netdev - Re: [PATCH net-next v2 05/14] net: mvpp2: do not force the link mode

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Message-ID: <20170828094051.GE2568@kwain>
Date:   Mon, 28 Aug 2017 11:40:51 +0200
From:   Antoine Tenart <antoine.tenart@...e-electrons.com>
To:     Russell King - ARM Linux <linux@...linux.org.uk>
Cc:     Marcin Wojtas <mw@...ihalf.com>,
        Antoine Tenart <antoine.tenart@...e-electrons.com>,
        "David S. Miller" <davem@...emloft.net>, kishon@...com,
        Andrew Lunn <andrew@...n.ch>,
        Jason Cooper <jason@...edaemon.net>,
        Sebastian Hesselbarth <sebastian.hesselbarth@...il.com>,
        Gregory Clément 
        <gregory.clement@...e-electrons.com>,
        Thomas Petazzoni <thomas.petazzoni@...e-electrons.com>,
        nadavh@...vell.com, linux-kernel@...r.kernel.org,
        Stefan Chulski <stefanc@...vell.com>,
        Miquèl Raynal 
        <miquel.raynal@...e-electrons.com>, netdev <netdev@...r.kernel.org>
Subject: Re: [PATCH net-next v2 05/14] net: mvpp2: do not force the link mode

On Mon, Aug 28, 2017 at 09:51:52AM +0100, Russell King - ARM Linux wrote:
> On Mon, Aug 28, 2017 at 10:38:37AM +0200, Marcin Wojtas wrote:
> >
> > Can you be 100% sure that when using SGMII with PHY's (like Marvell
> > Alaska 88E1xxx series), is in-band link information always available?
> > I'd be very cautious with such assumption and use in-band management
> > only when set in the DT, like mvneta. I think phylib can properly can
> > do its work when MDIO connection is provided on the board.
> 
> There is another issue to be aware of: if you're wanting to use flow
> control autonegotiation, that is not carried across SGMII's in-band
> signalling.  If you want to use SGMII's in-band signalling for the
> duplex and speed information, you still need phylib's notification
> to properly set the flow control.
> 
> <plug>
> Switching mvpp2 to use phylink (which is needed for the 1G SFP slot on
> mcbin) will handle all this for you - dealing with both in-band and
> out-of-band negotiation methods, and combining them in the appropriate
> manner for the selected operation mode.
> </plug>

So probably the best move here is to remove this patch, and wait for the
phylink support in the PPv2 driver.

Thanks!
Antoine

-- 
Antoine Ténart, Free Electrons
Embedded Linux and Kernel engineering
http://free-electrons.com

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