proc: Fix proc_sys_prune_dcache to hold a sb reference

[cris-mirror.git] / drivers / base / power / main.c

/*
 * drivers/base/power/main.c - Where the driver meets power management.
 *
 * Copyright (c) 2003 Patrick Mochel
 * Copyright (c) 2003 Open Source Development Lab
 *
 * This file is released under the GPLv2
 *
 *
 * The driver model core calls device_pm_add() when a device is registered.
 * This will initialize the embedded device_pm_info object in the device
 * and add it to the list of power-controlled devices. sysfs entries for
 * controlling device power management will also be added.
 *
 * A separate list is used for keeping track of power info, because the power
 * domain dependencies may differ from the ancestral dependencies that the
 * subsystem list maintains.
 */

#include <linux/device.h>
#include <linux/kallsyms.h>
#include <linux/export.h>
#include <linux/mutex.h>
#include <linux/pm.h>
#include <linux/pm_runtime.h>
#include <linux/pm-trace.h>
#include <linux/pm_wakeirq.h>
#include <linux/interrupt.h>
#include <linux/sched.h>
#include <linux/sched/debug.h>
#include <linux/async.h>
#include <linux/suspend.h>
#include <trace/events/power.h>
#include <linux/cpufreq.h>
#include <linux/cpuidle.h>
#include <linux/timer.h>

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

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

/*
 * The entries in the dpm_list list are in a depth first order, simply
 * because children are guaranteed to be discovered after parents, and
 * are inserted at the back of the list on discovery.
 *
 * Since device_pm_add() may be called with a device lock held,
 * we must never try to acquire a device lock while holding
 * dpm_list_mutex.
 */

LIST_HEAD(dpm_list);
static LIST_HEAD(dpm_prepared_list);
static LIST_HEAD(dpm_suspended_list);
static LIST_HEAD(dpm_late_early_list);
static LIST_HEAD(dpm_noirq_list);

struct suspend_stats suspend_stats;
static DEFINE_MUTEX(dpm_list_mtx);
static pm_message_t pm_transition;

static int async_error;

static char *pm_verb(int event)
{
        switch (event) {
        case PM_EVENT_SUSPEND:
                return "suspend";
        case PM_EVENT_RESUME:
                return "resume";
        case PM_EVENT_FREEZE:
                return "freeze";
        case PM_EVENT_QUIESCE:
                return "quiesce";
        case PM_EVENT_HIBERNATE:
                return "hibernate";
        case PM_EVENT_THAW:
                return "thaw";
        case PM_EVENT_RESTORE:
                return "restore";
        case PM_EVENT_RECOVER:
                return "recover";
        default:
                return "(unknown PM event)";
        }
}

/**
 * device_pm_sleep_init - Initialize system suspend-related device fields.
 * @dev: Device object being initialized.
 */
void device_pm_sleep_init(struct device *dev)
{
        dev->power.is_prepared = false;
        dev->power.is_suspended = false;
        dev->power.is_noirq_suspended = false;
        dev->power.is_late_suspended = false;
        init_completion(&dev->power.completion);
        complete_all(&dev->power.completion);
        dev->power.wakeup = NULL;
        INIT_LIST_HEAD(&dev->power.entry);
}

/**
 * device_pm_lock - Lock the list of active devices used by the PM core.
 */
void device_pm_lock(void)
{
        mutex_lock(&dpm_list_mtx);
}

/**
 * device_pm_unlock - Unlock the list of active devices used by the PM core.
 */
void device_pm_unlock(void)
{
        mutex_unlock(&dpm_list_mtx);
}

/**
 * device_pm_add - Add a device to the PM core's list of active devices.
 * @dev: Device to add to the list.
 */
void device_pm_add(struct device *dev)
{
        pr_debug("PM: Adding info for %s:%s\n",
                 dev->bus ? dev->bus->name : "No Bus", dev_name(dev));
        device_pm_check_callbacks(dev);
        mutex_lock(&dpm_list_mtx);
        if (dev->parent && dev->parent->power.is_prepared)
                dev_warn(dev, "parent %s should not be sleeping\n",
                        dev_name(dev->parent));
        list_add_tail(&dev->power.entry, &dpm_list);
        dev->power.in_dpm_list = true;
        mutex_unlock(&dpm_list_mtx);
}

/**
 * device_pm_remove - Remove a device from the PM core's list of active devices.
 * @dev: Device to be removed from the list.
 */
void device_pm_remove(struct device *dev)
{
        pr_debug("PM: Removing info for %s:%s\n",
                 dev->bus ? dev->bus->name : "No Bus", dev_name(dev));
        complete_all(&dev->power.completion);
        mutex_lock(&dpm_list_mtx);
        list_del_init(&dev->power.entry);
        dev->power.in_dpm_list = false;
        mutex_unlock(&dpm_list_mtx);
        device_wakeup_disable(dev);
        pm_runtime_remove(dev);
        device_pm_check_callbacks(dev);
}

/**
 * device_pm_move_before - Move device in the PM core's list of active devices.
 * @deva: Device to move in dpm_list.
 * @devb: Device @deva should come before.
 */
void device_pm_move_before(struct device *deva, struct device *devb)
{
        pr_debug("PM: Moving %s:%s before %s:%s\n",
                 deva->bus ? deva->bus->name : "No Bus", dev_name(deva),
                 devb->bus ? devb->bus->name : "No Bus", dev_name(devb));
        /* Delete deva from dpm_list and reinsert before devb. */
        list_move_tail(&deva->power.entry, &devb->power.entry);
}

/**
 * device_pm_move_after - Move device in the PM core's list of active devices.
 * @deva: Device to move in dpm_list.
 * @devb: Device @deva should come after.
 */
void device_pm_move_after(struct device *deva, struct device *devb)
{
        pr_debug("PM: Moving %s:%s after %s:%s\n",
                 deva->bus ? deva->bus->name : "No Bus", dev_name(deva),
                 devb->bus ? devb->bus->name : "No Bus", dev_name(devb));
        /* Delete deva from dpm_list and reinsert after devb. */
        list_move(&deva->power.entry, &devb->power.entry);
}

/**
 * device_pm_move_last - Move device to end of the PM core's list of devices.
 * @dev: Device to move in dpm_list.
 */
void device_pm_move_last(struct device *dev)
{
        pr_debug("PM: Moving %s:%s to end of list\n",
                 dev->bus ? dev->bus->name : "No Bus", dev_name(dev));
        list_move_tail(&dev->power.entry, &dpm_list);
}

static ktime_t initcall_debug_start(struct device *dev)
{
        ktime_t calltime = 0;

        if (pm_print_times_enabled) {
                pr_info("calling  %s+ @ %i, parent: %s\n",
                        dev_name(dev), task_pid_nr(current),
                        dev->parent ? dev_name(dev->parent) : "none");
                calltime = ktime_get();
        }

        return calltime;
}

static void initcall_debug_report(struct device *dev, ktime_t calltime,
                                  int error, pm_message_t state, char *info)
{
        ktime_t rettime;
        s64 nsecs;

        rettime = ktime_get();
        nsecs = (s64) ktime_to_ns(ktime_sub(rettime, calltime));

        if (pm_print_times_enabled) {
                pr_info("call %s+ returned %d after %Ld usecs\n", dev_name(dev),
                        error, (unsigned long long)nsecs >> 10);
        }
}

