diff mbox

[RFC,1/2] PM / Runtime: Support for generic I/O power domains

Message ID 201104290154.56145.rjw@sisk.pl (mailing list archive)
State Superseded
Headers show

Commit Message

Rafael Wysocki April 28, 2011, 11:54 p.m. UTC
From: Rafael J. Wysocki <rjw@sisk.pl>

Introcude common headers, helper functions and callbacks allowing
platforms to use simple generic power domains for runtime power
management.

Introduce struct generic_power_domain to be used for representing
power domains that each contain a number of devices and may be
master domains or subdomains with respect to other power domains.
Among other things, this structure includes callbacks to be
provided by platforms for performing specific tasks related to
power management (i.e. ->stop_device() may disable a device's
clocks, while ->start_device() may enable them, ->power_on() is
supposed to remove power from the entire power domain
and ->power_off() is supposed to restore it).

Introduce functions that can be used as power domain runtime PM
callbacks, pm_genpd_runtime_suspend() and pm_genpd_runtime_resume(),
as well as helper functions for the initialization of a power
domain represented by a struct generic_power_domain object,
adding a device to or removing a device from it and adding or
removing subdomains.

Signed-off-by: Rafael J. Wysocki <rjw@sisk.pl>
---
 drivers/base/power/Makefile |    2 
 drivers/base/power/domain.c |  416 ++++++++++++++++++++++++++++++++++++++++++++
 include/linux/pm.h          |    3 
 include/linux/pm_domain.h   |   82 ++++++++
 4 files changed, 501 insertions(+), 2 deletions(-)


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Comments

Rafael Wysocki April 29, 2011, 8:11 p.m. UTC | #1
On Friday, April 29, 2011, MyungJoo Ham wrote:
> On Fri, Apr 29, 2011 at 8:54 AM, Rafael J. Wysocki <rjw@sisk.pl> wrote:
> > From: Rafael J. Wysocki <rjw@sisk.pl>
> >
> > Introcude common headers, helper functions and callbacks allowing
> > platforms to use simple generic power domains for runtime power
> > management.
> >
> > Introduce struct generic_power_domain to be used for representing
> > power domains that each contain a number of devices and may be
> > master domains or subdomains with respect to other power domains.
> > Among other things, this structure includes callbacks to be
> > provided by platforms for performing specific tasks related to
> > power management (i.e. ->stop_device() may disable a device's
> > clocks, while ->start_device() may enable them, ->power_on() is
> > supposed to remove power from the entire power domain
> > and ->power_off() is supposed to restore it).
> >
> > Introduce functions that can be used as power domain runtime PM
> > callbacks, pm_genpd_runtime_suspend() and pm_genpd_runtime_resume(),
> > as well as helper functions for the initialization of a power
> > domain represented by a struct generic_power_domain object,
> > adding a device to or removing a device from it and adding or
> > removing subdomains.
> >
> > Signed-off-by: Rafael J. Wysocki <rjw@sisk.pl>
> 
> Hi!
> 
> The pm_domain is assuming that there is at most one powerdomain per
> device, which is perfectly fine with my machines and the concept of
> in-SoC powerdomains.
> 
> However, if so, wouldn't it be possible to simply set powerdomain by
> setting a device's parent?
> For example, for a device, struct device *dev, and a powerdomain,
> struct device *pd, use
>  "dev.parent = pd;", and let runtime-pm handle including the
> "dev_power_governor" in the pm_domain's pm related code.

Well, not really.  There are a few things to consider.

First, in general, there may be devices that have a real parent and belong
to a power domain at the same time, so we can't "steal" the parent
pointers from them.

Second, we generally don't want subsystem-level runtime PM callbacks to be
executed directly for devices in a power domain and the domain's
callbacks are used instead.  Normally, subsystem (e.g. bus type) callbacks
execute drivers' callbacks, but for devices in a power domain we may not
really want the drivers' callbacks to be executed until the domain is ready
for power removal (i.e. pm_runtime_suspend() or equivalent has been called
for all devices in the domain already).  If we were to use the approach
you suggest, we'd need to override the subsystem's runtime PM callbacks for
the devices in the power domain _anyway_ and _additionally_ we'd need to
represent that power domain as the parent of all of those devices.  While that
might work in principle, I think it's more straightforward to do it like
in the $subject patch.  [In this approach a power domain may be regarded as an
entity providing PM callbacks replacing the subsystem ones for devices
belonging to it and those callbacks should be sufficient to make things work
without additional modifications of the device hierarchy.]

