[Mesa-dev] [PATCH 3/3] i965/miptree: Stop retiling miptrees

[Nanley Chery]

On Wed, May 30, 2018 at 10:57:05PM +0100, Chris Wilson wrote:
> Quoting Nanley Chery (2018-05-30 21:44:35)
> > We previously retiled miptrees to work around limitations of the BLT
> > engine. BLORP fallbacks can overcome these, so we no longer have need
> > for retiling.
> > 
> > Removing retiling fixes a number of problems. If the row pitch was too
> > wide for the BLT engine, we retiled to linear and had the following
> > issues:
> > * We retiled on gen6+ platforms which don't actually use the blitter.
> > * We ignored miptree_create_for_bo's requests for tiled miptrees.
> > 
> > I don't know how to write a test for the last issue unfortunately. Also,
> > I haven't nominated this for stable releases, because of the amount of
> > churn needed - we'd have to pull in the series which stops using the
> > blitter on gen6+.
> > 
> > Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=106738
> > ---
> >  src/mesa/drivers/dri/i965/intel_mipmap_tree.c | 62 +------------------
> >  1 file changed, 1 insertion(+), 61 deletions(-)
> > 
> > diff --git a/src/mesa/drivers/dri/i965/intel_mipmap_tree.c b/src/mesa/drivers/dri/i965/intel_mipmap_tree.c
> > index 1c888d5210b..a57720b338a 100644
> > --- a/src/mesa/drivers/dri/i965/intel_mipmap_tree.c
> > +++ b/src/mesa/drivers/dri/i965/intel_mipmap_tree.c
> > @@ -509,46 +509,6 @@ free_aux_state_map(enum isl_aux_state **state)
> >     free(state);
> >  }
> >  
> > -static bool
> > -need_to_retile_as_linear(struct brw_context *brw, unsigned row_pitch,
> > -                         enum isl_tiling tiling, unsigned samples)
> > -{
> > -   if (samples > 1)
> > -      return false;
> > -
> > -   if (tiling == ISL_TILING_LINEAR)
> > -      return false;
> > -
> > -    /* If the width is much smaller than a tile, don't bother tiling. */
> > -   if (row_pitch < 64)
> > -      return true;
> > -
> > -   if (ALIGN(row_pitch, 512) >= 32768) {
> 
> For stable, you could at least fix these checks.
> 
> The BLT limit is 32767*4 for tiled surfaces, or borrow blt_pitch() from
> intel_blit.c (or export the checker from intel_blit.c)

Good call.

> -Chris