Re: [PATCH net-next 0/5] PTP support for the SJA1105 DSA driver

[Vladimir Oltean]

On 5/29/19 7:52 AM, Richard Cochran wrote:
> On Wed, May 29, 2019 at 02:56:22AM +0300, Vladimir Oltean wrote:
> > Not all is rosy, though.
>
> You can sure say that again!
>   
> > PTP timestamping will only work when the ports are bridged. Otherwise,
> > the metadata follow-up frames holding RX timestamps won't be received
> > because they will be blocked by the master port's MAC filter. Linuxptp
> > tries to put the net device in ALLMULTI/PROMISC mode,
>
> Untrue.

I'm sorry, then what does this code from raw.c do?

> 	mreq.mr_ifindex = index;
> 	mreq.mr_type = PACKET_MR_ALLMULTI;
> 	mreq.mr_alen = 0;
> 	if (!setsockopt(fd, SOL_PACKET, option, &mreq, sizeof(mreq))) {
> 		return 0;
> 	}
> 	pr_warning("setsockopt PACKET_MR_ALLMULTI failed: %m");
>
> 	mreq.mr_ifindex = index;
> 	mreq.mr_type = PACKET_MR_PROMISC;
> 	mreq.mr_alen = 0;
> 	if (!setsockopt(fd, SOL_PACKET, option, &mreq, sizeof(mreq))) {
> 		return 0;
> 	}
> 	pr_warning("setsockopt PACKET_MR_PROMISC failed: %m");


> > but DSA doesn't
> > pass this on to the master port, which does the actual reception.
> > The master port is put in promiscous mode when the slave ports are
> > enslaved to a bridge.
> >
> > Also, even with software-corrected timestamps, one can observe a
> > negative path delay reported by linuxptp:
> >
> > ptp4l[55.600]: master offset          8 s2 freq  +83677 path delay     -2390
> > ptp4l[56.600]: master offset         17 s2 freq  +83688 path delay     -2391
> > ptp4l[57.601]: master offset          6 s2 freq  +83682 path delay     -2391
> > ptp4l[58.601]: master offset         -1 s2 freq  +83677 path delay     -2391
> >
> > Without investigating too deeply, this appears to be introduced by the
> > correction applied by linuxptp to t4 (t4c: corrected master rxtstamp)
> > during the path delay estimation process (removing the correction makes
> > the path delay positive).
>
> No.  The root cause is the time stamps delivered by the hardware or
> your driver.  That needs to be addressed before going forward.

How can I check that the timestamps are valid?

Regards,
-Vladimir

> Thanks,
> Richard