[linux-2.6-block.git] / drivers / base / power / qos.c

/*
 * Devices PM QoS constraints management
 *
 * Copyright (C) 2011 Texas Instruments, Inc.
 *
 * 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.
 *
 *
 * This module exposes the interface to kernel space for specifying
 * per-device PM QoS dependencies. It provides infrastructure for registration
 * of:
 *
 * Dependents on a QoS value : register requests
 * Watchers of QoS value : get notified when target QoS value changes
 *
 * This QoS design is best effort based. Dependents register their QoS needs.
 * Watchers register to keep track of the current QoS needs of the system.
 * Watchers can register different types of notification callbacks:
 *  . a per-device notification callback using the dev_pm_qos_*_notifier API.
 *    The notification chain data is stored in the per-device constraint
 *    data struct.
 *  . a system-wide notification callback using the dev_pm_qos_*_global_notifier
 *    API. The notification chain data is stored in a static variable.
 *
 * Note about the per-device constraint data struct allocation:
 * . The per-device constraints data struct ptr is tored into the device
 *    dev_pm_info.
 * . To minimize the data usage by the per-device constraints, the data struct
 *   is only allocated at the first call to dev_pm_qos_add_request.
 * . The data is later free'd when the device is removed from the system.
 *  . A global mutex protects the constraints users from the data being
 *     allocated and free'd.
 */

#include <linux/pm_qos.h>
#include <linux/spinlock.h>
#include <linux/slab.h>
#include <linux/device.h>
#include <linux/mutex.h>
#include <linux/export.h>


static DEFINE_MUTEX(dev_pm_qos_mtx);

static BLOCKING_NOTIFIER_HEAD(dev_pm_notifiers);

/**
 * dev_pm_qos_read_value - Get PM QoS constraint for a given device.
 * @dev: Device to get the PM QoS constraint value for.
 */
s32 dev_pm_qos_read_value(struct device *dev)
{
	struct pm_qos_constraints *c;
	unsigned long flags;
	s32 ret = 0;

	spin_lock_irqsave(&dev->power.lock, flags);

	c = dev->power.constraints;
	if (c)
		ret = pm_qos_read_value(c);

	spin_unlock_irqrestore(&dev->power.lock, flags);

	return ret;
}

/*
 * apply_constraint
 * @req: constraint request to apply
 * @action: action to perform add/update/remove, of type enum pm_qos_req_action
 * @value: defines the qos request
 *
 * Internal function to update the constraints list using the PM QoS core
 * code and if needed call the per-device and the global notification
 * callbacks
 */
static int apply_constraint(struct dev_pm_qos_request *req,
			    enum pm_qos_req_action action, int value)
{
	int ret, curr_value;

	ret = pm_qos_update_target(req->dev->power.constraints,
				   &req->node, action, value);

	if (ret) {
		/* Call the global callbacks if needed */
		curr_value = pm_qos_read_value(req->dev->power.constraints);
		blocking_notifier_call_chain(&dev_pm_notifiers,
					     (unsigned long)curr_value,
					     req);
	}

	return ret;
}

/*
 * dev_pm_qos_constraints_allocate
 * @dev: device to allocate data for
 *
 * Called at the first call to add_request, for constraint data allocation
 * Must be called with the dev_pm_qos_mtx mutex held
 */
static int dev_pm_qos_constraints_allocate(struct device *dev)
{
	struct pm_qos_constraints *c;
	struct blocking_notifier_head *n;

	c = kzalloc(sizeof(*c), GFP_KERNEL);
	if (!c)
		return -ENOMEM;

	n = kzalloc(sizeof(*n), GFP_KERNEL);
	if (!n) {
		kfree(c);
		return -ENOMEM;
	}
	BLOCKING_INIT_NOTIFIER_HEAD(n);

	plist_head_init(&c->list);
	c->target_value = PM_QOS_DEV_LAT_DEFAULT_VALUE;
	c->default_value = PM_QOS_DEV_LAT_DEFAULT_VALUE;
	c->type = PM_QOS_MIN;
	c->notifiers = n;

	spin_lock_irq(&dev->power.lock);
	dev->power.constraints = c;
	spin_unlock_irq(&dev->power.lock);

	return 0;
}

/**
 * dev_pm_qos_constraints_init - Initalize device's PM QoS constraints pointer.
 * @dev: target device
 *
 * Called from the device PM subsystem during device insertion under
 * device_pm_lock().
 */
void dev_pm_qos_constraints_init(struct device *dev)
{
	mutex_lock(&dev_pm_qos_mtx);
	dev->power.constraints = NULL;
	dev->power.power_state = PMSG_ON;
	mutex_unlock(&dev_pm_qos_mtx);
}

