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Message-ID: <f05839c0-7a78-4616-bedc-6a876b7f4bb3@collabora.com>
Date:   Mon, 30 Oct 2023 00:41:23 +0200
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Subject: Re: [PATCH v2 11/12] riscv: dts: starfive: visionfive-v1: Enable gmac
 and setup phy
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To:     Andrew Lunn <andrew@lunn.ch>
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
References: <20231029042712.520010-1-cristian.ciocaltea@collabora.com>
 <20231029042712.520010-12-cristian.ciocaltea@collabora.com>
 <f379a507-c3c1-4872-9e4f-f521b86f44d4@lunn.ch>
From:   Cristian Ciocaltea <cristian.ciocaltea@collabora.com>
In-Reply-To: <f379a507-c3c1-4872-9e4f-f521b86f44d4@lunn.ch>
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On 10/29/23 20:45, Andrew Lunn wrote:
> 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.

It seems the visionfive-v2 board also required setting some delays, but
unfortunately no details were provided:

0104340a67b1 ("riscv: dts: starfive: visionfive 2: Add configuration of
mac and phy")

Thanks,
Cristian