[Linuxptp-users] Issue with initial high jitter(Path Delay Variation)

[Sujatha G. <suj...@gm...>]

Hi All,

I am facing issue with ptp4l application where the SLAVE to MASTER Path
Delay Variation is very high for initial few seconds and it is taking ~62
seconds for the slave clock to get stabilized.

This issue is seen 4 out of 5 times when the system is executed with the
same software.

Our target is to have the slave clock get stabilized with in 5 seconds from
s0 state and the jitter should be less than 100 ns.

In Success case(Logs provided below)
-  slave clock is taking  186 - 173  = 13 seconds for stabilization
-  Jitter is with 100ns after stabilization

In Failire case (Logs provided below)
- slave clock is taking 340 - 278 = 62 seconds for stabilization
-  jitter is maintained below 100ns after stabilization but it is very very
high compared to previous case during the stabilization stage

The issues observed in Failure case logs are ,
-  the Master time stamp and slave time stamp difference is very high
- at s1, adjtime called to adjust the slave time, but after that the  time
difference is more
- adjtime is called only once and after that the time adjustment is
happening only using adjfreq
- the maximum adjfreq can happen is 32767999, hence it is trying to adjust
the frequency using 32767999 for 29 times and then gradually frequency
value is decreased to adjust the slave time and for this it is taking 62
seconds
- This behaviour is observed 4 out of 5 times and suddenly for 1 time the
systems starts behaving correctly where I got the the success logs.
- I have tried to set the pi_offset_const in default.cfg to 1.0 thinking
that if the time difference between MASTER and SLAVE goes beyond 1 second
adjtime might get called. But the value changed in default.cfg does not get
reflected in the software. I have verified it in pi.c file by
printing s->max_offset value , This value is always 0

- Based on the logs below, the time difference between MASTER and SLAVE is
not going beyond 1 second so I experimented the pi_offset_const with 0.5 as
well but could not see any difference.


Can somebody help me to solve this issue. I have been struggling with this
issue for a long time and currently exhausted with all the possible
options.Any pointers on this issue could be a great help to me.


Thank you all in advance.


*Success Logs:*
ptp4l[167.314]: driver changed our HWTSTAMP options
ptp4l[167.320]: tx_type   1 not 1
ptp4l[167.324]: rx_filter 1 not 12
ptp4l[167.329]: port 1: INITIALIZING to LISTENING on INITIALIZE
ptp4l[167.340]: port 0: INITIALIZING to LISTENING on INITIALIZE
ptp4l[168.503]: port 1: new foreign master 001ec0.fffe.8614b5-1
ptp4l[172.512]: selected best master clock 001ec0.fffe.8614b5
ptp4l[172.527]: port 1: LISTENING to UNCALIBRATED on RS_SLAVE
ptp4l[173.676]: master offset -1474359190506508 s0 freq      +0 path delay
     1391
ptp4l[174.677]: master offset -1474359190525503 s1 freq  -18994 path delay
     3347
ptp4l[175.676]: master offset       1686 s2 freq  -17308 path delay
 3347
ptp4l[175.681]: port 1: UNCALIBRATED to SLAVE on MASTER_CLOCK_SELECTED
ptp4l[176.677]: master offset       3777 s2 freq  -14712 path delay
 1391
ptp4l[177.677]: master offset       1412 s2 freq  -15943 path delay
 1425
ptp4l[178.677]: master offset        208 s2 freq  -16724 path delay
 1425
ptp4l[179.677]: master offset       -209 s2 freq  -17078 path delay
 1391
ptp4l[180.677]: master offset        228 s2 freq  -16704 path delay
886
ptp4l[181.678]: master offset       -210 s2 freq  -17074 path delay
886
ptp4l[182.677]: master offset        222 s2 freq  -16705 path delay
381
ptp4l[183.677]: master offset       -293 s2 freq  -17153 path delay
458
ptp4l[184.678]: master offset       -370 s2 freq  -17318 path delay
458
ptp4l[185.678]: master offset       -171 s2 freq  -17230 path delay
381
ptp4l[186.678]: master offset        -38 s2 freq  -17148 path delay
370
ptp4l[187.678]: master offset        -92 s2 freq  -17214 path delay
354
ptp4l[188.678]: master offset         40 s2 freq  -17109 path delay
354
ptp4l[189.678]: master offset        -31 s2 freq  -17168 path delay
349
ptp4l[190.678]: master offset        103 s2 freq  -17044 path delay
346
ptp4l[191.678]: master offset         26 s2 freq  -17090 path delay
346
ptp4l[192.678]: master offset        -35 s2 freq  -17143 path delay
344
ptp4l[193.678]: master offset       -102 s2 freq  -17220 path delay
344
ptp4l[194.678]: master offset         11 s2 freq  -17138 path delay
344
ptp4l[195.682]: master offset        -51 s2 freq  -17197 path delay
340
ptp4l[196.678]: master offset         62 s2 freq  -17099 path delay
340
ptp4l[197.678]: master offset         14 s2 freq  -17128 path delay
337
ptp4l[198.678]: master offset        -66 s2 freq  -17204 path delay
337
ptp4l[199.678]: master offset         72 s2 freq  -17086 path delay
337
ptp4l[200.678]: master offset          5 s2 freq  -17131 path delay
339
ptp4l[201.680]: master offset        -54 s2 freq  -17189 path delay
339



