[PATCH 05/20] drm/edid: parse YCBCR420 videomodes from EDID

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

HDMI 2.0 spec adds support for YCBCR420 sub-sampled output.
CEA-861-F adds two new blocks in EDID's CEA extension blocks,
to provide information about sink's YCBCR420 output capabilities.

These blocks are:

- YCBCR420vdb(YCBCR 420 video data block):
This block contains VICs of video modes, which can be sopported only
in YCBCR420 output mode (Not in RGB/YCBCR444/422. Its like a normal
SVD block, valid for YCBCR420 modes only.

- YCBCR420cmdb(YCBCR 420 capability map data block):
This block gives information about video modes which can support
YCBCR420 output mode also (along with RGB,YCBCR444/422 etc) This
block contains a bitmap index of normal svd videomodes, which can
support YCBCR420 output too.
So if bit 0 from first vcb byte is set, first video mode in the svd
list can support YCBCR420 output too. Bit 1 means second video mode
from svd list can support YCBCR420 output too, and so on.

This patch adds two bitmaps in display's hdmi_info structure, one each
for VCB and VDB modes. If the source is HDMI 2.0 capable, this patch
adds:
- VDB modes (YCBCR 420 only modes) in connector's mode list, also makes
  an entry in the vdb_bitmap per vic.
- VCB modes (YCBCR 420 also modes) only entry in the vcb_bitmap.

V2: Addressed
    Review comments from Emil:
    - Use 1ULL<<i instead of 1<<i to make sure the output is 64bit.
    - Use the suggested method for updating dbmap.
    - Add documentation for YCBCR420_vcb_map to fix kbuild warning.

    Review comments from Ville:
    - Do not expose the YCBCR420 flags in uabi layer, keep it internal.
    - Save a map of YCBCR420 modes for future reference.
    - Check db length before trying to parse extended tag.
    - Add a warning if there are > 64 modes in capability map block.
    - Use y420cmdb in function names and macros while dealing with vcb
      to be aligned with spec.
    - Move the display information parsing block ahead of mode parsing
      blocks.

V3: Addressed design/review comments from Ville
    - Do not add flags in video modes, else we have to expose them to user
    - There should not be a UABI change, and kernel should detect the
      choice of the output based on type of mode, and the bitmaps.
    - Use standard bitops from kernel bitmap header, instead of calculating
      bit positions manually.

V4: Addressed review comments from Ville:
    - s/ycbcr_420_vdb/y420vdb
    - s/ycbcr_420_vcb/y420cmdb
    - Be less verbose on description of do_y420vdb_modes
    - Move newmode variable in the loop scope.
    - Use svd_to_vic() to get a VIC, instead of 0x7f
    - Remove bitmap description for CMDB modes & VDB modes
    - Dont add connector->ycbcr_420_allowed check for cmdb modes
    - Remove 'len' variable, in is_y420cmdb function, which is used
      only once
    - Add length check in is_y420vdb function
    - Remove unnecessary if (!db) check in function parse_y420cmdb_bitmap
    - Do not add print about YCBCR 420 modes
    - Fix indentation in few places
    - Move ycbcr420_dc_modes in next patch, where its used
    - Add a separate patch for movement of drm_add_display_info()

V5: Addressed review comments from Ville:
    - Add the patch which cleans up the current EXTENDED_TAG usage
    - Make y420_cmdb_map u64
    - Do not block ycbcr420 modes while parsing the EDID, rather
      add a separate helper function to prune ycbcr420-only modes from
      connector's probed modes.

V6: Rebase

Signed-off-by: Shashank Sharma <shashank.sharma@intel.com>
---
 drivers/gpu/drm/drm_edid.c  | 148 +++++++++++++++++++++++++++++++++++++++++++-
 include/drm/drm_connector.h |  20 ++++++
 2 files changed, 166 insertions(+), 2 deletions(-)

