netdev - Re: [PATCH 2/4] dt-bindings: net: dsa: document internal MDIO bus

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Date: Tue, 12 Sep 2023 21:09:07 +0300
From: Arınç ÜNAL <arinc.unal@...nc9.com>
To: Andrew Lunn <andrew@...n.ch>
Cc: Vladimir Oltean <olteanv@...il.com>,
 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>,
 Rob Herring <robh+dt@...nel.org>,
 Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>,
 Conor Dooley <conor+dt@...nel.org>, Woojung Huh <woojung.huh@...rochip.com>,
 UNGLinuxDriver@...rochip.com, Linus Walleij <linus.walleij@...aro.org>,
 Alvin Šipraga <alsi@...g-olufsen.dk>,
 Daniel Golle <daniel@...rotopia.org>, Landen Chao
 <Landen.Chao@...iatek.com>, DENG Qingfang <dqfext@...il.com>,
 Sean Wang <sean.wang@...iatek.com>, Matthias Brugger
 <matthias.bgg@...il.com>,
 AngeloGioacchino Del Regno <angelogioacchino.delregno@...labora.com>,
 mithat.guner@...ont.com, erkin.bozoglu@...ont.com, netdev@...r.kernel.org,
 devicetree@...r.kernel.org, linux-kernel@...r.kernel.org,
 linux-arm-kernel@...ts.infradead.org, linux-mediatek@...ts.infradead.org
Subject: Re: [PATCH 2/4] dt-bindings: net: dsa: document internal MDIO bus

On 10.09.2023 00:16, Andrew Lunn wrote:
> Please trim the text when replying.
> 
> 
>> I'm writing below as a mix of patch log and discussion.
>>
>> Phylink bindings are required for ports that are controlled by OF-based
>> buses. DSA, like any other driver utilising the Linux MDIO infrastructure,
>> can register a bus. If I understand correctly, non-OF-based registration of
>> OpenFirmware MDIO buses is a feature specific to DSA which certain DSA
>> subdrivers make use of.
> 
> This is not really DSA specific. Any MAC driver, or MDIO driver, can
> call mdiobus_regsiter(), or of_mdiobus_register() and pass a NULL
> pointer if there is no OF node available. It then requires that the
> MAC driver uses an function like phy_find_first(), or knows via other
> means what address the PHY uses on the bus. For DSA, that other means
> is assuming a 1:1 mapping between port number and bus address.

Understood. At least a phy-handle on the DSA user port for each PHY 
controlled by non-DSA drivers is always needed correct? Otherwise DSA 
wouldn't know which PHY to map the DSA switch port?

And that means DSA requires OF-based buses to map the ports controlled 
by non-DSA driver buses to PHYs?

I'm trying to understand if phylink bindings for DSA user ports that are 
controlled by non-DSA driver buses are always necessary.

Would this also apply to MAC drivers that control switches?

Arınç