I should mention this is just using the default config file installed with ptp4l, but for full disclosure:
nvidia@jetson-randy2:~$ cat /etc/linuxptp/ptp4l.conf [global] # # Default Data Set # twoStepFlag 1 slaveOnly 0 priority1 128 priority2 128 domainNumber 0 clockClass 248 clockAccuracy 0xFE offsetScaledLogVariance 0xFFFF free_running 0 freq_est_interval 1 # # Port Data Set # logAnnounceInterval 1 logSyncInterval 0 logMinDelayReqInterval 0 logMinPdelayReqInterval 0 announceReceiptTimeout 3 syncReceiptTimeout 0 delayAsymmetry 0 fault_reset_interval 4 neighborPropDelayThresh 20000000 # # Run time options # assume_two_step 0 logging_level 6 path_trace_enabled 0 follow_up_info 0 hybrid_e2e 0 tx_timestamp_timeout 1 use_syslog 1 verbose 0 summary_interval 0 kernel_leap 1 check_fup_sync 0 # # Servo Options # pi_proportional_const 0.0 pi_integral_const 0.0 pi_proportional_scale 0.0 pi_proportional_exponent -0.3 pi_proportional_norm_max 0.7 pi_integral_scale 0.0 pi_integral_exponent 0.4 pi_integral_norm_max 0.3 step_threshold 0.0 first_step_threshold 0.00002 max_frequency 900000000 clock_servo pi sanity_freq_limit 200000000 ntpshm_segment 0 # # Transport options # transportSpecific 0x0 ptp_dst_mac 01:1B:19:00:00:00 p2p_dst_mac 01:80:C2:00:00:0E udp_ttl 1 udp6_scope 0x0E uds_address /var/run/ptp4l # # Default interface options # network_transport UDPv4 delay_mechanism E2E time_stamping hardware tsproc_mode filter delay_filter moving_median delay_filter_length 10 egressLatency 0 ingressLatency 0 boundary_clock_jbod 0 # # Clock description # productDescription ;; revisionData ;; manufacturerIdentity 00:00:00 userDescription ; timeSource 0xA0 On Fri, Dec 21, 2018 at 12:12 PM Randy Spruyt <randy.spr...@gmail.com> wrote: > Perhaps an elementary question, but maybe someone knows. The goal is to > have getnstimeofday() return a synchronized time value for 2 systems in a > kernel module. To do this, I would expect a simple "date" call from each > system to be pretty close, but it is not. > > > Using 2 x Jetson TX2 boards running Ubuntu 16.04 + ptp4l on Device 1 we > set an arbitrary date. > > ptp4l is running as a service on both: > /usr/sbin/ptp4l -f /etc/linuxptp/ptp4l.conf -i eth0 > > > set an arbitrary date on Device1: > > > nvidia@jetson-randy1:~$ sudo date -s "Dec 1 2015 04:00:00" > Tue Dec 1 04:00:00 UTC 2015 > > nvidia@jetson-randy1:~$ timedatectl > Local time: Tue 2015-12-01 04:00:01 UTC > Universal time: Tue 2015-12-01 04:00:01 UTC > RTC time: Wed 2017-03-01 12:12:00 > Time zone: Etc/UTC (UTC, +0000) > Network time on: no > NTP synchronized: no > RTC in local TZ: no > > > on Device2 we set a different arbitrary date: > > nvidia@jetson-randy2:~$ sudo date -s "Mar 10 2018 12:00:00" > Sat Mar 10 12:00:00 UTC 2018 > > nvidia@jetson-randy2:~$ timedatectl > Local time: Sat 2018-03-10 12:00:01 UTC > Universal time: Sat 2018-03-10 12:00:01 UTC > RTC time: Sat 2018-12-01 13:11:21 > Time zone: Etc/UTC (UTC, +0000) > Network time on: no > NTP synchronized: no > RTC in local TZ: no > > > Now we start ptp4l and phc2sys on each device. > > Device 1: > > Dec 1 04:02:06 jetson-randy1 systemd[1]: Started Precision Time Protocol > (PTP) service. > Dec 1 04:02:06 jetson-randy1 ptp4l: [83945.116] selected /dev/ptp0 as PTP > clock > Dec 1 04:02:06 jetson-randy1 ptp4l: [83945.117] port 1: INITIALIZING to > LISTENING on INITIALIZE > Dec 1 04:02:06 jetson-randy1 ptp4l: [83945.117] port 0: INITIALIZING