have their rate changed, either directly or indirectly due to changes
 * further up the parent chain of clocks. As a result, clocks up parent chain
 * also get under exclusive control of the calling consumer.
 *
 * If exlusivity is claimed more than once on clock, even by the same consumer,
 * the rate effectively gets locked as exclusivity can't be preempted.
 *
 * Calls to clk_rate_exclusive_put() must be balanced with calls to
 * clk_rate_exclusive_get(). Calls to this function may sleep, and do not return
 * error status.
 */
void clk_rate_exclusive_put(struct clk *clk)
{
        if (!clk)
                return;

        clk_prepare_lock();

        /*
         * if there is something wrong with this consumer protect count, stop
         * here before messing with the provider
         */
        if (WARN_ON(clk->exclusive_count <= 0))
                goto out;

        clk_core_rate_unprotect(clk->core);
        clk->exclusive_count--;
out:
        clk_prepare_unlock();
}
EXPORT_SYMBOL_GPL(clk_rate_exclusive_put);

static void clk_core_rate_protect(struct clk_core *core)
{
        lockdep_assert_held(&prepare_lock);

        if (!core)
                return;

        if (core->protect_count == 0)
                clk_core_rate_protect(core->parent);

        core->protect_count++;
}

static void clk_core_rate_restore_protect(struct clk_core *core, int count)
{
        lockdep_assert_held(&prepare_lock);

        if (!core)
                return;

        if (count == 0)
                return;

        clk_core_rate_protect(core);
        core->protect_count = count;
}

/**
 * clk_rate_exclusive_get - get exclusivity over the clk rate control
 * @clk: the clk over which the exclusity of rate control is requested
 *
 * clk_rate_exclusive_get() begins a critical section during which a clock
 * consumer cannot tolerate any other consumer making any operation on the
 * clock which could result in a rate change or rate glitch. Exclusive clocks
 * cannot have their rate changed, either directly or indirectly due to changes
 * further up the parent chain of clocks. As a result, clocks up parent chain
 * also get under exclusive control of the calling consumer.
 *
 * If exlusivity is claimed more than once on clock, even by the same consumer,
 * the rate effectively gets locked as exclusivity can't be preempted.
 *
 * Calls to clk_rate_exclusive_get() should be balanced with calls to
 * clk_rate_exclusive_put(). Calls to this function may sleep.
 * Returns 0 on success, -EERROR otherwise
 */
int clk_rate_exclusive_get(struct clk *clk)
{
        if (!clk)
                return 0;

        clk_prepare_lock();
        clk_core_rate_protect(clk->core);
        clk->exclusive_count++;
        clk_prepare_unlock();

        return 0;
}
EXPORT_SYMBOL_GPL(clk_rate_exclusive_get);

static void clk_core_unprepare(struct clk_core *core)
{
        lockdep_assert_held(&prepare_lock);

        if (!core)
                return;

        if (WARN(core->prepare_count == 0,
            "%s already unprepared\n", core->name))
                return;

        if (WARN(core->prepare_count == 1 && core->flags & CLK_IS_CRITICAL,
            "Unpreparing critical %s\n", core->name))
                return;

        if (core->flags & CLK_SET_RATE_GATE)
                clk_core_rate_unprotect(core);

        if (--core->prepare_count > 0)
                return;

        WARN(core->enable_count > 0, "Unpreparing enabled %s\n", core->name);

        trace_clk_unprepare(core);

        if (core->ops->unprepare)
                core->ops->unprepare(core->hw);

        clk_pm_runtime_put(core);

        trace_clk_unprepare_complete(core);
        clk_core_unprepare(core->parent);
}

static void clk_core_unprepare_lock(struct clk_core *core)
{
        clk_prepare_lock();
        clk_core_unprepare(core);
        clk_prepare_unlock();
}

/**
 * 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_core_unprepare_lock(clk->core);
}
EXPORT_SYMBOL_GPL(clk_unprepare);

static int clk_core_prepare(struct clk_core *core)
{
        int ret = 0;

        lockdep_assert_held(&prepare_lock);

        if (!core)
                return 0;

        if (core->prepare_count == 0) {
                ret = clk_pm_runtime_get(core);
                if (ret)
                        return ret;

                ret = clk_core_prepare(core->parent);
                if (ret)
                        goto runtime_put;

                trace_clk_prepare(core);

                if (core->ops->prepare)
                        ret = core->ops->prepare(core->hw);

                trace_clk_prepare_complete(core);

                if (ret)
                        goto unprepare;
        }

        core->prepare_count++;

