[PATCH V2 0/2] cpufreq: Allow light-weight tear down and bring up of CPUs

[PATCH V2 0/2] cpufreq: Allow light-weight tear down and bring up of CPUs

[Viresh Kumar]

The cpufreq core doesn't remove the cpufreq policy anymore on CPU
offline operation, rather that happens when the CPU device gets
unregistered from the kernel. This allows faster recovery when the CPU
comes back online. This is also very useful during system wide
suspend/resume where we offline all non-boot CPUs during suspend and
then bring them back on resume.

This patcset takes the same idea a step ahead to allow drivers to do
light weight tear-down and bring up during CPU offline/online operations
and updates the cpufreq-dt driver to implement the new helpers.

V1->V2:
- s/light_weight_exit()/offline()
- Also introduce the online() counterpart

Viresh Kumar (2):
  cpufreq: Allow light-weight tear down and bring up of CPUs
  cpufreq: dt: Implement online/offline() callbacks

 drivers/cpufreq/cpufreq-dt.c | 17 +++++++++++
 drivers/cpufreq/cpufreq.c    | 55 +++++++++++++++++++++++-------------
 include/linux/cpufreq.h      |  2 ++
 3 files changed, 55 insertions(+), 19 deletions(-)

-- 
2.20.1.321.g9e740568ce00

[PATCH V2 1/2] cpufreq: Allow light-weight tear down and bring up of CPUs

[Viresh Kumar]

The cpufreq core doesn't remove the cpufreq policy anymore on CPU
offline operation, rather that happens when the CPU device gets
unregistered from the kernel. This allows faster recovery when the CPU
comes back online. This is also very useful during system wide
suspend/resume where we offline all non-boot CPUs during suspend and
then bring them back on resume.

This commit takes the same idea a step ahead to allow drivers to do
light weight tear-down and bring-up during CPU offline and online
operations.

A new set of callbacks is introduced, online/offline(). online() gets
called when the first CPU of an inactive policy is brought up and
offline() gets called when all the CPUs of a policy are offlined.

The existing init/exit() callback get called on policy
creation/destruction. They also get called instead of online/offline()
callbacks if the online/offline() callbacks aren't provided.

This also moves around some code to get executed only for the new-policy
case going forward.

Signed-off-by: Viresh Kumar <viresh.kumar@linaro.org>
---
 drivers/cpufreq/cpufreq.c | 55 +++++++++++++++++++++++++--------------
 include/linux/cpufreq.h   |  2 ++
 2 files changed, 38 insertions(+), 19 deletions(-)

diff --git a/drivers/cpufreq/cpufreq.c b/drivers/cpufreq/cpufreq.c
index 96a69c67a545..2b3e9d501f49 100644
--- a/drivers/cpufreq/cpufreq.c
+++ b/drivers/cpufreq/cpufreq.c
@@ -1201,28 +1201,39 @@ static int cpufreq_online(unsigned int cpu)
 			return -ENOMEM;
 	}
 
-	cpumask_copy(policy->cpus, cpumask_of(cpu));
+	if (!new_policy && cpufreq_driver->online) {
+		ret = cpufreq_driver->online(policy);
+		if (ret) {
+			pr_debug("%s: %d: initialization failed\n", __func__,
+				 __LINE__);
+			goto out_exit_policy;
+		}
 
-	/* call driver. From then on the cpufreq must be able
-	 * to accept all calls to ->verify and ->setpolicy for this CPU
-	 */
-	ret = cpufreq_driver->init(policy);
-	if (ret) {
-		pr_debug("initialization failed\n");
-		goto out_free_policy;
-	}
+		/* Recover policy->cpus using related_cpus */
+		cpumask_copy(policy->cpus, policy->related_cpus);
+	} else {
+		cpumask_copy(policy->cpus, cpumask_of(cpu));
 
-	ret = cpufreq_table_validate_and_sort(policy);
-	if (ret)
-		goto out_exit_policy;
+		/*
+		 * Call driver. From then on the cpufreq must be able
+		 * to accept all calls to ->verify and ->setpolicy for this CPU.
+		 */
+		ret = cpufreq_driver->init(policy);
+		if (ret) {
+			pr_debug("%s: %d: initialization failed\n", __func__,
+				 __LINE__);
+			goto out_free_policy;
+		}
 
-	down_write(&policy->rwsem);
+		ret = cpufreq_table_validate_and_sort(policy);
+		if (ret)
+			goto out_exit_policy;
 
