[v10,02/27] PM / Domains: Add support for CPU devices to genpd
diff mbox series

Message ID 20181129174700.16585-3-ulf.hansson@linaro.org
State Deferred
Headers show
Series
  • PM / Domains: Support hierarchical CPU arrangement (PSCI/ARM)
Related show

Commit Message

Ulf Hansson Nov. 29, 2018, 5:46 p.m. UTC
To enable a device belonging to a CPU to be attached to a PM domain managed
by genpd, let's do a few changes to it, as to make it convenient to manage
the specifics around CPUs.

To be able to quickly find out what CPUs that are attached to a genpd,
which typically becomes useful from a genpd governor as following changes
is about to show, let's add a cpumask to the struct generic_pm_domain. At
the point when a CPU device gets attached to a genpd, let's update its
cpumask. Moreover, let's also propagate changes to the cpumask upwards in
the topology to the master PM domains. In this way, the cpumask for a genpd
hierarchically reflects all CPUs attached to the topology below it.

Finally, let's make this an opt-in feature, to avoid having to manage CPUs
and the cpumask for a genpd that doesn't need it. For that reason, let's
add a new genpd configuration bit, GENPD_FLAG_CPU_DOMAIN.

Cc: Lina Iyer <ilina@codeaurora.org>
Co-developed-by: Lina Iyer <lina.iyer@linaro.org>
Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>
---

Changes in v10:
	- Don't allocate the cpumask when not used.
	- Simplify the code that updates the cpumask.
	- Document the GENPD_FLAG_CPU_DOMAIN.

---
 drivers/base/power/domain.c | 66 ++++++++++++++++++++++++++++++++++++-
 include/linux/pm_domain.h   | 13 ++++++++
 2 files changed, 78 insertions(+), 1 deletion(-)

Comments

Daniel Lezcano Dec. 19, 2018, 9:53 a.m. UTC | #1
On 29/11/2018 18:46, Ulf Hansson wrote:
> To enable a device belonging to a CPU to be attached to a PM domain managed
> by genpd, let's do a few changes to it, as to make it convenient to manage
> the specifics around CPUs.
> 
> To be able to quickly find out what CPUs that are attached to a genpd,
> which typically becomes useful from a genpd governor as following changes
> is about to show, let's add a cpumask to the struct generic_pm_domain. At
> the point when a CPU device gets attached to a genpd, let's update its
> cpumask. Moreover, let's also propagate changes to the cpumask upwards in
> the topology to the master PM domains. In this way, the cpumask for a genpd
> hierarchically reflects all CPUs attached to the topology below it.
> 
> Finally, let's make this an opt-in feature, to avoid having to manage CPUs
> and the cpumask for a genpd that doesn't need it. For that reason, let's
> add a new genpd configuration bit, GENPD_FLAG_CPU_DOMAIN.
> 
> Cc: Lina Iyer <ilina@codeaurora.org>
> Co-developed-by: Lina Iyer <lina.iyer@linaro.org>
> Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>
> ---
> 
> Changes in v10:
> 	- Don't allocate the cpumask when not used.
> 	- Simplify the code that updates the cpumask.
> 	- Document the GENPD_FLAG_CPU_DOMAIN.
> 
> ---
>  drivers/base/power/domain.c | 66 ++++++++++++++++++++++++++++++++++++-
>  include/linux/pm_domain.h   | 13 ++++++++
>  2 files changed, 78 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/base/power/domain.c b/drivers/base/power/domain.c
> index e27b91d36a2a..c3ff8e395308 100644
> --- a/drivers/base/power/domain.c
> +++ b/drivers/base/power/domain.c
> @@ -20,6 +20,7 @@
>  #include <linux/sched.h>
>  #include <linux/suspend.h>
>  #include <linux/export.h>
> +#include <linux/cpu.h>
>  
>  #include "power.h"
>  
> @@ -126,6 +127,7 @@ static const struct genpd_lock_ops genpd_spin_ops = {
>  #define genpd_is_irq_safe(genpd)	(genpd->flags & GENPD_FLAG_IRQ_SAFE)
>  #define genpd_is_always_on(genpd)	(genpd->flags & GENPD_FLAG_ALWAYS_ON)
>  #define genpd_is_active_wakeup(genpd)	(genpd->flags & GENPD_FLAG_ACTIVE_WAKEUP)
> +#define genpd_is_cpu_domain(genpd)	(genpd->flags & GENPD_FLAG_CPU_DOMAIN)
>  
>  static inline bool irq_safe_dev_in_no_sleep_domain(struct device *dev,
>  		const struct generic_pm_domain *genpd)
> @@ -1377,6 +1379,56 @@ static void genpd_free_dev_data(struct device *dev,
>  	dev_pm_put_subsys_data(dev);
>  }
>  
> +static void __genpd_update_cpumask(struct generic_pm_domain *genpd,
> +				   int cpu, bool set, unsigned int depth)
> +{
> +	struct gpd_link *link;
> +
> +	if (!genpd_is_cpu_domain(genpd))
> +		return;

