etnaviv: drm: Be able to mark end of context init

Add etna_cmd_stream_mark_end_of_context_init(..) which stores the current
offset of the cmd stream as offset_end_of_context_init. This information
will be used to downgrade a cmd stream flush to a noop.

Signed-off-by: Christian Gmeiner <cgmeiner@igalia.com>
Reviewed-by: Lucas Stach <l.stach@pengutronix.de>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/25849>

src/etnaviv/drm/etnaviv_cmd_stream.c

@@ -230,6 +230,9 @@ void etna_cmd_stream_flush(struct etna_cmd_stream *stream, int in_fence_fd,
 	if (gpu->dev->use_softpin)
 		req.flags |= ETNA_SUBMIT_SOFTPIN;
 
+	if (stream->offset == priv->offset_end_of_context_init && !out_fence_fd)
+		is_noop = true;
+
 	if (unlikely(is_noop))
 		ret = 0;
 	else
@@ -254,6 +257,7 @@ void etna_cmd_stream_flush(struct etna_cmd_stream *stream, int in_fence_fd,
 	priv->submit.nr_relocs = 0;
 	priv->submit.nr_pmrs = 0;
 	priv->nr_bos = 0;
+	priv->offset_end_of_context_init = 0;
 }
 
 void etna_cmd_stream_reloc(struct etna_cmd_stream *stream,
@@ -284,6 +288,18 @@ void etna_cmd_stream_ref_bo(struct etna_cmd_stream *stream, struct etna_bo *bo,
 	bo2idx(stream, bo, flags);
 }
 
+void etna_cmd_stream_mark_end_of_context_init(struct etna_cmd_stream *stream)
+{
+   struct etna_cmd_stream_priv *priv = etna_cmd_stream_priv(stream);
+
+   /* 
+    * All commands before the end of context init are guaranteed to only alter GPU internal
+    * state and have no externally visible side effects, so we can skip the submit if the
+    * command buffer contains only context init commands.
+    */
+   priv->offset_end_of_context_init = stream->offset;
+}
+
 void etna_cmd_stream_perf(struct etna_cmd_stream *stream, const struct etna_perf *p)
 {
 	struct etna_cmd_stream_priv *priv = etna_cmd_stream_priv(stream);

src/etnaviv/drm/etnaviv_drmif.h

@@ -206,6 +206,8 @@ void etna_cmd_stream_reloc(struct etna_cmd_stream *stream, const struct etna_rel
 void etna_cmd_stream_ref_bo(struct etna_cmd_stream *stream,
 		struct etna_bo *bo, uint32_t flags);
 
+void etna_cmd_stream_mark_end_of_context_init(struct etna_cmd_stream *stream);
+
 /* performance monitoring functions:
  */
 

src/etnaviv/drm/etnaviv_priv.h

@@ -134,6 +134,7 @@ struct etna_cmd_stream_priv {
 	struct etna_pipe *pipe;
 
 	uint32_t last_timestamp;
+	uint32_t offset_end_of_context_init;
 
 	/* submit ioctl related tables: */
 	struct {