[Intel-gfx] [PATCH] drm/i915/byt: Avoid tweaking evaluation thresholds

[Brown, Len]

> It sucks, but I guess this is better than dead machines. I'd say let's
> wait another 1-2 weeks for tested-bys to trickle in, and if it does fix
> the problem then let's apply it. rps keeps on sucking, that's
> unfortunately not news at all.
> 
> Acked-by: Daniel Vetter <daniel.vetter at ffwll.ch>

I have 3 machines that I can hang in under 10 minutes.
They are different types of baytrail: n3540, j1900, z3775.

With this revert applied, all  three machines have
the same stress test for over 7 days without failure.

I disagree with an action plan that includes the word "wait".

Tested-by: Len Brown <len.brown at intel.com>

Indeed, my question is if we can turn off GFX p-states entirely
on this hardware.  Is there a command line parameter I can
use to do that?  If we have one, it will certainly make
troubleshooting orders of magnitude easier.

Note that the bisected patch

     commit 8fb55197e64d5988ec57b54e973daeea72c3f2ff
     Author: Chris Wilson <chris at chris-wilson.co.uk>
     Date:   Tue Apr 7 16:20:28 2015 +0100
    
     drm/i915: Agressive downclocking on Baytrail

was applied to Linux 3.17-rc1.
Thus, this revert should be applied to every stable release back to 3.17.

thanks,
-Len