extcon: Add driver for TI TUSB320

This patch adds an extcon driver for the TI TUSB320 USB Type-C device.
This can be used to detect whether the port is configured as a
downstream or upstream facing port.

Signed-off-by: Michael Auchter <[e-mail]>
Signed-off-by: Chanwoo Choi <[e-mail]>

drivers/extcon/Kconfig

···
 	  Say Y here to enable USB Type C cable detection extcon support when
 	  using Chrome OS EC based USB Type-C ports.
 
+config EXTCON_USBC_TUSB320
+	tristate "TI TUSB320 USB-C extcon support"
+	depends on I2C
+	select REGMAP_I2C
+	help
+	  Say Y here to enable support for USB Type C cable detection extcon
+	  support using a TUSB320.
+
 endif

drivers/extcon/Makefile

···
 obj-$(CONFIG_EXTCON_SM5502)	+= extcon-sm5502.o
 obj-$(CONFIG_EXTCON_USB_GPIO)	+= extcon-usb-gpio.o
 obj-$(CONFIG_EXTCON_USBC_CROS_EC) += extcon-usbc-cros-ec.o
+obj-$(CONFIG_EXTCON_USBC_TUSB320) += extcon-usbc-tusb320.o

drivers/extcon/extcon-usbc-tusb320.c

···
+// SPDX-License-Identifier: GPL-2.0
+/**
+ * drivers/extcon/extcon-tusb320.c - TUSB320 extcon driver
+ *
+ * Copyright (C) 2020 National Instruments Corporation
+ * Author: Michael Auchter <[e-mail]>
+ */
+
+#include <linux/extcon-provider.h>
+#include <linux/i2c.h>
+#include <linux/init.h>
+#include <linux/interrupt.h>
+#include <linux/kernel.h>
+#include <linux/module.h>
+#include <linux/regmap.h>
+
+#define TUSB320_REG9				0x9
+#define TUSB320_REG9_ATTACHED_STATE_SHIFT	6
+#define TUSB320_REG9_ATTACHED_STATE_MASK	0x3
+#define TUSB320_REG9_CABLE_DIRECTION		BIT(5)
+#define TUSB320_REG9_INTERRUPT_STATUS		BIT(4)
+#define TUSB320_ATTACHED_STATE_NONE		0x0
+#define TUSB320_ATTACHED_STATE_DFP		0x1
+#define TUSB320_ATTACHED_STATE_UFP		0x2
+#define TUSB320_ATTACHED_STATE_ACC		0x3
+
+struct tusb320_priv {
+	struct device *dev;
+	struct regmap *regmap;
+	struct extcon_dev *edev;
+};
+
+static const char * const tusb_attached_states[] = {
+	[TUSB320_ATTACHED_STATE_NONE] = "not attached",
+	[TUSB320_ATTACHED_STATE_DFP]  = "downstream facing port",
+	[TUSB320_ATTACHED_STATE_UFP]  = "upstream facing port",
+	[TUSB320_ATTACHED_STATE_ACC]  = "accessory",
+};
+
+static const unsigned int tusb320_extcon_cable[] = {
+	EXTCON_USB,
+	EXTCON_USB_HOST,
+	EXTCON_NONE,
+};
+
+static int tusb320_check_signature(struct tusb320_priv *priv)
+{
+	static const char sig[] = { '\0', 'T', 'U', 'S', 'B', '3', '2', '0' };
+	unsigned val;
+	int i, ret;
+
+	for (i = 0; i < sizeof(sig); i++) {
+		ret = regmap_read(priv->regmap, sizeof(sig) - 1 - i, &val);
+		if (ret < 0)
+			return ret;
+		if (val != sig[i]) {
+			dev_err(priv->dev, "signature mismatch!\n");
+			return -ENODEV;
+		}
+	}
+
+	return 0;
+}
+
+static irqreturn_t tusb320_irq_handler(int irq, void *dev_id)
+{
+	struct tusb320_priv *priv = dev_id;
+	int state, polarity;
+	unsigned reg;
+
+	if (regmap_read(priv->regmap, TUSB320_REG9, &reg)) {
+		dev_err(priv->dev, "error during i2c read!\n");
+		return IRQ_NONE;
+	}
+
+	if (!(reg & TUSB320_REG9_INTERRUPT_STATUS))
