linux-kernel - Re: [PATCH 2/2] ARM: dts: aspeed: ventura2: Add Meta ventura2 BMC

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Message-ID: <CAF7HswP7Oejs42K=jG8bkNiBoDhXR2LbeHoppk0nnNon6_afwA@mail.gmail.com>
Date: Wed, 24 Dec 2025 14:40:39 +0800
From: Kyle Hsieh <kylehsieh1995@...il.com>
To: Andrew Lunn <andrew@...n.ch>
Cc: Rob Herring <robh@...nel.org>, Krzysztof Kozlowski <krzk+dt@...nel.org>, 
	Conor Dooley <conor+dt@...nel.org>, Joel Stanley <joel@....id.au>, 
	Andrew Jeffery <andrew@...econstruct.com.au>, devicetree@...r.kernel.org, 
	linux-arm-kernel@...ts.infradead.org, linux-aspeed@...ts.ozlabs.org, 
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH 2/2] ARM: dts: aspeed: ventura2: Add Meta ventura2 BMC

On Tue, Dec 23, 2025 at 6:35 PM Andrew Lunn <andrew@...n.ch> wrote:
>
> > > What make/model of switch is it? Is it unmanaged, or does it use SPI
> > > or I2C for management?
>
> > The switch is connected via RMII to the MAC and is managed over MDIO.
>
> O.K. What make/model?
>
The device is a Marvell 88E6393X switch. In our design, the BMC connects
to the device via RMII with fixed link parameters to retrieve ethernet.
> > On our board, MDIO is not wired directly to the processor; instead, we
> > use a USB-to-MPSSE bridge (FT2232) to toggle the MDIO signals for
> > switch management.
>
> I have to push back on you using a closed source user space driver,
> given that i help maintain the Ethernet switch drivers...
>
> I know there have been attempts to get GPIO support added for FT2232,
> but i don't think any got as far as mainline. That is probably the
> only part you are missing. You can describe USB devices in DT. So you
> should be able to describe such a GPIO controller. You can then
> instantiate an virtual,mdio-gpio driver to give you an MDIO bus. And
> then add nodes for the switch using DSA.
>
Apologies for the confusion in my previous reply.
The BMC connects to the peer via an RMII fixed-link.
The link parameters are fixed at design time and there is no runtime
MDIO-managed PHY or switch control from the BMC.
>      Andrew