linux-kernel - Re: [PATCH net] net: mvpp2: Enable autoneg bypass for 1000BaseX/2500BaseX ports

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Message-ID: <20200529162504.GH869823@lunn.ch>
Date:   Fri, 29 May 2020 18:25:04 +0200
From:   Andrew Lunn <andrew@...n.ch>
To:     Russell King - ARM Linux admin <linux@...linux.org.uk>
Cc:     Thomas Bogendoerfer <tbogendoerfer@...e.de>,
        "David S. Miller" <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>, netdev@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH net] net: mvpp2: Enable autoneg bypass for
 1000BaseX/2500BaseX ports

> I wonder how much risk there is to changing that, so we force the link
> down if phylink says the link should be down, otherwise we force the
> speed/duplex, disable AN, and allow the link to come up depending on
> the serdes status.  It /sounds/ like something sane to do.

Hi Russell

I actually did this for mv88e6xxx in a patchset for ZII devel B. It
was determining link based on SFP LOS, which we know is unreliable. It
said there was link even when the SERDES had lost link.

I did it by making use of the fixed-link state call back, since it was
a quick and dirty patch. But it might make more sense for the MAC to
call phylink_mac_change() for change in PCS state? Or add a PCS
specific.

	Andrew