drm/i915: Don't enable the DDI-IO power in the TypeC TBT-alt mode

According to the spec we should not enable the DDI-IO power domain if
the TypeC port is in the TBT-alt mode, so do that only in the other
TypeC modes or for non-TypeC ports. See the internal BSpec Index/22243.

v2:
- Add the internal BSpec reference to the log message. (José)

Cc: Manasi Navare <manasi.d.navare@intel.com>
Cc: Anusha Srivatsa <anusha.srivatsa@intel.com>
Cc: José Roberto de Souza <jose.souza@intel.com>
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/20190628143635.22066-6-imre.deak@intel.com

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

@@ -3124,7 +3124,10 @@ static void intel_ddi_pre_enable_dp(struct intel_encoder *encoder,
 
 	intel_ddi_clk_select(encoder, crtc_state);
 
-	intel_display_power_get(dev_priv, dig_port->ddi_io_power_domain);
+	if (!intel_port_is_tc(dev_priv, port) ||
+	    dig_port->tc_mode != TC_PORT_TBT_ALT)
+		intel_display_power_get(dev_priv,
+					dig_port->ddi_io_power_domain);
 
 	icl_program_mg_dp_mode(dig_port);
 	icl_disable_phy_clock_gating(dig_port);
@@ -3306,8 +3309,10 @@ static void intel_ddi_post_disable_dp(struct intel_encoder *encoder,
 	intel_edp_panel_vdd_on(intel_dp);
 	intel_edp_panel_off(intel_dp);
 
-	intel_display_power_put_unchecked(dev_priv,
-					  dig_port->ddi_io_power_domain);
+	if (!intel_port_is_tc(dev_priv, encoder->port) ||
+	    dig_port->tc_mode != TC_PORT_TBT_ALT)
+		intel_display_power_put_unchecked(dev_priv,
+						  dig_port->ddi_io_power_domain);
 
 	intel_ddi_clk_disable(encoder);
 }