[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 5120x4096.
So go for native YCbCr420 only if there are no scaler constraints.

v2: Corrected max-width based on Display Version.

Signed-off-by: Ankit Nautiyal <ankit.k.nautiyal at intel.com>
---
 drivers/gpu/drm/i915/display/intel_dp.c | 32 +++++++++++++++++++++----
 1 file changed, 28 insertions(+), 4 deletions(-)

diff --git a/drivers/gpu/drm/i915/display/intel_dp.c b/drivers/gpu/drm/i915/display/intel_dp.c
index 1dae71d7055a..be0bb368477b 100644
--- a/drivers/gpu/drm/i915/display/intel_dp.c
+++ b/drivers/gpu/drm/i915/display/intel_dp.c
@@ -804,11 +804,27 @@ u8 intel_dp_dsc_get_slice_count(struct intel_dp *intel_dp,
 	return 0;
 }
 
+static bool
+ycbcr420_scaler_constraints(struct drm_i915_private *i915,
+			    const struct drm_display_mode *mode)
+{
+	/* FIXME: Use macros for max_w and max_h from intel_scaler */
+	int max_w = 4096;
+	int max_h = 4096;
+
+	if (DISPLAY_VER(i915) > 11)
+		max_w = 5120;
+
+	return mode->hdisplay > max_w || mode->vdisplay > max_h;
+}
+
 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);
+	struct drm_i915_private *i915 = to_i915(connector->base.dev);
 
 	if (!connector->base.ycbcr_420_allowed ||
 	    sink_format != INTEL_OUTPUT_FORMAT_YCBCR420)
@@ -820,8 +836,15 @@ 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(i915, mode))
 		return INTEL_OUTPUT_FORMAT_YCBCR420;
+
+	return INTEL_OUTPUT_FORMAT_RGB;
 }
 
 int intel_dp_min_bpp(enum intel_output_format output_format)
@@ -857,7 +880,7 @@ 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));
 }
@@ -2041,7 +2064,8 @@ 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);
@@ -2051,7 +2075,7 @@ 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