linux-kernel - Re: [PATCH] phy: ti: gmii-sel: Force RGMII TX delay

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Message-ID: <3bc6476e-7539-40aa-b499-253273357a1d@lunn.ch>
Date: Mon, 4 Aug 2025 17:19:19 +0200
From: Andrew Lunn <andrew@...n.ch>
To: Michael Walle <mwalle@...nel.org>
Cc: Vinod Koul <vkoul@...nel.org>,
	Kishon Vijay Abraham I <kishon@...nel.org>,
	Siddharth Vadapalli <s-vadapalli@...com>,
	Matthias Schiffer <matthias.schiffer@...tq-group.com>,
	linux-phy@...ts.infradead.org, linux-kernel@...r.kernel.org,
	netdev@...r.kernel.org, nm@...com, vigneshr@...com
Subject: Re: [PATCH] phy: ti: gmii-sel: Force RGMII TX delay

On Mon, Aug 04, 2025 at 04:06:52PM +0200, Michael Walle wrote:
> Some SoCs are just validated with the TX delay enabled. With commit
> ca13b249f291 ("net: ethernet: ti: am65-cpsw: fixup PHY mode for fixed
> RGMII TX delay"), the network driver will patch the delay setting on the
> fly assuming that the TX delay is fixed. In reality, the TX delay is
> configurable and just skipped in the documentation. There are
> bootloaders, which will disable the TX delay and this will lead to a
> transmit path which doesn't add any delays at all. Fix that by always
> forcing the TX delay to be enabled.

Please could you add a paragraph:

    This is safe to do, and will not break any existing boards
    supported in mainline because...

We have to be careful of regressions, and such a paragraph makes it
clear you have thought it through, and what your assumptions are. If
something does break, listing your assumptions will help finding what
went wrong.

   Andrew