linux-kernel - Re: [PATCH 1/3] arm64: dts: rockchip: Change gmac phy-mode to rgmii-id for rk3576 evb1

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Message-ID: <81D509A8F65F0243+c7b58aef-95a4-4f2a-a423-7e8b2c0bbeab@airkyi.com>
Date: Thu, 22 Jan 2026 09:38:17 +0800
From: Chaoyi Chen <kernel@...kyi.com>
To: Andrew Lunn <andrew@...n.ch>
Cc: Rob Herring <robh@...nel.org>, Krzysztof Kozlowski <krzk+dt@...nel.org>,
 Conor Dooley <conor+dt@...nel.org>, Heiko Stuebner <heiko@...ech.de>,
 Alexey Charkov <alchark@...il.com>, Shawn Lin <shawn.lin@...k-chips.com>,
 Sebastian Reichel <sebastian.reichel@...labora.com>,
 Chaoyi Chen <chaoyi.chen@...k-chips.com>, Andy Yan
 <andy.yan@...k-chips.com>,
 Nicolas Frattaroli <nicolas.frattaroli@...labora.com>,
 Detlev Casanova <detlev.casanova@...labora.com>,
 Stephen Chen <stephen@...xa.com>, devicetree@...r.kernel.org,
 linux-arm-kernel@...ts.infradead.org, linux-rockchip@...ts.infradead.org,
 linux-kernel@...r.kernel.org
Subject: Re: [PATCH 1/3] arm64: dts: rockchip: Change gmac phy-mode to
 rgmii-id for rk3576 evb1

Hi Andrew,

On 1/21/2026 8:55 PM, Andrew Lunn wrote:
>> @@ -721,6 +719,7 @@ rgmii_phy0: ethernet-phy@1 {
>>  		reset-assert-us = <20000>;
>>  		reset-deassert-us = <100000>;
>>  		reset-gpios = <&gpio2 RK_PB5 GPIO_ACTIVE_LOW>;
>> +		tx-internal-delay-ps = <1950>;
> 
> The PHY should add 2000ps, as required by the RGMII standard. The
> difference is so small there is no need for tx-internal-delay.
>

Thank you for the clarification. I chose 1950 here because I find that
the MotorComm yt8xxx Ethernet PHY binding only offer the options of 
1950 or 2100. 

> In most cases, 'rmgii-id' should be sufficient, unless the PCB is
> badly designed.
> 

I suspect the ROCK 4D board might be an exception. Sebastian once
reported that it wouldn't work properly under "rgmii-id". Well, I'm
not sure what strategy to adopt in this case.

-- 
Best, 
Chaoyi