drm/i915/dp: read DPCD PSR capability only on eDP

Reduce AUX transactions for non-eDP.
Signed-off-by: Jani Nikula <jani.nikula@intel.com>
Reviewed-by: Todd Previte <tprevite@gmail.com>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>

drivers/gpu/drm/i915/intel_dp.c

@@ -2686,11 +2686,14 @@ intel_dp_get_dpcd(struct intel_dp *intel_dp)
 
 	/* Check if the panel supports PSR */
 	memset(intel_dp->psr_dpcd, 0, sizeof(intel_dp->psr_dpcd));
-	intel_dp_aux_native_read_retry(intel_dp, DP_PSR_SUPPORT,
-				       intel_dp->psr_dpcd,
-				       sizeof(intel_dp->psr_dpcd));
-	if (is_edp_psr(intel_dp))
-		DRM_DEBUG_KMS("Detected EDP PSR Panel.\n");
+	if (is_edp(intel_dp)) {
+		intel_dp_aux_native_read_retry(intel_dp, DP_PSR_SUPPORT,
+					       intel_dp->psr_dpcd,
+					       sizeof(intel_dp->psr_dpcd));
+		if (is_edp_psr(intel_dp))
+			DRM_DEBUG_KMS("Detected EDP PSR Panel.\n");
+	}
+
 	if (!(intel_dp->dpcd[DP_DOWNSTREAMPORT_PRESENT] &
 	      DP_DWN_STRM_PORT_PRESENT))
 		return true; /* native DP sink */