[Bug 108826] [GLK DSI] Black screen after grub - Ubuntu 18.04 - kernel latest tip 21.11.2018

[bugzilla-daemon at freedesktop.org]

https://bugs.freedesktop.org/show_bug.cgi?id=108826

--- Comment #13 from Jani Nikula <jani.nikula at intel.com> ---
One idea for debugging this:

1) boot *without* loading i915
2) get register dump using intel_reg (from the igt-gpu-tools [1])
3) modprobe i915 (presumably screen goes black at this point)
4) repeat the register dump

Alas I think intel_reg dump still falls short for MIPI DSI register dumps.
Someone from our side should provide a register spec file to use with intel_reg
to include all the relevant registers. (One of the reasons we're not dumping
the DSI registers by default is that reading them hangs the machine if DSI
isn't properly powered and clocks enabled.)

[1] https://cgit.freedesktop.org/drm/igt-gpu-tools/

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