netdev - Re: [PATCH net-next v3 8/8] Revert "net: dsa: OF-ware slave_mii

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Message-ID: <CAJq09z46T+uySp7DOLSpmh-Zouk2_CwvdMSmyuqB14bKSYf+jg@mail.gmail.com>
Date: Mon, 8 Jan 2024 01:44:08 -0300
From: Luiz Angelo Daros de Luca <luizluca@...il.com>
To: Arınç ÜNAL <arinc.unal@...nc9.com>
Cc: netdev@...r.kernel.org, linus.walleij@...aro.org, alsi@...g-olufsen.dk, 
	andrew@...n.ch, f.fainelli@...il.com, olteanv@...il.com, davem@...emloft.net, 
	edumazet@...gle.com, kuba@...nel.org, pabeni@...hat.com
Subject: Re: [PATCH net-next v3 8/8] Revert "net: dsa: OF-ware slave_mii_bus"

Hi Arinç,

> It looks like this patch will cause the MDIO bus of the switches probed on
> OF which are controlled by these subdrivers to only be registered
> non-OF-based.
>
> drivers/net/dsa/b53/b53_common.c
> drivers/net/dsa/lan9303-core.c
> drivers/net/dsa/vitesse-vsc73xx-core.c
>
> These subdrivers let the DSA driver register the bus OF-based or
> non-OF-based:
> - ds->ops->phy_read() and ds->ops->phy_write() are present.
> - ds->user_mii_bus is not populated.

I checked the changes on those drivers since
fe7324b932222574a0721b80e72c6c5fe57960d1 and nothing indicates that
they were changing anything related to the user mii bus. I also
checked bindings for the mdio node requirement. None of them mentioned
the mdio node.

> Not being able to register the bus OF-based may cause issues. There is an
> example for the switch on the MT7988 SoC which is controlled by the MT7530
> DSA subdriver. Being able to reference the PHYs on the switch MDIO bus is
> mandatory on MT7988 as calibration data from NVMEM for each PHY is
> required.
>
> I suggest that we hold off on this patch until these subdrivers are made to
> be capable of registering the MDIO bus as OF-based on their own.

We might be over cautious keeping this for more time after the realtek
refactoring gets merged. The using OF with the generic user mii bus
driver is just a broken design and probably not in use. Anyway, it is
not a requirement for the series. If there is no objection, I can drop
it.

I would like to send v4 with the OF node handling simplified by the
change in the MDIO API. However, I'm reluctant to send mostly the same
code without any reviews.

Regards,

Luiz