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Date: Sun, 17 Dec 2023 18:55:10 +0100
From: Andrew Lunn <andrew@lunn.ch>
To: Cristian Ciocaltea <cristian.ciocaltea@collabora.com>
Cc: "David S. Miller" <davem@davemloft.net>,
	Eric Dumazet <edumazet@google.com>,
	Jakub Kicinski <kuba@kernel.org>, Paolo Abeni <pabeni@redhat.com>,
	Rob Herring <robh+dt@kernel.org>,
	Krzysztof Kozlowski <krzysztof.kozlowski+dt@linaro.org>,
	Conor Dooley <conor+dt@kernel.org>,
	Emil Renner Berthing <kernel@esmil.dk>,
	Samin Guo <samin.guo@starfivetech.com>,
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	Emil Renner Berthing <emil.renner.berthing@canonical.com>
Subject: Re: [PATCH v3 6/9] riscv: dts: starfive: visionfive-v1: Setup
 ethernet phy
Message-ID: <f8f9d454-6155-4b1c-b4b2-daf98267be14@lunn.ch>
References: <20231215204050.2296404-1-cristian.ciocaltea@collabora.com>
 <20231215204050.2296404-7-cristian.ciocaltea@collabora.com>
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In-Reply-To: <20231215204050.2296404-7-cristian.ciocaltea@collabora.com>

On Fri, Dec 15, 2023 at 10:40:45PM +0200, 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
> miss-behaviour on the GMAC side, but most likely the issue stems from
> the Motorcomm PHY.

I suggest you make a similar comment in the .dts file, just to explain
the odd setting.

	Andrew