Re: [RFC PATCH net-next v4 23/28] net: dsa: register of_mdiobus if a mdio node is declared

Some switch have phy port that use the internal switch mdio bus and can
have different phy regs than the one declared in the ports node. Add
support for this specific case by registering the mdiobus with the mdio
node and permit the port to declare a phy-handle defined inside the
switch node.

This is an example from the qca8337 switch where the 5 phy port should
use the internal mdiobus and would benefits from this.

switch10: switch@10 {
        compatible = "qca,qca8337";
        #address-cells = <1>;
        #size-cells = <0>;
        reg = <0x10>;

        ports {
                #address-cells = <1>;
                #size-cells = <0>;

                port@0 {
                        reg = <0>;
                        label = "cpu";
                        ethernet = <&gmac1>;
                        phy-mode = "rgmii-id";

                        fixed-link {
                                speed = <1000>;
                                full-duplex;
                        };
                };

                port@1 {
                        reg = <1>;
                        label = "lan1";

                        phy-handle = <&phy_port0>;
                        phy-mode = "internal";
                };

                port@2 {
                        reg = <2>;
                        label = "lan2";

                        phy-handle = <&phy_port1>;
                        phy-mode = "internal";
                };

                port@3 {
                        reg = <3>;
                        label = "lan3";

                        phy-handle = <&phy_port2>;
                        phy-mode = "internal";
                };

                port@4 {
                        reg = <4>;
                        label = "lan4";

                        phy-handle = <&phy_port3>;
                        phy-mode = "internal";
                };

                port@5 {
                        reg = <5>;
                        label = "wan";

                        phy-handle = <&phy_port4>;
                        phy-mode = "internal";
                };

                port@6 {
                        reg = <6>;
                        label = "cpu";
                        ethernet = <&gmac2>;
                        phy-mode = "sgmii";

                        fixed-link {
                                        speed = <1000>;
                                        full-duplex;
                        };
                };
        };

        mdio {
                #address-cells = <1>;
                #size-cells = <0>;

                phy_port0: phy@0 {
                        reg = <0>;
                };

                phy_port1: phy@1 {
                        reg = <1>;
                };

                phy_port2: phy@2 {
                        reg = <2>;
                };

                phy_port3: phy@3 {
                        reg = <3>;
                };

                phy_port4: phy@4 {
                        reg = <4>;
                };
        };
};

Signed-off-by: Ansuel Smith <ansuelsmth@gmail.com>
---
 net/dsa/dsa2.c | 13 ++++++++++++-
 1 file changed, 12 insertions(+), 1 deletion(-)

diff --git a/net/dsa/dsa2.c b/net/dsa/dsa2.c
index 3c3e56a1f34d..79adabe3e2a7 100644
--- a/net/dsa/dsa2.c
+++ b/net/dsa/dsa2.c

@@ -14,6 +14,7 @@
 #include <linux/rtnetlink.h>
 #include <linux/of.h>
 #include <linux/of_net.h>
+#include <linux/of_mdio.h>
 #include <net/devlink.h>
 
 #include "dsa_priv.h"

@@ -721,6 +722,8 @@ static int dsa_switch_setup(struct dsa_switch *ds)
 	devlink_params_publish(ds->devlink);
 
 	if (!ds->slave_mii_bus && ds->ops->phy_read) {
+		struct device_node *mdio;
+
 		ds->slave_mii_bus = devm_mdiobus_alloc(ds->dev);
 		if (!ds->slave_mii_bus) {
 			err = -ENOMEM;

@@ -729,7 +732,15 @@ static int dsa_switch_setup(struct dsa_switch *ds)
 
 		dsa_slave_mii_bus_init(ds);
 
-		err = mdiobus_register(ds->slave_mii_bus);
+		mdio = of_get_child_by_name(ds->dev->of_node, "mdio");
+
+		if (mdio) {