Linux 4.19-rc7

[linux-2.6/btrfs-unstable.git] / drivers / base / power / runtime.c

/*
 * drivers/base/power/runtime.c - Helper functions for device runtime PM
 *
 * Copyright (c) 2009 Rafael J. Wysocki <rjw@sisk.pl>, Novell Inc.
 * Copyright (C) 2010 Alan Stern <stern@rowland.harvard.edu>
 *
 * This file is released under the GPLv2.
 */

#include <linux/sched/mm.h>
#include <linux/export.h>
#include <linux/pm_runtime.h>
#include <linux/pm_wakeirq.h>
#include <trace/events/rpm.h>

#include "../base.h"
#include "power.h"

typedef int (*pm_callback_t)(struct device *);

static pm_callback_t __rpm_get_callback(struct device *dev, size_t cb_offset)
{
        pm_callback_t cb;
        const struct dev_pm_ops *ops;

        if (dev->pm_domain)
                ops = &dev->pm_domain->ops;
        else if (dev->type && dev->type->pm)
                ops = dev->type->pm;
        else if (dev->class && dev->class->pm)
                ops = dev->class->pm;
        else if (dev->bus && dev->bus->pm)
                ops = dev->bus->pm;
        else
                ops = NULL;

        if (ops)
                cb = *(pm_callback_t *)((void *)ops + cb_offset);
        else
                cb = NULL;

        if (!cb && dev->driver && dev->driver->pm)
                cb = *(pm_callback_t *)((void *)dev->driver->pm + cb_offset);

        return cb;
}

#define RPM_GET_CALLBACK(dev, callback) \
                __rpm_get_callback(dev, offsetof(struct dev_pm_ops, callback))

static int rpm_resume(struct device *dev, int rpmflags);
static int rpm_suspend(struct device *dev, int rpmflags);

/**
 * update_pm_runtime_accounting - Update the time accounting of power states
 * @dev: Device to update the accounting for
 *
 * In order to be able to have time accounting of the various power states
 * (as used by programs such as PowerTOP to show the effectiveness of runtime
 * PM), we need to track the time spent in each state.
 * update_pm_runtime_accounting must be called each time before the
 * runtime_status field is updated, to account the time in the old state
 * correctly.
 */
void update_pm_runtime_accounting(struct device *dev)
{
        unsigned long now = jiffies;
        unsigned long delta;

        delta = now - dev->power.accounting_timestamp;

        dev->power.accounting_timestamp = now;

        if (dev->power.disable_depth > 0)
                return;

        if (dev->power.runtime_status == RPM_SUSPENDED)
                dev->power.suspended_jiffies += delta;
        else
                dev->power.active_jiffies += delta;
}

static void __update_runtime_status(struct device *dev, enum rpm_status status)
{
        update_pm_runtime_accounting(dev);
        dev->power.runtime_status = status;
}

/**
 * pm_runtime_deactivate_timer - Deactivate given device's suspend timer.
 * @dev: Device to handle.
 */
static void pm_runtime_deactivate_timer(struct device *dev)
{
        if (dev->power.timer_expires > 0) {
                del_timer(&dev->power.suspend_timer);
                dev->power.timer_expires = 0;
        }
}

/**
 * pm_runtime_cancel_pending - Deactivate suspend timer and cancel requests.
 * @dev: Device to handle.
 */
static void pm_runtime_cancel_pending(struct device *dev)
{
        pm_runtime_deactivate_timer(dev);
        /*
         * In case there's a request pending, make sure its work function will
         * return without doing anything.
         */
        dev->power.request = RPM_REQ_NONE;
}

/*
 * pm_runtime_autosuspend_expiration - Get a device's autosuspend-delay expiration time.
 * @dev: Device to handle.
 *
 * Compute the autosuspend-delay expiration time based on the device's
 * power.last_busy time.  If the delay has already expired or is disabled
 * (negative) or the power.use_autosuspend flag isn't set, return 0.
 * Otherwise return the expiration time in jiffies (adjusted to be nonzero).
 *
 * This function may be called either with or without dev->power.lock held.
 * Either way it can be racy, since power.last_busy may be updated at any time.
 */
unsigned long pm_runtime_autosuspend_expiration(struct device *dev)
{
        int autosuspend_delay;
        long elapsed;
        unsigned long last_busy;
        unsigned long expires = 0;

        if (!dev->power.use_autosuspend)
                goto out;

        autosuspend_delay = READ_ONCE(dev->power.autosuspend_delay);
        if (autosuspend_delay < 0)
                goto out;

        last_busy = READ_ONCE(dev->power.last_busy);
        elapsed = jiffies - last_busy;
        if (elapsed < 0)
                goto out;       /* jiffies has wrapped around. */

        /*
         * If the autosuspend_delay is >= 1 second, align the timer by rounding
         * up to the nearest second.
         */
        expires = last_busy + msecs_to_jiffies(autosuspend_delay);
        if (autosuspend_delay >= 1000)
                expires = round_jiffies(expires);
        expires += !expires;
        if (elapsed >= expires - last_busy)
                expires = 0;    /* Already expired. */

 out:
        return expires;
}
EXPORT_SYMBOL_GPL(pm_runtime_autosuspend_expiration);

static int dev_memalloc_noio(struct device *dev, void *data)
{
        return dev->power.memalloc_noio;
}

/*
 * pm_runtime_set_memalloc_noio - Set a device's memalloc_noio flag.
 * @dev: Device to handle.
 * @enable: True for setting the flag and False for clearing the flag.
 *
 * Set the flag for all devices in the path from the device to the
 * root device in the device tree if @enable is true, otherwise clear
 * the flag for devices in the path whose siblings don't set the flag.
 *
 * The function should only be called by block device, or network
 * device driver for solving the deadlock problem during runtime
 * resume/suspend:
 *
 *     If memory allocation with GFP_KERNEL is called inside runtime
 *     resume/suspend callback of any one of its ancestors(or the
 *     block device itself), the deadlock may be triggered inside the
 *     memory allocation since it might not complete until the block
 *     device becomes active and the involed page I/O finishes. The
 *     situation is pointed out first by Alan Stern. Network device
 *     are involved in iSCSI kind of situation.
 *
 * The lock of dev_hotplug_mutex is held in the function for handling
 * hotplug race because pm_runtime_set_memalloc_noio() may be called
 * in async probe().
 *
 * The function should be called between device_add() and device_del()
 * on the affected device(block/network device).
 */
void pm_runtime_set_memalloc_noio(struct device *dev, bool enable)
{
        static DEFINE_MUTEX(dev_hotplug_mutex);

        mutex_lock(&dev_hotplug_mutex);
        for (;;) {
                bool enabled;

                /* hold power lock since bitfield is not SMP-safe. */
                spin_lock_irq(&dev->power.lock);
                enabled = dev->power.memalloc_noio;
                dev->power.memalloc_noio = enable;
                spin_unlock_irq(&dev->power.lock);

                /*
                 * not need to enable ancestors any more if the device
                 * has been enabled.
                 */
                if (enabled && enable)
                        break;

                dev = dev->parent;

