On 2013-11-22 09:19, [email protected] wrote:
I have just written a PHC driver for NTP and tested it on this system: Supermicro SYS-50150EHF-D525 which has a pair of Intel 82574L NICs which have IEEE 1588 hardware-based timestamping. I'm using NTP dev 4.2.7p397 onLinux kernel 3.12 with linuxptp. One of the PHCs is sync'd via PTP to an FEIZyfer Gsync GrandMaster, which is in turn synced via 5MHz to the USNO Master Clock #2.I'm running ptp4l to sync PHC1 to the GrandMaster. Then NTP is reading the refclocks PHC0, PHC1 and an NTP server on the LAN ptp2: ntpq -p remote refid st t when poll reach delay offset jitter ============================================================================== +PHC(0) .PTP. 0 l 15 16 377 0.000 0.000 0.000 *PHC(1) .PTP. 0 l 2 16 377 0.000 -0.001 0.000 +ptp2 .IRIG. 1 u 38 64 377 0.123 0.018 0.007 After about 15 hours the loopstats shows a s.d. of +/- 0.579 microsec with peak-peak 2.52 microsec (3,073 points). Very superb. However, it took fully 75 minutes at start to converge. It took that long to remove 20ms of phase error. I have never seen such a slow convergence. Very smooth too. I have tested the NMEA/ATOM drivers on this system and the convergence was the normal few minutes. Any suggestions? Can email plots.. Rich Schmidt Time Service Dept US Naval Observatory
You do not appear to be delivering PPS via kernel PPS, an ATOM driver, or user mode PPS, with PHC0/1 as your prefer peer. You want to see o before your ref clock, so that may explain slow convergence compared to using the ATOM driver! Does Linux PTP have an interface to provide timestamp interrupts to Linux kernel PPS, and can you set that up, or add user mode PPS to your driver? There are example user mode PPS patches for Raspberry Pi Raspian Linux NTP, and in ports/winnt/ntpd/ntp_iocompletionport.c. You could compare your loopstats to your ref clock peerstats, and also your driver clockstats if you are generating them? Loopstats offset/jitter should track your ref clock peerstats offset/jitter exactly, and comparing to your clockstats may point you to causes. -- Take care. Thanks, Brian Inglis _______________________________________________ questions mailing list [email protected] http://lists.ntp.org/listinfo/questions
