[Intel-gfx] [RFC 2/6] drm/i915/dp: Add a config function for YCBCR420 outputs

[Gwan-gyeong Mun]

This patch checks a support of YCBCR420 outputs on an encoder level.
If the input mode is YCBCR420-only mode then it prepares DP as an YCBCR420
output, else it continues with RGB output mode.
It set output_format to INTEL_OUTPUT_FORMAT_YCBCR420 in order to using
a pipe scaler as RGB to YCbCr 4:4:4.

Signed-off-by: Gwan-gyeong Mun <gwan-gyeong.mun at intel.com>
---
 drivers/gpu/drm/i915/intel_dp.c | 33 +++++++++++++++++++++++++++++++++
 1 file changed, 33 insertions(+)

diff --git a/drivers/gpu/drm/i915/intel_dp.c b/drivers/gpu/drm/i915/intel_dp.c
index ad7382d3be86..a61aff23c8b2 100644
--- a/drivers/gpu/drm/i915/intel_dp.c
+++ b/drivers/gpu/drm/i915/intel_dp.c
@@ -2098,6 +2098,31 @@ intel_dp_compute_link_config(struct intel_encoder *encoder,
 	return 0;
 }
 
+static bool
+intel_dp_ycbcr420_config(struct drm_connector *connector,
+			 struct intel_crtc_state *config)
+{
+	struct intel_crtc *intel_crtc = to_intel_crtc(config->base.crtc);
+
+	if (!connector->ycbcr_420_allowed) {
+		DRM_ERROR("Platform doesn't support YCBCR420 output\n");
+		return false;
+	}
+
+	config->output_format = INTEL_OUTPUT_FORMAT_YCBCR420;
+
+	/* YCBCR 420 output conversion needs a scaler */
+	if (skl_update_scaler_crtc(config)) {
+		DRM_DEBUG_KMS("Scaler allocation for output failed\n");
+		return false;
+	}
+
+	intel_pch_panel_fitting(intel_crtc, config,
+				DRM_MODE_SCALE_FULLSCREEN);
+
+	return true;
+}
+
 int
 intel_dp_compute_config(struct intel_encoder *encoder,
 			struct intel_crtc_state *pipe_config,
@@ -2115,6 +2140,7 @@ intel_dp_compute_config(struct intel_encoder *encoder,
 	bool constant_n = drm_dp_has_quirk(&intel_dp->desc,
 					   DP_DPCD_QUIRK_CONSTANT_N);
 	int ret;
+	struct drm_connector *connector = conn_state->connector;
 
 	if (HAS_PCH_SPLIT(dev_priv) && !HAS_DDI(dev_priv) && port != PORT_A)
 		pipe_config->has_pch_encoder = true;
@@ -2123,6 +2149,13 @@ intel_dp_compute_config(struct intel_encoder *encoder,
 	if (lspcon->active)
 		lspcon_ycbcr420_config(&intel_connector->base, pipe_config);
 
+	if (drm_mode_is_420_only(&connector->display_info, adjusted_mode)) {
+		if (!intel_dp_ycbcr420_config(connector, pipe_config)) {
+			DRM_ERROR("Can't support YCBCR420 output\n");
+			return false;
+		}
+	}
+
 	pipe_config->has_drrs = false;
 	if (IS_G4X(dev_priv) || port == PORT_A)
 		pipe_config->has_audio = false;
-- 
2.20.1