-	if (new_policy) {
 		/* related_cpus should at least include policy->cpus. */
 		cpumask_copy(policy->related_cpus, policy->cpus);
 	}
 
+	down_write(&policy->rwsem);
 	/*
 	 * affected cpus must always be the one, which are online. We aren't
 	 * managing offline cpus here.
@@ -1421,11 +1432,12 @@ static int cpufreq_offline(unsigned int cpu)
 		cpufreq_exit_governor(policy);
 
 	/*
-	 * Perform the ->exit() even during light-weight tear-down,
-	 * since this is a core component, and is essential for the
-	 * subsequent light-weight ->init() to succeed.
+	 * Perform the ->offline() during light-weight tear-down, as
+	 * that allows fast recovery when the CPU comes back.
 	 */
-	if (cpufreq_driver->exit) {
+	if (cpufreq_driver->offline) {
+		cpufreq_driver->offline(policy);
+	} else if (cpufreq_driver->exit) {
 		cpufreq_driver->exit(policy);
 		policy->freq_table = NULL;
 	}
@@ -1454,8 +1466,13 @@ static void cpufreq_remove_dev(struct device *dev, struct subsys_interface *sif)
 	cpumask_clear_cpu(cpu, policy->real_cpus);
 	remove_cpu_dev_symlink(policy, dev);
 
-	if (cpumask_empty(policy->real_cpus))
+	if (cpumask_empty(policy->real_cpus)) {
+		/* We did light-weight exit earlier, do full tear down now */
+		if (cpufreq_driver->offline)
+			cpufreq_driver->exit(policy);
+
 		cpufreq_policy_free(policy);
+	}
 }
 
 /**
diff --git a/include/linux/cpufreq.h b/include/linux/cpufreq.h
index 9db074ecbbd7..b160e98076e3 100644
--- a/include/linux/cpufreq.h
+++ b/include/linux/cpufreq.h
@@ -325,6 +325,8 @@ struct cpufreq_driver {
 	/* optional */
 	int		(*bios_limit)(int cpu, unsigned int *limit);
 
+	int		(*online)(struct cpufreq_policy *policy);
+	int		(*offline)(struct cpufreq_policy *policy);
 	int		(*exit)(struct cpufreq_policy *policy);
 	void		(*stop_cpu)(struct cpufreq_policy *policy);
 	int		(*suspend)(struct cpufreq_policy *policy);
-- 
2.20.1.321.g9e740568ce00

[PATCH V2 2/2] cpufreq: dt: Implement online/offline() callbacks

[Viresh Kumar]

Implement the light-weight tear down and bring up helpers to reduce the
amount of work to do on CPU offline/online operation.

Signed-off-by: Viresh Kumar <viresh.kumar@linaro.org>
---
 drivers/cpufreq/cpufreq-dt.c | 17 +++++++++++++++++
 1 file changed, 17 insertions(+)

diff --git a/drivers/cpufreq/cpufreq-dt.c b/drivers/cpufreq/cpufreq-dt.c
index 7ba392911cd0..1aefaa1b0ca2 100644
--- a/drivers/cpufreq/cpufreq-dt.c
+++ b/drivers/cpufreq/cpufreq-dt.c
@@ -295,6 +295,21 @@ static int cpufreq_init(struct cpufreq_policy *policy)
 	return ret;
 }
 
+static int cpufreq_online(struct cpufreq_policy *policy)
+{
+	/* We did light-weight tear down earlier, nothing to do here */
+	return 0;
+}
+
+static int cpufreq_offline(struct cpufreq_policy *policy)
+{
+	/*
+	 * Preserve policy->driver_data and don't free resources on light-weight
+	 * tear down.
+	 */
+	return 0;
+}
+
 static int cpufreq_exit(struct cpufreq_policy *policy)
 {
 	struct private_data *priv = policy->driver_data;
@@ -319,6 +334,8 @@ static struct cpufreq_driver dt_cpufreq_driver = {
 	.get = cpufreq_generic_get,
 	.init = cpufreq_init,
 	.exit = cpufreq_exit,
+	.online = cpufreq_online,
+	.offline = cpufreq_offline,
 	.name = "cpufreq-dt",
 	.attr = cpufreq_dt_attr,
 	.suspend = cpufreq_generic_suspend,
-- 
2.20.1.321.g9e740568ce00

Re: [PATCH V2 2/2] cpufreq: dt: Implement online/offline() callbacks

[Rafael J. Wysocki]

