Re: [PATCH 2/5] drm/i915/dp: Add helper to get min sdp guardband

["Hogander, Jouni" <jouni.hogander@intel.com>]

On Fri, 2025-10-17 at 18:05 +0530, Ankit Nautiyal wrote:
> Add a helper to compute vblank time needed for transmitting specific
> DisplayPort SDPs like PPS, GAMUT_METADATA, and VSC_EXT. Latency is
> based on line count per packet type.
> 
> This will be used to ensure adequate guardband when features like
> DSC/HDR
> are enabled.
> 
> v2: Correct the lines required for PPS SDP. (Jouni)
> 
> Bspec: 70151
> Signed-off-by: Ankit Nautiyal <ankit.k.nautiyal@intel.com>

Reviewed-by: Jouni Högander <jouni.hogander@intel.com>
> ---
>  drivers/gpu/drm/i915/display/intel_dp.c | 36
> +++++++++++++++++++++++++
>  drivers/gpu/drm/i915/display/intel_dp.h |  2 ++
>  2 files changed, 38 insertions(+)
> 
> diff --git a/drivers/gpu/drm/i915/display/intel_dp.c
> b/drivers/gpu/drm/i915/display/intel_dp.c
> index 7059d55687cf..acbb4d476543 100644
> --- a/drivers/gpu/drm/i915/display/intel_dp.c
> +++ b/drivers/gpu/drm/i915/display/intel_dp.c
> @@ -6990,3 +6990,39 @@ int intel_dp_compute_config_late(struct
> intel_encoder *encoder,
>  
>  	return 0;
>  }
> +
> +static
> +int intel_dp_get_lines_for_sdp(u32 type)
> +{
> +	switch (type) {
> +	case DP_SDP_VSC_EXT_VESA:
> +	case DP_SDP_VSC_EXT_CEA:
> +		return 10;
> +	case HDMI_PACKET_TYPE_GAMUT_METADATA:
> +		return 8;
> +	case DP_SDP_PPS:
> +		return 7;
> +	default:
> +		break;
> +	}
> +
> +	return 0;
> +}
> +
> +int intel_dp_sdp_min_guardband(const struct intel_crtc_state
> *crtc_state,
> +			       bool assume_all_enabled)
> +{
> +	int sdp_guardband = 0;
> +
> +	if (assume_all_enabled ||
> +	    crtc_state->infoframes.enable &
> +	   
> intel_hdmi_infoframe_enable(HDMI_PACKET_TYPE_GAMUT_METADATA))
> +		sdp_guardband = max(sdp_guardband,
> +				   
> intel_dp_get_lines_for_sdp(HDMI_PACKET_TYPE_GAMUT_METADATA));
> +
> +	if (assume_all_enabled ||
> +	    crtc_state->dsc.compression_enable)
> +		sdp_guardband = max(sdp_guardband,
> intel_dp_get_lines_for_sdp(DP_SDP_PPS));
> +
> +	return sdp_guardband;
> +}
> diff --git a/drivers/gpu/drm/i915/display/intel_dp.h
> b/drivers/gpu/drm/i915/display/intel_dp.h
> index 281ced3a3b39..7ee5aeb28fe2 100644
> --- a/drivers/gpu/drm/i915/display/intel_dp.h
> +++ b/drivers/gpu/drm/i915/display/intel_dp.h
> @@ -221,5 +221,7 @@ bool intel_dp_in_hdr_mode(const struct
> drm_connector_state *conn_state);
>  int intel_dp_compute_config_late(struct intel_encoder *encoder,
>  				 struct intel_crtc_state
> *crtc_state,
>  				 struct drm_connector_state
> *conn_state);
> +int intel_dp_sdp_min_guardband(const struct intel_crtc_state
> *crtc_state,
> +			       bool assume_all_enabled);
>  
>  #endif /* __INTEL_DP_H__ */