/*
   * This module exposes the interface to kernel space for specifying
   * QoS dependencies.  It provides infrastructure for registration of:
   *
   * Dependents on a QoS value : register requirements
   * 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 requirements, notifiers
   *
   * User mode requirements 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
   * requirement is removed and a new qos target is computed.  This way when the
   * requirement 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>

   */
  
  #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 requirements 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
   */
  struct requirement_list {
  	struct list_head list;
  	union {
  		s32 value;
  		s32 usec;
  		s32 kbps;
  	};
  	char *name;
  };
  
  static s32 max_compare(s32 v1, s32 v2);
  static s32 min_compare(s32 v1, s32 v2);
  
  struct pm_qos_object {
  	struct requirement_list requirements;
  	struct blocking_notifier_head *notifiers;
  	struct miscdevice pm_qos_power_miscdev;
  	char *name;
  	s32 default_value;

  	atomic_t target_value;

  	s32 (*comparitor)(s32, s32);
  };
  
  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 = {
  	.requirements = {LIST_HEAD_INIT(cpu_dma_pm_qos.requirements.list)},
  	.notifiers = &cpu_dma_lat_notifier,
  	.name = "cpu_dma_latency",
  	.default_value = 2000 * USEC_PER_SEC,

  	.target_value = ATOMIC_INIT(2000 * USEC_PER_SEC),

  	.comparitor = min_compare
  };
  
  static BLOCKING_NOTIFIER_HEAD(network_lat_notifier);
  static struct pm_qos_object network_lat_pm_qos = {
  	.requirements = {LIST_HEAD_INIT(network_lat_pm_qos.requirements.list)},
  	.notifiers = &network_lat_notifier,
  	.name = "network_latency",
  	.default_value = 2000 * USEC_PER_SEC,

  	.target_value = ATOMIC_INIT(2000 * USEC_PER_SEC),

  	.comparitor = min_compare
  };
  
  
  static BLOCKING_NOTIFIER_HEAD(network_throughput_notifier);
  static struct pm_qos_object network_throughput_pm_qos = {
  	.requirements =
  		{LIST_HEAD_INIT(network_throughput_pm_qos.requirements.list)},
  	.notifiers = &network_throughput_notifier,
  	.name = "network_throughput",
  	.default_value = 0,

  	.target_value = ATOMIC_INIT(0),

  	.comparitor = max_compare
  };
  
  
  static struct pm_qos_object *pm_qos_array[] = {
  	&null_pm_qos,
  	&cpu_dma_pm_qos,
  	&network_lat_pm_qos,
  	&network_throughput_pm_qos
  };
  
  static DEFINE_SPINLOCK(pm_qos_lock);
  
  static ssize_t pm_qos_power_write(struct file *filp, const 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,
  	.open = pm_qos_power_open,
  	.release = pm_qos_power_release,
  };
  
  /* static helper functions */
  static s32 max_compare(s32 v1, s32 v2)
  {
  	return max(v1, v2);
  }
  
  static s32 min_compare(s32 v1, s32 v2)
  {
  	return min(v1, v2);
  }
  
  
  static void update_target(int target)
  {
  	s32 extreme_value;
  	struct requirement_list *node;
  	unsigned long flags;
  	int call_notifier = 0;
  
  	spin_lock_irqsave(&pm_qos_lock, flags);
  	extreme_value = pm_qos_array[target]->default_value;
  	list_for_each_entry(node,
  			&pm_qos_array[target]->requirements.list, list) {
  		extreme_value = pm_qos_array[target]->comparitor(
  				extreme_value, node->value);
  	}

  	if (atomic_read(&pm_qos_array[target]->target_value) != extreme_value) {

  		call_notifier = 1;

  		atomic_set(&pm_qos_array[target]->target_value, extreme_value);

  		pr_debug(KERN_ERR "new target for qos %d is %d
  ", target,

  			atomic_read(&pm_qos_array[target]->target_value));

  	}
  	spin_unlock_irqrestore(&pm_qos_lock, flags);
  
  	if (call_notifier)
  		blocking_notifier_call_chain(pm_qos_array[target]->notifiers,
  			(unsigned long) extreme_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_requirement - 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_requirement(int pm_qos_class)
  {

  	return atomic_read(&pm_qos_array[pm_qos_class]->target_value);

  }
  EXPORT_SYMBOL_GPL(pm_qos_requirement);
  
  /**
   * pm_qos_add_requirement - inserts new qos request into the list
   * @pm_qos_class: identifies which list of qos request to us
   * @name: identifies the request
   * @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.

