Re: [v4 5/5] drm/edid: check for HF-SCDB block

["Ville Syrjälä" <ville.syrjala@linux.intel.com>]

On Wed, Mar 02, 2022 at 05:35:11PM +0800, Lee Shawn C wrote:
> Find HF-SCDB information in CEA extensions block. And retrieve
> Max_TMDS_Character_Rate that support by sink device.
> 
> Cc: Jani Nikula <jani.nikula@linux.intel.com>
> Cc: Ville Syrjala <ville.syrjala@linux.intel.com>
> Cc: Ankit Nautiyal <ankit.k.nautiyal@intel.com>
> Signed-off-by: Lee Shawn C <shawn.c.lee@intel.com>
> ---
>  drivers/gpu/drm/drm_edid.c | 36 ++++++++++++++++++++++++++++++++++++
>  1 file changed, 36 insertions(+)
> 
> diff --git a/drivers/gpu/drm/drm_edid.c b/drivers/gpu/drm/drm_edid.c
> index 2b8ddc956ce2..d6b48c543c23 100644
> --- a/drivers/gpu/drm/drm_edid.c
> +++ b/drivers/gpu/drm/drm_edid.c
> @@ -3350,6 +3350,7 @@ add_detailed_modes(struct drm_connector *connector, struct edid *edid,
>  #define EXT_VIDEO_DATA_BLOCK_420	0x0E
>  #define EXT_VIDEO_CAP_BLOCK_Y420CMDB	0x0F
>  #define EXT_VIDEO_HF_EEODB_DATA_BLOCK	0x78
> +#define EXT_VIDEO_HF_SCDB_DATA_BLOCK	0x79
>  #define EDID_BASIC_AUDIO	(1 << 6)
>  #define EDID_CEA_YCRCB444	(1 << 5)
>  #define EDID_CEA_YCRCB422	(1 << 4)
> @@ -4277,6 +4278,20 @@ static bool cea_db_is_vcdb(const u8 *db)
>  	return true;
>  }
>  
> +static bool cea_db_is_hf_scdb(const u8 *db)
> +{
> +	if (cea_db_tag(db) != USE_EXTENDED_TAG)
> +		return false;
> +
> +	if (cea_db_payload_len(db) < 7)
> +		return false;
> +
> +	if (cea_db_extended_tag(db) != EXT_VIDEO_HF_SCDB_DATA_BLOCK)
> +		return false;
> +
> +	return true;
> +}
> +
>  static bool cea_db_is_y420cmdb(const u8 *db)
>  {
>  	if (cea_db_tag(db) != USE_EXTENDED_TAG)
> @@ -4987,6 +5002,25 @@ static void drm_parse_vcdb(struct drm_connector *connector, const u8 *db)
>  		info->rgb_quant_range_selectable = true;
>  }
>  
> +static void drm_parse_hf_scdb(struct drm_connector *connector, const u8 *db)
> +{
> +	struct drm_display_info *info = &connector->display_info;
> +	u32 max_tmds_clock;
> +
> +	DRM_DEBUG_KMS("HF-SCDB version 0x%02x\n", db[4]);
> +
> +	max_tmds_clock = db[5] * 5000;
> +	if (info->max_tmds_clock < max_tmds_clock) {
> +		info->max_tmds_clock = max_tmds_clock;
> +		DRM_DEBUG_KMS("HF-SCDB: max TMDS clock %d kHz\n",
> +			      info->max_tmds_clock);
> +	}
> +
> +	/*
> +	 * ToDo: Parse the remaining SCDB data if needed
> +	 */

If I'm reading the spec right this block should contain the exact same
stuff as the HF-VSDB. We should reuse the same code for parsing both.

> +}
> +
>  static
>  void drm_get_max_frl_rate(int max_frl_rate, u8 *max_lanes, u8 *max_rate_per_lane)
>  {
> @@ -5282,6 +5316,8 @@ static void drm_parse_cea_ext(struct drm_connector *connector,
>  			drm_parse_y420cmdb_bitmap(connector, db);
>  		if (cea_db_is_vcdb(db))
>  			drm_parse_vcdb(connector, db);
> +		if (cea_db_is_hf_scdb(db))
> +			drm_parse_hf_scdb(connector, db);
>  		if (cea_db_is_hdmi_hdr_metadata_block(db))
>  			drm_parse_hdr_metadata_block(connector, db);
>  	}
> -- 
> 2.17.1

-- 
Ville Syrjälä
Intel