/**
 * dev_pm_qos_constraints_destroy
 * @dev: target device
 *
 * Called from the device PM subsystem on device removal under device_pm_lock().
 */
void dev_pm_qos_constraints_destroy(struct device *dev)
{
	struct dev_pm_qos_request *req, *tmp;
	struct pm_qos_constraints *c;

	mutex_lock(&dev_pm_qos_mtx);

	dev->power.power_state = PMSG_INVALID;
	c = dev->power.constraints;
	if (!c)
		goto out;

	/* Flush the constraints list for the device */
	plist_for_each_entry_safe(req, tmp, &c->list, node) {
		/*
		 * Update constraints list and call the notification
		 * callbacks if needed
		 */
		apply_constraint(req, PM_QOS_REMOVE_REQ, PM_QOS_DEFAULT_VALUE);
		memset(req, 0, sizeof(*req));
	}

	spin_lock_irq(&dev->power.lock);
	dev->power.constraints = NULL;
	spin_unlock_irq(&dev->power.lock);

	kfree(c->notifiers);
	kfree(c);

 out:
	mutex_unlock(&dev_pm_qos_mtx);
}

/**
 * dev_pm_qos_add_request - inserts new qos request into the list
 * @dev: target device for the constraint
 * @req: pointer to a preallocated handle
 * @value: defines the qos request
 *
 * This function inserts a new entry in the device constraints list of
 * requested qos performance characteristics. It recomputes the aggregate
 * QoS expectations of parameters and initializes the dev_pm_qos_request
 * handle.  Caller needs to save this handle for later use in updates and
 * removal.
 *
 * Returns 1 if the aggregated constraint value has changed,
 * 0 if the aggregated constraint value has not changed,
 * -EINVAL in case of wrong parameters, -ENOMEM if there's not enough memory
 * to allocate for data structures, -ENODEV if the device has just been removed
 * from the system.
 */
int dev_pm_qos_add_request(struct device *dev, struct dev_pm_qos_request *req,
			   s32 value)
{
	int ret = 0;

	if (!dev || !req) /*guard against callers passing in null */
		return -EINVAL;

	if (WARN(dev_pm_qos_request_active(req),
		 "%s() called for already added request\n", __func__))
		return -EINVAL;

	req->dev = dev;

	mutex_lock(&dev_pm_qos_mtx);

	if (!dev->power.constraints) {
		if (dev->power.power_state.event == PM_EVENT_INVALID) {
			/* The device has been removed from the system. */
			req->dev = NULL;
			ret = -ENODEV;
			goto out;
		} else {
			/*
			 * Allocate the constraints data on the first call to
			 * add_request, i.e. only if the data is not already
			 * allocated and if the device has not been removed.
			 */
			ret = dev_pm_qos_constraints_allocate(dev);
		}
	}

	if (!ret)
		ret = apply_constraint(req, PM_QOS_ADD_REQ, value);

 out:
	mutex_unlock(&dev_pm_qos_mtx);

	return ret;
}
EXPORT_SYMBOL_GPL(dev_pm_qos_add_request);

/**
 * dev_pm_qos_update_request - modifies an existing qos request
 * @req : handle to list element holding a dev_pm_qos request to use
 * @new_value: defines the qos request
 *
 * Updates an existing dev PM qos request along with updating the
 * target value.
 *
 * Attempts are made to make this code callable on hot code paths.
 *
 * Returns 1 if the aggregated constraint value has changed,
 * 0 if the aggregated constraint value has not changed,
 * -EINVAL in case of wrong parameters, -ENODEV if the device has been
 * removed from the system
 */
int dev_pm_qos_update_request(struct dev_pm_qos_request *req,
			      s32 new_value)
{
	int ret = 0;

	if (!req) /*guard against callers passing in null */
		return -EINVAL;

	if (WARN(!dev_pm_qos_request_active(req),
		 "%s() called for unknown object\n", __func__))
		return -EINVAL;

	mutex_lock(&dev_pm_qos_mtx);

	if (req->dev->power.constraints) {
		if (new_value != req->node.prio)
			ret = apply_constraint(req, PM_QOS_UPDATE_REQ,
					       new_value);
	} else {
		/* Return if the device has been removed */
		ret = -ENODEV;
	}

	mutex_unlock(&dev_pm_qos_mtx);
	return ret;
}
EXPORT_SYMBOL_GPL(dev_pm_qos_update_request);

