zte's code,first commit

Change-Id: I9a04da59e459a9bc0d67f101f700d9d7dc8d681b
diff --git a/ap/os/linux/linux-3.4.x/drivers/base/power/domain.c b/ap/os/linux/linux-3.4.x/drivers/base/power/domain.c
new file mode 100644
index 0000000..83aa694
--- /dev/null
+++ b/ap/os/linux/linux-3.4.x/drivers/base/power/domain.c
@@ -0,0 +1,1815 @@
+/*
+ * drivers/base/power/domain.c - Common code related to device power domains.
+ *
+ * Copyright (C) 2011 Rafael J. Wysocki <rjw@sisk.pl>, Renesas Electronics Corp.
+ *
+ * This file is released under the GPLv2.
+ */
+
+#include <linux/init.h>
+#include <linux/kernel.h>
+#include <linux/io.h>
+#include <linux/pm_runtime.h>
+#include <linux/pm_domain.h>
+#include <linux/pm_qos.h>
+#include <linux/slab.h>
+#include <linux/err.h>
+#include <linux/sched.h>
+#include <linux/suspend.h>
+#include <linux/export.h>
+
+#define GENPD_DEV_CALLBACK(genpd, type, callback, dev)		\
+({								\
+	type (*__routine)(struct device *__d); 			\
+	type __ret = (type)0;					\
+								\
+	__routine = genpd->dev_ops.callback; 			\
+	if (__routine) {					\
+		__ret = __routine(dev); 			\
+	} else {						\
+		__routine = dev_gpd_data(dev)->ops.callback;	\
+		if (__routine) 					\
+			__ret = __routine(dev);			\
+	}							\
+	__ret;							\
+})
+
+#define GENPD_DEV_TIMED_CALLBACK(genpd, type, callback, dev, field, name)	\
+({										\
+	ktime_t __start = ktime_get();						\
+	type __retval = GENPD_DEV_CALLBACK(genpd, type, callback, dev);		\
+	s64 __elapsed = ktime_to_ns(ktime_sub(ktime_get(), __start));		\
+	struct gpd_timing_data *__td = &dev_gpd_data(dev)->td;			\
+	if (!__retval && __elapsed > __td->field) {				\
+		__td->field = __elapsed;					\
+		dev_warn(dev, name " latency exceeded, new value %lld ns\n",	\
+			__elapsed);						\
+		genpd->max_off_time_changed = true;				\
+		__td->constraint_changed = true;				\
+	}									\
+	__retval;								\
+})
+
+static LIST_HEAD(gpd_list);
+static DEFINE_MUTEX(gpd_list_lock);
+
+#ifdef CONFIG_PM
+
+struct generic_pm_domain *dev_to_genpd(struct device *dev)
+{
+	if (IS_ERR_OR_NULL(dev->pm_domain))
+		return ERR_PTR(-EINVAL);
+
+	return pd_to_genpd(dev->pm_domain);
+}
+
+static int genpd_stop_dev(struct generic_pm_domain *genpd, struct device *dev)
+{
+	return GENPD_DEV_TIMED_CALLBACK(genpd, int, stop, dev,
+					stop_latency_ns, "stop");
+}
+
+static int genpd_start_dev(struct generic_pm_domain *genpd, struct device *dev)
+{
+	return GENPD_DEV_TIMED_CALLBACK(genpd, int, start, dev,
+					start_latency_ns, "start");
+}
+
+static int genpd_save_dev(struct generic_pm_domain *genpd, struct device *dev)
+{
+	return GENPD_DEV_TIMED_CALLBACK(genpd, int, save_state, dev,
+					save_state_latency_ns, "state save");
+}
+
+static int genpd_restore_dev(struct generic_pm_domain *genpd, struct device *dev)
+{
+	return GENPD_DEV_TIMED_CALLBACK(genpd, int, restore_state, dev,
+					restore_state_latency_ns,
+					"state restore");
+}
+
+static bool genpd_sd_counter_dec(struct generic_pm_domain *genpd)
+{
+	bool ret = false;
+
+	if (!WARN_ON(atomic_read(&genpd->sd_count) == 0))
+		ret = !!atomic_dec_and_test(&genpd->sd_count);
+
+	return ret;
+}
+
+static void genpd_sd_counter_inc(struct generic_pm_domain *genpd)
+{
+	atomic_inc(&genpd->sd_count);
+	smp_mb__after_atomic_inc();
+}
+
+static void genpd_acquire_lock(struct generic_pm_domain *genpd)
+{
+	DEFINE_WAIT(wait);
+
+	mutex_lock(&genpd->lock);
+	/*
+	 * Wait for the domain to transition into either the active,
+	 * or the power off state.
+	 */
+	for (;;) {
+		prepare_to_wait(&genpd->status_wait_queue, &wait,
+				TASK_UNINTERRUPTIBLE);
+		if (genpd->status == GPD_STATE_ACTIVE
+		    || genpd->status == GPD_STATE_POWER_OFF)
+			break;
+		mutex_unlock(&genpd->lock);
+
+		schedule();
+
+		mutex_lock(&genpd->lock);
+	}
+	finish_wait(&genpd->status_wait_queue, &wait);
+}
+
+static void genpd_release_lock(struct generic_pm_domain *genpd)
+{
+	mutex_unlock(&genpd->lock);
+}
+
+static void genpd_set_active(struct generic_pm_domain *genpd)
+{
+	if (genpd->resume_count == 0)
+		genpd->status = GPD_STATE_ACTIVE;
+}
+
+/**
+ * __pm_genpd_poweron - Restore power to a given PM domain and its masters.
+ * @genpd: PM domain to power up.
+ *
+ * Restore power to @genpd and all of its masters so that it is possible to
+ * resume a device belonging to it.
+ */
+int __pm_genpd_poweron(struct generic_pm_domain *genpd)
+	__releases(&genpd->lock) __acquires(&genpd->lock)
+{
+	struct gpd_link *link;
+	DEFINE_WAIT(wait);
+	int ret = 0;
+
+	/* If the domain's master is being waited for, we have to wait too. */
+	for (;;) {
+		prepare_to_wait(&genpd->status_wait_queue, &wait,
+				TASK_UNINTERRUPTIBLE);
+		if (genpd->status != GPD_STATE_WAIT_MASTER)
+			break;
+		mutex_unlock(&genpd->lock);
+
+		schedule();
+
+		mutex_lock(&genpd->lock);
+	}
+	finish_wait(&genpd->status_wait_queue, &wait);
+
+	if (genpd->status == GPD_STATE_ACTIVE
+	    || (genpd->prepared_count > 0 && genpd->suspend_power_off))
+		return 0;
+
+	if (genpd->status != GPD_STATE_POWER_OFF) {
+		genpd_set_active(genpd);
+		return 0;
+	}
+
+	/*
+	 * The list is guaranteed not to change while the loop below is being
+	 * executed, unless one of the masters' .power_on() callbacks fiddles
+	 * with it.
+	 */
+	list_for_each_entry(link, &genpd->slave_links, slave_node) {
+		genpd_sd_counter_inc(link->master);
+		genpd->status = GPD_STATE_WAIT_MASTER;
+
+		mutex_unlock(&genpd->lock);
+
+		ret = pm_genpd_poweron(link->master);
+
+		mutex_lock(&genpd->lock);
+
+		/*
+		 * The "wait for parent" status is guaranteed not to change
+		 * while the master is powering on.
+		 */
+		genpd->status = GPD_STATE_POWER_OFF;
+		wake_up_all(&genpd->status_wait_queue);
+		if (ret) {
+			genpd_sd_counter_dec(link->master);
+			goto err;
+		}
+	}
+
+	if (genpd->power_on) {
+		ktime_t time_start = ktime_get();
+		s64 elapsed_ns;
+
+		ret = genpd->power_on(genpd);
+		if (ret)
+			goto err;
+
+		elapsed_ns = ktime_to_ns(ktime_sub(ktime_get(), time_start));
+		if (elapsed_ns > genpd->power_on_latency_ns) {
+			genpd->power_on_latency_ns = elapsed_ns;
+			genpd->max_off_time_changed = true;
+			if (genpd->name)
+				pr_warning("%s: Power-on latency exceeded, "
+					"new value %lld ns\n", genpd->name,
+					elapsed_ns);
+		}
+	}
+
+	genpd_set_active(genpd);
+
+	return 0;
+
+ err:
+	list_for_each_entry_continue_reverse(link, &genpd->slave_links, slave_node)
+		genpd_sd_counter_dec(link->master);
+
+	return ret;
+}
+
+/**
+ * pm_genpd_poweron - Restore power to a given PM domain and its masters.
