drm/nouveau/kms: Use new drm_dp_read_mst_cap() helper for checking MST caps

Signed-off-by: Lyude Paul <lyude@redhat.com>
Reviewed-by: Ben Skeggs <bskeggs@redhat.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20200826182456.322681-11-lyude@redhat.com

drivers/gpu/drm/nouveau/nouveau_dp.c

@@ -44,7 +44,6 @@ nouveau_dp_probe_dpcd(struct nouveau_connector *nv_connector,
 	struct nv50_mstm *mstm = NULL;
 	int ret;
 	u8 *dpcd = outp->dp.dpcd;
-	u8 tmp;
 
 	ret = drm_dp_dpcd_read(aux, DP_DPCD_REV, dpcd, DP_RECEIVER_CAP_SIZE);
 	if (ret == DP_RECEIVER_CAP_SIZE && dpcd[DP_DPCD_REV]) {
@@ -56,19 +55,10 @@ nouveau_dp_probe_dpcd(struct nouveau_connector *nv_connector,
 		return connector_status_disconnected;
 	}
 
-	if (nouveau_mst)
+	if (nouveau_mst) {
 		mstm = outp->dp.mstm;
-
-	if (mstm) {
-		if (dpcd[DP_DPCD_REV] >= DP_DPCD_REV_12) {
-			ret = drm_dp_dpcd_readb(aux, DP_MSTM_CAP, &tmp);
-			if (ret < 0)
-				return connector_status_disconnected;
-
-			mstm->can_mst = !!(tmp & DP_MST_CAP);
-		} else {
-			mstm->can_mst = false;
-		}
+		if (mstm)
+			mstm->can_mst = drm_dp_read_mst_cap(aux, dpcd);
 	}
 
 	return connector_status_connected;