On Tue, 21 Jan 2025 15:54:53 +0800
Yijie Yang [off-list ref] wrote:

Correct the definition of 'phy-mode' to reflect that RX and TX delays are
added by the board, not the MAC, to prevent confusion and ensure accurate
documentation.

That's not entirely correct though. The purpose of the RGMII variants
(TXID, RXID, ID) are mostly to know whether or not the PHY must add
internal delays. That would be when the MAC can't AND there's no PCB
delay traces. Some MAC can insert delays.

There's documentation here as well on that point :

https://elixir.bootlin.com/linux/v6.13-rc3/source/Documentation/networking/phy.rst#L82

So, MACs may insert delays. A modification for the doc, if needed,
would rather be :

-      # RX and TX delays are added by the MAC when required
+      # RX and TX delays are added by the MAC or PCB traces when required

Thanks,

Maxime