usb: typec: tcpci: Fix up sink disconnect thresholds for PD

"Table 4-3 VBUS Sink Characteristics" of "Type-C Cable and Connector
Specification" defines the disconnect voltage thresholds of various
configurations. This change fixes the disconnect threshold voltage
calculation based on vSinkPD_min and vSinkDisconnectPD as defined
by the table.

Fixes: e1a97bf8 ("usb: typec: tcpci: Implement Auto discharge disconnect callbacks")
Cc: stable <stable@vger.kernel.org>
Acked-by: Heikki Krogerus <heikki.krogerus@linux.intel.com>
Signed-off-by: Badhri Jagan Sridharan <badhri@google.com>
Link: https://lore.kernel.org/r/20210615174323.1160132-1-badhri@google.comSigned-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/usb/typec/tcpm/tcpci.c

@@ -21,8 +21,12 @@
 #define	PD_RETRY_COUNT_DEFAULT			3
 #define	PD_RETRY_COUNT_3_0_OR_HIGHER		2
 #define	AUTO_DISCHARGE_DEFAULT_THRESHOLD_MV	3500
-#define	AUTO_DISCHARGE_PD_HEADROOM_MV		850
-#define	AUTO_DISCHARGE_PPS_HEADROOM_MV		1250
+#define	VSINKPD_MIN_IR_DROP_MV			750
+#define	VSRC_NEW_MIN_PERCENT			95
+#define	VSRC_VALID_MIN_MV			500
+#define	VPPS_NEW_MIN_PERCENT			95
+#define	VPPS_VALID_MIN_MV			100
+#define	VSINKDISCONNECT_PD_MIN_PERCENT		90
 
 #define tcpc_presenting_rd(reg, cc) \
 	(!(TCPC_ROLE_CTRL_DRP & (reg)) && \
@@ -351,11 +355,13 @@ static int tcpci_set_auto_vbus_discharge_threshold(struct tcpc_dev *dev, enum ty
 		threshold = AUTO_DISCHARGE_DEFAULT_THRESHOLD_MV;
 	} else if (mode == TYPEC_PWR_MODE_PD) {
 		if (pps_active)
-			threshold = (95 * requested_vbus_voltage_mv / 100) -
-				AUTO_DISCHARGE_PD_HEADROOM_MV;
+			threshold = ((VPPS_NEW_MIN_PERCENT * requested_vbus_voltage_mv / 100) -
+				     VSINKPD_MIN_IR_DROP_MV - VPPS_VALID_MIN_MV) *
+				     VSINKDISCONNECT_PD_MIN_PERCENT / 100;
 		else
-			threshold = (95 * requested_vbus_voltage_mv / 100) -
-				AUTO_DISCHARGE_PPS_HEADROOM_MV;
+			threshold = ((VSRC_NEW_MIN_PERCENT * requested_vbus_voltage_mv / 100) -
+				     VSINKPD_MIN_IR_DROP_MV - VSRC_VALID_MIN_MV) *
+				     VSINKDISCONNECT_PD_MIN_PERCENT / 100;
 	} else {
 		/* 3.5V for non-pd sink */
 		threshold = AUTO_DISCHARGE_DEFAULT_THRESHOLD_MV;