qos.c

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/*
 * 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>

#include "power.h"

static DEFINE_MUTEX(dev_pm_qos_mtx);

static BLOCKING_NOTIFIER_HEAD(dev_pm_notifiers);

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;
}

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;
}

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);
}

void dev_pm_qos_constraints_destroy(struct device *dev)
{
    struct dev_pm_qos_request *req, *tmp;
    struct pm_qos_constraints *c;

    /*
     * If the device's PM QoS resume latency limit has been exposed to user
     * space, it has to be hidden at this point.
     */
    dev_pm_qos_hide_latency_limit(dev);

    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);
}

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\n", __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);

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\n", __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);

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\n", __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);

int dev_pm_qos_add_notifier(struct device *dev, struct notifier_block *notifier)
{
    int ret = 0;

    mutex_lock(&dev_pm_qos_mtx);

    if (!dev->power.constraints)
        ret = dev->power.power_state.event != PM_EVENT_INVALID ?
            dev_pm_qos_constraints_allocate(dev) : -ENODEV;

    if (!ret)
        ret = blocking_notifier_chain_register(
                dev->power.constraints->notifiers, notifier);

    mutex_unlock(&dev_pm_qos_mtx);
    return ret;
}
EXPORT_SYMBOL_GPL(dev_pm_qos_add_notifier);

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);

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);

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);

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 < 0)
        req->dev = NULL;

    return error;
}
EXPORT_SYMBOL_GPL(dev_pm_qos_add_ancestor_request);

#ifdef CONFIG_PM_RUNTIME
static void __dev_pm_qos_drop_user_request(struct device *dev)
{
    dev_pm_qos_remove_request(dev->power.pq_req);
    dev->power.pq_req = NULL;
}

int dev_pm_qos_expose_latency_limit(struct device *dev, s32 value)
{
    struct dev_pm_qos_request *req;
    int ret;

    if (!device_is_registered(dev) || value < 0)
        return -EINVAL;

    if (dev->power.pq_req)
        return -EEXIST;

    req = kzalloc(sizeof(*req), GFP_KERNEL);
    if (!req)
        return -ENOMEM;

    ret = dev_pm_qos_add_request(dev, req, value);
    if (ret < 0)
        return ret;

    dev->power.pq_req = req;
    ret = pm_qos_sysfs_add(dev);
    if (ret)
        __dev_pm_qos_drop_user_request(dev);

    return ret;
}
EXPORT_SYMBOL_GPL(dev_pm_qos_expose_latency_limit);

void dev_pm_qos_hide_latency_limit(struct device *dev)
{
    if (dev->power.pq_req) {
        pm_qos_sysfs_remove(dev);
        __dev_pm_qos_drop_user_request(dev);
    }
}
EXPORT_SYMBOL_GPL(dev_pm_qos_hide_latency_limit);
#endif /* CONFIG_PM_RUNTIME */