[PATCH] arm64: dts: imx8mp-debix-model-a: Disable EEE for 1000T

[Fabio Estevam]

Adding Andrew in case he can help with the review.

On Sun, Oct 26, 2025 at 9:29 AM Laurent Pinchart
<laurent.pinchart at ideasonboard.com> wrote:
>
> Energy Efficient Ethernet (EEE) is broken at least for 1000T on the EQOS
> (DWMAC) interface. When connected to an EEE-enabled peer, the ethernet
> devices produces an interrupts storm. Disable EEE support to fix it.
>
> Signed-off-by: Laurent Pinchart <laurent.pinchart at ideasonboard.com>
> ---
> The exact reason for the interrupt storm is unknown, and my attempts to
> diagnose it was hindered by my lack of expertise with DWMAC. As far as I
> understand, the DWMAC implements EEE support, and so does the RTL8211E
> PHY according to its datasheet. What each side does exactly is unknown
> to me. One theory I've heard to explain the issue is that the two
> implementations conflict. There is no register in the RTL8211E PHY to
> disable EEE on the PHY side while still advertising its support to the
> peer and relying on the implementation in the DWMAC (if this even makes
> sense), so disabling EEE is the only viable option.
>
> This patch is likely a workaround, but it fixes ethernet usage on the
> board, so it's in my opinion worth being merged. If someone with better
> knowledge of EEE and DWMAC, as well as an interest in getting it working
> properly on the Debix board, wants to submit additional patches to drop
> eee-broken-1000t, I will be happy to test them.
> ---
>  arch/arm64/boot/dts/freescale/imx8mp-debix-model-a.dts | 1 +
>  1 file changed, 1 insertion(+)
>
> diff --git a/arch/arm64/boot/dts/freescale/imx8mp-debix-model-a.dts b/arch/arm64/boot/dts/freescale/imx8mp-debix-model-a.dts
> index 9422beee30b2..4aa47f71425b 100644
> --- a/arch/arm64/boot/dts/freescale/imx8mp-debix-model-a.dts
> +++ b/arch/arm64/boot/dts/freescale/imx8mp-debix-model-a.dts
> @@ -102,6 +102,7 @@ ethphy0: ethernet-phy at 1 { /* RTL8211E */
>                         reset-gpios = <&gpio4 18 GPIO_ACTIVE_LOW>;
>                         reset-assert-us = <20>;
>                         reset-deassert-us = <200000>;
> +                       eee-broken-1000t;
>                 };
>         };
>  };
> --
> Regards,
>
> Laurent Pinchart
>