Re: [PATCH 1/4] ARM: dts: imx6qdl-sabrelite: add mdio phy address 0

[sashiko-bot@kernel.org]

Thank you for your contribution! Sashiko AI review found 1 potential issue(s) to consider:
- [High] Setting the Ethernet PHY `reg` property to the MDIO broadcast address (0) instead of the actual hardware-strapped address breaks Ethernet initialization on the SABRE Lite board.
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commit fbbd7813db5860f802e25f49f30fa7e2a33c20e6
Author: Frank Li <Frank.Li@nxp.com>
ARM: dts: imx6qdl-sabrelite: add mdio phy address 0

This commit explicitly sets the Ethernet PHY reg property to 0 to resolve
device tree schema validation warnings. It relies on the IEEE 802.3
specification indicating that a PHY should respond to the broadcast
address 0.

> diff --git a/arch/arm/boot/dts/nxp/imx/imx6qdl-sabrelite.dtsi b/arch/arm/boot/dts/nxp/imx/imx6qdl-sabrelite.dtsi
> --- a/arch/arm/boot/dts/nxp/imx/imx6qdl-sabrelite.dtsi
> +++ b/arch/arm/boot/dts/nxp/imx/imx6qdl-sabrelite.dtsi
> @@ -291,8 +291,9 @@ mdio {
>  		#address-cells = <1>;
>  		#size-cells = <0>;
>  
> -		ethphy: ethernet-phy {
> +		ethphy: ethernet-phy@0 {
>  			compatible = "ethernet-phy-ieee802.3-c22";
> +			reg = <0>;

Could this cause a regression in Ethernet functionality on the Sabre Lite
board?

The device tree should accurately describe the physical hardware topology,
but the Micrel KSZ9021 PHY on the Sabre Lite board is hardware-strapped to
address 6, not 0. Furthermore, the KSZ9021 datasheet indicates that it does
not support address 0 as a broadcast address.

Prior to this patch, the absence of a reg property caused
of_mdio_parse_addr() to return an error. This triggered an auto-probing
loop over all 32 addresses, which successfully found the PHY at address 6.

By explicitly defining reg = <0>, the kernel skips the auto-scanning
fallback and exclusively probes address 0. Because the PHY does not respond
to MDIO reads at address 0, get_phy_device() will read 0xFFFF and fail with
-ENODEV, preventing the PHY from registering.

Should this instead set the reg property to the actual hardware-strapped
address 6 to satisfy the schema without breaking initialization?

>  			txen-skew-ps = <0>;
>  			txc-skew-ps = <3000>;
>  			rxdv-skew-ps = <0>;

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Sashiko AI review · https://sashiko.dev/#/patchset/20260511-b4-imx25_dts_simple_warning-v1-0-01b855a5ce25@nxp.com?part=1