[PATCH] PM / Domains: Add pm_genpd_lookup() API to lookup domain by device node

[PATCH] PM / Domains: Add pm_genpd_lookup() API to lookup domain by device node

[Ulf Hansson]

In a step to move away from using genpd's name based APIs, such as the
pm_genpd_add_subdomain_names(), provide an API to lookup an already
initialized generic PM domain by its device node.

This API would typically be a called from SOC specific code, to fetch a
handle to the domain. Especially convenient to configure subdomains and
when the hierarchy of the domains are described in DT.

Do note, before pm_genpd_init() is invoked to initialize a generic PM
domain, it's the callers responsibility to assign the new ->dev_node
pointer in the struct generic_pm_domain, to enable pm_genpd_lookup() to
find the domain.

Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>
---

The background to why I propose this patch comes from a discussion around the
below patchset:
https://lkml.org/lkml/2014/11/24/290


---
 drivers/base/power/domain.c | 26 ++++++++++++++++++++++++++
 include/linux/pm_domain.h   |  2 ++
 2 files changed, 28 insertions(+)

diff --git a/drivers/base/power/domain.c b/drivers/base/power/domain.c
index 735c473..34555eb 100644
--- a/drivers/base/power/domain.c
+++ b/drivers/base/power/domain.c
@@ -75,6 +75,32 @@ struct generic_pm_domain *dev_to_genpd(struct device *dev)
 	return pd_to_genpd(dev->pm_domain);
 }
 
+/**
+ * pm_genpd_lookup - Fetch a generic PM domain object by device node
+ * @node: Device node to a corresponding genpd.
+ *
+ * Returns a valid pointer to struct generic_pm_domain on success or ERR_PTR()
+ * on failure.
+ */
+struct generic_pm_domain *pm_genpd_lookup(struct device_node *node)
+{
+	struct generic_pm_domain *genpd = ERR_PTR(-ENOENT), *gpd;
+
+	if (IS_ERR_OR_NULL(node))
+		return ERR_PTR(-EINVAL);
+
+	mutex_lock(&gpd_list_lock);
+	list_for_each_entry(gpd, &gpd_list, gpd_list_node) {
+		if (gpd->dev_node == node) {
+			genpd = gpd;
+			break;
+		}
+	}
+	mutex_unlock(&gpd_list_lock);
+	return genpd;
+}
+EXPORT_SYMBOL_GPL(pm_genpd_lookup);
+
 static int genpd_stop_dev(struct generic_pm_domain *genpd, struct device *dev)
 {
 	return GENPD_DEV_TIMED_CALLBACK(genpd, int, stop, dev,
diff --git a/include/linux/pm_domain.h b/include/linux/pm_domain.h
index 8cbd32e..322cb7c 100644
--- a/include/linux/pm_domain.h
+++ b/include/linux/pm_domain.h
@@ -53,6 +53,7 @@ struct generic_pm_domain {
 	struct dev_power_governor *gov;
 	struct work_struct power_off_work;
 	const char *name;
+	struct device_node *dev_node;	/* Device node for the PM domain */
 	unsigned int in_progress;	/* Number of devices being suspended now */
 	atomic_t sd_count;	/* Number of subdomains with power "on" */
 	enum gpd_status status;	/* Current state of the domain */
@@ -126,6 +127,7 @@ static inline struct generic_pm_domain_data *dev_gpd_data(struct device *dev)
 }
 
 extern struct generic_pm_domain *dev_to_genpd(struct device *dev);
+extern struct generic_pm_domain *pm_genpd_lookup(struct device_node *node);
 extern int __pm_genpd_add_device(struct generic_pm_domain *genpd,
 				 struct device *dev,
 				 struct gpd_timing_data *td);
-- 
1.9.1

[PATCH] PM / Domains: Add pm_genpd_lookup() API to lookup domain by device node

[Rafael J. Wysocki]

