[PATCH 0/4] arm64: dts: rockchip: Add HINLINK H66K/H68K

[Andrew Lunn]

> As I worked on my dts, I discovered that the 1Gb ethernet ports, using an
> RTL8211, don't support rgmii-id mode; only rgmii.
> (https://www.realtek.com/Product/Index?id=3976&cate_id=786). 

Which exact RTL8211 does the board use? You link to information for
the RTL8211FD(I)-CG, which i assume is supported in Linux as RTL8211F.

https://elixir.bootlin.com/linux/v6.16.3/source/drivers/net/phy/realtek/realtek_main.c#L519

This indicates it supports all four RGMII modes. And in general, all
PHY drivers in Linux for RGMII PHYs support all four RGMII modes.

> Changing this makes a huge difference in the ethernet throughput speed. With
> rgmii-id mode specified, throughput is about 6.5 Mbs. Changing this to rgmii
> mode increases throughput to about 960 Mbs. 

Here is some more information about that the four RGMII modes mean,
and how you should use them in Linux:

https://elixir.bootlin.com/linux/v6.16.3/source/Documentation/devicetree/bindings/net/ethernet-controller.yaml#L264

	Andrew