        /*
         * CLK_SET_RATE_GATE is a special case of clock protection
         * Instead of a consumer claiming exclusive rate control, it is
         * actually the provider which prevents any consumer from making any
         * operation which could result in a rate change or rate glitch while
         * the clock is prepared.
         */
        if (core->flags & CLK_SET_RATE_GATE)
                clk_core_rate_protect(core);

        return 0;
unprepare:
        clk_core_unprepare(core->parent);
runtime_put:
        clk_pm_runtime_put(core);
        return ret;
}

static int clk_core_prepare_lock(struct clk_core *core)
{
        int ret;

        clk_prepare_lock();
        ret = clk_core_prepare(core);
        clk_prepare_unlock();

        return ret;
}

/**
 * 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)
{
        if (!clk)
                return 0;

        return clk_core_prepare_lock(clk->core);
}
EXPORT_SYMBOL_GPL(clk_prepare);

static void clk_core_disable(struct clk_core *core)
{
        lockdep_assert_held(&enable_lock);

        if (!core)
                return;

        if (WARN(core->enable_count == 0, "%s already disabled\n", core->name))
                return;

        if (WARN(core->enable_count == 1 && core->flags & CLK_IS_CRITICAL,
            "Disabling critical %s\n", core->name))
                return;

        if (--core->enable_count > 0)
                return;

        trace_clk_disable_rcuidle(core);

        if (core->ops->disable)
                core->ops->disable(core->hw);

        trace_clk_disable_complete_rcuidle(core);

        clk_core_disable(core->parent);
}

static void clk_core_disable_lock(struct clk_core *core)
{
        unsigned long flags;

        flags = clk_enable_lock();
        clk_core_disable(core);
        clk_enable_unlock(flags);
}

/**
 * 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)
{
        if (IS_ERR_OR_NULL(clk))
                return;

        clk_core_disable_lock(clk->core);
}
EXPORT_SYMBOL_GPL(clk_disable);

static int clk_core_enable(struct clk_core *core)
{
        int ret = 0;

        lockdep_assert_held(&enable_lock);

        if (!core)
                return 0;

        if (WARN(core->prepare_count == 0,
            "Enabling unprepared %s\n", core->name))
                return -ESHUTDOWN;

        if (core->enable_count == 0) {
                ret = clk_core_enable(core->parent);

                if (ret)
                        return ret;

                trace_clk_enable_rcuidle(core);

                if (core->ops->enable)
                        ret = core->ops->enable(core->hw);

                trace_clk_enable_complete_rcuidle(core);

                if (ret) {
                        clk_core_disable(core->parent);
                        return ret;
                }
        }

        core->enable_count++;
        return 0;
}

static int clk_core_enable_lock(struct clk_core *core)
{
        unsigned long flags;
        int ret;

        flags = clk_enable_lock();
        ret = clk_core_enable(core);
        clk_enable_unlock(flags);

        return ret;
}

/**
 * clk_gate_restore_context - restore context for poweroff
 * @hw: the clk_hw pointer of clock whose state is to be restored
 *
 * The clock gate restore context function enables or disables
 * the gate clocks based on the enable_count. This is done in cases
 * where the clock context is lost and based on the enable_count
 * the clock either needs to be enabled/disabled. This
 * helps restore the state of gate clocks.
 */
void clk_gate_restore_context(struct clk_hw *hw)
{
        struct clk_core *core = hw->core;

        if (core->enable_count)
                core->ops->enable(hw);
        else
                core->ops->disable(hw);
}
EXPORT_SYMBOL_GPL(clk_gate_restore_context);

static int clk_core_save_context(struct clk_core *core)
{
        struct clk_core *child;
        int ret = 0;

        hlist_for_each_entry(child, &core->children, child_node) {
                ret = clk_core_save_context(child);
                if (ret < 0)
                        return ret;
        }

        if (core->ops && core->ops->save_context)
                ret = core->ops->save_context(core->hw);

        return ret;
}

static void clk_core_restore_context(struct clk_core *core)
{
        struct clk_core *child;

        if (core->ops && core->ops->restore_context)
                core->ops->restore_context(core->hw);

        hlist_for_each_entry(child, &core->children, child_node)
                clk_core_restore_context(child);
}