                /*
                 * clear flag of the parent device only if all the
                 * children don't set the flag because ancestor's
                 * flag was set by any one of the descendants.
                 */
                if (!dev || (!enable &&
                             device_for_each_child(dev, NULL,
                                                   dev_memalloc_noio)))
                        break;
        }
        mutex_unlock(&dev_hotplug_mutex);
}
EXPORT_SYMBOL_GPL(pm_runtime_set_memalloc_noio);

/**
 * rpm_check_suspend_allowed - Test whether a device may be suspended.
 * @dev: Device to test.
 */
static int rpm_check_suspend_allowed(struct device *dev)
{
        int retval = 0;

        if (dev->power.runtime_error)
                retval = -EINVAL;
        else if (dev->power.disable_depth > 0)
                retval = -EACCES;
        else if (atomic_read(&dev->power.usage_count) > 0)
                retval = -EAGAIN;
        else if (!dev->power.ignore_children &&
                        atomic_read(&dev->power.child_count))
                retval = -EBUSY;

        /* Pending resume requests take precedence over suspends. */
        else if ((dev->power.deferred_resume
                        && dev->power.runtime_status == RPM_SUSPENDING)
            || (dev->power.request_pending
                        && dev->power.request == RPM_REQ_RESUME))
                retval = -EAGAIN;
        else if (__dev_pm_qos_read_value(dev) == 0)
                retval = -EPERM;
        else if (dev->power.runtime_status == RPM_SUSPENDED)
                retval = 1;

        return retval;
}

static int rpm_get_suppliers(struct device *dev)
{
        struct device_link *link;

        list_for_each_entry_rcu(link, &dev->links.suppliers, c_node) {
                int retval;

                if (!(link->flags & DL_FLAG_PM_RUNTIME))
                        continue;

                if (READ_ONCE(link->status) == DL_STATE_SUPPLIER_UNBIND ||
                    link->rpm_active)
                        continue;

                retval = pm_runtime_get_sync(link->supplier);
                /* Ignore suppliers with disabled runtime PM. */
                if (retval < 0 && retval != -EACCES) {
                        pm_runtime_put_noidle(link->supplier);
                        return retval;
                }
                link->rpm_active = true;
        }
        return 0;
}

static void rpm_put_suppliers(struct device *dev)
{
        struct device_link *link;

        list_for_each_entry_rcu(link, &dev->links.suppliers, c_node)
                if (link->rpm_active &&
                    READ_ONCE(link->status) != DL_STATE_SUPPLIER_UNBIND) {
                        pm_runtime_put(link->supplier);
                        link->rpm_active = false;
                }
}

/**
 * __rpm_callback - Run a given runtime PM callback for a given device.
 * @cb: Runtime PM callback to run.
 * @dev: Device to run the callback for.
 */
static int __rpm_callback(int (*cb)(struct device *), struct device *dev)
        __releases(&dev->power.lock) __acquires(&dev->power.lock)
{
        int retval, idx;
        bool use_links = dev->power.links_count > 0;

        if (dev->power.irq_safe) {
                spin_unlock(&dev->power.lock);
        } else {
                spin_unlock_irq(&dev->power.lock);

                /*
                 * Resume suppliers if necessary.
                 *
                 * The device's runtime PM status cannot change until this
                 * routine returns, so it is safe to read the status outside of
                 * the lock.
                 */
                if (use_links && dev->power.runtime_status == RPM_RESUMING) {
                        idx = device_links_read_lock();

                        retval = rpm_get_suppliers(dev);
                        if (retval)
                                goto fail;

                        device_links_read_unlock(idx);
                }
        }

        retval = cb(dev);

        if (dev->power.irq_safe) {
                spin_lock(&dev->power.lock);
        } else {
                /*
                 * If the device is suspending and the callback has returned
                 * success, drop the usage counters of the suppliers that have
                 * been reference counted on its resume.
                 *
                 * Do that if resume fails too.
                 */
                if (use_links
                    && ((dev->power.runtime_status == RPM_SUSPENDING && !retval)
                    || (dev->power.runtime_status == RPM_RESUMING && retval))) {
                        idx = device_links_read_lock();

 fail:
                        rpm_put_suppliers(dev);

                        device_links_read_unlock(idx);
                }

                spin_lock_irq(&dev->power.lock);
        }

        return retval;
}

/**
 * rpm_idle - Notify device bus type if the device can be suspended.
 * @dev: Device to notify the bus type about.
 * @rpmflags: Flag bits.
 *
 * Check if the device's runtime PM status allows it to be suspended.  If
 * another idle notification has been started earlier, return immediately.  If
 * the RPM_ASYNC flag is set then queue an idle-notification request; otherwise
 * run the ->runtime_idle() callback directly. If the ->runtime_idle callback
 * doesn't exist or if it returns 0, call rpm_suspend with the RPM_AUTO flag.
 *
 * This function must be called under dev->power.lock with interrupts disabled.
 */
static int rpm_idle(struct device *dev, int rpmflags)
{
        int (*callback)(struct device *);
        int retval;

        trace_rpm_idle_rcuidle(dev, rpmflags);
        retval = rpm_check_suspend_allowed(dev);
        if (retval < 0)
                ;       /* Conditions are wrong. */

        /* Idle notifications are allowed only in the RPM_ACTIVE state. */
        else if (dev->power.runtime_status != RPM_ACTIVE)
                retval = -EAGAIN;

        /*
         * Any pending request other than an idle notification takes
         * precedence over us, except that the timer may be running.
         */
        else if (dev->power.request_pending &&
            dev->power.request > RPM_REQ_IDLE)
                retval = -EAGAIN;

        /* Act as though RPM_NOWAIT is always set. */
        else if (dev->power.idle_notification)
                retval = -EINPROGRESS;
        if (retval)
                goto out;

        /* Pending requests need to be canceled. */
        dev->power.request = RPM_REQ_NONE;

        if (dev->power.no_callbacks)
                goto out;

        /* Carry out an asynchronous or a synchronous idle notification. */
        if (rpmflags & RPM_ASYNC) {
                dev->power.request = RPM_REQ_IDLE;
                if (!dev->power.request_pending) {
                        dev->power.request_pending = true;
                        queue_work(pm_wq, &dev->power.work);
                }
                trace_rpm_return_int_rcuidle(dev, _THIS_IP_, 0);
                return 0;
        }

        dev->power.idle_notification = true;

        callback = RPM_GET_CALLBACK(dev, runtime_idle);

        if (callback)
                retval = __rpm_callback(callback, dev);

        dev->power.idle_notification = false;
        wake_up_all(&dev->power.wait_queue);

 out:
        trace_rpm_return_int_rcuidle(dev, _THIS_IP_, retval);
        return retval ? retval : rpm_suspend(dev, rpmflags | RPM_AUTO);
}

