[Bug 108103] Failed to initialize GPU and Screen corruption at the top of the screen.

[bugzilla-daemon at freedesktop.org]

https://bugs.freedesktop.org/show_bug.cgi?id=108103

--- Comment #16 from Vasily Galkin <galkin-vv at ya.ru> ---
I have the similar problem: black screen with j4105 cpu, that reproduces only
with iommu enabled

My ASRock-J4105-ITX board during boot is identified as 
DMI: To Be Filled By O.E.M. To Be Filled By O.E.M./J4105-ITX, BIOS P1.40
08/06/2018

Gpu in lspci is identified as
00:02.0 VGA compatible controller: Intel Corporation Device 3185

If I enable VT-d in the EFI Setup and intel_iommu=on parameter, than I have
monitor becomes black (though, there is no gpu hang message) during X start (no
any screen corruption).

During the boot framebuffer console initializes, but contains an error message
(on 4.19.5 debian kernel, on previous kernels the message telled something
about GPU hang):

i915 0000:00:02.0: Failed to initialize GPU, declaring it wedged!

There is no error state:
# cat /sys/class/drm/card0/error
No error state collected

Than boot continues using framebuffer console and at the moment of lightdm
starting the screen becomes just black (ssh still works fine).

Disabling intel_iommu completely solves the problem.

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