*Failure Logs:*
ptp4l[270.981]: selected /dev/ptp0 as PTP clock
ptp4l[271.014]: driver changed our HWTSTAMP options
ptp4l[271.020]: tx_type   1 not 1
ptp4l[271.024]: rx_filter 1 not 12
ptp4l[271.028]: port 1: INITIALIZING to LISTENING on INITIALIZE
ptp4l[271.040]: port 0: INITIALIZING to LISTENING on INITIALIZE
ptp4l[272.323]: port 1: new foreign master 001ec0.fffe.8614b5-1
ptp4l[276.323]: selected best master clock 001ec0.fffe.8614b5
ptp4l[276.328]: port 1: LISTENING to UNCALIBRATED on RS_SLAVE
ptp4l[278.496]: master offset -1475113437970290 s0 freq      +0 path delay
     7176
ptp4l[279.496]: master offset -1475113437987402 s1 freq  -17112 path delay
     7176
ptp4l[280.496]: master offset -1000000284 s2 freq -32767999 path delay
 7176
ptp4l[280.501]: port 1: UNCALIBRATED to SLAVE on MASTER_CLOCK_SELECTED
ptp4l[281.501]: master offset -967516976 s2 freq -32767999 path delay
 5595
ptp4l[282.497]: master offset -932832166 s2 freq -32767999 path delay
 -1927882
ptp4l[283.497]: master offset -898147308 s2 freq -32767999 path delay
 -3861360
ptp4l[284.497]: master offset -865395833 s2 freq -32767999 path delay
 -3861360
ptp4l[285.497]: master offset -831350054 s2 freq -32767999 path delay
 -5155742
ptp4l[286.497]: master offset -799893170 s2 freq -32767999 path delay
 -3861360
ptp4l[287.497]: master offset -765847415 s2 freq -32767999 path delay
 -5155742
ptp4l[288.497]: master offset -733096073 s2 freq -32767999 path delay
 -5155742
ptp4l[289.497]: master offset -698230049 s2 freq -32767999 path delay
 -7270253
ptp4l[290.498]: master offset -665478434 s2 freq -32767999 path delay
 -7270253
ptp4l[291.498]: master offset -632727061 s2 freq -32767999 path delay
 -7270253
ptp4l[292.498]: master offset -598665729 s2 freq -32767999 path delay
 -8580243
ptp4l[293.498]: master offset -564280251 s2 freq -32767999 path delay
-10214326
ptp4l[294.498]: master offset -531529599 s2 freq -32767999 path delay
-10213455
ptp4l[295.498]: master offset -497634061 s2 freq -32767999 path delay
-11357800
ptp4l[296.498]: master offset -464882705 s2 freq -32767999 path delay
-11357800
ptp4l[297.498]: master offset -432131187 s2 freq -32767999 path delay
-11357800
ptp4l[298.498]: master offset -399380745 s2 freq -32767999 path delay
-11356929
ptp4l[299.498]: master offset -366628279 s2 freq -32767999 path delay
-11357800
ptp4l[300.498]: master offset -333876738 s2 freq -32767999 path delay
-11357800
ptp4l[301.498]: master offset -301125423 s2 freq -32767999 path delay
-11357800
ptp4l[302.498]: master offset -268374981 s2 freq -32767999 path delay
-11356929
ptp4l[303.498]: master offset -235623646 s2 freq -32767999 path delay
-11356929
ptp4l[304.498]: master offset -202794969 s2 freq -32767999 path delay
-11434176
ptp4l[305.498]: master offset -170043447 s2 freq -32767999 path delay
-11434176
ptp4l[306.498]: master offset -137787552 s2 freq -32767999 path delay
-10938890
ptp4l[307.502]: master offset -105035853 s2 freq -32767999 path delay
-10938890
ptp4l[308.498]: master offset  -72284835 s2 freq -32767999 path delay
-10938890
ptp4l[309.498]: master offset  -39533393 s2 freq -32767999 path delay
-10938890
ptp4l[310.498]: master offset   -6782000 s2 freq -6799112 path delay
-10938890
ptp4l[311.498]: master offset     240469 s2 freq -1811243 path delay
-10938890
ptp4l[312.498]: master offset     607326 s2 freq -1372245 path delay
