PM / Domains: Introduce a genpd OF helper that removes a subdomain

We already have the of_genpd_add_subdomain() helper, but no corresponding
of_genpd_remove_subdomain(), so let's add it. Subsequent changes starts to
make use of it.
Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>
Acked-by: Rafael J. Wysocki <rafael@kernel.org>

drivers/base/power/domain.c

@@ -2302,6 +2302,44 @@ int of_genpd_add_subdomain(struct of_phandle_args *parent_spec,
 }
 EXPORT_SYMBOL_GPL(of_genpd_add_subdomain);
 
+/**
+ * of_genpd_remove_subdomain - Remove a subdomain from an I/O PM domain.
+ * @parent_spec: OF phandle args to use for parent PM domain look-up
+ * @subdomain_spec: OF phandle args to use for subdomain look-up
+ *
+ * Looks-up a parent PM domain and subdomain based upon phandle args
+ * provided and removes the subdomain from the parent PM domain. Returns a
+ * negative error code on failure.
+ */
+int of_genpd_remove_subdomain(struct of_phandle_args *parent_spec,
+			      struct of_phandle_args *subdomain_spec)
+{
+	struct generic_pm_domain *parent, *subdomain;
+	int ret;
+
+	mutex_lock(&gpd_list_lock);
+
+	parent = genpd_get_from_provider(parent_spec);
+	if (IS_ERR(parent)) {
+		ret = PTR_ERR(parent);
+		goto out;
+	}
+
+	subdomain = genpd_get_from_provider(subdomain_spec);
+	if (IS_ERR(subdomain)) {
+		ret = PTR_ERR(subdomain);
+		goto out;
+	}
+
+	ret = pm_genpd_remove_subdomain(parent, subdomain);
+
+out:
+	mutex_unlock(&gpd_list_lock);
+
+	return ret;
+}
+EXPORT_SYMBOL_GPL(of_genpd_remove_subdomain);
+
 /**
  * of_genpd_remove_last - Remove the last PM domain registered for a provider
  * @provider: Pointer to device structure associated with provider

include/linux/pm_domain.h

@@ -284,6 +284,8 @@ void of_genpd_del_provider(struct device_node *np);
 int of_genpd_add_device(struct of_phandle_args *args, struct device *dev);
 int of_genpd_add_subdomain(struct of_phandle_args *parent_spec,
 			   struct of_phandle_args *subdomain_spec);
+int of_genpd_remove_subdomain(struct of_phandle_args *parent_spec,
+			      struct of_phandle_args *subdomain_spec);
 struct generic_pm_domain *of_genpd_remove_last(struct device_node *np);
 int of_genpd_parse_idle_states(struct device_node *dn,
 			       struct genpd_power_state **states, int *n);
@@ -322,6 +324,12 @@ static inline int of_genpd_add_subdomain(struct of_phandle_args *parent_spec,
 	return -ENODEV;
 }
 
+static inline int of_genpd_remove_subdomain(struct of_phandle_args *parent_spec,
+					struct of_phandle_args *subdomain_spec)
+{
+	return -ENODEV;
+}
+
 static inline int of_genpd_parse_idle_states(struct device_node *dn,
 			struct genpd_power_state **states, int *n)
 {