> -----Original Message----- > From: Keller, Jacob E > Sent: Wednesday, May 22, 2019 1:28 PM > To: 'Sanjay Bhandari' <san...@ziffusion.com> > Subject: RE: [Linuxptp-users] question on "-a" option in phc2sys (and > boundary clock > etc.) > > > From: Sanjay Bhandari [mailto:san...@ziffusion.com] > > Sent: Wednesday, May 22, 2019 12:18 PM > > To: Richard Cochran <richardcoch...@gmail.com> > > Cc: linuxptp-us...@lists.sourceforge.net > > Subject: Re: [Linuxptp-users] question on "-a" option in phc2sys (and > > boundary clock > etc.) > > > > For this mode, the collection of clocks must be synchronized by an > > > external > program, for example phc2sys(8) in "automatic" mode. > > > I am confused about what this external program is supposed to do. If all > > the ports > share the same hardware clock device, then aren't these ports synchronized > already? > Once ptp4l sets the PHC on a slave port, won't all the other ports see the > same exact > time automatically? How can 2 clocks that share the same hardware clock > device be > even out of sync? > > I don't actually think there is an example of a driver where they are > actually all > synched to the same PHC device. A lot of hardware designs, even if the > hardware > uses one clock, end up with different effective clocks due to configuration > differences. > (i.e. the configuration for setting the effective frequency or time offset > differ). You > need to correct those differences properly. > > In the case where you actually have a single /dev/ptpX device for multiple > ports, then > yes you should not need to use phc2sys to keep them in synch. > > I think this later section refers to the "jbod" or "just a bunch of clocks" > mode. > > Regards, > Jake
Forgot the list on my original reply. Regards, Jake _______________________________________________ Linuxptp-devel mailing list Linuxptp-devel@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/linuxptp-devel