+ * @genpd: PM domain to power up.
+ */
+int pm_genpd_poweron(struct generic_pm_domain *genpd)
+{
+	int ret;
+
+	mutex_lock(&genpd->lock);
+	ret = __pm_genpd_poweron(genpd);
+	mutex_unlock(&genpd->lock);
+	return ret;
+}
+
+#endif /* CONFIG_PM */
+
+#ifdef CONFIG_PM_RUNTIME
+
+static int genpd_dev_pm_qos_notifier(struct notifier_block *nb,
+				     unsigned long val, void *ptr)
+{
+	struct generic_pm_domain_data *gpd_data;
+	struct device *dev;
+
+	gpd_data = container_of(nb, struct generic_pm_domain_data, nb);
+
+	mutex_lock(&gpd_data->lock);
+	dev = gpd_data->base.dev;
+	if (!dev) {
+		mutex_unlock(&gpd_data->lock);
+		return NOTIFY_DONE;
+	}
+	mutex_unlock(&gpd_data->lock);
+
+	for (;;) {
+		struct generic_pm_domain *genpd;
+		struct pm_domain_data *pdd;
+
+		spin_lock_irq(&dev->power.lock);
+
+		pdd = dev->power.subsys_data ?
+				dev->power.subsys_data->domain_data : NULL;
+		if (pdd) {
+			to_gpd_data(pdd)->td.constraint_changed = true;
+			genpd = dev_to_genpd(dev);
+		} else {
+			genpd = ERR_PTR(-ENODATA);
+		}
+
+		spin_unlock_irq(&dev->power.lock);
+
+		if (!IS_ERR(genpd)) {
+			mutex_lock(&genpd->lock);
+			genpd->max_off_time_changed = true;
+			mutex_unlock(&genpd->lock);
+		}
+
+		dev = dev->parent;
+		if (!dev || dev->power.ignore_children)
+			break;
+	}
+
+	return NOTIFY_DONE;
+}
+
+/**
+ * __pm_genpd_save_device - Save the pre-suspend state of a device.
+ * @pdd: Domain data of the device to save the state of.
+ * @genpd: PM domain the device belongs to.
+ */
+static int __pm_genpd_save_device(struct pm_domain_data *pdd,
+				  struct generic_pm_domain *genpd)
+	__releases(&genpd->lock) __acquires(&genpd->lock)
+{
+	struct generic_pm_domain_data *gpd_data = to_gpd_data(pdd);
+	struct device *dev = pdd->dev;
+	int ret = 0;
+
+	if (gpd_data->need_restore)
+		return 0;
+
+	mutex_unlock(&genpd->lock);
+
+	genpd_start_dev(genpd, dev);
+	ret = genpd_save_dev(genpd, dev);
+	genpd_stop_dev(genpd, dev);
+
+	mutex_lock(&genpd->lock);
+
+	if (!ret)
+		gpd_data->need_restore = true;
+
+	return ret;
+}
+
+/**
+ * __pm_genpd_restore_device - Restore the pre-suspend state of a device.
+ * @pdd: Domain data of the device to restore the state of.
+ * @genpd: PM domain the device belongs to.
+ */
+static void __pm_genpd_restore_device(struct pm_domain_data *pdd,
+				      struct generic_pm_domain *genpd)
+	__releases(&genpd->lock) __acquires(&genpd->lock)
+{
+	struct generic_pm_domain_data *gpd_data = to_gpd_data(pdd);
+	struct device *dev = pdd->dev;
+
+	if (!gpd_data->need_restore)
+		return;
+
+	mutex_unlock(&genpd->lock);
+
+	genpd_start_dev(genpd, dev);
+	genpd_restore_dev(genpd, dev);
+	genpd_stop_dev(genpd, dev);
+
+	mutex_lock(&genpd->lock);
+
+	gpd_data->need_restore = false;
+}
+
+/**
+ * genpd_abort_poweroff - Check if a PM domain power off should be aborted.
+ * @genpd: PM domain to check.
+ *
+ * Return true if a PM domain's status changed to GPD_STATE_ACTIVE during
+ * a "power off" operation, which means that a "power on" has occured in the
+ * meantime, or if its resume_count field is different from zero, which means
+ * that one of its devices has been resumed in the meantime.
+ */
+static bool genpd_abort_poweroff(struct generic_pm_domain *genpd)
+{
+	return genpd->status == GPD_STATE_WAIT_MASTER
+		|| genpd->status == GPD_STATE_ACTIVE || genpd->resume_count > 0;
+}
+
+/**
+ * genpd_queue_power_off_work - Queue up the execution of pm_genpd_poweroff().
+ * @genpd: PM domait to power off.
+ *
+ * Queue up the execution of pm_genpd_poweroff() unless it's already been done
+ * before.
+ */
+void genpd_queue_power_off_work(struct generic_pm_domain *genpd)
+{
+	if (!work_pending(&genpd->power_off_work))
+		queue_work(pm_wq, &genpd->power_off_work);
+}
+
+/**
+ * pm_genpd_poweroff - Remove power from a given PM domain.
+ * @genpd: PM domain to power down.
+ *
+ * If all of the @genpd's devices have been suspended and all of its subdomains
+ * have been powered down, run the runtime suspend callbacks provided by all of
+ * the @genpd's devices' drivers and remove power from @genpd.
+ */
+static int pm_genpd_poweroff(struct generic_pm_domain *genpd)
+	__releases(&genpd->lock) __acquires(&genpd->lock)
+{
+	struct pm_domain_data *pdd;
+	struct gpd_link *link;
+	unsigned int not_suspended;
+	int ret = 0;
+
+ start:
+	/*
+	 * Do not try to power off the domain in the following situations:
+	 * (1) The domain is already in the "power off" state.
+	 * (2) The domain is waiting for its master to power up.
+	 * (3) One of the domain's devices is being resumed right now.
+	 * (4) System suspend is in progress.
+	 */
+	if (genpd->status == GPD_STATE_POWER_OFF
+	    || genpd->status == GPD_STATE_WAIT_MASTER
+	    || genpd->resume_count > 0 || genpd->prepared_count > 0)
+		return 0;
+
+	if (atomic_read(&genpd->sd_count) > 0)
+		return -EBUSY;
+
+	not_suspended = 0;
+	list_for_each_entry(pdd, &genpd->dev_list, list_node)
+		if (pdd->dev->driver && (!pm_runtime_suspended(pdd->dev)
+		    || pdd->dev->power.irq_safe || to_gpd_data(pdd)->always_on))
+			not_suspended++;
+
+	if (not_suspended > genpd->in_progress)
+		return -EBUSY;
+
+	if (genpd->poweroff_task) {
+		/*
+		 * Another instance of pm_genpd_poweroff() is executing
+		 * callbacks, so tell it to start over and return.
+		 */
+		genpd->status = GPD_STATE_REPEAT;
+		return 0;
+	}
+
+	if (genpd->gov && genpd->gov->power_down_ok) {
+		if (!genpd->gov->power_down_ok(&genpd->domain))
+			return -EAGAIN;
+	}
+
+	genpd->status = GPD_STATE_BUSY;
+	genpd->poweroff_task = current;
+
+	list_for_each_entry_reverse(pdd, &genpd->dev_list, list_node) {
+		ret = atomic_read(&genpd->sd_count) == 0 ?
