On Fri, Dec 15, 2023 at 10:40:45PM +0200, Cristian Ciocaltea wrote:

The StarFive VisionFive V1 SBC 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 is 1.95 ns, which proves to
be too high. Applying a 50% reduction seems to mitigate the issue.

Also note this adjustment is not necessary on BeagleV Starlight SBC,
which uses a Microchip PHY.  Hence, there is no indication of a
miss-behaviour on the GMAC side, but most likely the issue stems from
the Motorcomm PHY.

I suggest you make a similar comment in the .dts file, just to explain
the odd setting.

	Andrew