r300g: implement fences using dummy relocations

So finally we have them.

1 files changed, 24 insertions, 11 deletions

diff --git a/src/gallium/drivers/r300/r300_flush.c b/src/gallium/drivers/r300/r300_flush.c
index 0db1365702..bfc15ceae7 100644
--- a/src/gallium/drivers/r300/r300_flush.c
+++ b/src/gallium/drivers/r300/r300_flush.c
@@ -37,11 +37,23 @@ static void r300_flush(struct pipe_context* pipe,
 {
     struct r300_context *r300 = r300_context(pipe);
     struct r300_atom *atom;
-    struct r300_fence **rfence = (struct r300_fence**)fence;
+    struct r300_winsys_bo **rfence = (struct r300_winsys_bo**)fence;
 
     if (r300->draw && !r300->draw_vbo_locked)
 	r300_draw_flush_vbuf(r300);
 
+    if (rfence) {
+        /* Create a fence, which is a dummy BO. */
+        *rfence = r300->rws->buffer_create(r300->rws, 1, 1,
+                                           PIPE_BIND_VERTEX_BUFFER,
+                                           PIPE_USAGE_STATIC,
+                                           R300_DOMAIN_GTT);
+        /* Add the fence as a dummy relocation. */
+        r300->rws->cs_add_reloc(r300->cs,
+                                r300->rws->buffer_get_cs_handle(*rfence),
+                                R300_DOMAIN_GTT, R300_DOMAIN_GTT);
+    }
+
     if (r300->dirty_hw) {
         r300_emit_hyperz_end(r300);
         r300_emit_query_end(r300);
@@ -70,16 +82,17 @@ static void r300_flush(struct pipe_context* pipe,
         r300->upload_vb_validated = FALSE;
         r300->upload_ib_validated = FALSE;
     } else {
-        /* Even if hw is not dirty, we should at least reset the CS in case
-         * the space checking failed for the first draw operation. */
-        r300->rws->cs_flush(r300->cs);
-    }
-
-    /* Create a new fence. */
-    if (rfence) {
-        *rfence = CALLOC_STRUCT(r300_fence);
-        pipe_reference_init(&(*rfence)->reference, 1);
-        (*rfence)->ctx = r300;
+        if (rfence) {
+            /* We have to create a fence object, but the command stream is empty
+             * and we cannot emit an empty CS. We must write some regs then. */
+            CS_LOCALS(r300);
+            OUT_CS_REG(RB3D_COLOR_CHANNEL_MASK, 0);
+            r300->rws->cs_flush(r300->cs);
+        } else {
+            /* Even if hw is not dirty, we should at least reset the CS in case
+             * the space checking failed for the first draw operation. */
+            r300->rws->cs_flush(r300->cs);
+        }
     }
 }