[Bug 97822] Split screen/display corruption issue on HP EliteOne 800 G2 23-in Touch AIO

[bugzilla-daemon at freedesktop.org]

https://bugs.freedesktop.org/show_bug.cgi?id=97822

--- Comment #72 from Jani Nikula <jani.nikula at intel.com> ---
(In reply to Robert Wolf from comment #63)
> I have installed my linux image a few years ago for older PCs with BIOS,
> therefore I was still using old boot method - PXEboot and grub from MBR from
> disk. Now I have prepared (U)EFI netboot, because of disabled Legacy
> Support. As we wanted to test if the duplicated image on external monitor
> works with UEFI boot, we have started Ubuntu 16.10 from USB flash as UEFI.
> We have not disabled i915 KMS and we expected that the image will be shown
> again only on upper half. But the image was displayed on whole screen! We
> have enabled Legacy Support and the image was again only on upper half. Then
> again Legacy Support disabled and image was again OK. So we have
> coincidentally found the BUG in this BIOS - if the Legacy Support is
> enabled, (1) image is not by default cloned to connected external output,
> (2) with standard Linux i915 KMS and xorg-intel video drivers the image is
> squeezed to upper half of screen on internal output, even if the resolution
> is correct. If Legacy Support is disabled, everything works fine - image is
> duplicated to external monitor right after switch on (even the HP logo is
> duplicated) and image is displayed correctly on internal output even with
> i915 KMS and xorg intel driver.

This is not a surprising find. If the machine ships Windows with UEFI boot,
that's likely the only combo that was ever tested.

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