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

[Lyude Paul <lyude@redhat.com>]

On Fri, 2020-09-04 at 14:53 +0300, Ville Syrjala wrote:
> From: Ville Syrjälä <ville.syrjala@linux.intel.com>
> 
> 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@linux.intel.com>
> ---
>  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);

Forgot the kdocs again

> +
> +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]);
-- 
Cheers,
	Lyude Paul (she/her)
	Software Engineer at Red Hat

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