usb: typec: tcpci_maxim: Add support for Sink FRS

Upon receiving ALERT_EXTENDED.TCPC_SINK_FAST_ROLE_SWAP signal
tcpm to start Sink fast role swap signal.

Inform when TCPM is sourcing vbus.

Signed-off-by: Badhri Jagan Sridharan <badhri@google.com>
Reviewed-by: Heikki Krogerus <heikki.krogerus@linux.intel.com>
Link: https://lore.kernel.org/r/20201008061556.1402293-9-badhri@google.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/usb/typec/tcpm/tcpci_maxim.c

@@ -106,13 +106,22 @@ static void max_tcpci_init_regs(struct max_tcpci_chip *chip)
 		return;
 	}
 
+	ret = max_tcpci_write8(chip, TCPC_ALERT_EXTENDED, 0xff);
+	if (ret < 0) {
+		dev_err(chip->dev, "Unable to clear TCPC_ALERT_EXTENDED ret:%d\n", ret);
+		return;
+	}
+
 	alert_mask = TCPC_ALERT_TX_SUCCESS | TCPC_ALERT_TX_DISCARDED | TCPC_ALERT_TX_FAILED |
 		TCPC_ALERT_RX_HARD_RST | TCPC_ALERT_RX_STATUS | TCPC_ALERT_CC_STATUS |
-		TCPC_ALERT_VBUS_DISCNCT | TCPC_ALERT_RX_BUF_OVF | TCPC_ALERT_POWER_STATUS;
+		TCPC_ALERT_VBUS_DISCNCT | TCPC_ALERT_RX_BUF_OVF | TCPC_ALERT_POWER_STATUS |
+		/* Enable Extended alert for detecting Fast Role Swap Signal */
+		TCPC_ALERT_EXTND;
 
 	ret = max_tcpci_write16(chip, TCPC_ALERT_MASK, alert_mask);
 	if (ret < 0) {
-		dev_err(chip->dev, "Error writing to TCPC_ALERT_MASK ret:%d\n", ret);
+		dev_err(chip->dev,
+			"Error enabling TCPC_ALERT: TCPC_ALERT_MASK write failed ret:%d\n", ret);
 		return;
 	}
 
@@ -122,6 +131,10 @@ static void max_tcpci_init_regs(struct max_tcpci_chip *chip)
 		dev_err(chip->dev, "Error writing to TCPC_POWER_CTRL ret:%d\n", ret);
 		return;
 	}
+
+	ret = max_tcpci_write8(chip, TCPC_ALERT_EXTENDED_MASK, TCPC_SINK_FAST_ROLE_SWAP);
+	if (ret < 0)
+		return;
 }
 
 static void process_rx(struct max_tcpci_chip *chip, u16 status)
@@ -225,10 +238,23 @@ static void process_power_status(struct max_tcpci_chip *chip)
 	if (ret < 0)
 		return;
 
-	if (pwr_status == 0xff)
+	if (pwr_status == 0xff) {
 		max_tcpci_init_regs(chip);
-	else
+	} else if (pwr_status & TCPC_POWER_STATUS_SOURCING_VBUS) {
+		tcpm_sourcing_vbus(chip->port);
+		/*
+		 * Alawys re-enable boost here.
+		 * In normal case, when say an headset is attached, TCPM would
+		 * have instructed to TCPC to enable boost, so the call is a
+		 * no-op.
+		 * But for Fast Role Swap case, Boost turns on autonomously without
+		 * AP intervention, but, needs AP to enable source mode explicitly
+		 * for AP to regain control.
+		 */
+		max_tcpci_set_vbus(chip->tcpci, &chip->data, true, false);
+	} else {
 		tcpm_vbus_change(chip->port);
+	}
 }
 
 static void process_tx(struct max_tcpci_chip *chip, u16 status)
@@ -249,6 +275,7 @@ static irqreturn_t _max_tcpci_irq(struct max_tcpci_chip *chip, u16 status)
 {
 	u16 mask;
 	int ret;
+	u8 reg_status;
 
 	/*
 	 * Clear alert status for everything except RX_STATUS, which shouldn't
@@ -274,6 +301,21 @@ static irqreturn_t _max_tcpci_irq(struct max_tcpci_chip *chip, u16 status)
 		}
 	}
 
+	if (status & TCPC_ALERT_EXTND) {
+		ret = max_tcpci_read8(chip, TCPC_ALERT_EXTENDED, &reg_status);
+		if (ret < 0)
+			return ret;
+
+		ret = max_tcpci_write8(chip, TCPC_ALERT_EXTENDED, reg_status);
+		if (ret < 0)
+			return ret;
+
+		if (reg_status & TCPC_SINK_FAST_ROLE_SWAP) {
+			dev_info(chip->dev, "FRS Signal");
+			tcpm_sink_frs(chip->port);
+		}
+	}
+
 	if (status & TCPC_ALERT_RX_STATUS)
 		process_rx(chip, status);