/**
 * dev_pm_qos_remove_request - modifies an existing qos request
 * @req: handle to request list element
 *
 * Will remove pm qos request from the list of constraints and
 * recompute the current target value. Call this on slow code paths.
 *
 * Returns 1 if the aggregated constraint value has changed,
 * 0 if the aggregated constraint value has not changed,
 * -EINVAL in case of wrong parameters, -ENODEV if the device has been
 * removed from the system
 */
int dev_pm_qos_remove_request(struct dev_pm_qos_request *req)
{
	int ret = 0;

	if (!req) /*guard against callers passing in null */
		return -EINVAL;

	if (WARN(!dev_pm_qos_request_active(req),
		 "%s() called for unknown object\n", __func__))
		return -EINVAL;

	mutex_lock(&dev_pm_qos_mtx);

	if (req->dev->power.constraints) {
		ret = apply_constraint(req, PM_QOS_REMOVE_REQ,
				       PM_QOS_DEFAULT_VALUE);
		memset(req, 0, sizeof(*req));
	} else {
		/* Return if the device has been removed */
		ret = -ENODEV;
	}

	mutex_unlock(&dev_pm_qos_mtx);
	return ret;
}
EXPORT_SYMBOL_GPL(dev_pm_qos_remove_request);

/**
 * dev_pm_qos_add_notifier - sets notification entry for changes to target value
 * of per-device PM QoS constraints
 *
 * @dev: target device for the constraint
 * @notifier: notifier block managed by caller.
 *
 * Will register the notifier into a notification chain that gets called
 * upon changes to the target value for the device.
 */
int dev_pm_qos_add_notifier(struct device *dev, struct notifier_block *notifier)
{
	int retval = 0;

	mutex_lock(&dev_pm_qos_mtx);

	/* Silently return if the constraints object is not present. */
	if (dev->power.constraints)
		retval = blocking_notifier_chain_register(
				dev->power.constraints->notifiers,
				notifier);

	mutex_unlock(&dev_pm_qos_mtx);
	return retval;
}
EXPORT_SYMBOL_GPL(dev_pm_qos_add_notifier);

/**
 * dev_pm_qos_remove_notifier - deletes notification for changes to target value
 * of per-device PM QoS constraints
 *
 * @dev: target device for the constraint
 * @notifier: notifier block to be removed.
 *
 * Will remove the notifier from the notification chain that gets called
 * upon changes to the target value.
 */
int dev_pm_qos_remove_notifier(struct device *dev,
			       struct notifier_block *notifier)
{
	int retval = 0;

	mutex_lock(&dev_pm_qos_mtx);

	/* Silently return if the constraints object is not present. */
	if (dev->power.constraints)
		retval = blocking_notifier_chain_unregister(
				dev->power.constraints->notifiers,
				notifier);

	mutex_unlock(&dev_pm_qos_mtx);
	return retval;
}
EXPORT_SYMBOL_GPL(dev_pm_qos_remove_notifier);

/**
 * dev_pm_qos_add_global_notifier - sets notification entry for changes to
 * target value of the PM QoS constraints for any device
 *
 * @notifier: notifier block managed by caller.
 *
 * Will register the notifier into a notification chain that gets called
 * upon changes to the target value for any device.
 */
int dev_pm_qos_add_global_notifier(struct notifier_block *notifier)
{
	return blocking_notifier_chain_register(&dev_pm_notifiers, notifier);
}
EXPORT_SYMBOL_GPL(dev_pm_qos_add_global_notifier);

