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Date:   Sun, 29 Oct 2023 19:45:12 +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>,
        Paul Walmsley <paul.walmsley@sifive.com>,
        Palmer Dabbelt <palmer@dabbelt.com>,
        Albert Ou <aou@eecs.berkeley.edu>,
        Alexandre Torgue <alexandre.torgue@foss.st.com>,
        Jose Abreu <joabreu@synopsys.com>,
        Maxime Coquelin <mcoquelin.stm32@gmail.com>,
        Richard Cochran <richardcochran@gmail.com>,
        Giuseppe Cavallaro <peppe.cavallaro@st.com>,
        netdev@vger.kernel.org, devicetree@vger.kernel.org,
        linux-kernel@vger.kernel.org, linux-riscv@lists.infradead.org,
        linux-stm32@st-md-mailman.stormreply.com,
        linux-arm-kernel@lists.infradead.org, kernel@collabora.com
Subject: Re: [PATCH v2 11/12] riscv: dts: starfive: visionfive-v1: Enable
 gmac and setup phy
Message-ID: <f379a507-c3c1-4872-9e4f-f521b86f44d4@lunn.ch>
References: <20231029042712.520010-1-cristian.ciocaltea@collabora.com>
 <20231029042712.520010-12-cristian.ciocaltea@collabora.com>
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On Sun, Oct 29, 2023 at 06:27:11AM +0200, Cristian Ciocaltea wrote:
> The StarFive VisionFive V1 SBC has 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.

I'm not so happy this cannot be explained. You are potentially heading
into horrible backwards compatibility problems with old DT blobs and
new kernels once this is explained and fixed.

    Andrew