[Intel-gfx] [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 max_src_w and
max_src_h as defined by for the platform.
So go for native YCbCr420 only if there are no scaler constraints.

v2: Corrected max-width based on Display Version.

v3: Updated max-width as per latest Bspec change.

Signed-off-by: Ankit Nautiyal <ankit.k.nautiyal at intel.com>
---
 drivers/gpu/drm/i915/display/intel_dp.c | 41 ++++++++++++++++++++++---
 1 file changed, 37 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..bbfb6559feef 100644
--- a/drivers/gpu/drm/i915/display/intel_dp.c
+++ b/drivers/gpu/drm/i915/display/intel_dp.c
@@ -804,11 +804,36 @@ 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)
+{
+	int max_src_w, max_src_h;
+
+	if (DISPLAY_VER(i915) < 11) {
+		max_src_w = 4096;
+		max_src_h = 4096;
+	} else if (DISPLAY_VER(i915) < 12) {
+		max_src_w = 5120;
+		max_src_h = 4096;
+	} else if (DISPLAY_VER(i915) < 14) {
+		max_src_w = 5120;
+		max_src_h = 8192;
+	} else {
+		max_src_w = 4096;
+		max_src_h = 8192;
+	}
+
+	return mode->hdisplay > max_src_w || mode->vdisplay > max_src_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 +845,15 @@ 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 +889,7 @@ 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 +2073,8 @@ 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 +2084,7 @@ 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