+			__pm_genpd_save_device(pdd, genpd) : -EBUSY;
+
+		if (genpd_abort_poweroff(genpd))
+			goto out;
+
+		if (ret) {
+			genpd_set_active(genpd);
+			goto out;
+		}
+
+		if (genpd->status == GPD_STATE_REPEAT) {
+			genpd->poweroff_task = NULL;
+			goto start;
+		}
+	}
+
+	if (genpd->power_off) {
+		ktime_t time_start;
+		s64 elapsed_ns;
+
+		if (atomic_read(&genpd->sd_count) > 0) {
+			ret = -EBUSY;
+			goto out;
+		}
+
+		time_start = ktime_get();
+
+		/*
+		 * If sd_count > 0 at this point, one of the subdomains hasn't
+		 * managed to call pm_genpd_poweron() for the master yet after
+		 * incrementing it.  In that case pm_genpd_poweron() will wait
+		 * for us to drop the lock, so we can call .power_off() and let
+		 * the pm_genpd_poweron() restore power for us (this shouldn't
+		 * happen very often).
+		 */
+		ret = genpd->power_off(genpd);
+		if (ret == -EBUSY) {
+			genpd_set_active(genpd);
+			goto out;
+		}
+
+		elapsed_ns = ktime_to_ns(ktime_sub(ktime_get(), time_start));
+		if (elapsed_ns > genpd->power_off_latency_ns) {
+			genpd->power_off_latency_ns = elapsed_ns;
+			genpd->max_off_time_changed = true;
+			if (genpd->name)
+				pr_warning("%s: Power-off latency exceeded, "
+					"new value %lld ns\n", genpd->name,
+					elapsed_ns);
+		}
+	}
+
+	genpd->status = GPD_STATE_POWER_OFF;
+
+	list_for_each_entry(link, &genpd->slave_links, slave_node) {
+		genpd_sd_counter_dec(link->master);
+		genpd_queue_power_off_work(link->master);
+	}
+
+ out:
+	genpd->poweroff_task = NULL;
+	wake_up_all(&genpd->status_wait_queue);
+	return ret;
+}
+
+/**
+ * genpd_power_off_work_fn - Power off PM domain whose subdomain count is 0.
+ * @work: Work structure used for scheduling the execution of this function.
+ */
+static void genpd_power_off_work_fn(struct work_struct *work)
+{
+	struct generic_pm_domain *genpd;
+
+	genpd = container_of(work, struct generic_pm_domain, power_off_work);
+
+	genpd_acquire_lock(genpd);
+	pm_genpd_poweroff(genpd);
+	genpd_release_lock(genpd);
+}
+
+/**
+ * pm_genpd_runtime_suspend - Suspend a device belonging to I/O PM domain.
+ * @dev: Device to suspend.
+ *
+ * Carry out a runtime suspend of a device under the assumption that its
+ * pm_domain field points to the domain member of an object of type
+ * struct generic_pm_domain representing a PM domain consisting of I/O devices.
+ */
+static int pm_genpd_runtime_suspend(struct device *dev)
+{
+	struct generic_pm_domain *genpd;
+	bool (*stop_ok)(struct device *__dev);
+	int ret;
+
+	dev_dbg(dev, "%s()\n", __func__);
+
+	genpd = dev_to_genpd(dev);
+	if (IS_ERR(genpd))
+		return -EINVAL;
+
+	might_sleep_if(!genpd->dev_irq_safe);
+
+	if (dev_gpd_data(dev)->always_on)
+		return -EBUSY;
+
+	stop_ok = genpd->gov ? genpd->gov->stop_ok : NULL;
+	if (stop_ok && !stop_ok(dev))
+		return -EBUSY;
+
+	ret = genpd_stop_dev(genpd, dev);
+	if (ret)
+		return ret;
+
+	/*
+	 * If power.irq_safe is set, this routine will be run with interrupts
+	 * off, so it can't use mutexes.
+	 */
+	if (dev->power.irq_safe)
+		return 0;
+
+	mutex_lock(&genpd->lock);
+	genpd->in_progress++;
+	pm_genpd_poweroff(genpd);
+	genpd->in_progress--;
+	mutex_unlock(&genpd->lock);
+
+	return 0;
+}
+
+/**
+ * pm_genpd_runtime_resume - Resume a device belonging to I/O PM domain.
+ * @dev: Device to resume.
+ *
+ * Carry out a runtime resume of a device under the assumption that its
+ * pm_domain field points to the domain member of an object of type
+ * struct generic_pm_domain representing a PM domain consisting of I/O devices.
+ */
+static int pm_genpd_runtime_resume(struct device *dev)
+{
+	struct generic_pm_domain *genpd;
+	DEFINE_WAIT(wait);
+	int ret;
+
+	dev_dbg(dev, "%s()\n", __func__);
+
+	genpd = dev_to_genpd(dev);
+	if (IS_ERR(genpd))
+		return -EINVAL;
+
+	might_sleep_if(!genpd->dev_irq_safe);
+
+	/* If power.irq_safe, the PM domain is never powered off. */
+	if (dev->power.irq_safe)
+		goto out;
+
+	mutex_lock(&genpd->lock);
+	ret = __pm_genpd_poweron(genpd);
+	if (ret) {
+		mutex_unlock(&genpd->lock);
+		return ret;
+	}
+	genpd->status = GPD_STATE_BUSY;
+	genpd->resume_count++;
+	for (;;) {
+		prepare_to_wait(&genpd->status_wait_queue, &wait,
+				TASK_UNINTERRUPTIBLE);
+		/*
+		 * If current is the powering off task, we have been called
+		 * reentrantly from one of the device callbacks, so we should
+		 * not wait.
+		 */
+		if (!genpd->poweroff_task || genpd->poweroff_task == current)
+			break;
+		mutex_unlock(&genpd->lock);
+
+		schedule();
+
+		mutex_lock(&genpd->lock);
+	}
+	finish_wait(&genpd->status_wait_queue, &wait);
+	__pm_genpd_restore_device(dev->power.subsys_data->domain_data, genpd);
+	genpd->resume_count--;
+	genpd_set_active(genpd);
+	wake_up_all(&genpd->status_wait_queue);
+	mutex_unlock(&genpd->lock);
+
+ out:
+	genpd_start_dev(genpd, dev);
+
+	return 0;
+}
+
+/**
+ * pm_genpd_poweroff_unused - Power off all PM domains with no devices in use.
+ */
+void pm_genpd_poweroff_unused(void)
+{
+	struct generic_pm_domain *genpd;
+
+	mutex_lock(&gpd_list_lock);
+
+	list_for_each_entry(genpd, &gpd_list, gpd_list_node)
+		genpd_queue_power_off_work(genpd);
+
+	mutex_unlock(&gpd_list_lock);
+}
+
+#else
+
+static inline int genpd_dev_pm_qos_notifier(struct notifier_block *nb,
+					    unsigned long val, void *ptr)
+{
+	return NOTIFY_DONE;
+}
+
+static inline void genpd_power_off_work_fn(struct work_struct *work) {}
+
+#define pm_genpd_runtime_suspend	NULL
+#define pm_genpd_runtime_resume		NULL
+
+#endif /* CONFIG_PM_RUNTIME */
+
+#ifdef CONFIG_PM_SLEEP
+
+static bool genpd_dev_active_wakeup(struct generic_pm_domain *genpd,
+				    struct device *dev)
+{
+	return GENPD_DEV_CALLBACK(genpd, bool, active_wakeup, dev);
+}
+
+static int genpd_suspend_dev(struct generic_pm_domain *genpd, struct device *dev)
+{
+	return GENPD_DEV_CALLBACK(genpd, int, suspend, dev);
+}
+
+static int genpd_suspend_late(struct generic_pm_domain *genpd, struct device *dev)
+{
+	return GENPD_DEV_CALLBACK(genpd, int, suspend_late, dev);
+}
+
+static int genpd_resume_early(struct generic_pm_domain *genpd, struct device *dev)
+{
+	return GENPD_DEV_CALLBACK(genpd, int, resume_early, dev);
+}
+
+static int genpd_resume_dev(struct generic_pm_domain *genpd, struct device *dev)
+{
+	return GENPD_DEV_CALLBACK(genpd, int, resume, dev);
+}
+
+static int genpd_freeze_dev(struct generic_pm_domain *genpd, struct device *dev)
+{
+	return GENPD_DEV_CALLBACK(genpd, int, freeze, dev);
+}
+
+static int genpd_freeze_late(struct generic_pm_domain *genpd, struct device *dev)
+{
+	return GENPD_DEV_CALLBACK(genpd, int, freeze_late, dev);
+}
+
+static int genpd_thaw_early(struct generic_pm_domain *genpd, struct device *dev)
+{
+	return GENPD_DEV_CALLBACK(genpd, int, thaw_early, dev);
+}
+
+static int genpd_thaw_dev(struct generic_pm_domain *genpd, struct device *dev)
+{
+	return GENPD_DEV_CALLBACK(genpd, int, thaw, dev);
+}
+
+/**
+ * pm_genpd_sync_poweroff - Synchronously power off a PM domain and its masters.
