drm/i915/dp: Add intel_dp_mode_valid_with_dsc()

Add intel_dp_mode_valid_with_dsc() and call this for an SST/MST mode
validation to prepare for a follow-up change using a way to verify the
mode's required BW the same way this is done elsewhere during state
computation (which in turn depends on the mode's effective data rate
with the corresponding BW overhead).

Reviewed-by: Vinod Govindapillai <vinod.govindapillai@intel.com>
Signed-off-by: Imre Deak <imre.deak@intel.com>
Link: https://patch.msgid.link/20251222153547.713360-13-imre.deak@intel.com

Author: ideak

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

@@ -1580,24 +1580,20 @@ intel_dp_mode_valid(struct drm_connector *_connector,
 			dsc_slice_count =
 				drm_dp_dsc_sink_max_slice_count(connector->dp.dsc_dpcd,
 								true);
+			dsc = dsc_max_compressed_bpp && dsc_slice_count;
 		} else if (drm_dp_sink_supports_fec(connector->dp.fec_capability)) {
-			dsc_max_compressed_bpp =
-				intel_dp_dsc_get_max_compressed_bpp(display,
-								    max_link_clock,
-								    max_lanes,
-								    target_clock,
-								    mode->hdisplay,
-								    num_joined_pipes,
-								    output_format,
-								    pipe_bpp, 64);
-			dsc_slice_count =
-				intel_dp_dsc_get_slice_count(connector,
-							     target_clock,
-							     mode->hdisplay,
-							     num_joined_pipes);
-		}
+			unsigned long bw_overhead_flags = 0;
 
-		dsc = dsc_max_compressed_bpp && dsc_slice_count;
+			if (!drm_dp_is_uhbr_rate(max_link_clock))
+				bw_overhead_flags |= DRM_DP_BW_OVERHEAD_FEC;
+
+			dsc = intel_dp_mode_valid_with_dsc(connector,
+							   max_link_clock, max_lanes,
+							   target_clock, mode->hdisplay,
+							   num_joined_pipes,
+							   output_format, pipe_bpp,
+							   bw_overhead_flags);
+		}
 	}
 
 	if (intel_dp_joiner_needs_dsc(display, num_joined_pipes) && !dsc)
@@ -2705,6 +2701,35 @@ static int compute_max_compressed_bpp_x16(struct intel_connector *connector,
 	return max_link_bpp_x16;
 }
 
+bool intel_dp_mode_valid_with_dsc(struct intel_connector *connector,
+				  int link_clock, int lane_count,
+				  int mode_clock, int mode_hdisplay,
+				  int num_joined_pipes,
+				  enum intel_output_format output_format,
+				  int pipe_bpp, unsigned long bw_overhead_flags)
+{
+	struct intel_display *display = to_intel_display(connector);
+	int dsc_max_compressed_bpp;
+	int dsc_slice_count;
+
+	dsc_max_compressed_bpp =
+		intel_dp_dsc_get_max_compressed_bpp(display,
+						    link_clock,
+						    lane_count,
+						    mode_clock,
+						    mode_hdisplay,
+						    num_joined_pipes,
+						    output_format,
+						    pipe_bpp, 64);
+	dsc_slice_count =
+		intel_dp_dsc_get_slice_count(connector,
+					     mode_clock,
+					     mode_hdisplay,
+					     num_joined_pipes);
+
+	return dsc_max_compressed_bpp && dsc_slice_count;
+}
+
 /*
  * Calculate the output link min, max bpp values in limits based on the pipe bpp
  * range, crtc_state and dsc mode. Return true on success.

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

@@ -150,6 +150,13 @@ u16 intel_dp_dsc_get_max_compressed_bpp(struct intel_display *display,
 					enum intel_output_format output_format,
 					u32 pipe_bpp,
 					u32 timeslots);
+
+bool intel_dp_mode_valid_with_dsc(struct intel_connector *connector,
+				  int link_clock, int lane_count,
+				  int mode_clock, int mode_hdisplay,
+				  int num_joined_pipes,
+				  enum intel_output_format output_format,
+				  int pipe_bpp, unsigned long bw_overhead_flags);
 bool intel_dp_dsc_valid_compressed_bpp(struct intel_dp *intel_dp, int bpp_x16);
 u8 intel_dp_dsc_get_slice_count(const struct intel_connector *connector,
 				int mode_clock, int mode_hdisplay,

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

@@ -1462,8 +1462,6 @@ mst_connector_mode_valid_ctx(struct drm_connector *_connector,
 		DRM_DP_BW_OVERHEAD_MST | DRM_DP_BW_OVERHEAD_SSC_REF_CLK;
 	int ret;
 	bool dsc = false;
-	u16 dsc_max_compressed_bpp = 0;
-	u8 dsc_slice_count = 0;
 	int target_clock = mode->clock;
 	int num_joined_pipes;
 
@@ -1522,31 +1520,22 @@ mst_connector_mode_valid_ctx(struct drm_connector *_connector,
 		return 0;
 	}
 
-	if (intel_dp_has_dsc(connector)) {
+	if (intel_dp_has_dsc(connector) && drm_dp_sink_supports_fec(connector->dp.fec_capability)) {
 		/*
 		 * TBD pass the connector BPC,
 		 * for now U8_MAX so that max BPC on that platform would be picked
 		 */
 		int pipe_bpp = intel_dp_dsc_compute_max_bpp(connector, U8_MAX);
 
-		if (drm_dp_sink_supports_fec(connector->dp.fec_capability)) {
-			dsc_max_compressed_bpp =
-				intel_dp_dsc_get_max_compressed_bpp(display,
-								    max_link_clock,
-								    max_lanes,
-								    target_clock,
-								    mode->hdisplay,
-								    num_joined_pipes,
-								    INTEL_OUTPUT_FORMAT_RGB,
-								    pipe_bpp, 64);
-			dsc_slice_count =
-				intel_dp_dsc_get_slice_count(connector,
-							     target_clock,
-							     mode->hdisplay,
-							     num_joined_pipes);
-		}
+		if (!drm_dp_is_uhbr_rate(max_link_clock))
+			bw_overhead_flags |= DRM_DP_BW_OVERHEAD_FEC;
 
-		dsc = dsc_max_compressed_bpp && dsc_slice_count;
+		dsc = intel_dp_mode_valid_with_dsc(connector,
+						   max_link_clock, max_lanes,
+						   target_clock, mode->hdisplay,
+						   num_joined_pipes,
+						   INTEL_OUTPUT_FORMAT_RGB, pipe_bpp,
+						   bw_overhead_flags);
 	}
 
 	if (intel_dp_joiner_needs_dsc(display, num_joined_pipes) && !dsc) {