drivers/base/power/clock_ops.c - kernel/msm-4.19 - Gitiles

 /*
  * drivers/base/power/clock_ops.c - Generic clock manipulation PM callbacks
  *
  * Copyright (c) 2011 Rafael J. Wysocki <rjw@sisk.pl>, Renesas Electronics Corp.
  *
  * This file is released under the GPLv2.
  */

 #include <linux/kernel.h>
 #include <linux/device.h>
 #include <linux/io.h>
 #include <linux/pm.h>
 #include <linux/pm_clock.h>
 #include <linux/clk.h>
 #include <linux/clkdev.h>
 #include <linux/slab.h>
 #include <linux/err.h>

 #ifdef CONFIG_PM

 enum pce_status {
 	PCE_STATUS_NONE = 0,
 	PCE_STATUS_ACQUIRED,
 	PCE_STATUS_ENABLED,
 	PCE_STATUS_ERROR,
 };

 struct pm_clock_entry {
 	struct list_head node;
 	char *con_id;
 	struct clk *clk;
 	enum pce_status status;
 };

 /**
  * pm_clk_enable - Enable a clock, reporting any errors
  * @dev: The device for the given clock
  * @ce: PM clock entry corresponding to the clock.
  */
 static inline int __pm_clk_enable(struct device *dev, struct pm_clock_entry *ce)
 {
 	int ret;

 	if (ce->status < PCE_STATUS_ERROR) {
 		ret = clk_enable(ce->clk);
 		if (!ret)
 			ce->status = PCE_STATUS_ENABLED;
 		else
 			dev_err(dev, "%s: failed to enable clk %p, error %d\n",
 				__func__, ce->clk, ret);
 	}

 	return ret;
 }

 /**
  * pm_clk_acquire - Acquire a device clock.
  * @dev: Device whose clock is to be acquired.
  * @ce: PM clock entry corresponding to the clock.
  */
 static void pm_clk_acquire(struct device *dev, struct pm_clock_entry *ce)
 {
 	if (!ce->clk)
 		ce->clk = clk_get(dev, ce->con_id);
 	if (IS_ERR(ce->clk)) {
 		ce->status = PCE_STATUS_ERROR;
 	} else {
 		clk_prepare(ce->clk);
 		ce->status = PCE_STATUS_ACQUIRED;
 		dev_dbg(dev, "Clock %s managed by runtime PM.\n", ce->con_id);
 	}
 }

 static int __pm_clk_add(struct device *dev, const char *con_id,
 			struct clk *clk)
 {
 	struct pm_subsys_data *psd = dev_to_psd(dev);
 	struct pm_clock_entry *ce;

 	if (!psd)
 		return -EINVAL;

 	ce = kzalloc(sizeof(*ce), GFP_KERNEL);
 	if (!ce) {
 		dev_err(dev, "Not enough memory for clock entry.\n");
 		return -ENOMEM;
 	}

 	if (con_id) {
 		ce->con_id = kstrdup(con_id, GFP_KERNEL);
 		if (!ce->con_id) {
 			dev_err(dev,
 				"Not enough memory for clock connection ID.\n");
 			kfree(ce);
 			return -ENOMEM;
 		}
 	} else {
 		if (IS_ERR(ce->clk) || !__clk_get(clk)) {
 			kfree(ce);
 			return -ENOENT;
 		}
 		ce->clk = clk;
 	}

 	pm_clk_acquire(dev, ce);

 	spin_lock_irq(&psd->lock);
 	list_add_tail(&ce->node, &psd->clock_list);
 	spin_unlock_irq(&psd->lock);
 	return 0;
 }

 /**
  * pm_clk_add - Start using a device clock for power management.
  * @dev: Device whose clock is going to be used for power management.
  * @con_id: Connection ID of the clock.
  *
  * Add the clock represented by @con_id to the list of clocks used for
  * the power management of @dev.
  */
 int pm_clk_add(struct device *dev, const char *con_id)
 {
 	return __pm_clk_add(dev, con_id, NULL);
 }