+		return IRQ_NONE;
+
+	state = (reg >> TUSB320_REG9_ATTACHED_STATE_SHIFT) &
+		TUSB320_REG9_ATTACHED_STATE_MASK;
+	polarity = !!(reg & TUSB320_REG9_CABLE_DIRECTION);
+
+	dev_dbg(priv->dev, "attached state: %s, polarity: %d\n",
+		tusb_attached_states[state], polarity);
+
+	extcon_set_state(priv->edev, EXTCON_USB,
+			 state == TUSB320_ATTACHED_STATE_UFP);
+	extcon_set_state(priv->edev, EXTCON_USB_HOST,
+			 state == TUSB320_ATTACHED_STATE_DFP);
+	extcon_set_property(priv->edev, EXTCON_USB,
+			    EXTCON_PROP_USB_TYPEC_POLARITY,
+			    (union extcon_property_value)polarity);
+	extcon_set_property(priv->edev, EXTCON_USB_HOST,
+			    EXTCON_PROP_USB_TYPEC_POLARITY,
+			    (union extcon_property_value)polarity);
+	extcon_sync(priv->edev, EXTCON_USB);
+	extcon_sync(priv->edev, EXTCON_USB_HOST);
+
+	regmap_write(priv->regmap, TUSB320_REG9, reg);
+
+	return IRQ_HANDLED;
+}
+
+static const struct regmap_config tusb320_regmap_config = {
+	.reg_bits = 8,
+	.val_bits = 8,
+};
+
+static int tusb320_extcon_probe(struct i2c_client *client,
+				const struct i2c_device_id *id)
+{
+	struct tusb320_priv *priv;
+	int ret;
+
+	priv = devm_kzalloc(&client->dev, sizeof(*priv), GFP_KERNEL);
+	if (!priv)
+		return -ENOMEM;
+	priv->dev = &client->dev;
+
+	priv->regmap = devm_regmap_init_i2c(client, &tusb320_regmap_config);
+	if (IS_ERR(priv->regmap))
+		return PTR_ERR(priv->regmap);
+
+	ret = tusb320_check_signature(priv);
+	if (ret)
+		return ret;
+
+	priv->edev = devm_extcon_dev_allocate(priv->dev, tusb320_extcon_cable);
+	if (IS_ERR(priv->edev)) {
+		dev_err(priv->dev, "failed to allocate extcon device\n");
+		return PTR_ERR(priv->edev);
+	}
+
+	ret = devm_extcon_dev_register(priv->dev, priv->edev);
+	if (ret < 0) {
+		dev_err(priv->dev, "failed to register extcon device\n");
+		return ret;
+	}
+
+	extcon_set_property_capability(priv->edev, EXTCON_USB,
+				       EXTCON_PROP_USB_TYPEC_POLARITY);
+	extcon_set_property_capability(priv->edev, EXTCON_USB_HOST,
+				       EXTCON_PROP_USB_TYPEC_POLARITY);
+
+	/* update initial state */
+	tusb320_irq_handler(client->irq, priv);
+
+	ret = devm_request_threaded_irq(priv->dev, client->irq, NULL,
+					tusb320_irq_handler,
+					IRQF_TRIGGER_FALLING | IRQF_ONESHOT,
+					client->name, priv);
+
+	return ret;
+}
+
+static const struct of_device_id tusb320_extcon_dt_match[] = {
+	{ .compatible = "ti,tusb320", },
+	{ }
+};
+MODULE_DEVICE_TABLE(of, tusb320_extcon_dt_match);
+
+static struct i2c_driver tusb320_extcon_driver = {
+	.probe		= tusb320_extcon_probe,
+	.driver		= {
+		.name	= "extcon-tusb320",
+		.of_match_table = tusb320_extcon_dt_match,
+	},
+};
+
+static int __init tusb320_init(void)
+{
+	return i2c_add_driver(&tusb320_extcon_driver);
+}
+subsys_initcall(tusb320_init);
+
+static void __exit tusb320_exit(void)
+{
+	i2c_del_driver(&tusb320_extcon_driver);
+}
+module_exit(tusb320_exit);
+
+MODULE_AUTHOR("Michael Auchter <[e-mail]>");
+MODULE_DESCRIPTION("TI TUSB320 extcon driver");
+MODULE_LICENSE("GPL v2");