[PATCH v2] extcon: add Maxim MAX3355 driver

[Sergei Shtylyov]

Maxim  Integrated MAX3355E chip integrates a  charge pump and comparators to
enable a system with an integrated USB OTG dual-role transceiver to function
as  an USB  OTG dual-role device.  In addition  to sensing/controlling Vbus,
the chip also passes thru the ID signal  from the USB  OTG connector.
On some Renesas boards,  this signal is  just fed into the SoC thru a GPIO
pin --  there's no real  OTG controller, only host and gadget USB controllers
sharing the same USB bus; however, we'd  like to allow host or gadget drivers
to be loaded depending on the cable type,  hence the need for the MAX3355
extcon driver. The Vbus status signals are also  wired to GPIOs (however, we
aren't currently interested in them),  the OFFVBUS# signal is controlled  by
the host controllers, there's  also the SHDN# signal wired to a GPIO, it
should be driven high for the  normal operation.

Signed-off-by: Sergei Shtylyov <sergei.shtylyov@xxxxxxxxxxxxxxxxxx>

---
The patch is against the 'extcon-next' branch of the 'extcon.git' repo.

Changes in version 2:
- added the USB gadget cable support;
- added the remove() driver method which drives SHDN# GPIO low to save power;
- dropped vendor prefix from the ID GPIO property name;
- changed the GPIO property name suffix to "-gpios";
- switched to usign extcon_set_cable_state_() API;
- switched to using the gpiod/sleeping 'gpiolib' APIs;
- addded error messages to max3355_probe();
- added IRQF_NO_SUSPEND flasg to the devm_request_threaded_irq() call;
- renamed 'ret' variable to 'err' in max3355_probe();
- expanded the Kconfig entry help text;
- added vendor name to the patch summary, the bindings document, the Kconfig
  entry, the driver heading comment, the module description, and the change log;
- fixed up and reformatted the change log.

 Documentation/devicetree/bindings/extcon/extcon-max3355.txt |   21 +
 drivers/extcon/Kconfig                                      |    8 
 drivers/extcon/Makefile                                     |    1 
 drivers/extcon/extcon-max3355.c                             |  153 ++++++++++++
 4 files changed, 183 insertions(+)

Index: extcon/Documentation/devicetree/bindings/extcon/extcon-max3355.txt
===================================================================
--- /dev/null
+++ extcon/Documentation/devicetree/bindings/extcon/extcon-max3355.txt
@@ -0,0 +1,21 @@
+Maxim Integrated MAX3355 USB OTG chip
+-------------------------------------
+
+MAX3355 integrates a charge pump and comparators to enable a system with an
+integrated USB OTG dual-role transceiver to function as a USB OTG dual-role
+device.
+
+Required properties:
+- compatible: should be "maxim,max3355";
+- maxim,shdn-gpios: should contain a phandle and GPIO specifier for the GPIO pin
+  connected to the MAX3355's SHDN# pin;
+- id-gpios: should contain a phandle and GPIO specifier for the GPIO pin
+  connected to the MAX3355's ID_OUT pin.
+
+Example (Koelsch board):
+
+	usb-otg {
+		compatible = "maxim,max3355";
+		maxim,shdn-gpios = <&gpio2 4 GPIO_ACTIVE_LOW>;
+		id-gpios = <&gpio5 31 GPIO_ACTIVE_HIGH>;
+	};
Index: extcon/drivers/extcon/Kconfig
===================================================================
--- extcon.orig/drivers/extcon/Kconfig
+++ extcon/drivers/extcon/Kconfig
@@ -52,6 +52,14 @@ config EXTCON_MAX14577
 	  Maxim MAX14577/77836. The MAX14577/77836 MUIC is a USB port accessory
 	  detector and switch.
 