/**
 * dpm_wait - Wait for a PM operation to complete.
 * @dev: Device to wait for.
 * @async: If unset, wait only if the device's power.async_suspend flag is set.
 */
static void dpm_wait(struct device *dev, bool async)
{
        if (!dev)
                return;

        if (async || (pm_async_enabled && dev->power.async_suspend))
                wait_for_completion(&dev->power.completion);
}

static int dpm_wait_fn(struct device *dev, void *async_ptr)
{
        dpm_wait(dev, *((bool *)async_ptr));
        return 0;
}

static void dpm_wait_for_children(struct device *dev, bool async)
{
       device_for_each_child(dev, &async, dpm_wait_fn);
}

static void dpm_wait_for_suppliers(struct device *dev, bool async)
{
        struct device_link *link;
        int idx;

        idx = device_links_read_lock();

        /*
         * If the supplier goes away right after we've checked the link to it,
         * we'll wait for its completion to change the state, but that's fine,
         * because the only things that will block as a result are the SRCU
         * callbacks freeing the link objects for the links in the list we're
         * walking.
         */
        list_for_each_entry_rcu(link, &dev->links.suppliers, c_node)
                if (READ_ONCE(link->status) != DL_STATE_DORMANT)
                        dpm_wait(link->supplier, async);

        device_links_read_unlock(idx);
}

static void dpm_wait_for_superior(struct device *dev, bool async)
{
        dpm_wait(dev->parent, async);
        dpm_wait_for_suppliers(dev, async);
}

static void dpm_wait_for_consumers(struct device *dev, bool async)
{
        struct device_link *link;
        int idx;

        idx = device_links_read_lock();

        /*
         * The status of a device link can only be changed from "dormant" by a
         * probe, but that cannot happen during system suspend/resume.  In
         * theory it can change to "dormant" at that time, but then it is
         * reasonable to wait for the target device anyway (eg. if it goes
         * away, it's better to wait for it to go away completely and then
         * continue instead of trying to continue in parallel with its
         * unregistration).
         */
        list_for_each_entry_rcu(link, &dev->links.consumers, s_node)
                if (READ_ONCE(link->status) != DL_STATE_DORMANT)
                        dpm_wait(link->consumer, async);

        device_links_read_unlock(idx);
}

static void dpm_wait_for_subordinate(struct device *dev, bool async)
{
        dpm_wait_for_children(dev, async);
        dpm_wait_for_consumers(dev, async);
}

/**
 * pm_op - Return the PM operation appropriate for given PM event.
 * @ops: PM operations to choose from.
 * @state: PM transition of the system being carried out.
 */
static pm_callback_t pm_op(const struct dev_pm_ops *ops, pm_message_t state)
{
        switch (state.event) {
#ifdef CONFIG_SUSPEND
        case PM_EVENT_SUSPEND:
                return ops->suspend;
        case PM_EVENT_RESUME:
                return ops->resume;
#endif /* CONFIG_SUSPEND */
#ifdef CONFIG_HIBERNATE_CALLBACKS
        case PM_EVENT_FREEZE:
        case PM_EVENT_QUIESCE:
                return ops->freeze;
        case PM_EVENT_HIBERNATE:
                return ops->poweroff;
        case PM_EVENT_THAW:
        case PM_EVENT_RECOVER:
                return ops->thaw;
                break;
        case PM_EVENT_RESTORE:
                return ops->restore;
#endif /* CONFIG_HIBERNATE_CALLBACKS */
        }

        return NULL;
}

/**
 * pm_late_early_op - Return the PM operation appropriate for given PM event.
 * @ops: PM operations to choose from.
 * @state: PM transition of the system being carried out.
 *
 * Runtime PM is disabled for @dev while this function is being executed.
 */
static pm_callback_t pm_late_early_op(const struct dev_pm_ops *ops,
                                      pm_message_t state)
{
        switch (state.event) {
#ifdef CONFIG_SUSPEND
        case PM_EVENT_SUSPEND:
                return ops->suspend_late;
        case PM_EVENT_RESUME:
                return ops->resume_early;
#endif /* CONFIG_SUSPEND */
#ifdef CONFIG_HIBERNATE_CALLBACKS
        case PM_EVENT_FREEZE:
        case PM_EVENT_QUIESCE:
                return ops->freeze_late;
        case PM_EVENT_HIBERNATE:
                return ops->poweroff_late;
        case PM_EVENT_THAW:
        case PM_EVENT_RECOVER:
                return ops->thaw_early;
        case PM_EVENT_RESTORE:
                return ops->restore_early;
#endif /* CONFIG_HIBERNATE_CALLBACKS */
        }

        return NULL;
}

/**
 * pm_noirq_op - Return the PM operation appropriate for given PM event.
 * @ops: PM operations to choose from.
 * @state: PM transition of the system being carried out.
 *
 * The driver of @dev will not receive interrupts while this function is being
 * executed.
 */
static pm_callback_t pm_noirq_op(const struct dev_pm_ops *ops, pm_message_t state)
{
        switch (state.event) {
#ifdef CONFIG_SUSPEND
        case PM_EVENT_SUSPEND:
                return ops->suspend_noirq;
        case PM_EVENT_RESUME:
                return ops->resume_noirq;
#endif /* CONFIG_SUSPEND */
#ifdef CONFIG_HIBERNATE_CALLBACKS
        case PM_EVENT_FREEZE:
        case PM_EVENT_QUIESCE:
                return ops->freeze_noirq;
        case PM_EVENT_HIBERNATE:
                return ops->poweroff_noirq;
        case PM_EVENT_THAW:
        case PM_EVENT_RECOVER:
                return ops->thaw_noirq;
        case PM_EVENT_RESTORE:
                return ops->restore_noirq;
#endif /* CONFIG_HIBERNATE_CALLBACKS */
        }

        return NULL;
}

static void pm_dev_dbg(struct device *dev, pm_message_t state, char *info)
{
        dev_dbg(dev, "%s%s%s\n", info, pm_verb(state.event),
                ((state.event & PM_EVENT_SLEEP) && device_may_wakeup(dev)) ?
                ", may wakeup" : "");
}

static void pm_dev_err(struct device *dev, pm_message_t state, char *info,
                        int error)
{
        printk(KERN_ERR "PM: Device %s failed to %s%s: error %d\n",
                dev_name(dev), pm_verb(state.event), info, error);
}

