netdev - Re: [Linuxptp-devel] strangeness

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Date:   Thu, 7 Mar 2019 11:02:21 +0530
From:   Harini Katakam <harinik@...inx.com>
To:     Paul Thomas <pthomas8589@...il.com>
Cc:     Richard Cochran <richardcochran@...il.com>,
        "linuxptp-devel@...ts.sourceforge.net" 
        <linuxptp-devel@...ts.sourceforge.net>, netdev@...r.kernel.org
Subject: Re: [Linuxptp-devel] strangeness

Hi Paul,
On Thu, Mar 7, 2019 at 4:38 AM Paul Thomas <pthomas8589@...il.com> wrote:
>
> On Fri, Mar 1, 2019 at 1:24 AM Harini Katakam <harinik@...inx.com> wrote:
> >
> > +netdev
> >
> > Hi Paul,
> > On Fri, Mar 1, 2019 at 12:29 AM Richard Cochran
> > <richardcochran@...il.com> wrote:
> > >
> > > On Thu, Feb 28, 2019 at 12:33:26PM -0500, Paul Thomas wrote:
> > > > Yes changing it to TSTAMP_ALL_PTP_FRAMES instead of TSTAMP_ALL_FRAMES
> > > > does seem to fix the ssh issue. My worry is that there is still a bug
> > > > somewhere in the network stack that this is just masking.
> >
> > Ok thanks.
> > One place to check in the driver will be:
> > if (gem_ptp_do_txstamp(queue, skb, desc) == 0) {
> > /* skb now belongs to timestamp buffer
> > * and will be removed later
> > */
> > tx_skb->skb = NULL;
> > }
> > When all TX packets are timestamped, the skb always belongs to the
> > timestamp buffer.
> >
> > >
> > > Or the HW isn't sending the frames in the first place.
> > >
> > > Check that first!
> >
> > To check this, the statistics registers in MAC will be one way.
> > But if there is no TX completion interrupt, then I wouldn't expect
> > these statistics to increase either. The used bit status in BD dump
> > might be of more use.
> >
> > I will also try to reproduce (with TX timestamp ALL) and see if any of
> > the above gives some clue.
> >
> > Regards,
> > Harini
>
> Hi Harini, any luck looking at this?

I'm sorry, I was not able to debug this further.

>
> I didn't get very far, even in the "broken" state I see plenty of tx_frames:
> root@xu5:/opt/linuxptp# ethtool -S eth0
> NIC statistics:
>      ...
>      tx_frames: 39763
>      ...
>
> When you said "registers in the MAC" is ethtool -S displaying that?

Yes, ethtool does display these statistics.
I was referring to the registers starting offset 0xFF0B0108 (for GEM0) here:
https://www.xilinx.com/html_docs/registers/ug1087/ug1087-zynq-ultrascale-registers.html
If you see this value increasing, then the MAC is transmitting successfully.
Although, I realize it could be other traffic. To see if specific
packets (for the
failed SSH connection) are not being queued, a BD dump might help.

Regards,
Harini