/**
 * rpm_callback - Run a given runtime PM callback for a given device.
 * @cb: Runtime PM callback to run.
 * @dev: Device to run the callback for.
 */
static int rpm_callback(int (*cb)(struct device *), struct device *dev)
{
        int retval;

        if (!cb)
                return -ENOSYS;

        if (dev->power.memalloc_noio) {
                unsigned int noio_flag;

                /*
                 * Deadlock might be caused if memory allocation with
                 * GFP_KERNEL happens inside runtime_suspend and
                 * runtime_resume callbacks of one block device's
                 * ancestor or the block device itself. Network
                 * device might be thought as part of iSCSI block
                 * device, so network device and its ancestor should
                 * be marked as memalloc_noio too.
                 */
                noio_flag = memalloc_noio_save();
                retval = __rpm_callback(cb, dev);
                memalloc_noio_restore(noio_flag);
        } else {
                retval = __rpm_callback(cb, dev);
        }

        dev->power.runtime_error = retval;
        return retval != -EACCES ? retval : -EIO;
}

/**
 * rpm_suspend - Carry out runtime suspend of given device.
 * @dev: Device to suspend.
 * @rpmflags: Flag bits.
 *
 * Check if the device's runtime PM status allows it to be suspended.
 * Cancel a pending idle notification, autosuspend or suspend. If
 * another suspend has been started earlier, either return immediately
 * or wait for it to finish, depending on the RPM_NOWAIT and RPM_ASYNC
 * flags. If the RPM_ASYNC flag is set then queue a suspend request;
 * otherwise run the ->runtime_suspend() callback directly. When
 * ->runtime_suspend succeeded, if a deferred resume was requested while
 * the callback was running then carry it out, otherwise send an idle
 * notification for its parent (if the suspend succeeded and both
 * ignore_children of parent->power and irq_safe of dev->power are not set).
 * If ->runtime_suspend failed with -EAGAIN or -EBUSY, and if the RPM_AUTO
 * flag is set and the next autosuspend-delay expiration time is in the
 * future, schedule another autosuspend attempt.
 *
 * This function must be called under dev->power.lock with interrupts disabled.
 */
static int rpm_suspend(struct device *dev, int rpmflags)
        __releases(&dev->power.lock) __acquires(&dev->power.lock)
{
        int (*callback)(struct device *);
        struct device *parent = NULL;
        int retval;

        trace_rpm_suspend_rcuidle(dev, rpmflags);

 repeat:
        retval = rpm_check_suspend_allowed(dev);

        if (retval < 0)
                ;       /* Conditions are wrong. */

        /* Synchronous suspends are not allowed in the RPM_RESUMING state. */
        else if (dev->power.runtime_status == RPM_RESUMING &&
            !(rpmflags & RPM_ASYNC))
                retval = -EAGAIN;
        if (retval)
                goto out;

        /* If the autosuspend_delay time hasn't expired yet, reschedule. */
        if ((rpmflags & RPM_AUTO)
            && dev->power.runtime_status != RPM_SUSPENDING) {
                unsigned long expires = pm_runtime_autosuspend_expiration(dev);

                if (expires != 0) {
                        /* Pending requests need to be canceled. */
                        dev->power.request = RPM_REQ_NONE;

                        /*
                         * Optimization: If the timer is already running and is
                         * set to expire at or before the autosuspend delay,
                         * avoid the overhead of resetting it.  Just let it
                         * expire; pm_suspend_timer_fn() will take care of the
                         * rest.
                         */
                        if (!(dev->power.timer_expires && time_before_eq(
                            dev->power.timer_expires, expires))) {
                                dev->power.timer_expires = expires;
                                mod_timer(&dev->power.suspend_timer, expires);
                        }
                        dev->power.timer_autosuspends = 1;
                        goto out;
                }
        }

        /* Other scheduled or pending requests need to be canceled. */
        pm_runtime_cancel_pending(dev);

        if (dev->power.runtime_status == RPM_SUSPENDING) {
                DEFINE_WAIT(wait);

                if (rpmflags & (RPM_ASYNC | RPM_NOWAIT)) {
                        retval = -EINPROGRESS;
                        goto out;
                }

                if (dev->power.irq_safe) {
                        spin_unlock(&dev->power.lock);

                        cpu_relax();

                        spin_lock(&dev->power.lock);
                        goto repeat;
                }

                /* Wait for the other suspend running in parallel with us. */
                for (;;) {
                        prepare_to_wait(&dev->power.wait_queue, &wait,
                                        TASK_UNINTERRUPTIBLE);
                        if (dev->power.runtime_status != RPM_SUSPENDING)
                                break;

                        spin_unlock_irq(&dev->power.lock);

                        schedule();

                        spin_lock_irq(&dev->power.lock);
                }
                finish_wait(&dev->power.wait_queue, &wait);
                goto repeat;
        }

        if (dev->power.no_callbacks)
                goto no_callback;       /* Assume success. */

        /* Carry out an asynchronous or a synchronous suspend. */
        if (rpmflags & RPM_ASYNC) {
                dev->power.request = (rpmflags & RPM_AUTO) ?
                    RPM_REQ_AUTOSUSPEND : RPM_REQ_SUSPEND;
                if (!dev->power.request_pending) {
                        dev->power.request_pending = true;
                        queue_work(pm_wq, &dev->power.work);
                }
                goto out;
        }

        __update_runtime_status(dev, RPM_SUSPENDING);

        callback = RPM_GET_CALLBACK(dev, runtime_suspend);

        dev_pm_enable_wake_irq_check(dev, true);
        retval = rpm_callback(callback, dev);
        if (retval)
                goto fail;

 no_callback:
        __update_runtime_status(dev, RPM_SUSPENDED);
        pm_runtime_deactivate_timer(dev);

        if (dev->parent) {
                parent = dev->parent;
                atomic_add_unless(&parent->power.child_count, -1, 0);
        }
        wake_up_all(&dev->power.wait_queue);

        if (dev->power.deferred_resume) {
                dev->power.deferred_resume = false;
                rpm_resume(dev, 0);
                retval = -EAGAIN;
                goto out;
        }

        /* Maybe the parent is now able to suspend. */
        if (parent && !parent->power.ignore_children && !dev->power.irq_safe) {
                spin_unlock(&dev->power.lock);

                spin_lock(&parent->power.lock);
                rpm_idle(parent, RPM_ASYNC);
                spin_unlock(&parent->power.lock);

                spin_lock(&dev->power.lock);
        }

 out:
        trace_rpm_return_int_rcuidle(dev, _THIS_IP_, retval);

        return retval;

 fail:
        dev_pm_disable_wake_irq_check(dev);
        __update_runtime_status(dev, RPM_ACTIVE);
        dev->power.deferred_resume = false;
        wake_up_all(&dev->power.wait_queue);

        if (retval == -EAGAIN || retval == -EBUSY) {
                dev->power.runtime_error = 0;

                /*
                 * If the callback routine failed an autosuspend, and
                 * if the last_busy time has been updated so that there
                 * is a new autosuspend expiration time, automatically
                 * reschedule another autosuspend.
                 */
                if ((rpmflags & RPM_AUTO) &&
                    pm_runtime_autosuspend_expiration(dev) != 0)
                        goto repeat;
        } else {
                pm_runtime_cancel_pending(dev);
        }
        goto out;
}