static void dpm_show_time(ktime_t starttime, pm_message_t state, char *info)
{
        ktime_t calltime;
        u64 usecs64;
        int usecs;

        calltime = ktime_get();
        usecs64 = ktime_to_ns(ktime_sub(calltime, starttime));
        do_div(usecs64, NSEC_PER_USEC);
        usecs = usecs64;
        if (usecs == 0)
                usecs = 1;
        pr_info("PM: %s%s%s of devices complete after %ld.%03ld msecs\n",
                info ?: "", info ? " " : "", pm_verb(state.event),
                usecs / USEC_PER_MSEC, usecs % USEC_PER_MSEC);
}

static int dpm_run_callback(pm_callback_t cb, struct device *dev,
                            pm_message_t state, char *info)
{
        ktime_t calltime;
        int error;

        if (!cb)
                return 0;

        calltime = initcall_debug_start(dev);

        pm_dev_dbg(dev, state, info);
        trace_device_pm_callback_start(dev, info, state.event);
        error = cb(dev);
        trace_device_pm_callback_end(dev, error);
        suspend_report_result(cb, error);

        initcall_debug_report(dev, calltime, error, state, info);

        return error;
}

#ifdef CONFIG_DPM_WATCHDOG
struct dpm_watchdog {
        struct device           *dev;
        struct task_struct      *tsk;
        struct timer_list       timer;
};

#define DECLARE_DPM_WATCHDOG_ON_STACK(wd) \
        struct dpm_watchdog wd

/**
 * dpm_watchdog_handler - Driver suspend / resume watchdog handler.
 * @data: Watchdog object address.
 *
 * Called when a driver has timed out suspending or resuming.
 * There's not much we can do here to recover so panic() to
 * capture a crash-dump in pstore.
 */
static void dpm_watchdog_handler(unsigned long data)
{
        struct dpm_watchdog *wd = (void *)data;

        dev_emerg(wd->dev, "**** DPM device timeout ****\n");
        show_stack(wd->tsk, NULL);
        panic("%s %s: unrecoverable failure\n",
                dev_driver_string(wd->dev), dev_name(wd->dev));
}

/**
 * dpm_watchdog_set - Enable pm watchdog for given device.
 * @wd: Watchdog. Must be allocated on the stack.
 * @dev: Device to handle.
 */
static void dpm_watchdog_set(struct dpm_watchdog *wd, struct device *dev)
{
        struct timer_list *timer = &wd->timer;

        wd->dev = dev;
        wd->tsk = current;

        init_timer_on_stack(timer);
        /* use same timeout value for both suspend and resume */
        timer->expires = jiffies + HZ * CONFIG_DPM_WATCHDOG_TIMEOUT;
        timer->function = dpm_watchdog_handler;
        timer->data = (unsigned long)wd;
        add_timer(timer);
}

/**
 * dpm_watchdog_clear - Disable suspend/resume watchdog.
 * @wd: Watchdog to disable.
 */
static void dpm_watchdog_clear(struct dpm_watchdog *wd)
{
        struct timer_list *timer = &wd->timer;

        del_timer_sync(timer);
        destroy_timer_on_stack(timer);
}
#else
#define DECLARE_DPM_WATCHDOG_ON_STACK(wd)
#define dpm_watchdog_set(x, y)
#define dpm_watchdog_clear(x)
#endif

/*------------------------- Resume routines -------------------------*/

/**
 * device_resume_noirq - Execute an "early resume" callback for given device.
 * @dev: Device to handle.
 * @state: PM transition of the system being carried out.
 * @async: If true, the device is being resumed asynchronously.
 *
 * The driver of @dev will not receive interrupts while this function is being
 * executed.
 */
static int device_resume_noirq(struct device *dev, pm_message_t state, bool async)
{
        pm_callback_t callback = NULL;
        char *info = NULL;
        int error = 0;

        TRACE_DEVICE(dev);
        TRACE_RESUME(0);

        if (dev->power.syscore || dev->power.direct_complete)
                goto Out;

        if (!dev->power.is_noirq_suspended)
                goto Out;

        dpm_wait_for_superior(dev, async);

        if (dev->pm_domain) {
                info = "noirq power domain ";
                callback = pm_noirq_op(&dev->pm_domain->ops, state);
        } else if (dev->type && dev->type->pm) {
                info = "noirq type ";
                callback = pm_noirq_op(dev->type->pm, state);
        } else if (dev->class && dev->class->pm) {
                info = "noirq class ";
                callback = pm_noirq_op(dev->class->pm, state);
        } else if (dev->bus && dev->bus->pm) {
                info = "noirq bus ";
                callback = pm_noirq_op(dev->bus->pm, state);
        }

        if (!callback && dev->driver && dev->driver->pm) {
                info = "noirq driver ";
                callback = pm_noirq_op(dev->driver->pm, state);
        }

        error = dpm_run_callback(callback, dev, state, info);
        dev->power.is_noirq_suspended = false;

 Out:
        complete_all(&dev->power.completion);
        TRACE_RESUME(error);
        return error;
}

static bool is_async(struct device *dev)
{
        return dev->power.async_suspend && pm_async_enabled
                && !pm_trace_is_enabled();
}

static void async_resume_noirq(void *data, async_cookie_t cookie)
{
        struct device *dev = (struct device *)data;
        int error;

        error = device_resume_noirq(dev, pm_transition, true);
        if (error)
                pm_dev_err(dev, pm_transition, " async", error);

        put_device(dev);
}

/**
 * dpm_resume_noirq - Execute "noirq resume" callbacks for all devices.
 * @state: PM transition of the system being carried out.
 *
 * Call the "noirq" resume handlers for all devices in dpm_noirq_list and
 * enable device drivers to receive interrupts.
 */
void dpm_resume_noirq(pm_message_t state)
{
        struct device *dev;
        ktime_t starttime = ktime_get();

        trace_suspend_resume(TPS("dpm_resume_noirq"), state.event, true);
        mutex_lock(&dpm_list_mtx);
        pm_transition = state;

        /*
         * Advanced the async threads upfront,
         * in case the starting of async threads is
         * delayed by non-async resuming devices.
         */
        list_for_each_entry(dev, &dpm_noirq_list, power.entry) {
                reinit_completion(&dev->power.completion);
                if (is_async(dev)) {
                        get_device(dev);
                        async_schedule(async_resume_noirq, dev);
                }
        }

        while (!list_empty(&dpm_noirq_list)) {
                dev = to_device(dpm_noirq_list.next);
                get_device(dev);
                list_move_tail(&dev->power.entry, &dpm_late_early_list);
                mutex_unlock(&dpm_list_mtx);

                if (!is_async(dev)) {
                        int error;

