USB: otg: gpio_vbus transceiver stub

gpio_vbus provides simple GPIO VBUS sensing for peripheral
controllers with an internal transceiver.
Optionally, a second GPIO can be used to control D+ pullup.

It also interfaces with the regulator framework to limit charging
currents when powered via USB. gpio_vbus requests the regulator
supplying "vbus_draw" and can enable/disable it or limit its
current depending on USB state.

[[e-mail]: use drivers/otg, cleanups ]

Signed-off-by: Philipp Zabel <[e-mail]>
Signed-off-by: David Brownell <[e-mail]>
Signed-off-by: Greg Kroah-Hartman <[e-mail]>

drivers/usb/otg/Kconfig

···
 	  Select this to make sure the build includes objects from
 	  the OTG infrastructure directory.
 
+#
+# USB Transceiver Drivers
+#
+config USB_GPIO_VBUS
+	tristate "GPIO based peripheral-only VBUS sensing 'transceiver'"
+	depends on GENERIC_GPIO
+	select USB_OTG_UTILS
+	help
+	  Provides simple GPIO VBUS sensing for controllers with an
+	  internal transceiver via the otg_transceiver interface, and
+	  optionally control of a D+ pullup GPIO as well as a VBUS
+	  current limit regulator.
+
 config ISP1301_OMAP
 	tristate "Philips ISP1301 with OMAP OTG"
 	depends on I2C && ARCH_OMAP_OTG

drivers/usb/otg/Makefile

···
+#
+# OTG infrastructure and transceiver drivers
+#
+
+obj-$(CONFIG_USB_GPIO_VBUS)	+= gpio_vbus.o
 obj-$(CONFIG_ISP1301_OMAP)	+= isp1301_omap.o
 
 ifeq ($(CONFIG_USB_DEBUG),y)