/**
 * rpm_resume - Carry out runtime resume of given device.
 * @dev: Device to resume.
 * @rpmflags: Flag bits.
 *
 * Check if the device's runtime PM status allows it to be resumed.  Cancel
 * any scheduled or pending requests.  If another resume has been started
 * earlier, either return immediately or wait for it to finish, depending on the
 * RPM_NOWAIT and RPM_ASYNC flags.  Similarly, if there's a suspend running in
 * parallel with this function, either tell the other process to resume after
 * suspending (deferred_resume) or wait for it to finish.  If the RPM_ASYNC
 * flag is set then queue a resume request; otherwise run the
 * ->runtime_resume() callback directly.  Queue an idle notification for the
 * device if the resume succeeded.
 *
 * This function must be called under dev->power.lock with interrupts disabled.
 */
static int rpm_resume(struct device *dev, int rpmflags)
        __releases(&dev->power.lock) __acquires(&dev->power.lock)
{
        int (*callback)(struct device *);
        struct device *parent = NULL;
        int retval = 0;

        trace_rpm_resume_rcuidle(dev, rpmflags);

 repeat:
        if (dev->power.runtime_error)
                retval = -EINVAL;
        else if (dev->power.disable_depth == 1 && dev->power.is_suspended
            && dev->power.runtime_status == RPM_ACTIVE)
                retval = 1;
        else if (dev->power.disable_depth > 0)
                retval = -EACCES;
        if (retval)
                goto out;

        /*
         * Other scheduled or pending requests need to be canceled.  Small
         * optimization: If an autosuspend timer is running, leave it running
         * rather than cancelling it now only to restart it again in the near
         * future.
         */
        dev->power.request = RPM_REQ_NONE;
        if (!dev->power.timer_autosuspends)
                pm_runtime_deactivate_timer(dev);

        if (dev->power.runtime_status == RPM_ACTIVE) {
                retval = 1;
                goto out;
        }

        if (dev->power.runtime_status == RPM_RESUMING
            || dev->power.runtime_status == RPM_SUSPENDING) {
                DEFINE_WAIT(wait);

                if (rpmflags & (RPM_ASYNC | RPM_NOWAIT)) {
                        if (dev->power.runtime_status == RPM_SUSPENDING)
                                dev->power.deferred_resume = true;
                        else
                                retval = -EINPROGRESS;
                        goto out;
                }

                if (dev->power.irq_safe) {
                        spin_unlock(&dev->power.lock);

                        cpu_relax();

                        spin_lock(&dev->power.lock);
                        goto repeat;
                }

                /* Wait for the operation carried out in parallel with us. */
                for (;;) {
                        prepare_to_wait(&dev->power.wait_queue, &wait,
                                        TASK_UNINTERRUPTIBLE);
                        if (dev->power.runtime_status != RPM_RESUMING
                            && dev->power.runtime_status != RPM_SUSPENDING)
                                break;

                        spin_unlock_irq(&dev->power.lock);

                        schedule();

                        spin_lock_irq(&dev->power.lock);
                }
                finish_wait(&dev->power.wait_queue, &wait);
                goto repeat;
        }

        /*
         * See if we can skip waking up the parent.  This is safe only if
         * power.no_callbacks is set, because otherwise we don't know whether
         * the resume will actually succeed.
         */
        if (dev->power.no_callbacks && !parent && dev->parent) {
                spin_lock_nested(&dev->parent->power.lock, SINGLE_DEPTH_NESTING);
                if (dev->parent->power.disable_depth > 0
                    || dev->parent->power.ignore_children
                    || dev->parent->power.runtime_status == RPM_ACTIVE) {
                        atomic_inc(&dev->parent->power.child_count);
                        spin_unlock(&dev->parent->power.lock);
                        retval = 1;
                        goto no_callback;       /* Assume success. */
                }
                spin_unlock(&dev->parent->power.lock);
        }

        /* Carry out an asynchronous or a synchronous resume. */
        if (rpmflags & RPM_ASYNC) {
                dev->power.request = RPM_REQ_RESUME;
                if (!dev->power.request_pending) {
                        dev->power.request_pending = true;
                        queue_work(pm_wq, &dev->power.work);
                }
                retval = 0;
                goto out;
        }

        if (!parent && dev->parent) {
                /*
                 * Increment the parent's usage counter and resume it if
                 * necessary.  Not needed if dev is irq-safe; then the
                 * parent is permanently resumed.
                 */
                parent = dev->parent;
                if (dev->power.irq_safe)
                        goto skip_parent;
                spin_unlock(&dev->power.lock);

                pm_runtime_get_noresume(parent);

                spin_lock(&parent->power.lock);
                /*
                 * Resume the parent if it has runtime PM enabled and not been
                 * set to ignore its children.
                 */
                if (!parent->power.disable_depth
                    && !parent->power.ignore_children) {
                        rpm_resume(parent, 0);
                        if (parent->power.runtime_status != RPM_ACTIVE)
                                retval = -EBUSY;
                }
                spin_unlock(&parent->power.lock);

                spin_lock(&dev->power.lock);
                if (retval)
                        goto out;
                goto repeat;
        }
 skip_parent:

        if (dev->power.no_callbacks)
                goto no_callback;       /* Assume success. */

        __update_runtime_status(dev, RPM_RESUMING);

        callback = RPM_GET_CALLBACK(dev, runtime_resume);

        dev_pm_disable_wake_irq_check(dev);
        retval = rpm_callback(callback, dev);
        if (retval) {
                __update_runtime_status(dev, RPM_SUSPENDED);
                pm_runtime_cancel_pending(dev);
                dev_pm_enable_wake_irq_check(dev, false);
        } else {
 no_callback:
                __update_runtime_status(dev, RPM_ACTIVE);
                pm_runtime_mark_last_busy(dev);
                if (parent)
                        atomic_inc(&parent->power.child_count);
        }
        wake_up_all(&dev->power.wait_queue);

        if (retval >= 0)
                rpm_idle(dev, RPM_ASYNC);

 out:
        if (parent && !dev->power.irq_safe) {
                spin_unlock_irq(&dev->power.lock);

                pm_runtime_put(parent);

                spin_lock_irq(&dev->power.lock);
        }

        trace_rpm_return_int_rcuidle(dev, _THIS_IP_, retval);

        return retval;
}

/**
 * pm_runtime_work - Universal runtime PM work function.
 * @work: Work structure used for scheduling the execution of this function.
 *
 * Use @work to get the device object the work is to be done for, determine what
 * is to be done and execute the appropriate runtime PM function.
 */
static void pm_runtime_work(struct work_struct *work)
{
        struct device *dev = container_of(work, struct device, power.work);
        enum rpm_request req;

        spin_lock_irq(&dev->power.lock);

        if (!dev->power.request_pending)
                goto out;

        req = dev->power.request;
        dev->power.request = RPM_REQ_NONE;
        dev->power.request_pending = false;

