// SPDX-License-Identifier: GPL-2.0
/*
 * gpio-vbus.c - simple GPIO VBUS sensing driver for B peripheral devices
 *
 * Copyright (c) 2008 Philipp Zabel <philipp.zabel@gmail.com>
 */

#include <linux/kernel.h>
#include <linux/platform_device.h>
#include <linux/gpio/consumer.h>
#include <linux/module.h>
#include <linux/slab.h>
#include <linux/interrupt.h>
#include <linux/usb.h>
#include <linux/workqueue.h>

#include <linux/regulator/consumer.h>

#include <linux/usb/gadget.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 gpio_desc        *vbus_gpiod;
        struct gpio_desc        *pullup_gpiod;
        struct usb_phy          phy;
        struct device          *dev;
        struct regulator       *vbus_draw;
        int                     vbus_draw_enabled;
        unsigned                mA;
        struct delayed_work     work;
        int                     vbus;
        int                     irq;
};


/*
 * 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_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;
        int ret;

        if (!vbus_draw)
                return;

        enabled = gpio_vbus->vbus_draw_enabled;
        if (mA) {
                regulator_set_current_limit(vbus_draw, 0, 1000 * mA);
                if (!enabled) {
                        ret = regulator_enable(vbus_draw);
                        if (ret < 0)
                                return;
                        gpio_vbus->vbus_draw_enabled = 1;
                }
        } else {
                if (enabled) {
                        ret = regulator_disable(vbus_draw);
                        if (ret < 0)
                                return;
                        gpio_vbus->vbus_draw_enabled = 0;
                }
        }
        gpio_vbus->mA = mA;
}

static int is_vbus_powered(struct gpio_vbus_data *gpio_vbus)
{
        return gpiod_get_value(gpio_vbus->vbus_gpiod);
}

static void gpio_vbus_work(struct work_struct *work)
{
        struct gpio_vbus_data *gpio_vbus =
                container_of(work, struct gpio_vbus_data, work.work);
        int status, vbus;

        if (!gpio_vbus->phy.otg->gadget)
                return;

        vbus = is_vbus_powered(gpio_vbus);
        if ((vbus ^ gpio_vbus->vbus) == 0)
                return;
        gpio_vbus->vbus = vbus;

        /* Peripheral controllers which manage the pullup themselves won't have
         * a pullup GPIO 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.
         */

        if (vbus) {
                status = USB_EVENT_VBUS;
                gpio_vbus->phy.otg->state = OTG_STATE_B_PERIPHERAL;
                gpio_vbus->phy.last_event = status;
                usb_gadget_vbus_connect(gpio_vbus->phy.otg->gadget);

                /* drawing a "unit load" is *always* OK, except for OTG */
                set_vbus_draw(gpio_vbus, 100);

                /* optionally enable D+ pullup */
                if (gpio_vbus->pullup_gpiod)
                        gpiod_set_value(gpio_vbus->pullup_gpiod, 1);

                atomic_notifier_call_chain(&gpio_vbus->phy.notifier,
                                           status, gpio_vbus->phy.otg->gadget);
                usb_phy_set_event(&gpio_vbus->phy, USB_EVENT_ENUMERATED);
        } else {
                /* optionally disable D+ pullup */
                if (gpio_vbus->pullup_gpiod)
                        gpiod_set_value(gpio_vbus->pullup_gpiod, 0);

                set_vbus_draw(gpio_vbus, 0);

                usb_gadget_vbus_disconnect(gpio_vbus->phy.otg->gadget);
                status = USB_EVENT_NONE;
                gpio_vbus->phy.otg->state = OTG_STATE_B_IDLE;
                gpio_vbus->phy.last_event = status;

                atomic_notifier_call_chain(&gpio_vbus->phy.notifier,
                                           status, gpio_vbus->phy.otg->gadget);
                usb_phy_set_event(&gpio_vbus->phy, USB_EVENT_NONE);
        }
}

