Re: [PATCH 2/2] arm64: dts: rockchip: Add EmbedFire LubanCat 4 board

[Andrew Lunn <andrew@lunn.ch>]

On Tue, Jul 07, 2026 at 05:20:35AM +0800, Pufan Jin wrote:
> On Sun, Jul 05, 2026 at 05:11:58PM +0200, Andrew Lunn wrote:
> > > +	/* The board has 1.5ns delays on RX lines; TX delay is provided by the MAC. */
> >
> > That is pretty unusual. How is this RX delay done?
> 
> You're right to question this, and I apologise -- the comment was
> inaccurate. I re-checked the board schematic and both TXC and RXC
> have ~2ns of trace delay added on the PCB (annotated as
> "TXC / RXC : delays 2ns" next to the RGMII bus).

O.K. So both having delays on the PCB is what i would call "somewhat
unusual", vs "pretty unusual" for a single delay.

> Since the PCB already provides the required clock skew on both
> directions, for v2 I will switch to:
> 
>     phy-mode = "rgmii";
> 
> and drop both the tx_delay property and the misleading comment.

Please correct the comment. One issue we have is that many boards use
"rgmii" and are broken. You have a board which uses "rgmii" and it is
in fact correct. It is good to explain why it is correct, otherwise
people could think it is just another broken board.

       Andrew