drm/i915/dp: Wait for FEC detected status in the sink

As required by the DP standard wait for the sink to detect the FEC
decode enabling symbol sent by the source.

There is a difference between SST and MST when the source enables
the FEC encoding: on SST this happens only after enabling the
transcoder, whereas on MST it happens already after enabling the
transcoder function (before enabling the transcoder). Wait for the
detected status at the earliest spot accordingly.

v2:
- Wait for the FEC detected status on SST after the transcoder is
  enabled.

Reviewed-by: Stanislav Lisovskiy <[email protected]>
Signed-off-by: Imre Deak <[email protected]>
Link: https://patchwork.freedesktop.org/patch/msgid/[email protected]

1 files changed, 4 insertions, 0 deletions

diff --git a/drivers/gpu/drm/i915/display/intel_dp_mst.c b/drivers/gpu/drm/i915/display/intel_dp_mst.c
index 5214cdb049b3..4d0827a3cd9b 100644
--- a/drivers/gpu/drm/i915/display/intel_dp_mst.c
+++ b/drivers/gpu/drm/i915/display/intel_dp_mst.c
@@ -878,6 +878,7 @@ static void intel_mst_enable_dp(struct intel_atomic_state *state,
 	struct drm_dp_mst_topology_state *mst_state =
 		drm_atomic_get_new_mst_topology_state(&state->base, &intel_dp->mst_mgr);
 	enum transcoder trans = pipe_config->cpu_transcoder;
+	bool first_mst_stream = intel_dp->active_mst_links == 1;
 
 	drm_WARN_ON(&dev_priv->drm, pipe_config->has_pch_encoder);
 
@@ -904,6 +905,9 @@ static void intel_mst_enable_dp(struct intel_atomic_state *state,
 
 	wait_for_act_sent(encoder, pipe_config);
 
+	if (first_mst_stream)
+		intel_ddi_wait_for_fec_status(encoder, pipe_config, true);
+
 	drm_dp_add_payload_part2(&intel_dp->mst_mgr, &state->base,
 				 drm_atomic_get_mst_payload_state(mst_state, connector->port));