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

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Message-ID: <ad17b701-f260-473f-b96f-0668ce052e75@lunn.ch>
Date: Mon, 16 Jun 2025 20:43:14 +0200
From: Andrew Lunn <andrew@...n.ch>
To: Robert Cross <quantumcross@...il.com>
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

On Mon, Jun 16, 2025 at 02:22:43PM -0400, Robert Cross wrote:
> 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.

You are not understanding what i'm saying. This family has a single
MDIO bus controller. That controller is used by both the internal PHY
devices, plus there are two pins on the chip for external PHYs.

All the PHYs will appear on that one MDIO bus controller.

The MV88E6390_G2_SMI_PHY_CMD_FUNC_EXTERNAL bit is reserved on the 6352
family.

	Andrew