drm/i915: Disconnect PHYs left connected by BIOS on disabled ports

BIOS may leave a TypeC PHY in a connected state even though the
corresponding port is disabled. This will prevent any hotplug events
from being signalled (after the monitor deasserts and then reasserts its
HPD) until the PHY is disconnected and so the driver will not detect a
connected sink. Rebooting with the PHY in the connected state also
results in a system hang.

Fix the above by disconnecting TypeC PHYs on disabled ports.

Before commit 64851a32 the PHY connected state was read out even
for disabled ports and later the PHY got disconnected as a side effect
of a tc_port_lock/unlock() sequence (during connector probing), hence
recovering the port's hotplug functionality.

Closes: https://gitlab.freedesktop.org/drm/intel/-/issues/5014
Fixes: 64851a32 ("drm/i915/tc: Add a mode for the TypeC PHY's disconnected state")
Cc: <stable@vger.kernel.org> # v5.16+
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/20220217152237.670220-1-imre.deak@intel.com

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

@@ -693,6 +693,8 @@ void intel_tc_port_sanitize(struct intel_digital_port *dig_port)
 {
 	struct drm_i915_private *i915 = to_i915(dig_port->base.base.dev);
 	struct intel_encoder *encoder = &dig_port->base;
+	intel_wakeref_t tc_cold_wref;
+	enum intel_display_power_domain domain;
 	int active_links = 0;
 
 	mutex_lock(&dig_port->tc_lock);
@@ -704,12 +706,11 @@ void intel_tc_port_sanitize(struct intel_digital_port *dig_port)
 
 	drm_WARN_ON(&i915->drm, dig_port->tc_mode != TC_PORT_DISCONNECTED);
 	drm_WARN_ON(&i915->drm, dig_port->tc_lock_wakeref);
-	if (active_links) {
-		enum intel_display_power_domain domain;
-		intel_wakeref_t tc_cold_wref = tc_cold_block(dig_port, &domain);
 
-		dig_port->tc_mode = intel_tc_port_get_current_mode(dig_port);
+	tc_cold_wref = tc_cold_block(dig_port, &domain);
 
+	dig_port->tc_mode = intel_tc_port_get_current_mode(dig_port);
+	if (active_links) {
 		if (!icl_tc_phy_is_connected(dig_port))
 			drm_dbg_kms(&i915->drm,
 				    "Port %s: PHY disconnected with %d active link(s)\n",
@@ -718,9 +719,22 @@ void intel_tc_port_sanitize(struct intel_digital_port *dig_port)
 
 		dig_port->tc_lock_wakeref = tc_cold_block(dig_port,
 							  &dig_port->tc_lock_power_domain);
+	} else {
+		/*
+		 * TBT-alt is the default mode in any case the PHY ownership is not
+		 * held (regardless of the sink's connected live state), so
+		 * we'll just switch to disconnected mode from it here without
+		 * a note.
+		 */
+		if (dig_port->tc_mode != TC_PORT_TBT_ALT)
+			drm_dbg_kms(&i915->drm,
+				    "Port %s: PHY left in %s mode on disabled port, disconnecting it\n",
+				    dig_port->tc_port_name,
+				    tc_port_mode_name(dig_port->tc_mode));
+		icl_tc_phy_disconnect(dig_port);
+	}
 
 	tc_cold_unblock(dig_port, domain, tc_cold_wref);
-	}
 
 	drm_dbg_kms(&i915->drm, "Port %s: sanitize mode (%s)\n",
 		    dig_port->tc_port_name,