diff --git a/drivers/gpu/drm/drm_edid.c b/drivers/gpu/drm/drm_edid.c
index 9a07f42..10dab62 100644
--- a/drivers/gpu/drm/drm_edid.c
+++ b/drivers/gpu/drm/drm_edid.c
@@ -2783,6 +2783,8 @@ add_detailed_modes(struct drm_connector *connector, struct edid *edid,
 #define SPEAKER_BLOCK	0x04
 #define USE_EXTENDED_TAG 0x07
 #define EXT_VIDEO_CAPABILITY_BLOCK 0x00
+#define EXT_VIDEO_DATA_BLOCK_420	0x0E
+#define EXT_VIDEO_CAP_BLOCK_Y420CMDB 0x0F
 #define EDID_BASIC_AUDIO	(1 << 6)
 #define EDID_CEA_YCRCB444	(1 << 5)
 #define EDID_CEA_YCRCB422	(1 << 4)
@@ -3154,15 +3156,79 @@ drm_display_mode_from_vic_index(struct drm_connector *connector,
 	return newmode;
 }
 
+/*
+ * do_y420vdb_modes - Parse YCBCR 420 only modes
+ * @connector: connector corresponding to the HDMI sink
+ * @svds: start of the data block of CEA YCBCR 420 VDB
+ * @len: length of the CEA YCBCR 420 VDB
+ *
+ * Parse the CEA-861-F YCBCR 420 Video Data Block (Y420VDB)
+ * which contains modes which can be supported in YCBCR 420
+ * output format only.
+ */
+static int do_y420vdb_modes(struct drm_connector *connector,
+				   const u8 *svds, u8 svds_len)
+{
+	int modes = 0, i;
+	struct drm_device *dev = connector->dev;
+	struct drm_display_info *info = &connector->display_info;
+	struct drm_hdmi_info *hdmi = &info->hdmi;
+
+	for (i = 0; i < svds_len; i++) {
+		u8 vic = svd_to_vic(svds[i]);
+		struct drm_display_mode *newmode;
+
+		newmode = drm_mode_duplicate(dev, &edid_cea_modes[vic]);
+		if (!newmode)
+			break;
+		bitmap_set(hdmi->y420_vdb_modes, vic, 1);
+		drm_mode_probed_add(connector, newmode);
+		modes++;
+	}
+
+	if (modes > 0)
+		info->color_formats |= DRM_COLOR_FORMAT_YCRCB420;
+	return modes;
+}
+
+/*
+ * drm_add_cmdb_modes - Add a YCBCR 420 mode into bitmap
+ * @connector: connector corresponding to the HDMI sink
+ * @vic: CEA vic for the video mode to be added in the map
+ *
+ * Makes an entry for a videomode in the YCBCR 420 bitmap
+ */
+static void
+drm_add_cmdb_modes(struct drm_connector *connector, u8 svd)
+{
+	u8 vic = svd_to_vic(svd);
+	struct drm_hdmi_info *hdmi = &connector->display_info.hdmi;
+
+	bitmap_set(hdmi->y420_cmdb_modes, vic, 1);
+}
+
 static int
 do_cea_modes(struct drm_connector *connector, const u8 *db, u8 len)
 {
 	int i, modes = 0;
+	struct drm_hdmi_info *hdmi = &connector->display_info.hdmi;
 
 	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 CEA modes from CEA VDB, which
+			 * can support YCBCR 420 sampling output also (apart
+			 * from RGB/YCBCR444 etc).
+			 * For example, if the bit 0 in bitmap is set,
+			 * first mode in VDB can support YCBCR420 output too.
+			 * Add YCBCR420 modes only if sink is HDMI 2.0 capable.
+			 */
+			if (hdmi->y420_cmdb_map & (1 << i))
+				drm_add_cmdb_modes(connector, db[i]);
+
 			drm_mode_probed_add(connector, mode);
 			modes++;
 		}
@@ -3504,9 +3570,78 @@ static bool cea_db_is_hdmi_forum_vsdb(const u8 *db)
 	return oui == HDMI_FORUM_IEEE_OUI;
 }
 