 /**
  * pm_clk_add_clk - Start using a device clock for power management.
  * @dev: Device whose clock is going to be used for power management.
  * @clk: Clock pointer
  *
  * Add the clock to the list of clocks used for the power management of @dev.
  * It will increment refcount on clock pointer, use clk_put() on it when done.
  */
 int pm_clk_add_clk(struct device *dev, struct clk *clk)
 {
 	return __pm_clk_add(dev, NULL, clk);
 }

 /**
  * __pm_clk_remove - Destroy PM clock entry.
  * @ce: PM clock entry to destroy.
  */
 static void __pm_clk_remove(struct pm_clock_entry *ce)
 {
 	if (!ce)
 		return;

 	if (ce->status < PCE_STATUS_ERROR) {
 		if (ce->status == PCE_STATUS_ENABLED)
 			clk_disable(ce->clk);

 		if (ce->status >= PCE_STATUS_ACQUIRED) {
 			clk_unprepare(ce->clk);
 			clk_put(ce->clk);
 		}
 	}

 	kfree(ce->con_id);
 	kfree(ce);
 }

 /**
  * pm_clk_remove - Stop using a device clock for power management.
  * @dev: Device whose clock should not be used for PM any more.
  * @con_id: Connection ID of the clock.
  *
  * Remove the clock represented by @con_id from the list of clocks used for
  * the power management of @dev.
  */
 void pm_clk_remove(struct device *dev, const char *con_id)
 {
 	struct pm_subsys_data *psd = dev_to_psd(dev);
 	struct pm_clock_entry *ce;

 	if (!psd)
 		return;

 	spin_lock_irq(&psd->lock);

 	list_for_each_entry(ce, &psd->clock_list, node) {
 		if (!con_id && !ce->con_id)
 			goto remove;
 		else if (!con_id || !ce->con_id)
 			continue;
 		else if (!strcmp(con_id, ce->con_id))
 			goto remove;
 	}

 	spin_unlock_irq(&psd->lock);
 	return;

  remove:
 	list_del(&ce->node);
 	spin_unlock_irq(&psd->lock);

 	__pm_clk_remove(ce);
 }

 /**
  * pm_clk_init - Initialize a device's list of power management clocks.
  * @dev: Device to initialize the list of PM clocks for.
  *
  * Initialize the lock and clock_list members of the device's pm_subsys_data
  * object.
  */
 void pm_clk_init(struct device *dev)
 {
 	struct pm_subsys_data *psd = dev_to_psd(dev);
 	if (psd)
 		INIT_LIST_HEAD(&psd->clock_list);
 }

 /**
  * pm_clk_create - Create and initialize a device's list of PM clocks.
  * @dev: Device to create and initialize the list of PM clocks for.
  *
  * Allocate a struct pm_subsys_data object, initialize its lock and clock_list
  * members and make the @dev's power.subsys_data field point to it.
  */
 int pm_clk_create(struct device *dev)
 {
 	return dev_pm_get_subsys_data(dev);
 }

 /**
  * pm_clk_destroy - Destroy a device's list of power management clocks.
  * @dev: Device to destroy the list of PM clocks for.
  *
  * Clear the @dev's power.subsys_data field, remove the list of clock entries
  * from the struct pm_subsys_data object pointed to by it before and free
  * that object.
  */
 void pm_clk_destroy(struct device *dev)
 {
 	struct pm_subsys_data *psd = dev_to_psd(dev);
 	struct pm_clock_entry *ce, *c;
 	struct list_head list;

 	if (!psd)
 		return;

 	INIT_LIST_HEAD(&list);

 	spin_lock_irq(&psd->lock);

 	list_for_each_entry_safe_reverse(ce, c, &psd->clock_list, node)
 		list_move(&ce->node, &list);

 	spin_unlock_irq(&psd->lock);

 	dev_pm_put_subsys_data(dev);

 	list_for_each_entry_safe_reverse(ce, c, &list, node) {
 		list_del(&ce->node);
 		__pm_clk_remove(ce);
 	}
 }