On Tue, Feb 12, 2019 at 8:07 AM Viresh Kumar <viresh.kumar@linaro.org> wrote:
>
> Implement the light-weight tear down and bring up helpers to reduce the
> amount of work to do on CPU offline/online operation.
>
> Signed-off-by: Viresh Kumar <viresh.kumar@linaro.org>
> ---
>  drivers/cpufreq/cpufreq-dt.c | 17 +++++++++++++++++
>  1 file changed, 17 insertions(+)
>
> diff --git a/drivers/cpufreq/cpufreq-dt.c b/drivers/cpufreq/cpufreq-dt.c
> index 7ba392911cd0..1aefaa1b0ca2 100644
> --- a/drivers/cpufreq/cpufreq-dt.c
> +++ b/drivers/cpufreq/cpufreq-dt.c
> @@ -295,6 +295,21 @@ static int cpufreq_init(struct cpufreq_policy *policy)
>         return ret;
>  }
>
> +static int cpufreq_online(struct cpufreq_policy *policy)
> +{
> +       /* We did light-weight tear down earlier, nothing to do here */
> +       return 0;
> +}

I think you could avoid having to add this empty stub if the core
checked for both online and offline, that is

if (driver->offline || driver->online) {
    ret = driver->online ? driver->online(policy) : 0;
} else {
    ret = driver->init(policy);
}

or similar.

> +
> +static int cpufreq_offline(struct cpufreq_policy *policy)
> +{
> +       /*
> +        * Preserve policy->driver_data and don't free resources on light-weight
> +        * tear down.
> +        */
> +       return 0;
> +}
> +
>  static int cpufreq_exit(struct cpufreq_policy *policy)
>  {
>         struct private_data *priv = policy->driver_data;
> @@ -319,6 +334,8 @@ static struct cpufreq_driver dt_cpufreq_driver = {
>         .get = cpufreq_generic_get,
>         .init = cpufreq_init,
>         .exit = cpufreq_exit,
> +       .online = cpufreq_online,
> +       .offline = cpufreq_offline,
>         .name = "cpufreq-dt",
>         .attr = cpufreq_dt_attr,
>         .suspend = cpufreq_generic_suspend,
> --
> 2.20.1.321.g9e740568ce00
>

Re: [PATCH V2 2/2] cpufreq: dt: Implement online/offline() callbacks

[Viresh Kumar]

On 12-02-19, 10:43, Rafael J. Wysocki wrote:
> On Tue, Feb 12, 2019 at 8:07 AM Viresh Kumar <viresh.kumar@linaro.org> wrote:
> >
> > Implement the light-weight tear down and bring up helpers to reduce the
> > amount of work to do on CPU offline/online operation.
> >
> > Signed-off-by: Viresh Kumar <viresh.kumar@linaro.org>
> > ---
> >  drivers/cpufreq/cpufreq-dt.c | 17 +++++++++++++++++
> >  1 file changed, 17 insertions(+)
> >
> > diff --git a/drivers/cpufreq/cpufreq-dt.c b/drivers/cpufreq/cpufreq-dt.c
> > index 7ba392911cd0..1aefaa1b0ca2 100644
> > --- a/drivers/cpufreq/cpufreq-dt.c
> > +++ b/drivers/cpufreq/cpufreq-dt.c
> > @@ -295,6 +295,21 @@ static int cpufreq_init(struct cpufreq_policy *policy)
> >         return ret;
> >  }
> >
> > +static int cpufreq_online(struct cpufreq_policy *policy)
> > +{
> > +       /* We did light-weight tear down earlier, nothing to do here */
> > +       return 0;
> > +}
> 
> I think you could avoid having to add this empty stub if the core
> checked for both online and offline, that is
> 
> if (driver->offline || driver->online) {

This doesn't look great as all we should care about here is ->online()
and checking for offline as well looks a bit hacky.

>     ret = driver->online ? driver->online(policy) : 0;
> } else {
>     ret = driver->init(policy);
> }
> 
> or similar.

