[PATCH v2 17/18] drm/dp: Add helpers for DFP YCbCr 4:2:0 handling

[Ville Syrjala <ville.syrjala@xxxxxxxxxxxxxxx>]

From: Ville Syrjälä <ville.syrjala@xxxxxxxxxxxxxxx>

Add helpers to determine whether the DFP supports
YCbCr 4:2:0 passthrough or YCbCr 4:4:4->4:2:0 conversion.

Signed-off-by: Ville Syrjälä <ville.syrjala@xxxxxxxxxxxxxxx>
---
 drivers/gpu/drm/drm_dp_helper.c | 44 +++++++++++++++++++++++++++++++++
 include/drm/drm_dp_helper.h     |  8 ++++++
 2 files changed, 52 insertions(+)

diff --git a/drivers/gpu/drm/drm_dp_helper.c b/drivers/gpu/drm/drm_dp_helper.c
index 0d5e9bcf11d0..dc68e10aa1fd 100644
--- a/drivers/gpu/drm/drm_dp_helper.c
+++ b/drivers/gpu/drm/drm_dp_helper.c
@@ -808,6 +808,50 @@ int drm_dp_downstream_max_bpc(const u8 dpcd[DP_RECEIVER_CAP_SIZE],
 }
 EXPORT_SYMBOL(drm_dp_downstream_max_bpc);
 
+bool drm_dp_downstream_420_passthrough(const u8 dpcd[DP_RECEIVER_CAP_SIZE],
+				       const u8 port_cap[4])
+{
+	if (!drm_dp_is_branch(dpcd))
+		return false;
+
+	if (dpcd[DP_DPCD_REV] < 0x13)
+		return false;
+
+	switch (port_cap[0] & DP_DS_PORT_TYPE_MASK) {
+	case DP_DS_PORT_TYPE_DP:
+		return true;
+	case DP_DS_PORT_TYPE_HDMI:
+		if ((dpcd[DP_DOWNSTREAMPORT_PRESENT] & DP_DETAILED_CAP_INFO_AVAILABLE) == 0)
+			return false;
+
+		return port_cap[3] & DP_DS_HDMI_YCBCR420_PASS_THROUGH;
+	default:
+		return false;
+	}
+}
+EXPORT_SYMBOL(drm_dp_downstream_420_passthrough);
+
+bool drm_dp_downstream_444_to_420_conversion(const u8 dpcd[DP_RECEIVER_CAP_SIZE],
+					     const u8 port_cap[4])
+{
+	if (!drm_dp_is_branch(dpcd))
+		return false;
+
+	if (dpcd[DP_DPCD_REV] < 0x13)
+		return false;
+
+	switch (port_cap[0] & DP_DS_PORT_TYPE_MASK) {
+	case DP_DS_PORT_TYPE_HDMI:
+		if ((dpcd[DP_DOWNSTREAMPORT_PRESENT] & DP_DETAILED_CAP_INFO_AVAILABLE) == 0)
+			return false;
+
+		return port_cap[3] & DP_DS_HDMI_YCBCR444_TO_420_CONV;
+	default:
+		return false;
+	}
+}
+EXPORT_SYMBOL(drm_dp_downstream_444_to_420_conversion);
+
 /**
  * drm_dp_downstream_mode() - return a mode for downstream facing port
  * @dpcd: DisplayPort configuration data
diff --git a/include/drm/drm_dp_helper.h b/include/drm/drm_dp_helper.h
index fbba4a0f7366..c9f2851904d0 100644
--- a/include/drm/drm_dp_helper.h
+++ b/include/drm/drm_dp_helper.h
@@ -407,6 +407,10 @@ struct drm_device;
 # define DP_DS_DVI_HIGH_COLOR_DEPTH	    (1 << 2)
 /* offset 3 for HDMI */
 # define DP_DS_HDMI_FRAME_SEQ_TO_FRAME_PACK (1 << 0)
+# define DP_DS_HDMI_YCBCR422_PASS_THROUGH   (1 << 1)
+# define DP_DS_HDMI_YCBCR420_PASS_THROUGH   (1 << 2)
+# define DP_DS_HDMI_YCBCR444_TO_422_CONV    (1 << 3)
+# define DP_DS_HDMI_YCBCR444_TO_420_CONV    (1 << 4)
 
 #define DP_MAX_DOWNSTREAM_PORTS		    0x10
 
@@ -1663,6 +1667,10 @@ int drm_dp_downstream_min_tmds_clock(const u8 dpcd[DP_RECEIVER_CAP_SIZE],
 int drm_dp_downstream_max_bpc(const u8 dpcd[DP_RECEIVER_CAP_SIZE],
 			      const u8 port_cap[4],
 			      const struct edid *edid);
+bool drm_dp_downstream_420_passthrough(const u8 dpcd[DP_RECEIVER_CAP_SIZE],
+				       const u8 port_cap[4]);
+bool drm_dp_downstream_444_to_420_conversion(const u8 dpcd[DP_RECEIVER_CAP_SIZE],
+					     const u8 port_cap[4]);
 struct drm_display_mode *drm_dp_downstream_mode(struct drm_device *dev,
 						const u8 dpcd[DP_RECEIVER_CAP_SIZE],
 						const u8 port_cap[4]);
-- 
2.26.2

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