usb: typec: tcpm/tcpci_maxim: fix non-contaminant CC handling

tcpci_maxim currently never triggers the TCPM state machine when CC
status has not changed due to a contaminant but due to a real
connection event, i.e. a genuine plug event, meaning the system will
stay idle and not notify any subscribers.

The reason is that the initial state of the port is 'toggling', which
causes _max_tcpci_irq() to only drive the contamination part of the
TCPM state machine (via tcpm_port_clean()).

What should happen instead is that if no contamination was detected,
the TCPM should be notified of the CC change in this case.

To fix this, we update ...is_contaminant() to also allow its caller to
determine if more CC processing is required and then call into the TCPM
as required.

While at it, add a kernel-doc for max_contaminant_is_contaminant().

Note: the code has an issue where I2C errors during contaminant
detection also cause the TCPM state machine to not be updated. This
commit doesn't change this behaviour and should be addressed by
follow-up commit(s).

Signed-off-by: André Draszik <andre.draszik@linaro.org>
Reviewed-by: Heikki Krogerus <heikki.krogerus@linux.intel.com>
Link: https://lore.kernel.org/r/20240806-max33359-toggling-v2-1-a66ab37baafb@linaro.org
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

3 files changed, 27 insertions, 7 deletions

diff --git a/drivers/usb/typec/tcpm/maxim_contaminant.c b/drivers/usb/typec/tcpm/maxim_contaminant.c
index 7bfec45e8f4f..22163d8f9eb0 100644
--- a/drivers/usb/typec/tcpm/maxim_contaminant.c
+++ b/drivers/usb/typec/tcpm/maxim_contaminant.c
@@ -324,11 +324,14 @@ static int max_contaminant_enable_dry_detection(struct max_tcpci_chip *chip)
 	return 0;
 }
 
-bool max_contaminant_is_contaminant(struct max_tcpci_chip *chip, bool disconnect_while_debounce)
+bool max_contaminant_is_contaminant(struct max_tcpci_chip *chip, bool disconnect_while_debounce,
+				    bool *cc_handled)
 {
 	u8 cc_status, pwr_cntl;
 	int ret;
 
+	*cc_handled = true;
+
 	ret = max_tcpci_read8(chip, TCPC_CC_STATUS, &cc_status);
 	if (ret < 0)
 		return false;
@@ -370,7 +373,6 @@ bool max_contaminant_is_contaminant(struct max_tcpci_chip *chip, bool disconnect
 				return true;
 			}
 		}
-		return false;
 	} else if (chip->contaminant_state == DETECTED) {
 		if (!(cc_status & TCPC_CC_STATUS_TOGGLING)) {
 			chip->contaminant_state = max_contaminant_detect_contaminant(chip);
@@ -381,6 +383,7 @@ bool max_contaminant_is_contaminant(struct max_tcpci_chip *chip, bool disconnect
 		}
 	}
 
+	*cc_handled = false;
 	return false;
 }
 
diff --git a/drivers/usb/typec/tcpm/tcpci_maxim.h b/drivers/usb/typec/tcpm/tcpci_maxim.h
index a41ca9e7ad08..76270d5c2838 100644
--- a/drivers/usb/typec/tcpm/tcpci_maxim.h
+++ b/drivers/usb/typec/tcpm/tcpci_maxim.h
@@ -81,6 +81,20 @@ static inline int max_tcpci_write8(struct max_tcpci_chip *chip, unsigned int reg
 	return regmap_raw_write(chip->data.regmap, reg, &val, sizeof(u8));
 }
 
-bool max_contaminant_is_contaminant(struct max_tcpci_chip *chip, bool disconnect_while_debounce);
+/**
+ * max_contaminant_is_contaminant - Test if CC was toggled due to contaminant
+ *
+ * @chip: Handle to a struct max_tcpci_chip
+ * @disconnect_while_debounce: Whether the disconnect was detected when CC
+ *      		       pins were debouncing
+ * @cc_handled: Returns whether or not update to CC status was handled here
+ *
+ * Determine if a contaminant was detected.
+ *
+ * Returns: true if a contaminant was detected, false otherwise. cc_handled
+ * is updated to reflect whether or not further CC handling is required.
+ */
+bool max_contaminant_is_contaminant(struct max_tcpci_chip *chip, bool disconnect_while_debounce,
+				    bool *cc_handled);
 
 #endif  // TCPCI_MAXIM_H_
diff --git a/drivers/usb/typec/tcpm/tcpci_maxim_core.c b/drivers/usb/typec/tcpm/tcpci_maxim_core.c
index 1584ab2983be..fd1b80593367 100644
--- a/drivers/usb/typec/tcpm/tcpci_maxim_core.c
+++ b/drivers/usb/typec/tcpm/tcpci_maxim_core.c
@@ -357,12 +357,14 @@ static irqreturn_t _max_tcpci_irq(struct max_tcpci_chip *chip, u16 status)
 		tcpm_vbus_change(chip->port);
 
 	if (status & TCPC_ALERT_CC_STATUS) {
+		bool cc_handled = false;
+
 		if (chip->contaminant_state == DETECTED || tcpm_port_is_toggling(chip->port)) {
-			if (!max_contaminant_is_contaminant(chip, false))
+			if (!max_contaminant_is_contaminant(chip, false, &cc_handled))
 				tcpm_port_clean(chip->port);
-		} else {
-			tcpm_cc_change(chip->port);
 		}
+		if (!cc_handled)
+			tcpm_cc_change(chip->port);
 	}
 
 	if (status & TCPC_ALERT_POWER_STATUS)
@@ -455,8 +457,9 @@ static int tcpci_init(struct tcpci *tcpci, struct tcpci_data *data)
 static void max_tcpci_check_contaminant(struct tcpci *tcpci, struct tcpci_data *tdata)
 {
 	struct max_tcpci_chip *chip = tdata_to_max_tcpci(tdata);
+	bool cc_handled;
 
-	if (!max_contaminant_is_contaminant(chip, true))
+	if (!max_contaminant_is_contaminant(chip, true, &cc_handled))
 		tcpm_port_clean(chip->port);
 }