linux-kernel - Re: [PATCH 2/2] net: mdio: reset PHY before attempting to access registers in fwnode_mdiobus_register

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Message-ID: <e4dbb9e0-4447-485a-8b64-911c6a3d0a29@bootlin.com>
Date: Mon, 13 Oct 2025 16:31:10 +0200
From: Maxime Chevallier <maxime.chevallier@...tlin.com>
To: Buday Csaba <buday.csaba@...lan.hu>, 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>, netdev@...r.kernel.org,
 linux-kernel@...r.kernel.org
Subject: Re: [PATCH 2/2] net: mdio: reset PHY before attempting to access
 registers in fwnode_mdiobus_register_phy

Hi,

On 13/10/2025 15:55, Buday Csaba wrote:
> When the ID of an ethernet PHY is not provided by the 'compatible'
> string in the device tree, its actual ID is read via the MDIO bus.
> For some PHYs this could be unsafe, since a hard reset may be
> necessary to safely access the MDIO registers.
> This patch makes it possible to hard-reset an ethernet PHY before
> attempting to read the ID, via a new device tree property, called:
> `reset-phy-before-probe`.
> 
> There were previous attempts to implement such functionality, I
> tried to collect a few of these (see links).
> 
> Link: https://lore.kernel.org/lkml/1499346330-12166-2-git-send-email-richard.leitner@skidata.com/
> Link: https://lore.kernel.org/all/20230405-net-next-topic-net-phy-reset-v1-0-7e5329f08002@pengutronix.de/
> Link: https://lore.kernel.org/netdev/20250709133222.48802-4-buday.csaba@prolan.hu/
> Signed-off-by: Buday Csaba <buday.csaba@...lan.hu>

This should probably be accompanied by a DT binding update,
with some justification that this is indeed HW description
and not OS confguration.

At least the use of the term "probe" in the property makes this
sound like OS configuration, maybe something like :
  "phy-id-needs-reset" ?

Maxime