linux-kernel - Re: [PATCH v2 3/4] dt-bindings: net: mdio: add phy-id-read-needs-reset property

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Message-ID: <aPigoh4E3_g2LzoE@debianbuilder>
Date: Wed, 22 Oct 2025 11:15:14 +0200
From: Buday Csaba <buday.csaba@...lan.hu>
To: Rob Herring <robh@...nel.org>
CC: Andrew Lunn <andrew@...n.ch>, Heiner Kallweit <hkallweit1@...il.com>,
	Russell King <linux@...linux.org.uk>, "David S. Miller"
	<davem@...emloft.net>, Eric Dumazet <edumazet@...gle.com>, Jakub Kicinski
	<kuba@...nel.org>, Paolo Abeni <pabeni@...hat.com>, Krzysztof Kozlowski
	<krzk+dt@...nel.org>, Conor Dooley <conor+dt@...nel.org>, Florian Fainelli
	<f.fainelli@...il.com>, <netdev@...r.kernel.org>,
	<devicetree@...r.kernel.org>, <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v2 3/4] dt-bindings: net: mdio: add
 phy-id-read-needs-reset property

On Tue, Oct 21, 2025 at 03:10:23PM -0500, Rob Herring wrote:
> On Wed, Oct 15, 2025 at 03:45:02PM +0200, Buday Csaba wrote:
> > Some Ethernet PHYs require a hard reset before accessing their MDIO
> > registers. When the ID is not provided by a compatible string,
> > reading the PHY ID may fail on such devices.
> > 
> > This patch introduces a new device tree property called
> > `phy-id-read-needs-reset`, which can be used to hard reset the
> > PHY before attempting to read its ID via MDIO.
> > 
> > Signed-off-by: Buday Csaba <buday.csaba@...lan.hu>
> > ---
> >  Documentation/devicetree/bindings/net/ethernet-phy.yaml | 8 ++++++++
> >  1 file changed, 8 insertions(+)
> > 
> > diff --git a/Documentation/devicetree/bindings/net/ethernet-phy.yaml b/Documentation/devicetree/bindings/net/ethernet-phy.yaml
> > index 2ec2d9fda..b570f8038 100644
> > --- a/Documentation/devicetree/bindings/net/ethernet-phy.yaml
> > +++ b/Documentation/devicetree/bindings/net/ethernet-phy.yaml
> > @@ -215,6 +215,14 @@ properties:
> >        Delay after the reset was deasserted in microseconds. If
> >        this property is missing the delay will be skipped.
> >  
> > +  phy-id-read-needs-reset:
> > +    $ref: /schemas/types.yaml#/definitions/flag
> > +    description:
> > +      Some PHYs require a hard reset before accessing MDIO registers.
> > +      This workaround allows auto-detection of the PHY ID in such cases.
> > +      When the PHY ID is provided with the 'compatible' string, setting
> > +      this property has no effect.
> 
> If the phy is listed in DT, then it should have a compatible. Therefore, 
> you don't need this property.
> 
> Rob
> 

Actually, please partly ignore my previous letter. I managed to do it
without a new DT property, and this seems to be a more elegant solution
after all.

If you wish to take a look at the next patch, you can find it here:
https://lore.kernel.org/netdev/cover.1761124022.git.buday.csaba@prolan.hu/

Thanks for the feedback!

Csaba