On Wed, Jul 20, 2022 at 12:06:43PM +0200, Jakub Raczyński wrote: > I was trying to setup gPTP using linuxptp (ptp4l + phc2sys) that would allow > two way synchronization using ntpd. Setup without ntpd (synchronizing > CLOCK_REALTIME) seems to be working perfectly. > However with ntpd is that when in network there is no external gPTP Master > available and device does become Master itself it may synchronize itself to > its own shm memory. > > > phc2sys is run using: /usr/sbin/phc2sys -a -r -r -f /etc/ptp4l.cfg -E ntpshm > -M 4
That is not expected to work. phc2sys has only one servo and ntpshm can be used only in one direction. You would need a second phc2sys instance with an option to only synchronize the PHC, when the port is in master state. As a workaround, you could write a script that would monitor the state and start/stop phc2sys as needed. > While testing devices with gPTP we encountered, in my opinion, quite > inconsequential behavior. Using different setups, I set following flags and > had following outcome: > > > gmCapable = 0 , slaveOnly = 0 -> OK > gmCapable = 1 , slaveOnly = 0 -> OK > gmCapable = 0 , slaveOnly = 1 -> Cannot mix 1588 slaveOnly with 802.1AS > !gmCapable > gmCapable = 1 , slaveOnly = 1 -> OK > > > Frankly, I would expect combination of "gmCapable = 1 , slaveOnly = 1" to > fail with than "gmCapable = 0 , slaveOnly = 1". > > > > I would like to ask for reasoning behind that combination block and not the > other. Since SlaveOnly flag performs as expected, even for gPTP setup. I'm not sure. If slaveOnly is 1, the clock will not ever be a grandmaster, i.e. not try to send sync messages. What would be different with gmCapable of 0? -- Miroslav Lichvar _______________________________________________ Linuxptp-users mailing list Linuxptp-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/linuxptp-users
