drm/i915/fec: Set FEC_READY in FEC_CONFIGURATION

If the panel supports FEC, the driver has to
set the FEC_READY bit in the dpcd register:
FEC_CONFIGURATION.

This has to happen before link training.

v2: s/intel_dp_set_fec_ready/intel_dp_sink_set_fec_ready
   - change commit message. (Gaurav)

v3: rebased. (r-b Manasi)

v4: Use fec crtc state, before setting FEC_READY
bit. (Anusha)

v5: Move to intel_ddi.c
- Make the function static (Anusha)

v6: Dont pass state as a separate argument (Ville)

v7: (From Manasi)
* Correct the debug print (Ville)

Cc: dri-devel@lists.freedesktop.org
Cc: Gaurav K Singh <gaurav.k.singh@intel.com>
Cc: Jani Nikula <jani.nikula@linux.intel.com>
Cc: Ville Syrjala <ville.syrjala@linux.intel.com>
Cc: Manasi Navare <manasi.d.navare@intel.com>
Signed-off-by: Anusha Srivatsa <anusha.srivatsa@intel.com>
Signed-off-by: Manasi Navare <manasi.d.navare@intel.com>
Reviewed-by: Manasi Navare <manasi.d.navare@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20181128202628.20238-15-manasi.d.navare@intel.com

drivers/gpu/drm/i915/intel_ddi.c

@@ -3102,6 +3102,16 @@ static void icl_program_mg_dp_mode(struct intel_digital_port *intel_dig_port)
 	I915_WRITE(MG_DP_MODE(port, 1), ln1);
 }
 
+static void intel_dp_sink_set_fec_ready(struct intel_dp *intel_dp,
+					const struct intel_crtc_state *crtc_state)
+{
+	if (!crtc_state->fec_enable)
+		return;
+
+	if (drm_dp_dpcd_writeb(&intel_dp->aux, DP_FEC_CONFIGURATION, DP_FEC_READY) <= 0)
+		DRM_DEBUG_KMS("Failed to set FEC_READY in the sink\n");
+}
+
 static void intel_ddi_pre_enable_dp(struct intel_encoder *encoder,
 				    const struct intel_crtc_state *crtc_state,
 				    const struct drm_connector_state *conn_state)
@@ -3142,6 +3152,7 @@ static void intel_ddi_pre_enable_dp(struct intel_encoder *encoder,
 		intel_dp_sink_dpms(intel_dp, DRM_MODE_DPMS_ON);
 	intel_dp_sink_set_decompression_state(intel_dp, crtc_state,
 					      true);
+	intel_dp_sink_set_fec_ready(intel_dp, crtc_state);
 	intel_dp_start_link_train(intel_dp);
 	if (port != PORT_A || INTEL_GEN(dev_priv) >= 9)
 		intel_dp_stop_link_train(intel_dp);