[Intel-gfx] [PATCH 4/9] drm/i915: add post-flush store dw workaround

[Jesse Barnes]

On Tue, 25 Sep 2012 10:49:28 +0200
Daniel Vetter <daniel at ffwll.ch> wrote:

> On Wed, Sep 19, 2012 at 01:28:58PM -0700, Jesse Barnes wrote:
> > Several platforms need this to flush the CS write buffers.
> 
> Chris spent quite some effort to dump less crap into the rings on gen6,
> and your description here sounds like we only need this when flushing
> write caches. Or it might only apply to CS writes (in which case this is
> at the wrong spot). In any case, can you please double check where exactly
> we need this and only add it there, with a neat comment explaining things
> added?

"write caches" as in "any time we do a store dw and want to read the
result coherently" is my understanding.

> I'm bitching because afair the CS stuff the windows driver emits (of which
> I've seen some traces) only emits one such 8x MI_WRITE block per batch,
> whereas your code here would emit 2 such 2x MI_WRITE blocks.

Doing it once should be sufficient, I guess I need to split this out
(probably a good idea anyway for comment & naming purposes).

-- 
Jesse Barnes, Intel Open Source Technology Center