linux-kernel - Re: [PATCH net-next] net: dsa: mv88e6xxx: enable automedia on 6190x and 6390x devices

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Message-ID: <d3f45312-882d-4667-89da-c562e0828589@lunn.ch>
Date:   Mon, 24 Jul 2023 20:34:27 +0200
From:   Andrew Lunn <andrew@...n.ch>
To:     Ante Knezic <ante.knezic@...mholz.de>
Cc:     netdev@...r.kernel.org, f.fainelli@...il.com, olteanv@...il.com,
        davem@...emloft.net, edumazet@...gle.com, kuba@...nel.org,
        pabeni@...hat.com, linux-kernel@...r.kernel.org
Subject: Re: [PATCH net-next] net: dsa: mv88e6xxx: enable automedia on 6190x
 and 6390x devices

On Mon, Jul 24, 2023 at 12:18:29PM +0200, Ante Knezic wrote:
> Marvell 6190x and 6390x devices support using unusued lanes of
> ports 9 and 10 as automedia PHY/SERDES ports. In order to be
> able to use them as automedia ports, serdes lanes must be
> properly initialized so we allow setting the desired cmode to
> be later used by the phylink_pcs infrastructure.

By auto-media, you mean both a copper PHY and an SFP? And whichever
gets link first wins the MAC?

auto-media has been discussed a few times, and rejected, since Linux
has no concept of multiple 'phy like devices' connected to one MAC.

How are you representing this in DT? I assume you have both an SFP
socket, and a phy-handle pointing to a PHY? phylink will not drive
both at the same time. So you cannot have them admin up at the same
time? How do you get the SFP out of TX disable, when phylink sees a
PHY? What does ethtool return? What the PHY is advertising as its link
modes? Or nothing since an SFP does not advertise speeds?

       Andrew