Next, if power domains were to be represented by device objects, we'd
need to create subsystem (e.g. bus type) objects providing PM callbacks
for them (so, for example, we'd have a "generic power domain" bus type)
and we'd probably need drivers for power domain "devices".  It seems that
this additional infrastructure would be a bit overweight.

Finally, if a power domain were represented as a parent of its devices,
its (or its subsystem's) runtime PM callbacks would end up executing the
runtime PM callbacks provided by its child devices' drivers, which would be
kind of unusual, so to speak.

There probably are more arguments, but I guess the above are sufficient. :-)

Thanks,
Rafael
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Greg Kroah-Hartman April 29, 2011, 8:54 p.m. UTC | #2
On Fri, Apr 29, 2011 at 01:54:55AM +0200, Rafael J. Wysocki wrote:
> From: Rafael J. Wysocki <rjw@sisk.pl>
> 
> Introcude common headers, helper functions and callbacks allowing
> platforms to use simple generic power domains for runtime power
> management.
> 
> Introduce struct generic_power_domain to be used for representing
> power domains that each contain a number of devices and may be
> master domains or subdomains with respect to other power domains.
> Among other things, this structure includes callbacks to be
> provided by platforms for performing specific tasks related to
> power management (i.e. ->stop_device() may disable a device's
> clocks, while ->start_device() may enable them, ->power_on() is
> supposed to remove power from the entire power domain
> and ->power_off() is supposed to restore it).
> 
> Introduce functions that can be used as power domain runtime PM
> callbacks, pm_genpd_runtime_suspend() and pm_genpd_runtime_resume(),
> as well as helper functions for the initialization of a power
> domain represented by a struct generic_power_domain object,
> adding a device to or removing a device from it and adding or
> removing subdomains.
> 
> Signed-off-by: Rafael J. Wysocki <rjw@sisk.pl>
> ---
>  drivers/base/power/Makefile |    2 
>  drivers/base/power/domain.c |  416 ++++++++++++++++++++++++++++++++++++++++++++
>  include/linux/pm.h          |    3 
>  include/linux/pm_domain.h   |   82 ++++++++
>  4 files changed, 501 insertions(+), 2 deletions(-)

If this solves the power domain issue, and no one has any problems with
getting to work on their platforms, it looks great to me.

Very nice job:
	Acked-by: Greg Kroah-Hartman <gregkh@suse.de>

thanks,

greg k-h
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MyungJoo Ham May 4, 2011, 8:43 a.m. UTC | #3
On Sat, Apr 30, 2011 at 5:11 AM, Rafael J. Wysocki <rjw@sisk.pl> wrote:
>
> Well, not really.  There are a few things to consider.
>
> First, in general, there may be devices that have a real parent and belong
> to a power domain at the same time, so we can't "steal" the parent
> pointers from them.

Ah. right we only have one parent per device. Ok, setting a power
domain as a device's parent is not going to work for some devices.


However, I have some other questions.

1. pm_genpd_runtime_suspend and pm_genpd_runtime_resume are opened to
outside (not static and "extern"ed). Are devices supposed to call
pm_genpd_runtime_* directly? Shouldn't they be hidden so that devices
are forced to turn on/off power domains with runtime_pm framework
only? Is there any reason to expose them?

2.  If we can assure that related clocks are not turned on when a
power domain is shutting down, it'd be nice.
I guess it would be sufficient to let it "WARN" at
gov->power_down_ok(). Is it the intention of governor?


Thank you! I also think this is going to help us a lot, too :)

- MyungJoo
Rafael Wysocki May 4, 2011, 5:08 p.m. UTC | #4
On Wednesday, May 04, 2011, MyungJoo Ham wrote:
> On Sat, Apr 30, 2011 at 5:11 AM, Rafael J. Wysocki <rjw@sisk.pl> wrote:
> >
> > Well, not really.  There are a few things to consider.
> >
> > First, in general, there may be devices that have a real parent and belong
> > to a power domain at the same time, so we can't "steal" the parent
> > pointers from them.
> 
> Ah. right we only have one parent per device. Ok, setting a power
> domain as a device's parent is not going to work for some devices.
> 
> 
> However, I have some other questions.
> 
> 1. pm_genpd_runtime_suspend and pm_genpd_runtime_resume are opened to
> outside (not static and "extern"ed). Are devices supposed to call
> pm_genpd_runtime_* directly?

I suppose you mean drivers.  No, they aren't.

