[Bug 215001] Regression in 5.15, Firmware-initialized graphics console selects FB_VGA16, screen corruption

[bugzilla-daemon at bugzilla.kernel.org]

https://bugzilla.kernel.org/show_bug.cgi?id=215001

--- Comment #2 from Artem S. Tashkinov (aros at gmx.com) ---
CC'ing the relevant mailing list.

> A regression in kernel 5.15 causes FB_VGA16 (vga16fb) to fail to detect that
> it has been passed a firmware-initialized graphics bitmap instead of a
> character-mapped 80x25 display.  It takes ownership of the console, instead
> of passing control to FB_EFI, FB_VESA, FB_SIMPLE and so on.  This results in
> writing ASCII bytes into the RGB bitmap, with random bits appearing in the
> first few scanlines of the screen.  (The remainder of the screen is
> untouched, e.g. Grub's window saying it is loading the Linux kernel.)
> 
> Once udevd loads the appropriate modesetting driver (in my case, amdgpu), the
> graphics screen is (re)initialized properly and becomes usable.
> 
> Kernel config options CONFIG_SYSFB_SIMPLEFB, CONFIG_FB_SIMPLE, CONFIG_FB_EFI,
> and CONFIG_FB_VESA had no effect when toggled on and off.
> 
> Workaround: Disabling CONFIG_FB_VGA16 blocks vga16fb from grabbing the
> console, allowing the EFI framebuffer to properly take ownership of the
> console.
> 
> This bug is a duplicate of #214603.  Credit goes to that reporter for
> disabling FB_VGA16 as a workaround.  I would have updated that report rather
> than file a duplicate, except that #214603 does not have its metadata
> (product, component, version, regression, or even its summary fields) set
> correctly.  Hopefully this new report will be seen by the correct
> maintainers.

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