I am evaluating linuxptp for use in an embedded system. The basic architecture is as follows: +-------------+ +-------------+ +-------------+ | | | | | | | | | | | | | GRANDMASTER |<--->| Embedded PC |<-->| Custom board| | (PC) | | (Intel) | | | | | | | | | +-------------+ +-------------+ +-------------+
The Embedded system is constituted by an embedded PC (Intel based) and a custom board both running Linux and it is intended to be connected to an external PC (also Linux) Both the Embedded PC is running kernel 4.14.30 and the Custom board, kernel 4.14.0, both 32-bits. I compiled linuxptp 3.1.1 for both. As the custom board does not support hardware timestamp, I am experimenting with the software timestamp. I forced the custom board to client mode: sudo ptp4l -i eth0 -S -s -m -q step_threshold=0.00001 And the Embedded PC works as grandmaster for the Custom board: sudo ptp4l -i eth_am -S -m -q step_threshold=0.00001 I noticed that sometimes the master offset starts increasing as if the clock was no longer being updated. Unfortunately I did not save an instance of the log when this anomaly happened. I saved a sample of the log after running similar commands on two Fitlet PCs running Ubuntu Mate 20.04LTS (kernel 5.4.0, 64-bits OS), also running linuxptp 3.1.1 compiled in. I noticed what looks like an important difference between both configurations. This is the log of the custom board: custom_board:~$ sudo ptp4l -i eth0 -S -s -m -q step_threshold=0.00001 ptp4l[23715.187]: port 1: INITIALIZING to LISTENING on INIT_COMPLETE ptp4l[23715.187]: port 0: INITIALIZING to LISTENING on INIT_COMPLETE ptp4l[23721.896]: selected local clock 000a35.fffe.000122 as best master ptp4l[23728.111]: selected local clock 000a35.fffe.000122 as best master ptp4l[23735.085]: selected local clock 000a35.fffe.000122 as best master ptp4l[23742.999]: selected local clock 000a35.fffe.000122 as best master ptp4l[23749.230]: selected local clock 000a35.fffe.000122 as best master ptp4l[23755.780]: selected local clock 000a35.fffe.000122 as best master ptp4l[23761.675]: port 1: new foreign master aabbcc.fffe.ddee66-1 ptp4l[23762.677]: selected local clock 000a35.fffe.000122 as best master ptp4l[23765.675]: selected best master clock aabbcc.fffe.ddee66 ptp4l[23765.675]: foreign master not using PTP timescale ptp4l[23765.675]: port 1: LISTENING to UNCALIBRATED on RS_SLAVE ptp4l[23767.674]: master offset -519361 s0 freq +100000000 path delay 64850 ptp4l[23768.674]: master offset -519678 s0 freq +100000000 path delay 64850 ptp4l[23769.674]: master offset -523460 s0 freq +100000000 path delay 65099 ptp4l[23770.674]: master offset -521308 s0 freq +100000000 path delay 65275 ptp4l[23771.674]: master offset -525323 s0 freq +100000000 path delay 65275 ptp4l[23772.674]: master offset -528631 s0 freq +100000000 path delay 65318 ptp4l[23773.675]: master offset -527435 s0 freq +100000000 path delay 65318 ptp4l[23774.675]: master offset -528132 s0 freq +100000000 path delay 65451 ptp4l[23775.675]: master offset -533678 s0 freq +100000000 path delay 65972 ptp4l[23776.675]: master offset -531624 s0 freq +100000000 path delay 65972 ptp4l[23777.675]: master offset -534432 s0 freq +100000000 path delay 66493 ptp4l[23778.675]: master offset -534855 s0 freq +100000000 path delay 65988 ptp4l[23779.675]: master offset -537967 s0 freq +100000000 path delay 66572 ptp4l[23780.675]: master offset -539110 s0 freq +100000000 path delay 66572 ptp4l[23781.675]: master offset -538102 s0 freq +100000000 path delay 65988 ptp4l[23782.675]: master offset -540316 s0 freq +100000000 path delay 66572 ptp4l[23783.675]: master offset -542282 s1 freq +99998711 path delay 66680 ptp4l[23784.675]: master offset 3549 s2 freq +99999069 path delay 66680 ptp4l[23784.675]: port 1: UNCALIBRATED to SLAVE on MASTER_CLOCK_SELECTED ptp4l[23785.675]: master offset 2215 s2 freq +99998938 path delay 66680 ptp4l[23786.675]: master offset 1182 s2 freq +99998836 path delay 66749 ptp4l[23787.676]: master offset 3788 s2 freq +99999100 path delay 66749 ptp4l[23788.676]: master offset 2412 s2 freq +99998965 path delay 66749 ptp4l[23789.676]: master offset 1775 s2 freq +99998903 path delay 66749 ptp4l[23790.676]: master offset 4067 s2 freq +99999136 path delay 66680 ptp4l[23791.676]: master offset 824 s2 freq +99998813 path delay 66749 ptp4l[23792.676]: master offset 3687 s2 freq +99999103 path delay 66749 ptp4l[23793.676]: master offset 3373 s2 freq +99999075 path delay 66749 ptp4l[23794.676]: master offset 6239 s2 freq +99999368 path delay 66749 ptp4l[23795.676]: master offset 9323 s2 freq +99999686 path delay 66838 ptp4l[23796.676]: master offset 8212 s2 freq +99999583 path delay 66838 ptp4l[23797.676]: master offset 6440 s2 freq +99999412 path delay 67000 ptp4l[23798.676]: master offset 10252 s2 freq +99999803 path delay 67602 ptp4l[23799.676]: master offset 6070 s2 freq +99999391 path delay 67602 ptp4l[23800.676]: master offset 5183 s2 freq +99999308 path delay 67602 ptp4l[23801.676]: master offset 6810 s2 freq +99999477 path delay 67602 ptp4l[23802.676]: master offset 7300 s2 freq +99999533 path delay 68151 ptp4l[23803.676]: master offset 7303 s2 freq +99999541 path delay 68151 ptp4l[23804.676]: master offset 8433 s2 freq +99999663 path delay 68151 ptp4l[23805.677]: master offset 8715 s2 freq +99999699 path delay 68151 ptp4l[23806.677]: master offset 6014 s2 freq +99999435 path delay 68151 The important difference between the above and the test with the Fitlets is on the clock column, all values are +100000000 or close to it, all positive values, whereas on the Fitlets, the values are much lower and alternate between positive and negative values as well as the offsets. So it occurred there could be some software issue in this fairly old kernel version that may have been fixed in more recent kernels. Or maybe it is has to do with 32-bits vs 64-bits OS. Or I am simply doing something very wrong. Any help to help me to identify and fix this problem is welcome. TIA.
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