> Shouldn't they be hidden so that devices
> are forced to turn on/off power domains with runtime_pm framework
> only? Is there any reason to expose them?

I thought some subsystems might bypass pm_genpd_init() and use their own
initialization, in which case the extern definitions would be useful.

That said, they aren't necessary at the moment, so I'll make them static
in the final version of the patch.

> 2.  If we can assure that related clocks are not turned on when a
> power domain is shutting down, it'd be nice.

If you look at the shmobile patch at
https://patchwork.kernel.org/patch/742932/
you'll see that it uses the ->stop_device() and ->start_device()
callbacks for this purpose.

> I guess it would be sufficient to let it "WARN" at
> gov->power_down_ok().

Sure, you can do that too.

> Is it the intention of governor?

No, the intention of the governor is to make it possible to take
for example, latencies, into account when deciding whether or not to
power down the domain.  In short, my idea is that the governor will
have information on how much time it's going to take to power down
and resume the power domain (along with all devices) and, on the other hand,
what maximum wakeup latency is acceptable for the given power domain.
It will compare the two numbers and return "true" if the second one is
greater, for example.  That said, I don't have a clean use case at the moment,
so that's more of a future stub than something necessary right now.

> Thank you! I also think this is going to help us a lot, too :)

Good to hear that. :-)

Thanks,
Rafael
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diff mbox

Patch

Index: linux-2.6/include/linux/pm_domain.h
===================================================================
--- /dev/null
+++ linux-2.6/include/linux/pm_domain.h
@@ -0,0 +1,82 @@ 
+/*
+ * pm_domain.h - Definitions and headers related to device power domains.
+ *
+ * Copyright (C) 2011 Rafael J. Wysocki <rjw@sisk.pl>, Renesas Electronics Corp.
+ *
+ * This file is released under the GPLv2.
+ */
+
+#ifndef _LINUX_PM_DOMAIN_H
+#define _LINUX_PM_DOMAIN_H
+
+#include <linux/device.h>
+
+struct dev_power_governor {
+	bool (*power_down_ok)(struct dev_power_domain *domain);
+};
+
+struct generic_power_domain {
+	struct dev_power_domain domain;
+	struct list_head node;
+	struct generic_power_domain *master;
+	struct list_head subdomain_list;
+	struct list_head device_list;
+	struct mutex lock;
+	struct dev_power_governor *gov;
+	bool power_is_off;
+	int (*power_off)(struct dev_power_domain *domain);
+	int (*power_on)(struct dev_power_domain *domain);
+	int (*start_device)(struct device *dev);
+	int (*stop_device)(struct device *dev);
+};
+
+struct dev_list_entry {
+	struct list_head node;
+	struct device *dev;
+};
+
+#ifdef CONFIG_PM_RUNTIME
+extern int pm_genpd_runtime_suspend(struct device *dev);
+extern int pm_genpd_runtime_resume(struct device *dev);
+#else
+#define pm_genpd_runtime_suspend	NULL;
+#define pm_genpd_runtime_resume	NULL;
+#endif
+
+#ifdef CONFIG_PM
+extern int pm_genpd_add_device(struct generic_power_domain *genpd,
+			       struct device *dev);
+extern int pm_genpd_remove_device(struct generic_power_domain *genpd,
+				  struct device *dev);
+extern int pm_genpd_add_subdomain(struct generic_power_domain *genpd,
+				  struct generic_power_domain *new_subdomain);
+extern int pm_genpd_remove_subdomain(struct generic_power_domain *genpd,
+				     struct generic_power_domain *target);
+extern void pm_genpd_init(struct generic_power_domain *genpd,
+			  struct dev_power_governor *gov, bool is_off);
+#else
+static inline int pm_genpd_add_device(struct generic_power_domain *genpd,
+				      struct device *dev)
+{
+	return -ENOSYS;
+}
+static inline int pm_genpd_remove_device(struct generic_power_domain *genpd,
+					 struct device *dev)
+{
+	return -ENOSYS;
+}
+static inline int pm_genpd_add_subdomain(struct generic_power_domain *genpd,
+					 struct generic_power_domain *new_sd)
+{
+	return -ENOSYS;
+}
+static inline int pm_genpd_remove_subdomain(struct generic_power_domain *genpd,
+					    struct generic_power_domain *target)
+{
+	return -ENOSYS;
+}
+static inline void pm_genpd_init(struct generic_power_domain *genpd,
+				 struct dev_power_governor *gov, bool is_off) {}
+#endif
+
+#endif /* _LINUX_PM_DOMAIN_H */
Index: linux-2.6/include/linux/pm.h
===================================================================
--- linux-2.6.orig/include/linux/pm.h
+++ linux-2.6/include/linux/pm.h
@@ -472,7 +472,8 @@  extern void update_pm_runtime_accounting
  * subsystem-level and driver-level callbacks.
  */
 struct dev_power_domain {
-	struct dev_pm_ops	ops;
+	struct dev_pm_ops ops;
+	void *platform_data;
 };
 