With this test, we won't continue updating the cpumask for the other
masters. Is it done on purpose ?

> +	list_for_each_entry(link, &genpd->slave_links, slave_node) {
> +		struct generic_pm_domain *master = link->master;
> +
> +		genpd_lock_nested(master, depth + 1);
> +		__genpd_update_cpumask(master, cpu, set, depth + 1);
> +		genpd_unlock(master);
> +	}
> +
> +	if (set)
> +		cpumask_set_cpu(cpu, genpd->cpus);
> +	else
> +		cpumask_clear_cpu(cpu, genpd->cpus);
> +}
> +
> +static void genpd_update_cpumask(struct generic_pm_domain *genpd,
> +				 struct device *dev, bool set)
> +{
> +	int cpu;
> +
> +	if (!genpd_is_cpu_domain(genpd))
> +		return;
> +
> +	for_each_possible_cpu(cpu) {
> +		if (get_cpu_device(cpu) == dev) {
> +			__genpd_update_cpumask(genpd, cpu, set, 0);
> +			return;
> +		}
> +	}
> +}
> +
> +static void genpd_set_cpumask(struct generic_pm_domain *genpd,
> +			      struct device *dev)
> +{
> +	genpd_update_cpumask(genpd, dev, true);
> +}
> +
> +static void genpd_clear_cpumask(struct generic_pm_domain *genpd,
> +				struct device *dev)
> +{
> +	genpd_update_cpumask(genpd, dev, false);
> +}
> +
>  static int genpd_add_device(struct generic_pm_domain *genpd, struct device *dev,
>  			    struct gpd_timing_data *td)
>  {
> @@ -1398,6 +1450,8 @@ static int genpd_add_device(struct generic_pm_domain *genpd, struct device *dev,
>  	if (ret)
>  		goto out;
>  
> +	genpd_set_cpumask(genpd, dev);
> +
>  	dev_pm_domain_set(dev, &genpd->domain);
>  
>  	genpd->device_count++;
> @@ -1459,6 +1513,7 @@ static int genpd_remove_device(struct generic_pm_domain *genpd,
>  	if (genpd->detach_dev)
>  		genpd->detach_dev(genpd, dev);
>  
> +	genpd_clear_cpumask(genpd, dev);
>  	dev_pm_domain_set(dev, NULL);
>  
>  	list_del_init(&pdd->list_node);
> @@ -1686,11 +1741,18 @@ int pm_genpd_init(struct generic_pm_domain *genpd,
>  	if (genpd_is_always_on(genpd) && !genpd_status_on(genpd))
>  		return -EINVAL;
>  
> +	if (genpd_is_cpu_domain(genpd) &&
> +	    !zalloc_cpumask_var(&genpd->cpus, GFP_KERNEL))
> +		return -ENOMEM;
> +
>  	/* Use only one "off" state if there were no states declared */
>  	if (genpd->state_count == 0) {
>  		ret = genpd_set_default_power_state(genpd);
> -		if (ret)
> +		if (ret) {
> +			if (genpd_is_cpu_domain(genpd))
> +				free_cpumask_var(genpd->cpus);
>  			return ret;
> +		}
>  	} else if (!gov) {
>  		pr_warn("%s : no governor for states\n", genpd->name);
>  	}
> @@ -1736,6 +1798,8 @@ static int genpd_remove(struct generic_pm_domain *genpd)
>  	list_del(&genpd->gpd_list_node);
>  	genpd_unlock(genpd);
>  	cancel_work_sync(&genpd->power_off_work);
> +	if (genpd_is_cpu_domain(genpd))
> +		free_cpumask_var(genpd->cpus);
>  	if (genpd->free_state) {
>  		kfree(genpd->states);
>  		genpd->states = NULL;
> diff --git a/include/linux/pm_domain.h b/include/linux/pm_domain.h
> index f9e09bd4152c..5a4673605d22 100644
> --- a/include/linux/pm_domain.h
> +++ b/include/linux/pm_domain.h
> @@ -16,6 +16,7 @@
>  #include <linux/of.h>
>  #include <linux/notifier.h>
>  #include <linux/spinlock.h>
> +#include <linux/cpumask.h>
>  
>  /*
>   * Flags to control the behaviour of a genpd.
> @@ -42,11 +43,22 @@
>   * GENPD_FLAG_ACTIVE_WAKEUP:	Instructs genpd to keep the PM domain powered
>   *				on, in case any of its attached devices is used
>   *				in the wakeup path to serve system wakeups.
> + *
> + * GENPD_FLAG_CPU_DOMAIN:	Instructs genpd that it should expect to get
> + *				devices attached, which may belong to CPUs or
> + *				possibly have subdomains with CPUs attached.
> + *				This flag enables the genpd backend driver to
> + *				deploy idle power management support for CPUs
> + *				and groups of CPUs. Note that, the backend
> + *				driver must then comply with the so called,
> + *				last-man-standing algorithm, for the CPUs in the
> + *				PM domain.
>   */
>  #define GENPD_FLAG_PM_CLK	 (1U << 0)
