[Bug 1853735] Re: grub2 fails to load with DP1.2 (but not DP1.1)

[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

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https://bugs.launchpad.net/bugs/1853735

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

Status in grub2 package in Ubuntu:
  New

Bug description:
  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 at 4k) and DP1.2 (60Hz at 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 at 4k as intended.

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

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