[Intel-gfx] [PATCH] drm/i915: Disable execlists by default for gen8

[Michel Thierry]

On 7/7/2015 9:33 AM, Chris Wilson wrote:
> On Sat, Apr 11, 2015 at 09:41:37AM +0100, Chris Wilson wrote:
>> Bug reports are still coming in for late 4.0-rcX that indicate that
>> execlists causes GPU hangs following resume.
>>
>> Fixes regression from
>> commit d7f621e50704306c348ccb192f17047f1499f9bc
>> Author: Oscar Mateo <oscar.mateo at intel.com>
>> Date:   Thu Jul 24 17:04:49 2014 +0100
>>
>>      drm/i915/bdw: Enable Logical Ring Contexts (hence, Execlists)
>>
>> Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=89308
>
> Ping?
>
> Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=89915
>
> Bugs are still being reported where execlists is the culprit in 4.0.6.
> We have no advantages for execlists in 4.0, only performance and
> stability regressions, so what was the justification for keeping it
> enabled?
> -Chris
>
Hi,

I still think it's the same problem fixed by Peter 
(http://git.kernel.org/cgit/linux/kernel/git/stable/linux-stable.git/commit/?id=364aece01a2dd748fc36a1e8bf52ef639b0857bd).
The issue was a race between enabling the interrupts and completing the 
first batchbuffer, that's probably why we only saw it in chv, but it's 
the same code bdw uses.

v4.0.6 didn't get the fix,
http://git.kernel.org/cgit/linux/kernel/git/stable/linux-stable.git/tree/drivers/gpu/drm/i915/i915_drv.c?id=v4.0.6

Only v4.0.7:
http://git.kernel.org/cgit/linux/kernel/git/stable/linux-stable.git/tree/drivers/gpu/drm/i915/i915_drv.c?id=v4.0.7

-Michel