The 12V/2A supply (24 Watts) should be lots to run the 820c (assuming that you don’t have a very power hungry mezzanine board attached). and your test with a 12V/4A supply didn’t change anything. I am assuming that the wires from the supply to the 820c are not too long (~1m) and of sufficient gauge to deliver the necessary current to the board.
I think you can eliminate my power supply idea from your list of potential causes of the issue.
I read through the boot log, it appears that the Qualcomm proprietary loaders (messages beginning with “[SBD] -”) get through with no issue, then LK (messages with integer time stamps) is started with no issue, then finally the Linux kernel (massages with real time stamps) get started. The Linux kernel seems to be doing fine bringing things up and gets all 4 cores running then tries to bring up the SDCard controller.
That’s when something goes wrong. There is no SDCard in the slot in the setup pictures so I don’t think that is the issue, maybe it just happens to be at the time of the crash which was also right after the 4 cores were powered up. The watch dog then trips, and the system goes back to the Qualcomm proprietary boot loader, which realises that the problem is a watchdog timeout and it proceeds to generate a XBLRamDump Image. Finally the Qualcomm proprietary boot loader stops and is waiting for a debugger to look into the problem.
At this point I agree it is a kernel SW issue, but beyond my debugging skills.
No longer a Qualcomm employee
looking for a new opportunity.