Re: [PATCH] drm/i915: "Flush Me Harder" required on gen6+

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

On Thu, 28 Jun 2012 09:48:42 +0200, Daniel Vetter <daniel.vetter@ffwll.ch> wrote:
> The prep to remove the flushing list in
> 
> commit cc889e0f6ce6a63c62db17d702ecfed86d58083f
> Author: Daniel Vetter <daniel.vetter@ffwll.ch>
> Date:   Wed Jun 13 20:45:19 2012 +0200
> 
>     drm/i915: disable flushing_list/gpu_write_list
> 
> causes quite some decent regressions. We can fix this by setting the
> CS_STALL bit to ensure that the following seqno write happens only
> after the cache flush has completed. But only do that when the caller
> actually wants the flush (and not also when we invalidate caches
> before starting the next batch).
> 
> I've looked through all our ancient scrolls about gen6+ pipe control
> workarounds, and this seems to be indeed a legal combination: We're
> allowed to set the CS_STALL bit when we flush the render cache (which
> we do).
> 
> While yelling at this code, also pass back the return value from
> intel_emit_post_sync_nonzero_flush properly.
> 
> v2: Instead of emitting more pipe controls, set the CS_STALL bit on
> the write flush as suggested by Chris Wilson. It seems to work, too.
> 
> Cc: Eric Anholt <eric@anholt.net>
> Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=51436
> Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=51429
> Tested-by: Lu Hua <huax.lu@intel.com>
> Signed-Off-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Tested-by: Chris Wilson <chris@chris-wilson.co.uk>
Reviewed-by: Chris Wilson <chris@chris-wilson.co.uk>
-Chris

-- 
Chris Wilson, Intel Open Source Technology Centre