netdev - Re: [PATCH net-next v2 2/3] net: ethernet: ti: am65-cpsw: fixup PHY mode for fixed RGMII TX delay

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Message-ID: <fa3688c0-3b01-49fb-9c16-eeea66748876@lunn.ch>
Date: Mon, 14 Jul 2025 15:09:22 +0200
From: Andrew Lunn <andrew@...n.ch>
To: Michael Walle <mwalle@...nel.org>
Cc: Matthias Schiffer <matthias.schiffer@...tq-group.com>,
	Andrew Lunn <andrew+netdev@...n.ch>,
	"David S. Miller" <davem@...emloft.net>,
	Eric Dumazet <edumazet@...gle.com>,
	Jakub Kicinski <kuba@...nel.org>, Paolo Abeni <pabeni@...hat.com>,
	Rob Herring <robh@...nel.org>,
	Krzysztof Kozlowski <krzk+dt@...nel.org>,
	Conor Dooley <conor+dt@...nel.org>,
	Andy Whitcroft <apw@...onical.com>,
	Dwaipayan Ray <dwaipayanray1@...il.com>,
	Lukas Bulwahn <lukas.bulwahn@...il.com>,
	Joe Perches <joe@...ches.com>, Jonathan Corbet <corbet@....net>,
	Nishanth Menon <nm@...com>, Vignesh Raghavendra <vigneshr@...com>,
	Siddharth Vadapalli <s-vadapalli@...com>,
	Roger Quadros <rogerq@...nel.org>, Tero Kristo <kristo@...nel.org>,
	linux-doc@...r.kernel.org, linux-kernel@...r.kernel.org,
	netdev@...r.kernel.org, devicetree@...r.kernel.org,
	linux-arm-kernel@...ts.infradead.org, linux@...tq-group.com,
	Maxime Chevallier <maxime.chevallier@...tlin.com>
Subject: Re: [PATCH net-next v2 2/3] net: ethernet: ti: am65-cpsw: fixup PHY
 mode for fixed RGMII TX delay

On Mon, Jul 14, 2025 at 12:01:22PM +0200, Michael Walle wrote:
> Hi,
> 
> On Tue Jun 24, 2025 at 12:53 PM CEST, Matthias Schiffer wrote:
> > All am65-cpsw controllers have a fixed TX delay, so the PHY interface
> > mode must be fixed up to account for this.
> >
> > Modes that claim to a delay on the PCB can't actually work. Warn people
> > to update their Device Trees if one of the unsupported modes is specified.
> >
> > Signed-off-by: Matthias Schiffer <matthias.schiffer@...tq-group.com>
> > Reviewed-by: Maxime Chevallier <maxime.chevallier@...tlin.com>
> > Reviewed-by: Andrew Lunn <andrew@...n.ch>
> 
> For whatever reason, this patch is breaking network on our board
> (just transmission). We have rgmii-id in our devicetree which is now
> modified to be just rgmii-rxid. The board has a TI AM67A (J722S) with a
> Broadcom BCM54210E PHY. I'm not sure, if AM67A MAC doesn't add any
> delay or if it's too small. I'll need to ask around if there are any
> measurements but my colleague doing the measurements is on holiday
> at the moment.

I agree, we need to see if this is a AM65 vs AM67 issue. rgmii-id
would be correct if the MAC is not adding delays.

Do you have access to the datasheets for both? Can you do a side by
side comparison for the section which describes the fixed TX delay?

	Andrew