![Paul Gortmaker](/assets/img/avatar_default.png)
Most of these files were implicitly getting EXPORT_SYMBOL via device.h which was including module.h, but that path will be broken soon. [ with input from Stephen Rothwell <sfr@canb.auug.org.au> ] Signed-off-by: Paul Gortmaker <paul.gortmaker@windriver.com>
421 lines
12 KiB
C
421 lines
12 KiB
C
/*
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* Devices PM QoS constraints management
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*
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* Copyright (C) 2011 Texas Instruments, Inc.
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*
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* This program is free software; you can redistribute it and/or modify
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* it under the terms of the GNU General Public License version 2 as
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* published by the Free Software Foundation.
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*
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*
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* This module exposes the interface to kernel space for specifying
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* per-device PM QoS dependencies. It provides infrastructure for registration
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* of:
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*
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* Dependents on a QoS value : register requests
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* Watchers of QoS value : get notified when target QoS value changes
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*
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* This QoS design is best effort based. Dependents register their QoS needs.
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* Watchers register to keep track of the current QoS needs of the system.
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* Watchers can register different types of notification callbacks:
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* . a per-device notification callback using the dev_pm_qos_*_notifier API.
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* The notification chain data is stored in the per-device constraint
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* data struct.
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* . a system-wide notification callback using the dev_pm_qos_*_global_notifier
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* API. The notification chain data is stored in a static variable.
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*
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* Note about the per-device constraint data struct allocation:
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* . The per-device constraints data struct ptr is tored into the device
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* dev_pm_info.
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* . To minimize the data usage by the per-device constraints, the data struct
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* is only allocated at the first call to dev_pm_qos_add_request.
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* . The data is later free'd when the device is removed from the system.
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* . A global mutex protects the constraints users from the data being
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* allocated and free'd.
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*/
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#include <linux/pm_qos.h>
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#include <linux/spinlock.h>
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#include <linux/slab.h>
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#include <linux/device.h>
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#include <linux/mutex.h>
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#include <linux/export.h>
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static DEFINE_MUTEX(dev_pm_qos_mtx);
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static BLOCKING_NOTIFIER_HEAD(dev_pm_notifiers);
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/**
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* dev_pm_qos_read_value - Get PM QoS constraint for a given device.
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* @dev: Device to get the PM QoS constraint value for.
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*/
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s32 dev_pm_qos_read_value(struct device *dev)
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{
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struct pm_qos_constraints *c;
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unsigned long flags;
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s32 ret = 0;
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spin_lock_irqsave(&dev->power.lock, flags);
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c = dev->power.constraints;
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if (c)
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ret = pm_qos_read_value(c);
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spin_unlock_irqrestore(&dev->power.lock, flags);
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return ret;
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}
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/*
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* apply_constraint
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* @req: constraint request to apply
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* @action: action to perform add/update/remove, of type enum pm_qos_req_action
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* @value: defines the qos request
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*
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* Internal function to update the constraints list using the PM QoS core
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* code and if needed call the per-device and the global notification
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* callbacks
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*/
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static int apply_constraint(struct dev_pm_qos_request *req,
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enum pm_qos_req_action action, int value)
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{
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int ret, curr_value;
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ret = pm_qos_update_target(req->dev->power.constraints,
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&req->node, action, value);
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if (ret) {
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/* Call the global callbacks if needed */
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curr_value = pm_qos_read_value(req->dev->power.constraints);
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blocking_notifier_call_chain(&dev_pm_notifiers,
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(unsigned long)curr_value,
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req);
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}
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return ret;
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}
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/*
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* dev_pm_qos_constraints_allocate
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* @dev: device to allocate data for
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*
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* Called at the first call to add_request, for constraint data allocation
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* Must be called with the dev_pm_qos_mtx mutex held
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*/
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static int dev_pm_qos_constraints_allocate(struct device *dev)
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{
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struct pm_qos_constraints *c;
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struct blocking_notifier_head *n;
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c = kzalloc(sizeof(*c), GFP_KERNEL);
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if (!c)
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return -ENOMEM;
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n = kzalloc(sizeof(*n), GFP_KERNEL);
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if (!n) {
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kfree(c);
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return -ENOMEM;
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}
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BLOCKING_INIT_NOTIFIER_HEAD(n);
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plist_head_init(&c->list);
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c->target_value = PM_QOS_DEV_LAT_DEFAULT_VALUE;
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c->default_value = PM_QOS_DEV_LAT_DEFAULT_VALUE;
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c->type = PM_QOS_MIN;
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c->notifiers = n;
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spin_lock_irq(&dev->power.lock);
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dev->power.constraints = c;
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spin_unlock_irq(&dev->power.lock);
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return 0;
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}
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/**
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* dev_pm_qos_constraints_init - Initalize device's PM QoS constraints pointer.
