Re: [PATCH] drm/i915: Invariably invalidate before ctx switch

Chris Wilson
2014-04-03T07:05:48Z

On Wed, Apr 02, 2014 at 10:30:23PM -0700, Ben Widawsky wrote:
> We have been setting the bit which was originally BIOS dependent since:
> commit f05bb0c7b624252a5e768287e340e8e45df96e42
> Author: Chris Wilson <chris@chris-wilson.co.uk>
> Date: Sun Jan 20 16:33:32 2013 +0000
>
> drm/i915: GFX_MODE Flush TLB Invalidate Mode must be '1' for scanline waits
>
> Therefore, we do not need to try to figure it out dynamically and we can
> just always invalidate the TLBs.
>
> It's a partial revert of:
> commit 12b0286f49947a6cdc9285032d918466a8c3f5f9
> Author: Ben Widawsky <ben@bwidawsk.net>
> Date: Mon Jun 4 14:42:50 2012 -0700
>
> drm/i915: possibly invalidate TLB before context switch
>
> The original commit attempted to only invalidate when necessary
> (very much a relic from the old days). Now, we can just always invalidate.
>
> I guess the old TODO still exists. Since we seem to have abandoned ILK
> contexts however, there isn't much point in even remembering.
>
> Cc: Chris Wilson <chris@chris-wilson.co.uk>
> Signed-off-by: Ben Widawsky <ben@bwidawsk.net>

Seems reasonable, except in most cases (execbuffer) there will be
a following cache-invalidate as part of the move-to-gpu.

Reviewed-by: Chris Wilson <chris@chris-wilson.co.uk>

ILK ctx, never forget.
-Chris

--
Chris Wilson, Intel Open Source Technology Centre