linux-kernel - Re: [PATCH v2] net: dsa: mv88e6xxx: fix external smi for mv88e6176

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Message-ID: <CAATNC474tcoDeDaGg1GKbSAkb8QBT9rcHrHrszycWpQwzU+6XA@mail.gmail.com>
Date: Mon, 16 Jun 2025 14:22:43 -0400
From: Robert Cross <quantumcross@...il.com>
To: Andrew Lunn <andrew@...n.ch>
Cc: netdev@...r.kernel.org, bpf@...r.kernel.org, olteanv@...il.com, 
	davem@...emloft.net, edumazet@...gle.com, kuba@...nel.org, pabeni@...hat.com, 
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2] net: dsa: mv88e6xxx: fix external smi for mv88e6176

According to the documents I'm looking at, the 88E6172 and
88E6176 both have external MDIO buses. I have brought up
a board with two connected 88E6176 chips, each with a PHY
that can only be managed with the MDC/MDIO_PHY pins of
the 88E6176s.

After applying this patch I was able to successfully manage
and control these external PHYs without issue. I'm not sure
if you have access to the 88E6176 datasheet specifically,
but this chip absolutely does have an external MDIO.

(also, I fixed the problems with the checkpatch.pl, I will submit
the fixed version again tomorrow)

- Robert Cross

On Mon, Jun 16, 2025 at 1:55 PM Andrew Lunn <andrew@...n.ch> wrote:
>
> On Mon, Jun 16, 2025 at 12:20:25PM -0400, Robert Cross wrote:
> > (Sorry this is my second attempt, I fixed my email client)
> >
> > I was trying to enable external SMI on a mv88e6176.
>
>         MV88E6XXX_FAMILY_6352,  /* 6172 6176 6240 6352 */
>
> So it is part of the 6352 family. That family does not have an
> internal and external MDIO bus. It has a single bus which is both
> internal and external.
>
> It is only the 6390 family and above which has two MDIO busses.
>
>     Andrew
>
> ---
> pw-bot: cr