+config EXTCON_MAX3355
+	tristate "Maxim MAX3355 USB OTG EXTCON Support"
+	help
+	  If you say yes here you get support for the USB OTG role detection by
+	  MAX3355. The MAX3355 chip integrates a charge pump and comparators to
+	  enable a system with an integrated USB OTG dual-role transceiver to
+	  function as an USB OTG dual-role device.
+
 config EXTCON_MAX77693
 	tristate "Maxim MAX77693 EXTCON Support"
 	depends on MFD_MAX77693 && INPUT
Index: extcon/drivers/extcon/Makefile
===================================================================
--- extcon.orig/drivers/extcon/Makefile
+++ extcon/drivers/extcon/Makefile
@@ -8,6 +8,7 @@ obj-$(CONFIG_EXTCON_ARIZONA)	+= extcon-a
 obj-$(CONFIG_EXTCON_AXP288)	+= extcon-axp288.o
 obj-$(CONFIG_EXTCON_GPIO)	+= extcon-gpio.o
 obj-$(CONFIG_EXTCON_MAX14577)	+= extcon-max14577.o
+obj-$(CONFIG_EXTCON_MAX3355)	+= extcon-max3355.o
 obj-$(CONFIG_EXTCON_MAX77693)	+= extcon-max77693.o
 obj-$(CONFIG_EXTCON_MAX77843)	+= extcon-max77843.o
 obj-$(CONFIG_EXTCON_MAX8997)	+= extcon-max8997.o
Index: extcon/drivers/extcon/extcon-max3355.c
===================================================================
--- /dev/null
+++ extcon/drivers/extcon/extcon-max3355.c
@@ -0,0 +1,153 @@
+/*
+ * Maxim Integrated MAX3355 USB OTG chip extcon driver
+ *
+ * Copyright (C) 2014 Cogent Embedded, Inc.
+ * Author: Sergei Shtylyov <sergei.shtylyov@xxxxxxxxxxxxxxxxxx>
+ *
+ * This software is licensed under the terms of the GNU General Public
+ * License version 2, as published by the Free Software Foundation, and
+ * may be copied, distributed, and modified under those terms.
+ */
+
+#include <linux/extcon.h>
+#include <linux/gpio.h>
+#include <linux/init.h>
+#include <linux/interrupt.h>
+#include <linux/kernel.h>
+#include <linux/module.h>
+#include <linux/of_gpio.h>
+#include <linux/platform_device.h>
+#include <linux/slab.h>
+#include <linux/workqueue.h>
+
+struct max3355_data {
+	struct extcon_dev *edev;
+	struct gpio_desc *id_gpiod;
+	struct gpio_desc *shdn_gpiod;
+};
+
+static const unsigned int max3355_cable[] = {
+	EXTCON_USB,
+	EXTCON_USB_HOST,
+	EXTCON_NONE,
+};
+
+static irqreturn_t max3355_id_irq(int irq, void *dev_id)
+{
+	struct max3355_data *data = dev_id;
+	int id = gpiod_get_value_cansleep(data->id_gpiod);
+
+	if (id) {
+		/*
+		 * ID = 1 means USB HOST cable detached.
+		 * As we don't have event for USB peripheral cable attached,
+		 * we simulate USB peripheral attach here.
+		 */
+		extcon_set_cable_state_(data->edev, EXTCON_USB_HOST, false);
+		extcon_set_cable_state_(data->edev, EXTCON_USB, true);
+	} else {
+		/*
+		 * ID = 0 means USB HOST cable attached.
+		 * As we don't have event for USB peripheral cable detached,
+		 * we simulate USB peripheral detach here.
+		 */
+		extcon_set_cable_state_(data->edev, EXTCON_USB, false);
+		extcon_set_cable_state_(data->edev, EXTCON_USB_HOST, true);
+	}
+
+	return IRQ_HANDLED;
+}
+
+static int max3355_probe(struct platform_device *pdev)
+{
+	struct device_node *np = pdev->dev.of_node;
+	struct max3355_data *data;
+	struct gpio_desc *gpiod;
+	int irq, err;
+
+	data = devm_kzalloc(&pdev->dev, sizeof(struct max3355_data),
+			    GFP_KERNEL);
+	if (!data)
+		return -ENOMEM;
+
+	data->edev = devm_extcon_dev_allocate(&pdev->dev, max3355_cable);
+	if (IS_ERR(data->edev)) {
+		dev_err(&pdev->dev, "failed to allocate extcon device\n");
+		return PTR_ERR(data->edev);
+	}
+	data->edev->name = kstrdup(np->name, GFP_KERNEL);
+
+	gpiod = devm_gpiod_get(&pdev->dev, "id", GPIOD_IN);
+	if (IS_ERR(gpiod)) {
+		dev_err(&pdev->dev, "failed to get ID_OUT GPIO\n");
+		return PTR_ERR(gpiod);
+	}
+	data->id_gpiod = gpiod;
+
+	gpiod = devm_gpiod_get(&pdev->dev, "maxim,shdn", GPIOD_OUT_HIGH);
+	if (IS_ERR(gpiod)) {
+		dev_err(&pdev->dev, "failed to get SHDN# GPIO\n");
+		return PTR_ERR(gpiod);
+	}
+	data->shdn_gpiod = gpiod;
+
+	err = devm_extcon_dev_register(&pdev->dev, data->edev);
+	if (err < 0) {
+		dev_err(&pdev->dev, "failed to register extcon device\n");
+		return err;
+	}
+
+	irq = gpiod_to_irq(data->id_gpiod);
+	if (irq < 0) {
+		dev_err(&pdev->dev, "failed to translate ID_OUT GPIO to IRQ\n");
+		return irq;
+	}
+
+	err = devm_request_threaded_irq(&pdev->dev, irq, NULL, max3355_id_irq,
+					IRQF_ONESHOT | IRQF_NO_SUSPEND |
+					IRQF_TRIGGER_RISING |
+					IRQF_TRIGGER_FALLING,
+					pdev->name, data);
+	if (err < 0) {
+		dev_err(&pdev->dev, "failed to request ID_OUT IRQ\n");
+		return err;
+	}
+
+	platform_set_drvdata(pdev, data);
+
+	/* Perform initial detection */
+	max3355_id_irq(irq, data);
+
+	return 0;
+}
+
+static int max3355_remove(struct platform_device *pdev)
+{
+	struct max3355_data *data = platform_get_drvdata(pdev);
+
+	gpiod_set_value_cansleep(data->shdn_gpiod, 0);
+
+	return 0;
+}
+
+static const struct of_device_id max3355_match_table[] = {
+	{ .compatible = "maxim,max3355", },
+	{ }
+};
+MODULE_DEVICE_TABLE(of, max3355_match_table);
+
+static struct platform_driver max3355_driver = {
+	.probe		= max3355_probe,
+	.remove		= max3355_remove,
+	.driver		= {
+		.name	= "extcon-max3355",
+		.of_match_table = max3355_match_table,
+		.owner	= THIS_MODULE,
+	},
+};
+
+module_platform_driver(max3355_driver);
+
+MODULE_AUTHOR("Sergei Shtylyov <sergei.shtylyov@xxxxxxxxxxxxxxxxxx>");
+MODULE_DESCRIPTION("Maxim MAX3355 extcon driver");
+MODULE_LICENSE("GPL v2");

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