drm/amd/display: only include FEC overhead if both asic and display support FEC

[why]
Some asics don't support FEC but FEC overhead is added into link
bandwidth calculation by mistake. This causes certain timing cannot be
validated.

[how]
Only include FEC overhead if both asic and display support FEC.
Signed-off-by: Wenjing Liu <Wenjing.Liu@amd.com>
Reviewed-by: Ashley Thomas <Ashley.Thomas2@amd.com>
Acked-by: Rodrigo Siqueira <Rodrigo.Siqueira@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>

drivers/gpu/drm/amd/display/dc/core/dc_link.c

@@ -3406,7 +3406,7 @@ uint32_t dc_link_bandwidth_kbps(
 	link_bw_kbps *= 8;   /* 8 bits per byte*/
 	link_bw_kbps *= link_setting->lane_count;
 
-	if (link->dpcd_caps.fec_cap.bits.FEC_CAPABLE) {
+	if (dc_link_is_fec_supported(link)) {
 		/* Account for FEC overhead.
 		 * We have to do it based on caps,
 		 * and not based on FEC being set ready,
@@ -3450,3 +3450,12 @@ void dc_link_overwrite_extended_receiver_cap(
 	dp_overwrite_extended_receiver_cap(link);
 }
 
+bool dc_link_is_fec_supported(const struct dc_link *link)
+{
+	return (dc_is_dp_signal(link->connector_signal) &&
+			link->link_enc->features.fec_supported &&
+			link->dpcd_caps.fec_cap.bits.FEC_CAPABLE &&
+			!link->dc->debug.disable_fec &&
+			!IS_FPGA_MAXIMUS_DC(link->ctx->dce_environment));
+}
+

drivers/gpu/drm/amd/display/dc/core/dc_link_dp.c

@@ -4126,8 +4126,7 @@ void dp_set_fec_ready(struct dc_link *link, bool ready)
 	struct link_encoder *link_enc = link->link_enc;
 	uint8_t fec_config = 0;
 
-	if (link->dc->debug.disable_fec ||
-			IS_FPGA_MAXIMUS_DC(link->ctx->dce_environment))
+	if (!dc_link_is_fec_supported(link))
 		return;
 
 	if (link_enc->funcs->fec_set_ready &&
@@ -4162,8 +4161,7 @@ void dp_set_fec_enable(struct dc_link *link, bool enable)
 {
 	struct link_encoder *link_enc = link->link_enc;
 
-	if (link->dc->debug.disable_fec ||
-			IS_FPGA_MAXIMUS_DC(link->ctx->dce_environment))
+	if (!dc_link_is_fec_supported(link))
 		return;
 
 	if (link_enc->funcs->fec_set_enable &&

drivers/gpu/drm/amd/display/dc/dc_link.h

@@ -333,4 +333,7 @@ bool dc_submit_i2c_oem(
 
 uint32_t dc_bandwidth_in_kbps_from_timing(
 	const struct dc_crtc_timing *timing);
+
+bool dc_link_is_fec_supported(const struct dc_link *link);
+
 #endif /* DC_LINK_H_ */

drivers/gpu/drm/amd/display/dc/dcn20/dcn20_resource.c

@@ -1143,6 +1143,7 @@ static const struct encoder_feature_support link_enc_feature = {
 		.max_hdmi_pixel_clock = 600000,
 		.hdmi_ycbcr420_supported = true,
 		.dp_ycbcr420_supported = true,
+		.fec_supported = true,
 		.flags.bits.IS_HBR2_CAPABLE = true,
 		.flags.bits.IS_HBR3_CAPABLE = true,
 		.flags.bits.IS_TPS3_CAPABLE = true,

drivers/gpu/drm/amd/display/dc/dcn21/dcn21_resource.c

@@ -1589,6 +1589,7 @@ static const struct encoder_feature_support link_enc_feature = {
 		.max_hdmi_pixel_clock = 600000,
 		.hdmi_ycbcr420_supported = true,
 		.dp_ycbcr420_supported = true,
+		.fec_supported = true,
 		.flags.bits.IS_HBR2_CAPABLE = true,
 		.flags.bits.IS_HBR3_CAPABLE = true,
 		.flags.bits.IS_TPS3_CAPABLE = true,

drivers/gpu/drm/amd/display/dc/inc/hw/link_encoder.h

@@ -68,6 +68,7 @@ struct encoder_feature_support {
 	unsigned int max_hdmi_pixel_clock;
 	bool hdmi_ycbcr420_supported;
 	bool dp_ycbcr420_supported;
+	bool fec_supported;
 };
 
 union dpcd_psr_configuration {