/*
   * This module exposes the interface to kernel space for specifying
   * 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.
   *
   * There are 3 basic classes of QoS parameter: latency, timeout, throughput
   * each have defined units:
   * latency: usec
   * timeout: usec <-- currently not used.
   * throughput: kbs (kilo byte / sec)
   *

   * There are lists of pm_qos_objects each one wrapping requests, notifiers

   *

   * User mode requests on a QOS parameter register themselves to the

   * subsystem by opening the device node /dev/... and writing there request to
   * the node.  As long as the process holds a file handle open to the node the
   * client continues to be accounted for.  Upon file release the usermode

   * request is removed and a new qos target is computed.  This way when the
   * request that the application has is cleaned up when closes the file

   * pointer or exits the pm_qos_object will get an opportunity to clean up.
   *

   * Mark Gross <mgross@linux.intel.com>

   */

  /*#define DEBUG*/

  #include <linux/pm_qos_params.h>
  #include <linux/sched.h>
  #include <linux/spinlock.h>
  #include <linux/slab.h>
  #include <linux/time.h>
  #include <linux/fs.h>
  #include <linux/device.h>
  #include <linux/miscdevice.h>
  #include <linux/string.h>
  #include <linux/platform_device.h>
  #include <linux/init.h>
  
  #include <linux/uaccess.h>
  
  /*

   * locking rule: all changes to requests or notifiers lists

   * or pm_qos_object list and pm_qos_objects need to happen with pm_qos_lock
   * held, taken with _irqsave.  One lock to rule them all
   */

  enum pm_qos_type {
  	PM_QOS_MAX,		/* return the largest value */
  	PM_QOS_MIN		/* return the smallest value */
  };

  
  struct pm_qos_object {

  	struct plist_head requests;

  	struct blocking_notifier_head *notifiers;
  	struct miscdevice pm_qos_power_miscdev;
  	char *name;
  	s32 default_value;

  	enum pm_qos_type type;

  };

  static DEFINE_SPINLOCK(pm_qos_lock);

  static struct pm_qos_object null_pm_qos;
  static BLOCKING_NOTIFIER_HEAD(cpu_dma_lat_notifier);
  static struct pm_qos_object cpu_dma_pm_qos = {

  	.requests = PLIST_HEAD_INIT(cpu_dma_pm_qos.requests, pm_qos_lock),

  	.notifiers = &cpu_dma_lat_notifier,
  	.name = "cpu_dma_latency",
  	.default_value = 2000 * USEC_PER_SEC,

  	.type = PM_QOS_MIN,

  };
  
  static BLOCKING_NOTIFIER_HEAD(network_lat_notifier);
  static struct pm_qos_object network_lat_pm_qos = {

  	.requests = PLIST_HEAD_INIT(network_lat_pm_qos.requests, pm_qos_lock),

  	.notifiers = &network_lat_notifier,
  	.name = "network_latency",
  	.default_value = 2000 * USEC_PER_SEC,

  	.type = PM_QOS_MIN

  };
  
  
  static BLOCKING_NOTIFIER_HEAD(network_throughput_notifier);
  static struct pm_qos_object network_throughput_pm_qos = {

  	.requests = PLIST_HEAD_INIT(network_throughput_pm_qos.requests, pm_qos_lock),

  	.notifiers = &network_throughput_notifier,
  	.name = "network_throughput",
  	.default_value = 0,

  	.type = PM_QOS_MAX,

  };
  
  
  static struct pm_qos_object *pm_qos_array[] = {
  	&null_pm_qos,
  	&cpu_dma_pm_qos,
  	&network_lat_pm_qos,
  	&network_throughput_pm_qos
  };

  static ssize_t pm_qos_power_write(struct file *filp, const char __user *buf,
  		size_t count, loff_t *f_pos);

  static ssize_t pm_qos_power_read(struct file *filp, char __user *buf,
  		size_t count, loff_t *f_pos);

  static int pm_qos_power_open(struct inode *inode, struct file *filp);
  static int pm_qos_power_release(struct inode *inode, struct file *filp);
  
  static const struct file_operations pm_qos_power_fops = {
  	.write = pm_qos_power_write,