                        error = device_resume_noirq(dev, state, false);
                        if (error) {
                                suspend_stats.failed_resume_noirq++;
                                dpm_save_failed_step(SUSPEND_RESUME_NOIRQ);
                                dpm_save_failed_dev(dev_name(dev));
                                pm_dev_err(dev, state, " noirq", error);
                        }
                }

                mutex_lock(&dpm_list_mtx);
                put_device(dev);
        }
        mutex_unlock(&dpm_list_mtx);
        async_synchronize_full();
        dpm_show_time(starttime, state, "noirq");
        resume_device_irqs();
        device_wakeup_disarm_wake_irqs();
        cpuidle_resume();
        trace_suspend_resume(TPS("dpm_resume_noirq"), state.event, false);
}

/**
 * device_resume_early - Execute an "early resume" callback for given device.
 * @dev: Device to handle.
 * @state: PM transition of the system being carried out.
 * @async: If true, the device is being resumed asynchronously.
 *
 * Runtime PM is disabled for @dev while this function is being executed.
 */
static int device_resume_early(struct device *dev, pm_message_t state, bool async)
{
        pm_callback_t callback = NULL;
        char *info = NULL;
        int error = 0;

        TRACE_DEVICE(dev);
        TRACE_RESUME(0);

        if (dev->power.syscore || dev->power.direct_complete)
                goto Out;

        if (!dev->power.is_late_suspended)
                goto Out;

        dpm_wait_for_superior(dev, async);

        if (dev->pm_domain) {
                info = "early power domain ";
                callback = pm_late_early_op(&dev->pm_domain->ops, state);
        } else if (dev->type && dev->type->pm) {
                info = "early type ";
                callback = pm_late_early_op(dev->type->pm, state);
        } else if (dev->class && dev->class->pm) {
                info = "early class ";
                callback = pm_late_early_op(dev->class->pm, state);
        } else if (dev->bus && dev->bus->pm) {
                info = "early bus ";
                callback = pm_late_early_op(dev->bus->pm, state);
        }

        if (!callback && dev->driver && dev->driver->pm) {
                info = "early driver ";
                callback = pm_late_early_op(dev->driver->pm, state);
        }

        error = dpm_run_callback(callback, dev, state, info);
        dev->power.is_late_suspended = false;

 Out:
        TRACE_RESUME(error);

        pm_runtime_enable(dev);
        complete_all(&dev->power.completion);
        return error;
}

static void async_resume_early(void *data, async_cookie_t cookie)
{
        struct device *dev = (struct device *)data;
        int error;

        error = device_resume_early(dev, pm_transition, true);
        if (error)
                pm_dev_err(dev, pm_transition, " async", error);

        put_device(dev);
}

/**
 * dpm_resume_early - Execute "early resume" callbacks for all devices.
 * @state: PM transition of the system being carried out.
 */
void dpm_resume_early(pm_message_t state)
{
        struct device *dev;
        ktime_t starttime = ktime_get();

        trace_suspend_resume(TPS("dpm_resume_early"), state.event, true);
        mutex_lock(&dpm_list_mtx);
        pm_transition = state;

        /*
         * Advanced the async threads upfront,
         * in case the starting of async threads is
         * delayed by non-async resuming devices.
         */
        list_for_each_entry(dev, &dpm_late_early_list, power.entry) {
                reinit_completion(&dev->power.completion);
                if (is_async(dev)) {
                        get_device(dev);
                        async_schedule(async_resume_early, dev);
                }
        }

        while (!list_empty(&dpm_late_early_list)) {
                dev = to_device(dpm_late_early_list.next);
                get_device(dev);
                list_move_tail(&dev->power.entry, &dpm_suspended_list);
                mutex_unlock(&dpm_list_mtx);

                if (!is_async(dev)) {
                        int error;

                        error = device_resume_early(dev, state, false);
                        if (error) {
                                suspend_stats.failed_resume_early++;
                                dpm_save_failed_step(SUSPEND_RESUME_EARLY);
                                dpm_save_failed_dev(dev_name(dev));
                                pm_dev_err(dev, state, " early", error);
                        }
                }
                mutex_lock(&dpm_list_mtx);
                put_device(dev);
        }
        mutex_unlock(&dpm_list_mtx);
        async_synchronize_full();
        dpm_show_time(starttime, state, "early");
        trace_suspend_resume(TPS("dpm_resume_early"), state.event, false);
}

/**
 * dpm_resume_start - Execute "noirq" and "early" device callbacks.
 * @state: PM transition of the system being carried out.
 */
void dpm_resume_start(pm_message_t state)
{
        dpm_resume_noirq(state);
        dpm_resume_early(state);
}
EXPORT_SYMBOL_GPL(dpm_resume_start);

/**
 * device_resume - Execute "resume" callbacks for given device.
 * @dev: Device to handle.
 * @state: PM transition of the system being carried out.
 * @async: If true, the device is being resumed asynchronously.
 */
static int device_resume(struct device *dev, pm_message_t state, bool async)
{
        pm_callback_t callback = NULL;
        char *info = NULL;
        int error = 0;
        DECLARE_DPM_WATCHDOG_ON_STACK(wd);

        TRACE_DEVICE(dev);
        TRACE_RESUME(0);

        if (dev->power.syscore)
                goto Complete;

        if (dev->power.direct_complete) {
                /* Match the pm_runtime_disable() in __device_suspend(). */
                pm_runtime_enable(dev);
                goto Complete;
        }

        dpm_wait_for_superior(dev, async);
        dpm_watchdog_set(&wd, dev);
        device_lock(dev);

        /*
         * This is a fib.  But we'll allow new children to be added below
         * a resumed device, even if the device hasn't been completed yet.
         */
        dev->power.is_prepared = false;

        if (!dev->power.is_suspended)
                goto Unlock;

        if (dev->pm_domain) {
                info = "power domain ";
                callback = pm_op(&dev->pm_domain->ops, state);
                goto Driver;
        }

        if (dev->type && dev->type->pm) {
                info = "type ";
                callback = pm_op(dev->type->pm, state);
                goto Driver;
        }

        if (dev->class) {
                if (dev->class->pm) {
                        info = "class ";
                        callback = pm_op(dev->class->pm, state);
                        goto Driver;
                } else if (dev->class->resume) {
                        info = "legacy class ";
                        callback = dev->class->resume;
                        goto End;
                }
        }

        if (dev->bus) {
                if (dev->bus->pm) {
                        info = "bus ";
                        callback = pm_op(dev->bus->pm, state);
                } else if (dev->bus->resume) {
                        info = "legacy bus ";
                        callback = dev->bus->resume;
                        goto End;
                }
        }

 Driver:
        if (!callback && dev->driver && dev->driver->pm) {
                info = "driver ";
                callback = pm_op(dev->driver->pm, state);
        }

 End:
        error = dpm_run_callback(callback, dev, state, info);
        dev->power.is_suspended = false;