 /*
Index: linux-2.6/drivers/base/power/Makefile
===================================================================
--- linux-2.6.orig/drivers/base/power/Makefile
+++ linux-2.6/drivers/base/power/Makefile
@@ -1,4 +1,4 @@ 
-obj-$(CONFIG_PM)	+= sysfs.o generic_ops.o
+obj-$(CONFIG_PM)	+= sysfs.o generic_ops.o domain.o
 obj-$(CONFIG_PM_SLEEP)	+= main.o wakeup.o
 obj-$(CONFIG_PM_RUNTIME)	+= runtime.o
 obj-$(CONFIG_PM_TRACE_RTC)	+= trace.o
Index: linux-2.6/drivers/base/power/domain.c
===================================================================
--- /dev/null
+++ linux-2.6/drivers/base/power/domain.c
@@ -0,0 +1,416 @@ 
+/*
+ * 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/slab.h>
+#include <linux/err.h>
+
+#ifdef CONFIG_PM_RUNTIME
+
+/**
+ * __pm_genpd_restore_device - Restore a pre-suspend state of a device.
+ * @dev: Device to restore the state of.
+ * @genpd: Power domain the device belongs to.
+ */
+static void __pm_genpd_restore_device(struct device *dev,
+				      struct generic_power_domain *genpd)
+{
+	struct device_driver *drv = dev->driver;
+
+	if (genpd->start_device)
+		genpd->start_device(dev);
+
+	if (drv && drv->pm && drv->pm->runtime_resume)
+		drv->pm->runtime_resume(dev);
+
+	if (genpd->stop_device)
+		genpd->stop_device(dev);
+}
+
+/**
+ * __pm_genpd_poweroff - Remove power from a given power domain.
+ * @genpd: Power 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_power_domain *genpd)
+{
+	struct generic_power_domain *subdomain;
+	struct dev_list_entry *dle;
+	int ret;
+
+	if (genpd->power_is_off)
+		return 0;
+
+	list_for_each_entry(dle, &genpd->device_list, node)
+		if (!pm_runtime_suspended(dle->dev))
+			return -EBUSY;
+
+	list_for_each_entry_reverse(subdomain, &genpd->subdomain_list, node) {
+		mutex_lock(&subdomain->lock);
+		ret = __pm_genpd_poweroff(subdomain);
+		mutex_unlock(&subdomain->lock);
+		if (ret)
+			return ret;
+	}
+
+	if (genpd->gov && genpd->gov->power_down_ok) {
+		if (!genpd->gov->power_down_ok(&genpd->domain))
+			return -EAGAIN;
+	}
+
+	list_for_each_entry_reverse(dle, &genpd->device_list, node) {
+		struct device *dev = dle->dev;
+		struct device_driver *drv = dev->driver;
+
+		if (genpd->start_device)
+			genpd->start_device(dev);
+
+		if (drv && drv->pm && drv->pm->runtime_suspend)
+			ret = drv->pm->runtime_suspend(dev);
+
+		if (genpd->stop_device)
+			genpd->stop_device(dev);
+
+		if (ret)
+			goto err_dev;
+	}
+
+	if (genpd->power_off)
+		genpd->power_off(&genpd->domain);
+
+	genpd->power_is_off = true;
+
+	return 0;
+
+ err_dev:
+	list_for_each_entry_continue(dle, &genpd->device_list, node)
+		__pm_genpd_restore_device(dle->dev, genpd);
+
+	return ret;
+}
+
+/**
+ * pm_genpd_poweroff - Remove power from a given power domain and its masters.
+ * @genpd: Power domain to power down.
+ *
+ * Try to remove power from @genpd and all of its masters in order to save as
+ * much power as possible.
+ */
+static int pm_genpd_poweroff(struct generic_power_domain *genpd)
+{
+	struct generic_power_domain *master;
+	int ret;
+
+	mutex_lock(&genpd->lock);
+	master = genpd->master;
+	if (master) {
+		mutex_unlock(&genpd->lock);
+		return pm_genpd_poweroff(master);
+	}
+	ret = __pm_genpd_poweroff(genpd);
+	mutex_unlock(&genpd->lock);
+
+	return ret;
+}
+
+/**
+ * pm_genpd_runtime_suspend - Suspend a device belonging to I/O power domain.
