PLLAON as clock source over the air

[lennartha]

Hey everyone,

we have updated our AGX Xavier from Jetpack 32.3.1 to Jetpack 32.5.1. As the update changed the clock source for the can bus we have been following the instructions here together with the great discussion here in our lab to successfully bring the can bus back online, which is mission critical for us.

As we already have quite a number of robots deployed in the field we need to find a way to change the clock source over the air. This should be possible, as the over the air update from Jetpack 32.3.1 to 32.5.1 introduces those changes. We just need to find a way to reverse them.

Is there a way to change the clock source to PLLAON for can0 over the air once updated to 32.5.1?

[kayccc]

Sorry for the late response, is this still an issue to support?

[lennartha]

Hey @kayccc,
yes, this is very much still an issue for us where we need support.

[shgarg]

Hi lennartha,
There is no such provision rightnow to change clock after updated to 32.5 over the air or once system booted.
You need to change dtbs as mentioned in https://docs.nvidia.com/jetson/l4t/index.html#page/Tegra%20Linux%20Driver%20Package%20Development%20Guide/clocks.html#wwpID0E06B0HA

Thanks,
Shubhi

[lennartha]

Hey @shgarg, thank you so much for the swift response!
That is bad news for us.
Thank you for your reply anyway!

[lennartha]

@shgarg and @kayccc,
can you elaborate what exactly makes it impossible to reverse the over the air update of the clock source? Before running sudo apt dist-upgrade on the Xavier PLLAON is the default. Why do we need to flash it to revers that change?

[shgarg]

Hi lennartha,
Bpmp controls the clocks. It is disabled in bpmp dtb for the modules to save power and there is no way IMO to update bpmp dtb runtime.