 Unlock:
        device_unlock(dev);
        dpm_watchdog_clear(&wd);

 Complete:
        complete_all(&dev->power.completion);

        TRACE_RESUME(error);

        return error;
}

static void async_resume(void *data, async_cookie_t cookie)
{
        struct device *dev = (struct device *)data;
        int error;

        error = device_resume(dev, pm_transition, true);
        if (error)
                pm_dev_err(dev, pm_transition, " async", error);
        put_device(dev);
}

/**
 * dpm_resume - Execute "resume" callbacks for non-sysdev devices.
 * @state: PM transition of the system being carried out.
 *
 * Execute the appropriate "resume" callback for all devices whose status
 * indicates that they are suspended.
 */
void dpm_resume(pm_message_t state)
{
        struct device *dev;
        ktime_t starttime = ktime_get();

        trace_suspend_resume(TPS("dpm_resume"), state.event, true);
        might_sleep();

        mutex_lock(&dpm_list_mtx);
        pm_transition = state;
        async_error = 0;

        list_for_each_entry(dev, &dpm_suspended_list, power.entry) {
                reinit_completion(&dev->power.completion);
                if (is_async(dev)) {
                        get_device(dev);
                        async_schedule(async_resume, dev);
                }
        }

        while (!list_empty(&dpm_suspended_list)) {
                dev = to_device(dpm_suspended_list.next);
                get_device(dev);
                if (!is_async(dev)) {
                        int error;

                        mutex_unlock(&dpm_list_mtx);

                        error = device_resume(dev, state, false);
                        if (error) {
                                suspend_stats.failed_resume++;
                                dpm_save_failed_step(SUSPEND_RESUME);
                                dpm_save_failed_dev(dev_name(dev));
                                pm_dev_err(dev, state, "", error);
                        }

                        mutex_lock(&dpm_list_mtx);
                }
                if (!list_empty(&dev->power.entry))
                        list_move_tail(&dev->power.entry, &dpm_prepared_list);
                put_device(dev);
        }
        mutex_unlock(&dpm_list_mtx);
        async_synchronize_full();
        dpm_show_time(starttime, state, NULL);

        cpufreq_resume();
        trace_suspend_resume(TPS("dpm_resume"), state.event, false);
}

/**
 * device_complete - Complete a PM transition for given device.
 * @dev: Device to handle.
 * @state: PM transition of the system being carried out.
 */
static void device_complete(struct device *dev, pm_message_t state)
{
        void (*callback)(struct device *) = NULL;
        char *info = NULL;

        if (dev->power.syscore)
                return;

        device_lock(dev);

        if (dev->pm_domain) {
                info = "completing power domain ";
                callback = dev->pm_domain->ops.complete;
        } else if (dev->type && dev->type->pm) {
                info = "completing type ";
                callback = dev->type->pm->complete;
        } else if (dev->class && dev->class->pm) {
                info = "completing class ";
                callback = dev->class->pm->complete;
        } else if (dev->bus && dev->bus->pm) {
                info = "completing bus ";
                callback = dev->bus->pm->complete;
        }

        if (!callback && dev->driver && dev->driver->pm) {
                info = "completing driver ";
                callback = dev->driver->pm->complete;
        }

        if (callback) {
                pm_dev_dbg(dev, state, info);
                callback(dev);
        }

        device_unlock(dev);

        pm_runtime_put(dev);
}

/**
 * dpm_complete - Complete a PM transition for all non-sysdev devices.
 * @state: PM transition of the system being carried out.
 *
 * Execute the ->complete() callbacks for all devices whose PM status is not
 * DPM_ON (this allows new devices to be registered).
 */
void dpm_complete(pm_message_t state)
{
        struct list_head list;

        trace_suspend_resume(TPS("dpm_complete"), state.event, true);
        might_sleep();

        INIT_LIST_HEAD(&list);
        mutex_lock(&dpm_list_mtx);
        while (!list_empty(&dpm_prepared_list)) {
                struct device *dev = to_device(dpm_prepared_list.prev);

                get_device(dev);
                dev->power.is_prepared = false;
                list_move(&dev->power.entry, &list);
                mutex_unlock(&dpm_list_mtx);

                trace_device_pm_callback_start(dev, "", state.event);
                device_complete(dev, state);
                trace_device_pm_callback_end(dev, 0);

                mutex_lock(&dpm_list_mtx);
                put_device(dev);
        }
        list_splice(&list, &dpm_list);
        mutex_unlock(&dpm_list_mtx);

        /* Allow device probing and trigger re-probing of deferred devices */
        device_unblock_probing();
        trace_suspend_resume(TPS("dpm_complete"), state.event, false);
}

/**
 * dpm_resume_end - Execute "resume" callbacks and complete system transition.
 * @state: PM transition of the system being carried out.
 *
 * Execute "resume" callbacks for all devices and complete the PM transition of
 * the system.
 */
void dpm_resume_end(pm_message_t state)
{
        dpm_resume(state);
        dpm_complete(state);
}
EXPORT_SYMBOL_GPL(dpm_resume_end);


/*------------------------- Suspend routines -------------------------*/

/**
 * resume_event - Return a "resume" message for given "suspend" sleep state.
 * @sleep_state: PM message representing a sleep state.
 *
 * Return a PM message representing the resume event corresponding to given
 * sleep state.
 */
static pm_message_t resume_event(pm_message_t sleep_state)
{
        switch (sleep_state.event) {
        case PM_EVENT_SUSPEND:
                return PMSG_RESUME;
        case PM_EVENT_FREEZE:
        case PM_EVENT_QUIESCE:
                return PMSG_RECOVER;
        case PM_EVENT_HIBERNATE:
                return PMSG_RESTORE;
        }
        return PMSG_ON;
}

/**
 * device_suspend_noirq - Execute a "late suspend" callback for given device.
 * @dev: Device to handle.
 * @state: PM transition of the system being carried out.
 * @async: If true, the device is being suspended asynchronously.
 *
 * The driver of @dev will not receive interrupts while this function is being
 * executed.
 */
static int __device_suspend_noirq(struct device *dev, pm_message_t state, bool async)
{
        pm_callback_t callback = NULL;
        char *info = NULL;
        int error = 0;

        TRACE_DEVICE(dev);
        TRACE_SUSPEND(0);

        dpm_wait_for_subordinate(dev, async);

        if (async_error)
                goto Complete;

        if (dev->power.syscore || dev->power.direct_complete)
                goto Complete;

        if (dev->pm_domain) {
                info = "noirq power domain ";
                callback = pm_noirq_op(&dev->pm_domain->ops, state);
        } else if (dev->type && dev->type->pm) {
                info = "noirq type ";
                callback = pm_noirq_op(dev->type->pm, state);
        } else if (dev->class && dev->class->pm) {
                info = "noirq class ";
                callback = pm_noirq_op(dev->class->pm, state);
        } else if (dev->bus && dev->bus->pm) {
                info = "noirq bus ";
                callback = pm_noirq_op(dev->bus->pm, state);
        }

        if (!callback && dev->driver && dev->driver->pm) {
                info = "noirq driver ";
                callback = pm_noirq_op(dev->driver->pm, state);
        }

        error = dpm_run_callback(callback, dev, state, info);
        if (!error)
                dev->power.is_noirq_suspended = true;
        else
                async_error = error;

