[PATCH net-next v2 03/12] dpll: Add helpers to find DPLL pin fwnode

[Ivan Vecera <ivecera@redhat.com>]

dpll: core: add helpers to find DPLL pin fwnode

Add helper functions to the DPLL core to retrieve a DPLL pin's firmware
node handle based on the 'dpll-pins' and 'dpll-pin-names' properties.

Unlike simple phandle arrays, 'dpll-pins' entries typically contain
a pin specifier (index and direction) as defined by '#dpll-pin-cells'.
The new helper fwnode_dpll_pin_node_get() parses these specifiers
using fwnode_property_get_reference_args(). It resolves the target
pin by:
1. Identifying the DPLL device node from the phandle.
2. Selecting the correct sub-node ('input-pins' or 'output-pins') based
   on the direction argument.
3. Matching the pin index argument against the 'reg' property of
   the child nodes.

Additionally, register 'dpll-pins' in drivers/of/property.c to enable
proper parsing of the supplier bindings by the OF core.

Signed-off-by: Ivan Vecera <ivecera@redhat.com>
---
v2:
* added check for fwnode_property_match_string() return value
* reworked searching for the pin using dpll device phandle and
  pin specifier
* added dpll-pins into OF core supplier_bindings
---
 drivers/dpll/dpll_core.c | 74 ++++++++++++++++++++++++++++++++++++++++
 drivers/of/property.c    |  2 ++
 include/linux/dpll.h     | 15 ++++++++
 3 files changed, 91 insertions(+)

diff --git a/drivers/dpll/dpll_core.c b/drivers/dpll/dpll_core.c
index fb68b5e19b480..b0083b5c10aa4 100644
--- a/drivers/dpll/dpll_core.c
+++ b/drivers/dpll/dpll_core.c
@@ -13,6 +13,7 @@
 #include <linux/property.h>
 #include <linux/slab.h>
 #include <linux/string.h>
+#include <dt-bindings/dpll/dpll.h>
 
 #include "dpll_core.h"
 #include "dpll_netlink.h"
@@ -654,6 +655,79 @@ struct dpll_pin *fwnode_dpll_pin_find(struct fwnode_handle *fwnode)
 }
 EXPORT_SYMBOL_GPL(fwnode_dpll_pin_find);
 
+/**
+ * fwnode_dpll_pin_node_get - get dpll pin node from given fw node and pin name
+ * @fwnode: firmware node that uses the dpll pin
+ * @name: dpll pin name from dpll-pin-names property
+ *
+ * Return: ERR_PTR() on error or a valid firmware node handle on success.
+ */
+struct fwnode_handle *fwnode_dpll_pin_node_get(struct fwnode_handle *fwnode,
+					       const char *name)
+{
+	struct fwnode_handle *parent_node, *pin_node;
+	struct fwnode_reference_args args;
+	const char *parent_name;
+	int ret, index = 0;
+
+	if (name) {
+		index = fwnode_property_match_string(fwnode, "dpll-pin-names",
+						     name);
+		if (index < 0)
+			return ERR_PTR(-ENOENT);
+	}
+
+	ret = fwnode_property_get_reference_args(fwnode, "dpll-pins",
+						 "#dpll-pin-cells", 2, index,
+						 &args);
+	if (ret)
+		return ERR_PTR(ret);
+
+	/* We support only 2 cell DPLL bindings in the kernel currently. */
+	if (args.nargs != 2) {
+		fwnode_handle_put(args.fwnode);
+		return ERR_PTR(-ENOENT);
+	}
+
+	/* Resolve parent node name according pin direction type */
+	switch (args.args[1]) {
+	case DPLL_PIN_INPUT:
+		parent_name = "input-pins";
+		break;
+	case DPLL_PIN_OUTPUT:
+		parent_name = "output-pins";
+		break;
+	default:
+		fwnode_handle_put(args.fwnode);
+		return ERR_PTR(-EINVAL);
+	}
+
+	/* Get pin's parent sub-node */
+	parent_node = fwnode_get_named_child_node(args.fwnode, parent_name);
+	if (!parent_node) {
+		fwnode_handle_put(args.fwnode);
+		return ERR_PTR(-ENOENT);
+	}
+
+	/* Enumerate child pin nodes and find the requested one */
+	fwnode_for_each_child_node(parent_node, pin_node) {
+		u32 reg;
+
+		if (fwnode_property_read_u32(pin_node, "reg", &reg))
+			continue;
+
+		if (reg == args.args[0])
+			break;
+	}
+
+	/* Release pin's parent and dpll device node */
+	fwnode_handle_put(parent_node);
+	fwnode_handle_put(args.fwnode);
+
+	return pin_node ? pin_node : ERR_PTR(-ENOENT);
+}
+EXPORT_SYMBOL_GPL(fwnode_dpll_pin_node_get);
+
 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/of/property.c b/drivers/of/property.c
index 4e3524227720a..8571c8bb71ade 100644
--- a/drivers/of/property.c
+++ b/drivers/of/property.c
@@ -1410,6 +1410,7 @@ DEFINE_SIMPLE_PROP(post_init_providers, "post-init-providers", NULL)
 DEFINE_SIMPLE_PROP(access_controllers, "access-controllers", "#access-controller-cells")
 DEFINE_SIMPLE_PROP(pses, "pses", "#pse-cells")
 DEFINE_SIMPLE_PROP(power_supplies, "power-supplies", NULL)
+DEFINE_SIMPLE_PROP(dpll_pins, "dpll-pins", "#dpll-pin-cells")
 DEFINE_SUFFIX_PROP(regulators, "-supply", NULL)
 DEFINE_SUFFIX_PROP(gpio, "-gpio", "#gpio-cells")
 
@@ -1568,6 +1569,7 @@ static const struct supplier_bindings of_supplier_bindings[] = {
 		.parse_prop = parse_post_init_providers,
 		.fwlink_flags = FWLINK_FLAG_IGNORE,
 	},
+	{ .parse_prop = parse_dpll_pins, },
 	{}
 };
 
diff --git a/include/linux/dpll.h b/include/linux/dpll.h
index f0c31a111c304..755c36d1ef45a 100644
--- a/include/linux/dpll.h
+++ b/include/linux/dpll.h
@@ -11,6 +11,7 @@
 #include <linux/device.h>
 #include <linux/netlink.h>
 #include <linux/netdevice.h>
+#include <linux/property.h>
 #include <linux/rtnetlink.h>
 
 struct dpll_device;
@@ -176,6 +177,8 @@ 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);
+struct fwnode_handle *fwnode_dpll_pin_node_get(struct fwnode_handle *fwnode,
+					       const char *name);
 #else
 static inline void
 dpll_netdev_pin_set(struct net_device *dev, struct dpll_pin *dpll_pin) { }
@@ -197,8 +200,20 @@ fwnode_dpll_pin_find(struct fwnode_handle *fwnode)
 {
 	return NULL;
 }
+
+static inline struct fwnode_handle *
+fwnode_dpll_pin_node_get(struct fwnode_handle *fwnode, const char *name)
+{
+	return NULL;
+}
 #endif
 
+static inline struct fwnode_handle *
+device_dpll_pin_node_get(struct device *dev, const char *name)
+{
+	return fwnode_dpll_pin_node_get(dev_fwnode(dev), name);
+}
+
 struct dpll_device *
 dpll_device_get(u64 clock_id, u32 dev_driver_id, struct module *module);
 
-- 
2.52.0