no external screen (HDMI) on early boot process with GRUB2 and EFI

[address@hidden]

Hi,

I already described my problem here
https://forums.opensuse.org/showthread.php/542146-no-second-(external)-screen-on-early-boot-process-with-HDMI?s=2dbf177801547bff45956cc97bc17933

In short words:

Steps seen on laptop screen only:

 * boot with GRUB2 and EFI from an unencrypted partition (later /boot/efi)
   GRUB uses /boot/efi/EFI/opensuse/grub.cfg
 * GRUB password request (text mode) for the encrypted partitions (LVM
   with /(root), /home, swap)
 * GRUB uses /boot/grub2/grub.cfg
 * GRUB boot menu comes up (graphic mode), selection of openSUSE
 * GRUB loads initial ramdisk and kernel
 * boot.log starts

A little bit later I can see the boot.log also also on my external screen.

The screen is connected via an DVI-D-HDMI and HDMI cable to my docking
station (adapter in docking station).

videoinfo says:
/grub> videoinfo//
//List of supported video modes://
//Adapter 'EFI GOP driver'//
//* 0x000 1024 x 768 x 31...
/

I tried to set a sufficient resolution for my external screen in both
grub.cfg (gfxmode), but it didn't work.

My old monitor connected directly via DVI-D cable to the docking station
worked.

Is maybe the used video driver efi_gop 'too poor' to operate the
external screen via HDMI or is it more a general technical problem, so I
need the kernel to address the external monitor correctly?

Thanks a lot!