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

2 files changed, 27 insertions, 6 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;
diff --git a/src/gallium/drivers/r300/r300_state.c b/src/gallium/drivers/r300/r300_state.c
index bc6c67dd034..84d9da3ad9d 100644
--- a/src/gallium/drivers/r300/r300_state.c
+++ b/src/gallium/drivers/r300/r300_state.c
@@ -549,6 +549,10 @@ static void*
         dsa->z_stencil_control |=
             (r300_translate_depth_stencil_function(state->depth.func) <<
                 R300_Z_FUNC_SHIFT);
+    } else {
+        /* We must enable depth test, otherwise occlusion queries won't work. */
+        dsa->z_buffer_control |= R300_Z_ENABLE;
+        dsa->z_stencil_control |= R300_ZS_ALWAYS;
     }
 
     /* Stencil buffer setup. */
@@ -632,11 +636,13 @@ static void*
     OUT_CB_REG(R500_FG_ALPHA_VALUE, dsa->alpha_value);
     END_CB;
 
+    /* We must enable depth test, otherwise occlusion queries won't work.
+     * We setup a dummy zbuffer to silent the CS checker, see emit_fb_state. */
     BEGIN_CB(dsa->cb_zb_no_readwrite, 10);
     OUT_CB_REG(R300_FG_ALPHA_FUNC, dsa->alpha_function);
     OUT_CB_REG_SEQ(R300_ZB_CNTL, 3);
-    OUT_CB(0);
-    OUT_CB(0);
+    OUT_CB(R300_Z_ENABLE);
+    OUT_CB(R300_ZS_ALWAYS);
     OUT_CB(0);
     OUT_CB_REG(R500_ZB_STENCILREFMASK_BF, 0);
     OUT_CB_REG(R500_FG_ALPHA_VALUE, dsa->alpha_value);
@@ -645,8 +651,8 @@ static void*
     BEGIN_CB(dsa->cb_fp16_zb_no_readwrite, 10);
     OUT_CB_REG(R300_FG_ALPHA_FUNC, dsa->alpha_function_fp16);
     OUT_CB_REG_SEQ(R300_ZB_CNTL, 3);
-    OUT_CB(0);
-    OUT_CB(0);
+    OUT_CB(R300_Z_ENABLE);
+    OUT_CB(R300_ZS_ALWAYS);
     OUT_CB(0);
     OUT_CB_REG(R500_ZB_STENCILREFMASK_BF, 0);
     OUT_CB_REG(R500_FG_ALPHA_VALUE, dsa->alpha_value);
@@ -792,12 +798,14 @@ void r300_mark_fb_state_dirty(struct r300_context *r300,
     /* Now compute the fb_state atom size. */
     r300->fb_state.size = 2 + (8 * state->nr_cbufs);
 
-    if (r300->cbzb_clear)
+    if (r300->cbzb_clear) {
         r300->fb_state.size += 10;
-    else if (state->zsbuf) {
+    } else if (state->zsbuf) {
         r300->fb_state.size += 10;
         if (r300->hyperz_enabled)
             r300->fb_state.size += 8;
+    } else if (state->nr_cbufs) {
+        r300->fb_state.size += 10;
     }
 
     /* The size of the rest of atoms stays the same. */