 /**
  * pm_clk_suspend - Disable clocks in a device's PM clock list.
  * @dev: Device to disable the clocks for.
  */
 int pm_clk_suspend(struct device *dev)
 {
 	struct pm_subsys_data *psd = dev_to_psd(dev);
 	struct pm_clock_entry *ce;
 	unsigned long flags;

 	dev_dbg(dev, "%s()\n", __func__);

 	if (!psd)
 		return 0;

 	spin_lock_irqsave(&psd->lock, flags);

 	list_for_each_entry_reverse(ce, &psd->clock_list, node) {
 		if (ce->status < PCE_STATUS_ERROR) {
 			if (ce->status == PCE_STATUS_ENABLED)
 				clk_disable(ce->clk);
 			ce->status = PCE_STATUS_ACQUIRED;
 		}
 	}

 	spin_unlock_irqrestore(&psd->lock, flags);

 	return 0;
 }

 /**
  * pm_clk_resume - Enable clocks in a device's PM clock list.
  * @dev: Device to enable the clocks for.
  */
 int pm_clk_resume(struct device *dev)
 {
 	struct pm_subsys_data *psd = dev_to_psd(dev);
 	struct pm_clock_entry *ce;
 	unsigned long flags;

 	dev_dbg(dev, "%s()\n", __func__);

 	if (!psd)
 		return 0;

 	spin_lock_irqsave(&psd->lock, flags);

 	list_for_each_entry(ce, &psd->clock_list, node)
 		__pm_clk_enable(dev, ce);

 	spin_unlock_irqrestore(&psd->lock, flags);

 	return 0;
 }

 /**
  * pm_clk_notify - Notify routine for device addition and removal.
  * @nb: Notifier block object this function is a member of.
  * @action: Operation being carried out by the caller.
  * @data: Device the routine is being run for.
  *
  * For this function to work, @nb must be a member of an object of type
  * struct pm_clk_notifier_block containing all of the requisite data.
  * Specifically, the pm_domain member of that object is copied to the device's
  * pm_domain field and its con_ids member is used to populate the device's list
  * of PM clocks, depending on @action.
  *
  * If the device's pm_domain field is already populated with a value different
  * from the one stored in the struct pm_clk_notifier_block object, the function
  * does nothing.
  */
 static int pm_clk_notify(struct notifier_block *nb,
 				 unsigned long action, void *data)
 {
 	struct pm_clk_notifier_block *clknb;
 	struct device *dev = data;
 	char **con_id;
 	int error;

 	dev_dbg(dev, "%s() %ld\n", __func__, action);

 	clknb = container_of(nb, struct pm_clk_notifier_block, nb);

 	switch (action) {
 	case BUS_NOTIFY_ADD_DEVICE:
 		if (dev->pm_domain)
 			break;

 		error = pm_clk_create(dev);
 		if (error)
 			break;

 		dev->pm_domain = clknb->pm_domain;
 		if (clknb->con_ids[0]) {
 			for (con_id = clknb->con_ids; *con_id; con_id++)
 				pm_clk_add(dev, *con_id);
 		} else {
 			pm_clk_add(dev, NULL);
 		}

 		break;
 	case BUS_NOTIFY_DEL_DEVICE:
 		if (dev->pm_domain != clknb->pm_domain)
 			break;

 		dev->pm_domain = NULL;
 		pm_clk_destroy(dev);
 		break;
 	}

 	return 0;
 }

 #else /* !CONFIG_PM */

 /**
  * enable_clock - Enable a device clock.
  * @dev: Device whose clock is to be enabled.
  * @con_id: Connection ID of the clock.
  */
 static void enable_clock(struct device *dev, const char *con_id)
 {
 	struct clk *clk;

 	clk = clk_get(dev, con_id);
 	if (!IS_ERR(clk)) {
 		clk_prepare_enable(clk);
 		clk_put(clk);
 		dev_info(dev, "Runtime PM disabled, clock forced on.\n");
 	}
 }

 /**
  * disable_clock - Disable a device clock.
  * @dev: Device whose clock is to be disabled.
  * @con_id: Connection ID of the clock.
  */
 static void disable_clock(struct device *dev, const char *con_id)
 {
 	struct clk *clk;

 	clk = clk_get(dev, con_id);
 	if (!IS_ERR(clk)) {
 		clk_disable_unprepare(clk);
 		clk_put(clk);
 		dev_info(dev, "Runtime PM disabled, clock forced off.\n");
 	}
 }

