drm/dp: Add support to indicate if sink supports AS SDP

Add an API that indicates support for Adaptive Sync SDP in
the sink, which can be utilized by the rest of the DP programming.

--v1:
- Format commit message properly.
Signed-off-by: Mitul Golani <mitulkumar.ajitkumar.golani@intel.com>
Reviewed-by: Ankit Nautiyal <ankit.k.nautiyal@intel.com>
Signed-off-by: Ankit Nautiyal <ankit.k.nautiyal@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20240322031157.3823909-2-mitulkumar.ajitkumar.golani@intel.com

drivers/gpu/drm/display/drm_dp_helper.c

@@ -2948,6 +2948,31 @@ void drm_dp_vsc_sdp_log(struct drm_printer *p, const struct drm_dp_vsc_sdp *vsc)
 }
 EXPORT_SYMBOL(drm_dp_vsc_sdp_log);
 
+/**
+ * drm_dp_as_sdp_supported() - check if adaptive sync sdp is supported
+ * @aux: DisplayPort AUX channel
+ * @dpcd: DisplayPort configuration data
+ *
+ * Returns true if adaptive sync sdp is supported, else returns false
+ */
+bool drm_dp_as_sdp_supported(struct drm_dp_aux *aux, const u8 dpcd[DP_RECEIVER_CAP_SIZE])
+{
+	u8 rx_feature;
+
+	if (dpcd[DP_DPCD_REV] < DP_DPCD_REV_13)
+		return false;
+
+	if (drm_dp_dpcd_readb(aux, DP_DPRX_FEATURE_ENUMERATION_LIST_CONT_1,
+			      &rx_feature) != 1) {
+		drm_dbg_dp(aux->drm_dev,
+			   "Failed to read DP_DPRX_FEATURE_ENUMERATION_LIST_CONT_1\n");
+		return false;
+	}
+
+	return (rx_feature & DP_ADAPTIVE_SYNC_SDP_SUPPORTED);
+}
+EXPORT_SYMBOL(drm_dp_as_sdp_supported);
+
 /**
  * drm_dp_vsc_sdp_supported() - check if vsc sdp is supported
  * @aux: DisplayPort AUX channel

include/drm/display/drm_dp_helper.h

@@ -101,6 +101,7 @@ struct drm_dp_vsc_sdp {
 void drm_dp_vsc_sdp_log(struct drm_printer *p, const struct drm_dp_vsc_sdp *vsc);
 
 bool drm_dp_vsc_sdp_supported(struct drm_dp_aux *aux, const u8 dpcd[DP_RECEIVER_CAP_SIZE]);
+bool drm_dp_as_sdp_supported(struct drm_dp_aux *aux, const u8 dpcd[DP_RECEIVER_CAP_SIZE]);
 
 int drm_dp_psr_setup_time(const u8 psr_cap[EDP_PSR_RECEIVER_CAP_SIZE]);