usb: typec: tcpm: Add callbacks to mitigate wakeups due to contaminant

On some of the TCPC implementations, when the Type-C port is exposed
to contaminants, such as water, TCPC stops toggling while reporting OPEN
either by the time TCPM reads CC pin status or during CC debounce
window. This causes TCPM to be stuck in TOGGLING state. If TCPM is made
to restart toggling, the behavior recurs causing redundant CPU wakeups
till the USB-C port is free of contaminant.

[206199.287817] CC1: 0 -> 0, CC2: 0 -> 0 [state TOGGLING, polarity 0, disconnected]
[206199.640337] CC1: 0 -> 0, CC2: 0 -> 0 [state TOGGLING, polarity 0, disconnected]
[206199.985789] CC1: 0 -> 0, CC2: 0 -> 0 [state TOGGLING, polarity 0, disconnected]

(or)

[ 7853.867577] Start toggling
[ 7853.889921] CC1: 0 -> 0, CC2: 0 -> 0 [state TOGGLING, polarity 0, disconnected]
[ 7855.698765] CC1: 0 -> 0, CC2: 0 -> 5 [state TOGGLING, polarity 0, connected]
[ 7855.698790] state change TOGGLING -> SNK_ATTACH_WAIT [rev3 NONE_AMS]
[ 7855.698826] pending state change SNK_ATTACH_WAIT -> SNK_DEBOUNCED @ 170 ms [rev3 NONE_AMS]
[ 7855.703559] CC1: 0 -> 0, CC2: 5 -> 5 [state SNK_ATTACH_WAIT, polarity 0, connected]
[ 7855.856555] CC1: 0 -> 0, CC2: 5 -> 0 [state SNK_ATTACH_WAIT, polarity 0, disconnected]
[ 7855.856581] state change SNK_ATTACH_WAIT -> SNK_ATTACH_WAIT [rev3 NONE_AMS]
[ 7855.856613] pending state change SNK_ATTACH_WAIT -> SNK_UNATTACHED @ 170 ms [rev3 NONE_AMS]
[ 7856.027744] state change SNK_ATTACH_WAIT -> SNK_UNATTACHED [delayed 170 ms]
[ 7856.181949] CC1: 0 -> 0, CC2: 0 -> 0 [state TOGGLING, polarity 0, disconnected]
[ 7856.187896] CC1: 0 -> 0, CC2: 0 -> 0 [state TOGGLING, polarity 0, disconnected]
[ 7857.645630] CC1: 0 -> 0, CC2: 0 -> 0 [state TOGGLING, polarity 0, disconnected]
[ 7857.647291] CC1: 0 -> 0, CC2: 0 -> 5 [state TOGGLING, polarity 0, connected]
[ 7857.647298] state change TOGGLING -> SNK_ATTACH_WAIT [rev3 NONE_AMS]
[ 7857.647310] pending state change SNK_ATTACH_WAIT -> SNK_DEBOUNCED @ 170 ms [rev3 NONE_AMS]
[ 7857.808106] CC1: 0 -> 0, CC2: 5 -> 0 [state SNK_ATTACH_WAIT, polarity 0, disconnected]
[ 7857.808123] state change SNK_ATTACH_WAIT -> SNK_ATTACH_WAIT [rev3 NONE_AMS]
[ 7857.808150] pending state change SNK_ATTACH_WAIT -> SNK_UNATTACHED @ 170 ms [rev3 NONE_AMS]
[ 7857.978727] state change SNK_ATTACH_WAIT -> SNK_UNATTACHED [delayed 170 ms]

To mitigate redundant TCPM wakeups, TCPCs which do have the needed hardware
can implement the check_contaminant callback which is invoked by TCPM
to evaluate for presence of contaminant. Lower level TCPC driver can
restart toggling through TCPM_PORT_CLEAN event when the driver detects
that USB-C port is free of contaminant. check_contaminant callback also
passes the disconnect_while_debounce flag which when true denotes that
the CC pins transitioned to OPEN state during the CC debounce window.

Signed-off-by: Badhri Jagan Sridharan <[e-mail]>
Acked-by: Heikki Krogerus <[e-mail]>
Link: https://lore.kernel.org/r/[e-mail]
Signed-off-by: Greg Kroah-Hartman <[e-mail]>

drivers/usb/typec/tcpm/tcpm.c

···
 #define FOREACH_STATE(S)			\
 	S(INVALID_STATE),			\
 	S(TOGGLING),			\
+	S(CHECK_CONTAMINANT),			\
 	S(SRC_UNATTACHED),			\
 	S(SRC_ATTACH_WAIT),			\
 	S(SRC_ATTACHED),			\
···
 #define TCPM_RESET_EVENT	BIT(2)
 #define TCPM_FRS_EVENT		BIT(3)
 #define TCPM_SOURCING_VBUS	BIT(4)
+#define TCPM_PORT_CLEAN		BIT(5)
 