        switch (req) {
        case RPM_REQ_NONE:
                break;
        case RPM_REQ_IDLE:
                rpm_idle(dev, RPM_NOWAIT);
                break;
        case RPM_REQ_SUSPEND:
                rpm_suspend(dev, RPM_NOWAIT);
                break;
        case RPM_REQ_AUTOSUSPEND:
                rpm_suspend(dev, RPM_NOWAIT | RPM_AUTO);
                break;
        case RPM_REQ_RESUME:
                rpm_resume(dev, RPM_NOWAIT);
                break;
        }

 out:
        spin_unlock_irq(&dev->power.lock);
}

/**
 * pm_suspend_timer_fn - Timer function for pm_schedule_suspend().
 * @data: Device pointer passed by pm_schedule_suspend().
 *
 * Check if the time is right and queue a suspend request.
 */
static void pm_suspend_timer_fn(struct timer_list *t)
{
        struct device *dev = from_timer(dev, t, power.suspend_timer);
        unsigned long flags;
        unsigned long expires;

        spin_lock_irqsave(&dev->power.lock, flags);

        expires = dev->power.timer_expires;
        /* If 'expire' is after 'jiffies' we've been called too early. */
        if (expires > 0 && !time_after(expires, jiffies)) {
                dev->power.timer_expires = 0;
                rpm_suspend(dev, dev->power.timer_autosuspends ?
                    (RPM_ASYNC | RPM_AUTO) : RPM_ASYNC);
        }

        spin_unlock_irqrestore(&dev->power.lock, flags);
}

/**
 * pm_schedule_suspend - Set up a timer to submit a suspend request in future.
 * @dev: Device to suspend.
 * @delay: Time to wait before submitting a suspend request, in milliseconds.
 */
int pm_schedule_suspend(struct device *dev, unsigned int delay)
{
        unsigned long flags;
        int retval;

        spin_lock_irqsave(&dev->power.lock, flags);

        if (!delay) {
                retval = rpm_suspend(dev, RPM_ASYNC);
                goto out;
        }

        retval = rpm_check_suspend_allowed(dev);
        if (retval)
                goto out;

        /* Other scheduled or pending requests need to be canceled. */
        pm_runtime_cancel_pending(dev);

        dev->power.timer_expires = jiffies + msecs_to_jiffies(delay);
        dev->power.timer_expires += !dev->power.timer_expires;
        dev->power.timer_autosuspends = 0;
        mod_timer(&dev->power.suspend_timer, dev->power.timer_expires);

 out:
        spin_unlock_irqrestore(&dev->power.lock, flags);

        return retval;
}
EXPORT_SYMBOL_GPL(pm_schedule_suspend);

/**
 * __pm_runtime_idle - Entry point for runtime idle operations.
 * @dev: Device to send idle notification for.
 * @rpmflags: Flag bits.
 *
 * If the RPM_GET_PUT flag is set, decrement the device's usage count and
 * return immediately if it is larger than zero.  Then carry out an idle
 * notification, either synchronous or asynchronous.
 *
 * This routine may be called in atomic context if the RPM_ASYNC flag is set,
 * or if pm_runtime_irq_safe() has been called.
 */
int __pm_runtime_idle(struct device *dev, int rpmflags)
{
        unsigned long flags;
        int retval;

        if (rpmflags & RPM_GET_PUT) {
                if (!atomic_dec_and_test(&dev->power.usage_count))
                        return 0;
        }

        might_sleep_if(!(rpmflags & RPM_ASYNC) && !dev->power.irq_safe);

        spin_lock_irqsave(&dev->power.lock, flags);
        retval = rpm_idle(dev, rpmflags);
        spin_unlock_irqrestore(&dev->power.lock, flags);

        return retval;
}
EXPORT_SYMBOL_GPL(__pm_runtime_idle);

/**
 * __pm_runtime_suspend - Entry point for runtime put/suspend operations.
 * @dev: Device to suspend.
 * @rpmflags: Flag bits.
 *
 * If the RPM_GET_PUT flag is set, decrement the device's usage count and
 * return immediately if it is larger than zero.  Then carry out a suspend,
 * either synchronous or asynchronous.
 *
 * This routine may be called in atomic context if the RPM_ASYNC flag is set,
 * or if pm_runtime_irq_safe() has been called.
 */
int __pm_runtime_suspend(struct device *dev, int rpmflags)
{
        unsigned long flags;
        int retval;

        if (rpmflags & RPM_GET_PUT) {
                if (!atomic_dec_and_test(&dev->power.usage_count))
                        return 0;
        }

        might_sleep_if(!(rpmflags & RPM_ASYNC) && !dev->power.irq_safe);

        spin_lock_irqsave(&dev->power.lock, flags);
        retval = rpm_suspend(dev, rpmflags);
        spin_unlock_irqrestore(&dev->power.lock, flags);

        return retval;
}
EXPORT_SYMBOL_GPL(__pm_runtime_suspend);

/**
 * __pm_runtime_resume - Entry point for runtime resume operations.
 * @dev: Device to resume.
 * @rpmflags: Flag bits.
 *
 * If the RPM_GET_PUT flag is set, increment the device's usage count.  Then
 * carry out a resume, either synchronous or asynchronous.
 *
 * This routine may be called in atomic context if the RPM_ASYNC flag is set,
 * or if pm_runtime_irq_safe() has been called.
 */
int __pm_runtime_resume(struct device *dev, int rpmflags)
{
        unsigned long flags;
        int retval;

        might_sleep_if(!(rpmflags & RPM_ASYNC) && !dev->power.irq_safe &&
                        dev->power.runtime_status != RPM_ACTIVE);

        if (rpmflags & RPM_GET_PUT)
                atomic_inc(&dev->power.usage_count);

        spin_lock_irqsave(&dev->power.lock, flags);
        retval = rpm_resume(dev, rpmflags);
        spin_unlock_irqrestore(&dev->power.lock, flags);

        return retval;
}
EXPORT_SYMBOL_GPL(__pm_runtime_resume);

/**
 * pm_runtime_get_if_in_use - Conditionally bump up the device's usage counter.
 * @dev: Device to handle.
 *
 * Return -EINVAL if runtime PM is disabled for the device.
 *
 * If that's not the case and if the device's runtime PM status is RPM_ACTIVE
 * and the runtime PM usage counter is nonzero, increment the counter and
 * return 1.  Otherwise return 0 without changing the counter.
 */
int pm_runtime_get_if_in_use(struct device *dev)
{
        unsigned long flags;
        int retval;

        spin_lock_irqsave(&dev->power.lock, flags);
        retval = dev->power.disable_depth > 0 ? -EINVAL :
                dev->power.runtime_status == RPM_ACTIVE
                        && atomic_inc_not_zero(&dev->power.usage_count);
        spin_unlock_irqrestore(&dev->power.lock, flags);
        return retval;
}
EXPORT_SYMBOL_GPL(pm_runtime_get_if_in_use);

