RE: [PATCH v4 07/16] drm/dp_helper: Add helpers to configure PCONs RGB-YCbCr Conversion

["Shankar, Uma" <uma.shankar@intel.com>]

> -----Original Message-----
> From: Nautiyal, Ankit K <ankit.k.nautiyal@intel.com>
> Sent: Tuesday, December 8, 2020 1:22 PM
> To: intel-gfx@lists.freedesktop.org
> Cc: dri-devel@lists.freedesktop.org; Shankar, Uma <uma.shankar@intel.com>;
> airlied@linux.ie; jani.nikula@linux.intel.com; ville.syrjala@linux.intel.com;
> Kulkarni, Vandita <vandita.kulkarni@intel.com>; Sharma, Swati2
> <swati2.sharma@intel.com>
> Subject: [PATCH v4 07/16] drm/dp_helper: Add helpers to configure PCONs RGB-
> YCbCr Conversion
> 
> DP Specification for DP2.0 to HDMI2.1 Pcon specifies support for conversion of
> colorspace from RGB to YCbCr.
> https://groups.vesa.org/wg/DP/document/previewpdf/15651
> 
> This patch adds the relavant registers and helper functions to get the capability
> and set the color conversion bits for rgb->ycbcr conversion through PCON.
> 
> Signed-off-by: Ankit Nautiyal <ankit.k.nautiyal@intel.com>
> ---
>  drivers/gpu/drm/drm_dp_helper.c | 59 +++++++++++++++++++++++++++++++++
>  include/drm/drm_dp_helper.h     | 10 +++++-
>  2 files changed, 68 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/gpu/drm/drm_dp_helper.c
> b/drivers/gpu/drm/drm_dp_helper.c index d0626f57f99c..344662d5c295 100644
> --- a/drivers/gpu/drm/drm_dp_helper.c
> +++ b/drivers/gpu/drm/drm_dp_helper.c
> @@ -949,6 +949,35 @@ bool
> drm_dp_downstream_444_to_420_conversion(const u8
> dpcd[DP_RECEIVER_CAP_SIZE]  }
> EXPORT_SYMBOL(drm_dp_downstream_444_to_420_conversion);
> 
> +/**
> + * drm_dp_downstream_rgb_to_ycbcr_conversion() - determine downstream
> facing port
> + *                                               RGB->YCbCr conversion capability
> + * @dpcd: DisplayPort configuration data
> + * @port_cap: downstream facing port capabilities
> + *
> + * Returns: whether the downstream facing port can convert RGB->YCbCr
> +*/ bool drm_dp_downstream_rgb_to_ycbcr_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_BT601_RGB_YCBCR_CONV;

I guess there are other conversions also possible, like BT709 and 2020. Update those
as well here.

> +	default:
> +		return false;
> +	}
> +}
> +EXPORT_SYMBOL(drm_dp_downstream_rgb_to_ycbcr_conversion);
> +
>  /**
>   * drm_dp_downstream_mode() - return a mode for downstream facing port
>   * @dev: DRM device
> @@ -3140,3 +3169,33 @@ int drm_dp_pcon_pps_override_param(struct
> drm_dp_aux *aux, u8 pps_param[6])
>  	return 0;
>  }
>  EXPORT_SYMBOL(drm_dp_pcon_pps_override_param);
> +
> +/*
> + * drm_dp_pcon_convert_rgb_to_ycbcr() - Configure the PCon to convert
> +RGB to Ycbcr
> + * @aux: displayPort AUX channel
> + * @color_spc: Color space conversion type
> + *
> + * Returns 0 on success, else returns negative error code.
> + */
> +int drm_dp_pcon_convert_rgb_to_ycbcr(struct drm_dp_aux *aux, u8
> +color_spc) {
> +	int ret;
> +	u8 buf;
> +
> +	if (color_spc != DP_CONVERSION_BT601_RGB_YCBCR_ENABLE ||
> +	    color_spc != DP_CONVERSION_BT709_RGB_YCBCR_ENABLE ||
> +	    color_spc != DP_CONVERSION_BT2020_RGB_YCBCR_ENABLE)
> +		return -EINVAL;

Yeah this is wrong, fix it.

> +
> +	ret = drm_dp_dpcd_readb(aux, DP_PROTOCOL_CONVERTER_CONTROL_2,
> &buf);
> +	if (ret < 0)
> +		return ret;
> +
> +	buf |= color_spc;
> +	ret = drm_dp_dpcd_writeb(aux,
> DP_PROTOCOL_CONVERTER_CONTROL_2, buf);
> +	if (ret < 0)
> +		return ret;
> +
> +	return 0;
> +}
> +EXPORT_SYMBOL(drm_dp_pcon_convert_rgb_to_ycbcr);
> diff --git a/include/drm/drm_dp_helper.h b/include/drm/drm_dp_helper.h index
> 347b4e1a55b4..1b3d54ed7a78 100644
> --- a/include/drm/drm_dp_helper.h
> +++ b/include/drm/drm_dp_helper.h
> @@ -431,6 +431,9 @@ struct drm_device;
>  # 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_DS_HDMI_BT601_RGB_YCBCR_CONV    (1 << 5)
> +# define DP_DS_HDMI_BT709_RGB_YCBCR_CONV    (1 << 6)
> +# define DP_DS_HDMI_BT2020_RGB_YCBCR_CONV   (1 << 7)

I think it would be good to mention the location in spec (section or table),
will make it easier to understand/review by directly going to relevant sections in spec.

> 
>  #define DP_MAX_DOWNSTREAM_PORTS		    0x10
> 
> @@ -1217,7 +1220,9 @@ struct drm_device;
>  # define DP_PCON_ENC_PPS_OVERRIDE_DISABLED      0
>  # define DP_PCON_ENC_PPS_OVERRIDE_EN_PARAMS     1
>  # define DP_PCON_ENC_PPS_OVERRIDE_EN_BUFFER     2
> -
> +# define DP_CONVERSION_BT601_RGB_YCBCR_ENABLE  (1 << 4) # define
> +DP_CONVERSION_BT709_RGB_YCBCR_ENABLE  (1 << 5) # define
> +DP_CONVERSION_BT2020_RGB_YCBCR_ENABLE (1 << 6)
> 
>  /* PCON Downstream HDMI ERROR Status per Lane */
>  #define DP_PCON_HDMI_ERROR_STATUS_LN0          0x3037
> @@ -2178,5 +2183,8 @@ int drm_dp_pcon_dsc_bpp_incr(const u8
> pcon_dsc_dpcd[DP_PCON_DSC_ENCODER_CAP_SIZE
>  int drm_dp_pcon_pps_default(struct drm_dp_aux *aux);  int
> drm_dp_pcon_pps_override_buf(struct drm_dp_aux *aux, u8 pps_buf[128]);  int
> drm_dp_pcon_pps_override_param(struct drm_dp_aux *aux, u8 pps_param[6]);
> +bool drm_dp_downstream_rgb_to_ycbcr_conversion(const u8
> dpcd[DP_RECEIVER_CAP_SIZE],
> +					       const u8 port_cap[4]);
> +int drm_dp_pcon_convert_rgb_to_ycbcr(struct drm_dp_aux *aux, u8
> +color_spc);
> 
>  #endif /* _DRM_DP_HELPER_H_ */
> --
> 2.17.1

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