drm/i915: Fix AUX power domain toggling across TypeC mode resets

Make sure to select the port's AUX power domain while holding the TC
port lock. The domain depends on the port's current TC mode, which may
get changed under us if we're not holding the lock.

This was left out from
commit 8c10e22 ("drm/i915: Keep the TypeC port mode fixed for detect/AUX transfers")

Cc: <stable@vger.kernel.org> # v5.4+
Signed-off-by: Imre Deak <imre.deak@intel.com>
Reviewed-by: José Roberto de Souza <jose.souza@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20200514204553.27193-1-imre.deak@intel.com

drivers/gpu/drm/i915/display/intel_dp.c

@@ -1359,8 +1359,7 @@ intel_dp_aux_xfer(struct intel_dp *intel_dp,
 	bool is_tc_port = intel_phy_is_tc(i915, phy);
 	i915_reg_t ch_ctl, ch_data[5];
 	u32 aux_clock_divider;
-	enum intel_display_power_domain aux_domain =
-		intel_aux_power_domain(intel_dig_port);
+	enum intel_display_power_domain aux_domain;
 	intel_wakeref_t aux_wakeref;
 	intel_wakeref_t pps_wakeref;
 	int i, ret, recv_bytes;
@@ -1375,6 +1374,8 @@ intel_dp_aux_xfer(struct intel_dp *intel_dp,
 	if (is_tc_port)
 		intel_tc_port_lock(intel_dig_port);
 
+	aux_domain = intel_aux_power_domain(intel_dig_port);
+
 	aux_wakeref = intel_display_power_get(i915, aux_domain);
 	pps_wakeref = pps_lock(intel_dp);