drivers/usb/otg/gpio_vbus.c

···
+/*
+ * gpio-vbus.c - simple GPIO VBUS sensing driver for B peripheral devices
+ *
+ * Copyright (c) 2008 Philipp Zabel <[e-mail]>
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License version 2 as
+ * published by the Free Software Foundation.
+ */
+
+#include <linux/kernel.h>
+#include <linux/platform_device.h>
+#include <linux/gpio.h>
+#include <linux/interrupt.h>
+#include <linux/usb.h>
+
+#include <linux/regulator/consumer.h>
+
+#include <linux/usb/gadget.h>
+#include <linux/usb/gpio_vbus.h>
+#include <linux/usb/otg.h>
+
+
+/*
+ * A simple GPIO VBUS sensing driver for B peripheral only devices
+ * with internal transceivers. It can control a D+ pullup GPIO and
+ * a regulator to limit the current drawn from VBUS.
+ *
+ * Needs to be loaded before the UDC driver that will use it.
+ */
+struct gpio_vbus_data {
+	struct otg_transceiver otg;
+	struct device          *dev;
+	struct regulator       *vbus_draw;
+	int			vbus_draw_enabled;
+	unsigned		mA;
+};
+
+
+/*
+ * This driver relies on "both edges" triggering.  VBUS has 100 msec to
+ * stabilize, so the peripheral controller driver may need to cope with
+ * some bouncing due to current surges (e.g. charging local capacitance)
+ * and contact chatter.
+ *
+ * REVISIT in desperate straits, toggling between rising and falling
+ * edges might be workable.
+ */
+#define VBUS_IRQ_FLAGS \
+	( IRQF_SAMPLE_RANDOM | IRQF_SHARED \
+	| IRQF_TRIGGER_RISING | IRQF_TRIGGER_FALLING )
+
+
+/* interface to regulator framework */
+static void set_vbus_draw(struct gpio_vbus_data *gpio_vbus, unsigned mA)
+{
+	struct regulator *vbus_draw = gpio_vbus->vbus_draw;
+	int enabled;
+
+	if (!vbus_draw)
+		return;
+
+	enabled = gpio_vbus->vbus_draw_enabled;
+	if (mA) {
+		regulator_set_current_limit(vbus_draw, 0, 1000 * mA);
+		if (!enabled) {
+			regulator_enable(vbus_draw);
+			gpio_vbus->vbus_draw_enabled = 1;
+		}
+	} else {
+		if (enabled) {
+			regulator_disable(vbus_draw);
+			gpio_vbus->vbus_draw_enabled = 0;
+		}
+	}
+	gpio_vbus->mA = mA;
+}
+
+/* VBUS change IRQ handler */
+static irqreturn_t gpio_vbus_irq(int irq, void *data)
+{
+	struct platform_device *pdev = data;
+	struct gpio_vbus_mach_info *pdata = pdev->dev.platform_data;
+	struct gpio_vbus_data *gpio_vbus = platform_get_drvdata(pdev);
+	int gpio, vbus;
+
+	vbus = gpio_get_value(pdata->gpio_vbus);
+	if (pdata->gpio_vbus_inverted)
+		vbus = !vbus;
+
+	dev_dbg(&pdev->dev, "VBUS %s (gadget: %s)\n",
+		vbus ? "supplied" : "inactive",
+		gpio_vbus->otg.gadget ? gpio_vbus->otg.gadget->name : "none");
+
+	if (!gpio_vbus->otg.gadget)
+		return IRQ_HANDLED;
+
+	/* Peripheral controllers which manage the pullup themselves won't have
+	 * gpio_pullup configured here.  If it's configured here, we'll do what
+	 * isp1301_omap::b_peripheral() does and enable the pullup here... although
+	 * that may complicate usb_gadget_{,dis}connect() support.
+	 */
+	gpio = pdata->gpio_pullup;
+	if (vbus) {
+		gpio_vbus->otg.state = OTG_STATE_B_PERIPHERAL;
+		usb_gadget_vbus_connect(gpio_vbus->otg.gadget);
+
+		/* drawing a "unit load" is *always* OK, except for OTG */
+		set_vbus_draw(gpio_vbus, 100);
+
+		/* optionally enable D+ pullup */
+		if (gpio_is_valid(gpio))
+			gpio_set_value(gpio, !pdata->gpio_pullup_inverted);
+	} else {
+		/* optionally disable D+ pullup */
+		if (gpio_is_valid(gpio))
+			gpio_set_value(gpio, pdata->gpio_pullup_inverted);
