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Date: Thu, 14 Dec 2023 23:08:51 +0000
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Subject: [PATCH v2 07/12] usb: typec: tcpci: add attempt_vconn_swap_discovery callback
From: RD Babiera <rdbabiera@google.com>
To: rdbabiera@google.com, heikki.krogerus@linux.intel.com, linux@roeck-us.net, 
	gregkh@linuxfoundation.org, linux-kernel@vger.kernel.org, 
	linux-usb@vger.kernel.org
Cc: badhri@google.com, bryan.odonoghue@linaro.org, agross@kernel.org, 
	andersson@kernel.org, konrad.dybcio@linaro.org
Content-Type: text/plain; charset="UTF-8"

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>
---
 drivers/usb/typec/tcpm/tcpci.c            | 11 +++++++++++
 drivers/usb/typec/tcpm/tcpci_maxim.h      |  1 +
 drivers/usb/typec/tcpm/tcpci_maxim_core.c | 17 ++++++++++++++++-
 include/linux/usb/tcpci.h                 |  9 +++++++++
 include/linux/usb/tcpm.h                  |  9 +++++++++
 5 files changed, 46 insertions(+), 1 deletion(-)

diff --git a/drivers/usb/typec/tcpm/tcpci.c b/drivers/usb/typec/tcpm/tcpci.c
index 8ea4ed159a13..40c7b6224c74 100644
--- a/drivers/usb/typec/tcpm/tcpci.c
+++ b/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;
diff --git a/drivers/usb/typec/tcpm/tcpci_maxim.h b/drivers/usb/typec/tcpm/tcpci_maxim.h
index 2c1c4d161b0d..78ff3b73ee7e 100644
--- a/drivers/usb/typec/tcpm/tcpci_maxim.h
+++ b/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)
diff --git a/drivers/usb/typec/tcpm/tcpci_maxim_core.c b/drivers/usb/typec/tcpm/tcpci_maxim_core.c
index f9f838df43f7..eec3bcec119c 100644
--- a/drivers/usb/typec/tcpm/tcpci_maxim_core.c
+++ b/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);
diff --git a/include/linux/usb/tcpci.h b/include/linux/usb/tcpci.h
index 9ed6d62c9c5f..47a86b8a4a50 100644
--- a/include/linux/usb/tcpci.h
+++ b/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);
diff --git a/include/linux/usb/tcpm.h b/include/linux/usb/tcpm.h
index 41d1ac9c8bbf..6671427f7eeb 100644
--- a/include/linux/usb/tcpm.h
+++ b/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;
-- 
2.43.0.472.g3155946c3a-goog