usb: typec: tcpci: add attempt_vconn_swap_discovery callback

Add attempt_vconn_swap_discovery callback to determine whether the TCPM
should perform a Vconn swap following Discover Identity on SOP. The tcpci
will return false unless chip level drivers implement the callback.

Maxim based TCPCs will return true unless the last connection resulted in
a Vconn Over Current Fault, which may be the result of the Vconn swap. In
addition to the port resetting, the TCPCI will veto the next Vconn swap
from occurring.
Signed-off-by: RD Babiera <rdbabiera@google.com>
Reviewed-by: Heikki Krogerus <heikki.krogerus@linux.intel.com>
Link: https://lore.kernel.org/r/20240108191620.987785-21-rdbabiera@google.comSigned-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/usb/typec/tcpm/tcpci.c

@@ -594,6 +594,16 @@ static bool tcpci_cable_comm_capable(struct tcpc_dev *tcpc)
 	return tcpci->data->cable_comm_capable;
 }
 
+static bool tcpci_attempt_vconn_swap_discovery(struct tcpc_dev *tcpc)
+{
+	struct tcpci *tcpci = tcpc_to_tcpci(tcpc);
+
+	if (tcpci->data->attempt_vconn_swap_discovery)
+		return tcpci->data->attempt_vconn_swap_discovery(tcpci, tcpci->data);
+
+	return false;
+}
+
 static int tcpci_init(struct tcpc_dev *tcpc)
 {
 	struct tcpci *tcpci = tcpc_to_tcpci(tcpc);
@@ -804,6 +814,7 @@ struct tcpci *tcpci_register_port(struct device *dev, struct tcpci_data *data)
 	tcpci->tcpc.frs_sourcing_vbus = tcpci_frs_sourcing_vbus;
 	tcpci->tcpc.set_partner_usb_comm_capable = tcpci_set_partner_usb_comm_capable;
 	tcpci->tcpc.cable_comm_capable = tcpci_cable_comm_capable;
+	tcpci->tcpc.attempt_vconn_swap_discovery = tcpci_attempt_vconn_swap_discovery;
 
 	if (tcpci->data->check_contaminant)
 		tcpci->tcpc.check_contaminant = tcpci_check_contaminant;

drivers/usb/typec/tcpm/tcpci_maxim.h

@@ -62,6 +62,7 @@ struct max_tcpci_chip {
 	struct i2c_client *client;
 	struct tcpm_port *port;
 	enum contamiant_state contaminant_state;
+	bool veto_vconn_swap;
 };
 
 static inline int max_tcpci_read16(struct max_tcpci_chip *chip, unsigned int reg, u16 *val)

drivers/usb/typec/tcpm/tcpci_maxim_core.c

@@ -323,8 +323,10 @@ static irqreturn_t _max_tcpci_irq(struct max_tcpci_chip *chip, u16 status)
 		if (ret < 0)
 			return ret;
 
-		if (reg_status & TCPC_FAULT_STATUS_VCONN_OC)
+		if (reg_status & TCPC_FAULT_STATUS_VCONN_OC) {
+			chip->veto_vconn_swap = true;
 			tcpm_port_error_recovery(chip->port);
+		}
 	}
 
 	if (status & TCPC_ALERT_EXTND) {
@@ -458,6 +460,18 @@ static void max_tcpci_check_contaminant(struct tcpci *tcpci, struct tcpci_data *
 		tcpm_port_clean(chip->port);
 }
 
+static bool max_tcpci_attempt_vconn_swap_discovery(struct tcpci *tcpci, struct tcpci_data *tdata)
+{
+	struct max_tcpci_chip *chip = tdata_to_max_tcpci(tdata);
+
+	if (chip->veto_vconn_swap) {
+		chip->veto_vconn_swap = false;
+		return false;
+	}
+
+	return true;
+}
+
 static int max_tcpci_probe(struct i2c_client *client)
 {
 	int ret;
@@ -493,6 +507,7 @@ static int max_tcpci_probe(struct i2c_client *client)
 	chip->data.set_partner_usb_comm_capable = max_tcpci_set_partner_usb_comm_capable;
 	chip->data.check_contaminant = max_tcpci_check_contaminant;
 	chip->data.cable_comm_capable = true;
+	chip->data.attempt_vconn_swap_discovery = max_tcpci_attempt_vconn_swap_discovery;
 
 	max_tcpci_init_regs(chip);
 	chip->tcpci = tcpci_register_port(chip->dev, &chip->data);

include/linux/usb/tcpci.h

@@ -201,6 +201,14 @@ struct tcpci;
  *		toggling state.
  * @cable_comm_capable
  *		optional; Set when TCPC can communicate with cable plugs over SOP'
+ * @attempt_vconn_swap_discovery:
+ *		Optional; The callback is called by the TCPM when the result of
+ *		a Discover Identity request indicates that the port partner is
+ *		a receptacle capable of modal operation. Chip level TCPCI drivers
+ *		can implement their own policy to determine if and when a Vconn
+ *		swap following Discover Identity on SOP' occurs.
+ *		Return true when the TCPM is allowed to request a Vconn swap
+ *		after Discovery Identity on SOP.
  */
 struct tcpci_data {
 	struct regmap *regmap;
@@ -219,6 +227,7 @@ struct tcpci_data {
 	void (*set_partner_usb_comm_capable)(struct tcpci *tcpci, struct tcpci_data *data,
 					     bool capable);
 	void (*check_contaminant)(struct tcpci *tcpci, struct tcpci_data *data);
+	bool (*attempt_vconn_swap_discovery)(struct tcpci *tcpci, struct tcpci_data *data);
 };
 
 struct tcpci *tcpci_register_port(struct device *dev, struct tcpci_data *data);

include/linux/usb/tcpm.h

@@ -122,6 +122,14 @@ enum tcpm_transmit_type {
  * @cable_comm_capable
  *		Optional; Returns whether cable communication over SOP' is supported
  *		by the tcpc
+ * @attempt_vconn_swap_discovery:
+ *		Optional; The callback is called by the TCPM when the result of
+ *		a Discover Identity request indicates that the port partner is
+ *		a receptacle capable of modal operation. Chip level TCPCI drivers
+ *		can implement their own policy to determine if and when a Vconn
+ *		swap following Discover Identity on SOP' occurs.
+ *		Return true when the TCPM is allowed to request a Vconn swap
+ *		after Discovery Identity on SOP.
  */
 struct tcpc_dev {
 	struct fwnode_handle *fwnode;
@@ -158,6 +166,7 @@ struct tcpc_dev {
 	void (*set_partner_usb_comm_capable)(struct tcpc_dev *dev, bool enable);
 	void (*check_contaminant)(struct tcpc_dev *dev);
 	bool (*cable_comm_capable)(struct tcpc_dev *dev);
+	bool (*attempt_vconn_swap_discovery)(struct tcpc_dev *dev);
 };
 
 struct tcpm_port;