/**
 * __pm_runtime_set_status - Set runtime PM status of a device.
 * @dev: Device to handle.
 * @status: New runtime PM status of the device.
 *
 * If runtime PM of the device is disabled or its power.runtime_error field is
 * different from zero, the status may be changed either to RPM_ACTIVE, or to
 * RPM_SUSPENDED, as long as that reflects the actual state of the device.
 * However, if the device has a parent and the parent is not active, and the
 * parent's power.ignore_children flag is unset, the device's status cannot be
 * set to RPM_ACTIVE, so -EBUSY is returned in that case.
 *
 * If successful, __pm_runtime_set_status() clears the power.runtime_error field
 * and the device parent's counter of unsuspended children is modified to
 * reflect the new status.  If the new status is RPM_SUSPENDED, an idle
 * notification request for the parent is submitted.
 */
int __pm_runtime_set_status(struct device *dev, unsigned int status)
{
        struct device *parent = dev->parent;
        unsigned long flags;
        bool notify_parent = false;
        int error = 0;

        if (status != RPM_ACTIVE && status != RPM_SUSPENDED)
                return -EINVAL;

        spin_lock_irqsave(&dev->power.lock, flags);

        if (!dev->power.runtime_error && !dev->power.disable_depth) {
                error = -EAGAIN;
                goto out;
        }

        if (dev->power.runtime_status == status || !parent)
                goto out_set;

        if (status == RPM_SUSPENDED) {
                atomic_add_unless(&parent->power.child_count, -1, 0);
                notify_parent = !parent->power.ignore_children;
        } else {
                spin_lock_nested(&parent->power.lock, SINGLE_DEPTH_NESTING);

                /*
                 * It is invalid to put an active child under a parent that is
                 * not active, has runtime PM enabled and the
                 * 'power.ignore_children' flag unset.
                 */
                if (!parent->power.disable_depth
                    && !parent->power.ignore_children
                    && parent->power.runtime_status != RPM_ACTIVE) {
                        dev_err(dev, "runtime PM trying to activate child device %s but parent (%s) is not active\n",
                                dev_name(dev),
                                dev_name(parent));
                        error = -EBUSY;
                } else if (dev->power.runtime_status == RPM_SUSPENDED) {
                        atomic_inc(&parent->power.child_count);
                }

                spin_unlock(&parent->power.lock);

                if (error)
                        goto out;
        }

 out_set:
        __update_runtime_status(dev, status);
        dev->power.runtime_error = 0;
 out:
        spin_unlock_irqrestore(&dev->power.lock, flags);

        if (notify_parent)
                pm_request_idle(parent);

        return error;
}
EXPORT_SYMBOL_GPL(__pm_runtime_set_status);

/**
 * __pm_runtime_barrier - Cancel pending requests and wait for completions.
 * @dev: Device to handle.
 *
 * Flush all pending requests for the device from pm_wq and wait for all
 * runtime PM operations involving the device in progress to complete.
 *
 * Should be called under dev->power.lock with interrupts disabled.
 */
static void __pm_runtime_barrier(struct device *dev)
{
        pm_runtime_deactivate_timer(dev);

        if (dev->power.request_pending) {
                dev->power.request = RPM_REQ_NONE;
                spin_unlock_irq(&dev->power.lock);

                cancel_work_sync(&dev->power.work);

                spin_lock_irq(&dev->power.lock);
                dev->power.request_pending = false;
        }

        if (dev->power.runtime_status == RPM_SUSPENDING
            || dev->power.runtime_status == RPM_RESUMING
            || dev->power.idle_notification) {
                DEFINE_WAIT(wait);

                /* Suspend, wake-up or idle notification in progress. */
                for (;;) {
                        prepare_to_wait(&dev->power.wait_queue, &wait,
                                        TASK_UNINTERRUPTIBLE);
                        if (dev->power.runtime_status != RPM_SUSPENDING
                            && dev->power.runtime_status != RPM_RESUMING
                            && !dev->power.idle_notification)
                                break;
                        spin_unlock_irq(&dev->power.lock);

                        schedule();

                        spin_lock_irq(&dev->power.lock);
                }
                finish_wait(&dev->power.wait_queue, &wait);
        }
}

/**
 * pm_runtime_barrier - Flush pending requests and wait for completions.
 * @dev: Device to handle.
 *
 * Prevent the device from being suspended by incrementing its usage counter and
 * if there's a pending resume request for the device, wake the device up.
 * Next, make sure that all pending requests for the device have been flushed
 * from pm_wq and wait for all runtime PM operations involving the device in
 * progress to complete.
 *
 * Return value:
 * 1, if there was a resume request pending and the device had to be woken up,
 * 0, otherwise
 */
int pm_runtime_barrier(struct device *dev)
{
        int retval = 0;

        pm_runtime_get_noresume(dev);
        spin_lock_irq(&dev->power.lock);

        if (dev->power.request_pending
            && dev->power.request == RPM_REQ_RESUME) {
                rpm_resume(dev, 0);
                retval = 1;
        }

        __pm_runtime_barrier(dev);

        spin_unlock_irq(&dev->power.lock);
        pm_runtime_put_noidle(dev);

        return retval;
}
EXPORT_SYMBOL_GPL(pm_runtime_barrier);

/**
 * __pm_runtime_disable - Disable runtime PM of a device.
 * @dev: Device to handle.
 * @check_resume: If set, check if there's a resume request for the device.
 *
 * Increment power.disable_depth for the device and if it was zero previously,
 * cancel all pending runtime PM requests for the device and wait for all
 * operations in progress to complete.  The device can be either active or
 * suspended after its runtime PM has been disabled.
 *
 * If @check_resume is set and there's a resume request pending when
 * __pm_runtime_disable() is called and power.disable_depth is zero, the
 * function will wake up the device before disabling its runtime PM.
 */
void __pm_runtime_disable(struct device *dev, bool check_resume)
{
        spin_lock_irq(&dev->power.lock);

        if (dev->power.disable_depth > 0) {
                dev->power.disable_depth++;
                goto out;
        }

        /*
         * Wake up the device if there's a resume request pending, because that
         * means there probably is some I/O to process and disabling runtime PM
         * shouldn't prevent the device from processing the I/O.
         */
        if (check_resume && dev->power.request_pending
            && dev->power.request == RPM_REQ_RESUME) {
                /*
                 * Prevent suspends and idle notifications from being carried
                 * out after we have woken up the device.
                 */
                pm_runtime_get_noresume(dev);

                rpm_resume(dev, 0);

                pm_runtime_put_noidle(dev);
        }

        if (!dev->power.disable_depth++)
                __pm_runtime_barrier(dev);

 out:
        spin_unlock_irq(&dev->power.lock);
}
EXPORT_SYMBOL_GPL(__pm_runtime_disable);

/**
 * pm_runtime_enable - Enable runtime PM of a device.
 * @dev: Device to handle.
 */
void pm_runtime_enable(struct device *dev)
{
        unsigned long flags;

        spin_lock_irqsave(&dev->power.lock, flags);

        if (dev->power.disable_depth > 0)
                dev->power.disable_depth--;
        else
                dev_warn(dev, "Unbalanced %s!\n", __func__);