 -9465521
ptp4l[313.502]: master offset     -82486 s2 freq -1879859 path delay
 -7416620
ptp4l[314.499]: master offset    1773547 s2 freq  -48572 path delay
 -7416620
ptp4l[315.499]: master offset    -306599 s2 freq -1596654 path delay
 -5288386
ptp4l[316.498]: master offset     452990 s2 freq -929044 path delay
 -4482990
ptp4l[317.498]: master offset    1379304 s2 freq +133167 path delay
 -4482990
ptp4l[318.499]: master offset   -1209889 s2 freq -2042235 path delay
 -2033615
ptp4l[319.499]: master offset    -570670 s2 freq -1765983 path delay
-667937
ptp4l[320.499]: master offset     942311 s2 freq -424203 path delay
-429615
ptp4l[321.499]: master offset    1361863 s2 freq +278042 path delay
-429615
ptp4l[322.499]: master offset     877075 s2 freq +201813 path delay
-233274
ptp4l[323.499]: master offset     657429 s2 freq +245290 path delay
-233274
ptp4l[324.499]: master offset     256206 s2 freq  +41295 path delay
 -94051
ptp4l[325.499]: master offset     101446 s2 freq  -36603 path delay
482
ptp4l[326.499]: master offset     116561 s2 freq   +8946 path delay
 3951
ptp4l[327.499]: master offset      91065 s2 freq  +18418 path delay
 3951
ptp4l[328.499]: master offset      53869 s2 freq   +8542 path delay
 5785
ptp4l[329.499]: master offset      26391 s2 freq   -2775 path delay
 7659
ptp4l[330.499]: master offset      16293 s2 freq   -4956 path delay
 3184
ptp4l[331.499]: master offset       2694 s2 freq  -13667 path delay
 4398
ptp4l[332.500]: master offset       -982 s2 freq  -16535 path delay
 4398
ptp4l[333.500]: master offset        856 s2 freq  -14992 path delay
 1800
ptp4l[334.500]: master offset       -614 s2 freq  -16205 path delay
 1024
ptp4l[335.500]: master offset      -1311 s2 freq  -17086 path delay
585
ptp4l[336.500]: master offset      -1493 s2 freq  -17661 path delay
585
ptp4l[337.500]: master offset      -1094 s2 freq  -17710 path delay
585
ptp4l[338.500]: master offset       -684 s2 freq  -17628 path delay
585
ptp4l[339.503]: master offset       -178 s2 freq  -17328 path delay
494
ptp4l[340.500]: master offset        -45 s2 freq  -17248 path delay
399
ptp4l[341.500]: master offset        -16 s2 freq  -17233 path delay
399
ptp4l[342.500]: master offset         32 s2 freq  -17189 path delay
362
ptp4l[343.500]: master offset        112 s2 freq  -17100 path delay
328
ptp4l[344.500]: master offset        -42 s2 freq  -17220 path delay
328
ptp4l[345.499]: master offset        -26 s2 freq  -17217 path delay
328
ptp4l[346.500]: master offset         12 s2 freq  -17187 path delay
328
ptp4l[347.500]: master offset         42 s2 freq  -17153 path delay
328
ptp4l[348.500]: master offset       -138 s2 freq  -17320 path delay
333
ptp4l[349.500]: master offset       -102 s2 freq  -17326 path delay
333
ptp4l[350.500]: master offset        -73 s2 freq  -17327 path delay
336
ptp4l[351.500]: master offset        -29 s2 freq  -17305 path delay
337
ptp4l[352.500]: master offset          7 s2 freq  -17278 path delay
336
ptp4l[353.500]: master offset         39 s2 freq  -17244 path delay
334
ptp4l[354.500]: master offset         73 s2 freq  -17198 path delay
332
ptp4l[355.500]: master offset        104 s2 freq  -17145 path delay
330
ptp4l[356.500]: master offset        -41 s2 freq  -17259 path delay
330
ptp4l[357.500]: master offset         -5 s2 freq  -17235 path delay
330


Best Regards,
Sujatha