  	.read = pm_qos_power_read,

  	.open = pm_qos_power_open,
  	.release = pm_qos_power_release,

  	.llseek = noop_llseek,

  };

  /* unlocked internal variant */
  static inline int pm_qos_get_value(struct pm_qos_object *o)

  {

  	if (plist_head_empty(&o->requests))
  		return o->default_value;

  	switch (o->type) {
  	case PM_QOS_MIN:

  		return plist_first(&o->requests)->prio;

  	case PM_QOS_MAX:

  		return plist_last(&o->requests)->prio;

  	default:
  		/* runtime check for not using enum */
  		BUG();
  	}
  }
  
  static void update_target(struct pm_qos_object *o, struct plist_node *node,
  			  int del, int value)

  {

  	unsigned long flags;

  	int prev_value, curr_value;

  
  	spin_lock_irqsave(&pm_qos_lock, flags);

  	prev_value = pm_qos_get_value(o);
  	/* PM_QOS_DEFAULT_VALUE is a signal that the value is unchanged */
  	if (value != PM_QOS_DEFAULT_VALUE) {
  		/*
  		 * to change the list, we atomically remove, reinit
  		 * with new value and add, then see if the extremal
  		 * changed
  		 */
  		plist_del(node, &o->requests);
  		plist_node_init(node, value);
  		plist_add(node, &o->requests);
  	} else if (del) {
  		plist_del(node, &o->requests);
  	} else {
  		plist_add(node, &o->requests);

  	}

  	curr_value = pm_qos_get_value(o);

  	spin_unlock_irqrestore(&pm_qos_lock, flags);

  	if (prev_value != curr_value)
  		blocking_notifier_call_chain(o->notifiers,
  					     (unsigned long)curr_value,
  					     NULL);

  }
  
  static int register_pm_qos_misc(struct pm_qos_object *qos)
  {
  	qos->pm_qos_power_miscdev.minor = MISC_DYNAMIC_MINOR;
  	qos->pm_qos_power_miscdev.name = qos->name;
  	qos->pm_qos_power_miscdev.fops = &pm_qos_power_fops;
  
  	return misc_register(&qos->pm_qos_power_miscdev);
  }
  
  static int find_pm_qos_object_by_minor(int minor)
  {
  	int pm_qos_class;
  
  	for (pm_qos_class = 0;
  		pm_qos_class < PM_QOS_NUM_CLASSES; pm_qos_class++) {
  		if (minor ==
  			pm_qos_array[pm_qos_class]->pm_qos_power_miscdev.minor)
  			return pm_qos_class;
  	}
  	return -1;
  }
  
  /**

   * pm_qos_request - returns current system wide qos expectation

   * @pm_qos_class: identification of which qos value is requested
   *
   * This function returns the current target value in an atomic manner.
   */

  int pm_qos_request(int pm_qos_class)

  {

  	unsigned long flags;
  	int value;
  
  	spin_lock_irqsave(&pm_qos_lock, flags);
  	value = pm_qos_get_value(pm_qos_array[pm_qos_class]);
  	spin_unlock_irqrestore(&pm_qos_lock, flags);
  
  	return value;

  }

  EXPORT_SYMBOL_GPL(pm_qos_request);

  int pm_qos_request_active(struct pm_qos_request_list *req)
  {
  	return req->pm_qos_class != 0;
  }
  EXPORT_SYMBOL_GPL(pm_qos_request_active);

  /**

   * pm_qos_add_request - inserts new qos request into the list

   * @dep: pointer to a preallocated handle
   * @pm_qos_class: identifies which list of qos request to use

   * @value: defines the qos request
   *
   * This function inserts a new entry in the pm_qos_class list of requested qos

   * performance characteristics.  It recomputes the aggregate QoS expectations

   * for the pm_qos_class of parameters and initializes the pm_qos_request_list
   * handle.  Caller needs to save this handle for later use in updates and
   * removal.