 /**
  * pm_clk_notify - Notify routine for device addition and removal.
  * @nb: Notifier block object this function is a member of.
  * @action: Operation being carried out by the caller.
  * @data: Device the routine is being run for.
  *
  * For this function to work, @nb must be a member of an object of type
  * struct pm_clk_notifier_block containing all of the requisite data.
  * Specifically, the con_ids member of that object is used to enable or disable
  * the device's clocks, depending on @action.
  */
 static int pm_clk_notify(struct notifier_block *nb,
 				 unsigned long action, void *data)
 {
 	struct pm_clk_notifier_block *clknb;
 	struct device *dev = data;
 	char **con_id;

 	dev_dbg(dev, "%s() %ld\n", __func__, action);

 	clknb = container_of(nb, struct pm_clk_notifier_block, nb);

 	switch (action) {
 	case BUS_NOTIFY_BIND_DRIVER:
 		if (clknb->con_ids[0]) {
 			for (con_id = clknb->con_ids; *con_id; con_id++)
 				enable_clock(dev, *con_id);
 		} else {
 			enable_clock(dev, NULL);
 		}
 		break;
 	case BUS_NOTIFY_UNBOUND_DRIVER:
 		if (clknb->con_ids[0]) {
 			for (con_id = clknb->con_ids; *con_id; con_id++)
 				disable_clock(dev, *con_id);
 		} else {
 			disable_clock(dev, NULL);
 		}
 		break;
 	}

 	return 0;
 }

 #endif /* !CONFIG_PM */

 /**
  * pm_clk_add_notifier - Add bus type notifier for power management clocks.
  * @bus: Bus type to add the notifier to.
  * @clknb: Notifier to be added to the given bus type.
  *
  * The nb member of @clknb is not expected to be initialized and its
  * notifier_call member will be replaced with pm_clk_notify().  However,
  * the remaining members of @clknb should be populated prior to calling this
  * routine.
  */
 void pm_clk_add_notifier(struct bus_type *bus,
 				 struct pm_clk_notifier_block *clknb)
 {
 	if (!bus || !clknb)
 		return;

 	clknb->nb.notifier_call = pm_clk_notify;
 	bus_register_notifier(bus, &clknb->nb);
 }
	/*
	* drivers/base/power/clock_ops.c - Generic clock manipulation PM callbacks
	*
	* Copyright (c) 2011 Rafael J. Wysocki <rjw@sisk.pl>, Renesas Electronics Corp.
	*
	* This file is released under the GPLv2.
	*/

	#include <linux/kernel.h>
	#include <linux/device.h>
	#include <linux/io.h>
	#include <linux/pm.h>
	#include <linux/pm_clock.h>
	#include <linux/clk.h>
	#include <linux/clkdev.h>
	#include <linux/slab.h>
	#include <linux/err.h>

	#ifdef CONFIG_PM

	enum pce_status {
	PCE_STATUS_NONE = 0,
	PCE_STATUS_ACQUIRED,
	PCE_STATUS_ENABLED,
	PCE_STATUS_ERROR,
	};

	struct pm_clock_entry {
	struct list_head node;
	char *con_id;
	struct clk *clk;
	enum pce_status status;
	};

	/**
	* pm_clk_enable - Enable a clock, reporting any errors
	* @dev: The device for the given clock
	* @ce: PM clock entry corresponding to the clock.
	*/
	static inline int __pm_clk_enable(struct device dev, struct pm_clock_entry ce)
	{
	int ret;

	if (ce->status < PCE_STATUS_ERROR) {
	ret = clk_enable(ce->clk);
	if (!ret)
	ce->status = PCE_STATUS_ENABLED;
	else
	dev_err(dev, "%s: failed to enable clk %p, error %d\n",
	__func__, ce->clk, ret);
	}