/**
 * dev_pm_qos_remove_global_notifier - deletes notification for changes to
 * target value of PM QoS constraints for any device
 *
 * @notifier: notifier block to be removed.
 *
 * Will remove the notifier from the notification chain that gets called
 * upon changes to the target value for any device.
 */
int dev_pm_qos_remove_global_notifier(struct notifier_block *notifier)
{
	return blocking_notifier_chain_unregister(&dev_pm_notifiers, notifier);
}
EXPORT_SYMBOL_GPL(dev_pm_qos_remove_global_notifier);
Commit	Line	Data
91ff4cb8 JP	1	/*
	2	* Devices PM QoS constraints management
	3	*
	4	* Copyright (C) 2011 Texas Instruments, Inc.
	5	*
	6	* This program is free software; you can redistribute it and/or modify
	7	* it under the terms of the GNU General Public License version 2 as
	8	* published by the Free Software Foundation.
	9	*
	10	*
	11	* This module exposes the interface to kernel space for specifying
	12	* per-device PM QoS dependencies. It provides infrastructure for registration
	13	* of:
	14	*
	15	* Dependents on a QoS value : register requests
	16	* Watchers of QoS value : get notified when target QoS value changes
	17	*
	18	* This QoS design is best effort based. Dependents register their QoS needs.
	19	* Watchers register to keep track of the current QoS needs of the system.
b66213cd JP	20	* Watchers can register different types of notification callbacks:
	21	* . a per-device notification callback using the dev_pm_qos_*_notifier API.
	22	* The notification chain data is stored in the per-device constraint
	23	* data struct.
	24	* . a system-wide notification callback using the dev_pm_qos_*_global_notifier
	25	* API. The notification chain data is stored in a static variable.
91ff4cb8 JP	26	*
	27	* Note about the per-device constraint data struct allocation:
	28	* . The per-device constraints data struct ptr is tored into the device
	29	* dev_pm_info.
	30	* . To minimize the data usage by the per-device constraints, the data struct
	31	* is only allocated at the first call to dev_pm_qos_add_request.
	32	* . The data is later free'd when the device is removed from the system.
91ff4cb8 JP	33	* . A global mutex protects the constraints users from the data being
	34	* allocated and free'd.
	35	*/
	36
	37	#include <linux/pm_qos.h>
	38	#include <linux/spinlock.h>
	39	#include <linux/slab.h>
	40	#include <linux/device.h>
	41	#include <linux/mutex.h>
1b6bc32f	42	#include <linux/export.h>
91ff4cb8 JP	43
	44
	45	static DEFINE_MUTEX(dev_pm_qos_mtx);
1a9a9152	46
b66213cd JP	47	static BLOCKING_NOTIFIER_HEAD(dev_pm_notifiers);
b66213cd JP	48
1a9a9152 RW	49	/**
	50	* dev_pm_qos_read_value - Get PM QoS constraint for a given device.
	51	* @dev: Device to get the PM QoS constraint value for.
	52	*/
	53	s32 dev_pm_qos_read_value(struct device *dev)
	54	{
	55	struct pm_qos_constraints *c;
	56	unsigned long flags;
	57	s32 ret = 0;
	58
	59	spin_lock_irqsave(&dev->power.lock, flags);
	60
	61	c = dev->power.constraints;
	62	if (c)
	63	ret = pm_qos_read_value(c);
	64
	65	spin_unlock_irqrestore(&dev->power.lock, flags);
	66
	67	return ret;
	68	}
	69
b66213cd JP	70	/*
	71	* apply_constraint
	72	* @req: constraint request to apply
	73	* @action: action to perform add/update/remove, of type enum pm_qos_req_action
	74	* @value: defines the qos request
	75	*
	76	* Internal function to update the constraints list using the PM QoS core
	77	* code and if needed call the per-device and the global notification
	78	* callbacks
	79	*/
	80	static int apply_constraint(struct dev_pm_qos_request *req,
	81	enum pm_qos_req_action action, int value)
	82	{
	83	int ret, curr_value;
	84
