Monotonic clock on Jetpack 6.0

[user117897]

We are in the process of updating from Jetpack 5.1.1 to Jetpack 6.0 using the AGX Orin Devkit. One of the applications of our system requires very precise time stamping to synchronize data coming from a peripheral device. On Jetpack 5.1.1 this code is working well, however since updating to Jetpack 6.0 we are now seeing some unusual clock drift from the monotonic clock on the AGX.

I am curious if there are any differences in the way the monotonic clock on the Orin is configured between the two Jetpack versions? Or any other related changes?

[user117897]

Adding a little more info here. We verified that the frequency hopping is specifically in MONO_RAW by emitting a square wave on GPIO and comparing against a function analyzer (frequency was measured over a moving 500ms window).

We would expect this behavior from MONO, but not MONO_RAW.

[ShaneCCC]

Could you get the same from JP5 to compare.

Thanks

[ShaneCCC]

Bibek

Could you help to check if any internal report for this regression.

Thanks

[user117897]

Here is a similar graph from JP5.

On Jetpack 5 there are similar amplitude frequency hops in MONOTONIC_RAW, however, the hops are closer to 0.25 seconds in size which results in 0.25 * 200ppm = ~50us of integrated clock deviation which is easier to work around. On Jetpack 6 the minimum duration of a hop is 2 full seconds (and often much longer).

[user117897]

Hi Shane,

Just following up with this issue. Do you have any update? Can you point us towards any relevant drivers that might have changed between Jetpack 5 and 6? Is the clocksource driver for the oscillator tegra234-timer?

Any assistance would be greatly appreciated!

Thanks!

[ShaneCCC]

We are looking into it will update to you once get result.

Thanks

[user117897]

Hi Shane,

I saw that Jetpack 6.1 was recently released. Do you know if any of the changes might have any affect on this issue?

Thanks!

[Agtonomy]

Has this issue been resolved?
It looks like I may be seeing similar issue with AGX Orin Jetpack 6.2.
Before the upgrade we had Jetpack 5.1.2 and the problem did not exit.

[ShaneCCC]

Ran the test for 24 hours (100ms burst), I do not see such jump with CLOCK_MONOTONIC when compared to the host machine.
Clock monotonic is in sync with system clocksource and that is running accurately when compared to the host machine.

(Logs attached).

lab@lab-linux:~/kkartik$ ./compare.py clock_monotonic_test_03.txt

Summary:
------------------------------
Total elapsed time:      24:01:02.094
Average difference:       99.54 ms
Maximum difference:       102 ms
  Previous Difference Timestamp: 2024-10-05 16:52:10.209
  Current Elapsed Time Timestamp: 2024-10-05 16:52:10.311
Minimum difference:       77 ms
  Previous Difference Timestamp: 2024-10-06 14:18:46.849
  Current Elapsed Time Timestamp: 2024-10-06 14:18:46.92

compare.py (2.8 KB)