Re: [PATCH 1/2] arm64: dts: meson-gxbb-odroidc2: read the Ethernet MAC address from eFuse

[sashiko-bot@kernel.org]

Thank you for your contribution! Sashiko AI review found 1 potential issue(s) to consider:
- [Medium] net: of_get_mac_address_nvmem() fails due to 16-byte cell
--

commit 33c286acfab990fb62603385b64de76b3bd20dfe
Author: Fil Dunsky <filipp.dunsky@gmail.com>

arm64: dts: meson-gxbb-odroidc2: read the Ethernet MAC address from eFuse

This commit updates the meson-gxbb-odroidc2 device tree to read the Ethernet
MAC address from the eFuse nvmem cell instead of relying on the bootloader.
It links the ethmac node to the existing eth_mac nvmem cell using standard
properties.

> diff --git a/arch/arm64/boot/dts/amlogic/meson-gxbb-odroidc2.dts b/arch/arm64/boot/dts/amlogic/meson-gxbb-odroidc2.dts
> index 5943bc810678e..639b97ad515c0 100644
> --- a/arch/arm64/boot/dts/amlogic/meson-gxbb-odroidc2.dts
> +++ b/arch/arm64/boot/dts/amlogic/meson-gxbb-odroidc2.dts
> @@ -230,6 +230,9 @@ &ethmac {
>  	phy-handle = <&eth_phy0>;
>  	phy-mode = "rgmii";
>  
> +	nvmem-cells = <&eth_mac>;
> +	nvmem-cell-names = "mac-address";

[Severity: Medium]
Will this actually read the MAC address successfully? The network core strict
checks nvmem cells for MAC addresses to ensure they are exactly 6 bytes.

Looking at the eth_mac node defined in meson-gx.dtsi:

		eth_mac: eth-mac@34 {
			reg = <0x34 0x10>;
		};

This cell has a length of 16 bytes (0x10).

When the stmmac driver probes, it eventually calls of_get_mac_address_nvmem()
in net/core/of_net.c, which enforces this check:

	if (len != ETH_ALEN || !is_valid_ether_addr(mac)) {
		kfree(mac);
		return -EINVAL;
	}

Because 16 does not equal ETH_ALEN, this unconditionally returns -EINVAL. It
seems the driver will fall back to a bootloader-programmed or random MAC
address instead, which might be why it appeared to work during testing.

Could we adjust the device tree to point to a 6-byte cell instead?

> +
>  	amlogic,tx-delay-ns = <2>;
>  
>  	mdio {

-- 
Sashiko AI review · https://sashiko.dev/#/patchset/20261011-odroidc2-dts-v1-0-f9f0e779af88@gmail.com?part=1

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