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* @dev: target device
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*
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* Called from the device PM subsystem during device insertion under
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* device_pm_lock().
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*/
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void dev_pm_qos_constraints_init(struct device *dev)
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{
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mutex_lock(&dev_pm_qos_mtx);
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dev->power.constraints = NULL;
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dev->power.power_state = PMSG_ON;
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mutex_unlock(&dev_pm_qos_mtx);
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}
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/**
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* dev_pm_qos_constraints_destroy
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* @dev: target device
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*
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* Called from the device PM subsystem on device removal under device_pm_lock().
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*/
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void dev_pm_qos_constraints_destroy(struct device *dev)
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{
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struct dev_pm_qos_request *req, *tmp;
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struct pm_qos_constraints *c;
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mutex_lock(&dev_pm_qos_mtx);
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dev->power.power_state = PMSG_INVALID;
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c = dev->power.constraints;
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if (!c)
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goto out;
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/* Flush the constraints list for the device */
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plist_for_each_entry_safe(req, tmp, &c->list, node) {
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/*
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* Update constraints list and call the notification
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* callbacks if needed
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*/
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apply_constraint(req, PM_QOS_REMOVE_REQ, PM_QOS_DEFAULT_VALUE);
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memset(req, 0, sizeof(*req));
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}
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spin_lock_irq(&dev->power.lock);
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dev->power.constraints = NULL;
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spin_unlock_irq(&dev->power.lock);
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kfree(c->notifiers);
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kfree(c);
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out:
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mutex_unlock(&dev_pm_qos_mtx);
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}
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/**
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* dev_pm_qos_add_request - inserts new qos request into the list
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* @dev: target device for the constraint
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* @req: pointer to a preallocated handle
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* @value: defines the qos request
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*
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* This function inserts a new entry in the device constraints list of
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* requested qos performance characteristics. It recomputes the aggregate
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* QoS expectations of parameters and initializes the dev_pm_qos_request
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* handle. Caller needs to save this handle for later use in updates and
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* removal.
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*
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* Returns 1 if the aggregated constraint value has changed,
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* 0 if the aggregated constraint value has not changed,
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* -EINVAL in case of wrong parameters, -ENOMEM if there's not enough memory
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* to allocate for data structures, -ENODEV if the device has just been removed
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* from the system.
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*/
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int dev_pm_qos_add_request(struct device *dev, struct dev_pm_qos_request *req,
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s32 value)
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{
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int ret = 0;
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if (!dev || !req) /*guard against callers passing in null */
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return -EINVAL;
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if (dev_pm_qos_request_active(req)) {
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WARN(1, KERN_ERR "dev_pm_qos_add_request() called for already "
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"added request\n");
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return -EINVAL;
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}
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req->dev = dev;
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mutex_lock(&dev_pm_qos_mtx);
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if (!dev->power.constraints) {
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if (dev->power.power_state.event == PM_EVENT_INVALID) {
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/* The device has been removed from the system. */
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req->dev = NULL;
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ret = -ENODEV;
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goto out;
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} else {
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/*
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* Allocate the constraints data on the first call to
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* add_request, i.e. only if the data is not already
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* allocated and if the device has not been removed.
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*/
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ret = dev_pm_qos_constraints_allocate(dev);
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}
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}
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if (!ret)
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ret = apply_constraint(req, PM_QOS_ADD_REQ, value);
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out:
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mutex_unlock(&dev_pm_qos_mtx);
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return ret;
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}
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EXPORT_SYMBOL_GPL(dev_pm_qos_add_request);
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/**
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* dev_pm_qos_update_request - modifies an existing qos request
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* @req : handle to list element holding a dev_pm_qos request to use
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* @new_value: defines the qos request
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*
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* Updates an existing dev PM qos request along with updating the
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* target value.
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*
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* Attempts are made to make this code callable on hot code paths.