>  #define GENPD_FLAG_IRQ_SAFE	 (1U << 1)
>  #define GENPD_FLAG_ALWAYS_ON	 (1U << 2)
>  #define GENPD_FLAG_ACTIVE_WAKEUP (1U << 3)
> +#define GENPD_FLAG_CPU_DOMAIN	 (1U << 4)
>  
>  enum gpd_status {
>  	GPD_STATE_ACTIVE = 0,	/* PM domain is active */
> @@ -93,6 +105,7 @@ struct generic_pm_domain {
>  	unsigned int suspended_count;	/* System suspend device counter */
>  	unsigned int prepared_count;	/* Suspend counter of prepared devices */
>  	unsigned int performance_state;	/* Aggregated max performance state */
> +	cpumask_var_t cpus;		/* A cpumask of the attached CPUs */
>  	int (*power_off)(struct generic_pm_domain *domain);
>  	int (*power_on)(struct generic_pm_domain *domain);
>  	unsigned int (*opp_to_performance_state)(struct generic_pm_domain *genpd,
>
Ulf Hansson Dec. 19, 2018, 10:02 a.m. UTC | #2
On Wed, 19 Dec 2018 at 10:53, Daniel Lezcano <daniel.lezcano@linaro.org> wrote:
>
> On 29/11/2018 18:46, Ulf Hansson wrote:
> > To enable a device belonging to a CPU to be attached to a PM domain managed
> > by genpd, let's do a few changes to it, as to make it convenient to manage
> > the specifics around CPUs.
> >
> > To be able to quickly find out what CPUs that are attached to a genpd,
> > which typically becomes useful from a genpd governor as following changes
> > is about to show, let's add a cpumask to the struct generic_pm_domain. At
> > the point when a CPU device gets attached to a genpd, let's update its
> > cpumask. Moreover, let's also propagate changes to the cpumask upwards in
> > the topology to the master PM domains. In this way, the cpumask for a genpd
> > hierarchically reflects all CPUs attached to the topology below it.
> >
> > Finally, let's make this an opt-in feature, to avoid having to manage CPUs
> > and the cpumask for a genpd that doesn't need it. For that reason, let's
> > add a new genpd configuration bit, GENPD_FLAG_CPU_DOMAIN.
> >
> > Cc: Lina Iyer <ilina@codeaurora.org>
> > Co-developed-by: Lina Iyer <lina.iyer@linaro.org>
> > Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>
> > ---
> >
> > Changes in v10:
> >       - Don't allocate the cpumask when not used.
> >       - Simplify the code that updates the cpumask.
> >       - Document the GENPD_FLAG_CPU_DOMAIN.
> >
> > ---
> >  drivers/base/power/domain.c | 66 ++++++++++++++++++++++++++++++++++++-
> >  include/linux/pm_domain.h   | 13 ++++++++
> >  2 files changed, 78 insertions(+), 1 deletion(-)
> >
> > diff --git a/drivers/base/power/domain.c b/drivers/base/power/domain.c
> > index e27b91d36a2a..c3ff8e395308 100644
> > --- a/drivers/base/power/domain.c
> > +++ b/drivers/base/power/domain.c
> > @@ -20,6 +20,7 @@
> >  #include <linux/sched.h>
> >  #include <linux/suspend.h>
> >  #include <linux/export.h>
> > +#include <linux/cpu.h>
> >
> >  #include "power.h"
> >
> > @@ -126,6 +127,7 @@ static const struct genpd_lock_ops genpd_spin_ops = {
> >  #define genpd_is_irq_safe(genpd)     (genpd->flags & GENPD_FLAG_IRQ_SAFE)
> >  #define genpd_is_always_on(genpd)    (genpd->flags & GENPD_FLAG_ALWAYS_ON)
> >  #define genpd_is_active_wakeup(genpd)        (genpd->flags & GENPD_FLAG_ACTIVE_WAKEUP)
> > +#define genpd_is_cpu_domain(genpd)   (genpd->flags & GENPD_FLAG_CPU_DOMAIN)
> >
> >  static inline bool irq_safe_dev_in_no_sleep_domain(struct device *dev,
> >               const struct generic_pm_domain *genpd)
> > @@ -1377,6 +1379,56 @@ static void genpd_free_dev_data(struct device *dev,
> >       dev_pm_put_subsys_data(dev);
> >  }
> >
> > +static void __genpd_update_cpumask(struct generic_pm_domain *genpd,
> > +                                int cpu, bool set, unsigned int depth)
> > +{
> > +     struct gpd_link *link;
> > +
> > +     if (!genpd_is_cpu_domain(genpd))
> > +             return;
>
> With this test, we won't continue updating the cpumask for the other
> masters. Is it done on purpose ?

