drm/i915/dp: Restructure the sink/output format selection

Restructure intel_dp_compute_output_format() to resemble the new
intel_hdmi_compute_output_formats().

Again, we basically have two main code paths:
- YCbCr 4:2:0 only modes
- everything else including YCbCr 4:2:0 also modes

Take the exact same approach with the DP code, making the
format selection much less convoluted.

Cc: Nicolas Frattaroli <nicolas.frattaroli@collabora.com>
Cc: Ankit Nautiyal <ankit.k.nautiyal@intel.com>
Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Link: https://patch.msgid.link/20260409101539.22032-5-ville.syrjala@linux.intel.com
Reviewed-by: Ankit Nautiyal <ankit.k.nautiyal@intel.com>
Tested-by: Nicolas Frattaroli <nicolas.frattaroli@collabora.com>

1 files changed, 66 insertions, 26 deletions

diff --git a/drivers/gpu/drm/i915/display/intel_dp.c b/drivers/gpu/drm/i915/display/intel_dp.c
index b8b6d62fb275..ed5841f224ee 100644
--- a/drivers/gpu/drm/i915/display/intel_dp.c
+++ b/drivers/gpu/drm/i915/display/intel_dp.c
@@ -1379,6 +1379,28 @@ intel_dp_mode_valid_downstream(struct intel_connector *connector,
 	return MODE_OK;
 }
 
+static enum drm_mode_status
+intel_dp_sink_format_valid(struct intel_connector *connector,
+			   const struct drm_display_mode *mode,
+			   enum intel_output_format sink_format)
+{
+	const struct drm_display_info *info = &connector->base.display_info;
+
+	switch (sink_format) {
+	case INTEL_OUTPUT_FORMAT_YCBCR420:
+		if (!connector->base.ycbcr_420_allowed ||
+		    !drm_mode_is_420(info, mode))
+			return MODE_NO_420;
+
+		return MODE_OK;
+	case INTEL_OUTPUT_FORMAT_RGB:
+		return MODE_OK;
+	default:
+		MISSING_CASE(sink_format);
+		return MODE_BAD;
+	}
+}
+
 int intel_dp_max_hdisplay_per_pipe(struct intel_display *display)
 {
 	return DISPLAY_VER(display) >= 30 ? 6144 : 5120;
@@ -3338,41 +3360,59 @@ static int
 intel_dp_compute_output_format(struct intel_encoder *encoder,
 			       struct intel_crtc_state *crtc_state,
 			       struct drm_connector_state *conn_state,
-			       bool respect_downstream_limits)
+			       bool respect_downstream_limits,
+			       enum intel_output_format sink_format)
+{
+	struct intel_dp *intel_dp = enc_to_intel_dp(encoder);
+	struct intel_connector *connector = intel_dp->attached_connector;
+	const struct drm_display_mode *adjusted_mode = &crtc_state->hw.adjusted_mode;
+
+	if (intel_dp_sink_format_valid(connector, adjusted_mode,
+				       sink_format) != MODE_OK)
+		return -EINVAL;
+
+	crtc_state->sink_format = sink_format;
+	crtc_state->output_format = intel_dp_output_format(connector, crtc_state->sink_format);
+
+	return intel_dp_compute_link_config(encoder, crtc_state, conn_state,
+					    respect_downstream_limits);
+}
+
+static int
+intel_dp_compute_formats(struct intel_encoder *encoder,
+			 struct intel_crtc_state *crtc_state,
+			 struct drm_connector_state *conn_state,
+			 bool respect_downstream_limits)
 {
 	struct intel_display *display = to_intel_display(encoder);
 	struct intel_dp *intel_dp = enc_to_intel_dp(encoder);
 	struct intel_connector *connector = intel_dp->attached_connector;
 	const struct drm_display_info *info = &connector->base.display_info;
 	const struct drm_display_mode *adjusted_mode = &crtc_state->hw.adjusted_mode;
-	bool ycbcr_420_only;
 	int ret;
 
-	ycbcr_420_only = drm_mode_is_420_only(info, adjusted_mode);
-
-	if (ycbcr_420_only && !connector->base.ycbcr_420_allowed) {
-		drm_dbg_kms(display->drm,
-			    "YCbCr 4:2:0 mode but YCbCr 4:2:0 output not possible. Falling back to RGB.\n");
-		crtc_state->sink_format = INTEL_OUTPUT_FORMAT_RGB;
-	} else {
-		crtc_state->sink_format = intel_dp_sink_format(connector, adjusted_mode);
-	}
+	if (drm_mode_is_420_only(info, adjusted_mode)) {
+		ret = intel_dp_compute_output_format(encoder, crtc_state, conn_state,
+						     respect_downstream_limits,
+						     INTEL_OUTPUT_FORMAT_YCBCR420);
 
-	crtc_state->output_format = intel_dp_output_format(connector, crtc_state->sink_format);
+		if (ret) {
+			drm_dbg_kms(display->drm,
+				    "YCbCr 4:2:0 mode but YCbCr 4:2:0 output not possible. Falling back to RGB.\n");
 
-	ret = intel_dp_compute_link_config(encoder, crtc_state, conn_state,
-					   respect_downstream_limits);
-	if (ret) {
-		if (crtc_state->sink_format == INTEL_OUTPUT_FORMAT_YCBCR420 ||
-		    !connector->base.ycbcr_420_allowed ||
-		    !drm_mode_is_420_also(info, adjusted_mode))
-			return ret;
+			ret = intel_dp_compute_output_format(encoder, crtc_state, conn_state,
+							     respect_downstream_limits,
+							     INTEL_OUTPUT_FORMAT_RGB);
+		}
+	} else {
+		ret = intel_dp_compute_output_format(encoder, crtc_state, conn_state,
+						     respect_downstream_limits,
+						     INTEL_OUTPUT_FORMAT_RGB);
 
-		crtc_state->sink_format = INTEL_OUTPUT_FORMAT_YCBCR420;
-		crtc_state->output_format = intel_dp_output_format(connector,
-								   crtc_state->sink_format);
-		ret = intel_dp_compute_link_config(encoder, crtc_state, conn_state,
-						   respect_downstream_limits);
+		if (ret && drm_mode_is_420_also(info, adjusted_mode))
+			ret = intel_dp_compute_output_format(encoder, crtc_state, conn_state,
+							     respect_downstream_limits,
+							     INTEL_OUTPUT_FORMAT_YCBCR420);
 	}
 
 	return ret;
@@ -3547,9 +3587,9 @@ intel_dp_compute_config(struct intel_encoder *encoder,
 	 * Try to respect downstream TMDS clock limits first, if
 	 * that fails assume the user might know something we don't.
 	 */
-	ret = intel_dp_compute_output_format(encoder, pipe_config, conn_state, true);
+	ret = intel_dp_compute_formats(encoder, pipe_config, conn_state, true);
 	if (ret)
-		ret = intel_dp_compute_output_format(encoder, pipe_config, conn_state, false);
+		ret = intel_dp_compute_formats(encoder, pipe_config, conn_state, false);
 	if (ret)
 		return ret;