u32 unused)
 {
        struct intel_digital_port *intel_dig_port = dp_to_dig_port(intel_dp);
+       struct drm_i915_private *i915 =
+                       to_i915(intel_dig_port->base.base.dev);
+       enum phy phy = intel_port_to_phy(i915, intel_dig_port->base.port);
        u32 ret;
 
        ret = DP_AUX_CH_CTL_SEND_BUSY |
              DP_AUX_CH_CTL_FW_SYNC_PULSE_SKL(32) |
              DP_AUX_CH_CTL_SYNC_PULSE_SKL(32);
 
-       if (intel_dig_port->tc_mode == TC_PORT_TBT_ALT)
+       if (intel_phy_is_tc(i915, phy) &&
+           intel_dig_port->tc_mode == TC_PORT_TBT_ALT)
                ret |= DP_AUX_CH_CTL_TBT_IO;
 
        return ret;