netdev - Re: [PATCH v5 3/4] riscv: dts: starfive: visionfive-v1: Setup ethernet phy

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Date: Wed, 20 Dec 2023 05:48:07 -0800
From: Emil Renner Berthing <emil.renner.berthing@...onical.com>
To: Cristian Ciocaltea <cristian.ciocaltea@...labora.com>, 
	Emil Renner Berthing <kernel@...il.dk>, Conor Dooley <conor@...nel.org>, Rob Herring <robh+dt@...nel.org>, 
	Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>, 
	Paul Walmsley <paul.walmsley@...ive.com>, Palmer Dabbelt <palmer@...belt.com>, 
	Albert Ou <aou@...s.berkeley.edu>, Richard Cochran <richardcochran@...il.com>, 
	Andrew Lunn <andrew@...n.ch>, Jacob Keller <jacob.e.keller@...el.com>
Cc: linux-riscv@...ts.infradead.org, devicetree@...r.kernel.org, 
	linux-kernel@...r.kernel.org, netdev@...r.kernel.org, kernel@...labora.com, 
	Emil Renner Berthing <emil.renner.berthing@...onical.com>
Subject: Re: [PATCH v5 3/4] riscv: dts: starfive: visionfive-v1: Setup
 ethernet phy

Cristian Ciocaltea wrote:
> The StarFive VisionFive V1 SBC uses a Motorcomm YT8521 PHY supporting
> RGMII-ID, but requires manual adjustment of the RX internal delay to
> work properly.
>
> The default RX delay provided by the driver is 1.95 ns, which proves to
> be too high. Applying a 50% reduction seems to mitigate the issue.
>
> Also note this adjustment is not necessary on BeagleV Starlight SBC,
> which uses a Microchip PHY.  Hence, there is no indication of a
> misbehaviour on the GMAC side, but most likely the issue stems from
> the Motorcomm PHY.
>
> While at it, drop the redundant gpio include, which is already provided
> by jh7100-common.dtsi.
>
> Co-developed-by: Emil Renner Berthing <emil.renner.berthing@...onical.com>
> Signed-off-by: Emil Renner Berthing <emil.renner.berthing@...onical.com>
> Signed-off-by: Cristian Ciocaltea <cristian.ciocaltea@...labora.com>
> Reviewed-by: Jacob Keller <jacob.e.keller@...el.com>
> Reviewed-by: Andrew Lunn <andrew@...n.ch>
> ---
>  .../jh7100-starfive-visionfive-v1.dts         | 22 ++++++++++++++++++-
>  1 file changed, 21 insertions(+), 1 deletion(-)
>
> diff --git a/arch/riscv/boot/dts/starfive/jh7100-starfive-visionfive-v1.dts b/arch/riscv/boot/dts/starfive/jh7100-starfive-visionfive-v1.dts
> index e82af72f1aaf..4e396f820660 100644
> --- a/arch/riscv/boot/dts/starfive/jh7100-starfive-visionfive-v1.dts
> +++ b/arch/riscv/boot/dts/starfive/jh7100-starfive-visionfive-v1.dts
> @@ -6,7 +6,6 @@
>
>  /dts-v1/;
>  #include "jh7100-common.dtsi"
> -#include <dt-bindings/gpio/gpio.h>
>
>  / {
>  	model = "StarFive VisionFive V1";
> @@ -18,3 +17,24 @@ gpio-restart {
>  		priority = <224>;
>  	};
>  };
> +
> +/*
> + * The board uses a Motorcomm YT8521 PHY supporting RGMII-ID, but requires
> + * manual adjustment of the RX internal delay to work properly.  The default
> + * RX delay provided by the driver (1.95ns) is too high, but applying a 50%
> + * reduction seems to mitigate the issue.
> + *
> + * It is worth noting the adjustment is not necessary on BeagleV Starlight SBC,
> + * which uses a Microchip PHY.  Hence, most likely the Motorcomm PHY is the one
> + * responsible for the misbehaviour, not the GMAC.
> + */
> +&mdio {
> +	phy: ethernet-phy@0 {
> +		reg = <0>;
> +		rx-internal-delay-ps = <900>;
> +	};
> +};
> +
> +&gmac {
> +	phy-handle = <&phy>;
> +};

Alphabetical ordering here, please.

/Emil