Complete:
        complete_all(&dev->power.completion);
        TRACE_SUSPEND(error);
        return error;
}

static void async_suspend_noirq(void *data, async_cookie_t cookie)
{
        struct device *dev = (struct device *)data;
        int error;

        error = __device_suspend_noirq(dev, pm_transition, true);
        if (error) {
                dpm_save_failed_dev(dev_name(dev));
                pm_dev_err(dev, pm_transition, " async", error);
        }

        put_device(dev);
}

static int device_suspend_noirq(struct device *dev)
{
        reinit_completion(&dev->power.completion);

        if (is_async(dev)) {
                get_device(dev);
                async_schedule(async_suspend_noirq, dev);
                return 0;
        }
        return __device_suspend_noirq(dev, pm_transition, false);
}

/**
 * dpm_suspend_noirq - Execute "noirq suspend" callbacks for all devices.
 * @state: PM transition of the system being carried out.
 *
 * Prevent device drivers from receiving interrupts and call the "noirq" suspend
 * handlers for all non-sysdev devices.
 */
int dpm_suspend_noirq(pm_message_t state)
{
        ktime_t starttime = ktime_get();
        int error = 0;

        trace_suspend_resume(TPS("dpm_suspend_noirq"), state.event, true);
        cpuidle_pause();
        device_wakeup_arm_wake_irqs();
        suspend_device_irqs();
        mutex_lock(&dpm_list_mtx);
        pm_transition = state;
        async_error = 0;

        while (!list_empty(&dpm_late_early_list)) {
                struct device *dev = to_device(dpm_late_early_list.prev);

                get_device(dev);
                mutex_unlock(&dpm_list_mtx);

                error = device_suspend_noirq(dev);

                mutex_lock(&dpm_list_mtx);
                if (error) {
                        pm_dev_err(dev, state, " noirq", error);
                        dpm_save_failed_dev(dev_name(dev));
                        put_device(dev);
                        break;
                }
                if (!list_empty(&dev->power.entry))
                        list_move(&dev->power.entry, &dpm_noirq_list);
                put_device(dev);

                if (async_error)
                        break;
        }
        mutex_unlock(&dpm_list_mtx);
        async_synchronize_full();
        if (!error)
                error = async_error;

        if (error) {
                suspend_stats.failed_suspend_noirq++;
                dpm_save_failed_step(SUSPEND_SUSPEND_NOIRQ);
                dpm_resume_noirq(resume_event(state));
        } else {
                dpm_show_time(starttime, state, "noirq");
        }
        trace_suspend_resume(TPS("dpm_suspend_noirq"), state.event, false);
        return error;
}

/**
 * device_suspend_late - Execute a "late suspend" callback for given device.
 * @dev: Device to handle.
 * @state: PM transition of the system being carried out.
 * @async: If true, the device is being suspended asynchronously.
 *
 * Runtime PM is disabled for @dev while this function is being executed.
 */
static int __device_suspend_late(struct device *dev, pm_message_t state, bool async)
{
        pm_callback_t callback = NULL;
        char *info = NULL;
        int error = 0;

        TRACE_DEVICE(dev);
        TRACE_SUSPEND(0);

        __pm_runtime_disable(dev, false);

        dpm_wait_for_subordinate(dev, async);

        if (async_error)
                goto Complete;

        if (pm_wakeup_pending()) {
                async_error = -EBUSY;
                goto Complete;
        }

        if (dev->power.syscore || dev->power.direct_complete)
                goto Complete;

        if (dev->pm_domain) {
                info = "late power domain ";
                callback = pm_late_early_op(&dev->pm_domain->ops, state);
        } else if (dev->type && dev->type->pm) {
                info = "late type ";
                callback = pm_late_early_op(dev->type->pm, state);
        } else if (dev->class && dev->class->pm) {
                info = "late class ";
                callback = pm_late_early_op(dev->class->pm, state);
        } else if (dev->bus && dev->bus->pm) {
                info = "late bus ";
                callback = pm_late_early_op(dev->bus->pm, state);
        }

        if (!callback && dev->driver && dev->driver->pm) {
                info = "late driver ";
                callback = pm_late_early_op(dev->driver->pm, state);
        }

        error = dpm_run_callback(callback, dev, state, info);
        if (!error)
                dev->power.is_late_suspended = true;
        else
                async_error = error;

Complete:
        TRACE_SUSPEND(error);
        complete_all(&dev->power.completion);
        return error;
}

static void async_suspend_late(void *data, async_cookie_t cookie)
{
        struct device *dev = (struct device *)data;
        int error;

        error = __device_suspend_late(dev, pm_transition, true);
        if (error) {
                dpm_save_failed_dev(dev_name(dev));
                pm_dev_err(dev, pm_transition, " async", error);
        }
        put_device(dev);
}

static int device_suspend_late(struct device *dev)
{
        reinit_completion(&dev->power.completion);

        if (is_async(dev)) {
                get_device(dev);
                async_schedule(async_suspend_late, dev);
                return 0;
        }

        return __device_suspend_late(dev, pm_transition, false);
}

/**
 * dpm_suspend_late - Execute "late suspend" callbacks for all devices.
 * @state: PM transition of the system being carried out.
 */
int dpm_suspend_late(pm_message_t state)
{
        ktime_t starttime = ktime_get();
        int error = 0;

        trace_suspend_resume(TPS("dpm_suspend_late"), state.event, true);
        mutex_lock(&dpm_list_mtx);
        pm_transition = state;
        async_error = 0;

        while (!list_empty(&dpm_suspended_list)) {
                struct device *dev = to_device(dpm_suspended_list.prev);

                get_device(dev);
                mutex_unlock(&dpm_list_mtx);

                error = device_suspend_late(dev);

                mutex_lock(&dpm_list_mtx);
                if (!list_empty(&dev->power.entry))
                        list_move(&dev->power.entry, &dpm_late_early_list);

                if (error) {
                        pm_dev_err(dev, state, " late", error);
                        dpm_save_failed_dev(dev_name(dev));
                        put_device(dev);
                        break;
                }
                put_device(dev);

                if (async_error)
                        break;
        }
        mutex_unlock(&dpm_list_mtx);
        async_synchronize_full();
        if (!error)
                error = async_error;
        if (error) {
                suspend_stats.failed_suspend_late++;
                dpm_save_failed_step(SUSPEND_SUSPEND_LATE);
                dpm_resume_early(resume_event(state));
        } else {
                dpm_show_time(starttime, state, "late");
        }
        trace_suspend_resume(TPS("dpm_suspend_late"), state.event, false);
        return error;
}

