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

["Ville Syrjälä" <ville.syrjala@linux.intel.com>]

On Thu, Apr 03, 2014 at 08:05:35AM +0100, Chris Wilson wrote:
> 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.

Except we still move_to_gpu() before the context switch. My fbc related
patch to change that order never got merged.

> 
> Reviewed-by: Chris Wilson <chris@chris-wilson.co.uk>
> 
> ILK ctx, never forget.
> -Chris
> 
> -- 
> Chris Wilson, Intel Open Source Technology Centre
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-- 
Ville Syrjälä
Intel OTC