Correct, and yes it's on purpose.

We are not even allocating the cpumask for the genpd in question,
unless it has the GENPD_FLAG_CPU_DOMAIN set.

[...]

Kind regards
Uffe
Rafael J. Wysocki Jan. 11, 2019, 10:54 a.m. UTC | #3
On Wednesday, December 19, 2018 11:02:05 AM CET Ulf Hansson wrote:
> On Wed, 19 Dec 2018 at 10:53, Daniel Lezcano <daniel.lezcano@linaro.org> wrote:
> >
> > On 29/11/2018 18:46, Ulf Hansson wrote:
> > > To enable a device belonging to a CPU to be attached to a PM domain managed
> > > by genpd, let's do a few changes to it, as to make it convenient to manage
> > > the specifics around CPUs.
> > >
> > > To be able to quickly find out what CPUs that are attached to a genpd,
> > > which typically becomes useful from a genpd governor as following changes
> > > is about to show, let's add a cpumask to the struct generic_pm_domain. At
> > > the point when a CPU device gets attached to a genpd, let's update its
> > > cpumask. Moreover, let's also propagate changes to the cpumask upwards in
> > > the topology to the master PM domains. In this way, the cpumask for a genpd
> > > hierarchically reflects all CPUs attached to the topology below it.
> > >
> > > Finally, let's make this an opt-in feature, to avoid having to manage CPUs
> > > and the cpumask for a genpd that doesn't need it. For that reason, let's
> > > add a new genpd configuration bit, GENPD_FLAG_CPU_DOMAIN.
> > >
> > > Cc: Lina Iyer <ilina@codeaurora.org>
> > > Co-developed-by: Lina Iyer <lina.iyer@linaro.org>
> > > Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>
> > > ---
> > >
> > > Changes in v10:
> > >       - Don't allocate the cpumask when not used.
> > >       - Simplify the code that updates the cpumask.
> > >       - Document the GENPD_FLAG_CPU_DOMAIN.
> > >
> > > ---
> > >  drivers/base/power/domain.c | 66 ++++++++++++++++++++++++++++++++++++-
> > >  include/linux/pm_domain.h   | 13 ++++++++
> > >  2 files changed, 78 insertions(+), 1 deletion(-)
> > >
> > > diff --git a/drivers/base/power/domain.c b/drivers/base/power/domain.c
> > > index e27b91d36a2a..c3ff8e395308 100644
> > > --- a/drivers/base/power/domain.c
> > > +++ b/drivers/base/power/domain.c
> > > @@ -20,6 +20,7 @@
> > >  #include <linux/sched.h>
> > >  #include <linux/suspend.h>
> > >  #include <linux/export.h>
> > > +#include <linux/cpu.h>
> > >
> > >  #include "power.h"
> > >
> > > @@ -126,6 +127,7 @@ static const struct genpd_lock_ops genpd_spin_ops = {
> > >  #define genpd_is_irq_safe(genpd)     (genpd->flags & GENPD_FLAG_IRQ_SAFE)
> > >  #define genpd_is_always_on(genpd)    (genpd->flags & GENPD_FLAG_ALWAYS_ON)
> > >  #define genpd_is_active_wakeup(genpd)        (genpd->flags & GENPD_FLAG_ACTIVE_WAKEUP)
> > > +#define genpd_is_cpu_domain(genpd)   (genpd->flags & GENPD_FLAG_CPU_DOMAIN)
> > >
> > >  static inline bool irq_safe_dev_in_no_sleep_domain(struct device *dev,
> > >               const struct generic_pm_domain *genpd)
> > > @@ -1377,6 +1379,56 @@ static void genpd_free_dev_data(struct device *dev,
> > >       dev_pm_put_subsys_data(dev);
> > >  }
> > >
> > > +static void __genpd_update_cpumask(struct generic_pm_domain *genpd,
> > > +                                int cpu, bool set, unsigned int depth)
> > > +{
> > > +     struct gpd_link *link;
> > > +
> > > +     if (!genpd_is_cpu_domain(genpd))
> > > +             return;
> >
> > With this test, we won't continue updating the cpumask for the other
> > masters. Is it done on purpose ?
> 
> Correct, and yes it's on purpose.
> 
> We are not even allocating the cpumask for the genpd in question,
> unless it has the GENPD_FLAG_CPU_DOMAIN set.

