On Thu, Dec 27, 2018 at 06:56:27AM -0800, Richard Cochran wrote: > On Wed, Dec 26, 2018 at 11:33:32AM -0600, Keith Squier wrote: > > So one idea would be to > > configure ntpd/chronyd to take the PPS and then my application can pass the > > time using SHM. ntpd/chronyd can do their thing to smooth out and properly > > adjust the system clock. With the system clock being disciplined, I can > > then use phc2sys to synchronize the PHC to the system clock using something > > like "-s CLOCK_REALTIME -c eth0". (Do I need to use the -d option to pass > > /dev/pps0?) > > > > Are there any downsides to this? > > Yes, you are chaining two clock servos, one in ntpd and a second one > in phc2sys. That is an unnecessary source of error for your PTP > clients.
In addition, you lose the ability to time stamp the PPS from the GPS in hardware. ntpd and friends essentially use software time stamping, and depending on your kernel and platform, there will be significant additional error for this reason. BTW, I looked back at this thread, and Chris already answered your questions in some detail. Thanks, Richard _______________________________________________ Linuxptp-users mailing list Linuxptp-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/linuxptp-users