I also thought of a new flag like: CPUFREQ_LIGHT_WEIGHT_OFFLINE and
then we can get rid of both online/offline dummies but then thought of
starting with the dummy routines to begin with :)

-- 
viresh

Re: [PATCH V2 2/2] cpufreq: dt: Implement online/offline() callbacks

[Rafael J. Wysocki]

On Tue, Feb 12, 2019 at 10:49 AM Viresh Kumar <viresh.kumar@linaro.org> wrote:
>
> On 12-02-19, 10:43, Rafael J. Wysocki wrote:
> > On Tue, Feb 12, 2019 at 8:07 AM Viresh Kumar <viresh.kumar@linaro.org> wrote:
> > >
> > > Implement the light-weight tear down and bring up helpers to reduce the
> > > amount of work to do on CPU offline/online operation.
> > >
> > > Signed-off-by: Viresh Kumar <viresh.kumar@linaro.org>
> > > ---
> > >  drivers/cpufreq/cpufreq-dt.c | 17 +++++++++++++++++
> > >  1 file changed, 17 insertions(+)
> > >
> > > diff --git a/drivers/cpufreq/cpufreq-dt.c b/drivers/cpufreq/cpufreq-dt.c
> > > index 7ba392911cd0..1aefaa1b0ca2 100644
> > > --- a/drivers/cpufreq/cpufreq-dt.c
> > > +++ b/drivers/cpufreq/cpufreq-dt.c
> > > @@ -295,6 +295,21 @@ static int cpufreq_init(struct cpufreq_policy *policy)
> > >         return ret;
> > >  }
> > >
> > > +static int cpufreq_online(struct cpufreq_policy *policy)
> > > +{
> > > +       /* We did light-weight tear down earlier, nothing to do here */
> > > +       return 0;
> > > +}
> >
> > I think you could avoid having to add this empty stub if the core
> > checked for both online and offline, that is
> >
> > if (driver->offline || driver->online) {
>
> This doesn't look great as all we should care about here is ->online()
> and checking for offline as well looks a bit hacky.

That's a matter of the driver I/F definition.

You can require online to be there if offline is set and the other way
around (but then you should check if that's the case while registering
the driver) or you can allow just one of them to be provided for the
lightweight online/offline to be done.  In the latter case the
presence of the other callback plays the role of a flag.

Both are basically fine by me, but if you go for the former, please
add the checks to cpufreq_register_driver().

[PATCH V3 1/2] cpufreq: Allow light-weight tear down and bring up of CPUs

[Viresh Kumar]

The cpufreq core doesn't remove the cpufreq policy anymore on CPU
offline operation, rather that happens when the CPU device gets
unregistered from the kernel. This allows faster recovery when the CPU
comes back online. This is also very useful during system wide
suspend/resume where we offline all non-boot CPUs during suspend and
then bring them back on resume.

This commit takes the same idea a step ahead to allow drivers to do
light weight tear-down and bring-up during CPU offline and online
operations.

A new set of callbacks is introduced, online/offline(). online() gets
called when the first CPU of an inactive policy is brought up and
offline() gets called when all the CPUs of a policy are offlined.

The existing init/exit() callback get called on policy
creation/destruction. They also get called instead of online/offline()
callbacks if the online/offline() callbacks aren't provided.

This also moves around some code to get executed only for the new-policy
case going forward.

Signed-off-by: Viresh Kumar <viresh.kumar@linaro.org>
---
V2->V3:
- Additional check in cpufreq_register_driver().

 drivers/cpufreq/cpufreq.c | 58 +++++++++++++++++++++++++--------------
 include/linux/cpufreq.h   |  2 ++
 2 files changed, 40 insertions(+), 20 deletions(-)

diff --git a/drivers/cpufreq/cpufreq.c b/drivers/cpufreq/cpufreq.c
index 96a69c67a545..dd7626c5eb85 100644
--- a/drivers/cpufreq/cpufreq.c
+++ b/drivers/cpufreq/cpufreq.c
@@ -1201,28 +1201,39 @@ static int cpufreq_online(unsigned int cpu)
 			return -ENOMEM;
 	}
 
-	cpumask_copy(policy->cpus, cpumask_of(cpu));
+	if (!new_policy && cpufreq_driver->online) {
+		ret = cpufreq_driver->online(policy);
+		if (ret) {
+			pr_debug("%s: %d: initialization failed\n", __func__,
+				 __LINE__);
+			goto out_exit_policy;
+		}
 
-	/* call driver. From then on the cpufreq must be able
-	 * to accept all calls to ->verify and ->setpolicy for this CPU
-	 */
-	ret = cpufreq_driver->init(policy);
-	if (ret) {
-		pr_debug("initialization failed\n");
-		goto out_free_policy;
-	}
+		/* Recover policy->cpus using related_cpus */
+		cpumask_copy(policy->cpus, policy->related_cpus);
+	} else {
+		cpumask_copy(policy->cpus, cpumask_of(cpu));
 