+ * @genpd: PM domain to power off, if possible.
+ *
+ * Check if the given PM domain can be powered off (during system suspend or
+ * hibernation) and do that if so.  Also, in that case propagate to its masters.
+ *
+ * This function is only called in "noirq" stages of system power transitions,
+ * so it need not acquire locks (all of the "noirq" callbacks are executed
+ * sequentially, so it is guaranteed that it will never run twice in parallel).
+ */
+static void pm_genpd_sync_poweroff(struct generic_pm_domain *genpd)
+{
+	struct gpd_link *link;
+
+	if (genpd->status == GPD_STATE_POWER_OFF)
+		return;
+
+	if (genpd->suspended_count != genpd->device_count
+	    || atomic_read(&genpd->sd_count) > 0)
+		return;
+
+	if (genpd->power_off)
+		genpd->power_off(genpd);
+
+	genpd->status = GPD_STATE_POWER_OFF;
+
+	list_for_each_entry(link, &genpd->slave_links, slave_node) {
+		genpd_sd_counter_dec(link->master);
+		pm_genpd_sync_poweroff(link->master);
+	}
+}
+
+/**
+ * resume_needed - Check whether to resume a device before system suspend.
+ * @dev: Device to check.
+ * @genpd: PM domain the device belongs to.
+ *
+ * There are two cases in which a device that can wake up the system from sleep
+ * states should be resumed by pm_genpd_prepare(): (1) if the device is enabled
+ * to wake up the system and it has to remain active for this purpose while the
+ * system is in the sleep state and (2) if the device is not enabled to wake up
+ * the system from sleep states and it generally doesn't generate wakeup signals
+ * by itself (those signals are generated on its behalf by other parts of the
+ * system).  In the latter case it may be necessary to reconfigure the device's
+ * wakeup settings during system suspend, because it may have been set up to
+ * signal remote wakeup from the system's working state as needed by runtime PM.
+ * Return 'true' in either of the above cases.
+ */
+static bool resume_needed(struct device *dev, struct generic_pm_domain *genpd)
+{
+	bool active_wakeup;
+
+	if (!device_can_wakeup(dev))
+		return false;
+
+	active_wakeup = genpd_dev_active_wakeup(genpd, dev);
+	return device_may_wakeup(dev) ? active_wakeup : !active_wakeup;
+}
+
+/**
+ * pm_genpd_prepare - Start power transition of a device in a PM domain.
+ * @dev: Device to start the transition of.
+ *
+ * Start a power transition of a device (during a system-wide power transition)
+ * under the assumption that its pm_domain field points to the domain member of
+ * an object of type struct generic_pm_domain representing a PM domain
+ * consisting of I/O devices.
+ */
+static int pm_genpd_prepare(struct device *dev)
+{
+	struct generic_pm_domain *genpd;
+	int ret;
+
+	dev_dbg(dev, "%s()\n", __func__);
+
+	genpd = dev_to_genpd(dev);
+	if (IS_ERR(genpd))
+		return -EINVAL;
+
+	/*
+	 * If a wakeup request is pending for the device, it should be woken up
+	 * at this point and a system wakeup event should be reported if it's
+	 * set up to wake up the system from sleep states.
+	 */
+	pm_runtime_get_noresume(dev);
+	if (pm_runtime_barrier(dev) && device_may_wakeup(dev))
+		pm_wakeup_event(dev, 0);
+
+	if (pm_wakeup_pending()) {
+		pm_runtime_put_sync(dev);
+		return -EBUSY;
+	}
+
+	if (resume_needed(dev, genpd))
+		pm_runtime_resume(dev);
+
+	genpd_acquire_lock(genpd);
+
+	if (genpd->prepared_count++ == 0) {
+		genpd->suspended_count = 0;
+		genpd->suspend_power_off = genpd->status == GPD_STATE_POWER_OFF;
+	}
+
+	genpd_release_lock(genpd);
+
+	if (genpd->suspend_power_off) {
+		pm_runtime_put_noidle(dev);
+		return 0;
+	}
+
+	/*
+	 * The PM domain must be in the GPD_STATE_ACTIVE state at this point,
+	 * so pm_genpd_poweron() will return immediately, but if the device
+	 * is suspended (e.g. it's been stopped by genpd_stop_dev()), we need
+	 * to make it operational.
+	 */
+	pm_runtime_resume(dev);
+	__pm_runtime_disable(dev, false);
+
+	ret = pm_generic_prepare(dev);
+	if (ret) {
+		mutex_lock(&genpd->lock);
+
+		if (--genpd->prepared_count == 0)
+			genpd->suspend_power_off = false;
+
+		mutex_unlock(&genpd->lock);
+		pm_runtime_enable(dev);
+	}
+
+	pm_runtime_put_sync(dev);
+	return ret;
+}
+
+/**
+ * pm_genpd_suspend - Suspend a device belonging to an I/O PM domain.
+ * @dev: Device to suspend.
+ *
+ * Suspend a device under the assumption that its pm_domain field points to the
+ * domain member of an object of type struct generic_pm_domain representing
+ * a PM domain consisting of I/O devices.
+ */
+static int pm_genpd_suspend(struct device *dev)
+{
+	struct generic_pm_domain *genpd;
+
+	dev_dbg(dev, "%s()\n", __func__);
+
+	genpd = dev_to_genpd(dev);
+	if (IS_ERR(genpd))
+		return -EINVAL;
+
+	return genpd->suspend_power_off ? 0 : genpd_suspend_dev(genpd, dev);
+}
+
+/**
+ * pm_genpd_suspend_late - Late suspend of a device from an I/O PM domain.
+ * @dev: Device to suspend.
+ *
+ * Carry out a late suspend of a device under the assumption that its
+ * pm_domain field points to the domain member of an object of type
+ * struct generic_pm_domain representing a PM domain consisting of I/O devices.
+ */
+static int pm_genpd_suspend_late(struct device *dev)
+{
+	struct generic_pm_domain *genpd;
+
+	dev_dbg(dev, "%s()\n", __func__);
+
+	genpd = dev_to_genpd(dev);
+	if (IS_ERR(genpd))
+		return -EINVAL;
+
+	return genpd->suspend_power_off ? 0 : genpd_suspend_late(genpd, dev);
+}
+
+/**
+ * pm_genpd_suspend_noirq - Completion of suspend of device in an I/O PM domain.
+ * @dev: Device to suspend.
+ *
+ * Stop the device and remove power from the domain if all devices in it have
+ * been stopped.
+ */
+static int pm_genpd_suspend_noirq(struct device *dev)
+{
+	struct generic_pm_domain *genpd;
+
+	dev_dbg(dev, "%s()\n", __func__);
+
+	genpd = dev_to_genpd(dev);
+	if (IS_ERR(genpd))
+		return -EINVAL;
+
+	if (genpd->suspend_power_off || dev_gpd_data(dev)->always_on
+	    || (dev->power.wakeup_path && genpd_dev_active_wakeup(genpd, dev)))
+		return 0;
+
+	genpd_stop_dev(genpd, dev);
+
+	/*
+	 * Since all of the "noirq" callbacks are executed sequentially, it is
+	 * guaranteed that this function will never run twice in parallel for
+	 * the same PM domain, so it is not necessary to use locking here.
+	 */
+	genpd->suspended_count++;
+	pm_genpd_sync_poweroff(genpd);
+
+	return 0;
+}
+
+/**
+ * pm_genpd_resume_noirq - Start of resume of device in an I/O PM domain.
