[Intel-gfx] [PATCH 53/53] !UPSTREAM: drm/i915: Use MMIO flips

[Daniel Vetter]

On Thu, Jun 19, 2014 at 11:50 AM, Mateo Lozano, Oscar
<oscar.mateo at intel.com> wrote:
>> -----Original Message-----
>> From: Daniel Vetter [mailto:daniel.vetter at ffwll.ch] On Behalf Of Daniel
>> Vetter
>> Sent: Wednesday, June 18, 2014 10:01 PM
>> To: Mateo Lozano, Oscar
>> Cc: intel-gfx at lists.freedesktop.org
>> Subject: Re: [Intel-gfx] [PATCH 53/53] !UPSTREAM: drm/i915: Use MMIO
>> flips
>>
>> On Fri, Jun 13, 2014 at 04:38:11PM +0100, oscar.mateo at intel.com wrote:
>> > From: Sourab Gupta <sourab.gupta at intel.com>
>> >
>> > If we want flips to work, either we create an Execlists-aware version
>> > of intel_gen7_queue_flip, or we don't place commands directly in the
>> > ringbuffer.
>> >
>> > When upstreamed, this patch should implement the second option:
>>
>> Usually we just mention such requirements in the cover letter of the series
>> and don't include them.
>> -Daniel
>
> Well, since we have it here, there is something I wanted to ask about this:
>
> MODULE_PARM_DESC(use_mmio_flip, "use MMIO flips (-1=never, 0=driver discretion [default], 1=always)");
>
> The "driver discretion" option will blow up with Execlists :(
> How do I tackle this? an execlists version of intel_gen7_queue_flip? sanitizing use_mmio_flip when execlists get enabled? I really don´t have a preference...

Hm, usually we have it -1=per-platform defaults, 0=force disable,
1=force enable. Hooray for inconsistency. But anyway just make the
default with execlist be mmio flips. Tbh I don't see that much value
in this option, might as well kick it out and use mmio flips on gen7+
unconditionally for everything. Presuming they don't have any other
downsides.
-Daniel
-- 
Daniel Vetter
Software Engineer, Intel Corporation
+41 (0) 79 365 57 48 - http://blog.ffwll.ch