The 06/25/2018 14:43, Richard Hill wrote: > 1. The hardware nanosecond counter is not the same as PTP nanoseconds. PTP > time is held as > a variable, not by FEC > 2. The PPS-OUT signal does fire each second, but is not necessarily aligned > to PTP 0 > nanoseconds
This will not be an issue for offset measurement purposes correct? > 3. MAC/PHY resets will kill PPS-OUT (eg link down/up) > 4. To get sub 100ns accuracy, you're likely going to need external hardware > to control the > system clock by measuring the difference between GPS-PPS and PPS-OUT. (You > can then do > fine adjustment of PTP time) I think as Richard said, the idea now is just connecting 1PPS to the FEC directly, now the time served by Grandmaster should be accurate enough. One thing I am unsure of (and unsure how to accurately measure), Should I be worried about possible latency/jitter of synching ptp time to system clock on the slave devices (with phc2sys -a -r)? > 5. In my experience, PPS-in via GPIO just has far too much jitter to be > useful. So have you actually connected PPS to an FEC ENET_1588_EVENT#_IN pin on the imx, and modify the driver to use this for adjusting clock frequency? Thank you for sending these points my way. -- Rob ------------------------------------------------------------------------------ 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
