[Intel-gfx] [RFC v4 1/6] 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.

v2:
  Addressed review comments from Ville.
  Style fixed with few naming.
  %s/config/crtc_state/
  %s/intel_crtc/crtc/
  If lscon is active, it makes not to call intel_dp_ycbcr420_config()
  to avoid to clobber of lspcon_ycbcr420_config() routine.
  And it move the 420_only check into the intel_dp_ycbcr420_config().

v3: Fix uninitialized return value and it is reported by Dan Carpenter.

Signed-off-by: Gwan-gyeong Mun <gwan-gyeong.mun at intel.com>
Reviewed-by: Maarten Lankhorst <maarten.lankhorst at linux.intel.com>
---
 drivers/gpu/drm/i915/intel_dp.c | 39 ++++++++++++++++++++++++++++++++-
 1 file changed, 38 insertions(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/i915/intel_dp.c b/drivers/gpu/drm/i915/intel_dp.c
index e1a051c0fbfe..882afba6e0f1 100644
--- a/drivers/gpu/drm/i915/intel_dp.c
+++ b/drivers/gpu/drm/i915/intel_dp.c
@@ -2104,6 +2104,38 @@ intel_dp_compute_link_config(struct intel_encoder *encoder,
 	return 0;
 }
 
+static int
+intel_dp_ycbcr420_config(struct drm_connector *connector,
+			 struct intel_crtc_state *crtc_state)
+{
+	const struct drm_display_info *info = &connector->display_info;
+	const struct drm_display_mode *adjusted_mode =
+		&crtc_state->base.adjusted_mode;
+	struct intel_crtc *crtc = to_intel_crtc(crtc_state->base.crtc);
+	int ret;
+
+	if (drm_mode_is_420_only(info, adjusted_mode) &&
+	    connector->ycbcr_420_allowed) {
+		crtc_state->output_format = INTEL_OUTPUT_FORMAT_YCBCR420;
+
+		/* YCBCR 420 output conversion needs a scaler */
+		ret = skl_update_scaler_crtc(crtc_state);
+		if (ret) {
+			DRM_DEBUG_KMS("Scaler allocation for output failed\n");
+			goto err;
+		}
+
+		intel_pch_panel_fitting(crtc, crtc_state,
+					DRM_MODE_SCALE_FULLSCREEN);
+	}
+
+	return 0;
+
+err:
+	DRM_ERROR("Can't support YCBCR420 output\n");
+	return ret;
+}
+
 int
 intel_dp_compute_config(struct intel_encoder *encoder,
 			struct intel_crtc_state *pipe_config,
@@ -2120,7 +2152,7 @@ intel_dp_compute_config(struct intel_encoder *encoder,
 		to_intel_digital_connector_state(conn_state);
 	bool constant_n = drm_dp_has_quirk(&intel_dp->desc,
 					   DP_DPCD_QUIRK_CONSTANT_N);
-	int ret;
+	int ret = 0;
 
 	if (HAS_PCH_SPLIT(dev_priv) && !HAS_DDI(dev_priv) && port != PORT_A)
 		pipe_config->has_pch_encoder = true;
@@ -2128,6 +2160,11 @@ intel_dp_compute_config(struct intel_encoder *encoder,
 	pipe_config->output_format = INTEL_OUTPUT_FORMAT_RGB;
 	if (lspcon->active)
 		lspcon_ycbcr420_config(&intel_connector->base, pipe_config);
+	else
+		ret = intel_dp_ycbcr420_config(&intel_connector->base, pipe_config);
+
+	if (ret)
+		return ret;
 
 	pipe_config->has_drrs = false;
 	if (IS_G4X(dev_priv) || port == PORT_A)
-- 
2.21.0