drm/amd/display: Only use analog stream encoder with analog engine

[ Upstream commit 17ff034 ]

Some GPUs have analog connectors that work with a DP bridge chip
and don't actually have an internal DAC: Those should not use
the analog stream encoders.

Fixes: 5834c33 ("drm/amd/display: Add concept of analog encoders (v2)")
Signed-off-by: Timur Kristóf <timur.kristof@gmail.com>
Reviewed-by: Alex Hung <alex.hung@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>

Author: Timur Kristóf

drivers/gpu/drm/amd/display/dc/resource/dce100/dce100_resource.c

@@ -979,7 +979,10 @@ struct stream_encoder *dce100_find_first_free_match_stream_enc_for_link(
 	struct dc_link *link = stream->link;
 	enum engine_id preferred_engine = link->link_enc->preferred_engine;
 
-	if (dc_is_rgb_signal(stream->signal))
+	/* Prefer analog engine if the link encoder has one.
+	 * Otherwise, it's an external encoder.
+	 */
+	if (dc_is_rgb_signal(stream->signal) && link->link_enc->analog_engine != ENGINE_ID_UNKNOWN)
 		preferred_engine = link->link_enc->analog_engine;
 
 	for (i = 0; i < pool->stream_enc_count; i++) {