+ * @dev: Device to suspend.
+ *
+ * Carry out a runtime suspend of a device under the assumption that its
+ * pwr_domain field points to the domain member of an object of type
+ * struct generic_power_domain representing a power domain consisting of I/O
+ * devices.
+ */
+int pm_genpd_runtime_suspend(struct device *dev)
+{
+	struct generic_power_domain *genpd;
+
+	dev_dbg(dev, "%s()\n", __func__);
+
+	if (IS_ERR_OR_NULL(dev->pwr_domain))
+		return -EINVAL;
+
+	genpd = container_of(dev->pwr_domain,
+			     struct generic_power_domain, domain);
+
+	if (genpd->stop_device) {
+		int ret = genpd->stop_device(dev);
+		if (ret)
+			return ret;
+	}
+
+	return pm_genpd_poweroff(genpd);
+}
+
+/**
+ * __pm_genpd_poweron - Restore power for a given power domain.
+ * @genpd: Power domain to power up.
+ *
+ * Restore power for @genpd and run runtime resume callbacks provided by all of
+ * its devices' drivers.
+ */
+static int __pm_genpd_poweron(struct generic_power_domain *genpd)
+{
+	struct dev_list_entry *dle;
+
+	if (!genpd->power_is_off)
+		return 0;
+
+	if (genpd->power_on) {
+		int ret = genpd->power_on(&genpd->domain);
+		if (ret)
+			return ret;
+	}
+
+	genpd->power_is_off = false;
+
+	list_for_each_entry(dle, &genpd->device_list, node)
+		__pm_genpd_restore_device(dle->dev, genpd);
+
+	return 0;
+}
+
+/**
+ * pm_genpd_poweron - Restore power for a given power domain and its masters.
+ * @genpd: Power domain to power up.
+ *
+ * Restore power for @genpd and all of its masters so that it is possible to
+ * resume a device belonging to it.
+ */
+static int pm_genpd_poweron(struct generic_power_domain *genpd)
+{
+	struct generic_power_domain *master;
+	int ret;
+
+	mutex_lock(&genpd->lock);
+	master = genpd->master;
+	if (master) {
+		mutex_unlock(&genpd->lock);
+
+		ret = pm_genpd_poweron(master);
+		if (ret)
+			return ret;
+
+		mutex_lock(&genpd->lock);
+	}
+	ret = __pm_genpd_poweron(genpd);
+	mutex_unlock(&genpd->lock);
+
+	return ret;
+}
+
+/**
+ * pm_genpd_runtime_resume - Resume a device belonging to I/O power domain.
+ * @dev: Device to suspend.
+ *
+ * Carry out a runtime resume of a device under the assumption that its
+ * pwr_domain field points to the domain member of an object of type
+ * struct generic_power_domain representing a power domain consisting of I/O
+ * devices.
+ */
+int pm_genpd_runtime_resume(struct device *dev)
+{
+	struct generic_power_domain *genpd;
+	int ret;
+
+	dev_dbg(dev, "%s()\n", __func__);
+
+	if (IS_ERR_OR_NULL(dev->pwr_domain))
+		return -EINVAL;
+
+	genpd = container_of(dev->pwr_domain,
+			     struct generic_power_domain, domain);
+
+	ret = pm_genpd_poweron(genpd);
+	if (ret)
+		return ret;
+
+	if (genpd->start_device)
+		genpd->start_device(dev);
+
+	return 0;
+}
+
+#endif /* CONFIG_PM_RUNTIME */
+
+/**
+ * pm_genpd_add_device - Add a device to an I/O power domain.
+ * @genpd: Power domain to add the device to.
+ * @dev: Device to be added.
+ */
+int pm_genpd_add_device(struct generic_power_domain *genpd, struct device *dev)
+{
+	struct dev_list_entry *dle;
+	int ret = 0;
+
+	dev_dbg(dev, "%s()\n", __func__);
+
+	if (IS_ERR_OR_NULL(genpd) || IS_ERR_OR_NULL(dev))
+		return -EINVAL;
+
+	mutex_lock(&genpd->lock);
+
+	list_for_each_entry(dle, &genpd->device_list, node)
+		if (dle->dev == dev) {