/**
 * dpm_suspend_end - Execute "late" and "noirq" device suspend callbacks.
 * @state: PM transition of the system being carried out.
 */
int dpm_suspend_end(pm_message_t state)
{
        int error = dpm_suspend_late(state);
        if (error)
                return error;

        error = dpm_suspend_noirq(state);
        if (error) {
                dpm_resume_early(resume_event(state));
                return error;
        }

        return 0;
}
EXPORT_SYMBOL_GPL(dpm_suspend_end);

/**
 * legacy_suspend - Execute a legacy (bus or class) suspend callback for device.
 * @dev: Device to suspend.
 * @state: PM transition of the system being carried out.
 * @cb: Suspend callback to execute.
 * @info: string description of caller.
 */
static int legacy_suspend(struct device *dev, pm_message_t state,
                          int (*cb)(struct device *dev, pm_message_t state),
                          char *info)
{
        int error;
        ktime_t calltime;

        calltime = initcall_debug_start(dev);

        trace_device_pm_callback_start(dev, info, state.event);
        error = cb(dev, state);
        trace_device_pm_callback_end(dev, error);
        suspend_report_result(cb, error);

        initcall_debug_report(dev, calltime, error, state, info);

        return error;
}

static void dpm_clear_suppliers_direct_complete(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) {
                spin_lock_irq(&link->supplier->power.lock);
                link->supplier->power.direct_complete = false;
                spin_unlock_irq(&link->supplier->power.lock);
        }

        device_links_read_unlock(idx);
}

/**
 * device_suspend - Execute "suspend" callbacks for given device.
 * @dev: Device to handle.
 * @state: PM transition of the system being carried out.
 * @async: If true, the device is being suspended asynchronously.
 */
static int __device_suspend(struct device *dev, pm_message_t state, bool async)
{
        pm_callback_t callback = NULL;
        char *info = NULL;
        int error = 0;
        DECLARE_DPM_WATCHDOG_ON_STACK(wd);

        TRACE_DEVICE(dev);
        TRACE_SUSPEND(0);

        dpm_wait_for_subordinate(dev, async);

        if (async_error)
                goto Complete;

        /*
         * If a device configured to wake up the system from sleep states
         * has been suspended at run time and there's a resume request pending
         * for it, this is equivalent to the device signaling wakeup, so the
         * system suspend operation should be aborted.
         */
        if (pm_runtime_barrier(dev) && device_may_wakeup(dev))
                pm_wakeup_event(dev, 0);

        if (pm_wakeup_pending()) {
                async_error = -EBUSY;
                goto Complete;
        }

        if (dev->power.syscore)
                goto Complete;

        if (dev->power.direct_complete) {
                if (pm_runtime_status_suspended(dev)) {
                        pm_runtime_disable(dev);
                        if (pm_runtime_status_suspended(dev))
                                goto Complete;

                        pm_runtime_enable(dev);
                }
                dev->power.direct_complete = false;
        }

        dpm_watchdog_set(&wd, dev);
        device_lock(dev);

        if (dev->pm_domain) {
                info = "power domain ";
                callback = pm_op(&dev->pm_domain->ops, state);
                goto Run;
        }

        if (dev->type && dev->type->pm) {
                info = "type ";
                callback = pm_op(dev->type->pm, state);
                goto Run;
        }

        if (dev->class) {
                if (dev->class->pm) {
                        info = "class ";
                        callback = pm_op(dev->class->pm, state);
                        goto Run;
                } else if (dev->class->suspend) {
                        pm_dev_dbg(dev, state, "legacy class ");
                        error = legacy_suspend(dev, state, dev->class->suspend,
                                                "legacy class ");
                        goto End;
                }
        }

        if (dev->bus) {
                if (dev->bus->pm) {
                        info = "bus ";
                        callback = pm_op(dev->bus->pm, state);
                } else if (dev->bus->suspend) {
                        pm_dev_dbg(dev, state, "legacy bus ");
                        error = legacy_suspend(dev, state, dev->bus->suspend,
                                                "legacy bus ");
                        goto End;
                }
        }

 Run:
        if (!callback && dev->driver && dev->driver->pm) {
                info = "driver ";
                callback = pm_op(dev->driver->pm, state);
        }

        error = dpm_run_callback(callback, dev, state, info);

 End:
        if (!error) {
                struct device *parent = dev->parent;

                dev->power.is_suspended = true;
                if (parent) {
                        spin_lock_irq(&parent->power.lock);

                        dev->parent->power.direct_complete = false;
                        if (dev->power.wakeup_path
                            && !dev->parent->power.ignore_children)
                                dev->parent->power.wakeup_path = true;

                        spin_unlock_irq(&parent->power.lock);
                }
                dpm_clear_suppliers_direct_complete(dev);
        }

        device_unlock(dev);
        dpm_watchdog_clear(&wd);

 Complete:
        if (error)
                async_error = error;

        complete_all(&dev->power.completion);
        TRACE_SUSPEND(error);
        return error;
}

static void async_suspend(void *data, async_cookie_t cookie)
{
        struct device *dev = (struct device *)data;
        int error;

        error = __device_suspend(dev, pm_transition, true);
        if (error) {
                dpm_save_failed_dev(dev_name(dev));
                pm_dev_err(dev, pm_transition, " async", error);
        }

        put_device(dev);
}

static int device_suspend(struct device *dev)
{
        reinit_completion(&dev->power.completion);

        if (is_async(dev)) {
                get_device(dev);
                async_schedule(async_suspend, dev);
                return 0;
        }

        return __device_suspend(dev, pm_transition, false);
}

/**
 * dpm_suspend - Execute "suspend" callbacks for all non-sysdev devices.
 * @state: PM transition of the system being carried out.
 */
int dpm_suspend(pm_message_t state)
{
        ktime_t starttime = ktime_get();
        int error = 0;

        trace_suspend_resume(TPS("dpm_suspend"), state.event, true);
        might_sleep();

        cpufreq_suspend();

        mutex_lock(&dpm_list_mtx);
        pm_transition = state;
        async_error = 0;
        while (!list_empty(&dpm_prepared_list)) {
                struct device *dev = to_device(dpm_prepared_list.prev);

                get_device(dev);
                mutex_unlock(&dpm_list_mtx);

                error = device_suspend(dev);

                mutex_lock(&dpm_list_mtx);
                if (error) {
                        pm_dev_err(dev, state, "", error);
                        dpm_save_failed_dev(dev_name(dev));
                        put_device(dev);
                        break;
                }
                if (!list_empty(&dev->power.entry))
                        list_move(&dev->power.entry, &dpm_suspended_list);
                put_device(dev);
                if (async_error)
                        break;
        }
        mutex_unlock(&dpm_list_mtx);
        async_synchronize_full();
        if (!error)
                error = async_error;
        if (error) {
                suspend_stats.failed_suspend++;
                dpm_save_failed_step(SUSPEND_SUSPEND);
        } else
                dpm_show_time(starttime, state, NULL);
        trace_suspend_resume(TPS("dpm_suspend"), state.event, false);
        return error;
}

