drm/i915: Only enable DFP 4:4:4->4:2:0 conversion when outputting YCbCr 4:4:4

Let's not enable the 4:4:4->4:2:0 conversion bit in the DFP unless we're
actually outputting YCbCr 4:4:4. It would appear some protocol
converters blindy consult this bit even when the source is outputting
RGB, resulting in a visual mess.

Cc: stable@vger.kernel.org
Closes: https://gitlab.freedesktop.org/drm/intel/-/issues/2914Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20210111164111.13302-1-ville.syrjala@linux.intel.com
Fixes: 181567aa ("drm/i915: Do YCbCr 444->420 conversion via DP protocol converters")
Reviewed-by: Jani Nikula <jani.nikula@intel.com>
(cherry picked from commit 3170a21f)
Signed-off-by: Jani Nikula <jani.nikula@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20210118154355.24453-1-ville.syrjala@linux.intel.com

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

@@ -3725,7 +3725,7 @@ static void hsw_ddi_pre_enable_dp(struct intel_atomic_state *state,
 	intel_ddi_init_dp_buf_reg(encoder, crtc_state);
 	if (!is_mst)
 		intel_dp_set_power(intel_dp, DP_SET_POWER_D0);
-	intel_dp_configure_protocol_converter(intel_dp);
+	intel_dp_configure_protocol_converter(intel_dp, crtc_state);
 	intel_dp_sink_set_decompression_state(intel_dp, crtc_state,
 					      true);
 	intel_dp_sink_set_fec_ready(intel_dp, crtc_state);

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

@@ -4014,7 +4014,8 @@ static void intel_dp_enable_port(struct intel_dp *intel_dp,
 	intel_de_posting_read(dev_priv, intel_dp->output_reg);
 }
 
-void intel_dp_configure_protocol_converter(struct intel_dp *intel_dp)
+void intel_dp_configure_protocol_converter(struct intel_dp *intel_dp,
+					   const struct intel_crtc_state *crtc_state)
 {
 	struct drm_i915_private *i915 = dp_to_i915(intel_dp);
 	u8 tmp;
@@ -4033,8 +4034,8 @@ void intel_dp_configure_protocol_converter(struct intel_dp *intel_dp)
 		drm_dbg_kms(&i915->drm, "Failed to set protocol converter HDMI mode to %s\n",
 			    enableddisabled(intel_dp->has_hdmi_sink));
 
-	tmp = intel_dp->dfp.ycbcr_444_to_420 ?
-		DP_CONVERSION_TO_YCBCR420_ENABLE : 0;
+	tmp = crtc_state->output_format == INTEL_OUTPUT_FORMAT_YCBCR444 &&
+		intel_dp->dfp.ycbcr_444_to_420 ? DP_CONVERSION_TO_YCBCR420_ENABLE : 0;
 
 	if (drm_dp_dpcd_writeb(&intel_dp->aux,
 			       DP_PROTOCOL_CONVERTER_CONTROL_1, tmp) != 1)
@@ -4088,7 +4089,7 @@ static void intel_enable_dp(struct intel_atomic_state *state,
 	}
 
 	intel_dp_set_power(intel_dp, DP_SET_POWER_D0);
-	intel_dp_configure_protocol_converter(intel_dp);
+	intel_dp_configure_protocol_converter(intel_dp, pipe_config);
 	intel_dp_start_link_train(intel_dp, pipe_config);
 	intel_dp_stop_link_train(intel_dp, pipe_config);
 

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

@@ -51,7 +51,8 @@ int intel_dp_get_link_train_fallback_values(struct intel_dp *intel_dp,
 int intel_dp_retrain_link(struct intel_encoder *encoder,
 			  struct drm_modeset_acquire_ctx *ctx);
 void intel_dp_set_power(struct intel_dp *intel_dp, u8 mode);
-void intel_dp_configure_protocol_converter(struct intel_dp *intel_dp);
+void intel_dp_configure_protocol_converter(struct intel_dp *intel_dp,
+					   const struct intel_crtc_state *crtc_state);
 void intel_dp_sink_set_decompression_state(struct intel_dp *intel_dp,
 					   const struct intel_crtc_state *crtc_state,
 					   bool enable);