On 9/11/2025 7:44 PM, Ville Syrjälä wrote:
On Thu, Sep 11, 2025 at 08:15:45AM +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 and current line time.
Used to ensure adequate vblank when features like DSC/HDR are enabled.
Bspec: 70151
Signed-off-by: Ankit Nautiyal <ankit.k.nauti...@intel.com>
Reviewed-by: Mitul Golani <mitulkumar.ajitkumar.gol...@intel.com>
---
drivers/gpu/drm/i915/display/intel_dp.c | 47 +++++++++++++++++++++++++
drivers/gpu/drm/i915/display/intel_dp.h | 2 ++
2 files changed, 49 insertions(+)
diff --git a/drivers/gpu/drm/i915/display/intel_dp.c
b/drivers/gpu/drm/i915/display/intel_dp.c
index 2eab591a8ef5..83c46e4680b3 100644
--- a/drivers/gpu/drm/i915/display/intel_dp.c
+++ b/drivers/gpu/drm/i915/display/intel_dp.c
@@ -6857,3 +6857,50 @@ void intel_dp_mst_resume(struct intel_display *display)
}
}
}
+
+static
+int intel_dp_get_sdp_latency(u32 type, int linetime_us)
The "get" in the name is redundant.
Hmm ok, we can simply have intel_dp_sdp_latency().
+{
+ int lines;
+
+ switch (type) {
+ case DP_SDP_VSC_EXT_VESA:
+ case DP_SDP_VSC_EXT_CEA:
+ lines = 10;
+ break;
+ case HDMI_PACKET_TYPE_GAMUT_METADATA:
+ lines = 8;
+ break;
+ case DP_SDP_PPS:
+ lines = 6;
+ break;
+ default:
+ lines = 0;
+ break;
+ }
We should probably calculate these properly instead of
just hardcoding annoying magic numbers. But I suppose
these are supposed to be some kind of semi worst case
numbers so perhaps OK for now.
Yeah these are the numbers for worst case as mentioned in Bspec.
Regards,
Ankit
+
+ return lines * linetime_us;
+}
+
+int intel_dp_compute_sdp_latency(const struct intel_crtc_state *crtc_state,
+ bool assume_all_enabled)
+{
+ const struct drm_display_mode *adjusted_mode =
&crtc_state->hw.adjusted_mode;
+ int sdp_latency = 0;
+ int linetime_us;
+
+ linetime_us = DIV_ROUND_UP(adjusted_mode->crtc_htotal * 1000,
+ adjusted_mode->crtc_clock);
+ if (assume_all_enabled ||
+ crtc_state->infoframes.enable &
+ intel_hdmi_infoframe_enable(HDMI_PACKET_TYPE_GAMUT_METADATA))
+ sdp_latency = max(sdp_latency,
+
intel_dp_get_sdp_latency(HDMI_PACKET_TYPE_GAMUT_METADATA,
+ linetime_us));
+
+ if (assume_all_enabled || crtc_state->dsc.compression_enable)
+ sdp_latency = max(sdp_latency,
+ intel_dp_get_sdp_latency(DP_SDP_PPS,
linetime_us));
+
+ return sdp_latency;
+}
diff --git a/drivers/gpu/drm/i915/display/intel_dp.h
b/drivers/gpu/drm/i915/display/intel_dp.h
index f90cfd1dbbd0..d222749b191c 100644
--- a/drivers/gpu/drm/i915/display/intel_dp.h
+++ b/drivers/gpu/drm/i915/display/intel_dp.h
@@ -215,5 +215,7 @@ int intel_dp_compute_min_hblank(struct intel_crtc_state
*crtc_state,
int intel_dp_dsc_bpp_step_x16(const struct intel_connector *connector);
void intel_dp_dpcd_set_probe(struct intel_dp *intel_dp, bool
force_on_external);
bool intel_dp_in_hdr_mode(const struct drm_connector_state *conn_state);
+int intel_dp_compute_sdp_latency(const struct intel_crtc_state *crtc_state,
+ bool assume_all_enabled);
#endif /* __INTEL_DP_H__ */
--
2.45.2