/**
 * device_prepare - Prepare a device for system power transition.
 * @dev: Device to handle.
 * @state: PM transition of the system being carried out.
 *
 * Execute the ->prepare() callback(s) for given device.  No new children of the
 * device may be registered after this function has returned.
 */
static int device_prepare(struct device *dev, pm_message_t state)
{
        int (*callback)(struct device *) = NULL;
        int ret = 0;

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

        /*
         * If a device's parent goes into runtime suspend at the wrong time,
         * it won't be possible to resume the device.  To prevent this we
         * block runtime suspend here, during the prepare phase, and allow
         * it again during the complete phase.
         */
        pm_runtime_get_noresume(dev);

        device_lock(dev);

        dev->power.wakeup_path = device_may_wakeup(dev);

        if (dev->power.no_pm_callbacks) {
                ret = 1;        /* Let device go direct_complete */
                goto unlock;
        }

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

        if (!callback && dev->driver && dev->driver->pm)
                callback = dev->driver->pm->prepare;

        if (callback)
                ret = callback(dev);

unlock:
        device_unlock(dev);

        if (ret < 0) {
                suspend_report_result(callback, ret);
                pm_runtime_put(dev);
                return ret;
        }
        /*
         * A positive return value from ->prepare() means "this device appears
         * to be runtime-suspended and its state is fine, so if it really is
         * runtime-suspended, you can leave it in that state provided that you
         * will do the same thing with all of its descendants".  This only
         * applies to suspend transitions, however.
         */
        spin_lock_irq(&dev->power.lock);
        dev->power.direct_complete = ret > 0 && state.event == PM_EVENT_SUSPEND;
        spin_unlock_irq(&dev->power.lock);
        return 0;
}

/**
 * dpm_prepare - Prepare all non-sysdev devices for a system PM transition.
 * @state: PM transition of the system being carried out.
 *
 * Execute the ->prepare() callback(s) for all devices.
 */
int dpm_prepare(pm_message_t state)
{
        int error = 0;

        trace_suspend_resume(TPS("dpm_prepare"), state.event, true);
        might_sleep();

        /*
         * Give a chance for the known devices to complete their probes, before
         * disable probing of devices. This sync point is important at least
         * at boot time + hibernation restore.
         */
        wait_for_device_probe();
        /*
         * It is unsafe if probing of devices will happen during suspend or
         * hibernation and system behavior will be unpredictable in this case.
         * So, let's prohibit device's probing here and defer their probes
         * instead. The normal behavior will be restored in dpm_complete().
         */
        device_block_probing();

        mutex_lock(&dpm_list_mtx);
        while (!list_empty(&dpm_list)) {
                struct device *dev = to_device(dpm_list.next);

                get_device(dev);
                mutex_unlock(&dpm_list_mtx);

                trace_device_pm_callback_start(dev, "", state.event);
                error = device_prepare(dev, state);
                trace_device_pm_callback_end(dev, error);

                mutex_lock(&dpm_list_mtx);
                if (error) {
                        if (error == -EAGAIN) {
                                put_device(dev);
                                error = 0;
                                continue;
                        }
                        printk(KERN_INFO "PM: Device %s not prepared "
                                "for power transition: code %d\n",
                                dev_name(dev), error);
                        put_device(dev);
                        break;
                }
                dev->power.is_prepared = true;
                if (!list_empty(&dev->power.entry))
                        list_move_tail(&dev->power.entry, &dpm_prepared_list);
                put_device(dev);
        }
        mutex_unlock(&dpm_list_mtx);
        trace_suspend_resume(TPS("dpm_prepare"), state.event, false);
        return error;
}

/**
 * dpm_suspend_start - Prepare devices for PM transition and suspend them.
 * @state: PM transition of the system being carried out.
 *
 * Prepare all non-sysdev devices for system PM transition and execute "suspend"
 * callbacks for them.
 */
int dpm_suspend_start(pm_message_t state)
{
        int error;

        error = dpm_prepare(state);
        if (error) {
                suspend_stats.failed_prepare++;
                dpm_save_failed_step(SUSPEND_PREPARE);
        } else
                error = dpm_suspend(state);
        return error;
}
EXPORT_SYMBOL_GPL(dpm_suspend_start);

void __suspend_report_result(const char *function, void *fn, int ret)
{
        if (ret)
                printk(KERN_ERR "%s(): %pF returns %d\n", function, fn, ret);
}
EXPORT_SYMBOL_GPL(__suspend_report_result);

/**
 * device_pm_wait_for_dev - Wait for suspend/resume of a device to complete.
 * @dev: Device to wait for.
 * @subordinate: Device that needs to wait for @dev.
 */
int device_pm_wait_for_dev(struct device *subordinate, struct device *dev)
{
        dpm_wait(dev, subordinate->power.async_suspend);
        return async_error;
}
EXPORT_SYMBOL_GPL(device_pm_wait_for_dev);

/**
 * dpm_for_each_dev - device iterator.
 * @data: data for the callback.
 * @fn: function to be called for each device.
 *
 * Iterate over devices in dpm_list, and call @fn for each device,
 * passing it @data.
 */
void dpm_for_each_dev(void *data, void (*fn)(struct device *, void *))
{
        struct device *dev;

        if (!fn)
                return;

        device_pm_lock();
        list_for_each_entry(dev, &dpm_list, power.entry)
                fn(dev, data);
        device_pm_unlock();
}
EXPORT_SYMBOL_GPL(dpm_for_each_dev);

static bool pm_ops_is_empty(const struct dev_pm_ops *ops)
{
        if (!ops)
                return true;

        return !ops->prepare &&
               !ops->suspend &&
               !ops->suspend_late &&
               !ops->suspend_noirq &&
               !ops->resume_noirq &&
               !ops->resume_early &&
               !ops->resume &&
               !ops->complete;
}

void device_pm_check_callbacks(struct device *dev)
{
        spin_lock_irq(&dev->power.lock);
        dev->power.no_pm_callbacks =
                (!dev->bus || pm_ops_is_empty(dev->bus->pm)) &&
                (!dev->class || pm_ops_is_empty(dev->class->pm)) &&
                (!dev->type || pm_ops_is_empty(dev->type->pm)) &&
                (!dev->pm_domain || pm_ops_is_empty(&dev->pm_domain->ops)) &&
                (!dev->driver || pm_ops_is_empty(dev->driver->pm));
        spin_unlock_irq(&dev->power.lock);
}