+
+		set_vbus_draw(gpio_vbus, 0);
+
+		usb_gadget_vbus_disconnect(gpio_vbus->otg.gadget);
+		gpio_vbus->otg.state = OTG_STATE_B_IDLE;
+	}
+
+	return IRQ_HANDLED;
+}
+
+/* OTG transceiver interface */
+
+/* bind/unbind the peripheral controller */
+static int gpio_vbus_set_peripheral(struct otg_transceiver *otg,
+				struct usb_gadget *gadget)
+{
+	struct gpio_vbus_data *gpio_vbus;
+	struct gpio_vbus_mach_info *pdata;
+	struct platform_device *pdev;
+	int gpio, irq;
+
+	gpio_vbus = container_of(otg, struct gpio_vbus_data, otg);
+	pdev = to_platform_device(gpio_vbus->dev);
+	pdata = gpio_vbus->dev->platform_data;
+	irq = gpio_to_irq(pdata->gpio_vbus);
+	gpio = pdata->gpio_pullup;
+
+	if (!gadget) {
+		dev_dbg(&pdev->dev, "unregistering gadget '%s'\n",
+			otg->gadget->name);
+
+		/* optionally disable D+ pullup */
+		if (gpio_is_valid(gpio))
+			gpio_set_value(gpio, pdata->gpio_pullup_inverted);
+
+		set_vbus_draw(gpio_vbus, 0);
+
+		usb_gadget_vbus_disconnect(otg->gadget);
+		otg->state = OTG_STATE_UNDEFINED;
+
+		otg->gadget = NULL;
+		return 0;
+	}
+
+	otg->gadget = gadget;
+	dev_dbg(&pdev->dev, "registered gadget '%s'\n", gadget->name);
+
+	/* initialize connection state */
+	gpio_vbus_irq(irq, pdev);
+	return 0;
+}
+
+/* effective for B devices, ignored for A-peripheral */
+static int gpio_vbus_set_power(struct otg_transceiver *otg, unsigned mA)
+{
+	struct gpio_vbus_data *gpio_vbus;
+
+	gpio_vbus = container_of(otg, struct gpio_vbus_data, otg);
+
+	if (otg->state == OTG_STATE_B_PERIPHERAL)
+		set_vbus_draw(gpio_vbus, mA);
+	return 0;
+}
+
+/* for non-OTG B devices: set/clear transceiver suspend mode */
+static int gpio_vbus_set_suspend(struct otg_transceiver *otg, int suspend)
+{
+	struct gpio_vbus_data *gpio_vbus;
+
+	gpio_vbus = container_of(otg, struct gpio_vbus_data, otg);
+
+	/* draw max 0 mA from vbus in suspend mode; or the previously
+	 * recorded amount of current if not suspended
+	 *
+	 * NOTE: high powered configs (mA > 100) may draw up to 2.5 mA
+	 * if they're wake-enabled ... we don't handle that yet.
+	 */
+	return gpio_vbus_set_power(otg, suspend ? 0 : gpio_vbus->mA);
+}
+
+/* platform driver interface */
+
+static int __init gpio_vbus_probe(struct platform_device *pdev)
+{
+	struct gpio_vbus_mach_info *pdata = pdev->dev.platform_data;
+	struct gpio_vbus_data *gpio_vbus;
+	struct resource *res;
+	int err, gpio, irq;
+
+	if (!pdata || !gpio_is_valid(pdata->gpio_vbus))
+		return -EINVAL;
+	gpio = pdata->gpio_vbus;
+
+	gpio_vbus = kzalloc(sizeof(struct gpio_vbus_data), GFP_KERNEL);
+	if (!gpio_vbus)
+		return -ENOMEM;
+
+	platform_set_drvdata(pdev, gpio_vbus);
+	gpio_vbus->dev = &pdev->dev;
+	gpio_vbus->otg.label = "gpio-vbus";
+	gpio_vbus->otg.state = OTG_STATE_UNDEFINED;
+	gpio_vbus->otg.set_peripheral = gpio_vbus_set_peripheral;
+	gpio_vbus->otg.set_power = gpio_vbus_set_power;
+	gpio_vbus->otg.set_suspend = gpio_vbus_set_suspend;
+
+	err = gpio_request(gpio, "vbus_detect");
+	if (err) {
+		dev_err(&pdev->dev, "can't request vbus gpio %d, err: %d\n",
+			gpio, err);
+		goto err_gpio;
+	}
+	gpio_direction_input(gpio);
+
+	res = platform_get_resource(pdev, IORESOURCE_IRQ, 0);
+	if (res) {
+		irq = res->start;
+		res->flags &= IRQF_TRIGGER_MASK;
+		res->flags |= IRQF_SAMPLE_RANDOM | IRQF_SHARED;
+	} else
+		irq = gpio_to_irq(gpio);
+
+	/* if data line pullup is in use, initialize it to "not pulling up" */
+	gpio = pdata->gpio_pullup;
