We have a custom imx6 board. The board is based on the SABRE QP board. The two major differences are, we are using a Quad device, not a QuadPlus device, and also, we have 2GB total RAM instead of 1GB.
We're using SD3 as our boot device. During bring-up, we've ran into boot issues and started the thread: Can not boot custom iMX6 board from SD Card .Thanks to the answer we received in that thread, we managed to boot after running calibration. However we're now running into other problems.
After booting linux (and sometimes, *while* booting linux), at seemingly random times (after a few seconds, minutes, and in some cases, a couple hours), the system becomes completely unresponsive. There is no console output, ethernet connectivity is dead, etc. This appears to happen for no specific reason, it appears to be somewhat random. Nothing special is running on linux at the time of hang, it is just sitting there on the command line prompt (or sometimes in the middle of the boot process).
When this happens, we checked the supply rails and all appear to be OK. Also, to rule out any DRAM related issues, we ran overnight tests with the stress tester on the DDR3 chips (via the USB OTG interface), and all appears to be OK. We also ran DDR tests in u-boot and that seems to be OK as well. Similarly, when the board does boot and remain active for a couple hours, we run the linux memtester and we receive no errors there either.
We're not sure how to go about finding the problem. What could be possible sources of hang and how can we go about zeroing in on the problem?