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Date:   Mon, 21 Sep 2020 12:55:54 -0700
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Subject: [PATCH v8 10/11] usb: typec: tcpci: Implement Auto discharge
 disconnect callbacks
From:   Badhri Jagan Sridharan <badhri@google.com>
To:     Guenter Roeck <linux@roeck-us.net>,
        Heikki Krogerus <heikki.krogerus@linux.intel.com>,
        Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        Rob Herring <robh+dt@kernel.org>,
        Lee Jones <lee.jones@linaro.org>,
        Mark Brown <broonie@kernel.org>,
        Maxime Ripard <mripard@kernel.org>,
        Alexandre Belloni <alexandre.belloni@bootlin.com>,
        Thierry Reding <treding@nvidia.com>,
        Prashant Malani <pmalani@chromium.org>,
        Badhri Jagan Sridharan <badhri@google.com>
Cc:     devicetree@vger.kernel.org, linux-kernel@vger.kernel.org,
        linux-usb@vger.kernel.org
Content-Type: text/plain; charset="UTF-8"
Precedence: bulk

Implement callbacks for enabling/disabling
POWER_CONTROL.AutoDischargeDisconnect.

TCPCI spec allows TCPC hardware to autonomously discharge the vbus
capacitance upon disconnect. The expectation is that the TCPM enables
AutoDischargeDisconnect while entering SNK/SRC_ATTACHED states. Hardware
then automously discharges vbus when the vbus falls below a certain
threshold i.e. VBUS_SINK_DISCONNECT_THRESHOLD.

Apart from enabling the vbus discharge circuit, AutoDischargeDisconnect
is also used a flag to move TCPCI based TCPC implementations into
Attached.Snk/Attached.Src state as mentioned in
Figure 4-15. TCPC State Diagram before a Connection of the
USB Type-C Port Controller Interface Specification.
In such TCPC implementations, setting AutoDischargeDisconnect would
prevent TCPC into entering "Connection_Invalid" state as well.

Signed-off-by: Badhri Jagan Sridharan <badhri@google.com>
---
Changes since v1:
- Changing patch version to v6 to fix version number confusion.

Changes since v6:
- Rebase on usb-next.

Changes since v7:
Heikki's suggestion:
- Moved the actual write to TCPC_VBUS_SINK_DISCONNECT_THRESH
as it's common to all chip drivers.
- Renaming the tcpci_data callback as
get_auto_vbus_discharge_threshold
---
 drivers/usb/typec/tcpm/tcpci.c | 48 ++++++++++++++++++++++++++++++++++
 drivers/usb/typec/tcpm/tcpci.h | 22 ++++++++++++++--
 2 files changed, 68 insertions(+), 2 deletions(-)

diff --git a/drivers/usb/typec/tcpm/tcpci.c b/drivers/usb/typec/tcpm/tcpci.c
index f9f0af64da5f..dca21cd5873e 100644
--- a/drivers/usb/typec/tcpm/tcpci.c
+++ b/drivers/usb/typec/tcpm/tcpci.c
@@ -268,6 +268,48 @@ 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_role port_role,
+						   enum typec_pwr_opmode mode, bool pps_active,
+						   u32 requested_vbus_voltage_mv)
+{
+	struct tcpci *tcpci = tcpc_to_tcpci(dev);
+	u32 (*get_auto_vbus_threshold)(struct tcpci *tcpci, struct tcpci_data *data,
+				       enum typec_role port_role, enum typec_pwr_opmode mode,
+				       bool pps_active, u32 requested_vbus_voltage_mv);
+
+	get_auto_vbus_threshold = tcpci->data->get_auto_vbus_discharge_threshold;
+	if (get_auto_vbus_threshold) {
+		u32 threshold;
+		u16 val;
+
+		/*
+		 * Indicates that vbus is going to go away due PR_SWAP, hard reset etc.
+		 * Do not discharge vbus here.
+		 */
+		threshold = requested_vbus_voltage_mv ?
+			get_auto_vbus_threshold(tcpci, tcpci->data, port_role, mode, pps_active,
+						requested_vbus_voltage_mv) : 0;
+
+		val = threshold / TCPC_VBUS_SINK_DISCONNECT_THRESH_LSB_MV;
+		if (val > TCPC_VBUS_SINK_DISCONNECT_THRESH_MAX)
+			return -EINVAL;
+
+		return tcpci_write16(tcpci, TCPC_VBUS_SINK_DISCONNECT_THRESH, val);
+	}
+
+	return 0;
+}
+
 static int tcpci_enable_frs(struct tcpc_dev *dev, bool enable)
 {
 	struct tcpci *tcpci = tcpc_to_tcpci(dev);
@@ -629,6 +671,12 @@ struct tcpci *tcpci_register_port(struct device *dev, struct tcpci_data *data)
 	tcpci->tcpc.set_bist_data = tcpci_set_bist_data;
 	tcpci->tcpc.enable_frs = tcpci_enable_frs;
 
+	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);
diff --git a/drivers/usb/typec/tcpm/tcpci.h b/drivers/usb/typec/tcpm/tcpci.h
index 5ef07a56d67a..406dfb53f492 100644
--- a/drivers/usb/typec/tcpm/tcpci.h
+++ b/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
@@ -140,20 +145,33 @@
 /* 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.
+ * @auto_discharge_disconnect:
+ *		Optional; Enables TCPC to autonously discharge vbus on disconnect.
+ * @set_auto_vbus_discharge_threshold:
+ *		Mandatory when @auto_discharge_disconnect is sets. Allows
+ *		programming the voltage threshold of vbus below which TCPC
+ *		enables the vbus discharge circuit.
  */
-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);
 	int (*start_drp_toggling)(struct tcpci *tcpci, struct tcpci_data *data,
 				  enum typec_cc_status cc);
 	int (*set_vbus)(struct tcpci *tcpci, struct tcpci_data *data, bool source, bool sink);
+	u32 (*get_auto_vbus_discharge_threshold)(struct tcpci *tcpci, struct tcpci_data *data,
+						 enum typec_role port_role,
+						 enum typec_pwr_opmode mode, bool pps_active,
+						 u32 requested_vbus_voltage);
 };
 
 struct tcpci *tcpci_register_port(struct device *dev, struct tcpci_data *data);
-- 
2.28.0.681.g6f77f65b4e-goog