netdev - RE: [PATCH net-next 0/3] net: enetc: add port MDIO support for both i.MX94 and i.MX95

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Message-ID:
 <PAXPR04MB851011D5F7D3BD0D77EFFDFE88C4A@PAXPR04MB8510.eurprd04.prod.outlook.com>
Date: Tue, 4 Nov 2025 02:29:53 +0000
From: Wei Fang <wei.fang@....com>
To: Andrew Lunn <andrew@...n.ch>
CC: Claudiu Manoil <claudiu.manoil@....com>, Vladimir Oltean
	<vladimir.oltean@....com>, Clark Wang <xiaoning.wang@....com>,
	"andrew+netdev@...n.ch" <andrew+netdev@...n.ch>, "davem@...emloft.net"
	<davem@...emloft.net>, "edumazet@...gle.com" <edumazet@...gle.com>,
	"kuba@...nel.org" <kuba@...nel.org>, "pabeni@...hat.com" <pabeni@...hat.com>,
	Aziz Sellami <aziz.sellami@....com>, "imx@...ts.linux.dev"
	<imx@...ts.linux.dev>, "netdev@...r.kernel.org" <netdev@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: RE: [PATCH net-next 0/3] net: enetc: add port MDIO support for both
 i.MX94 and i.MX95

> > > So you have up to 32 virtual MDIO busses stacked on top of one
> >
> > Theoretically, there are up to 33 virtual MDIO buses, 32 port MDIO +
> > 1 'EMDIO function'. The EMDIO function can access all the PHYs on
> > the physical MDIO bus.
> 
> The EMDIO function sound dangerous. All the locking and PHY drivers
> assume they have exclusive access to a devices on the bus. Bad things
> will happen if they don't. And given how infrequently MDIO is
> typically used, such bugs are going to be hard to find.
> 
> You might want to make the 32 port MDIOs and the EMDIO mutually
> exclusive, so you can eliminate those potential bugs.
> 

When the PHY node is a child node of the ENETC node, ENETC will use
its port MDIO. When the PHY node is a child node of EMDIO, ENETC
will use EMDIO to access its PHY. Therefore, the DTS configuration
ensures mutual exclusion.