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.

Cc: Ville Syrjala <ville.syrj...@linux.intel.com>
Cc: Jose Abreu <joab...@synopsys.com>
Cc: Emil Velikov <emil.l.veli...@gmail.com>

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.

Signed-off-by: Shashank Sharma <shashank.sha...@intel.com>
---
 drivers/gpu/drm/drm_edid.c  | 193 ++++++++++++++++++++++++++++++++++++++++++--
 include/drm/drm_connector.h |  23 ++++++
 2 files changed, 211 insertions(+), 5 deletions(-)

diff --git a/drivers/gpu/drm/drm_edid.c b/drivers/gpu/drm/drm_edid.c
index 6fd8a98..4953f87 100644
--- a/drivers/gpu/drm/drm_edid.c
+++ b/drivers/gpu/drm/drm_edid.c
@@ -2781,7 +2781,9 @@ add_detailed_modes(struct drm_connector *connector, 
struct edid *edid,
 #define VIDEO_BLOCK     0x02
 #define VENDOR_BLOCK    0x03
 #define SPEAKER_BLOCK  0x04
-#define VIDEO_CAPABILITY_BLOCK 0x07
+#define VIDEO_CAPABILITY_BLOCK 0x07
+#define VIDEO_DATA_BLOCK_420   0x0E
+#define VIDEO_CAP_BLOCK_Y420CMDB 0x0F
 #define EDID_BASIC_AUDIO       (1 << 6)
 #define EDID_CEA_YCRCB444      (1 << 5)
 #define EDID_CEA_YCRCB422      (1 << 4)
@@ -3143,15 +3145,103 @@ drm_display_mode_from_vic_index(struct drm_connector 
*connector,
        return newmode;
 }
 
+/*
+ * do_ycbcr_420_vdb_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
+ *
+ * CEA-861-F has added a new video block called YCBCR 420 Video
+ * Data Block (ycbcr 420 vdb). This block contains modes which
+ * support YCBCR 420 HDMI output (only YCBCR 420). This function
+ * parses the block and adds these modes into connector's mode list.
+ */
+static int do_ycbcr_420_vdb_modes(struct drm_connector *connector,
+                                  const u8 *svds, u8 svds_len)
+{
+       int modes = 0, i;
+       struct drm_device *dev = connector->dev;
+       struct drm_display_mode *newmode;
+       struct drm_display_info *info = &connector->display_info;
+       struct drm_hdmi_info *hdmi = &info->hdmi;
+
+       for (i = 0; i < svds_len; i++) {
+               u8 vic = svds[i] & 0x7f;
+
+               newmode = drm_mode_duplicate(dev, &edid_cea_modes[vic]);
+               if (!newmode)
+                       break;
+               /*
+                * ycbcr420_vdb_modes is a fix position 128 bit bitmap.
+                * Every bit here represents a VIC, from CEA-861-F list.
+                * So if bit[n] is set, it indicates vic[n+1] supports
+                * YCBCR420 output. Bit 0 is dummy, as VICs start at 1.
+                * ycbcr420_vcb_modes[0] = |VIC=64 |VIC=63 |.....|VIC=2 |VIC=1 |
+                * ycbcr420_vcb_modes[1] = |VIC=128|VIC=127|.....|VIC=66|VIC=65|
+                */
+               bitmap_set(hdmi->ycbcr420_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_vcb_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_vcb_modes(struct drm_connector *connector, u8 vic)
+{
+       struct drm_hdmi_info *hdmi = &connector->display_info.hdmi;
+
+       /* VICs are 1 to 127(107 defined till CEA-861-F) */
+       vic &= 127;
+
+       /*
+        * ycbcr420_vcb_modes is a fix position 128 bit bitmap.
+        * Every bit here represents a VIC, from CEA-861-F list.
+        * So if bit[n] is set, it indicates vic[n+1] supports
+        * YCBCR420 output. Bit 0 is dummy, as VICs start at 1.
+        * ycbcr420_vcb_modes[0] = |VIC=64 |VIC=63 |.....|VIC=2 |VIC=1 |
+        * ycbcr420_vcb_modes[1] = |VIC=128|VIC=127|.....|VIC=66|VIC=65|
+        * Difference between a vcb_mode and vdb_mode is that a vcb_mode
+        * can support other HDMI outputs like RGB/YCBCR444/422 also
+        * along with YCBCR 240, whereas a vdb_mode can only support YCBCR
+        * 420 HDMI output.
+        */
+       bitmap_set(hdmi->ycbcr420_vcb_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 (connector->is_hdmi2_src &&
+                               test_bit(i, &hdmi->ycbcr420_vcb_map))
+                               drm_add_vcb_modes(connector, db[i]);
+
                        drm_mode_probed_add(connector, mode);
                        modes++;
                }
@@ -3427,6 +3517,12 @@ do_hdmi_vsdb_modes(struct drm_connector *connector, 
const u8 *db, u8 len,
 }
 