        WARN(!dev->power.disable_depth &&
             dev->power.runtime_status == RPM_SUSPENDED &&
             !dev->power.ignore_children &&
             atomic_read(&dev->power.child_count) > 0,
             "Enabling runtime PM for inactive device (%s) with active children\n",
             dev_name(dev));

        spin_unlock_irqrestore(&dev->power.lock, flags);
}
EXPORT_SYMBOL_GPL(pm_runtime_enable);

/**
 * pm_runtime_forbid - Block runtime PM of a device.
 * @dev: Device to handle.
 *
 * Increase the device's usage count and clear its power.runtime_auto flag,
 * so that it cannot be suspended at run time until pm_runtime_allow() is called
 * for it.
 */
void pm_runtime_forbid(struct device *dev)
{
        spin_lock_irq(&dev->power.lock);
        if (!dev->power.runtime_auto)
                goto out;

        dev->power.runtime_auto = false;
        atomic_inc(&dev->power.usage_count);
        rpm_resume(dev, 0);

 out:
        spin_unlock_irq(&dev->power.lock);
}
EXPORT_SYMBOL_GPL(pm_runtime_forbid);

/**
 * pm_runtime_allow - Unblock runtime PM of a device.
 * @dev: Device to handle.
 *
 * Decrease the device's usage count and set its power.runtime_auto flag.
 */
void pm_runtime_allow(struct device *dev)
{
        spin_lock_irq(&dev->power.lock);
        if (dev->power.runtime_auto)
                goto out;

        dev->power.runtime_auto = true;
        if (atomic_dec_and_test(&dev->power.usage_count))
                rpm_idle(dev, RPM_AUTO | RPM_ASYNC);

 out:
        spin_unlock_irq(&dev->power.lock);
}
EXPORT_SYMBOL_GPL(pm_runtime_allow);

/**
 * pm_runtime_no_callbacks - Ignore runtime PM callbacks for a device.
 * @dev: Device to handle.
 *
 * Set the power.no_callbacks flag, which tells the PM core that this
 * device is power-managed through its parent and has no runtime PM
 * callbacks of its own.  The runtime sysfs attributes will be removed.
 */
void pm_runtime_no_callbacks(struct device *dev)
{
        spin_lock_irq(&dev->power.lock);
        dev->power.no_callbacks = 1;
        spin_unlock_irq(&dev->power.lock);
        if (device_is_registered(dev))
                rpm_sysfs_remove(dev);
}
EXPORT_SYMBOL_GPL(pm_runtime_no_callbacks);

/**
 * pm_runtime_irq_safe - Leave interrupts disabled during callbacks.
 * @dev: Device to handle
 *
 * Set the power.irq_safe flag, which tells the PM core that the
 * ->runtime_suspend() and ->runtime_resume() callbacks for this device should
 * always be invoked with the spinlock held and interrupts disabled.  It also
 * causes the parent's usage counter to be permanently incremented, preventing
 * the parent from runtime suspending -- otherwise an irq-safe child might have
 * to wait for a non-irq-safe parent.
 */
void pm_runtime_irq_safe(struct device *dev)
{
        if (dev->parent)
                pm_runtime_get_sync(dev->parent);
        spin_lock_irq(&dev->power.lock);
        dev->power.irq_safe = 1;
        spin_unlock_irq(&dev->power.lock);
}
EXPORT_SYMBOL_GPL(pm_runtime_irq_safe);

/**
 * update_autosuspend - Handle a change to a device's autosuspend settings.
 * @dev: Device to handle.
 * @old_delay: The former autosuspend_delay value.
 * @old_use: The former use_autosuspend value.
 *
 * Prevent runtime suspend if the new delay is negative and use_autosuspend is
 * set; otherwise allow it.  Send an idle notification if suspends are allowed.
 *
 * This function must be called under dev->power.lock with interrupts disabled.
 */
static void update_autosuspend(struct device *dev, int old_delay, int old_use)
{
        int delay = dev->power.autosuspend_delay;

        /* Should runtime suspend be prevented now? */
        if (dev->power.use_autosuspend && delay < 0) {

                /* If it used to be allowed then prevent it. */
                if (!old_use || old_delay >= 0) {
                        atomic_inc(&dev->power.usage_count);
                        rpm_resume(dev, 0);
                }
        }

        /* Runtime suspend should be allowed now. */
        else {

                /* If it used to be prevented then allow it. */
                if (old_use && old_delay < 0)
                        atomic_dec(&dev->power.usage_count);

                /* Maybe we can autosuspend now. */
                rpm_idle(dev, RPM_AUTO);
        }
}

/**
 * pm_runtime_set_autosuspend_delay - Set a device's autosuspend_delay value.
 * @dev: Device to handle.
 * @delay: Value of the new delay in milliseconds.
 *
 * Set the device's power.autosuspend_delay value.  If it changes to negative
 * and the power.use_autosuspend flag is set, prevent runtime suspends.  If it
 * changes the other way, allow runtime suspends.
 */
void pm_runtime_set_autosuspend_delay(struct device *dev, int delay)
{
        int old_delay, old_use;

        spin_lock_irq(&dev->power.lock);
        old_delay = dev->power.autosuspend_delay;
        old_use = dev->power.use_autosuspend;
        dev->power.autosuspend_delay = delay;
        update_autosuspend(dev, old_delay, old_use);
        spin_unlock_irq(&dev->power.lock);
}
EXPORT_SYMBOL_GPL(pm_runtime_set_autosuspend_delay);

/**
 * __pm_runtime_use_autosuspend - Set a device's use_autosuspend flag.
 * @dev: Device to handle.
 * @use: New value for use_autosuspend.
 *
 * Set the device's power.use_autosuspend flag, and allow or prevent runtime
 * suspends as needed.
 */
void __pm_runtime_use_autosuspend(struct device *dev, bool use)
{
        int old_delay, old_use;

        spin_lock_irq(&dev->power.lock);
        old_delay = dev->power.autosuspend_delay;
        old_use = dev->power.use_autosuspend;
        dev->power.use_autosuspend = use;
        update_autosuspend(dev, old_delay, old_use);
        spin_unlock_irq(&dev->power.lock);
}
EXPORT_SYMBOL_GPL(__pm_runtime_use_autosuspend);

