[Intel-gfx] screen freeze with 5.2-rc6 Dell XPS-13 skylake i915

[Chris Wilson]

Quoting James Bottomley (2019-06-29 19:56:52)
> The symptoms are really weird: the screen image is locked in place. 
> The machine is still functional and if I log in over the network I can
> do anything I like, including killing the X server and the display will
> never alter.  It also seems that the system is accepting keyboard input
> because when it freezes I can cat information to a file (if the mouse
> was over an xterm) and verify over the network the file contents. 
> Nothing unusual appears in dmesg when the lockup happens.
> 
> The last kernel I booted successfully on the system was 5.0, so I'll
> try compiling 5.1 to narrow down the changes.

It's likely this is panel self-refresh going haywire.

commit 8f6e87d6d561f10cfa48a687345512419839b6d8
Author: José Roberto de Souza <jose.souza at intel.com>
Date:   Thu Mar 7 16:00:50 2019 -0800

    drm/i915: Enable PSR2 by default

    The support for PSR2 was polished, IGT tests for PSR2 was added and
    it was tested performing regular user workloads like browsing,
    editing documents and compiling Linux, so it is time to enable it by
    default and enjoy even more power-savings.

Temporary workaround would be to set i915.enable_psr=0
-Chris