 static int
+cea_db_extended_tag(const u8 *db)
+{
+       return db[1];
+}
+
+static int
 cea_db_payload_len(const u8 *db)
 {
        return db[0] & 0x1f;
@@ -3487,9 +3583,81 @@ static bool cea_db_is_hdmi_forum_vsdb(const u8 *db)
        return oui == HDMI_FORUM_IEEE_OUI;
 }
 
+static bool cea_db_is_ycbcr_420_cmdb(const u8 *db)
+{
+       u8 len = cea_db_payload_len(db);
+
+       if (cea_db_tag(db) != VIDEO_CAPABILITY_BLOCK)
+               return false;
+
+       if (!len)
+               return false;
+
+       if (cea_db_extended_tag(db) != VIDEO_CAP_BLOCK_Y420CMDB)
+               return false;
+
+       return true;
+}
+
+static bool cea_db_is_ycbcr_420_vdb(const u8 *db)
+{
+       if (cea_db_tag(db) != VIDEO_CAPABILITY_BLOCK)
+               return false;
+
+       if (cea_db_extended_tag(db) != 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 (!db)
+               return;
+
+       if (map_len == 0) {
+               /* All CEA modes support ycbcr420 sampling also.*/
+               hdmi->ycbcr420_vcb_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) {
+               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)
 {
@@ -3512,10 +3680,17 @@ 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_ycbcr_420_vdb(db) &&
+                                       connector->is_hdmi2_src) {
+                               const u8 *vdb420 = &db[2];
+
+                               /* Add 4:2:0(only) modes present in EDID */
+                               modes += do_ycbcr_420_vdb_modes(connector,
+                                                               vdb420,
+                                                               dbl - 1);
                        }
                }
        }
@@ -4196,6 +4371,8 @@ 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_ycbcr_420_cmdb(db))
+                       drm_parse_y420cmdb_bitmap(connector, db);
        }
 }
 
@@ -4430,6 +4607,13 @@ int drm_add_edid_modes(struct drm_connector *connector, 
struct edid *edid)
        quirks = edid_get_quirks(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);
+
+       /*
         * EDID spec says modes should be preferred in this order:
         * - preferred detailed mode
         * - other detailed modes from base block
@@ -4450,14 +4634,13 @@ 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);
 
        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 390319c..5a47c33 100644
--- a/include/drm/drm_connector.h
+++ b/include/drm/drm_connector.h
@@ -137,6 +137,28 @@ struct drm_scdc {
 struct drm_hdmi_info {
        /** @scdc: sink's scdc support and capabilities */
        struct drm_scdc scdc;
+
+       /**
+        * @ycbcr420_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 ycbcr420_vdb_modes[BITS_TO_LONGS(128)];
+
+       /**
+        * @ycbcr420_vcb_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 ycbcr420_vcb_modes[BITS_TO_LONGS(128)];
+
+       /** @ycbcr420_vcb_map: bitmap of SVD index, to extraxt vcb modes */
+       unsigned long ycbcr420_vcb_map;
+
+       /** @ycbcr420_dc_modes: bitmap of deep color support index */
+       u8 ycbcr420_dc_modes;
 };
 
 /**
@@ -200,6 +222,7 @@ 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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