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 firmware 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 ->fwnode
pointer in the struct generic_pm_domain, to enable pm_genpd_lookup() to
find the domain.

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

Changes in v2:
        Change from using struct device_node to struct fwnode_handle.
        Updated commit header accordingly.

---
 drivers/base/power/domain.c | 27 +++++++++++++++++++++++++++
 include/linux/pm_domain.h   |  4 ++++
 2 files changed, 31 insertions(+)

diff --git a/drivers/base/power/domain.c b/drivers/base/power/domain.c
index 735c473..2d881d5 100644
--- a/drivers/base/power/domain.c
+++ b/drivers/base/power/domain.c
@@ -75,6 +75,33 @@ 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 firmware node.
+ * @node: Firmware 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 fwnode_handle *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->fwnode == 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..aa01050 100644
--- a/include/linux/pm_domain.h
+++ b/include/linux/pm_domain.h
@@ -43,6 +43,8 @@ struct gpd_cpuidle_data {
        struct cpuidle_state *idle_state;
 };
 
+struct fwnode_handle;
+
 struct generic_pm_domain {
        struct dev_pm_domain domain;    /* PM domain operations */
        struct list_head gpd_list_node; /* Node in the global PM domains list */
@@ -53,6 +55,7 @@ struct generic_pm_domain {
        struct dev_power_governor *gov;
        struct work_struct power_off_work;
        const char *name;
+       struct fwnode_handle *fwnode;   /* Firware 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 +129,7 @@ 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 fwnode_handle *node);
 extern int __pm_genpd_add_device(struct generic_pm_domain *genpd,
                                 struct device *dev,
                                 struct gpd_timing_data *td);
-- 
1.9.1

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