[Mesa-dev] [PATCH 1/2] i965: Apply depthstencil alignment workaround when doing fast clears.

[Paul Berry]

On 12 March 2013 12:28, Eric Anholt <eric at anholt.net> wrote:

> Paul Berry <stereotype441 at gmail.com> writes:
>
> > Fast depth clears have the same depth/stencil alignment requirements
> > as other drawing operations.  Therefore, we need to call
> > brw_workaround_depthstencil_alignment() from both the clear and
> > drawing paths.
> >
> > Without this fix, we get image corruption if the following conditions
> > hold: (a) the first ever drawing operation to a depth miplevel (or the
> > first drawing operation after having used the texture for sampling) is
> > a clear, (b) the depth miplevel has a size that is eligible for fast
> > depth clears, and (c) the depth miplevel has an offset within the
> > miptree that isn't 8x8 aligned.
> >
> > Fixes piglit "depthstencil-render-miplevels" tests with size 273.
> >
> > NOTE: This is a candidate for stable branches
> > ---
> >  src/mesa/drivers/dri/i965/brw_clear.c | 6 +++++-
> >  1 file changed, 5 insertions(+), 1 deletion(-)
> >
> > diff --git a/src/mesa/drivers/dri/i965/brw_clear.c
> b/src/mesa/drivers/dri/i965/brw_clear.c
> > index 53d8e54..cde1a06 100644
> > --- a/src/mesa/drivers/dri/i965/brw_clear.c
> > +++ b/src/mesa/drivers/dri/i965/brw_clear.c
> > @@ -40,6 +40,8 @@
> >  #include "intel_mipmap_tree.h"
> >  #include "intel_regions.h"
> >
> > +#include "brw_context.h"
> > +
> >  #define FILE_DEBUG_FLAG DEBUG_BLIT
> >
> >  static const char *buffer_names[] = {
> > @@ -219,7 +221,8 @@ brw_fast_clear_depth(struct gl_context *ctx)
> >  static void
> >  brw_clear(struct gl_context *ctx, GLbitfield mask)
> >  {
> > -   struct intel_context *intel = intel_context(ctx);
> > +   struct brw_context *brw = brw_context(ctx);
> > +   struct intel_context *intel = &brw->intel;
> >
> >     if (!_mesa_check_conditional_render(ctx))
> >        return;
> > @@ -229,6 +232,7 @@ brw_clear(struct gl_context *ctx, GLbitfield mask)
> >     }
> >
> >     intel_prepare_render(intel);
> > +   brw_workaround_depthstencil_alignment(brw);
>
> It seems like this should be happening in brw_fast_clear(), either
> before before calling blorp or inside of it, instead of in the potential
> caller of brw_fast_clear().  Makes sense, though.
>

Chad made the same comment to me in person yesterday.  The reason I put it
here is to accommodate patch 2/2 (which allows
brw_workaround_depthstencil_alignment to avoid an unnecessary copy when
clearing the whole miplevel).  If I move the call to
brw_workaround_depthstencil_alignment into brw_fast_clear_depth(), then the
unnecessary copy will only be avoided when doing depth clears.  If I leave
it here, the unnecessary copy will be avoided for all clears.


>
> >     if (mask & BUFFER_BIT_DEPTH) {
> >        if (brw_fast_clear_depth(ctx)) {
>
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