/**
 * clk_save_context - save clock context for poweroff
 *
 * Saves the context of the clock register for powerstates in which the
 * contents of the registers will be lost. Occurs deep within the suspend
 * code.  Returns 0 on success.
 */
int clk_save_context(void)
{
        struct clk_core *clk;
        int ret;

        hlist_for_each_entry(clk, &clk_root_list, child_node) {
                ret = clk_core_save_context(clk);
                if (ret < 0)
                        return ret;
        }

        hlist_for_each_entry(clk, &clk_orphan_list, child_node) {
                ret = clk_core_save_context(clk);
                if (ret < 0)
                        return ret;
        }

        return 0;
}
EXPORT_SYMBOL_GPL(clk_save_context);

/**
 * clk_restore_context - restore clock context after poweroff
 *
 * Restore the saved clock context upon resume.
 *
 */
void clk_restore_context(void)
{
        struct clk_core *core;

        hlist_for_each_entry(core, &clk_root_list, child_node)
                clk_core_restore_context(core);

        hlist_for_each_entry(core, &clk_orphan_list, child_node)
                clk_core_restore_context(core);
}
EXPORT_SYMBOL_GPL(clk_restore_context);

/**
 * 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)
{
        if (!clk)
                return 0;

        return clk_core_enable_lock(clk->core);
}
EXPORT_SYMBOL_GPL(clk_enable);

/**
 * clk_is_enabled_when_prepared - indicate if preparing a clock also enables it.
 * @clk: clock source
 *
 * Returns true if clk_prepare() implicitly enables the clock, effectively
 * making clk_enable()/clk_disable() no-ops, false otherwise.
 *
 * This is of interest mainly to power management code where actually
 * disabling the clock also requires unpreparing it to have any material
 * effect.
 *
 * Regardless of the value returned here, the caller must always invoke
 * clk_enable() or clk_prepare_enable()  and counterparts for usage counts
 * to be right.
 */
bool clk_is_enabled_when_prepared(struct clk *clk)
{
        return clk && !(clk->core->ops->enable && clk->core->ops->disable);
}
EXPORT_SYMBOL_GPL(clk_is_enabled_when_prepared);

static int clk_core_prepare_enable(struct clk_core *core)
{
        int ret;

        ret = clk_core_prepare_lock(core);
        if (ret)
                return ret;

        ret = clk_core_enable_lock(core);
        if (ret)
                clk_core_unprepare_lock(core);

        return ret;
}

static void clk_core_disable_unprepare(struct clk_core *core)
{
        clk_core_disable_lock(core);
        clk_core_unprepare_lock(core);
}

static void __init clk_unprepare_unused_subtree(struct clk_core *core)
{
        struct clk_core *child;

        lockdep_assert_held(&prepare_lock);

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

        if (core->prepare_count)
                return;

        if (core->flags & CLK_IGNORE_UNUSED)
                return;

        if (clk_pm_runtime_get(core))
                return;

        if (clk_core_is_prepared(core)) {
                trace_clk_unprepare(core);
                if (core->ops->unprepare_unused)
                        core->ops->unprepare_unused(core->hw);
                else if (core->ops->unprepare)
                        core->ops->unprepare(core->hw);
                trace_clk_unprepare_complete(core);
        }

        clk_pm_runtime_put(core);
}

static void __init clk_disable_unused_subtree(struct clk_core *core)
{
        struct clk_core *child;
        unsigned long flags;

        lockdep_assert_held(&prepare_lock);

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

        if (core->flags & CLK_OPS_PARENT_ENABLE)
                clk_core_prepare_enable(core->parent);

        if (clk_pm_runtime_get(core))
                goto unprepare_out;

        flags = clk_enable_lock();

        if (core->enable_count)
                goto unlock_out;

        if (core->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_core_is_enabled(core)) {
                trace_clk_disable(core);
                if (core->ops->disable_unused)
                        core->ops->disable_unused(core->hw);
                else if (core->ops->disable)
                        core->ops->disable(core->hw);
                trace_clk_disable_complete(core);
        }

unlock_out:
        clk_enable_unlock(flags);
        clk_pm_runtime_put(core);
unprepare_out:
        if (core->flags & CLK_OPS_PARENT_ENABLE)
                clk_core_disable_unprepare(core->parent);
}

static bool clk_ignore_unused __initdata;
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 __init clk_disable_unused(void)
{
        struct clk_core *core;

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

        clk_prepare_lock();

