Re: [PATCH v3 7/8] arm64: dts: amlogic: t7: khadas-vim4: enable the ethernet port

From: Martin Blumenstingl <martin.blumenstingl@googlemail.com>
To: Lucas Tanure <tanure@linux.com>
Cc: xianwei.zhao@amlogic.com, Andrew Lunn <andrew+netdev@lunn.ch>,
	 "David S. Miller" <davem@davemloft.net>,
	Eric Dumazet <edumazet@kernel.org>,
	 Jakub Kicinski <kuba@kernel.org>,
	Paolo Abeni <pabeni@redhat.com>, Rob Herring <robh@kernel.org>,
	 Krzysztof Kozlowski <krzk+dt@kernel.org>,
	Conor Dooley <conor+dt@kernel.org>,
	 Neil Armstrong <neil.armstrong@linaro.org>,
	Kevin Hilman <khilman@baylibre.com>,
	 Jerome Brunet <jbrunet@baylibre.com>,
	Maxime Chevallier <maxime.chevallier@bootlin.com>,
	 Maxime Coquelin <mcoquelin.stm32@gmail.com>,
	Alexandre Torgue <alexandre.torgue@foss.st.com>,
	 netdev@vger.kernel.org, devicetree@vger.kernel.org,
	 linux-arm-kernel@lists.infradead.org,
	linux-amlogic@lists.infradead.org,  linux-kernel@vger.kernel.org
Subject: Re: [PATCH v3 7/8] arm64: dts: amlogic: t7: khadas-vim4: enable the ethernet port
Date: Sun, 11 Oct 2026 00:00:40 +0200	[thread overview]
Message-ID: <CAFBinCC8iKESoc2zEXJMEmqk0cwWbVap-a2KcAtB7-KFKO9Atg@mail.gmail.com> (raw)
In-Reply-To: <20261010105900.247342-8-tanure@linux.com>

On Sat, Oct 10, 2026 at 12:59 PM Lucas Tanure <tanure@linux.com> wrote:
[...]
> RGMII needs a delay on each of its two clocks, and on this board
> both come from inside the chips, not from the board traces. The PHY
> adds the one on receive. Its transmit delay does not work here, so the
> controller adds that one.
[...]
> +&ethmac {
> +       status = "okay";
> +       pinctrl-0 = <&eth_pins>, <&eth_rgmii_pins>;
> +       pinctrl-names = "default";
> +       phy-mode = "rgmii-id";
> +       phy-handle = <&external_phy>;
> +       tx-internal-delay-ps = <2000>;
You're stating that RTL8211F's TX delay doesn't work but not explaining why.
I haven't come across this behavior before and I'm worried that that's
an issue with a batch of RTL8211F.
What if the previous/next batch of RTL8211F will have working TX delay
again - wouldn't that mean 4ns delay in total unless the RTL8211F
driver is changed?

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