netdev - Re: [RFC] phylink: support for devices with MAC sharing SFP cage & PHY (e.g. Turris Omnia)

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Date:   Sun, 30 Dec 2018 14:35:32 -0800
From:   Florian Fainelli <f.fainelli@...il.com>
To:     Andrew Lunn <andrew@...n.ch>,
        Klaus Kudielka <klaus.kudielka@...il.com>
Cc:     netdev@...r.kernel.org, Heiner Kallweit <hkallweit1@...il.com>,
        Russell King <linux@...linux.org.uk>,
        Uwe Kleine-König <uwe@...ine-koenig.org>,
        Tomas Hlavacek <tmshlvck@...il.com>
Subject: Re: [RFC] phylink: support for devices with MAC sharing SFP cage &
 PHY (e.g. Turris Omnia)

Le 12/30/18 à 1:51 AM, Andrew Lunn a écrit :
> On Sun, Dec 30, 2018 at 09:25:53AM +0100, Klaus Kudielka wrote:
>> Hello,
> 
> Hi Klaus
> 
> Thanks for reposting on the correct list.
> 
>> Apart from the 88E1514 PHY specified for eth2, the device also
>> features an SFP cage, which uses the same SGMII of the Armada
>> 385 SoC (a 2:1 multiplexer is driven by the MOD_DEF0 signal).
> 
> Some of the Marvell Ethernet switches have a similar setup. Some ports
> have both an internal PHY and a SERDES port which can be connected to
> an SFP cage. Whichever gets link first is connected to the MAC.  I can
> also imagine a slightly different setup to what you have, the MUX is
> controlled via a GPIO, not MOD_DEF0, so again, you want both active
> until one gets link, although SFP LOS is not very reliable for this.
> 
> So we need a generic solution to this. In your case, the PHY should be
> configured down when the SFP is present, but then made active when the
> SFP is unplugged. For the Marvell switch, we need both SFP and PHY
> active until one gets a link, and then the other configured down. So
> it sounds like we need some board specific code involved to implement
> the board specific parts.

There are at least two user space configuration knobs that we could
extend to support dynamically switching between copper and fiber interface:

ethtool -s <iface> port tp|mii|fiber..

or

devlink port type eth media copper|sfp

Would that work here?
-- 
Florian