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

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

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

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

        clk_prepare_unlock();

        return 0;
}
late_initcall_sync(clk_disable_unused);

static int clk_core_determine_round_nolock(struct clk_core *core,
                                           struct clk_rate_request *req)
{
        long rate;

        lockdep_assert_held(&prepare_lock);

        if (!core)
                return 0;

        /*
         * At this point, core protection will be disabled
         * - if the provider is not protected at all
         * - if the calling consumer is the only one which has exclusivity
         *   over the provider
         */
        if (clk_core_rate_is_protected(core)) {
                req->rate = core->rate;
        } else if (core->ops->determine_rate) {
                return core->ops->determine_rate(core->hw, req);
        } else if (core->ops->round_rate) {
                rate = core->ops->round_rate(core->hw, req->rate,
                                             &req->best_parent_rate);
                if (rate < 0)
                        return rate;

                req->rate = rate;
        } else {
                return -EINVAL;
        }

        return 0;
}

static void clk_core_init_rate_req(struct clk_core * const core,
                                   struct clk_rate_request *req)
{
        struct clk_core *parent;

        if (WARN_ON(!core || !req))
                return;

        parent = core->parent;
        if (parent) {
                req->best_parent_hw = parent->hw;
                req->best_parent_rate = parent->rate;
        } else {
                req->best_parent_hw = NULL;
                req->best_parent_rate = 0;
        }
}

static bool clk_core_can_round(struct clk_core * const core)
{
        return core->ops->determine_rate || core->ops->round_rate;
}

static int clk_core_round_rate_nolock(struct clk_core *core,
                                      struct clk_rate_request *req)
{
        lockdep_assert_held(&prepare_lock);

        if (!core) {
                req->rate = 0;
                return 0;
        }

        clk_core_init_rate_req(core, req);

        if (clk_core_can_round(core))
                return clk_core_determine_round_nolock(core, req);
        else if (core->flags & CLK_SET_RATE_PARENT)
                return clk_core_round_rate_nolock(core->parent, req);

        req->rate = core->rate;
        return 0;
}

/**
 * __clk_determine_rate - get the closest rate actually supported by a clock
 * @hw: determine the rate of this clock
 * @req: target rate request
 *
 * Useful for clk_ops such as .set_rate and .determine_rate.
 */
int __clk_determine_rate(struct clk_hw *hw, struct clk_rate_request *req)
{
        if (!hw) {
                req->rate = 0;
                return 0;
        }

        return clk_core_round_rate_nolock(hw->core, req);
}
EXPORT_SYMBOL_GPL(__clk_determine_rate);

/**
 * clk_hw_round_rate() - round the given rate for a hw clk
 * @hw: the hw 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.
 *
 * Context: prepare_lock must be held.
 *          For clk providers to call from within clk_ops such as .round_rate,
 *          .determine_rate.
 *
 * Return: returns rounded rate of hw clk if clk supports round_rate operation
 *         else returns the parent rate.
 */
unsigned long clk_hw_round_rate(struct clk_hw *hw, unsigned long rate)
{
        int ret;
        struct clk_rate_request req;

        clk_core_get_boundaries(hw->core, &req.min_rate, &req.max_rate);
        req.rate = rate;

        ret = clk_core_round_rate_nolock(hw->core, &req);
        if (ret)
                return 0;

        return req.rate;
}
EXPORT_SYMBOL_GPL(clk_hw_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)
{
        struct clk_rate_request req;
        int ret;

        if (!clk)
                return 0;

        clk_prepare_lock();

        if (clk->exclusive_count)
                clk_core_rate_unprotect(clk->core);

        clk_core_get_boundaries(clk->core, &req.min_rate, &req.max_rate);
        req.rate = rate;

        ret = clk_core_round_rate_nolock(clk->core, &req);

        if (clk->exclusive_count)
                clk_core_rate_protect(clk->core);

        clk_prepare_unlock();

        if (ret)
                return ret;

        return req.rate;
}
EXPORT_SYMBOL_GPL(clk_round_rate);

