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Date: Tue, 12 May 2026 09:52:27 +0200
From: Francesco Dolcini <francesco@dolcini.it>
To: Andrew Lunn <andrew@lunn.ch>
Cc: Frank Li <Frank.Li@nxp.com>, Rob Herring <robh@kernel.org>,
	Krzysztof Kozlowski <krzk+dt@kernel.org>,
	Conor Dooley <conor+dt@kernel.org>,
	Sascha Hauer <s.hauer@pengutronix.de>,
	Pengutronix Kernel Team <kernel@pengutronix.de>,
	Fabio Estevam <festevam@gmail.com>, devicetree@vger.kernel.org,
	imx@lists.linux.dev, linux-arm-kernel@lists.infradead.org,
	linux-kernel@vger.kernel.org
Subject: Re: [PATCH 1/4] ARM: dts: imx6qdl-sabrelite: add mdio phy address 0
Message-ID: <20260512075227.GC5820@francesco-nb>
References: <20260511-b4-imx25_dts_simple_warning-v1-0-01b855a5ce25@nxp.com>
 <20260511-b4-imx25_dts_simple_warning-v1-1-01b855a5ce25@nxp.com>
 <f04fadf2-8d73-435b-b713-9d07e48e80ae@lunn.ch>
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In-Reply-To: <f04fadf2-8d73-435b-b713-9d07e48e80ae@lunn.ch>

On Tue, May 12, 2026 at 12:15:08AM +0200, Andrew Lunn wrote:
> On Mon, May 11, 2026 at 05:04:56PM -0400, Frank Li wrote:
> > According to IEEE 802.3 Clause 22.2.4.5.5 PHYAD (PHY Address), A PHY that
> > is connected to the station management entity via the mechanical interface
> > defined in 22.6 shall always respond to transactions addressed to PHY
> > Address zero <00000>.
> 
> Did you read 22.6? I've not seen a mechanical interface as defined in
> 22.6 for at least 20 years, maybe 30 years.
> 
> That cause does not apply in this context.
> 
> > -		ethphy: ethernet-phy {
> > +		ethphy: ethernet-phy@0 {
> >  			compatible = "ethernet-phy-ieee802.3-c22";
> > +			reg = <0>;
> 
> This could very well break this board. Without a reg value, the core
> will find the first PHY on the bus, at whatever address it is at. If
> you hard code 0, the PHY must be at 0, otherwise it will not be found.

Whoops, I replied without reading your answer first.

Yes, I agree, this change will break the board functionality.