+	if (gpio_is_valid(gpio)) {
+		err = gpio_request(gpio, "udc_pullup");
+		if (err) {
+			dev_err(&pdev->dev,
+				"can't request pullup gpio %d, err: %d\n",
+				gpio, err);
+			gpio_free(pdata->gpio_vbus);
+			goto err_gpio;
+		}
+		gpio_direction_output(gpio, pdata->gpio_pullup_inverted);
+	}
+
+	err = request_irq(irq, gpio_vbus_irq, VBUS_IRQ_FLAGS,
+		"vbus_detect", pdev);
+	if (err) {
+		dev_err(&pdev->dev, "can't request irq %i, err: %d\n",
+			irq, err);
+		goto err_irq;
+	}
+
+	/* only active when a gadget is registered */
+	err = otg_set_transceiver(&gpio_vbus->otg);
+	if (err) {
+		dev_err(&pdev->dev, "can't register transceiver, err: %d\n",
+			err);
+		goto err_otg;
+	}
+
+	gpio_vbus->vbus_draw = regulator_get(&pdev->dev, "vbus_draw");
+	if (IS_ERR(gpio_vbus->vbus_draw)) {
+		dev_dbg(&pdev->dev, "can't get vbus_draw regulator, err: %ld\n",
+			PTR_ERR(gpio_vbus->vbus_draw));
+		gpio_vbus->vbus_draw = NULL;
+	}
+
+	return 0;
+err_otg:
+	free_irq(irq, &pdev->dev);
+err_irq:
+	if (gpio_is_valid(pdata->gpio_pullup))
+		gpio_free(pdata->gpio_pullup);
+	gpio_free(pdata->gpio_vbus);
+err_gpio:
+	platform_set_drvdata(pdev, NULL);
+	kfree(gpio_vbus);
+	return err;
+}
+
+static int __exit gpio_vbus_remove(struct platform_device *pdev)
+{
+	struct gpio_vbus_data *gpio_vbus = platform_get_drvdata(pdev);
+	struct gpio_vbus_mach_info *pdata = pdev->dev.platform_data;
+	int gpio = pdata->gpio_vbus;
+
+	regulator_put(gpio_vbus->vbus_draw);
+
+	otg_set_transceiver(NULL);
+
+	free_irq(gpio_to_irq(gpio), &pdev->dev);
+	if (gpio_is_valid(pdata->gpio_pullup))
+		gpio_free(pdata->gpio_pullup);
+	gpio_free(gpio);
+	platform_set_drvdata(pdev, NULL);
+	kfree(gpio_vbus);
+
+	return 0;
+}
+
+/* NOTE:  the gpio-vbus device may *NOT* be hotplugged */
+
+MODULE_ALIAS("platform:gpio-vbus");
+
+static struct platform_driver gpio_vbus_driver = {
+	.driver = {
+		.name  = "gpio-vbus",
+		.owner = THIS_MODULE,
+	},
+	.remove  = __exit_p(gpio_vbus_remove),
+};
+
+static int __init gpio_vbus_init(void)
+{
+	return platform_driver_probe(&gpio_vbus_driver, gpio_vbus_probe);
+}
+module_init(gpio_vbus_init);
+
+static void __exit gpio_vbus_exit(void)
+{
+	platform_driver_unregister(&gpio_vbus_driver);
+}
+module_exit(gpio_vbus_exit);
+
+MODULE_DESCRIPTION("simple GPIO controlled OTG transceiver driver");
+MODULE_AUTHOR("Philipp Zabel");
+MODULE_LICENSE("GPL");

include/linux/usb/gpio_vbus.h

···
+/*
+ * A simple GPIO VBUS sensing driver for B peripheral only devices
+ * with internal transceivers.
+ * Optionally D+ pullup can be controlled by a second GPIO.
+ *
+ * Copyright (c) 2008 Philipp Zabel <[e-mail]>
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License version 2 as
+ * published by the Free Software Foundation.
+ *
+ */
+
+/**
+ * struct gpio_vbus_mach_info - configuration for gpio_vbus
+ * @gpio_vbus: VBUS sensing GPIO
+ * @gpio_pullup: optional D+ or D- pullup GPIO (else negative/invalid)
+ * @gpio_vbus_inverted: true if gpio_vbus is active low
+ * @gpio_pullup_inverted: true if gpio_pullup is active low
+ *
+ * The VBUS sensing GPIO should have a pulldown, which will normally be
+ * part of a resistor ladder turning a 4.0V-5.25V level on VBUS into a
+ * value the GPIO detects as active.  Some systems will use comparators.
+ */
+struct gpio_vbus_mach_info {
+	int gpio_vbus;
+	int gpio_pullup;
+	bool gpio_vbus_inverted;
+	bool gpio_pullup_inverted;
+};