Debugging DRM on a laptop?

[coypu%sdf.org@localhost]

Hi folks,

we're working on a drmkms update.
I'm testing it on a Dell XPS 9550. It's a laptop with a Skylake CPU.
It has a power button. The power button powers off, not reboot.
This means the dmesg buffer gets wiped.
No serial console as far as I know.

Now it reaches a point where the screen changes, but my DDB_COMMANDENTER
containing "reboot" won't do the expected thing. It's possible it's
hanging. I can't seem to blindly enter ddb.

Any suggestions to make debugging less painful?
Something like arm a watchdog to panic after some time.

I'm gonna experiment with sprinkling panic("XXX"); and see if this works
out.