+ * @dev: Device to resume.
+ *
+ * Restore power to the device's PM domain, if necessary, and start the device.
+ */
+static int pm_genpd_resume_noirq(struct device *dev)
+{
+	struct generic_pm_domain *genpd;
+
+	dev_dbg(dev, "%s()\n", __func__);
+
+	genpd = dev_to_genpd(dev);
+	if (IS_ERR(genpd))
+		return -EINVAL;
+
+	if (genpd->suspend_power_off || dev_gpd_data(dev)->always_on
+	    || (dev->power.wakeup_path && genpd_dev_active_wakeup(genpd, dev)))
+		return 0;
+
+	/*
+	 * Since all of the "noirq" callbacks are executed sequentially, it is
+	 * guaranteed that this function will never run twice in parallel for
+	 * the same PM domain, so it is not necessary to use locking here.
+	 */
+	pm_genpd_poweron(genpd);
+	genpd->suspended_count--;
+
+	return genpd_start_dev(genpd, dev);
+}
+
+/**
+ * pm_genpd_resume_early - Early resume of a device in an I/O PM domain.
+ * @dev: Device to resume.
+ *
+ * Carry out an early resume of a device under the assumption that its
+ * pm_domain field points to the domain member of an object of type
+ * struct generic_pm_domain representing a power domain consisting of I/O
+ * devices.
+ */
+static int pm_genpd_resume_early(struct device *dev)
+{
+	struct generic_pm_domain *genpd;
+
+	dev_dbg(dev, "%s()\n", __func__);
+
+	genpd = dev_to_genpd(dev);
+	if (IS_ERR(genpd))
+		return -EINVAL;
+
+	return genpd->suspend_power_off ? 0 : genpd_resume_early(genpd, dev);
+}
+
+/**
+ * pm_genpd_resume - Resume of device in an I/O PM domain.
+ * @dev: Device to resume.
+ *
+ * Resume a device under the assumption that its pm_domain field points to the
+ * domain member of an object of type struct generic_pm_domain representing
+ * a power domain consisting of I/O devices.
+ */
+static int pm_genpd_resume(struct device *dev)
+{
+	struct generic_pm_domain *genpd;
+
+	dev_dbg(dev, "%s()\n", __func__);
+
+	genpd = dev_to_genpd(dev);
+	if (IS_ERR(genpd))
+		return -EINVAL;
+
+	return genpd->suspend_power_off ? 0 : genpd_resume_dev(genpd, dev);
+}
+
+/**
+ * pm_genpd_freeze - Freezing a device in an I/O PM domain.
+ * @dev: Device to freeze.
+ *
+ * Freeze a device under the assumption that its pm_domain field points to the
+ * domain member of an object of type struct generic_pm_domain representing
+ * a power domain consisting of I/O devices.
+ */
+static int pm_genpd_freeze(struct device *dev)
+{
+	struct generic_pm_domain *genpd;
+
+	dev_dbg(dev, "%s()\n", __func__);
+
+	genpd = dev_to_genpd(dev);
+	if (IS_ERR(genpd))
+		return -EINVAL;
+
+	return genpd->suspend_power_off ? 0 : genpd_freeze_dev(genpd, dev);
+}
+
+/**
+ * pm_genpd_freeze_late - Late freeze of a device in an I/O PM domain.
+ * @dev: Device to freeze.
+ *
+ * Carry out a late freeze of a device under the assumption that its
+ * pm_domain field points to the domain member of an object of type
+ * struct generic_pm_domain representing a power domain consisting of I/O
+ * devices.
+ */
+static int pm_genpd_freeze_late(struct device *dev)
+{
+	struct generic_pm_domain *genpd;
+
+	dev_dbg(dev, "%s()\n", __func__);
+
+	genpd = dev_to_genpd(dev);
+	if (IS_ERR(genpd))
+		return -EINVAL;
+
+	return genpd->suspend_power_off ? 0 : genpd_freeze_late(genpd, dev);
+}
+
+/**
+ * pm_genpd_freeze_noirq - Completion of freezing a device in an I/O PM domain.
+ * @dev: Device to freeze.
+ *
+ * Carry out a late freeze of a device under the assumption that its
+ * pm_domain field points to the domain member of an object of type
+ * struct generic_pm_domain representing a power domain consisting of I/O
+ * devices.
+ */
+static int pm_genpd_freeze_noirq(struct device *dev)
+{
+	struct generic_pm_domain *genpd;
+
+	dev_dbg(dev, "%s()\n", __func__);
+
+	genpd = dev_to_genpd(dev);
+	if (IS_ERR(genpd))
+		return -EINVAL;
+
+	return genpd->suspend_power_off || dev_gpd_data(dev)->always_on ?
+		0 : genpd_stop_dev(genpd, dev);
+}
+
+/**
+ * pm_genpd_thaw_noirq - Early thaw of device in an I/O PM domain.
+ * @dev: Device to thaw.
+ *
+ * Start the device, unless power has been removed from the domain already
+ * before the system transition.
+ */
+static int pm_genpd_thaw_noirq(struct device *dev)
+{
+	struct generic_pm_domain *genpd;
+
+	dev_dbg(dev, "%s()\n", __func__);
+
+	genpd = dev_to_genpd(dev);
+	if (IS_ERR(genpd))
+		return -EINVAL;
+
+	return genpd->suspend_power_off || dev_gpd_data(dev)->always_on ?
+		0 : genpd_start_dev(genpd, dev);
+}
+
+/**
+ * pm_genpd_thaw_early - Early thaw of device in an I/O PM domain.
+ * @dev: Device to thaw.
+ *
+ * Carry out an early thaw of a device under the assumption that its
+ * pm_domain field points to the domain member of an object of type
+ * struct generic_pm_domain representing a power domain consisting of I/O
+ * devices.
+ */
+static int pm_genpd_thaw_early(struct device *dev)
+{
+	struct generic_pm_domain *genpd;
+
+	dev_dbg(dev, "%s()\n", __func__);
+
+	genpd = dev_to_genpd(dev);
+	if (IS_ERR(genpd))
+		return -EINVAL;
+
+	return genpd->suspend_power_off ? 0 : genpd_thaw_early(genpd, dev);
+}
+
+/**
+ * pm_genpd_thaw - Thaw a device belonging to an I/O power domain.
+ * @dev: Device to thaw.
+ *
+ * Thaw a device under the assumption that its pm_domain field points to the
+ * domain member of an object of type struct generic_pm_domain representing
+ * a power domain consisting of I/O devices.
+ */
+static int pm_genpd_thaw(struct device *dev)
+{
+	struct generic_pm_domain *genpd;
+
+	dev_dbg(dev, "%s()\n", __func__);
+
+	genpd = dev_to_genpd(dev);
+	if (IS_ERR(genpd))
+		return -EINVAL;
+
+	return genpd->suspend_power_off ? 0 : genpd_thaw_dev(genpd, dev);
+}
+
+/**
+ * pm_genpd_restore_noirq - Start of restore of device in an I/O PM domain.
+ * @dev: Device to resume.
+ *
+ * Make sure the domain will be in the same power state as before the
+ * hibernation the system is resuming from and start the device if necessary.
+ */
+static int pm_genpd_restore_noirq(struct device *dev)
+{
+	struct generic_pm_domain *genpd;
+
+	dev_dbg(dev, "%s()\n", __func__);
+
+	genpd = dev_to_genpd(dev);
+	if (IS_ERR(genpd))
+		return -EINVAL;
+
+	/*
+	 * Since all of the "noirq" callbacks are executed sequentially, it is
+	 * guaranteed that this function will never run twice in parallel for
+	 * the same PM domain, so it is not necessary to use locking here.
+	 *
+	 * At this point suspended_count == 0 means we are being run for the
+	 * first time for the given domain in the present cycle.
+	 */
+	if (genpd->suspended_count++ == 0) {
+		/*
+		 * The boot kernel might put the domain into arbitrary state,
+		 * so make it appear as powered off to pm_genpd_poweron(), so
+		 * that it tries to power it on in case it was really off.
