[PATCH 03/14] drm/i915/dp: Add Scaler constraint for YCbCr420 output

[Ankit Nautiyal]

For YCbCr420 output, scaler is required for downsampling.
Scaler can be used only when source size smaller than 4096x5120.
So go for native YCbCr420 only if there are no scaler constraints.

Signed-off-by: Ankit Nautiyal <ankit.k.nautiyal at intel.com>
---
 drivers/gpu/drm/i915/display/intel_dp.c | 23 +++++++++++++++++++----
 1 file changed, 19 insertions(+), 4 deletions(-)

diff --git a/drivers/gpu/drm/i915/display/intel_dp.c b/drivers/gpu/drm/i915/display/intel_dp.c
index 56b5a4bfd925..7197b74e878c 100644
--- a/drivers/gpu/drm/i915/display/intel_dp.c
+++ b/drivers/gpu/drm/i915/display/intel_dp.c
@@ -786,8 +786,15 @@ static u8 intel_dp_dsc_get_slice_count(struct intel_dp *intel_dp,
 	return 0;
 }
 
+static bool
+ycbcr420_scaler_constraints(const struct drm_display_mode *mode)
+{
+	return mode->hdisplay > 4096 || mode->vdisplay > 5120;
+}
+
 static enum intel_output_format
 intel_dp_output_format(struct intel_connector *connector,
+		       const struct drm_display_mode *mode,
 		       enum intel_output_format sink_format)
 {
 	struct intel_dp *intel_dp = intel_attached_dp(connector);
@@ -802,8 +809,15 @@ intel_dp_output_format(struct intel_connector *connector,
 
 	if (intel_dp->dfp.ycbcr_444_to_420)
 		return INTEL_OUTPUT_FORMAT_YCBCR444;
-	else
+
+	/*
+	 * For YCbCr420 output, scaler is required for downsampling
+	 * So go for native YCbCr420 only if there are no scaler constraints.
+	 */
+	if (!ycbcr420_scaler_constraints(mode))
 		return INTEL_OUTPUT_FORMAT_YCBCR420;
+
+	return INTEL_OUTPUT_FORMAT_RGB;
 }
 
 int intel_dp_min_bpp(enum intel_output_format output_format)
@@ -839,7 +853,7 @@ intel_dp_mode_min_output_bpp(struct intel_connector *connector,
 	else
 		sink_format = INTEL_OUTPUT_FORMAT_RGB;
 
-	output_format = intel_dp_output_format(connector, sink_format);
+	output_format = intel_dp_output_format(connector, mode, sink_format);
 
 	return intel_dp_output_bpp(output_format, intel_dp_min_bpp(output_format));
 }
@@ -2002,7 +2016,8 @@ intel_dp_compute_output_format(struct intel_encoder *encoder,
 		crtc_state->sink_format = INTEL_OUTPUT_FORMAT_RGB;
 	}
 
-	crtc_state->output_format = intel_dp_output_format(connector, crtc_state->sink_format);
+	crtc_state->output_format = intel_dp_output_format(connector, adjusted_mode,
+							   crtc_state->sink_format);
 
 	ret = intel_dp_compute_link_config(encoder, crtc_state, conn_state,
 					   respect_downstream_limits);
@@ -2012,7 +2027,7 @@ intel_dp_compute_output_format(struct intel_encoder *encoder,
 			return ret;
 
 		crtc_state->sink_format = INTEL_OUTPUT_FORMAT_YCBCR420;
-		crtc_state->output_format = intel_dp_output_format(connector,
+		crtc_state->output_format = intel_dp_output_format(connector, adjusted_mode,
 								   crtc_state->sink_format);
 		ret = intel_dp_compute_link_config(encoder, crtc_state, conn_state,
 						   respect_downstream_limits);
-- 
2.25.1