Debugging a kernel freeze

Hello, I have a iMX6 running a 4.9 kernel with a custom kernel driver communicating with a FPGA over PCIe. The driver is not built in to the kernel but loaded as a module after complete boot up. During the running of the system, after a few hours the kernel completely freezes. No kernel panics or stack traces, nothing. I have access to the serial console. In such a scenario what are the ways to debug and try locating the source of the problem? I am not looking for a solution for my problem but things or approaches one can go about trying while trying to fix such a scenario? Thank you for any pointers in advance. Regards.