+static bool cea_db_is_y420cmdb(const u8 *db)
+{
+
+	if (cea_db_tag(db) != USE_EXTENDED_TAG)
+		return false;
+
+	if (!cea_db_payload_len(db))
+		return false;
+
+	if (cea_db_extended_tag(db) != EXT_VIDEO_CAP_BLOCK_Y420CMDB)
+		return false;
+
+	return true;
+}
+
+static bool cea_db_is_y420vdb(const u8 *db)
+{
+	if (cea_db_tag(db) != USE_EXTENDED_TAG)
+		return false;
+
+	if (!cea_db_payload_len(db))
+		return false;
+
+	if (cea_db_extended_tag(db) != EXT_VIDEO_DATA_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_y420cmdb_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 (map_len == 0) {
+		/* All CEA modes support ycbcr420 sampling also.*/
+		hdmi->y420_cmdb_map = U64_MAX;
+		info->color_formats |= DRM_COLOR_FORMAT_YCRCB420;
+		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 (WARN_ON_ONCE(map_len > 8))
+		map_len = 8;
+
+	for (count = 0; count < map_len; count++)
+		map |= (u64)db[2 + count] << (8 * count);
+
+	if (map)
+		info->color_formats |= DRM_COLOR_FORMAT_YCRCB420;
+
+	hdmi->y420_cmdb_map = map;
+}
+
 static int
 add_cea_modes(struct drm_connector *connector, struct edid *edid)
 {
@@ -3529,10 +3664,16 @@ add_cea_modes(struct drm_connector *connector, struct edid *edid)
 				video = db + 1;
 				video_len = dbl;
 				modes += do_cea_modes(connector, video, dbl);
-			}
-			else if (cea_db_is_hdmi_vsdb(db)) {
+			} else if (cea_db_is_hdmi_vsdb(db)) {
 				hdmi = db;
 				hdmi_len = dbl;
+			} else if (cea_db_is_y420vdb(db)) {
+				const u8 *vdb420 = &db[2];
+
+				/* Add 4:2:0(only) modes present in EDID */
+				modes += do_y420vdb_modes(connector,
+							  vdb420,
+							  dbl - 1);
 			}
 		}
 	}
@@ -4215,6 +4356,8 @@ 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_y420cmdb(db))
+			drm_parse_y420cmdb_bitmap(connector, db);
 	}
 }
 
@@ -4476,6 +4619,7 @@ int drm_add_edid_modes(struct drm_connector *connector, struct edid *edid)
 	num_modes += add_cea_modes(connector, edid);
 	num_modes += add_alternate_cea_modes(connector, edid);
 	num_modes += add_displayid_detailed_modes(connector, edid);
+
 	if (edid->features & DRM_EDID_FEATURE_DEFAULT_GTF)
 		num_modes += add_inferred_modes(connector, edid);
 
diff --git a/include/drm/drm_connector.h b/include/drm/drm_connector.h
index ae5b7dc..b3af8e3 100644
--- a/include/drm/drm_connector.h
+++ b/include/drm/drm_connector.h
@@ -135,6 +135,25 @@ struct drm_scdc {
 struct drm_hdmi_info {
 	/** @scdc: sink's scdc support and capabilities */
 	struct drm_scdc scdc;
+
+	/**
+	 * @y420_vdb_modes: bitmap of modes which can support ycbcr420
+	 * output only (not normal RGB/YCBCR444/422 outputs). There are total
+	 * 107 VICs defined by CEA-861-F spec, so the size is 128 bits to map
+	 * upto 128 VICs;
+	 */
+	unsigned long y420_vdb_modes[BITS_TO_LONGS(128)];
+
+	/**
+	 * @y420_cmdb_modes: bitmap of modes which can support ycbcr420
+	 * output also, along with normal HDMI outputs. There are total 107
+	 * VICs defined by CEA-861-F spec, so the size is 128 bits to map upto
+	 * 128 VICs;
+	 */
+	unsigned long y420_cmdb_modes[BITS_TO_LONGS(128)];
+
+	/** @y420_cmdb_map: bitmap of SVD index, to extraxt vcb modes */
+	u64 y420_cmdb_map;
 };
 
 /**
@@ -198,6 +217,7 @@ struct drm_display_info {
 #define DRM_COLOR_FORMAT_RGB444		(1<<0)
 #define DRM_COLOR_FORMAT_YCRCB444	(1<<1)
 #define DRM_COLOR_FORMAT_YCRCB422	(1<<2)
+#define DRM_COLOR_FORMAT_YCRCB420	(1<<3)
 
 	/**
 	 * @color_formats: HDMI Color formats, selects between RGB and YCrCb
-- 
2.7.4

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