On 02/21/2014 08:20 PM, Paul Berry wrote: > On 21 February 2014 19:15, Kenneth Graunke <kenn...@whitecape.org > <mailto:kenn...@whitecape.org>> wrote: > > The blitter is completely ignorant of MSAA buffer layouts, so any > attempt to use BLT paths with MSAA buffers is likely to break > spectacularly. > > In most cases, BLORP handles MSAA blits, so we never hit this bug. > Until recently, it also wasn't worth fixing, since Meta couldn't handle > MSAA either, so there was nothing to fall back to. But now there is. > > +143 piglit tests on Broadwell (which doesn't have BLORP support). > Surprisingly, three also start failing. No changes on Ivybridge. > > > That actually doesn't surprise me too much. Since color buffers use an > array-like sample layout (sample N in the Nth layer), trying to use the > blitter on a multisampled buffer just gets you sample 0 from each pixel. > Which for some tests is good enough to pass (even though the blit is > actually doing the wrong thing). So it's possible that a few of these > tests that were passing by luck with the blitter don't yet have proper > Meta support :)
That makes a lot of sense. For UMS buffers, it got sample 0, which was enough to fool a few not-very-picky tests. But it still wrongly ignored samples >= 1. And it would probably break horribly for IMS buffers. I can definitely believe the meta code needs more baking. :) > Signed-off-by: Kenneth Graunke <kenn...@whitecape.org > <mailto:kenn...@whitecape.org>> > --- > src/mesa/drivers/dri/i965/intel_blit.c | 4 ++++ > 1 file changed, 4 insertions(+) > > diff --git a/src/mesa/drivers/dri/i965/intel_blit.c > b/src/mesa/drivers/dri/i965/intel_blit.c > index df85dc9..cedb230 100644 > --- a/src/mesa/drivers/dri/i965/intel_blit.c > +++ b/src/mesa/drivers/dri/i965/intel_blit.c > @@ -165,6 +165,10 @@ intel_miptree_blit(struct brw_context *brw, > mesa_format src_format = > _mesa_get_srgb_format_linear(src_mt->format); > mesa_format dst_format = > _mesa_get_srgb_format_linear(dst_mt->format); > > + /* The blitter doesn't understand multisampling at all. */ > + if (src_mt->num_samples > 0 || dst_mt->num_samples > 0) > + return false; > + > > > You might consider moving this check up to the top of the function, > since it doesn't depend on src_format or dst_format. But it's not a big > deal. Either way, the patch is: > > Reviewed-by: Paul Berry <stereotype...@gmail.com > <mailto:stereotype...@gmail.com>> Done. Thanks a ton for the review, Paul! --Ken
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