Re: [Linuxptp-users] offset explosion and irregular phc offsets

[Julien H. <ju...@ya...>]

> Are you compiling phc2sys with the posix skin?
> That won't work, because then:
> clock_gettime(CLOCK_REALTIME) - xenomai clock
> clock_adjtime(CLOCK_REALTIME) - linux clock
> This might explain the strange jumps that you are seeing.

Not yet, It was my next step



I've just tried with a normal linux kernel 3.9.11 and linuxptp 1.3.
As with the other versions, I had to modify the phc2sys :
No "if" for function "clock_gettime" error checking.


because of the following error message :
phc2sys -s p13p1 -O 0 -m
phc2sys[707.070]: failed to read clock: Invalid argument


And the result is the same as for Xenomai :

[root@marctaSBC linuxptp-1.3]# phc2sys -s p13p1 -O 0 -m
phc2sys[1268.134]: phc offset   2303109 s0 freq      +0 delay   5771
phc2sys[1269.135]: phc offset   2327465 s1 freq  -52982 delay   5831
phc2sys[1270.135]: phc offset     -9203 s2 freq  -62185 delay   5906
phc2sys[1271.136]: phc offset     -6173 s2 freq  -61916 delay   5834
phc2sys[1272.136]: phc offset     -5173 s2 freq  -62768 delay   5827
phc2sys[1273.136]: phc offset     -6556 s2 freq  -65703 delay   5838
phc2sys[1274.136]: phc offset      5357 s2 freq  -55757 delay   5861
phc2sys[1275.136]: phc offset      1351 s2 freq  -58156 delay   5767
phc2sys[1276.137]: phc offset      1706 s2 freq  -57395 delay   5834
phc2sys[1277.137]: phc offset     -8482 s2 freq  -67072 delay   5868
...

phc2sys[1320.146]: phc offset      3595 s2 freq  -59386 delay   5805
phc2sys[1321.146]: phc offset     17521 s2 freq  -44381 delay   5829
phc2sys[1322.146]: phc offset    -22279 s2 freq  -78925 delay   5836
phc2sys[1323.146]: phc offset     11422 s2 freq  -51908 delay   5834
phc2sys[1324.147]: phc offset      4133 s2 freq  -55770 delay   5831
phc2sys[1325.147]: phc offset      2738 s2 freq  -55925 delay   5872
phc2sys[1326.147]: phc offset     -7330 s2 freq  -65172 delay   5832


and it becomes :

phc2sys[1379.624]: phc offset -70368744178266 s2 freq -500000 delay   5804
phc2sys[1380.624]: phc offset -70368744139611 s2 freq -500000 delay   5830
phc2sys[1381.624]: phc offset -70368744086343 s2 freq -500000 delay   5769
phc2sys[1382.624]: phc offset -70368744044388 s2 freq -500000 delay   5777


after a while...



> This is only the apparent offset within the ptp4l program. The actual
> offset is unknown to the program, but you can measure it using a PPS,
> for example (but your hardware doesn't have this).

Sure, but I thought that a low and stable value of this apparent offset and delay would give us an indication on the good behaviour of the mechanism. I can't measure this offset in hardware today.  I've got a high precision time stamping acquisition board and I will measure the overall offset including ptp, phc2sys and packets sending offset when my setup will be ready...


Thank you,

Julien.