drm/i915/hdmi: Introduce intel_hdmi_is_ycbr420()

Introduce a small helper which given the crtc state tells us
whether we're output YCbCr 4:2:0 or not. For native HDMI this
is rather simple as we just look at the output_format. But I
think the helper is beneficial since with DP HDMI DFPs we're
going to need a more complex variant, and I want to unify the
DP and HDMI sides of that as much as possible.
Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20211015133921.4609-3-ville.syrjala@linux.intel.comReviewed-by: Jani Nikula <jani.nikula@intel.com>

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

@@ -1799,6 +1799,11 @@ static bool intel_has_hdmi_sink(struct intel_hdmi *hdmi,
 		READ_ONCE(to_intel_digital_connector_state(conn_state)->force_audio) != HDMI_AUDIO_OFF_DVI;
 }
 
+static bool intel_hdmi_is_ycbcr420(const struct intel_crtc_state *crtc_state)
+{
+	return crtc_state->output_format == INTEL_OUTPUT_FORMAT_YCBCR420;
+}
+
 static int hdmi_port_clock_limit(struct intel_hdmi *hdmi,
 				 bool respect_downstream_limits,
 				 bool has_hdmi_sink)
@@ -2036,7 +2041,7 @@ static bool hdmi_deep_color_possible(const struct intel_crtc_state *crtc_state,
 		return false;
 
 	/* Display Wa_1405510057:icl,ehl */
-	if (crtc_state->output_format == INTEL_OUTPUT_FORMAT_YCBCR420 &&
+	if (intel_hdmi_is_ycbcr420(crtc_state) &&
 	    bpc == 10 && DISPLAY_VER(dev_priv) == 11 &&
 	    (adjusted_mode->crtc_hblank_end -
 	     adjusted_mode->crtc_hblank_start) % 8 == 2)
@@ -2044,8 +2049,7 @@ static bool hdmi_deep_color_possible(const struct intel_crtc_state *crtc_state,
 
 	return intel_hdmi_deep_color_possible(crtc_state, bpc,
 					      crtc_state->has_hdmi_sink,
-					      crtc_state->output_format ==
-					      INTEL_OUTPUT_FORMAT_YCBCR420);
+					      intel_hdmi_is_ycbcr420(crtc_state));
 }
 
 static int intel_hdmi_compute_bpc(struct intel_encoder *encoder,
@@ -2079,7 +2083,7 @@ static int intel_hdmi_compute_clock(struct intel_encoder *encoder,
 		clock *= 2;
 
 	/* YCBCR420 TMDS rate requirement is half the pixel clock */
-	if (crtc_state->output_format == INTEL_OUTPUT_FORMAT_YCBCR420)
+	if (intel_hdmi_is_ycbcr420(crtc_state))
 		clock /= 2;
 
 	bpc = intel_hdmi_compute_bpc(encoder, crtc_state, clock);
@@ -2176,7 +2180,7 @@ static int intel_hdmi_compute_output_format(struct intel_encoder *encoder,
 
 	ret = intel_hdmi_compute_clock(encoder, crtc_state);
 	if (ret) {
-		if (crtc_state->output_format != INTEL_OUTPUT_FORMAT_YCBCR420 &&
+		if (!intel_hdmi_is_ycbcr420(crtc_state) &&
 		    connector->ycbcr_420_allowed &&
 		    drm_mode_is_420_also(&connector->display_info, adjusted_mode)) {
 			crtc_state->output_format = INTEL_OUTPUT_FORMAT_YCBCR420;
@@ -2221,7 +2225,7 @@ int intel_hdmi_compute_config(struct intel_encoder *encoder,
 	if (ret)
 		return ret;
 
-	if (pipe_config->output_format == INTEL_OUTPUT_FORMAT_YCBCR420) {
+	if (intel_hdmi_is_ycbcr420(pipe_config)) {
 		ret = intel_panel_fitting(pipe_config, conn_state);
 		if (ret)
 			return ret;