How to debug no video output for grub on UEFI on ARM?

[Andre]

Hi,

I cross-compiled GRUB for ARM with UEFI as platform. The target system is a
Tegra3 board, unfortunately I don't know the specifics.

I know I can load and run GRUB on this device, as I was able to make it
read a grub.cfg on the ESP root with two lines:  "sleep 10" and then
"reboot" and the machine did reboot after 10 seconds.
This is to say that a lot has already happened: it loaded the gpt_part
module and probably a bunch of others in order to read, parse and execute
the configuration file.

Right now my problem is that I cannot get GRUB to output to the video
screen. My understanding is that GRUB would use the UEFI GOP to interact
with the screen. I made sure to include "efi_gop" module on my grub image,
along with video, gfxterm, gfxmenu and a few others (at one point I made an
image that included all modules from the lib/grub/arm-efi to no effect in
getting video out). I am out of ideas of what to do to investigate why I
don'get video output.

Would you have any suggestions on what I could try to get video output?
Is there any way to get GRUB to dump debug logs to the ESP root? Do you
think it would be of any help for this problem?

Thank you,
Andre