Extend the DPLL core to support associating a DPLL pin with a firmware
node. This association is required to allow other subsystems (such as
network drivers) to locate and request specific DPLL pins defined in
the Device Tree or ACPI.

* Add a .fwnode field to the struct dpll_pin
* Introduce dpll_pin_fwnode_set() helper to allow the provider driver
  to associate a pin with a fwnode after the pin has been allocated
* Introduce fwnode_dpll_pin_find() helper to allow consumers to search
  for a registered DPLL pin using its associated fwnode handle
* Ensure the fwnode reference is properly released in dpll_pin_put()

Signed-off-by: Ivan Vecera <ivecera@redhat.com>
---
Changes:
RFC v2:
- dpll_pin_fwnode_set() helper to set firmware node without touching
  dpll_pin_get()
---
 drivers/dpll/dpll_core.c | 49 ++++++++++++++++++++++++++++++++++++++++
 drivers/dpll/dpll_core.h |  2 ++
 include/linux/dpll.h     | 11 +++++++++
 3 files changed, 62 insertions(+)

diff --git a/drivers/dpll/dpll_core.c b/drivers/dpll/dpll_core.c
index a461095efd8ac..fb68b5e19b480 100644
--- a/drivers/dpll/dpll_core.c
+++ b/drivers/dpll/dpll_core.c
@@ -10,6 +10,7 @@
 
 #include <linux/device.h>
 #include <linux/err.h>
+#include <linux/property.h>
 #include <linux/slab.h>
 #include <linux/string.h>
 
@@ -599,12 +600,60 @@ void dpll_pin_put(struct dpll_pin *pin)
 		xa_destroy(&pin->parent_refs);
 		xa_destroy(&pin->ref_sync_pins);
 		dpll_pin_prop_free(&pin->prop);
+		fwnode_handle_put(pin->fwnode);
 		kfree_rcu(pin, rcu);
 	}
 	mutex_unlock(&dpll_lock);
 }
 EXPORT_SYMBOL_GPL(dpll_pin_put);
 
+/**
+ * dpll_pin_fwnode_set - set dpll pin firmware node reference
+ * @pin: pointer to a dpll pin
+ * @fwnode: firmware node handle
+ *
+ * Set firmware node handle for the given dpll pin.
+ */
+void dpll_pin_fwnode_set(struct dpll_pin *pin, struct fwnode_handle *fwnode)
+{
+	mutex_lock(&dpll_lock);
+	fwnode_handle_put(pin->fwnode); /* Drop fwnode previously set */
+	pin->fwnode = fwnode_handle_get(fwnode);
+	mutex_unlock(&dpll_lock);
+}
+EXPORT_SYMBOL_GPL(dpll_pin_fwnode_set);
+
+/**
+ * fwnode_dpll_pin_find - find dpll pin by firmware node reference
+ * @fwnode: reference to firmware node
+ *
+ * Get existing object of a pin that is associated with given firmware node
+ * reference.
+ *
+ * Context: Acquires a lock (dpll_lock)
+ * Return:
+ * * valid dpll_pin struct pointer if succeeded
+ * * ERR_PTR(X) - error
+ */
+struct dpll_pin *fwnode_dpll_pin_find(struct fwnode_handle *fwnode)
+{
+	struct dpll_pin *pin, *ret = NULL;
+	unsigned long index;
+
+	mutex_lock(&dpll_lock);
+	xa_for_each(&dpll_pin_xa, index, pin) {
+		if (pin->fwnode == fwnode) {
+			ret = pin;
+			refcount_inc(&ret->refcount);
+			break;
+		}
+	}
+	mutex_unlock(&dpll_lock);
+
+	return ret;
+}
+EXPORT_SYMBOL_GPL(fwnode_dpll_pin_find);
+
 static int
 __dpll_pin_register(struct dpll_device *dpll, struct dpll_pin *pin,
 		    const struct dpll_pin_ops *ops, void *priv, void *cookie)
diff --git a/drivers/dpll/dpll_core.h b/drivers/dpll/dpll_core.h
index 8ce969bbeb64e..d3e17ff0ecef0 100644
--- a/drivers/dpll/dpll_core.h
+++ b/drivers/dpll/dpll_core.h
@@ -42,6 +42,7 @@ struct dpll_device {
  * @pin_idx:		index of a pin given by dev driver
  * @clock_id:		clock_id of creator
  * @module:		module of creator
+ * @fwnode:		optional reference to firmware node
  * @dpll_refs:		hold referencees to dplls pin was registered with
  * @parent_refs:	hold references to parent pins pin was registered with
  * @ref_sync_pins:	hold references to pins for Reference SYNC feature
@@ -54,6 +55,7 @@ struct dpll_pin {
 	u32 pin_idx;
 	u64 clock_id;
 	struct module *module;
+	struct fwnode_handle *fwnode;
 	struct xarray dpll_refs;
 	struct xarray parent_refs;
 	struct xarray ref_sync_pins;
diff --git a/include/linux/dpll.h b/include/linux/dpll.h
index 562f520b23c27..f0c31a111c304 100644
--- a/include/linux/dpll.h
+++ b/include/linux/dpll.h
@@ -16,6 +16,7 @@
 struct dpll_device;
 struct dpll_pin;
 struct dpll_pin_esync;
+struct fwnode_handle;
 
 struct dpll_device_ops {
 	int (*mode_get)(const struct dpll_device *dpll, void *dpll_priv,
@@ -173,6 +174,8 @@ void dpll_netdev_pin_clear(struct net_device *dev);
 size_t dpll_netdev_pin_handle_size(const struct net_device *dev);
 int dpll_netdev_add_pin_handle(struct sk_buff *msg,
 			       const struct net_device *dev);
+
+struct dpll_pin *fwnode_dpll_pin_find(struct fwnode_handle *fwnode);
 #else
 static inline void
 dpll_netdev_pin_set(struct net_device *dev, struct dpll_pin *dpll_pin) { }
@@ -188,6 +191,12 @@ dpll_netdev_add_pin_handle(struct sk_buff *msg, const struct net_device *dev)
 {
 	return 0;
 }
+
+static inline struct dpll_pin *
+fwnode_dpll_pin_find(struct fwnode_handle *fwnode)
+{
+	return NULL;
+}
 #endif
 
 struct dpll_device *
@@ -213,6 +222,8 @@ void dpll_pin_unregister(struct dpll_device *dpll, struct dpll_pin *pin,
 
 void dpll_pin_put(struct dpll_pin *pin);
 
+void dpll_pin_fwnode_set(struct dpll_pin *pin, struct fwnode_handle *fwnode);
+
 int dpll_pin_on_pin_register(struct dpll_pin *parent, struct dpll_pin *pin,
 			     const struct dpll_pin_ops *ops, void *priv);
 
-- 
2.51.2