	85	ret = pm_qos_update_target(req->dev->power.constraints,
	86	&req->node, action, value);
	87
	88	if (ret) {
	89	/* Call the global callbacks if needed */
	90	curr_value = pm_qos_read_value(req->dev->power.constraints);
	91	blocking_notifier_call_chain(&dev_pm_notifiers,
	92	(unsigned long)curr_value,
	93	req);
	94	}
	95
	96	return ret;
	97	}
91ff4cb8 JP	98
	99	/*
	100	* dev_pm_qos_constraints_allocate
	101	* @dev: device to allocate data for
	102	*
	103	* Called at the first call to add_request, for constraint data allocation
	104	* Must be called with the dev_pm_qos_mtx mutex held
	105	*/
	106	static int dev_pm_qos_constraints_allocate(struct device *dev)
	107	{
	108	struct pm_qos_constraints *c;
	109	struct blocking_notifier_head *n;
	110
	111	c = kzalloc(sizeof(*c), GFP_KERNEL);
	112	if (!c)
	113	return -ENOMEM;
	114
	115	n = kzalloc(sizeof(*n), GFP_KERNEL);
	116	if (!n) {
	117	kfree(c);
	118	return -ENOMEM;
	119	}
	120	BLOCKING_INIT_NOTIFIER_HEAD(n);
	121
1a9a9152 RW	122	plist_head_init(&c->list);
	123	c->target_value = PM_QOS_DEV_LAT_DEFAULT_VALUE;
	124	c->default_value = PM_QOS_DEV_LAT_DEFAULT_VALUE;
	125	c->type = PM_QOS_MIN;
	126	c->notifiers = n;
	127
	128	spin_lock_irq(&dev->power.lock);
91ff4cb8	129	dev->power.constraints = c;
1a9a9152	130	spin_unlock_irq(&dev->power.lock);
91ff4cb8 JP	131
	132	return 0;
	133	}
	134
	135	/**
1a9a9152	136	* dev_pm_qos_constraints_init - Initalize device's PM QoS constraints pointer.
91ff4cb8 JP	137	* @dev: target device
91ff4cb8 JP	138	*
1a9a9152 RW	139	* Called from the device PM subsystem during device insertion under
1a9a9152 RW	140	* device_pm_lock().
91ff4cb8 JP	141	*/
	142	void dev_pm_qos_constraints_init(struct device *dev)
	143	{
	144	mutex_lock(&dev_pm_qos_mtx);
1a9a9152 RW	145	dev->power.constraints = NULL;
1a9a9152 RW	146	dev->power.power_state = PMSG_ON;
91ff4cb8 JP	147	mutex_unlock(&dev_pm_qos_mtx);
	148	}
	149
	150	/**
	151	* dev_pm_qos_constraints_destroy
	152	* @dev: target device
	153	*
1a9a9152	154	* Called from the device PM subsystem on device removal under device_pm_lock().
91ff4cb8 JP	155	*/
	156	void dev_pm_qos_constraints_destroy(struct device *dev)
	157	{
	158	struct dev_pm_qos_request req, tmp;
1a9a9152	159	struct pm_qos_constraints *c;
91ff4cb8 JP	160
	161	mutex_lock(&dev_pm_qos_mtx);
	162
1a9a9152 RW	163	dev->power.power_state = PMSG_INVALID;
	164	c = dev->power.constraints;
	165	if (!c)
	166	goto out;
91ff4cb8	167
1a9a9152 RW	168	/* Flush the constraints list for the device */
	169	plist_for_each_entry_safe(req, tmp, &c->list, node) {
	170	/*
	171	* Update constraints list and call the notification
	172	* callbacks if needed
	173	*/
	174	apply_constraint(req, PM_QOS_REMOVE_REQ, PM_QOS_DEFAULT_VALUE);
	175	memset(req, 0, sizeof(*req));
91ff4cb8	176	}
91ff4cb8	177
1a9a9152 RW	178	spin_lock_irq(&dev->power.lock);
	179	dev->power.constraints = NULL;
	180	spin_unlock_irq(&dev->power.lock);
	181
	182	kfree(c->notifiers);
	183	kfree(c);
	184
	185	out:
91ff4cb8 JP	186	mutex_unlock(&dev_pm_qos_mtx);
	187	}
	188
	189	/**
	190	* dev_pm_qos_add_request - inserts new qos request into the list
	191	* @dev: target device for the constraint
	192	* @req: pointer to a preallocated handle
	193	* @value: defines the qos request
	194	*
	195	* This function inserts a new entry in the device constraints list of
	196	* requested qos performance characteristics. It recomputes the aggregate
	197	* QoS expectations of parameters and initializes the dev_pm_qos_request
	198	* handle. Caller needs to save this handle for later use in updates and
	199	* removal.
	200	*
	201	* Returns 1 if the aggregated constraint value has changed,
