[Mesa-dev] [PATCH] i965: Use RED for depth texture formats rather than INTENSITY.

[Kenneth Graunke]

While looking through the documentation, I found this in the Sandybridge
PRM (Volume 4, Part 1, Page 140):
"Use of sample_c with SURFTYPE_CUBE surfaces is undefined with the
 following surface formats: I24X8_UNORM, L24X8_UNORM, A24X8_UNORM,
 I32_FLOAT, L32_FLOAT, A32_FLOAT."

I haven't observed this to be true, but it suggests that we may want to
use other formats.

We already perform DEPTH_TEXTURE_MODE swizzling in the shaders, and
don't rely on the surface format to splat things appropriately.  So
using RED should work just as well as INTENSITY.

A few notes about the formats:
- R24_UNORM_X8_TYPELESS has the exact same properties as I24X8_UNORM.
- R16_UNORM and R32_FLOAT are additionally supported as a render target,
  while the old I16_UNORM/I32_FLOAT formats are not.
- R32_FLOAT_X8X24_TYPELESS is not supported as a render target, while
  the old format (R32G32_FLOAT) was.  However, it shares the same
  properties as the formats we use for Z24, so it should suffice.

This makes translate_tex_format and brw_blorp_surface_info::set
a bit more similar.

No Piglit or oglconform changes on Sandybridge.

Signed-off-by: Kenneth Graunke <kenneth at whitecape.org>
---
 src/mesa/drivers/dri/i965/brw_surface_formats.c | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

I found the text, wrote the patch, and tested it, so I figured I'd
send it out...but it doesn't seem to do anything useful, either...

diff --git a/src/mesa/drivers/dri/i965/brw_surface_formats.c b/src/mesa/drivers/dri/i965/brw_surface_formats.c
index 91e73d5..6b17553 100644
--- a/src/mesa/drivers/dri/i965/brw_surface_formats.c
+++ b/src/mesa/drivers/dri/i965/brw_surface_formats.c
@@ -695,17 +695,17 @@ translate_tex_format(struct brw_context *brw,
    switch( mesa_format ) {
 
    case MESA_FORMAT_Z16:
-      return BRW_SURFACEFORMAT_I16_UNORM;
+      return BRW_SURFACEFORMAT_R16_UNORM;
 
    case MESA_FORMAT_S8_Z24:
    case MESA_FORMAT_X8_Z24:
-      return BRW_SURFACEFORMAT_I24X8_UNORM;
+      return BRW_SURFACEFORMAT_R24_UNORM_X8_TYPELESS;
 
    case MESA_FORMAT_Z32_FLOAT:
-      return BRW_SURFACEFORMAT_I32_FLOAT;
+      return BRW_SURFACEFORMAT_R32_FLOAT;
 
    case MESA_FORMAT_Z32_FLOAT_X24S8:
-      return BRW_SURFACEFORMAT_R32G32_FLOAT;
+      return BRW_SURFACEFORMAT_R32_FLOAT_X8X24_TYPELESS;
 
    case MESA_FORMAT_RGBA_FLOAT32:
       /* The value of this BRW_SURFACEFORMAT is 0, which tricks the
-- 
1.8.4.4