r300g: fix occlusion queries when depth test is disabled or zbuffer is missing

From now on, depth test is always enabled in hardware.

If depth test is disabled in Gallium, the hardware Z function is set to ALWAYS.

If there is no zbuffer set, the colorbuffer0 memory is set as a zbuffer
to silence the CS checker.

This fixes piglit:
- occlusion-query-discard
- NV_conditional_render/bitmap
- NV_conditional_render/drawpixels
- NV_conditional_render/vertex_array

1 files changed, 13 insertions, 0 deletions

diff --git a/src/gallium/drivers/r300/r300_emit.c b/src/gallium/drivers/r300/r300_emit.c
index 874037ed9fd..5d6188e5120 100644
--- a/src/gallium/drivers/r300/r300_emit.c
+++ b/src/gallium/drivers/r300/r300_emit.c
@@ -439,6 +439,19 @@ void r300_emit_fb_state(struct r300_context* r300, unsigned size, void* state)
             OUT_CS_REG(R300_ZB_ZMASK_OFFSET, 0);
             OUT_CS_REG(R300_ZB_ZMASK_PITCH, surf->pitch_zmask);
         }
+    /* Set up a dummy zbuffer. Otherwise occlusion queries won't work.
+     * Use the first colorbuffer, we will disable writes in the DSA state
+     * so as not to corrupt it. */
+    } else if (fb->nr_cbufs) {
+        surf = r300_surface(fb->cbufs[0]);
+
+        OUT_CS_REG(R300_ZB_FORMAT, R300_DEPTHFORMAT_16BIT_INT_Z);
+
+        OUT_CS_REG(R300_ZB_DEPTHOFFSET, 0);
+        OUT_CS_RELOC(surf);
+
+        OUT_CS_REG(R300_ZB_DEPTHPITCH, 4 | R300_DEPTHMICROTILE_TILED);
+        OUT_CS_RELOC(surf);
     }
 
     END_CS;