	202	* 0 if the aggregated constraint value has not changed,
1a9a9152 RW	203	* -EINVAL in case of wrong parameters, -ENOMEM if there's not enough memory
	204	* to allocate for data structures, -ENODEV if the device has just been removed
	205	* from the system.
91ff4cb8 JP	206	*/
91ff4cb8 JP	207	int dev_pm_qos_add_request(struct device dev, struct dev_pm_qos_request req,
b66213cd	208	s32 value)
91ff4cb8 JP	209	{
	210	int ret = 0;
	211
	212	if (!dev \|\| !req) /guard against callers passing in null /
	213	return -EINVAL;
	214
af4c720e GL	215	if (WARN(dev_pm_qos_request_active(req),
af4c720e GL	216	"%s() called for already added request\n", __func__))
91ff4cb8	217	return -EINVAL;
91ff4cb8	218
91ff4cb8 JP	219	req->dev = dev;
91ff4cb8 JP	220
1a9a9152	221	mutex_lock(&dev_pm_qos_mtx);
91ff4cb8	222
1a9a9152 RW	223	if (!dev->power.constraints) {
	224	if (dev->power.power_state.event == PM_EVENT_INVALID) {
	225	/* The device has been removed from the system. */
	226	req->dev = NULL;
	227	ret = -ENODEV;
	228	goto out;
	229	} else {
	230	/*
	231	* Allocate the constraints data on the first call to
	232	* add_request, i.e. only if the data is not already
	233	* allocated and if the device has not been removed.
	234	*/
	235	ret = dev_pm_qos_constraints_allocate(dev);
	236	}
	237	}
91ff4cb8 JP	238
91ff4cb8 JP	239	if (!ret)
b66213cd	240	ret = apply_constraint(req, PM_QOS_ADD_REQ, value);
91ff4cb8	241
1a9a9152	242	out:
91ff4cb8	243	mutex_unlock(&dev_pm_qos_mtx);
1a9a9152	244
91ff4cb8 JP	245	return ret;
	246	}
	247	EXPORT_SYMBOL_GPL(dev_pm_qos_add_request);
	248
	249	/**
	250	* dev_pm_qos_update_request - modifies an existing qos request
	251	* @req : handle to list element holding a dev_pm_qos request to use
	252	* @new_value: defines the qos request
	253	*
	254	* Updates an existing dev PM qos request along with updating the
	255	* target value.
	256	*
	257	* Attempts are made to make this code callable on hot code paths.
	258	*
	259	* Returns 1 if the aggregated constraint value has changed,
	260	* 0 if the aggregated constraint value has not changed,
	261	* -EINVAL in case of wrong parameters, -ENODEV if the device has been
	262	* removed from the system
	263	*/
	264	int dev_pm_qos_update_request(struct dev_pm_qos_request *req,
	265	s32 new_value)
	266	{
	267	int ret = 0;
	268
	269	if (!req) /guard against callers passing in null /
	270	return -EINVAL;
	271
af4c720e GL	272	if (WARN(!dev_pm_qos_request_active(req),
af4c720e GL	273	"%s() called for unknown object\n", __func__))
91ff4cb8	274	return -EINVAL;
91ff4cb8 JP	275
	276	mutex_lock(&dev_pm_qos_mtx);
	277
1a9a9152	278	if (req->dev->power.constraints) {
91ff4cb8	279	if (new_value != req->node.prio)
b66213cd JP	280	ret = apply_constraint(req, PM_QOS_UPDATE_REQ,
b66213cd JP	281	new_value);
91ff4cb8 JP	282	} else {
	283	/* Return if the device has been removed */
	284	ret = -ENODEV;
	285	}
	286
	287	mutex_unlock(&dev_pm_qos_mtx);
	288	return ret;
	289	}
	290	EXPORT_SYMBOL_GPL(dev_pm_qos_update_request);
	291
	292	/**
	293	* dev_pm_qos_remove_request - modifies an existing qos request
	294	* @req: handle to request list element
	295	*
	296	* Will remove pm qos request from the list of constraints and
	297	* recompute the current target value. Call this on slow code paths.
	298	*
	299	* Returns 1 if the aggregated constraint value has changed,
	300	* 0 if the aggregated constraint value has not changed,
	301	* -EINVAL in case of wrong parameters, -ENODEV if the device has been
	302	* removed from the system
	303	*/
	304	int dev_pm_qos_remove_request(struct dev_pm_qos_request *req)
	305	{
	306	int ret = 0;
	307