/**
 * __clk_notify - call clk notifier chain
 * @core: 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_core *core, 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.old_rate = old_rate;
        cnd.new_rate = new_rate;

        list_for_each_entry(cn, &clk_notifier_list, node) {
                if (cn->clk->core == core) {
                        cnd.clk = cn->clk;
                        ret = srcu_notifier_call_chain(&cn->notifier_head, msg,
                                        &cnd);
                        if (ret & NOTIFY_STOP_MASK)
                                return ret;
                }
        }

        return ret;
}

/**
 * __clk_recalc_accuracies
 * @core: 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 its
 * parent.
 */
static void __clk_recalc_accuracies(struct clk_core *core)
{
        unsigned long parent_accuracy = 0;
        struct clk_core *child;

        lockdep_assert_held(&prepare_lock);

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

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

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

static long clk_core_get_accuracy_recalc(struct clk_core *core)
{
        if (core && (core->flags & CLK_GET_ACCURACY_NOCACHE))
                __clk_recalc_accuracies(core);

        return clk_core_get_accuracy_no_lock(core);
}

/**
 * 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)
{
        long accuracy;

        if (!clk)
                return 0;

        clk_prepare_lock();
        accuracy = clk_core_get_accuracy_recalc(clk->core);
        clk_prepare_unlock();

        return accuracy;
}
EXPORT_SYMBOL_GPL(clk_get_accuracy);

static unsigned long clk_recalc(struct clk_core *core,
                                unsigned long parent_rate)
{
        unsigned long rate = parent_rate;

        if (core->ops->recalc_rate && !clk_pm_runtime_get(core)) {
                rate = core->ops->recalc_rate(core->hw, parent_rate);
                clk_pm_runtime_put(core);
        }
        return rate;
}

/**
 * __clk_recalc_rates
 * @core: 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.
 */
static void __clk_recalc_rates(struct clk_core *core, unsigned long msg)
{
        unsigned long old_rate;
        unsigned long parent_rate = 0;
        struct clk_core *child;

        lockdep_assert_held(&prepare_lock);

        old_rate = core->rate;

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

        core->rate = clk_recalc(core, parent_rate);

        /*
         * ignore NOTIFY_STOP and NOTIFY_BAD return values for POST_RATE_CHANGE
         * & ABORT_RATE_CHANGE notifiers
         */
        if (core->notifier_count && msg)
                __clk_notify(core, msg, old_rate, core->rate);

        hlist_for_each_entry(child, &core->children, child_node)
                __clk_recalc_rates(child, msg);
}

static unsigned long clk_core_get_rate_recalc(struct clk_core *core)
{
        if (core && (core->flags & CLK_GET_RATE_NOCACHE))
                __clk_recalc_rates(core, 0);

        return clk_core_get_rate_nolock(core);
}

/**
 * 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;

        if (!clk)
                return 0;

        clk_prepare_lock();
        rate = clk_core_get_rate_recalc(clk->core);
        clk_prepare_unlock();

        return rate;
}
EXPORT_SYMBOL_GPL(clk_get_rate);

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

        if (!parent)
                return -EINVAL;

        for (i = 0; i < core->num_parents; i++) {
                /* Found it first try! */
                if (core->parents[i].core == parent)
                        return i;

                /* Something else is here, so keep looking */
                if (core->parents[i].core)
                        continue;

                /* Maybe core hasn't been cached but the hw is all we know? */
                if (core->parents[i].hw) {
                        if (core->parents[i].hw == parent->hw)
                                break;

                        /* Didn't match, but we're expecting a clk_hw */
                        continue;
                }

                /* Maybe it hasn't been cached (clk_set_parent() path) */
                if (parent == clk_core_get(core, i))
                        break;

                /* Fallback to comparing globally unique names */
                if (core->parents[i].name &&
                    !strcmp(parent->name, core->parents[i].name))
                        break;
        }

        if (i == core->num_parents)
                return -EINVAL;

        core->parents[i].core = parent;
        return i;
}

/**
 * clk_hw_get_parent_index - return the index of the parent clock
 * @hw: clk_hw associated with the clk being consumed
 *
 * Fetches and returns the index of parent clock. Returns -EINVAL if the given
 * clock does not have a current parent.
 */
int clk_hw_get_parent_index(struct clk_hw *hw)
{
        struct clk_hw *parent = clk_hw_get_parent(hw);

        if (WARN_ON(parent == NULL))
                return -EINVAL;

        return clk_fetch_parent_index(hw->core, parent->core);
}
EXPORT_SYMBOL_GPL(clk_hw_get_parent_index);

