grub2 fails to load with DP1.2 (but not DP1.1)

[Georg Lipps]

I observed a very strange behaviour and have not found a solution so far:

Legacy BIOS
GRUB2 (2.02-2ubuntu8.13)
Nvidia Quadro K420
ASUS PB27U 4k monitor connected via display port

The monitor allows to select DP1.1 (30Hz@4k) and DP1.2 (60Hz@4k) via OSD. With DP1.1 computer boots up normally but it would be required to later change manually to 60Hz.

With DP1.2 the BIOS messages (POST) are seen, then a short cursor blink in the left upper corner and the systems halts with a blank screen (I can exclude that grub continues with the boot up process since I cannot ping the machine).

I tried:

GRUB_GFXMODE "1024*768*8"

and GRUB_TERMINAl "console"

reinstalling MBR

Always the same picture: DP1.1 no problem, DP1.2 no GRUB.

One more oddity: If a boot in DP1.1 and then switch the monitor to DP1.2 during GRUB the boot process continues normally and I end with a graphic session 60Hz@4k as intended.

It appears that only the inital grub2 loading is affected somehow.

[Georg Lipps (georg-lipps)]

I did some research. In fact GRUB2 is unable to load under these conditions:

* booting with BIOS (not UEFI)
* Nvidia graphics adapter
* usage of display port

The failure to boot is only observed with GRUB not when Windows boots directly.

I guess the graphics adapter is probed at the start of GRUB and fails for some reason. Could please somebody look into this?

Some references:

https://www.reddit.com/r/linuxquestions/comments/c1r3pu/grub_wont_load_when_connected_to_monitor_via/

https://forum.level1techs.com/t/odd-displayport-grub2-boot-issue/136745/15

[Launchpad Janitor (janitor)]

Status changed to 'Confirmed' because the bug affects multiple users.

[kurdt (kurdt-)]

I'm also affected by this. But in my case the display shows "unconnected cable". If the display is turned off at GRUB load everything goes fine. If the display is turned on, GRUB seems to be stucked

[Mate Kukri (mkukri)]

This seems like an issue with NVIDIA's legacy BIOS VESA ROM. Perhaps try UEFI boot, which is likely less buggy on modern VGA cards.

I doubt we will be able to do much unless someone with affected hardware can submit a patch.