Bug#794393: xserver-xorg-video-intel: Backport version causes hang on resume from suspend on Jessie

[Jerome <an.inbox@free.fr>]

On 08/04/2015 02:56 AM, Vincent Cheng wrote:
> Please file a bug report upstream (see instructions above) and let us 
> know the bug number so we can mark it as forwarded in the BTS.

When I went to report upstream as indicated I noticed the bug was 
already reported and closed as fixed upstream (no details):
https://bugs.freedesktop.org/show_bug.cgi?id=90342

I went looking for more info on the upstream fix and found this other bug:
https://bugs.freedesktop.org/show_bug.cgi?id=89915

The comment #7 there indicates a fix upstream in kernel 4.0.7. So I 
tried the Debian kernel 4.0.8-2 from testing (again, but this time 
without updating DRM+Mesa so still from Jessie). It hangs much less 
often but when it does the PC is locked solid.

I updated the FDO bug 90342 and asked for clarification on the fix. 
Either it's not the reference I found or the fix is only partial.

The FDO bug 89915 comment 2 suggested as a work-around using the kernel 
option 'i915.enable_execlists=0'. I tried it before testing kernel 4.0.8 
so on the stock Jessie 3.16 kernel and on two tests one was ok, and in 
the other the GPU hanged but recovered. I will make more tests, this may 
be a better option for now.
Will also try kernel 4.1 now in unstable.

TBC...

Thanks,

Jerome