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

[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

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

Status in grub2 package in Ubuntu:
  Confirmed

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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