[PATCH RFC 3/9] net: stmmac: qcom-ethqos: fix RGMII_ID mode to use DLL bypass

[Mohd Ayaan Anwar]

On Mon, Jun 15, 2026 at 06:48:55PM +0200, Andrew Lunn wrote:
> > > I'm curious how this works at the moment? Do no boards make use of
> > > RGMII ID? Are all current boards broken?
> > 
> > Searching through the DTS, I found that we have two boards using "rgmii"
> > (qcs404-evb-4000.dts and sa8155-adp.dts) and another board using
> > "rgmii-txid" (sa8540p-ride.dts). No board which uses RGMII ID.
> 
> So this causes problems. We cannot break existing boards, yet it would
> be good to fix the current broken behaviour.

I am trying to track down the sa8155-adp and sa8540p-ride boards. The
EMAC on QCS404 is extremely similar to QCS615 Ride [0], and I got that
board to work with this series (with RGMII ID mode). So I am fairly
confident that QCS404 would not break (if its even booting up with the
upstream kernel currently). Also, I think we could change the phy-mode
for QCS404 to "rgmii-id" from "rgmii" if these fixes go in.

> It could be the best way forward is that you issue a warning when
> "rgmii" is found and pass rgmii-id to the PHY. And you also change the
> two boards to use rgmii-id. Lets think about the rgmii-txid case once
> we better understand it.
> 

As Konrad mentioned, it would be great to know if we can test out these
boards. Looking at the different versions of the ETHQOS programming
guide, stopping MAC side delay should be as simple as what we are doing
in this commit. But whether the two boards work directly with the
default PHY delays is unknown.

	Ayaan

[0] The proposed RGMII fixes would help enable ethernet on QCS615 Ride
as well. I see that the original series had a lot of issues:
https://lore.kernel.org/all/20250121-dts_qcs615-v3-0-fa4496950d8a@quicinc.com/