Re: [PATCH 3/3] arm64: dts: rockchip: add dts for Ariaboard Photonicat RK3568

Andrew Lunn
2024-09-05T18:20:27Z

> arch/riscv/boot/dts/starfive/jh7100-starfive-visionfive-v1.dts also
> uses YT8521. I added rx-internal-delay-ps and tx-internal-delay-ps
> to rgmii_phy1 of mdio1 according to the prompts, and it now works
> well using rgmii-id!
>
> &mdio1 {
> rgmii_phy1: ethernet-phy@0 {
> compatible = "ethernet-phy-ieee802.3-c22";
> reg = <0x0>;
> rx-internal-delay-ps = <1500>;
> tx-internal-delay-ps = <1500>;
> };
> };
>
> &gmac1 {
> [...]
> phy-mode = "rgmii-id";
> [...]
> tx_delay = <0x0>;
> rx_delay = <0x0>;
> status = "okay";
> /* Motorcomm YT8521SC WAN port */
> };

That looks O.K.

The YT8521SC seems to have issues with delays.
jh7100-starfive-visionfive-v1.dts says

/*
* The board 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 (1.95ns) is too high, but applying a 50%
* reduction seems to mitigate the issue.
*
* It is worth noting the adjustment is not necessary on BeagleV Starlight SBC,
* which uses a Microchip PHY. Hence, most likely the Motorcomm PHY is the one
* responsible for the misbehaviour, not the GMAC.
*/

Andrew