+		 */
+		genpd->status = GPD_STATE_POWER_OFF;
+		if (genpd->suspend_power_off) {
+			/*
+			 * If the domain was off before the hibernation, make
+			 * sure it will be off going forward.
+			 */
+			if (genpd->power_off)
+				genpd->power_off(genpd);
+
+			return 0;
+		}
+	}
+
+	if (genpd->suspend_power_off)
+		return 0;
+
+	pm_genpd_poweron(genpd);
+
+	return dev_gpd_data(dev)->always_on ? 0 : genpd_start_dev(genpd, dev);
+}
+
+/**
+ * pm_genpd_complete - Complete power transition of a device in a power domain.
+ * @dev: Device to complete the transition of.
+ *
+ * Complete a power transition of a device (during a system-wide power
+ * transition) under the assumption that its pm_domain field points to the
+ * domain member of an object of type struct generic_pm_domain representing
+ * a power domain consisting of I/O devices.
+ */
+static void pm_genpd_complete(struct device *dev)
+{
+	struct generic_pm_domain *genpd;
+	bool run_complete;
+
+	dev_dbg(dev, "%s()\n", __func__);
+
+	genpd = dev_to_genpd(dev);
+	if (IS_ERR(genpd))
+		return;
+
+	mutex_lock(&genpd->lock);
+
+	run_complete = !genpd->suspend_power_off;
+	if (--genpd->prepared_count == 0)
+		genpd->suspend_power_off = false;
+
+	mutex_unlock(&genpd->lock);
+
+	if (run_complete) {
+		pm_generic_complete(dev);
+		pm_runtime_set_active(dev);
+		pm_runtime_enable(dev);
+		pm_runtime_idle(dev);
+	}
+}
+
+#else
+
+#define pm_genpd_prepare		NULL
+#define pm_genpd_suspend		NULL
+#define pm_genpd_suspend_late		NULL
+#define pm_genpd_suspend_noirq		NULL
+#define pm_genpd_resume_early		NULL
+#define pm_genpd_resume_noirq		NULL
+#define pm_genpd_resume			NULL
+#define pm_genpd_freeze			NULL
+#define pm_genpd_freeze_late		NULL
+#define pm_genpd_freeze_noirq		NULL
+#define pm_genpd_thaw_early		NULL
+#define pm_genpd_thaw_noirq		NULL
+#define pm_genpd_thaw			NULL
+#define pm_genpd_restore_noirq		NULL
+#define pm_genpd_complete		NULL
+
+#endif /* CONFIG_PM_SLEEP */
+
+/**
+ * __pm_genpd_add_device - Add a device to an I/O PM domain.
+ * @genpd: PM domain to add the device to.
+ * @dev: Device to be added.
+ * @td: Set of PM QoS timing parameters to attach to the device.
+ */
+int __pm_genpd_add_device(struct generic_pm_domain *genpd, struct device *dev,
+			  struct gpd_timing_data *td)
+{
+	struct generic_pm_domain_data *gpd_data;
+	struct pm_domain_data *pdd;
+	int ret = 0;
+
+	dev_dbg(dev, "%s()\n", __func__);
+
+	if (IS_ERR_OR_NULL(genpd) || IS_ERR_OR_NULL(dev))
+		return -EINVAL;
+
+	gpd_data = kzalloc(sizeof(*gpd_data), GFP_KERNEL);
+	if (!gpd_data)
+		return -ENOMEM;
+
+	mutex_init(&gpd_data->lock);
+	gpd_data->nb.notifier_call = genpd_dev_pm_qos_notifier;
+	dev_pm_qos_add_notifier(dev, &gpd_data->nb);
+
+	genpd_acquire_lock(genpd);
+
+	if (genpd->prepared_count > 0) {
+		ret = -EAGAIN;
+		goto out;
+	}
+
+	list_for_each_entry(pdd, &genpd->dev_list, list_node)
+		if (pdd->dev == dev) {
+			ret = -EINVAL;
+			goto out;
+		}
+
+	genpd->device_count++;
+	genpd->max_off_time_changed = true;
+
+	dev_pm_get_subsys_data(dev);
+
+	mutex_lock(&gpd_data->lock);
+	spin_lock_irq(&dev->power.lock);
+	dev->pm_domain = &genpd->domain;
+	dev->power.subsys_data->domain_data = &gpd_data->base;
+	gpd_data->base.dev = dev;
+	list_add_tail(&gpd_data->base.list_node, &genpd->dev_list);
+	gpd_data->need_restore = genpd->status == GPD_STATE_POWER_OFF;
+	if (td)
+		gpd_data->td = *td;
+
+	gpd_data->td.constraint_changed = true;
+	gpd_data->td.effective_constraint_ns = -1;
+	spin_unlock_irq(&dev->power.lock);
+	mutex_unlock(&gpd_data->lock);
+
+	genpd_release_lock(genpd);
+
+	return 0;
+
+ out:
+	genpd_release_lock(genpd);
+
+	dev_pm_qos_remove_notifier(dev, &gpd_data->nb);
+	kfree(gpd_data);
+	return ret;
+}
+
+/**
+ * __pm_genpd_of_add_device - Add a device to an I/O PM domain.
+ * @genpd_node: Device tree node pointer representing a PM domain to which the
+ *   the device is added to.
+ * @dev: Device to be added.
+ * @td: Set of PM QoS timing parameters to attach to the device.
+ */
+int __pm_genpd_of_add_device(struct device_node *genpd_node, struct device *dev,
+			     struct gpd_timing_data *td)
+{
+	struct generic_pm_domain *genpd = NULL, *gpd;
+
+	dev_dbg(dev, "%s()\n", __func__);
+
+	if (IS_ERR_OR_NULL(genpd_node) || IS_ERR_OR_NULL(dev))
+		return -EINVAL;
+
+	mutex_lock(&gpd_list_lock);
+	list_for_each_entry(gpd, &gpd_list, gpd_list_node) {
+		if (gpd->of_node == genpd_node) {
+			genpd = gpd;
+			break;
+		}
+	}
+	mutex_unlock(&gpd_list_lock);
+
+	if (!genpd)
+		return -EINVAL;
+
+	return __pm_genpd_add_device(genpd, dev, td);
+}
+
+/**
+ * pm_genpd_remove_device - Remove a device from an I/O PM domain.
+ * @genpd: PM domain to remove the device from.
+ * @dev: Device to be removed.
+ */
+int pm_genpd_remove_device(struct generic_pm_domain *genpd,
+			   struct device *dev)
+{
+	struct generic_pm_domain_data *gpd_data;
+	struct pm_domain_data *pdd;
+	int ret = 0;
+
+	dev_dbg(dev, "%s()\n", __func__);
+
+	if (IS_ERR_OR_NULL(genpd) || IS_ERR_OR_NULL(dev)
+	    ||  IS_ERR_OR_NULL(dev->pm_domain)
+	    ||  pd_to_genpd(dev->pm_domain) != genpd)
+		return -EINVAL;
+
+	genpd_acquire_lock(genpd);
+
+	if (genpd->prepared_count > 0) {
+		ret = -EAGAIN;
+		goto out;
+	}
+
+	genpd->device_count--;
+	genpd->max_off_time_changed = true;
+
+	spin_lock_irq(&dev->power.lock);
+	dev->pm_domain = NULL;
+	pdd = dev->power.subsys_data->domain_data;
+	list_del_init(&pdd->list_node);
+	dev->power.subsys_data->domain_data = NULL;
+	spin_unlock_irq(&dev->power.lock);
+
+	gpd_data = to_gpd_data(pdd);
+	mutex_lock(&gpd_data->lock);
+	pdd->dev = NULL;
+	mutex_unlock(&gpd_data->lock);
+
+	genpd_release_lock(genpd);
+
+	dev_pm_qos_remove_notifier(dev, &gpd_data->nb);
+	kfree(gpd_data);
+	dev_pm_put_subsys_data(dev);
+	return 0;
+
+ out:
+	genpd_release_lock(genpd);
+
+	return ret;
+}
+
+/**
+ * pm_genpd_dev_always_on - Set/unset the "always on" flag for a given device.