to > LISTENING on INITIALIZE > Dec 1 04:02:08 jetson-randy1 ptp4l: [83946.193] port 1: new foreign > master 00044b.fffe.c56e7b-1 > Dec 1 04:02:12 jetson-randy1 ptp4l: [83950.194] selected best master > clock 00044b.fffe.c56e7b > Dec 1 04:02:12 jetson-randy1 ptp4l: [83950.195] assuming the grand master > role > Dec 1 04:02:12 jetson-randy1 ptp4l: [83950.195] port 1: LISTENING to > GRAND_MASTER on RS_GRAND_MASTER > > and > > nvidia@jetson-randy1:~$ sudo phc2sys -a -r -m > phc2sys[83977.835]: reconfiguring after port state change > phc2sys[83977.839]: selecting eth0 for synchronization > phc2sys[83977.840]: nothing to synchronize > > > Device 2: > > Mar 10 12:03:02 jetson-randy2 systemd[1]: Started Precision Time Protocol > (PTP) service. > Mar 10 12:03:02 jetson-randy2 ptp4l: [75310.117] selected /dev/ptp0 as PTP > clock > Mar 10 12:03:02 jetson-randy2 ptp4l: [75310.118] port 1: INITIALIZING to > LISTENING on INITIALIZE > Mar 10 12:03:02 jetson-randy2 ptp4l: [75310.118] port 0: INITIALIZING to > LISTENING on INITIALIZE > Mar 10 12:03:04 jetson-randy2 ptp4l: [75312.065] port 1: new foreign > master 00044b.fffe.c4cf6f-1 > Mar 10 12:03:08 jetson-randy2 ptp4l: [75316.066] selected best master > clock 00044b.fffe.c4cf6f > Mar 10 12:03:08 jetson-randy2 ptp4l: [75316.067] port 1: LISTENING to > UNCALIBRATED on RS_SLAVE > Mar 10 12:03:09 jetson-randy2 ptp4l: [75317.066] master offset > 71740766475479566 s0 freq +62500000 path delay 0 > Mar 10 12:03:10 jetson-randy2 ptp4l: [75318.066] master offset > 71740766475512626 s1 freq +62500000 path delay -4004 > Mar 10 12:03:12 jetson-randy2 ptp4l: [75320.068] master offset -124949356 > s2 freq -62449356 path delay -1768 > Mar 10 12:03:12 jetson-randy2 ptp4l: [75320.068] port 1: UNCALIBRATED to > SLAVE on MASTER_CLOCK_SELECTED > Mar 10 12:03:13 jetson-randy2 ptp4l: [75321.067] master offset -62730032 > s2 freq -37714839 path delay -4004 > Mar 10 12:03:14 jetson-randy2 ptp4l: [75322.068] master offset -24937060 > s2 freq -18740876 path delay -6240 > Mar 10 12:03:15 jetson-randy2 ptp4l: [75323.067] master offset -1649428 > s2 freq -2934362 path delay -4492000 > > and > > nvidia@jetson-randy2:~$ sudo phc2sys -a -r -m > phc2sys[75361.130]: reconfiguring after port state change > phc2sys[75361.133]: selecting CLOCK_REALTIME for synchronization > phc2sys[75361.133]: selecting eth0 as the master clock > phc2sys[75361.133]: CLOCK_REALTIME phc offset 71740802475284240 s0 freq > +30393 delay 5600 > phc2sys[75362.134]: CLOCK_REALTIME phc offset 71740802475284367 s1 freq > +30520 delay 5664 > phc2sys[75363.134]: CLOCK_REALTIME phc offset -400 s2 freq +30120 > delay 3136 > phc2sys[75364.135]: CLOCK_REALTIME phc offset 17 s2 freq +30417 > delay 3168 > phc2sys[75365.135]: CLOCK_REALTIME phc offset 502 s2 freq +30907 > delay 5664 > phc2sys[75366.136]: CLOCK_REALTIME phc offset 100 s2 freq +30656 > delay 5632 > phc2sys[75367.137]: CLOCK_REALTIME phc offset -117 s2 freq +30469 > delay 5664 > phc2sys[75368.137]: CLOCK_REALTIME phc offset -114 s2 freq +30437 > delay 5663 > phc2sys[75369.138]: CLOCK_REALTIME phc offset -174 s2 freq +30342 > delay 5568 > > yet if we run these commands quickly: > > nvidia@jetson-randy1:~$ date > Tue Dec 1 04:05:21 UTC 2015 > > nvidia@jetson-randy2:~$ date > Tue Dec 1 04:04:45 UTC 2015 > > we notice that the times are off by about 40 seconds. > > Thoughts? > Randy > >
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