/**
 * pm_runtime_init - Initialize runtime PM fields in given device object.
 * @dev: Device object to initialize.
 */
void pm_runtime_init(struct device *dev)
{
        dev->power.runtime_status = RPM_SUSPENDED;
        dev->power.idle_notification = false;

        dev->power.disable_depth = 1;
        atomic_set(&dev->power.usage_count, 0);

        dev->power.runtime_error = 0;

        atomic_set(&dev->power.child_count, 0);
        pm_suspend_ignore_children(dev, false);
        dev->power.runtime_auto = true;

        dev->power.request_pending = false;
        dev->power.request = RPM_REQ_NONE;
        dev->power.deferred_resume = false;
        dev->power.accounting_timestamp = jiffies;
        INIT_WORK(&dev->power.work, pm_runtime_work);

        dev->power.timer_expires = 0;
        timer_setup(&dev->power.suspend_timer, pm_suspend_timer_fn, 0);

        init_waitqueue_head(&dev->power.wait_queue);
}

/**
 * pm_runtime_reinit - Re-initialize runtime PM fields in given device object.
 * @dev: Device object to re-initialize.
 */
void pm_runtime_reinit(struct device *dev)
{
        if (!pm_runtime_enabled(dev)) {
                if (dev->power.runtime_status == RPM_ACTIVE)
                        pm_runtime_set_suspended(dev);
                if (dev->power.irq_safe) {
                        spin_lock_irq(&dev->power.lock);
                        dev->power.irq_safe = 0;
                        spin_unlock_irq(&dev->power.lock);
                        if (dev->parent)
                                pm_runtime_put(dev->parent);
                }
        }
}

/**
 * pm_runtime_remove - Prepare for removing a device from device hierarchy.
 * @dev: Device object being removed from device hierarchy.
 */
void pm_runtime_remove(struct device *dev)
{
        __pm_runtime_disable(dev, false);
        pm_runtime_reinit(dev);
}

/**
 * pm_runtime_clean_up_links - Prepare links to consumers for driver removal.
 * @dev: Device whose driver is going to be removed.
 *
 * Check links from this device to any consumers and if any of them have active
 * runtime PM references to the device, drop the usage counter of the device
 * (once per link).
 *
 * Links with the DL_FLAG_STATELESS flag set are ignored.
 *
 * Since the device is guaranteed to be runtime-active at the point this is
 * called, nothing else needs to be done here.
 *
 * Moreover, this is called after device_links_busy() has returned 'false', so
 * the status of each link is guaranteed to be DL_STATE_SUPPLIER_UNBIND and
 * therefore rpm_active can't be manipulated concurrently.
 */
void pm_runtime_clean_up_links(struct device *dev)
{
        struct device_link *link;
        int idx;

        idx = device_links_read_lock();

        list_for_each_entry_rcu(link, &dev->links.consumers, s_node) {
                if (link->flags & DL_FLAG_STATELESS)
                        continue;

                if (link->rpm_active) {
                        pm_runtime_put_noidle(dev);
                        link->rpm_active = false;
                }
        }

        device_links_read_unlock(idx);
}

/**
 * pm_runtime_get_suppliers - Resume and reference-count supplier devices.
 * @dev: Consumer device.
 */
void pm_runtime_get_suppliers(struct device *dev)
{
        struct device_link *link;
        int idx;

        idx = device_links_read_lock();

        list_for_each_entry_rcu(link, &dev->links.suppliers, c_node)
                if (link->flags & DL_FLAG_PM_RUNTIME)
                        pm_runtime_get_sync(link->supplier);

        device_links_read_unlock(idx);
}

/**
 * pm_runtime_put_suppliers - Drop references to supplier devices.
 * @dev: Consumer device.
 */
void pm_runtime_put_suppliers(struct device *dev)
{
        struct device_link *link;
        int idx;

        idx = device_links_read_lock();

        list_for_each_entry_rcu(link, &dev->links.suppliers, c_node)
                if (link->flags & DL_FLAG_PM_RUNTIME)
                        pm_runtime_put(link->supplier);

        device_links_read_unlock(idx);
}

void pm_runtime_new_link(struct device *dev)
{
        spin_lock_irq(&dev->power.lock);
        dev->power.links_count++;
        spin_unlock_irq(&dev->power.lock);
}

void pm_runtime_drop_link(struct device *dev)
{
        rpm_put_suppliers(dev);

        spin_lock_irq(&dev->power.lock);
        WARN_ON(dev->power.links_count == 0);
        dev->power.links_count--;
        spin_unlock_irq(&dev->power.lock);
}

static bool pm_runtime_need_not_resume(struct device *dev)
{
        return atomic_read(&dev->power.usage_count) <= 1 &&
                (atomic_read(&dev->power.child_count) == 0 ||
                 dev->power.ignore_children);
}

/**
 * pm_runtime_force_suspend - Force a device into suspend state if needed.
 * @dev: Device to suspend.
 *
 * Disable runtime PM so we safely can check the device's runtime PM status and
 * if it is active, invoke its ->runtime_suspend callback to suspend it and
 * change its runtime PM status field to RPM_SUSPENDED.  Also, if the device's
 * usage and children counters don't indicate that the device was in use before
 * the system-wide transition under way, decrement its parent's children counter
 * (if there is a parent).  Keep runtime PM disabled to preserve the state
 * unless we encounter errors.
 *
 * Typically this function may be invoked from a system suspend callback to make
 * sure the device is put into low power state and it should only be used during
 * system-wide PM transitions to sleep states.  It assumes that the analogous
 * pm_runtime_force_resume() will be used to resume the device.
 */
int pm_runtime_force_suspend(struct device *dev)
{
        int (*callback)(struct device *);
        int ret;

        pm_runtime_disable(dev);
        if (pm_runtime_status_suspended(dev))
                return 0;

        callback = RPM_GET_CALLBACK(dev, runtime_suspend);

        ret = callback ? callback(dev) : 0;
        if (ret)
                goto err;

        /*
         * If the device can stay in suspend after the system-wide transition
         * to the working state that will follow, drop the children counter of
         * its parent, but set its status to RPM_SUSPENDED anyway in case this
         * function will be called again for it in the meantime.
         */
        if (pm_runtime_need_not_resume(dev))
                pm_runtime_set_suspended(dev);
        else
                __update_runtime_status(dev, RPM_SUSPENDED);

        return 0;

err:
        pm_runtime_enable(dev);
        return ret;
}
EXPORT_SYMBOL_GPL(pm_runtime_force_suspend);

/**
 * pm_runtime_force_resume - Force a device into resume state if needed.
 * @dev: Device to resume.
 *
 * Prior invoking this function we expect the user to have brought the device
 * into low power state by a call to pm_runtime_force_suspend(). Here we reverse
 * those actions and bring the device into full power, if it is expected to be
 * used on system resume.  In the other case, we defer the resume to be managed
 * via runtime PM.
 *
 * Typically this function may be invoked from a system resume callback.
 */
int pm_runtime_force_resume(struct device *dev)
{
        int (*callback)(struct device *);
        int ret = 0;

        if (!pm_runtime_status_suspended(dev) || pm_runtime_need_not_resume(dev))
                goto out;

        /*
         * The value of the parent's children counter is correct already, so
         * just update the status of the device.
         */
        __update_runtime_status(dev, RPM_ACTIVE);

        callback = RPM_GET_CALLBACK(dev, runtime_resume);

        ret = callback ? callback(dev) : 0;
        if (ret) {
                pm_runtime_set_suspended(dev);
                goto out;
        }

        pm_runtime_mark_last_busy(dev);
out:
        pm_runtime_enable(dev);
        return ret;
}
EXPORT_SYMBOL_GPL(pm_runtime_force_resume);