usb: typec: Introduce mode_selection bit

The port driver sets this bit for an alternate mode description to indicate
support for the mode selection feature. Once set, individual Alt Mode
drivers will no longer attempt to activate their respective modes within
their probe functions. This prevents race conditions and non-prioritized
activation.
The bit is not set by default. If left unset, the system retains the
current behavior where Alt Mode drivers manage their own activation logic.

Signed-off-by: Andrei Kuchynski <akuchynski@chromium.org>
Reviewed-by: Heikki Krogerus <heikki.krogerus@linux.intel.com>
Link: https://patch.msgid.link/20260119131824.2529334-6-akuchynski@chromium.org
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

Author: Andrei Kuchynski

drivers/usb/typec/altmodes/displayport.c

@@ -804,8 +804,10 @@ int dp_altmode_probe(struct typec_altmode *alt)
 	if (plug)
 		typec_altmode_set_drvdata(plug, dp);
 
-	dp->state = plug ? DP_STATE_ENTER_PRIME : DP_STATE_ENTER;
-	schedule_work(&dp->work);
+	if (!alt->mode_selection) {
+		dp->state = plug ? DP_STATE_ENTER_PRIME : DP_STATE_ENTER;
+		schedule_work(&dp->work);
+	}
 
 	return 0;
 }

drivers/usb/typec/altmodes/thunderbolt.c

@@ -307,7 +307,7 @@ static int tbt_altmode_probe(struct typec_altmode *alt)
 	typec_altmode_set_drvdata(alt, tbt);
 	typec_altmode_set_ops(alt, &tbt_altmode_ops);
 
-	if (tbt_ready(alt)) {
+	if (!alt->mode_selection && tbt_ready(alt)) {
 		if (tbt->plug[TYPEC_PLUG_SOP_P])
 			tbt->state = TBT_STATE_SOP_P_ENTER;
 		else if (tbt->plug[TYPEC_PLUG_SOP_PP])

drivers/usb/typec/class.c

@@ -655,6 +655,7 @@ typec_register_altmode(struct device *parent,
 	alt->adev.svid = desc->svid;
 	alt->adev.mode = desc->mode;
 	alt->adev.vdo = desc->vdo;
+	alt->adev.mode_selection = desc->mode_selection;
 	alt->roles = desc->roles;
 	alt->id = id;
 

include/linux/usb/typec.h

@@ -155,6 +155,7 @@ struct typec_altmode_desc {
 	/* Only used with ports */
 	enum typec_port_data	roles;
 	bool			inactive;
+	bool			mode_selection;
 };
 
 void typec_partner_set_pd_revision(struct typec_partner *partner, u16 pd_revision);

include/linux/usb/typec_altmode.h

@@ -37,6 +37,7 @@ struct typec_altmode {
 	u32				vdo;
 	unsigned int			active:1;
 	u8				priority;
+	bool			mode_selection;
 
 	char				*desc;
 	const struct typec_altmode_ops	*ops;