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

From: Buday Csaba <[email-masked]>
Date: Wed, 22 Oct 2025 11:15:14 +0200

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 <[email-masked]>
> > ---
> >  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/[email-masked]/

Thanks for the feedback!

Csaba