+ * @dev: Device to set/unset the flag for.
+ * @val: The new value of the device's "always on" flag.
+ */
+void pm_genpd_dev_always_on(struct device *dev, bool val)
+{
+	struct pm_subsys_data *psd;
+	unsigned long flags;
+
+	spin_lock_irqsave(&dev->power.lock, flags);
+
+	psd = dev_to_psd(dev);
+	if (psd && psd->domain_data)
+		to_gpd_data(psd->domain_data)->always_on = val;
+
+	spin_unlock_irqrestore(&dev->power.lock, flags);
+}
+EXPORT_SYMBOL_GPL(pm_genpd_dev_always_on);
+
+/**
+ * pm_genpd_dev_need_restore - Set/unset the device's "need restore" flag.
+ * @dev: Device to set/unset the flag for.
+ * @val: The new value of the device's "need restore" flag.
+ */
+void pm_genpd_dev_need_restore(struct device *dev, bool val)
+{
+	struct pm_subsys_data *psd;
+	unsigned long flags;
+
+	spin_lock_irqsave(&dev->power.lock, flags);
+
+	psd = dev_to_psd(dev);
+	if (psd && psd->domain_data)
+		to_gpd_data(psd->domain_data)->need_restore = val;
+
+	spin_unlock_irqrestore(&dev->power.lock, flags);
+}
+EXPORT_SYMBOL_GPL(pm_genpd_dev_need_restore);
+
+/**
+ * pm_genpd_add_subdomain - Add a subdomain to an I/O PM domain.
+ * @genpd: Master PM domain to add the subdomain to.
+ * @subdomain: Subdomain to be added.
+ */
+int pm_genpd_add_subdomain(struct generic_pm_domain *genpd,
+			   struct generic_pm_domain *subdomain)
+{
+	struct gpd_link *link;
+	int ret = 0;
+
+	if (IS_ERR_OR_NULL(genpd) || IS_ERR_OR_NULL(subdomain))
+		return -EINVAL;
+
+ start:
+	genpd_acquire_lock(genpd);
+	mutex_lock_nested(&subdomain->lock, SINGLE_DEPTH_NESTING);
+
+	if (subdomain->status != GPD_STATE_POWER_OFF
+	    && subdomain->status != GPD_STATE_ACTIVE) {
+		mutex_unlock(&subdomain->lock);
+		genpd_release_lock(genpd);
+		goto start;
+	}
+
+	if (genpd->status == GPD_STATE_POWER_OFF
+	    &&  subdomain->status != GPD_STATE_POWER_OFF) {
+		ret = -EINVAL;
+		goto out;
+	}
+
+	list_for_each_entry(link, &genpd->master_links, master_node) {
+		if (link->slave == subdomain && link->master == genpd) {
+			ret = -EINVAL;
+			goto out;
+		}
+	}
+
+	link = kzalloc(sizeof(*link), GFP_KERNEL);
+	if (!link) {
+		ret = -ENOMEM;
+		goto out;
+	}
+	link->master = genpd;
+	list_add_tail(&link->master_node, &genpd->master_links);
+	link->slave = subdomain;
+	list_add_tail(&link->slave_node, &subdomain->slave_links);
+	if (subdomain->status != GPD_STATE_POWER_OFF)
+		genpd_sd_counter_inc(genpd);
+
+ out:
+	mutex_unlock(&subdomain->lock);
+	genpd_release_lock(genpd);
+
+	return ret;
+}
+
+/**
+ * pm_genpd_remove_subdomain - Remove a subdomain from an I/O PM domain.
+ * @genpd: Master PM domain to remove the subdomain from.
+ * @subdomain: Subdomain to be removed.
+ */
+int pm_genpd_remove_subdomain(struct generic_pm_domain *genpd,
+			      struct generic_pm_domain *subdomain)
+{
+	struct gpd_link *link;
+	int ret = -EINVAL;
+
+	if (IS_ERR_OR_NULL(genpd) || IS_ERR_OR_NULL(subdomain))
+		return -EINVAL;
+
+ start:
+	genpd_acquire_lock(genpd);
+
+	list_for_each_entry(link, &genpd->master_links, master_node) {
+		if (link->slave != subdomain)
+			continue;
+
+		mutex_lock_nested(&subdomain->lock, SINGLE_DEPTH_NESTING);
+
+		if (subdomain->status != GPD_STATE_POWER_OFF
+		    && subdomain->status != GPD_STATE_ACTIVE) {
+			mutex_unlock(&subdomain->lock);
+			genpd_release_lock(genpd);
+			goto start;
+		}
+
+		list_del(&link->master_node);
+		list_del(&link->slave_node);
+		kfree(link);
+		if (subdomain->status != GPD_STATE_POWER_OFF)
+			genpd_sd_counter_dec(genpd);
+
+		mutex_unlock(&subdomain->lock);
+
+		ret = 0;
+		break;
+	}
+
+	genpd_release_lock(genpd);
+
+	return ret;
+}
+
+/**
+ * pm_genpd_add_callbacks - Add PM domain callbacks to a given device.
+ * @dev: Device to add the callbacks to.
+ * @ops: Set of callbacks to add.
+ * @td: Timing data to add to the device along with the callbacks (optional).
+ */
+int pm_genpd_add_callbacks(struct device *dev, struct gpd_dev_ops *ops,
+			   struct gpd_timing_data *td)
+{
+	struct pm_domain_data *pdd;
+	int ret = 0;
+
+	if (!(dev && dev->power.subsys_data && ops))
+		return -EINVAL;
+
+	pm_runtime_disable(dev);
+	device_pm_lock();
+
+	pdd = dev->power.subsys_data->domain_data;
+	if (pdd) {
+		struct generic_pm_domain_data *gpd_data = to_gpd_data(pdd);
+
+		gpd_data->ops = *ops;
+		if (td)
+			gpd_data->td = *td;
+	} else {
+		ret = -EINVAL;
+	}
+
+	device_pm_unlock();
+	pm_runtime_enable(dev);
+
+	return ret;
+}
+EXPORT_SYMBOL_GPL(pm_genpd_add_callbacks);
+
+/**
+ * __pm_genpd_remove_callbacks - Remove PM domain callbacks from a given device.
+ * @dev: Device to remove the callbacks from.
+ * @clear_td: If set, clear the device's timing data too.
+ */
+int __pm_genpd_remove_callbacks(struct device *dev, bool clear_td)
+{
+	struct pm_domain_data *pdd;
+	int ret = 0;
+
+	if (!(dev && dev->power.subsys_data))
+		return -EINVAL;
+
+	pm_runtime_disable(dev);
+	device_pm_lock();
+
+	pdd = dev->power.subsys_data->domain_data;
+	if (pdd) {
+		struct generic_pm_domain_data *gpd_data = to_gpd_data(pdd);
+
+		gpd_data->ops = (struct gpd_dev_ops){ 0 };
+		if (clear_td)
+			gpd_data->td = (struct gpd_timing_data){ 0 };
+	} else {
+		ret = -EINVAL;
+	}
+
+	device_pm_unlock();
+	pm_runtime_enable(dev);
+
+	return ret;
+}
+EXPORT_SYMBOL_GPL(__pm_genpd_remove_callbacks);
+
+/* Default device callbacks for generic PM domains. */
+
+/**
+ * pm_genpd_default_save_state - Default "save device state" for PM domians.
+ * @dev: Device to handle.
+ */
+static int pm_genpd_default_save_state(struct device *dev)
+{
+	int (*cb)(struct device *__dev);
+	struct device_driver *drv = dev->driver;
+
+	cb = dev_gpd_data(dev)->ops.save_state;
+	if (cb)
+		return cb(dev);
+
+	if (drv && drv->pm && drv->pm->runtime_suspend)
+		return drv->pm->runtime_suspend(dev);
+
+	return 0;
+}
+
+/**
+ * pm_genpd_default_restore_state - Default PM domians "restore device state".
+ * @dev: Device to handle.
