netdev - Re: thunderx sgmii interface hang

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Date:   Tue, 19 Dec 2017 21:52:56 +0100
From:   Andrew Lunn <andrew@...n.ch>
To:     Tim Harvey <tharvey@...eworks.com>
Cc:     Sunil Goutham <sgoutham@...ium.com>,
        netdev <netdev@...r.kernel.org>
Subject: Re: thunderx sgmii interface hang

On Mon, Dec 18, 2017 at 01:53:47PM -0800, Tim Harvey wrote:
> On Wed, Dec 13, 2017 at 11:43 AM, Andrew Lunn <andrew@...n.ch> wrote:
> >> The nic appears to work fine (pings, TCP etc) up until a performance
> >> test is attempted.
> >> When an iperf bandwidth test is attempted the nic ends up in a state
> >> where truncated-ip packets are being sent out (per a tcpdump from
> >> another board):
> >
> > Hi Tim
> >
> > Are pause frames supported? Have you tried turning them off?
> >
> > Can you reproduce the issue with UDP? Or is it TCP only?
> >
> 
> Andrew,
> 
> Pause frames don't appear to be supported yet and the issue occurs
> when using UDP as well as TCP. I'm not clear what the best way to
> troubleshoot this is.

Hi Tim

Is pause being negotiated? In theory, it should not be. The PHY should
not offer it, if the MAC has not enabled it. But some PHY drivers are
probably broken and offer pause when they should not.

Also, can you trigger the issue using UDP at say 75% the maximum
bandwidth. That should be low enough that the peer never even tries to
use pause.

All this pause stuff is just a stab in the dark. Something else to try
is to turn off various forms off acceleration, ethtook -K, and see if
that makes a difference.

     Andrew