[RFC PATCH] arm64: dts: rockchip: H28K: release RTL8211F reset before MDIO probing

arm64: dts: rockchip: H28K: release RTL8211F reset before MDIO probing

The RTL8211F on the HINLINK H28K (RK3528) is held in reset at power-on:
its reset line (gpio4 RK_PC2, pin 146) is left unconfigured and reads
low. The PHY node's reset-gpios are only acted upon after the PHY has
been found on MDIO (fwnode_mdiobus_register_phy() reads the PHY ID
before it requests and toggles the reset GPIO), so the first probe
deadlocks and eth0 never gets a link:

    mdio_bus stmmac-0: MDIO device at address 1 is missing.
    rk_gmac-dwmac ffbe0000.ethernet eth0: cannot attach to PHY (error: -ENODEV)

Release the reset from the MAC node via snps,reset-gpios so it is
deasserted before MDIO scanning, and drop the PHY-node reset-gpios (a
second consumer on the same GPIO is rejected with -EBUSY).

This is an RFC: snps,reset-gpios is deprecated in favour of the
ethernet-PHY reset bindings, so feedback on the preferred way to release
the reset early is welcome.

Fixes: 145d4af4b204 ("arm64: dts: rockchip: Add HINLINK H28K")
Signed-off-by: Zhyi <[email protected]>
---
diff --git a/arch/arm64/boot/dts/rockchip/rk3528-hinlink-h28k.dts b/arch/arm64/boot/dts/rockchip/rk3528-hinlink-h28k.dts
index 0ec50e9..9d7e33a 100644
--- a/arch/arm64/boot/dts/rockchip/rk3528-hinlink-h28k.dts
+++ b/arch/arm64/boot/dts/rockchip/rk3528-hinlink-h28k.dts
@@ -191,6 +191,8 @@
 		    <&rgmii_rx_bus2>,
 		    <&rgmii_rgmii_clk>,
 		    <&rgmii_rgmii_bus>;
+	snps,reset-gpios = <&gpio4 RK_PC2 GPIO_ACTIVE_LOW>;
+	snps,reset-delays-us = <0 20000 100000>;
 	status = "okay";
 };
 
@@ -205,9 +207,6 @@
 		reg = <0x1>;
 		pinctrl-names = "default";
 		pinctrl-0 = <&gmac1_rstn_l>;
-		reset-assert-us = <20000>;
-		reset-deassert-us = <100000>;
-		reset-gpios = <&gpio4 RK_PC2 GPIO_ACTIVE_LOW>;
 	};
 };