drm/amd/display: Disable error correction if it's not supported

[Why]
Error correction was enabled in a monitor which doesn't support.

[How]
Disable error correction if it's not supported
Reviewed-by: Wenjing Liu <wenjing.liu@amd.com>
Acked-by: Aurabindo Pillai <aurabindo.pillai@amd.com>
Signed-off-by: Cruise <cruise.hung@amd.com>
Tested-by: Daniel Wheeler <daniel.wheeler@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>

drivers/gpu/drm/amd/display/dc/link/protocols/link_dp_phy.c

@@ -147,32 +147,27 @@ enum dc_status dp_set_fec_ready(struct dc_link *link, const struct link_resource
 
 	link_enc = link_enc_cfg_get_link_enc(link);
 	ASSERT(link_enc);
+	if (link_enc->funcs->fec_set_ready == NULL)
+		return DC_NOT_SUPPORTED;
 
-	if (!dp_should_enable_fec(link))
-		return status;
-
-	if (link_enc->funcs->fec_set_ready &&
-			link->dpcd_caps.fec_cap.bits.FEC_CAPABLE) {
-		if (ready) {
+	if (ready && dp_should_enable_fec(link)) {
+		if (link->fec_state == dc_link_fec_not_ready) {
 			fec_config = 1;
-			status = core_link_write_dpcd(link,
-					DP_FEC_CONFIGURATION,
-					&fec_config,
-					sizeof(fec_config));
+
+			status = core_link_write_dpcd(link, DP_FEC_CONFIGURATION,
+					&fec_config, sizeof(fec_config));
+
 			if (status == DC_OK) {
 				link_enc->funcs->fec_set_ready(link_enc, true);
 				link->fec_state = dc_link_fec_ready;
-			} else {
-				link_enc->funcs->fec_set_ready(link_enc, false);
-				link->fec_state = dc_link_fec_not_ready;
-				dm_error("dpcd write failed to set fec_ready");
 			}
-		} else if (link->fec_state == dc_link_fec_ready) {
+		}
+	} else {
+		if (link->fec_state == dc_link_fec_ready) {
 			fec_config = 0;
-			status = core_link_write_dpcd(link,
-					DP_FEC_CONFIGURATION,
-					&fec_config,
-					sizeof(fec_config));
+			core_link_write_dpcd(link, DP_FEC_CONFIGURATION,
+				&fec_config, sizeof(fec_config));
+
 			link_enc->funcs->fec_set_ready(link_enc, false);
 			link->fec_state = dc_link_fec_not_ready;
 		}
@@ -187,14 +182,12 @@ void dp_set_fec_enable(struct dc_link *link, bool enable)
 
 	link_enc = link_enc_cfg_get_link_enc(link);
 	ASSERT(link_enc);
-
-	if (!dp_should_enable_fec(link))
+	if (link_enc->funcs->fec_set_enable == NULL)
 		return;
 
-	if (link_enc->funcs->fec_set_enable &&
-			link->dpcd_caps.fec_cap.bits.FEC_CAPABLE) {
-		if (link->fec_state == dc_link_fec_ready && enable) {
-			/* Accord to DP spec, FEC enable sequence can first
+	if (enable && dp_should_enable_fec(link)) {
+		if (link->fec_state == dc_link_fec_ready) {
+			/* According to DP spec, FEC enable sequence can first
 			 * be transmitted anytime after 1000 LL codes have
 			 * been transmitted on the link after link training
 			 * completion. Using 1 lane RBR should have the maximum
@@ -204,7 +197,9 @@ void dp_set_fec_enable(struct dc_link *link, bool enable)
 			udelay(7);
 			link_enc->funcs->fec_set_enable(link_enc, true);
 			link->fec_state = dc_link_fec_enabled;
-		} else if (link->fec_state == dc_link_fec_enabled && !enable) {
+		}
+	} else {
+		if (link->fec_state == dc_link_fec_enabled) {
 			link_enc->funcs->fec_set_enable(link_enc, false);
 			link->fec_state = dc_link_fec_ready;
 		}