linux-kernel - Re: [PATCH net-next v2 1/1] net: mdio: reset PHY before attempting to access ID register

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Message-ID: <37ecfff6-19da-4b0d-9623-129431d5a218@redhat.com>
Date: Tue, 2 Dec 2025 13:38:21 +0100
From: Paolo Abeni <pabeni@...hat.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>,
 netdev@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH net-next v2 1/1] net: mdio: reset PHY before attempting to
 access ID register

On 11/28/25 2:53 PM, 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.
> 
> Add a fallback mechanism for such devices: when reading the ID
> fails, the reset will be asserted, and the ID read is retried.
> 
> This allows such devices to be used with an autodetected ID.
> 
> The fallback mechanism is activated in the error handling path, and
> the return code of fwnode_mdiobus_register_phy() is unaltered, except
> when the reset fails with -EPROBE_DEFER, which is propagated to the
> caller.
> 
> Signed-off-by: Buday Csaba <buday.csaba@...lan.hu>

IMHO this deserves an explicit ack from phy maintainers. Unless such ack
is going to land on the ML very soon, I suggest to defer this patch to
the next cycle, as Jakub is wrapping the net-next PR.

Thanks,

Paolo