linux-kernel - Re: [PATCH 2/2] arm64: dts: allwinner: h6: Add OrangePi 3 LTS DTS

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Message-ID: <2486dae4-c5a5-4df2-8048-87b4b2d46d54@lunn.ch>
Date: Tue, 29 Apr 2025 17:45:24 +0200
From: Andrew Lunn <andrew@...n.ch>
To: Jernej Škrabec <jernej.skrabec@...il.com>
Cc: Andre Przywara <andre.przywara@....com>, robh@...nel.org,
	krzk+dt@...nel.org, conor+dt@...nel.org, wens@...e.org,
	samuel@...lland.org, devicetree@...r.kernel.org,
	linux-arm-kernel@...ts.infradead.org, linux-sunxi@...ts.linux.dev,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH 2/2] arm64: dts: allwinner: h6: Add OrangePi 3 LTS DTS

> I just to be clear, I tested various combinations, including rgmii-id, and it
> didn't work, except rgmii-rxid, which matches strapping. Of course Motorcomm
> PHY driver took that into account and set registers accordingly.

So we have:

&emac {
	pinctrl-names = "default";
	pinctrl-0 = <&ext_rgmii_pins>;
	phy-mode = "rgmii-rxid";
	phy-handle = <&ext_rgmii_phy>;
	phy-supply = <&reg_gmac_3v3>;
	allwinner,rx-delay-ps = <0>;
	allwinner,tx-delay-ps = <700>;
	status = "okay";
};

and

&mdio {
	ext_rgmii_phy: ethernet-phy@1 {
		compatible = "ethernet-phy-ieee802.3-c22";
		reg = <1>;

		motorcomm,clk-out-frequency-hz = <125000000>;

		reset-gpios = <&pio 3 14 GPIO_ACTIVE_LOW>; /* PD14 */
		reset-assert-us = <15000>;
		reset-deassert-us = <100000>;
	};
};

The RX path looks O.K. RGMII-RXID means the PHY should be adding the
2ns delay. The allwinner,rx-delay-ps = <0> should be redundant, that
should be the driver default. And there are no properties in the PHY
node about RX. All good.

TX is the problem. The allwinner,tx-delay-ps = <700> causes the MAC to
add 700ps delay, and 'rgmii-rxid' means the PHY should not add any
delay. But 700ps is too low. It should be around 2000ps. So something
else is adding a delay, or the 700ps is not really 700ps.

You say the PHY is a YT8531C. These PHYs also accept
rx-internal-delay-ps and tx-internal-delay-ps properties in their DT
node.

Try setting 'rgmii-id', allwinner,tx-delay-ps = <0>, and both
rx-internal-delay-ps and tx-internal-delay-ps in the PHY node to 1950.
If that does not work, try other values in the PHY node.

	Andrew