Debugging a kernel freeze

[Victor Ascroft]

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.