/*
* 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>
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 (dev_pm_qos_request_active(req)) {
WARN(1, KERN_ERR "dev_pm_qos_add_request() called for already "
"added request\n");
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 (!dev_pm_qos_request_active(req)) {
WARN(1, KERN_ERR "dev_pm_qos_update_request() called for "
"unknown object\n");
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 (!dev_pm_qos_request_active(req)) {
WARN(1, KERN_ERR "dev_pm_qos_remove_request() called for "
"unknown object\n");
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);
