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

From: Russell King - ARM Linux
Date: Mon Aug 28 2017 - 04:52:26 EST


On Mon, Aug 28, 2017 at 10:38:37AM +0200, Marcin Wojtas wrote:
> Hi Antoine,
>
> 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>

--
RMK's Patch system: http://www.armlinux.org.uk/developer/patches/
FTTC broadband for 0.8mile line in suburbia: sync at 8.8Mbps down 630kbps up
According to speedtest.net: 8.21Mbps down 510kbps up