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*
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* Returns 1 if the aggregated constraint value has changed,
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* 0 if the aggregated constraint value has not changed,
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* -EINVAL in case of wrong parameters, -ENODEV if the device has been
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* removed from the system
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*/
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int dev_pm_qos_update_request(struct dev_pm_qos_request *req,
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s32 new_value)
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{
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int ret = 0;
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if (!req) /*guard against callers passing in null */
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return -EINVAL;
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if (!dev_pm_qos_request_active(req)) {
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WARN(1, KERN_ERR "dev_pm_qos_update_request() called for "
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"unknown object\n");
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return -EINVAL;
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}
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mutex_lock(&dev_pm_qos_mtx);
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if (req->dev->power.constraints) {
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if (new_value != req->node.prio)
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ret = apply_constraint(req, PM_QOS_UPDATE_REQ,
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new_value);
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} else {
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/* Return if the device has been removed */
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ret = -ENODEV;
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}
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mutex_unlock(&dev_pm_qos_mtx);
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return ret;
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}
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EXPORT_SYMBOL_GPL(dev_pm_qos_update_request);
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/**
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* dev_pm_qos_remove_request - modifies an existing qos request
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* @req: handle to request list element
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*
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* Will remove pm qos request from the list of constraints and
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* recompute the current target value. Call this on slow code paths.
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*
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* Returns 1 if the aggregated constraint value has changed,
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* 0 if the aggregated constraint value has not changed,
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* -EINVAL in case of wrong parameters, -ENODEV if the device has been
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* removed from the system
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*/
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int dev_pm_qos_remove_request(struct dev_pm_qos_request *req)
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{
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int ret = 0;
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if (!req) /*guard against callers passing in null */
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return -EINVAL;
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if (!dev_pm_qos_request_active(req)) {
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WARN(1, KERN_ERR "dev_pm_qos_remove_request() called for "
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"unknown object\n");
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return -EINVAL;
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}
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mutex_lock(&dev_pm_qos_mtx);
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if (req->dev->power.constraints) {
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ret = apply_constraint(req, PM_QOS_REMOVE_REQ,
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PM_QOS_DEFAULT_VALUE);
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memset(req, 0, sizeof(*req));
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} else {
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/* Return if the device has been removed */
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ret = -ENODEV;
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}
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mutex_unlock(&dev_pm_qos_mtx);
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return ret;
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}
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EXPORT_SYMBOL_GPL(dev_pm_qos_remove_request);
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/**
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* dev_pm_qos_add_notifier - sets notification entry for changes to target value
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* of per-device PM QoS constraints
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*
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* @dev: target device for the constraint
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* @notifier: notifier block managed by caller.
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*
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* Will register the notifier into a notification chain that gets called
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* upon changes to the target value for the device.
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*/
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int dev_pm_qos_add_notifier(struct device *dev, struct notifier_block *notifier)
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{
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int retval = 0;
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mutex_lock(&dev_pm_qos_mtx);
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/* Silently return if the constraints object is not present. */
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if (dev->power.constraints)
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retval = blocking_notifier_chain_register(
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dev->power.constraints->notifiers,
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notifier);
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mutex_unlock(&dev_pm_qos_mtx);
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return retval;
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}
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EXPORT_SYMBOL_GPL(dev_pm_qos_add_notifier);
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/**
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* dev_pm_qos_remove_notifier - deletes notification for changes to target value
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* of per-device PM QoS constraints
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*
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* @dev: target device for the constraint
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* @notifier: notifier block to be removed.
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*
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* Will remove the notifier from the notification chain that gets called
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* upon changes to the target value.
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*/
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int dev_pm_qos_remove_notifier(struct device *dev,
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struct notifier_block *notifier)
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{
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int retval = 0;
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mutex_lock(&dev_pm_qos_mtx);
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/* Silently return if the constraints object is not present. */
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if (dev->power.constraints)
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retval = blocking_notifier_chain_unregister(
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dev->power.constraints->notifiers,
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notifier);
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mutex_unlock(&dev_pm_qos_mtx);
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return retval;
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}
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EXPORT_SYMBOL_GPL(dev_pm_qos_remove_notifier);
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/**
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* dev_pm_qos_add_global_notifier - sets notification entry for changes to
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* target value of the PM QoS constraints for any device
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*
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* @notifier: notifier block managed by caller.
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*
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* Will register the notifier into a notification chain that gets called
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* upon changes to the target value for any device.
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*/
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int dev_pm_qos_add_global_notifier(struct notifier_block *notifier)
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{
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return blocking_notifier_chain_register(&dev_pm_notifiers, notifier);
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}
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EXPORT_SYMBOL_GPL(dev_pm_qos_add_global_notifier);
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/**
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* dev_pm_qos_remove_global_notifier - deletes notification for changes to
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* target value of PM QoS constraints for any device
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*
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* @notifier: notifier block to be removed.
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*
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* Will remove the notifier from the notification chain that gets called
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* upon changes to the target value for any device.
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*/
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int dev_pm_qos_remove_global_notifier(struct notifier_block *notifier)
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{
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return blocking_notifier_chain_unregister(&dev_pm_notifiers, notifier);
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}
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EXPORT_SYMBOL_GPL(dev_pm_qos_remove_global_notifier);
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