   */

  void pm_qos_add_request(struct pm_qos_request_list *dep,
  			int pm_qos_class, s32 value)

  {

  	struct pm_qos_object *o =  pm_qos_array[pm_qos_class];
  	int new_value;

  	if (pm_qos_request_active(dep)) {
  		WARN(1, KERN_ERR "pm_qos_add_request() called for already added request
  ");
  		return;
  	}
  	if (value == PM_QOS_DEFAULT_VALUE)
  		new_value = o->default_value;
  	else
  		new_value = value;
  	plist_node_init(&dep->list, new_value);
  	dep->pm_qos_class = pm_qos_class;
  	update_target(o, &dep->list, 0, PM_QOS_DEFAULT_VALUE);

  }

  EXPORT_SYMBOL_GPL(pm_qos_add_request);

  
  /**

   * pm_qos_update_request - modifies an existing qos request
   * @pm_qos_req : handle to list element holding a pm_qos request to use

   * @value: defines the qos request
   *

   * Updates an existing qos request for the pm_qos_class of parameters along

   * with updating the target pm_qos_class value.
   *

   * Attempts are made to make this code callable on hot code paths.

   */

  void pm_qos_update_request(struct pm_qos_request_list *pm_qos_req,

  			   s32 new_value)

  {

  	s32 temp;

  	struct pm_qos_object *o;

  	if (!pm_qos_req) /*guard against callers passing in null */
  		return;

  	if (!pm_qos_request_active(pm_qos_req)) {
  		WARN(1, KERN_ERR "pm_qos_update_request() called for unknown object
  ");
  		return;
  	}

  	o = pm_qos_array[pm_qos_req->pm_qos_class];
  
  	if (new_value == PM_QOS_DEFAULT_VALUE)
  		temp = o->default_value;
  	else
  		temp = new_value;
  
  	if (temp != pm_qos_req->list.prio)
  		update_target(o, &pm_qos_req->list, 0, temp);

  }

  EXPORT_SYMBOL_GPL(pm_qos_update_request);

  
  /**

   * pm_qos_remove_request - modifies an existing qos request
   * @pm_qos_req: handle to request list element

   *

   * Will remove pm qos request from the list of requests and
   * recompute the current target value for the pm_qos_class.  Call this
   * on slow code paths.

   */

  void pm_qos_remove_request(struct pm_qos_request_list *pm_qos_req)

  {

  	struct pm_qos_object *o;

  
  	if (pm_qos_req == NULL)
  		return;
  		/* silent return to keep pcm code cleaner */

  	if (!pm_qos_request_active(pm_qos_req)) {
  		WARN(1, KERN_ERR "pm_qos_remove_request() called for unknown object
  ");
  		return;
  	}

  	o = pm_qos_array[pm_qos_req->pm_qos_class];
  	update_target(o, &pm_qos_req->list, 1, PM_QOS_DEFAULT_VALUE);

  	memset(pm_qos_req, 0, sizeof(*pm_qos_req));

  }

  EXPORT_SYMBOL_GPL(pm_qos_remove_request);

  
  /**
   * pm_qos_add_notifier - sets notification entry for changes to target value
   * @pm_qos_class: identifies which qos target changes should be notified.
   * @notifier: notifier block managed by caller.
   *
   * will register the notifier into a notification chain that gets called

   * upon changes to the pm_qos_class target value.

   */

  int pm_qos_add_notifier(int pm_qos_class, struct notifier_block *notifier)

  {
  	int retval;
  
  	retval = blocking_notifier_chain_register(
  			pm_qos_array[pm_qos_class]->notifiers, notifier);
  
  	return retval;
  }
  EXPORT_SYMBOL_GPL(pm_qos_add_notifier);
  
  /**
   * pm_qos_remove_notifier - deletes notification entry from chain.
   * @pm_qos_class: identifies which qos target changes are notified.
   * @notifier: notifier block to be removed.
   *
   * will remove the notifier from the notification chain that gets called

   * upon changes to the pm_qos_class target value.

