[Intel-gfx] [PATCH] drm/i915: Disable DMC powersaving during GT operations

[Tvrtko Ursulin]

On 12/09/2017 13:45, Tvrtko Ursulin wrote:
> 
> On 12/09/2017 13:37, Chris Wilson wrote:
>> The DMC typifies the worst example of firmware: it overrides system
>> behaviour and is fubar. When no displays are active, the DMC appears to
>> continually toggle its control register trying to change display power
>> states. This in turn has the side effect of slowing down the GT by a few
>> orders of magntidue, making headless operations intolerably slow.
>>
>> This seems to affect all machines with dmc (so a byproduct of the dmc
>> code itself being shared) and severely limits throughput on the CI bxt
>> and triggers the watchdog for incomplete tests.
>>
>> Altenative suggestion is to blacklist all DMC firmware until it is
>> fixed.
> 
> I've sent this as https://patchwork.freedesktop.org/patch/154942/ some 
> time ago. You asked for a long code comment back then. :)
> 
> Anyway, I don't mind we merge one of the two since it is taking an 
> eternity to get this fixes in the firmware. So:
> 
> Reviewed-by: Tvrtko Ursulin <tvrtko.ursulin at intel.com>

I take it back, there was a reason in shape of another firmware bug 
which made us put this patch on hold. Imre might know the status of that 
one.

Regards,

Tvrtko