netdev - Re: [PATCH net-next 2/3] net: dsa: realtek: Add support for use of an optional mdio node

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Message-ID: <9702f3da-f755-4392-bf2b-28814ee0a8c7@lunn.ch>
Date: Mon, 28 Jul 2025 00:09:46 +0200
From: Andrew Lunn <andrew@...n.ch>
To: Jonas Karlman <jonas@...boo.se>
Cc: Linus Walleij <linus.walleij@...aro.org>,
	Alvin Šipraga <alsi@...g-olufsen.dk>,
	Vladimir Oltean <olteanv@...il.com>,
	"David S. Miller" <davem@...emloft.net>,
	Eric Dumazet <edumazet@...gle.com>,
	Jakub Kicinski <kuba@...nel.org>, Paolo Abeni <pabeni@...hat.com>,
	Yao Zi <ziyao@...root.org>, Chukun Pan <amadeus@....edu.cn>,
	Heiko Stuebner <heiko@...ech.de>, netdev@...r.kernel.org,
	linux-rockchip@...ts.infradead.org,
	linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH net-next 2/3] net: dsa: realtek: Add support for use of
 an optional mdio node

> Something like above does not seem to work, I get following:
> 
>   mdio_bus stmmac-0: MDIO device at address 0 is missing.
>   mdio_bus stmmac-0: MDIO device at address 1 is missing.
>   mdio_bus stmmac-0: MDIO device at address 2 is missing.
>   mdio_bus stmmac-0: MDIO device at address 3 is missing.

O.K, So i was wrong.

> And without an explicit 'mdio' child node the driver currently fails to
> load and the switch is never registered:
> 
>   rtl8365mb-mdio stmmac-0:1d: found an RTL8367RB-VB switch
>   rtl8365mb-mdio stmmac-0:1d: no MDIO bus node
>   rtl8365mb-mdio stmmac-0:1d: could not set up MDIO bus
>   rtl8365mb-mdio stmmac-0:1d: error -ENODEV: unable to register switch

So, not having an MDIO node was a long time ago seen as a short cut
for when there was a clear 1:1 mapping between port number and PHY bus
address. It still works, but it is somewhat deprecated. It also seems
like it is become more normal to need additional properties, like what
interrupt the PHY is using, the LEDs it has, etc.

> 
> With a 'mdio' child node 'make CHECK_DTBS=y' report something like:
> 
>   rockchip/rk3528-radxa-e24c.dtb: ethernet-switch@1d (realtek,rtl8365mb): mdio: False schema does not allow { [snip] }
>         from schema $id: http://devicetree.org/schemas/net/dsa/realtek.yaml#
> 
> So something should probably be changed, the driver, dt-bindings or
> possible both.

I think you should allow an MDIO node in DT. This is the only DSA
driver that i know of which does not allow it.

	Andrew