So this patch is generally fine by me.  You can add my ACK to it when
submitting it again, unless it is changed, so I know I've seen it
already.

Patch
diff mbox series

diff --git a/drivers/base/power/domain.c b/drivers/base/power/domain.c
index e27b91d36a2a..c3ff8e395308 100644
--- a/drivers/base/power/domain.c
+++ b/drivers/base/power/domain.c
@@ -20,6 +20,7 @@ 
 #include <linux/sched.h>
 #include <linux/suspend.h>
 #include <linux/export.h>
+#include <linux/cpu.h>
 
 #include "power.h"
 
@@ -126,6 +127,7 @@  static const struct genpd_lock_ops genpd_spin_ops = {
 #define genpd_is_irq_safe(genpd)	(genpd->flags & GENPD_FLAG_IRQ_SAFE)
 #define genpd_is_always_on(genpd)	(genpd->flags & GENPD_FLAG_ALWAYS_ON)
 #define genpd_is_active_wakeup(genpd)	(genpd->flags & GENPD_FLAG_ACTIVE_WAKEUP)
+#define genpd_is_cpu_domain(genpd)	(genpd->flags & GENPD_FLAG_CPU_DOMAIN)
 
 static inline bool irq_safe_dev_in_no_sleep_domain(struct device *dev,
 		const struct generic_pm_domain *genpd)
@@ -1377,6 +1379,56 @@  static void genpd_free_dev_data(struct device *dev,
 	dev_pm_put_subsys_data(dev);
 }
 
+static void __genpd_update_cpumask(struct generic_pm_domain *genpd,
+				   int cpu, bool set, unsigned int depth)
+{
+	struct gpd_link *link;
+
+	if (!genpd_is_cpu_domain(genpd))
+		return;
+
+	list_for_each_entry(link, &genpd->slave_links, slave_node) {
+		struct generic_pm_domain *master = link->master;
+
+		genpd_lock_nested(master, depth + 1);
+		__genpd_update_cpumask(master, cpu, set, depth + 1);
+		genpd_unlock(master);
+	}
+
+	if (set)
+		cpumask_set_cpu(cpu, genpd->cpus);
+	else
+		cpumask_clear_cpu(cpu, genpd->cpus);
+}
+
+static void genpd_update_cpumask(struct generic_pm_domain *genpd,
+				 struct device *dev, bool set)
+{
+	int cpu;
+
+	if (!genpd_is_cpu_domain(genpd))
+		return;
+
+	for_each_possible_cpu(cpu) {
+		if (get_cpu_device(cpu) == dev) {
+			__genpd_update_cpumask(genpd, cpu, set, 0);
+			return;
+		}
+	}
+}
+
+static void genpd_set_cpumask(struct generic_pm_domain *genpd,
+			      struct device *dev)
+{
+	genpd_update_cpumask(genpd, dev, true);
+}
+
+static void genpd_clear_cpumask(struct generic_pm_domain *genpd,
+				struct device *dev)
+{
+	genpd_update_cpumask(genpd, dev, false);
+}
+
 static int genpd_add_device(struct generic_pm_domain *genpd, struct device *dev,
 			    struct gpd_timing_data *td)
 {
@@ -1398,6 +1450,8 @@  static int genpd_add_device(struct generic_pm_domain *genpd, struct device *dev,
 	if (ret)
 		goto out;
 
