drm/i915/tc: Wait for IOM/FW PHY initialization of legacy TC ports

During boot-up/system resume, the TC PHY on legacy ports will be
initialized by the IOM/TCSS firmware regardless of a sink being
connected or not (as opposed to DP-alt/TBT ports, which the FW only
inits once a sink is connected).

Wait for the above initialization to complete during HW readout, so that
connecting the PHY later will already see the expected PHY ready state.
Signed-off-by: Imre Deak <imre.deak@intel.com>
Reviewed-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20230316131724.359612-6-imre.deak@intel.com

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

@@ -582,6 +582,15 @@ static bool icl_tc_phy_is_connected(struct intel_digital_port *dig_port)
 	       dig_port->tc_mode == TC_PORT_LEGACY;
 }
 
+static void tc_phy_wait_for_ready(struct intel_digital_port *dig_port)
+{
+	struct drm_i915_private *i915 = to_i915(dig_port->base.base.dev);
+
+	if (wait_for(tc_phy_status_complete(dig_port), 100))
+		drm_err(&i915->drm, "Port %s: timeout waiting for PHY ready\n",
+			dig_port->tc_port_name);
+}
+
 static enum tc_port_mode
 intel_tc_port_get_current_mode(struct intel_digital_port *dig_port)
 {
@@ -589,6 +598,14 @@ intel_tc_port_get_current_mode(struct intel_digital_port *dig_port)
 	u32 live_status_mask = tc_port_live_status_mask(dig_port);
 	enum tc_port_mode mode;
 
+	/*
+	 * For legacy ports the IOM firmware initializes the PHY during boot-up
+	 * and system resume whether or not a sink is connected. Wait here for
+	 * the initialization to get ready.
+	 */
+	if (dig_port->tc_legacy_port)
+		tc_phy_wait_for_ready(dig_port);
+
 	if (!tc_phy_is_owned(dig_port) ||
 	    drm_WARN_ON(&i915->drm, !tc_phy_status_complete(dig_port)))
 		return TC_PORT_TBT_ALT;