-	ret = cpufreq_table_validate_and_sort(policy);
-	if (ret)
-		goto out_exit_policy;
+		/*
+		 * Call driver. From then on the cpufreq must be able
+		 * to accept all calls to ->verify and ->setpolicy for this CPU.
+		 */
+		ret = cpufreq_driver->init(policy);
+		if (ret) {
+			pr_debug("%s: %d: initialization failed\n", __func__,
+				 __LINE__);
+			goto out_free_policy;
+		}
 
-	down_write(&policy->rwsem);
+		ret = cpufreq_table_validate_and_sort(policy);
+		if (ret)
+			goto out_exit_policy;
 
-	if (new_policy) {
 		/* related_cpus should at least include policy->cpus. */
 		cpumask_copy(policy->related_cpus, policy->cpus);
 	}
 
+	down_write(&policy->rwsem);
 	/*
 	 * affected cpus must always be the one, which are online. We aren't
 	 * managing offline cpus here.
@@ -1421,11 +1432,12 @@ static int cpufreq_offline(unsigned int cpu)
 		cpufreq_exit_governor(policy);
 
 	/*
-	 * Perform the ->exit() even during light-weight tear-down,
-	 * since this is a core component, and is essential for the
-	 * subsequent light-weight ->init() to succeed.
+	 * Perform the ->offline() during light-weight tear-down, as
+	 * that allows fast recovery when the CPU comes back.
 	 */
-	if (cpufreq_driver->exit) {
+	if (cpufreq_driver->offline) {
+		cpufreq_driver->offline(policy);
+	} else if (cpufreq_driver->exit) {
 		cpufreq_driver->exit(policy);
 		policy->freq_table = NULL;
 	}
@@ -1454,8 +1466,13 @@ static void cpufreq_remove_dev(struct device *dev, struct subsys_interface *sif)
 	cpumask_clear_cpu(cpu, policy->real_cpus);
 	remove_cpu_dev_symlink(policy, dev);
 
-	if (cpumask_empty(policy->real_cpus))
+	if (cpumask_empty(policy->real_cpus)) {
+		/* We did light-weight exit earlier, do full tear down now */
+		if (cpufreq_driver->offline)
+			cpufreq_driver->exit(policy);
+
 		cpufreq_policy_free(policy);
+	}
 }
 
 /**
@@ -2488,7 +2505,8 @@ int cpufreq_register_driver(struct cpufreq_driver *driver_data)
 		    driver_data->target) ||
 	     (driver_data->setpolicy && (driver_data->target_index ||
 		    driver_data->target)) ||
-	     (!!driver_data->get_intermediate != !!driver_data->target_intermediate))
+	     (!!driver_data->get_intermediate != !!driver_data->target_intermediate) ||
+	     (!driver_data->online ^ !driver_data->offline))
 		return -EINVAL;
 
 	pr_debug("trying to register driver %s\n", driver_data->name);
diff --git a/include/linux/cpufreq.h b/include/linux/cpufreq.h
index 9db074ecbbd7..b160e98076e3 100644
--- a/include/linux/cpufreq.h
+++ b/include/linux/cpufreq.h
@@ -325,6 +325,8 @@ struct cpufreq_driver {
 	/* optional */
 	int		(*bios_limit)(int cpu, unsigned int *limit);
 
+	int		(*online)(struct cpufreq_policy *policy);
+	int		(*offline)(struct cpufreq_policy *policy);
 	int		(*exit)(struct cpufreq_policy *policy);
 	void		(*stop_cpu)(struct cpufreq_policy *policy);
 	int		(*suspend)(struct cpufreq_policy *policy);
-- 
2.20.1.321.g9e740568ce00

Re: [PATCH V3 1/2] cpufreq: Allow light-weight tear down and bring up of CPUs

[Rafael J. Wysocki]

On Tue, Feb 12, 2019 at 11:47 AM Viresh Kumar <viresh.kumar@linaro.org> wrote:
>

[cut]

> @@ -2488,7 +2505,8 @@ int cpufreq_register_driver(struct cpufreq_driver *driver_data)
>                     driver_data->target) ||
>              (driver_data->setpolicy && (driver_data->target_index ||
>                     driver_data->target)) ||
> -            (!!driver_data->get_intermediate != !!driver_data->target_intermediate))
> +            (!!driver_data->get_intermediate != !!driver_data->target_intermediate) ||
> +            (!driver_data->online ^ !driver_data->offline))

Why do you need the ^ here?  != should be sufficient:

!driver_data->online != !driver_data->offline

?

