usb: typec: tcpci: Implement Auto discharge disconnect callbacks

vImplement callbacks for enabling/disabling
POWER_CONTROL.AutoDischargeDisconnect.

Programs VBUS_SINK_DISCONNECT_THRESHOLD based on the
voltage requested as sink, mode of operation.

The programmed threshold is based on vSinkDisconnect and
vSinkDisconnectPD values.

Add auto_discharge_disconnect to tdata to allow TCPC chip
level drivers enable AutoDischargeDisconnect.

Signed-off-by: Badhri Jagan Sridharan <badhri@google.com>
Reviewed-by: Heikki Krogerus <heikki.krogerus@linux.intel.com>
Link: https://lore.kernel.org/r/20201029063138.1429760-9-badhri@google.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/usb/typec/tcpm/tcpci.c

@@ -19,6 +19,9 @@
 #include "tcpci.h"
 
 #define	PD_RETRY_COUNT				3
+#define	AUTO_DISCHARGE_DEFAULT_THRESHOLD_MV	3500
+#define	AUTO_DISCHARGE_PD_HEADROOM_MV		850
+#define	AUTO_DISCHARGE_PPS_HEADROOM_MV		1250
 
 struct tcpci {
 	struct device *dev;
@@ -268,6 +271,58 @@ static int tcpci_set_vconn(struct tcpc_dev *tcpc, bool enable)
 				enable ? TCPC_POWER_CTRL_VCONN_ENABLE : 0);
 }
 
+static int tcpci_enable_auto_vbus_discharge(struct tcpc_dev *dev, bool enable)
+{
+	struct tcpci *tcpci = tcpc_to_tcpci(dev);
+	int ret;
+
+	ret = regmap_update_bits(tcpci->regmap, TCPC_POWER_CTRL, TCPC_POWER_CTRL_AUTO_DISCHARGE,
+				 enable ? TCPC_POWER_CTRL_AUTO_DISCHARGE : 0);
+	return ret;
+}
+
+static int tcpci_set_auto_vbus_discharge_threshold(struct tcpc_dev *dev, enum typec_pwr_opmode mode,
+						   bool pps_active, u32 requested_vbus_voltage_mv)
+{
+	struct tcpci *tcpci = tcpc_to_tcpci(dev);
+	unsigned int pwr_ctrl, threshold = 0;
+	int ret;
+
+	/*
+	 * Indicates that vbus is going to go away due PR_SWAP, hard reset etc.
+	 * Do not discharge vbus here.
+	 */
+	if (requested_vbus_voltage_mv == 0)
+		goto write_thresh;
+
+	ret = regmap_read(tcpci->regmap, TCPC_POWER_CTRL, &pwr_ctrl);
+	if (ret < 0)
+		return ret;
+
+	if (pwr_ctrl & TCPC_FAST_ROLE_SWAP_EN) {
+		/* To prevent disconnect when the source is fast role swap is capable. */
+		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;
+		else
+			threshold = (95 * requested_vbus_voltage_mv / 100) -
+				AUTO_DISCHARGE_PPS_HEADROOM_MV;
+	} else {
+		/* 3.5V for non-pd sink */
+		threshold = AUTO_DISCHARGE_DEFAULT_THRESHOLD_MV;
+	}
+
+	threshold = threshold / TCPC_VBUS_SINK_DISCONNECT_THRESH_LSB_MV;
+
+	if (threshold > TCPC_VBUS_SINK_DISCONNECT_THRESH_MAX)
+		return -EINVAL;
+
+write_thresh:
+	return tcpci_write16(tcpci, TCPC_VBUS_SINK_DISCONNECT_THRESH, threshold);
+}
+
 static int tcpci_enable_frs(struct tcpc_dev *dev, bool enable)
 {
 	struct tcpci *tcpci = tcpc_to_tcpci(dev);
@@ -638,6 +693,12 @@ struct tcpci *tcpci_register_port(struct device *dev, struct tcpci_data *data)
 	tcpci->tcpc.enable_frs = tcpci_enable_frs;
 	tcpci->tcpc.frs_sourcing_vbus = tcpci_frs_sourcing_vbus;
 
+	if (tcpci->data->auto_discharge_disconnect) {
+		tcpci->tcpc.enable_auto_vbus_discharge = tcpci_enable_auto_vbus_discharge;
+		tcpci->tcpc.set_auto_vbus_discharge_threshold =
+			tcpci_set_auto_vbus_discharge_threshold;
+	}
+
 	err = tcpci_parse_config(tcpci);
 	if (err < 0)
 		return ERR_PTR(err);

drivers/usb/typec/tcpm/tcpci.h

@@ -8,6 +8,8 @@
 #ifndef __LINUX_USB_TCPCI_H
 #define __LINUX_USB_TCPCI_H
 
+#include <linux/usb/typec.h>
+
 #define TCPC_VENDOR_ID			0x0
 #define TCPC_PRODUCT_ID			0x2
 #define TCPC_BCD_DEV			0x4
@@ -67,6 +69,7 @@
 
 #define TCPC_POWER_CTRL			0x1c
 #define TCPC_POWER_CTRL_VCONN_ENABLE	BIT(0)
+#define TCPC_POWER_CTRL_AUTO_DISCHARGE	BIT(4)
 #define TCPC_FAST_ROLE_SWAP_EN		BIT(7)
 
 #define TCPC_CC_STATUS			0x1d
@@ -133,6 +136,8 @@
 
 #define TCPC_VBUS_VOLTAGE			0x70
 #define TCPC_VBUS_SINK_DISCONNECT_THRESH	0x72
+#define TCPC_VBUS_SINK_DISCONNECT_THRESH_LSB_MV	25
+#define TCPC_VBUS_SINK_DISCONNECT_THRESH_MAX	0x3ff
 #define TCPC_VBUS_STOP_DISCHARGE_THRESH		0x74
 #define TCPC_VBUS_VOLTAGE_ALARM_HI_CFG		0x76
 #define TCPC_VBUS_VOLTAGE_ALARM_LO_CFG		0x78
@@ -140,17 +145,22 @@
 /* I2C_WRITE_BYTE_COUNT + 1 when TX_BUF_BYTE_x is only accessible I2C_WRITE_BYTE_COUNT */
 #define TCPC_TRANSMIT_BUFFER_MAX_LEN		31
 
+struct tcpci;
+
 /*
- * @TX_BUF_BYTE_x_hidden
+ * @TX_BUF_BYTE_x_hidden:
  *		optional; Set when TX_BUF_BYTE_x can only be accessed through I2C_WRITE_BYTE_COUNT.
  * @frs_sourcing_vbus:
  *		Optional; Callback to perform chip specific operations when FRS
  *		is sourcing vbus.
+ * @auto_discharge_disconnect:
+ *		Optional; Enables TCPC to autonously discharge vbus on disconnect.
  */
-struct tcpci;
 struct tcpci_data {
 	struct regmap *regmap;
 	unsigned char TX_BUF_BYTE_x_hidden:1;
+	unsigned char auto_discharge_disconnect:1;
+
 	int (*init)(struct tcpci *tcpci, struct tcpci_data *data);
 	int (*set_vconn)(struct tcpci *tcpci, struct tcpci_data *data,
 			 bool enable);