	return ret;
	}

	/**
	* pm_clk_acquire - Acquire a device clock.
	* @dev: Device whose clock is to be acquired.
	* @ce: PM clock entry corresponding to the clock.
	*/
	static void pm_clk_acquire(struct device dev, struct pm_clock_entry ce)
	{
	if (!ce->clk)
	ce->clk = clk_get(dev, ce->con_id);
	if (IS_ERR(ce->clk)) {
	ce->status = PCE_STATUS_ERROR;
	} else {
	clk_prepare(ce->clk);
	ce->status = PCE_STATUS_ACQUIRED;
	dev_dbg(dev, "Clock %s managed by runtime PM.\n", ce->con_id);
	}
	}

	static int __pm_clk_add(struct device dev, const char con_id,
	struct clk *clk)
	{
	struct pm_subsys_data *psd = dev_to_psd(dev);
	struct pm_clock_entry *ce;

	if (!psd)
	return -EINVAL;

	ce = kzalloc(sizeof(*ce), GFP_KERNEL);
	if (!ce) {
	dev_err(dev, "Not enough memory for clock entry.\n");
	return -ENOMEM;
	}

	if (con_id) {
	ce->con_id = kstrdup(con_id, GFP_KERNEL);
	if (!ce->con_id) {
	dev_err(dev,
	"Not enough memory for clock connection ID.\n");
	kfree(ce);
	return -ENOMEM;
	}
	} else {
	if (IS_ERR(ce->clk) \|\| !__clk_get(clk)) {
	kfree(ce);
	return -ENOENT;
	}
	ce->clk = clk;
	}

	pm_clk_acquire(dev, ce);

	spin_lock_irq(&psd->lock);
	list_add_tail(&ce->node, &psd->clock_list);
	spin_unlock_irq(&psd->lock);
	return 0;
	}

	/**
	* pm_clk_add - Start using a device clock for power management.
	* @dev: Device whose clock is going to be used for power management.
	* @con_id: Connection ID of the clock.
	*
	* Add the clock represented by @con_id to the list of clocks used for
	* the power management of @dev.
	*/
	int pm_clk_add(struct device dev, const char con_id)
	{
	return __pm_clk_add(dev, con_id, NULL);
	}

	/**
	* pm_clk_add_clk - Start using a device clock for power management.
	* @dev: Device whose clock is going to be used for power management.
	* @clk: Clock pointer
	*
	* Add the clock to the list of clocks used for the power management of @dev.
	* It will increment refcount on clock pointer, use clk_put() on it when done.
	*/
	int pm_clk_add_clk(struct device dev, struct clk clk)
	{
	return __pm_clk_add(dev, NULL, clk);
	}

	/**
	* __pm_clk_remove - Destroy PM clock entry.
	* @ce: PM clock entry to destroy.
	*/
	static void __pm_clk_remove(struct pm_clock_entry *ce)
	{
	if (!ce)
	return;

	if (ce->status < PCE_STATUS_ERROR) {
	if (ce->status == PCE_STATUS_ENABLED)
	clk_disable(ce->clk);

	if (ce->status >= PCE_STATUS_ACQUIRED) {
	clk_unprepare(ce->clk);
	clk_put(ce->clk);
	}
	}

	kfree(ce->con_id);
	kfree(ce);
	}

	/**
	* pm_clk_remove - Stop using a device clock for power management.
	* @dev: Device whose clock should not be used for PM any more.
	* @con_id: Connection ID of the clock.
	*
	* Remove the clock represented by @con_id from the list of clocks used for
	* the power management of @dev.
	*/
	void pm_clk_remove(struct device dev, const char con_id)
	{
	struct pm_subsys_data *psd = dev_to_psd(dev);
	struct pm_clock_entry *ce;

	if (!psd)
	return;

	spin_lock_irq(&psd->lock);

	list_for_each_entry(ce, &psd->clock_list, node) {
	if (!con_id && !ce->con_id)
	goto remove;
	else if (!con_id \|\| !ce->con_id)
	continue;
	else if (!strcmp(con_id, ce->con_id))
	goto remove;
	}

	spin_unlock_irq(&psd->lock);
	return;

	remove:
	list_del(&ce->node);
	spin_unlock_irq(&psd->lock);