>                 return -EINVAL;
>
>         pr_debug("trying to register driver %s\n", driver_data->name);

[PATCH V4 1/2] cpufreq: Allow light-weight tear down and bring up of CPUs

[Viresh Kumar]

The cpufreq core doesn't remove the cpufreq policy anymore on CPU
offline operation, rather that happens when the CPU device gets
unregistered from the kernel. This allows faster recovery when the CPU
comes back online. This is also very useful during system wide
suspend/resume where we offline all non-boot CPUs during suspend and
then bring them back on resume.

This commit takes the same idea a step ahead to allow drivers to do
light weight tear-down and bring-up during CPU offline and online
operations.

A new set of callbacks is introduced, online/offline(). online() gets
called when the first CPU of an inactive policy is brought up and
offline() gets called when all the CPUs of a policy are offlined.

The existing init/exit() callback get called on policy
creation/destruction. They also get called instead of online/offline()
callbacks if the online/offline() callbacks aren't provided.

This also moves around some code to get executed only for the new-policy
case going forward.

Signed-off-by: Viresh Kumar <viresh.kumar@linaro.org>
---
V3->V4:
- Use != instead of ^

 drivers/cpufreq/cpufreq.c | 58 +++++++++++++++++++++++++--------------
 include/linux/cpufreq.h   |  2 ++
 2 files changed, 40 insertions(+), 20 deletions(-)

diff --git a/drivers/cpufreq/cpufreq.c b/drivers/cpufreq/cpufreq.c
index 96a69c67a545..55e9795801a4 100644
--- a/drivers/cpufreq/cpufreq.c
+++ b/drivers/cpufreq/cpufreq.c
@@ -1201,28 +1201,39 @@ static int cpufreq_online(unsigned int cpu)
 			return -ENOMEM;
 	}
 
-	cpumask_copy(policy->cpus, cpumask_of(cpu));
+	if (!new_policy && cpufreq_driver->online) {
+		ret = cpufreq_driver->online(policy);
+		if (ret) {
+			pr_debug("%s: %d: initialization failed\n", __func__,
+				 __LINE__);
+			goto out_exit_policy;
+		}
 
-	/* call driver. From then on the cpufreq must be able
-	 * to accept all calls to ->verify and ->setpolicy for this CPU
-	 */
-	ret = cpufreq_driver->init(policy);
-	if (ret) {
-		pr_debug("initialization failed\n");
-		goto out_free_policy;
-	}
+		/* Recover policy->cpus using related_cpus */
+		cpumask_copy(policy->cpus, policy->related_cpus);
+	} else {
+		cpumask_copy(policy->cpus, cpumask_of(cpu));
 
-	ret = cpufreq_table_validate_and_sort(policy);
-	if (ret)
-		goto out_exit_policy;
+		/*
+		 * Call driver. From then on the cpufreq must be able
+		 * to accept all calls to ->verify and ->setpolicy for this CPU.
+		 */
+		ret = cpufreq_driver->init(policy);
+		if (ret) {
+			pr_debug("%s: %d: initialization failed\n", __func__,
+				 __LINE__);
+			goto out_free_policy;
+		}
 
-	down_write(&policy->rwsem);
+		ret = cpufreq_table_validate_and_sort(policy);
+		if (ret)
+			goto out_exit_policy;
 
-	if (new_policy) {
 		/* related_cpus should at least include policy->cpus. */
 		cpumask_copy(policy->related_cpus, policy->cpus);
 	}
 
+	down_write(&policy->rwsem);
 	/*
 	 * affected cpus must always be the one, which are online. We aren't
 	 * managing offline cpus here.
@@ -1421,11 +1432,12 @@ static int cpufreq_offline(unsigned int cpu)
 		cpufreq_exit_governor(policy);
 
