Re: [Linuxptp-users] PTP through a bridge interface

[Rob C. <RCo...@si...>]

Hi Richard, I really appreciate you answering my questions so quickly.

I attached my logs where I ran a patched version of ptp4l on the GM device (I also attached this patch), the patch simply binds the socket to br0 and joins the multicast group on the br0 interface instead of the eth0 interface supplied In the command.
Our routes go through br0 as expected in this situation:

$ ip ro.3 
224.0.0.0/4 dev br0  scope link
...

And our DSA is setup as a 'dumb' switch, all unknown DA frames are flooded out all ports.

Also our particular marvell switch does not have the ptp support, we are aware that some versions do.

When seeing the slave adjusting its ptp clock this leads me to think everything works okay with this patch? Is this something that could be added as an option to ptp4l and merged in the future to support linux sw bridges?

Thanks,
Rob

-----Original Message-----
From: Richard Cochran <ric...@gm...> 
Sent: Tuesday, June 5, 2018 9:14 AM
To: Rob Cornall <RCo...@si...>
Cc: lin...@li...
Subject: Re: [Linuxptp-users] PTP through a bridge interface

On Tue, Jun 05, 2018 at 02:40:18PM +0000, Rob Cornall wrote:
> I mean #2, a marvell (mv88e6xxx DSA) is used where the cpu port is connected the imx6 ethernet controller.
> 
> Yes It is setup as a linux software bridge via brctl.
> 
> 
> We are aware that having a switch on the master will add some variation of latency, but is it not possible to send ptp packets and receive them through it?

If you leave the switch alone, not as a DSA device, then you can use
eth0 as a PTP port.

Once you make eth0 the CPU port of a DSA device, you cannot use eth0 any more, and you can't use the br0 for PTP either.

So your choice are:

1. Don't use DSA for the Marvell and run ptp4l on eth0.

2. Use the PTP support for the Marvel DSA device (new in Linux kernel v4.17)
   and run ptp4l on the external ports.

HTH,
Richard