On Thu, Jun 21, 2018 at 12:24:15AM -0700, Rob Cornall wrote: > I have a setup with master and slave working with ptp supported imx6 macs. > > On master I have a GPS module with serial reports and a pps signal hooked up > to a GPIO on the imx. > I know for a different nic like the i210, it has some specific SDPs that can > be used > for the PPS input - and this could be used to discipline the phc in the nic > directly. > > For my current setup I think I would have to discipline the system clock with > gspd > and ntp or chrony, then use phc2sys to sync the system clock to the phc? > > Is this on the right track? And would having the pps not directly into the mac > cause major accuracy issues? We were looking for +-1usec.
Synchronizing the PHC to the system clock will probably have a negative effect on the accuracy. It depends on the HW. For 1us accuracy it might be ok. A bigger problem might be with the PPS timestamping. I'm not sure how exactly it works with the imx. If the kernel is timestamping interrupts triggered by the PPS, that will probably add an error of at least few microseconds, maybe even few tens of microseconds. Unless you can measure the delay and make sure it's stable, 1us accuracy is not realistic. The PPS needs to be timestamped by the HW (like with the i210), or by the kernel polling the GPIO pin (assuming the reading is fast enough). -- Miroslav Lichvar ------------------------------------------------------------------------------ Check out the vibrant tech community on one of the world's most engaging tech sites, Slashdot.org! http://sdm.link/slashdot _______________________________________________ Linuxptp-users mailing list Linuxptp-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/linuxptp-users
