On Fri, 2025-10-17 at 10:31 +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.
>
> Bspec: 70151
> Signed-off-by: Ankit Nautiyal <[email protected]>
> ---
> 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..3f2c319e3d6f 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 6;
I found value 7 in the Bspec you are referring in commit message?
BR,
Jouni Högander
> + 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__ */