 	/*
-	 * Perform the ->exit() even during light-weight tear-down,
-	 * since this is a core component, and is essential for the
-	 * subsequent light-weight ->init() to succeed.
+	 * Perform the ->offline() during light-weight tear-down, as
+	 * that allows fast recovery when the CPU comes back.
 	 */
-	if (cpufreq_driver->exit) {
+	if (cpufreq_driver->offline) {
+		cpufreq_driver->offline(policy);
+	} else if (cpufreq_driver->exit) {
 		cpufreq_driver->exit(policy);
 		policy->freq_table = NULL;
 	}
@@ -1454,8 +1466,13 @@ static void cpufreq_remove_dev(struct device *dev, struct subsys_interface *sif)
 	cpumask_clear_cpu(cpu, policy->real_cpus);
 	remove_cpu_dev_symlink(policy, dev);
 
-	if (cpumask_empty(policy->real_cpus))
+	if (cpumask_empty(policy->real_cpus)) {
+		/* We did light-weight exit earlier, do full tear down now */
+		if (cpufreq_driver->offline)
+			cpufreq_driver->exit(policy);
+
 		cpufreq_policy_free(policy);
+	}
 }
 
 /**
@@ -2488,7 +2505,8 @@ int cpufreq_register_driver(struct cpufreq_driver *driver_data)
 		    driver_data->target) ||
 	     (driver_data->setpolicy && (driver_data->target_index ||
 		    driver_data->target)) ||
-	     (!!driver_data->get_intermediate != !!driver_data->target_intermediate))
+	     (!!driver_data->get_intermediate != !!driver_data->target_intermediate) ||
+	     (!driver_data->online != !driver_data->offline))
 		return -EINVAL;
 
 	pr_debug("trying to register driver %s\n", driver_data->name);
diff --git a/include/linux/cpufreq.h b/include/linux/cpufreq.h
index 9db074ecbbd7..b160e98076e3 100644
--- a/include/linux/cpufreq.h
+++ b/include/linux/cpufreq.h
@@ -325,6 +325,8 @@ struct cpufreq_driver {
 	/* optional */
 	int		(*bios_limit)(int cpu, unsigned int *limit);
 
+	int		(*online)(struct cpufreq_policy *policy);
+	int		(*offline)(struct cpufreq_policy *policy);
 	int		(*exit)(struct cpufreq_policy *policy);
 	void		(*stop_cpu)(struct cpufreq_policy *policy);
 	int		(*suspend)(struct cpufreq_policy *policy);
-- 
2.20.1.321.g9e740568ce00

Re: [PATCH V4 1/2] cpufreq: Allow light-weight tear down and bring up of CPUs

[Rafael J. Wysocki]

