[PATCH 04/11] drm: parse ycbcr420 vcb block

[Shashank Sharma <shashank.sharma@intel.com>]

HDMI 2.0 spec adds support for ycbcr420 subsampled output.
CEA-861-F adds two new blocks in EDID, to provide information about
sink's support for ycbcr420 output.

One of these new blocks is: ycbcr420 vcb
- ycbcr420 video capability data (vcb) block: video modes which can be
  support in ycbcr420 output mode also (along with RGB, YCBCR 444/422 etc)

This patch adds parsing and handling of ycbcr420-vcb in the DRM layer.
This block contains a bitmap about which mode, from among the list of
normal svd videomodes, can support ycbcr420 output too.

So if bit 0 from first vcb byte is set, means first video mode in the
svd list, can be supported in ycbcr420 output too. Bit 2 means second
video mode from svd list, and so on.

Cc: Ville Syrjala <ville.syrjala@linux.intel.com>
Cc: Jose Abreu <joabreu@synopsys.com>
Signed-off-by: Shashank Sharma <shashank.sharma@intel.com>
---
 drivers/gpu/drm/drm_edid.c  | 80 +++++++++++++++++++++++++++++++++++++++++++--
 include/drm/drm_connector.h |  1 +
 2 files changed, 79 insertions(+), 2 deletions(-)

diff --git a/drivers/gpu/drm/drm_edid.c b/drivers/gpu/drm/drm_edid.c
index 64d8e2e..d01b7df 100644
--- a/drivers/gpu/drm/drm_edid.c
+++ b/drivers/gpu/drm/drm_edid.c
@@ -2778,6 +2778,7 @@ add_detailed_modes(struct drm_connector *connector, struct edid *edid,
 #define SPEAKER_BLOCK	0x04
 #define VIDEO_CAPABILITY_BLOCK	0x07
 #define VIDEO_DATA_BLOCK_420	0x0E
+#define VIDEO_CAP_BLOCK_420	0x0F
 #define EDID_BASIC_AUDIO	(1 << 6)
 #define EDID_CEA_YCRCB444	(1 << 5)
 #define EDID_CEA_YCRCB422	(1 << 4)
@@ -3143,11 +3144,21 @@ static int
 do_cea_modes(struct drm_connector *connector, const u8 *db, u8 len)
 {
 	int i, modes = 0;
+	u64 hdmi_420_cap_map = connector->display_info.hdmi.ycbcr420_vcb_map;
 
 	for (i = 0; i < len; i++) {
 		struct drm_display_mode *mode;
 		mode = drm_display_mode_from_vic_index(connector, db, len, i);
 		if (mode) {
+			/*
+			 * ycbcr420 capability block contains a bitmap which
+			 * gives the index of such CEA modes in VDB, which can
+			 * support ycbcr420 sampling output also.
+			 * For example, if the bit 0 in bitmap is set,
+			 * first mode in VDB can support ycbcr420 output too.
+			 */
+			if (hdmi_420_cap_map & (1 << i))
+				mode->flags |= DRM_MODE_FLAG_420;
 			drm_mode_probed_add(connector, mode);
 			modes++;
 		}
@@ -3526,9 +3537,64 @@ static bool cea_db_is_hdmi_vdb420(const u8 *db)
 	return true;
 }
 
+static bool cea_db_is_hdmi_vcb420(const u8 *db)
+{
+	if (cea_db_tag(db) != VIDEO_CAPABILITY_BLOCK)
+		return false;
+
+	if (cea_db_extended_tag(db) != VIDEO_CAP_BLOCK_420)
+		return false;
+
+	return true;
+}
+
 #define for_each_cea_db(cea, i, start, end) \
 	for ((i) = (start); (i) < (end) && (i) + cea_db_payload_len(&(cea)[(i)]) < (end); (i) += cea_db_payload_len(&(cea)[(i)]) + 1)
 
