/*
   * 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.
   *
   * This routine must be called with dev->power.lock held.
   */
  s32 __dev_pm_qos_read_value(struct device *dev)
  {
  	struct pm_qos_constraints *c = dev->power.constraints;
  
  	return c ? pm_qos_read_value(c) : 0;
  }
  
  /**
   * dev_pm_qos_read_value - Get PM QoS constraint for a given device (locked).

   * @dev: Device to get the PM QoS constraint value for.
   */
  s32 dev_pm_qos_read_value(struct device *dev)
  {

  	unsigned long flags;

  	s32 ret;

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

  	ret = __dev_pm_qos_read_value(dev);

  	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
  ", __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
  ", __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
  ", __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);

  
  /**
   * dev_pm_qos_add_ancestor_request - Add PM QoS request for device's ancestor.
   * @dev: Device whose ancestor to add the request for.
   * @req: Pointer to the preallocated handle.
   * @value: Constraint latency value.
   */
  int dev_pm_qos_add_ancestor_request(struct device *dev,
  				    struct dev_pm_qos_request *req, s32 value)
  {
  	struct device *ancestor = dev->parent;
  	int error = -ENODEV;
  
  	while (ancestor && !ancestor->power.ignore_children)
  		ancestor = ancestor->parent;
  
  	if (ancestor)
  		error = dev_pm_qos_add_request(ancestor, req, value);
  
  	if (error)
  		req->dev = NULL;
  
  	return error;
  }
  EXPORT_SYMBOL_GPL(dev_pm_qos_add_ancestor_request);