+ */
+static int pm_genpd_default_restore_state(struct device *dev)
+{
+	int (*cb)(struct device *__dev);
+	struct device_driver *drv = dev->driver;
+
+	cb = dev_gpd_data(dev)->ops.restore_state;
+	if (cb)
+		return cb(dev);
+
+	if (drv && drv->pm && drv->pm->runtime_resume)
+		return drv->pm->runtime_resume(dev);
+
+	return 0;
+}
+
+#ifdef CONFIG_PM_SLEEP
+
+/**
+ * pm_genpd_default_suspend - Default "device suspend" for PM domians.
+ * @dev: Device to handle.
+ */
+static int pm_genpd_default_suspend(struct device *dev)
+{
+	int (*cb)(struct device *__dev) = dev_gpd_data(dev)->ops.suspend;
+
+	return cb ? cb(dev) : pm_generic_suspend(dev);
+}
+
+/**
+ * pm_genpd_default_suspend_late - Default "late device suspend" for PM domians.
+ * @dev: Device to handle.
+ */
+static int pm_genpd_default_suspend_late(struct device *dev)
+{
+	int (*cb)(struct device *__dev) = dev_gpd_data(dev)->ops.suspend_late;
+
+	return cb ? cb(dev) : pm_generic_suspend_late(dev);
+}
+
+/**
+ * pm_genpd_default_resume_early - Default "early device resume" for PM domians.
+ * @dev: Device to handle.
+ */
+static int pm_genpd_default_resume_early(struct device *dev)
+{
+	int (*cb)(struct device *__dev) = dev_gpd_data(dev)->ops.resume_early;
+
+	return cb ? cb(dev) : pm_generic_resume_early(dev);
+}
+
+/**
+ * pm_genpd_default_resume - Default "device resume" for PM domians.
+ * @dev: Device to handle.
+ */
+static int pm_genpd_default_resume(struct device *dev)
+{
+	int (*cb)(struct device *__dev) = dev_gpd_data(dev)->ops.resume;
+
+	return cb ? cb(dev) : pm_generic_resume(dev);
+}
+
+/**
+ * pm_genpd_default_freeze - Default "device freeze" for PM domians.
+ * @dev: Device to handle.
+ */
+static int pm_genpd_default_freeze(struct device *dev)
+{
+	int (*cb)(struct device *__dev) = dev_gpd_data(dev)->ops.freeze;
+
+	return cb ? cb(dev) : pm_generic_freeze(dev);
+}
+
+/**
+ * pm_genpd_default_freeze_late - Default "late device freeze" for PM domians.
+ * @dev: Device to handle.
+ */
+static int pm_genpd_default_freeze_late(struct device *dev)
+{
+	int (*cb)(struct device *__dev) = dev_gpd_data(dev)->ops.freeze_late;
+
+	return cb ? cb(dev) : pm_generic_freeze_late(dev);
+}
+
+/**
+ * pm_genpd_default_thaw_early - Default "early device thaw" for PM domians.
+ * @dev: Device to handle.
+ */
+static int pm_genpd_default_thaw_early(struct device *dev)
+{
+	int (*cb)(struct device *__dev) = dev_gpd_data(dev)->ops.thaw_early;
+
+	return cb ? cb(dev) : pm_generic_thaw_early(dev);
+}
+
+/**
+ * pm_genpd_default_thaw - Default "device thaw" for PM domians.
+ * @dev: Device to handle.
+ */
+static int pm_genpd_default_thaw(struct device *dev)
+{
+	int (*cb)(struct device *__dev) = dev_gpd_data(dev)->ops.thaw;
+
+	return cb ? cb(dev) : pm_generic_thaw(dev);
+}
+
+#else /* !CONFIG_PM_SLEEP */
+
+#define pm_genpd_default_suspend	NULL
+#define pm_genpd_default_suspend_late	NULL
+#define pm_genpd_default_resume_early	NULL
+#define pm_genpd_default_resume		NULL
+#define pm_genpd_default_freeze		NULL
+#define pm_genpd_default_freeze_late	NULL
+#define pm_genpd_default_thaw_early	NULL
+#define pm_genpd_default_thaw		NULL
+
+#endif /* !CONFIG_PM_SLEEP */
+
+/**
+ * pm_genpd_init - Initialize a generic I/O PM domain object.
+ * @genpd: PM domain object to initialize.
+ * @gov: PM domain governor to associate with the domain (may be NULL).
+ * @is_off: Initial value of the domain's power_is_off field.
+ */
+void pm_genpd_init(struct generic_pm_domain *genpd,
+		   struct dev_power_governor *gov, bool is_off)
+{
+	if (IS_ERR_OR_NULL(genpd))
+		return;
+
+	INIT_LIST_HEAD(&genpd->master_links);
+	INIT_LIST_HEAD(&genpd->slave_links);
+	INIT_LIST_HEAD(&genpd->dev_list);
+	mutex_init(&genpd->lock);
+	genpd->gov = gov;
+	INIT_WORK(&genpd->power_off_work, genpd_power_off_work_fn);
+	genpd->in_progress = 0;
+	atomic_set(&genpd->sd_count, 0);
+	genpd->status = is_off ? GPD_STATE_POWER_OFF : GPD_STATE_ACTIVE;
+	init_waitqueue_head(&genpd->status_wait_queue);
+	genpd->poweroff_task = NULL;
+	genpd->resume_count = 0;
+	genpd->device_count = 0;
+	genpd->max_off_time_ns = -1;
+	genpd->max_off_time_changed = true;
+	genpd->domain.ops.runtime_suspend = pm_genpd_runtime_suspend;
+	genpd->domain.ops.runtime_resume = pm_genpd_runtime_resume;
+	genpd->domain.ops.runtime_idle = pm_generic_runtime_idle;
+	genpd->domain.ops.prepare = pm_genpd_prepare;
+	genpd->domain.ops.suspend = pm_genpd_suspend;
+	genpd->domain.ops.suspend_late = pm_genpd_suspend_late;
+	genpd->domain.ops.suspend_noirq = pm_genpd_suspend_noirq;
+	genpd->domain.ops.resume_noirq = pm_genpd_resume_noirq;
+	genpd->domain.ops.resume_early = pm_genpd_resume_early;
+	genpd->domain.ops.resume = pm_genpd_resume;
+	genpd->domain.ops.freeze = pm_genpd_freeze;
+	genpd->domain.ops.freeze_late = pm_genpd_freeze_late;
+	genpd->domain.ops.freeze_noirq = pm_genpd_freeze_noirq;
+	genpd->domain.ops.thaw_noirq = pm_genpd_thaw_noirq;
+	genpd->domain.ops.thaw_early = pm_genpd_thaw_early;
+	genpd->domain.ops.thaw = pm_genpd_thaw;
+	genpd->domain.ops.poweroff = pm_genpd_suspend;
+	genpd->domain.ops.poweroff_late = pm_genpd_suspend_late;
+	genpd->domain.ops.poweroff_noirq = pm_genpd_suspend_noirq;
+	genpd->domain.ops.restore_noirq = pm_genpd_restore_noirq;
+	genpd->domain.ops.restore_early = pm_genpd_resume_early;
+	genpd->domain.ops.restore = pm_genpd_resume;
+	genpd->domain.ops.complete = pm_genpd_complete;
+	genpd->dev_ops.save_state = pm_genpd_default_save_state;
+	genpd->dev_ops.restore_state = pm_genpd_default_restore_state;
+	genpd->dev_ops.suspend = pm_genpd_default_suspend;
+	genpd->dev_ops.suspend_late = pm_genpd_default_suspend_late;
+	genpd->dev_ops.resume_early = pm_genpd_default_resume_early;
+	genpd->dev_ops.resume = pm_genpd_default_resume;
+	genpd->dev_ops.freeze = pm_genpd_default_freeze;
+	genpd->dev_ops.freeze_late = pm_genpd_default_freeze_late;
+	genpd->dev_ops.thaw_early = pm_genpd_default_thaw_early;
+	genpd->dev_ops.thaw = pm_genpd_default_thaw;
+	mutex_lock(&gpd_list_lock);
+	list_add(&genpd->gpd_list_node, &gpd_list);
+	mutex_unlock(&gpd_list_lock);
+}