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Message-ID: <b65393f1-1c36-40e5-96f6-1e7f978cc185@collabora.com>
Date: Mon, 18 Dec 2023 13:43:52 +0200
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Subject: Re: [PATCH v3 6/9] riscv: dts: starfive: visionfive-v1: Setup
 ethernet 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>,
 Hal Feng <hal.feng@starfivetech.com>,
 Michael Turquette <mturquette@baylibre.com>, Stephen Boyd
 <sboyd@kernel.org>, 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-clk@vger.kernel.org,
 linux-stm32@st-md-mailman.stormreply.com,
 linux-arm-kernel@lists.infradead.org, kernel@collabora.com,
 Emil Renner Berthing <emil.renner.berthing@canonical.com>
References: <20231215204050.2296404-1-cristian.ciocaltea@collabora.com>
 <20231215204050.2296404-7-cristian.ciocaltea@collabora.com>
 <f8f9d454-6155-4b1c-b4b2-daf98267be14@lunn.ch>
From: Cristian Ciocaltea <cristian.ciocaltea@collabora.com>
In-Reply-To: <f8f9d454-6155-4b1c-b4b2-daf98267be14@lunn.ch>
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On 12/17/23 19:55, Andrew Lunn wrote:
> 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.

Sure, will do, we need a v4 anyway.

Thanks,
Cristian