Re: [PATCH] Revert "ARM: dts: sun7i: A20-olinuxino-lime2: Fix ethernet phy-mode"

["Petr Štetiar" <ynezz@true.cz>]

Petr Štetiar <ynezz@true.cz> [2022-03-08 13:55:30]:

Hi Greg,

one week has passed and as I didn't received any feedback, I'm providing more
details in a hope to make it more clear, why I think, that this fix is wrong
and should be reverted in LTS kernels 5.10 and 5.15.

> This reverts commit 55dd7e059098ce4bd0a55c251cb78e74604abb57 as it breaks
> network on my A20-olinuxino-lime2 hardware revision "K" which has Micrel
> KSZ9031RNXCC-TR Gigabit PHY. Bastien has probably some previous hardware
> revisions which were based on RTL8211E-VB-CG1 PHY and thus this fix was
> working on his board.

Disclaimer, I don't own A20-olinuxino-lime2 board with earlier HW revisions
G/G1/G2 utilizing RTL8211E PHY.

My understanding is, that up to kernel version 5.9 and specifically commit
bbc4d71d6354 ("net: phy: realtek: fix rtl8211e rx/tx delay config") it was
likely possible to use same DTS for A20-olinuxino-lime2 with KSZ9031 or
RTL8211E PHYs (all HW revisions).

At least I was using my A20-olinuxino-lime2 HW revision K with KSZ9031 PHY
just fine with 4.19 kernel. After upgrade to 5.10 LTS kernel my network
stopped working, reverting stable backport commit a90398438517 ("ARM: dts:
sun7i: A20-olinuxino-lime2: Fix ethernet phy-mode") fixed it.

From my POV proper fix for earlier HW revisions G/G1/G2 is introduction of
sun7i-a20-olinuxino-lime2-revG.dts with a proper `phy-mode` for RTL8211E PHY.

Cheers,

Petr

> Cc: stable@vger.kernel.org
> Cc: Bastien Roucariès <rouca@debian.org>
> References: https://github.com/openwrt/openwrt/issues/9153
> References: https://github.com/OLIMEX/OLINUXINO/blob/master/HARDWARE/A20-OLinuXino-LIME2/hardware_revision_changes_log.txt
> Signed-off-by: Petr Štetiar <ynezz@true.cz>
> ---
>  arch/arm/boot/dts/sun7i-a20-olinuxino-lime2.dts | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/arch/arm/boot/dts/sun7i-a20-olinuxino-lime2.dts b/arch/arm/boot/dts/sun7i-a20-olinuxino-lime2.dts
> index ecb91fb899ff..8077f1716fbc 100644
> --- a/arch/arm/boot/dts/sun7i-a20-olinuxino-lime2.dts
> +++ b/arch/arm/boot/dts/sun7i-a20-olinuxino-lime2.dts
> @@ -112,7 +112,7 @@ &gmac {
>  	pinctrl-names = "default";
>  	pinctrl-0 = <&gmac_rgmii_pins>;
>  	phy-handle = <&phy1>;
> -	phy-mode = "rgmii-id";
> +	phy-mode = "rgmii";
>  	status = "okay";
>  };