[Bug 77565] [BDW bisected]igt/pm_pc8 subcases cause system hang

[bugzilla-daemon at freedesktop.org]

https://bugs.freedesktop.org/show_bug.cgi?id=77565

Imre Deak <imre.deak at gmail.com> changed:

           What    |Removed                     |Added
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             Status|ASSIGNED                    |NEEDINFO

--- Comment #5 from Imre Deak <imre.deak at gmail.com> ---
(In reply to comment #4)
> (In reply to comment #3)
> > I think Imre has a patch to prevent runtime pm until the delayed rps work
> > has completed. That should address this.
> 
> I haven't checked yet this bug closer, but note that RC6/RPS is not enabled
> on BDW on current -nightly, I'm not sure if it's by overlook or on purpose.
> At least intel_disable_gt_powersave() is broken on BDW, since it'll try to
> disable RC6/RPS when it wasn't enabled in the first place. I posted a fix
> for this issue:
> 
> http://lists.freedesktop.org/archives/intel-gfx/2014-April/043695.html
> 
> As Daniel mentioned, in the same patchset there is also a patch to disable
> RPM until RC6/RPS is setup, but I'm not sure how that can make a difference
> on BDW, since we never enabled RC6/RPS there.

So I think the likely reason for the failure is that we don't enable RC6 but we
enable RPM (which depends on RC6). I suggest we fix this for now by correctly
reporting that RC6 is disabled and also keep RPM disabled based on this.

I cherry-picked the necessary patches from my VLV RPM branch for this and added
a new one that reports the correct RC6 status for BDW. It's an obvious fix as
it only keeps RPM disabled on BDW, but I still suggest it until BDW RC6 support
is fixed.

Daniel, if it's ok I can submit these patches separately from the rest of VLV
RPM stuff.

Please try the following branch:
https://github.com/ideak/linux/commits/bdw-rc6-rpm-fix

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