On Thursday, November 27, 2014 03:14:13 PM Ulf Hansson wrote:
> In a step to move away from using genpd's name based APIs, such as the
> pm_genpd_add_subdomain_names(), provide an API to lookup an already
> initialized generic PM domain by its device node.
> 
> This API would typically be a called from SOC specific code, to fetch a
> handle to the domain. Especially convenient to configure subdomains and
> when the hierarchy of the domains are described in DT.
> 
> Do note, before pm_genpd_init() is invoked to initialize a generic PM
> domain, it's the callers responsibility to assign the new ->dev_node
> pointer in the struct generic_pm_domain, to enable pm_genpd_lookup() to
> find the domain.
> 
> Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>
> ---
> 
> The background to why I propose this patch comes from a discussion around the
> below patchset:
> https://lkml.org/lkml/2014/11/24/290
> 
> 
> ---
>  drivers/base/power/domain.c | 26 ++++++++++++++++++++++++++
>  include/linux/pm_domain.h   |  2 ++
>  2 files changed, 28 insertions(+)
> 
> diff --git a/drivers/base/power/domain.c b/drivers/base/power/domain.c
> index 735c473..34555eb 100644
> --- a/drivers/base/power/domain.c
> +++ b/drivers/base/power/domain.c
> @@ -75,6 +75,32 @@ struct generic_pm_domain *dev_to_genpd(struct device *dev)
>  	return pd_to_genpd(dev->pm_domain);
>  }
>  
> +/**
> + * pm_genpd_lookup - Fetch a generic PM domain object by device node
> + * @node: Device node to a corresponding genpd.
> + *
> + * Returns a valid pointer to struct generic_pm_domain on success or ERR_PTR()
> + * on failure.
> + */
> +struct generic_pm_domain *pm_genpd_lookup(struct device_node *node)
> +{
> +	struct generic_pm_domain *genpd = ERR_PTR(-ENOENT), *gpd;
> +
> +	if (IS_ERR_OR_NULL(node))
> +		return ERR_PTR(-EINVAL);
> +
> +	mutex_lock(&gpd_list_lock);
> +	list_for_each_entry(gpd, &gpd_list, gpd_list_node) {
> +		if (gpd->dev_node == node) {
> +			genpd = gpd;
> +			break;
> +		}
> +	}
> +	mutex_unlock(&gpd_list_lock);
> +	return genpd;
> +}
> +EXPORT_SYMBOL_GPL(pm_genpd_lookup);
> +
>  static int genpd_stop_dev(struct generic_pm_domain *genpd, struct device *dev)
>  {
>  	return GENPD_DEV_TIMED_CALLBACK(genpd, int, stop, dev,
> diff --git a/include/linux/pm_domain.h b/include/linux/pm_domain.h
> index 8cbd32e..322cb7c 100644
> --- a/include/linux/pm_domain.h
> +++ b/include/linux/pm_domain.h
> @@ -53,6 +53,7 @@ struct generic_pm_domain {
>  	struct dev_power_governor *gov;
>  	struct work_struct power_off_work;
>  	const char *name;
> +	struct device_node *dev_node;	/* Device node for the PM domain */

Please don't add DT-specific members to generic data structures.

You can use struct fwnode_handle (currently in linux-next) instead.

>  	unsigned int in_progress;	/* Number of devices being suspended now */
>  	atomic_t sd_count;	/* Number of subdomains with power "on" */
>  	enum gpd_status status;	/* Current state of the domain */
> @@ -126,6 +127,7 @@ static inline struct generic_pm_domain_data *dev_gpd_data(struct device *dev)
>  }
>  
>  extern struct generic_pm_domain *dev_to_genpd(struct device *dev);
> +extern struct generic_pm_domain *pm_genpd_lookup(struct device_node *node);
>  extern int __pm_genpd_add_device(struct generic_pm_domain *genpd,
>  				 struct device *dev,
>  				 struct gpd_timing_data *td);
> 

-- 
I speak only for myself.
Rafael J. Wysocki, Intel Open Source Technology Center.