gallium/radeon: fix (S)DMA read-after-write hazards

Reviewed-by: Alex Deucher <[email protected]>
Reviewed-by: Nicolai Hähnle <[email protected]>

2 files changed, 25 insertions, 0 deletions

diff --git a/src/gallium/drivers/radeon/r600_pipe_common.c b/src/gallium/drivers/radeon/r600_pipe_common.c
index cea6b7bce82..3e15b143700 100644
--- a/src/gallium/drivers/radeon/r600_pipe_common.c
+++ b/src/gallium/drivers/radeon/r600_pipe_common.c
@@ -149,6 +149,30 @@ void r600_need_dma_space(struct r600_common_context *ctx, unsigned num_dw)
 	}
 }
 
+/* This is required to prevent read-after-write hazards. */
+void r600_dma_emit_wait_idle(struct r600_common_context *rctx)
+{
+	struct radeon_winsys_cs *cs = rctx->dma.cs;
+
+	/* done at the end of DMA calls, so increment this. */
+	rctx->num_dma_calls++;
+
+	r600_need_dma_space(rctx, 1);
+
+	if (cs->cdw == 0) /* empty queue */
+		return;
+
+	/* NOP waits for idle on Evergreen and later. */
+	if (rctx->chip_class >= CIK)
+		radeon_emit(cs, 0x00000000); /* NOP */
+	else if (rctx->chip_class >= EVERGREEN)
+		radeon_emit(cs, 0xf0000000); /* NOP */
+	else {
+		/* TODO: R600-R700 should use the FENCE packet.
+		 * CS checker support is required. */
+	}
+}
+
 static void r600_memory_barrier(struct pipe_context *ctx, unsigned flags)
 {
 }
diff --git a/src/gallium/drivers/radeon/r600_pipe_common.h b/src/gallium/drivers/radeon/r600_pipe_common.h
index 47b73653e93..03449536b5b 100644
--- a/src/gallium/drivers/radeon/r600_pipe_common.h
+++ b/src/gallium/drivers/radeon/r600_pipe_common.h
@@ -598,6 +598,7 @@ struct pipe_resource *r600_resource_create_common(struct pipe_screen *screen,
 						  const struct pipe_resource *templ);
 const char *r600_get_llvm_processor_name(enum radeon_family family);
 void r600_need_dma_space(struct r600_common_context *ctx, unsigned num_dw);
+void r600_dma_emit_wait_idle(struct r600_common_context *rctx);
 
 /* r600_gpu_load.c */
 void r600_gpu_load_kill_thread(struct r600_common_screen *rscreen);