	__pm_clk_remove(ce);
	}

	/**
	* pm_clk_init - Initialize a device's list of power management clocks.
	* @dev: Device to initialize the list of PM clocks for.
	*
	* Initialize the lock and clock_list members of the device's pm_subsys_data
	* object.
	*/
	void pm_clk_init(struct device *dev)
	{
	struct pm_subsys_data *psd = dev_to_psd(dev);
	if (psd)
	INIT_LIST_HEAD(&psd->clock_list);
	}

	/**
	* pm_clk_create - Create and initialize a device's list of PM clocks.
	* @dev: Device to create and initialize the list of PM clocks for.
	*
	* Allocate a struct pm_subsys_data object, initialize its lock and clock_list
	* members and make the @dev's power.subsys_data field point to it.
	*/
	int pm_clk_create(struct device *dev)
	{
	return dev_pm_get_subsys_data(dev);
	}

	/**
	* pm_clk_destroy - Destroy a device's list of power management clocks.
	* @dev: Device to destroy the list of PM clocks for.
	*
	* Clear the @dev's power.subsys_data field, remove the list of clock entries
	* from the struct pm_subsys_data object pointed to by it before and free
	* that object.
	*/
	void pm_clk_destroy(struct device *dev)
	{
	struct pm_subsys_data *psd = dev_to_psd(dev);
	struct pm_clock_entry ce, c;
	struct list_head list;

	if (!psd)
	return;

	INIT_LIST_HEAD(&list);

	spin_lock_irq(&psd->lock);

	list_for_each_entry_safe_reverse(ce, c, &psd->clock_list, node)
	list_move(&ce->node, &list);

	spin_unlock_irq(&psd->lock);

	dev_pm_put_subsys_data(dev);

	list_for_each_entry_safe_reverse(ce, c, &list, node) {
	list_del(&ce->node);
	__pm_clk_remove(ce);
	}
	}

	/**
	* pm_clk_suspend - Disable clocks in a device's PM clock list.
	* @dev: Device to disable the clocks for.
	*/
	int pm_clk_suspend(struct device *dev)
	{
	struct pm_subsys_data *psd = dev_to_psd(dev);
	struct pm_clock_entry *ce;
	unsigned long flags;

	dev_dbg(dev, "%s()\n", __func__);

	if (!psd)
	return 0;

	spin_lock_irqsave(&psd->lock, flags);

	list_for_each_entry_reverse(ce, &psd->clock_list, node) {
	if (ce->status < PCE_STATUS_ERROR) {
	if (ce->status == PCE_STATUS_ENABLED)
	clk_disable(ce->clk);
	ce->status = PCE_STATUS_ACQUIRED;
	}
	}

	spin_unlock_irqrestore(&psd->lock, flags);

	return 0;
	}

	/**
	* pm_clk_resume - Enable clocks in a device's PM clock list.
	* @dev: Device to enable the clocks for.
	*/
	int pm_clk_resume(struct device *dev)
	{
	struct pm_subsys_data *psd = dev_to_psd(dev);
	struct pm_clock_entry *ce;
	unsigned long flags;

	dev_dbg(dev, "%s()\n", __func__);

	if (!psd)
	return 0;

	spin_lock_irqsave(&psd->lock, flags);

	list_for_each_entry(ce, &psd->clock_list, node)
	__pm_clk_enable(dev, ce);

	spin_unlock_irqrestore(&psd->lock, flags);

	return 0;
	}

	/**
	* pm_clk_notify - Notify routine for device addition and removal.
	* @nb: Notifier block object this function is a member of.
	* @action: Operation being carried out by the caller.
	* @data: Device the routine is being run for.
	*
	* For this function to work, @nb must be a member of an object of type
	* struct pm_clk_notifier_block containing all of the requisite data.
	* Specifically, the pm_domain member of that object is copied to the device's
	* pm_domain field and its con_ids member is used to populate the device's list
	* of PM clocks, depending on @action.
	*
	* If the device's pm_domain field is already populated with a value different
	* from the one stored in the struct pm_clk_notifier_block object, the function
	* does nothing.
	*/
	static int pm_clk_notify(struct notifier_block *nb,
	unsigned long action, void *data)
	{
	struct pm_clk_notifier_block *clknb;
	struct device *dev = data;
	char **con_id;
	int error;