+	genpd_set_cpumask(genpd, dev);
+
 	dev_pm_domain_set(dev, &genpd->domain);
 
 	genpd->device_count++;
@@ -1459,6 +1513,7 @@  static int genpd_remove_device(struct generic_pm_domain *genpd,
 	if (genpd->detach_dev)
 		genpd->detach_dev(genpd, dev);
 
+	genpd_clear_cpumask(genpd, dev);
 	dev_pm_domain_set(dev, NULL);
 
 	list_del_init(&pdd->list_node);
@@ -1686,11 +1741,18 @@  int pm_genpd_init(struct generic_pm_domain *genpd,
 	if (genpd_is_always_on(genpd) && !genpd_status_on(genpd))
 		return -EINVAL;
 
+	if (genpd_is_cpu_domain(genpd) &&
+	    !zalloc_cpumask_var(&genpd->cpus, GFP_KERNEL))
+		return -ENOMEM;
+
 	/* Use only one "off" state if there were no states declared */
 	if (genpd->state_count == 0) {
 		ret = genpd_set_default_power_state(genpd);
-		if (ret)
+		if (ret) {
+			if (genpd_is_cpu_domain(genpd))
+				free_cpumask_var(genpd->cpus);
 			return ret;
+		}
 	} else if (!gov) {
 		pr_warn("%s : no governor for states\n", genpd->name);
 	}
@@ -1736,6 +1798,8 @@  static int genpd_remove(struct generic_pm_domain *genpd)
 	list_del(&genpd->gpd_list_node);
 	genpd_unlock(genpd);
 	cancel_work_sync(&genpd->power_off_work);
+	if (genpd_is_cpu_domain(genpd))
+		free_cpumask_var(genpd->cpus);
 	if (genpd->free_state) {
 		kfree(genpd->states);
 		genpd->states = NULL;
diff --git a/include/linux/pm_domain.h b/include/linux/pm_domain.h
index f9e09bd4152c..5a4673605d22 100644
--- a/include/linux/pm_domain.h
+++ b/include/linux/pm_domain.h
@@ -16,6 +16,7 @@ 
 #include <linux/of.h>
 #include <linux/notifier.h>
 #include <linux/spinlock.h>
+#include <linux/cpumask.h>
 
 /*
  * Flags to control the behaviour of a genpd.
@@ -42,11 +43,22 @@ 
  * GENPD_FLAG_ACTIVE_WAKEUP:	Instructs genpd to keep the PM domain powered
  *				on, in case any of its attached devices is used
  *				in the wakeup path to serve system wakeups.
+ *
+ * GENPD_FLAG_CPU_DOMAIN:	Instructs genpd that it should expect to get
+ *				devices attached, which may belong to CPUs or
+ *				possibly have subdomains with CPUs attached.
+ *				This flag enables the genpd backend driver to
+ *				deploy idle power management support for CPUs
+ *				and groups of CPUs. Note that, the backend
+ *				driver must then comply with the so called,
+ *				last-man-standing algorithm, for the CPUs in the
+ *				PM domain.
  */
 #define GENPD_FLAG_PM_CLK	 (1U << 0)
 #define GENPD_FLAG_IRQ_SAFE	 (1U << 1)
 #define GENPD_FLAG_ALWAYS_ON	 (1U << 2)
 #define GENPD_FLAG_ACTIVE_WAKEUP (1U << 3)
+#define GENPD_FLAG_CPU_DOMAIN	 (1U << 4)
 
 enum gpd_status {
 	GPD_STATE_ACTIVE = 0,	/* PM domain is active */
@@ -93,6 +105,7 @@  struct generic_pm_domain {
 	unsigned int suspended_count;	/* System suspend device counter */
 	unsigned int prepared_count;	/* Suspend counter of prepared devices */
 	unsigned int performance_state;	/* Aggregated max performance state */
+	cpumask_var_t cpus;		/* A cpumask of the attached CPUs */
 	int (*power_off)(struct generic_pm_domain *domain);
 	int (*power_on)(struct generic_pm_domain *domain);
 	unsigned int (*opp_to_performance_state)(struct generic_pm_domain *genpd,