drm/i915: Check for FRL training before DP Link training

This patch calls functions to check FRL training requirements
for an HDMI2.1 sink, when connected through PCON.
The call is made before the DP link training. In case FRL is not
required or failure during FRL training, the TMDS mode is selected
for the pcon.

v2: moved check_frl_training() just after FEC READY, before
starting DP link training.

v3: rebase
Signed-off-by: NAnkit Nautiyal <ankit.k.nautiyal@intel.com>
Reviewed-by: NUma Shankar <uma.shankar@intel.com>
Signed-off-by: NJani Nikula <jani.nikula@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20201218103723.30844-11-ankit.k.nautiyal@intel.com

drivers/gpu/drm/i915/display/intel_ddi.c

@@ -3651,6 +3651,8 @@ static void tgl_ddi_pre_enable_dp(struct intel_atomic_state *state,
 	 */
 	intel_dp_sink_set_fec_ready(intel_dp, crtc_state);
 
+	intel_dp_check_frl_training(intel_dp);
+
 	/*
 	 * 7.i Follow DisplayPort specification training sequence (see notes for
 	 *     failure handling)

drivers/gpu/drm/i915/display/intel_dp.c

@@ -4252,6 +4252,7 @@ static void intel_enable_dp(struct intel_atomic_state *state,
 
 	intel_dp_set_power(intel_dp, DP_SET_POWER_D0);
 	intel_dp_configure_protocol_converter(intel_dp);
+	intel_dp_check_frl_training(intel_dp);
 	intel_dp_start_link_train(intel_dp, pipe_config);
 	intel_dp_stop_link_train(intel_dp, pipe_config);
 
@@ -6173,6 +6174,7 @@ int intel_dp_retrain_link(struct intel_encoder *encoder,
 		    !intel_dp_mst_is_master_trans(crtc_state))
 			continue;
 
+		intel_dp_check_frl_training(intel_dp);
 		intel_dp_start_link_train(intel_dp, crtc_state);
 		intel_dp_stop_link_train(intel_dp, crtc_state);
 		break;