linux-kernel - Re: [PATCH net-next] net: dsa: remove OF-based MDIO bus registration from DSA core

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Date: Wed, 24 Jan 2024 08:30:11 +0300
From: Arınç ÜNAL <arinc.unal@...nc9.com>
To: Vladimir Oltean <olteanv@...il.com>
Cc: Andrew Lunn <andrew@...n.ch>, Florian Fainelli <f.fainelli@...il.com>,
 "David S. Miller" <davem@...emloft.net>, Eric Dumazet <edumazet@...gle.com>,
 Jakub Kicinski <kuba@...nel.org>, Paolo Abeni <pabeni@...hat.com>,
 Luiz Angelo Daros de Luca <luizluca@...il.com>, mithat.guner@...ont.com,
 erkin.bozoglu@...ont.com, Alvin Šipraga
 <ALSI@...g-olufsen.dk>, netdev@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH net-next] net: dsa: remove OF-based MDIO bus registration
 from DSA core

On 23.01.2024 18:44, Vladimir Oltean wrote:
> On Mon, Jan 22, 2024 at 08:33:48AM +0300, Arınç ÜNAL wrote:
>> These subdrivers which control switches [with MDIO bus] probed on OF, will
>> lose the ability to register the MDIO bus OF-based:
>>
>> drivers/net/dsa/b53/b53_common.c
>> drivers/net/dsa/lan9303-core.c
>> drivers/net/dsa/realtek/realtek-mdio.c
>> drivers/net/dsa/vitesse-vsc73xx-core.c
>>
>> These subdrivers let the DSA core driver register the bus:
>> - ds->ops->phy_read() and ds->ops->phy_write() are present.
>> - ds->user_mii_bus is not populated.
>>
>> The commit fe7324b93222 ("net: dsa: OF-ware slave_mii_bus") which brought
>> OF-based MDIO bus registration on the DSA core driver is reasonably recent
>> and, in this time frame, there have been no device trees in the Linux
>> repository that started describing the MDIO bus, or dt-bindings defining
>> the MDIO bus for the switches these subdrivers control. So I don't expect
>> any devices to be affected.
> 
> IIUC, Luiz made the original patch for the realtek switches. Shouldn't
> we wait until realtek registers ds->user_mii_bus on its own, before
> reverting? Otherwise, you're basically saying that Luiz made the DSA
> core patch without needing it.

My findings point to that. Luiz made the patch to optionally register the
MDIO bus of the MDIO controlled Realtek switches OF-based. So it's not
necessary to wait.

Arınç