   */
  int pm_qos_add_requirement(int pm_qos_class, char *name, s32 value)
  {
  	struct requirement_list *dep;
  	unsigned long flags;
  
  	dep = kzalloc(sizeof(struct requirement_list), GFP_KERNEL);
  	if (dep) {
  		if (value == PM_QOS_DEFAULT_VALUE)
  			dep->value = pm_qos_array[pm_qos_class]->default_value;
  		else
  			dep->value = value;
  		dep->name = kstrdup(name, GFP_KERNEL);
  		if (!dep->name)
  			goto cleanup;
  
  		spin_lock_irqsave(&pm_qos_lock, flags);
  		list_add(&dep->list,
  			&pm_qos_array[pm_qos_class]->requirements.list);
  		spin_unlock_irqrestore(&pm_qos_lock, flags);
  		update_target(pm_qos_class);
  
  		return 0;
  	}
  
  cleanup:
  	kfree(dep);
  	return -ENOMEM;
  }
  EXPORT_SYMBOL_GPL(pm_qos_add_requirement);
  
  /**
   * pm_qos_update_requirement - modifies an existing qos request
   * @pm_qos_class: identifies which list of qos request to us
   * @name: identifies the request
   * @value: defines the qos request
   *

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

   * with updating the target pm_qos_class value.
   *

   * If the named request isn't in the list then no change is made.

   */
  int pm_qos_update_requirement(int pm_qos_class, char *name, s32 new_value)
  {
  	unsigned long flags;
  	struct requirement_list *node;
  	int pending_update = 0;
  
  	spin_lock_irqsave(&pm_qos_lock, flags);
  	list_for_each_entry(node,
  		&pm_qos_array[pm_qos_class]->requirements.list, list) {
  		if (strcmp(node->name, name) == 0) {
  			if (new_value == PM_QOS_DEFAULT_VALUE)
  				node->value =
  				pm_qos_array[pm_qos_class]->default_value;
  			else
  				node->value = new_value;
  			pending_update = 1;
  			break;
  		}
  	}
  	spin_unlock_irqrestore(&pm_qos_lock, flags);
  	if (pending_update)
  		update_target(pm_qos_class);
  
  	return 0;
  }
  EXPORT_SYMBOL_GPL(pm_qos_update_requirement);
  
  /**
   * pm_qos_remove_requirement - modifies an existing qos request
   * @pm_qos_class: identifies which list of qos request to us
   * @name: identifies the request
   *

   * Will remove named qos request from pm_qos_class list of parameters and

   * recompute the current target value for the pm_qos_class.
   */
  void pm_qos_remove_requirement(int pm_qos_class, char *name)
  {
  	unsigned long flags;
  	struct requirement_list *node;
  	int pending_update = 0;
  
  	spin_lock_irqsave(&pm_qos_lock, flags);
  	list_for_each_entry(node,
  		&pm_qos_array[pm_qos_class]->requirements.list, list) {
  		if (strcmp(node->name, name) == 0) {
  			kfree(node->name);
  			list_del(&node->list);
  			kfree(node);
  			pending_update = 1;
  			break;
  		}
  	}
  	spin_unlock_irqrestore(&pm_qos_lock, flags);
  	if (pending_update)
  		update_target(pm_qos_class);
  }
  EXPORT_SYMBOL_GPL(pm_qos_remove_requirement);
  
  /**
   * 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);

  #define PID_NAME_LEN 32

  
  static int pm_qos_power_open(struct inode *inode, struct file *filp)
  {
  	int ret;
  	long pm_qos_class;

  	char name[PID_NAME_LEN];

  
  	pm_qos_class = find_pm_qos_object_by_minor(iminor(inode));
  	if (pm_qos_class >= 0) {
  		filp->private_data = (void *)pm_qos_class;

  		snprintf(name, PID_NAME_LEN, "process_%d", current->pid);

  		ret = pm_qos_add_requirement(pm_qos_class, name,
  					PM_QOS_DEFAULT_VALUE);

  		if (ret >= 0)

  			return 0;
  	}

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

  	char name[PID_NAME_LEN];

  
  	pm_qos_class = (long)filp->private_data;

  	snprintf(name, PID_NAME_LEN, "process_%d", current->pid);

  	pm_qos_remove_requirement(pm_qos_class, name);
  
  	return 0;
  }
  
  static ssize_t pm_qos_power_write(struct file *filp, const char __user *buf,
  		size_t count, loff_t *f_pos)
  {
  	s32 value;
  	int pm_qos_class;

  	char name[PID_NAME_LEN];

  
  	pm_qos_class = (long)filp->private_data;
  	if (count != sizeof(s32))
  		return -EINVAL;
  	if (copy_from_user(&value, buf, sizeof(s32)))
  		return -EFAULT;

  	snprintf(name, PID_NAME_LEN, "process_%d", current->pid);

  	pm_qos_update_requirement(pm_qos_class, name, value);
  
  	return  sizeof(s32);
  }
  
  
  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);