[PATCH 5.12 026/700] usb: typec: tcpm: Relax disconnect threshold during power negotiation

[Greg Kroah-Hartman]

From: Kyle Tso <kyletso@xxxxxxxxxx>

commit 2b537cf877eae6d2f2f102052290676e40b74a1d upstream.

If the voltage is being decreased in power negotiation, the Source will
set the power supply to operate at the new voltage level before sending
PS_RDY. Relax the threshold before sending Request Message so that it
will not race with Source which begins to adjust the voltage right after
it sends Accept Message (PPS) or tSrcTransition (25~35ms) after it sends
Accept Message (non-PPS).

The real threshold will be set after Sink receives PS_RDY Message.

Fixes: f321a02caebd ("usb: typec: tcpm: Implement enabling Auto Discharge disconnect support")
Cc: stable <stable@xxxxxxxxxxxxxxx>
Cc: Badhri Jagan Sridharan <badhri@xxxxxxxxxx>
Reviewed-by: Badhri Jagan Sridharan <badhri@xxxxxxxxxx>
Acked-by: Heikki Krogerus <heikki.krogerus@xxxxxxxxxxxxxxx>
Signed-off-by: Kyle Tso <kyletso@xxxxxxxxxx>
Link: https://lore.kernel.org/r/20210616090102.1897674-1-kyletso@xxxxxxxxxx
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>

---
 drivers/usb/typec/tcpm/tcpm.c |   27 +++++++++++++++++++++++++++
 1 file changed, 27 insertions(+)

--- a/drivers/usb/typec/tcpm/tcpm.c
+++ b/drivers/usb/typec/tcpm/tcpm.c
@@ -2556,6 +2556,11 @@ static void tcpm_pd_ctrl_request(struct
 			} else {
 				next_state = SNK_WAIT_CAPABILITIES;
 			}
+
+			/* Threshold was relaxed before sending Request. Restore it back. */
+			tcpm_set_auto_vbus_discharge_threshold(port, TYPEC_PWR_MODE_PD,
+							       port->pps_data.active,
+							       port->supply_voltage);
 			tcpm_set_state(port, next_state, 0);
 			break;
 		case SNK_NEGOTIATE_PPS_CAPABILITIES:
@@ -2569,6 +2574,11 @@ static void tcpm_pd_ctrl_request(struct
 			    port->send_discover)
 				port->vdm_sm_running = true;
 
+			/* Threshold was relaxed before sending Request. Restore it back. */
+			tcpm_set_auto_vbus_discharge_threshold(port, TYPEC_PWR_MODE_PD,
+							       port->pps_data.active,
+							       port->supply_voltage);
+
 			tcpm_set_state(port, SNK_READY, 0);
 			break;
 		case DR_SWAP_SEND:
@@ -3288,6 +3298,12 @@ static int tcpm_pd_send_request(struct t
 	if (ret < 0)
 		return ret;
 
+	/*
+	 * Relax the threshold as voltage will be adjusted after Accept Message plus tSrcTransition.
+	 * It is safer to modify the threshold here.
+	 */
+	tcpm_set_auto_vbus_discharge_threshold(port, TYPEC_PWR_MODE_USB, false, 0);
+
 	memset(&msg, 0, sizeof(msg));
 	msg.header = PD_HEADER_LE(PD_DATA_REQUEST,
 				  port->pwr_role,
@@ -3385,6 +3401,9 @@ static int tcpm_pd_send_pps_request(stru
 	if (ret < 0)
 		return ret;
 
+	/* Relax the threshold as voltage will be adjusted right after Accept Message. */
+	tcpm_set_auto_vbus_discharge_threshold(port, TYPEC_PWR_MODE_USB, false, 0);
+
 	memset(&msg, 0, sizeof(msg));
 	msg.header = PD_HEADER_LE(PD_DATA_REQUEST,
 				  port->pwr_role,
@@ -4161,6 +4180,10 @@ static void run_state_machine(struct tcp
 		port->hard_reset_count = 0;
 		ret = tcpm_pd_send_request(port);
 		if (ret < 0) {
+			/* Restore back to the original state */
+			tcpm_set_auto_vbus_discharge_threshold(port, TYPEC_PWR_MODE_PD,
+							       port->pps_data.active,
+							       port->supply_voltage);
 			/* Let the Source send capabilities again. */
 			tcpm_set_state(port, SNK_WAIT_CAPABILITIES, 0);
 		} else {
@@ -4171,6 +4194,10 @@ static void run_state_machine(struct tcp
 	case SNK_NEGOTIATE_PPS_CAPABILITIES:
 		ret = tcpm_pd_send_pps_request(port);
 		if (ret < 0) {
+			/* Restore back to the original state */
+			tcpm_set_auto_vbus_discharge_threshold(port, TYPEC_PWR_MODE_PD,
+							       port->pps_data.active,
+							       port->supply_voltage);
 			port->pps_status = ret;
 			/*
 			 * If this was called due to updates to sink