i915: Add an option for testing the effect of early Z in classic mode.

The early Z stuff is supposed to be unsafe without some more work in the
enable/disable path (in particular, how do we want to get it disabled on
the way out to the X Server?), but at the moment is 6% in OA.

2 files changed, 10 insertions, 0 deletions

diff --git a/src/mesa/drivers/dri/i915/i915_reg.h b/src/mesa/drivers/dri/i915/i915_reg.h
index b02e2c76286..84db58ea950 100644
--- a/src/mesa/drivers/dri/i915/i915_reg.h
+++ b/src/mesa/drivers/dri/i915/i915_reg.h
@@ -141,6 +141,7 @@
 /* p161 */
 #define _3DSTATE_DST_BUF_VARS_CMD	(CMD_3D | (0x1d<<24) | (0x85<<16))
 /* Dword 1 */
+#define CLASSIC_EARLY_DEPTH		(1<<31)
 #define TEX_DEFAULT_COLOR_OGL           (0<<30)
 #define TEX_DEFAULT_COLOR_D3D           (1<<30)
 #define ZR_EARLY_DEPTH                  (1<<29)
diff --git a/src/mesa/drivers/dri/i915/i915_vtbl.c b/src/mesa/drivers/dri/i915/i915_vtbl.c
index 6ecbc4709bc..2fca247af19 100644
--- a/src/mesa/drivers/dri/i915/i915_vtbl.c
+++ b/src/mesa/drivers/dri/i915/i915_vtbl.c
@@ -42,6 +42,7 @@
 #include "intel_regions.h"
 #include "intel_tris.h"
 #include "intel_fbo.h"
+#include "intel_chipset.h"
 
 #include "i915_reg.h"
 #include "i915_context.h"
@@ -611,6 +612,14 @@ i915_state_draw_region(struct intel_context *intel,
       }
    }
 
+   /* This isn't quite safe, thus being hidden behind an option.  When changing
+    * the value of this bit, the pipeline needs to be MI_FLUSHed.  And it
+    * can only be set when a depth buffer is already defined.
+    */
+   if (IS_945(intel->intelScreen->deviceID) && intel->use_early_z &&
+       depth_region->tiling != I915_TILING_NONE)
+      value |= CLASSIC_EARLY_DEPTH;
+
    if (depth_region && depth_region->cpp == 4) {
       value |= DEPTH_FRMT_24_FIXED_8_OTHER;
    }