+			ret = -EINVAL;
+			goto out;
+		}
+
+	dle = kzalloc(sizeof(*dle), GFP_KERNEL);
+	if (!dle) {
+		ret = -ENOMEM;
+		goto out;
+	}
+
+	dle->dev = dev;
+	list_add_tail(&dle->node, &genpd->device_list);
+
+	spin_lock_irq(&dev->power.lock);
+	dev->pwr_domain = &genpd->domain;
+	spin_unlock_irq(&dev->power.lock);
+
+ out:
+	mutex_unlock(&genpd->lock);
+
+	return ret;
+}
+
+/**
+ * pm_genpd_remove_device - Remove a device from an I/O power domain.
+ * @genpd: Power domain to remove the device from.
+ * @dev: Device to be removed.
+ */
+int pm_genpd_remove_device(struct generic_power_domain *genpd,
+			   struct device *dev)
+{
+	struct dev_list_entry *dle;
+	int ret = -EINVAL;
+
+	dev_dbg(dev, "%s()\n", __func__);
+
+	if (IS_ERR_OR_NULL(genpd) || IS_ERR_OR_NULL(dev))
+		return -EINVAL;
+
+	mutex_lock(&genpd->lock);
+
+	list_for_each_entry(dle, &genpd->device_list, node) {
+		if (dle->dev != dev)
+			continue;
+
+		spin_lock_irq(&dev->power.lock);
+		dev->pwr_domain = NULL;
+		spin_unlock_irq(&dev->power.lock);
+
+		list_del(&dle->node);
+		kfree(dle);
+
+		ret = 0;
+		break;
+	}
+
+	mutex_unlock(&genpd->lock);
+
+	return ret;
+}
+
+/**
+ * pm_genpd_add_subdomain - Add a subdomain to an I/O power domain.
+ * @genpd: Master power domain to add the subdomain to.
+ * @new_subdomain: Subdomain to be added.
+ */
+int pm_genpd_add_subdomain(struct generic_power_domain *genpd,
+			   struct generic_power_domain *new_subdomain)
+{
+	struct generic_power_domain *subdomain;
+	int ret = 0;
+
+	if (IS_ERR_OR_NULL(genpd) || IS_ERR_OR_NULL(new_subdomain))
+		return -EINVAL;
+
+	mutex_lock(&genpd->lock);
+
+	list_for_each_entry(subdomain, &genpd->subdomain_list, node)
+		if (subdomain == new_subdomain) {
+			ret = -EINVAL;
+			goto out;
+		}
+
+	mutex_lock(&new_subdomain->lock);
+	list_add_tail(&new_subdomain->node, &genpd->subdomain_list);
+	new_subdomain->master = genpd;
+	mutex_unlock(&new_subdomain->lock);
+
+ out:
+	mutex_unlock(&genpd->lock);
+
+	return ret;
+}
+
+/**
+ * pm_genpd_remove_subdomain - Remove a subdomain from an I/O power domain.
+ * @genpd: Master power domain to remove the subdomain from.
+ * @target: Subdomain to be removed.
+ */
+int pm_genpd_remove_subdomain(struct generic_power_domain *genpd,
+			      struct generic_power_domain *target)
+{
+	struct generic_power_domain *subdomain;
+	int ret = -EINVAL;
+
+	if (IS_ERR_OR_NULL(genpd) || IS_ERR_OR_NULL(target))
+		return -EINVAL;
+
+	mutex_lock(&genpd->lock);
+
+	list_for_each_entry(subdomain, &genpd->subdomain_list, node) {
+		if (subdomain != target)
+			continue;
+
+		mutex_lock(&subdomain->lock);
+		list_del(&subdomain->node);
+		subdomain->master = NULL;
+		mutex_unlock(&subdomain->lock);
+
+		ret = 0;
+		break;
+	}
+
+	mutex_unlock(&genpd->lock);
+
+	return ret;
+}
+
+/**
+ * pm_genpd_init - Initialize an I/O power domain object.
+ * @genpd: Power domain object to initialize.
+ */
+void pm_genpd_init(struct generic_power_domain *genpd,
+		   struct dev_power_governor *gov, bool is_off)
+{
+	if (IS_ERR_OR_NULL(genpd))
+		return;
+
+	INIT_LIST_HEAD(&genpd->node);
+	genpd->master = NULL;
+	INIT_LIST_HEAD(&genpd->device_list);
+	INIT_LIST_HEAD(&genpd->subdomain_list);
+	mutex_init(&genpd->lock);
+	genpd->gov = gov;
+	genpd->power_is_off = is_off;
+	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;
+}