+static void drm_parse_vcb_420_bitmap(struct drm_connector *connector,
+				     const u8 *db)
+{
+	struct drm_display_info *info = &connector->display_info;
+	struct drm_hdmi_info *hdmi = &info->hdmi;
+	u8 map_len = cea_db_payload_len(db) - 1;
+	u8 count;
+	u64 map = 0;
+
+	if (!db)
+		return;
+
+	if (map_len == 0) {
+		/* All CEA modes support ycbcr420 sampling also.*/
+		hdmi->ycbcr420_vcb_map = U64_MAX;
+		return;
+	}
+
+	/*
+	 * This map indicates which of the existing CEA block modes
+	 * from VDB can support YCBCR420 output too. So if bit=0 is
+	 * set, first mode from VDB can support YCBCR420 output too.
+	 * We will parse and keep this map, before parsing VDB itself
+	 * to avoid going through the same block again and again.
+	 *
+	 * Spec is not clear about max possible size of this block.
+	 * Clamping max bitmap block size at 8 bytes. Every byte can
+	 * address 8 CEA modes, in this way this map can address
+	 * 8*8 = first 64 SVDs.
+	 */
+	if (map_len > 8)
+		map_len = 8;
+
+	for (count = 0; count < map_len; count++)
+		map = (db[2 + count] << 8 * count) | map;
+
+	if (map) {
+		DRM_DEBUG_KMS("Sink supports ycbcr 420\n");
+		info->color_formats |= DRM_COLOR_FORMAT_YCRCB420;
+	}
+
+	hdmi->ycbcr420_vcb_map = map;
+}
+
 static int
 add_cea_modes(struct drm_connector *connector, struct edid *edid)
 {
@@ -3561,6 +3627,8 @@ add_cea_modes(struct drm_connector *connector, struct edid *edid)
 				/* Add 4:2:0(only) modes present in EDID */
 				modes += do_420_vdb_modes(connector, vdb420,
 							  vdb420_len);
+			} else if (cea_db_is_hdmi_vcb420(db)) {
+				drm_parse_vcb_420_bitmap(connector, db);
 			}
 		}
 	}
@@ -4241,6 +4309,8 @@ static void drm_parse_cea_ext(struct drm_connector *connector,
 			drm_parse_hdmi_vsdb_video(connector, db);
 		if (cea_db_is_hdmi_forum_vsdb(db))
 			drm_parse_hdmi_forum_vsdb(connector, db);
+		if (cea_db_is_hdmi_vcb420(db))
+			drm_parse_vcb_420_bitmap(connector, db);
 	}
 }
 
@@ -4492,6 +4562,14 @@ int drm_add_edid_modes(struct drm_connector *connector, struct edid *edid)
 	num_modes += add_cvt_modes(connector, edid);
 	num_modes += add_standard_modes(connector, edid);
 	num_modes += add_established_modes(connector, edid);
+
+	/*
+	 * CEA-861-F adds ycbcr capability map block, for HDMI 2.0 sinks.
+	 * To avoid multiple parsing of same block, lets get the sink info
+	 * before parsing CEA modes.
+	 */
+	drm_add_display_info(connector, edid);
+
 	num_modes += add_cea_modes(connector, edid);
 	num_modes += add_alternate_cea_modes(connector, edid);
 	num_modes += add_displayid_detailed_modes(connector, edid);
@@ -4501,8 +4579,6 @@ int drm_add_edid_modes(struct drm_connector *connector, struct edid *edid)
 	if (quirks & (EDID_QUIRK_PREFER_LARGE_60 | EDID_QUIRK_PREFER_LARGE_75))
 		edid_fixup_preferred(connector, quirks);
 
-	drm_add_display_info(connector, edid);
-
 	if (quirks & EDID_QUIRK_FORCE_6BPC)
 		connector->display_info.bpc = 6;
 
diff --git a/include/drm/drm_connector.h b/include/drm/drm_connector.h
index cef76b2..dbfa6a1 100644
--- a/include/drm/drm_connector.h
+++ b/include/drm/drm_connector.h
@@ -136,6 +136,7 @@ struct drm_scdc {
 struct drm_hdmi_info {
 	/** @scdc: sink's scdc support and capabilities */
 	struct drm_scdc scdc;
+	u64 ycbcr420_vcb_map;
 };
 
 /**
-- 
2.7.4

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