 #define LOG_BUFFER_ENTRIES	1024
 #define LOG_BUFFER_ENTRY_SIZE	128
···
 	 * SNK_READY for non-pd link.
 	 */
 	bool slow_charger_loop;
+
+	/*
+	 * When true indicates that the lower level drivers indicate potential presence
+	 * of contaminant in the connector pins based on the tcpm state machine
+	 * transitions.
+	 */
+	bool potential_contaminant;
 #ifdef CONFIG_DEBUG_FS
 	struct dentry *dentry;
 	struct mutex logbuffer_lock;	/* log buffer access lock */
···
 	/* Do not log while disconnected and unattached */
 	if (tcpm_port_is_disconnected(port) &&
 	    (port->state == SRC_UNATTACHED || port->state == SNK_UNATTACHED ||
-	     port->state == TOGGLING))
+	     port->state == TOGGLING || port->state == CHECK_CONTAMINANT))
 		return;
 
 	va_start(args, fmt);
···
 	unsigned int msecs;
 	enum tcpm_state upcoming_state;
 
+	if (port->tcpc->check_contaminant && port->state != CHECK_CONTAMINANT)
+		port->potential_contaminant = ((port->enter_state == SRC_ATTACH_WAIT &&
+						port->state == SRC_UNATTACHED) ||
+					       (port->enter_state == SNK_ATTACH_WAIT &&
+						port->state == SNK_UNATTACHED));
+
 	port->enter_state = port->state;
 	switch (port->state) {
 	case TOGGLING:
+		break;
+	case CHECK_CONTAMINANT:
+		port->tcpc->check_contaminant(port->tcpc);
 		break;
 	/* SRC states */
 	case SRC_UNATTACHED:
 		if (!port->non_pd_role_swap)
 			tcpm_swap_complete(port, -ENOTCONN);
 		tcpm_src_detach(port);
+		if (port->potential_contaminant) {
+			tcpm_set_state(port, CHECK_CONTAMINANT, 0);
+			break;
+		}
 		if (tcpm_start_toggling(port, tcpm_rp_cc(port))) {
 			tcpm_set_state(port, TOGGLING, 0);
 			break;
···
 			tcpm_swap_complete(port, -ENOTCONN);
 		tcpm_pps_complete(port, -ENOTCONN);
 		tcpm_snk_detach(port);
+		if (port->potential_contaminant) {
+			tcpm_set_state(port, CHECK_CONTAMINANT, 0);
+			break;
+		}
 		if (tcpm_start_toggling(port, TYPEC_CC_RD)) {
 			tcpm_set_state(port, TOGGLING, 0);
 			break;
···
 		else if (tcpm_port_is_sink(port))
 			tcpm_set_state(port, SNK_ATTACH_WAIT, 0);
 		break;
+	case CHECK_CONTAMINANT:
+		/* Wait for Toggling to be resumed */
+		break;
 	case SRC_UNATTACHED:
 	case ACC_UNATTACHED:
 		if (tcpm_port_is_debug(port) || tcpm_port_is_audio(port) ||
···
 			port->vbus_source = true;
 			_tcpm_pd_vbus_on(port);
 		}
+		if (events & TCPM_PORT_CLEAN) {
+			tcpm_log(port, "port clean");
+			if (port->state == CHECK_CONTAMINANT) {
+				if (tcpm_start_toggling(port, tcpm_rp_cc(port)))
+					tcpm_set_state(port, TOGGLING, 0);
+				else
+					tcpm_set_state(port, tcpm_default_state(port), 0);
+			}
+		}
 
 		spin_lock(&port->pd_event_lock);
 	}
···
 	kthread_queue_work(port->wq, &port->event_work);
 }
 EXPORT_SYMBOL_GPL(tcpm_sourcing_vbus);
+
+void tcpm_port_clean(struct tcpm_port *port)
+{
+	spin_lock(&port->pd_event_lock);
+	port->pd_events |= TCPM_PORT_CLEAN;
+	spin_unlock(&port->pd_event_lock);
+	kthread_queue_work(port->wq, &port->event_work);
+}
+EXPORT_SYMBOL_GPL(tcpm_port_clean);
+
+bool tcpm_port_is_toggling(struct tcpm_port *port)
+{
+	return port->port_type == TYPEC_PORT_DRP && port->state == TOGGLING;
+}
+EXPORT_SYMBOL_GPL(tcpm_port_is_toggling);
 
 static void tcpm_enable_frs_work(struct kthread_work *work)
 {

include/linux/usb/tcpm.h

···
  *              Optional; The USB Communications Capable bit indicates if port
  *              partner is capable of communication over the USB data lines
  *              (e.g. D+/- or SS Tx/Rx). Called to notify the status of the bit.
+ * @check_contaminant:
+ *		Optional; The callback is called when CC pins report open status
+ *		at the end of the deboumce period or when the port is still
+ *		toggling. Chip level drivers are expected to check for contaminant
+ *		and call tcpm_clean_port when the port is clean.
  */
 struct tcpc_dev {
 	struct fwnode_handle *fwnode;
···
 						 bool pps_active, u32 requested_vbus_voltage);
 	bool (*is_vbus_vsafe0v)(struct tcpc_dev *dev);
 	void (*set_partner_usb_comm_capable)(struct tcpc_dev *dev, bool enable);
+	void (*check_contaminant)(struct tcpc_dev *dev);
 };
 
 struct tcpm_port;
···
 			       enum tcpm_transmit_status status);
 void tcpm_pd_hard_reset(struct tcpm_port *port);
 void tcpm_tcpc_reset(struct tcpm_port *port);
+void tcpm_port_clean(struct tcpm_port *port);
+bool tcpm_port_is_toggling(struct tcpm_port *port);
 
 #endif /* __LINUX_USB_TCPM_H */