	dev_dbg(dev, "%s() %ld\n", __func__, action);

	clknb = container_of(nb, struct pm_clk_notifier_block, nb);

	switch (action) {
	case BUS_NOTIFY_ADD_DEVICE:
	if (dev->pm_domain)
	break;

	error = pm_clk_create(dev);
	if (error)
	break;

	dev->pm_domain = clknb->pm_domain;
	if (clknb->con_ids[0]) {
	for (con_id = clknb->con_ids; *con_id; con_id++)
	pm_clk_add(dev, *con_id);
	} else {
	pm_clk_add(dev, NULL);
	}

	break;
	case BUS_NOTIFY_DEL_DEVICE:
	if (dev->pm_domain != clknb->pm_domain)
	break;

	dev->pm_domain = NULL;
	pm_clk_destroy(dev);
	break;
	}

	return 0;
	}

	#else /* !CONFIG_PM */

	/**
	* enable_clock - Enable a device clock.
	* @dev: Device whose clock is to be enabled.
	* @con_id: Connection ID of the clock.
	*/
	static void enable_clock(struct device dev, const char con_id)
	{
	struct clk *clk;

	clk = clk_get(dev, con_id);
	if (!IS_ERR(clk)) {
	clk_prepare_enable(clk);
	clk_put(clk);
	dev_info(dev, "Runtime PM disabled, clock forced on.\n");
	}
	}

	/**
	* disable_clock - Disable a device clock.
	* @dev: Device whose clock is to be disabled.
	* @con_id: Connection ID of the clock.
	*/
	static void disable_clock(struct device dev, const char con_id)
	{
	struct clk *clk;

	clk = clk_get(dev, con_id);
	if (!IS_ERR(clk)) {
	clk_disable_unprepare(clk);
	clk_put(clk);
	dev_info(dev, "Runtime PM disabled, clock forced off.\n");
	}
	}

	/**
	* pm_clk_notify - Notify routine for device addition and removal.
	* @nb: Notifier block object this function is a member of.
	* @action: Operation being carried out by the caller.
	* @data: Device the routine is being run for.
	*
	* For this function to work, @nb must be a member of an object of type
	* struct pm_clk_notifier_block containing all of the requisite data.
	* Specifically, the con_ids member of that object is used to enable or disable
	* the device's clocks, depending on @action.
	*/
	static int pm_clk_notify(struct notifier_block *nb,
	unsigned long action, void *data)
	{
	struct pm_clk_notifier_block *clknb;
	struct device *dev = data;
	char **con_id;

	dev_dbg(dev, "%s() %ld\n", __func__, action);

	clknb = container_of(nb, struct pm_clk_notifier_block, nb);

	switch (action) {
	case BUS_NOTIFY_BIND_DRIVER:
	if (clknb->con_ids[0]) {
	for (con_id = clknb->con_ids; *con_id; con_id++)
	enable_clock(dev, *con_id);
	} else {
	enable_clock(dev, NULL);
	}
	break;
	case BUS_NOTIFY_UNBOUND_DRIVER:
	if (clknb->con_ids[0]) {
	for (con_id = clknb->con_ids; *con_id; con_id++)
	disable_clock(dev, *con_id);
	} else {
	disable_clock(dev, NULL);
	}
	break;
	}

	return 0;
	}

	#endif /* !CONFIG_PM */

	/**
	* pm_clk_add_notifier - Add bus type notifier for power management clocks.
	* @bus: Bus type to add the notifier to.
	* @clknb: Notifier to be added to the given bus type.
	*
	* The nb member of @clknb is not expected to be initialized and its
	* notifier_call member will be replaced with pm_clk_notify(). However,
	* the remaining members of @clknb should be populated prior to calling this
	* routine.
	*/
	void pm_clk_add_notifier(struct bus_type *bus,
	struct pm_clk_notifier_block *clknb)
	{
	if (!bus \|\| !clknb)
	return;

	clknb->nb.notifier_call = pm_clk_notify;
	bus_register_notifier(bus, &clknb->nb);
	}