	308	if (!req) /guard against callers passing in null /
	309	return -EINVAL;
	310
af4c720e GL	311	if (WARN(!dev_pm_qos_request_active(req),
af4c720e GL	312	"%s() called for unknown object\n", __func__))
91ff4cb8	313	return -EINVAL;
91ff4cb8 JP	314
	315	mutex_lock(&dev_pm_qos_mtx);
	316
1a9a9152	317	if (req->dev->power.constraints) {
b66213cd JP	318	ret = apply_constraint(req, PM_QOS_REMOVE_REQ,
b66213cd JP	319	PM_QOS_DEFAULT_VALUE);
91ff4cb8 JP	320	memset(req, 0, sizeof(*req));
	321	} else {
	322	/* Return if the device has been removed */
	323	ret = -ENODEV;
	324	}
	325
	326	mutex_unlock(&dev_pm_qos_mtx);
	327	return ret;
	328	}
	329	EXPORT_SYMBOL_GPL(dev_pm_qos_remove_request);
	330
	331	/**
	332	* dev_pm_qos_add_notifier - sets notification entry for changes to target value
	333	* of per-device PM QoS constraints
	334	*
	335	* @dev: target device for the constraint
	336	* @notifier: notifier block managed by caller.
	337	*
	338	* Will register the notifier into a notification chain that gets called
	339	* upon changes to the target value for the device.
	340	*/
	341	int dev_pm_qos_add_notifier(struct device dev, struct notifier_block notifier)
	342	{
	343	int retval = 0;
	344
	345	mutex_lock(&dev_pm_qos_mtx);
	346
1a9a9152 RW	347	/* Silently return if the constraints object is not present. */
	348	if (dev->power.constraints)
	349	retval = blocking_notifier_chain_register(
	350	dev->power.constraints->notifiers,
	351	notifier);
91ff4cb8	352
91ff4cb8 JP	353	mutex_unlock(&dev_pm_qos_mtx);
	354	return retval;
	355	}
	356	EXPORT_SYMBOL_GPL(dev_pm_qos_add_notifier);
	357
	358	/**
	359	* dev_pm_qos_remove_notifier - deletes notification for changes to target value
	360	* of per-device PM QoS constraints
	361	*
	362	* @dev: target device for the constraint
	363	* @notifier: notifier block to be removed.
	364	*
	365	* Will remove the notifier from the notification chain that gets called
	366	* upon changes to the target value.
	367	*/
	368	int dev_pm_qos_remove_notifier(struct device *dev,
	369	struct notifier_block *notifier)
	370	{
	371	int retval = 0;
	372
	373	mutex_lock(&dev_pm_qos_mtx);
	374
1a9a9152 RW	375	/* Silently return if the constraints object is not present. */
	376	if (dev->power.constraints)
	377	retval = blocking_notifier_chain_unregister(
	378	dev->power.constraints->notifiers,
	379	notifier);
91ff4cb8	380
91ff4cb8 JP	381	mutex_unlock(&dev_pm_qos_mtx);
	382	return retval;
	383	}
	384	EXPORT_SYMBOL_GPL(dev_pm_qos_remove_notifier);
b66213cd JP	385
	386	/**
	387	* dev_pm_qos_add_global_notifier - sets notification entry for changes to
	388	* target value of the PM QoS constraints for any device
	389	*
	390	* @notifier: notifier block managed by caller.
	391	*
	392	* Will register the notifier into a notification chain that gets called
	393	* upon changes to the target value for any device.
	394	*/
	395	int dev_pm_qos_add_global_notifier(struct notifier_block *notifier)
	396	{
	397	return blocking_notifier_chain_register(&dev_pm_notifiers, notifier);
	398	}
	399	EXPORT_SYMBOL_GPL(dev_pm_qos_add_global_notifier);
	400
	401	/**
	402	* dev_pm_qos_remove_global_notifier - deletes notification for changes to
	403	* target value of PM QoS constraints for any device
	404	*
	405	* @notifier: notifier block to be removed.
	406	*
	407	* Will remove the notifier from the notification chain that gets called
	408	* upon changes to the target value for any device.
	409	*/
	410	int dev_pm_qos_remove_global_notifier(struct notifier_block *notifier)
	411	{
	412	return blocking_notifier_chain_unregister(&dev_pm_notifiers, notifier);
	413	}
	414	EXPORT_SYMBOL_GPL(dev_pm_qos_remove_global_notifier);