Re: [PATCH] intel: Fix emit_linear_blit to use DWORD aligned width blits

[Chris Wilson <chris@chris-wilson.co.uk>]

On Tue, 09 Nov 2010 11:34:52 +0000, Peter Clifton <pcjc2@cam.ac.uk> wrote:
> On Tue, 2010-11-09 at 10:52 +0000, Peter Clifton wrote:
> > On Sun, 2010-11-07 at 10:25 +0000, Chris Wilson wrote:
> 
> > I've not tried that yet, but the PRM does state that BLT pitch is in
> > DWORDs.
> 
> Gah.. the PRM is badly written in places! In one place it states DWORDs,
> then in another you get the actual detail:

Of course, I was reading another document which made no mention of the
tiling or dword restrictions ;-)

Contradictory, uncrossreferenced, incomplete docs are all we have. 

> Chris, I can try word-aligned if you wish, but am chasing some other
> random GPU hangs / crashes at the moment. Fun fun ;)

No need, life is too short.
 
> (PS. Any idea where batchbuffer containing 3D commands, but with a
> string of 6-8 MI_NOOP commands would come from? I can't find code to
> emit like that in MESA or the 2D driver - I am wondering if the buffer
> had become corrupted).

Keep digging and you'll find a reference to some silicon bugs for which
certain commands (in this case it's probably the URB_FENCE) must not cross
cache-lines. I'm guessing that the MI_NOOPs you've seen are due to us
aligning the following commands to meet such constraints.
-Chris

-- 
Chris Wilson, Intel Open Source Technology Centre