   */
  int pm_qos_remove_notifier(int pm_qos_class, struct notifier_block *notifier)
  {
  	int retval;
  
  	retval = blocking_notifier_chain_unregister(
  			pm_qos_array[pm_qos_class]->notifiers, notifier);
  
  	return retval;
  }
  EXPORT_SYMBOL_GPL(pm_qos_remove_notifier);

  static int pm_qos_power_open(struct inode *inode, struct file *filp)
  {

  	long pm_qos_class;
  
  	pm_qos_class = find_pm_qos_object_by_minor(iminor(inode));
  	if (pm_qos_class >= 0) {

                 struct pm_qos_request_list *req = kzalloc(sizeof(*req), GFP_KERNEL);

  		if (!req)
  			return -ENOMEM;
  
  		pm_qos_add_request(req, pm_qos_class, PM_QOS_DEFAULT_VALUE);
  		filp->private_data = req;

  
  		if (filp->private_data)

  			return 0;
  	}

  	return -EPERM;
  }
  
  static int pm_qos_power_release(struct inode *inode, struct file *filp)
  {

  	struct pm_qos_request_list *req;

  	req = filp->private_data;

  	pm_qos_remove_request(req);

  	kfree(req);

  
  	return 0;
  }

  static ssize_t pm_qos_power_read(struct file *filp, char __user *buf,
  		size_t count, loff_t *f_pos)
  {
  	s32 value;
  	unsigned long flags;
  	struct pm_qos_object *o;

  	struct pm_qos_request_list *pm_qos_req = filp->private_data;

  
  	if (!pm_qos_req)
  		return -EINVAL;
  	if (!pm_qos_request_active(pm_qos_req))
  		return -EINVAL;
  
  	o = pm_qos_array[pm_qos_req->pm_qos_class];
  	spin_lock_irqsave(&pm_qos_lock, flags);
  	value = pm_qos_get_value(o);
  	spin_unlock_irqrestore(&pm_qos_lock, flags);
  
  	return simple_read_from_buffer(buf, count, f_pos, &value, sizeof(s32));
  }

  static ssize_t pm_qos_power_write(struct file *filp, const char __user *buf,
  		size_t count, loff_t *f_pos)
  {
  	s32 value;

  	int x;
  	char ascii_value[11];
  	struct pm_qos_request_list *pm_qos_req;
  
  	if (count == sizeof(s32)) {
  		if (copy_from_user(&value, buf, sizeof(s32)))
  			return -EFAULT;
  	} else if (count == 11) { /* len('0x12345678/0') */
  		if (copy_from_user(ascii_value, buf, 11))
  			return -EFAULT;

  		if (strlen(ascii_value) != 10)
  			return -EINVAL;

  		x = sscanf(ascii_value, "%x", &value);
  		if (x != 1)
  			return -EINVAL;

  		pr_debug("%s, %d, 0x%x
  ", ascii_value, x, value);

  	} else

  		return -EINVAL;

  	pm_qos_req = filp->private_data;

  	pm_qos_update_request(pm_qos_req, value);
  
  	return count;

  }
  
  
  static int __init pm_qos_power_init(void)
  {
  	int ret = 0;
  
  	ret = register_pm_qos_misc(&cpu_dma_pm_qos);
  	if (ret < 0) {
  		printk(KERN_ERR "pm_qos_param: cpu_dma_latency setup failed
  ");
  		return ret;
  	}
  	ret = register_pm_qos_misc(&network_lat_pm_qos);
  	if (ret < 0) {
  		printk(KERN_ERR "pm_qos_param: network_latency setup failed
  ");
  		return ret;
  	}
  	ret = register_pm_qos_misc(&network_throughput_pm_qos);
  	if (ret < 0)
  		printk(KERN_ERR
  			"pm_qos_param: network_throughput setup failed
  ");
  
  	return ret;
  }
  
  late_initcall(pm_qos_power_init);