On Tuesday, February 12, 2019 12:06:04 PM CET Viresh Kumar wrote:
> The cpufreq core doesn't remove the cpufreq policy anymore on CPU
> offline operation, rather that happens when the CPU device gets
> unregistered from the kernel. This allows faster recovery when the CPU
> comes back online. This is also very useful during system wide
> suspend/resume where we offline all non-boot CPUs during suspend and
> then bring them back on resume.
> 
> This commit takes the same idea a step ahead to allow drivers to do
> light weight tear-down and bring-up during CPU offline and online
> operations.
> 
> A new set of callbacks is introduced, online/offline(). online() gets
> called when the first CPU of an inactive policy is brought up and
> offline() gets called when all the CPUs of a policy are offlined.
> 
> The existing init/exit() callback get called on policy
> creation/destruction. They also get called instead of online/offline()
> callbacks if the online/offline() callbacks aren't provided.
> 
> This also moves around some code to get executed only for the new-policy
> case going forward.
> 
> Signed-off-by: Viresh Kumar <viresh.kumar@linaro.org>
> ---
> V3->V4:
> - Use != instead of ^
> 
>  drivers/cpufreq/cpufreq.c | 58 +++++++++++++++++++++++++--------------
>  include/linux/cpufreq.h   |  2 ++
>  2 files changed, 40 insertions(+), 20 deletions(-)
> 
> diff --git a/drivers/cpufreq/cpufreq.c b/drivers/cpufreq/cpufreq.c
> index 96a69c67a545..55e9795801a4 100644
> --- a/drivers/cpufreq/cpufreq.c
> +++ b/drivers/cpufreq/cpufreq.c
> @@ -1201,28 +1201,39 @@ static int cpufreq_online(unsigned int cpu)
>  			return -ENOMEM;
>  	}
>  
> -	cpumask_copy(policy->cpus, cpumask_of(cpu));
> +	if (!new_policy && cpufreq_driver->online) {
> +		ret = cpufreq_driver->online(policy);
> +		if (ret) {
> +			pr_debug("%s: %d: initialization failed\n", __func__,
> +				 __LINE__);
> +			goto out_exit_policy;
> +		}
>  
> -	/* call driver. From then on the cpufreq must be able
> -	 * to accept all calls to ->verify and ->setpolicy for this CPU
> -	 */
> -	ret = cpufreq_driver->init(policy);
> -	if (ret) {
> -		pr_debug("initialization failed\n");
> -		goto out_free_policy;
> -	}
> +		/* Recover policy->cpus using related_cpus */
> +		cpumask_copy(policy->cpus, policy->related_cpus);
> +	} else {
> +		cpumask_copy(policy->cpus, cpumask_of(cpu));
>  
> -	ret = cpufreq_table_validate_and_sort(policy);
> -	if (ret)
> -		goto out_exit_policy;
> +		/*
> +		 * Call driver. From then on the cpufreq must be able
> +		 * to accept all calls to ->verify and ->setpolicy for this CPU.
> +		 */
> +		ret = cpufreq_driver->init(policy);
> +		if (ret) {
> +			pr_debug("%s: %d: initialization failed\n", __func__,
> +				 __LINE__);
> +			goto out_free_policy;
> +		}
>  
> -	down_write(&policy->rwsem);
> +		ret = cpufreq_table_validate_and_sort(policy);
> +		if (ret)
> +			goto out_exit_policy;
>  
> -	if (new_policy) {
>  		/* related_cpus should at least include policy->cpus. */
>  		cpumask_copy(policy->related_cpus, policy->cpus);
>  	}
>  
> +	down_write(&policy->rwsem);
>  	/*
>  	 * affected cpus must always be the one, which are online. We aren't
>  	 * managing offline cpus here.
> @@ -1421,11 +1432,12 @@ static int cpufreq_offline(unsigned int cpu)
>  		cpufreq_exit_governor(policy);
>  
>  	/*
> -	 * Perform the ->exit() even during light-weight tear-down,
> -	 * since this is a core component, and is essential for the
> -	 * subsequent light-weight ->init() to succeed.
> +	 * Perform the ->offline() during light-weight tear-down, as
> +	 * that allows fast recovery when the CPU comes back.
>  	 */
> -	if (cpufreq_driver->exit) {
> +	if (cpufreq_driver->offline) {
> +		cpufreq_driver->offline(policy);
> +	} else if (cpufreq_driver->exit) {
>  		cpufreq_driver->exit(policy);
>  		policy->freq_table = NULL;
>  	}
> @@ -1454,8 +1466,13 @@ static void cpufreq_remove_dev(struct device *dev, struct subsys_interface *sif)
>  	cpumask_clear_cpu(cpu, policy->real_cpus);
>  	remove_cpu_dev_symlink(policy, dev);
>  
> -	if (cpumask_empty(policy->real_cpus))
> +	if (cpumask_empty(policy->real_cpus)) {
> +		/* We did light-weight exit earlier, do full tear down now */
> +		if (cpufreq_driver->offline)
> +			cpufreq_driver->exit(policy);
> +
>  		cpufreq_policy_free(policy);
> +	}
>  }
>  
>  /**
> @@ -2488,7 +2505,8 @@ int cpufreq_register_driver(struct cpufreq_driver *driver_data)
>  		    driver_data->target) ||
>  	     (driver_data->setpolicy && (driver_data->target_index ||
>  		    driver_data->target)) ||
> -	     (!!driver_data->get_intermediate != !!driver_data->target_intermediate))
> +	     (!!driver_data->get_intermediate != !!driver_data->target_intermediate) ||
> +	     (!driver_data->online != !driver_data->offline))
>  		return -EINVAL;
>  
>  	pr_debug("trying to register driver %s\n", driver_data->name);
> diff --git a/include/linux/cpufreq.h b/include/linux/cpufreq.h
> index 9db074ecbbd7..b160e98076e3 100644
> --- a/include/linux/cpufreq.h
> +++ b/include/linux/cpufreq.h
> @@ -325,6 +325,8 @@ struct cpufreq_driver {
>  	/* optional */
>  	int		(*bios_limit)(int cpu, unsigned int *limit);
>  
> +	int		(*online)(struct cpufreq_policy *policy);
> +	int		(*offline)(struct cpufreq_policy *policy);
>  	int		(*exit)(struct cpufreq_policy *policy);
>  	void		(*stop_cpu)(struct cpufreq_policy *policy);
>  	int		(*suspend)(struct cpufreq_policy *policy);
> 

Applied along with the [2/2], thanks!