/*
 * Update the orphan status of @core and all its children.
 */
static void clk_core_update_orphan_status(struct clk_core *core, bool is_orphan)
{
        struct clk_core *child;

        core->orphan = is_orphan;

        hlist_for_each_entry(child, &core->children, child_node)
                clk_core_update_orphan_status(child, is_orphan);
}

static void clk_reparent(struct clk_core *core, struct clk_core *new_parent)
{
        bool was_orphan = core->orphan;

        hlist_del(&core->child_node);

        if (new_parent) {
                bool becomes_orphan = new_parent->orphan;

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

                hlist_add_head(&core->child_node, &new_parent->children);

                if (was_orphan != becomes_orphan)
                        clk_core_update_orphan_status(core, becomes_orphan);
        } else {
                hlist_add_head(&core->child_node, &clk_orphan_list);
                if (!was_orphan)
                        clk_core_update_orphan_status(core, true);
        }

        core->parent = new_parent;
}

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

        /*
         * 1. enable parents for CLK_OPS_PARENT_ENABLE clock
         *
         * 2. 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.
         */

        /* enable old_parent & parent if CLK_OPS_PARENT_ENABLE is set */
        if (core->flags & CLK_OPS_PARENT_ENABLE) {
                clk_core_prepare_enable(old_parent);
                clk_core_prepare_enable(parent);
        }

        /* migrate prepare count if > 0 */
        if (core->prepare_count) {
                clk_core_prepare_enable(parent);
                clk_core_enable_lock(core);
        }

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

        return old_parent;
}

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

        /* re-balance ref counting if CLK_OPS_PARENT_ENABLE is set */
        if (core->flags & CLK_OPS_PARENT_ENABLE) {
                clk_core_disable_unprepare(parent);
                clk_core_disable_unprepare(old_parent);
        }
}

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

        old_parent = __clk_set_parent_before(core, parent);

        trace_clk_set_parent(core, parent);

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

        trace_clk_set_parent_complete(core, parent);

        if (ret) {
                flags = clk_enable_lock();
                clk_reparent(core, old_parent);
                clk_enable_unlock(flags);
                __clk_set_parent_after(core, old_parent, parent);

                return ret;
        }

        __clk_set_parent_after(core, parent, old_parent);

        return 0;
}

/**
 * __clk_speculate_rates
 * @core: 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.
 */
static int __clk_speculate_rates(struct clk_core *core,
                                 unsigned long parent_rate)
{
        struct clk_core *child;
        unsigned long new_rate;
        int ret = NOTIFY_DONE;

        lockdep_assert_held(&prepare_lock);

        new_rate = clk_recalc(core, parent_rate);

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

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

        hlist_for_each_entry(child, &core->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_core *core, unsigned long new_rate,
                             struct clk_core *new_parent, u8 p_index)
{
        struct clk_core *child;

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

        hlist_for_each_entry(child, &core->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_core *clk_calc_new_rates(struct clk_core *core,
                                           unsigned long rate)
{
        struct clk_core *top = core;
        struct clk_core *old_parent, *parent;
        unsigned long best_parent_rate = 0;
        unsigned long new_rate;
        unsigned long min_rate;
        unsigned long max_rate;
        int p_index = 0;
        long ret;

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

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

        clk_core_get_boundaries(core, &min_rate, &max_rate);

        /* find the closest rate and parent clk/rate */
        if (clk_core_can_round(core)) {
                struct clk_rate_request req;

                req.rate = rate;
                req.min_rate = min_rate;
                req.max_rate = max_rate;

                clk_core_init_rate_req(core, &req);

                ret = clk_core_determine_round_nolock(core, &req);
                if (ret < 0)
                        return NULL;

                best_parent_rate = req.best_parent_rate;
                new_rate = req.rate;
                parent = req.best_parent_hw ? req.best_parent_hw->core : NULL;

                if (new_rate < min_rate || new_rate > max_rate)
                        return NULL;
        } else if (!parent || !(core->flags & CLK_SET_RATE_PARENT)) {
                /* pass-through clock without adjustable parent */
                core->new_rate = core->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 &&
            (core->flags & CLK_SET_PARENT_GATE) && core->prepare_count) {
                pr_debug("%s: %s not gated but wants to reparent\n",
                         __func__, core->name);
                return NULL;
        }

        /* try finding the new parent index */
        if (parent && core->num_parents > 1) {
                p_index = clk_fetch_parent_index(core, parent);
                if (p_index < 0) {
                        pr_debug("%s: clk %s can not be parent of clk %s\n",
                                 __func__, parent->name, core->name);
                        return NULL;