[Mesa-dev] [PATCH] i965: Don't try to use the hardware blitter for multisampled miptrees.

[Kenneth Graunke]

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.

Signed-off-by: Kenneth Graunke <kenneth at 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;
+
    /* The blitter doesn't support doing any format conversions.  We do also
     * support blitting ARGB8888 to XRGB8888 (trivial, the values dropped into
     * the X channel don't matter), and XRGB8888 to ARGB8888 by setting the A
-- 
1.9.0