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

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Message-ID: <20251021201023.GA741540-robh@kernel.org>
Date: Tue, 21 Oct 2025 15:10:23 -0500
From: Rob Herring <robh@...nel.org>
To: Buday Csaba <buday.csaba@...lan.hu>
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 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