/* VBUS change IRQ handler */
static irqreturn_t gpio_vbus_irq(int irq, void *data)
{
        struct platform_device *pdev = data;
        struct gpio_vbus_data *gpio_vbus = platform_get_drvdata(pdev);
        struct usb_otg *otg = gpio_vbus->phy.otg;

        dev_dbg(&pdev->dev, "VBUS %s (gadget: %s)\n",
                is_vbus_powered(gpio_vbus) ? "supplied" : "inactive",
                otg->gadget ? otg->gadget->name : "none");

        if (otg->gadget)
                schedule_delayed_work(&gpio_vbus->work, msecs_to_jiffies(100));

        return IRQ_HANDLED;
}

/* OTG transceiver interface */

/* bind/unbind the peripheral controller */
static int gpio_vbus_set_peripheral(struct usb_otg *otg,
                                        struct usb_gadget *gadget)
{
        struct gpio_vbus_data *gpio_vbus;
        struct platform_device *pdev;

        gpio_vbus = container_of(otg->usb_phy, struct gpio_vbus_data, phy);
        pdev = to_platform_device(gpio_vbus->dev);

        if (!gadget) {
                dev_dbg(&pdev->dev, "unregistering gadget '%s'\n",
                        otg->gadget->name);

                /* optionally disable D+ pullup */
                if (gpio_vbus->pullup_gpiod)
                        gpiod_set_value(gpio_vbus->pullup_gpiod, 0);

                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->vbus = 0; /* start with disconnected */
        gpio_vbus_irq(gpio_vbus->irq, pdev);
        return 0;
}

/* effective for B devices, ignored for A-peripheral */
static int gpio_vbus_set_power(struct usb_phy *phy, unsigned mA)
{
        struct gpio_vbus_data *gpio_vbus;

        gpio_vbus = container_of(phy, struct gpio_vbus_data, phy);

        if (phy->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 usb_phy *phy, int suspend)
{
        struct gpio_vbus_data *gpio_vbus;

        gpio_vbus = container_of(phy, struct gpio_vbus_data, phy);

        /* 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(phy, suspend ? 0 : gpio_vbus->mA);
}

/* platform driver interface */

static int gpio_vbus_probe(struct platform_device *pdev)
{
        struct gpio_vbus_data *gpio_vbus;
        struct resource *res;
        struct device *dev = &pdev->dev;
        int err, irq;
        unsigned long irqflags;

        gpio_vbus = devm_kzalloc(&pdev->dev, sizeof(struct gpio_vbus_data),
                                 GFP_KERNEL);
        if (!gpio_vbus)
                return -ENOMEM;

        gpio_vbus->phy.otg = devm_kzalloc(&pdev->dev, sizeof(struct usb_otg),
                                          GFP_KERNEL);
        if (!gpio_vbus->phy.otg)
                return -ENOMEM;

        platform_set_drvdata(pdev, gpio_vbus);
        gpio_vbus->dev = &pdev->dev;
        gpio_vbus->phy.label = "gpio-vbus";
        gpio_vbus->phy.dev = gpio_vbus->dev;
        gpio_vbus->phy.set_power = gpio_vbus_set_power;
        gpio_vbus->phy.set_suspend = gpio_vbus_set_suspend;

        gpio_vbus->phy.otg->state = OTG_STATE_UNDEFINED;
        gpio_vbus->phy.otg->usb_phy = &gpio_vbus->phy;
        gpio_vbus->phy.otg->set_peripheral = gpio_vbus_set_peripheral;

        /* Look up the VBUS sensing GPIO */
        gpio_vbus->vbus_gpiod = devm_gpiod_get(dev, "vbus", GPIOD_IN);
        if (IS_ERR(gpio_vbus->vbus_gpiod)) {
                err = PTR_ERR(gpio_vbus->vbus_gpiod);
                dev_err(&pdev->dev, "can't request vbus gpio, err: %d\n", err);
                return err;
        }
        gpiod_set_consumer_name(gpio_vbus->vbus_gpiod, "vbus_detect");

        res = platform_get_resource(pdev, IORESOURCE_IRQ, 0);
        if (res) {
                irq = res->start;
                irqflags = (res->flags & IRQF_TRIGGER_MASK) | IRQF_SHARED;
        } else {
                irq = gpiod_to_irq(gpio_vbus->vbus_gpiod);
                irqflags = VBUS_IRQ_FLAGS;
        }

        gpio_vbus->irq = irq;

        /*
         * 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.
         * Get the optional D+ or D- pullup GPIO. If the data line pullup is
         * in use, initialize it to "not pulling up"
         */
        gpio_vbus->pullup_gpiod = devm_gpiod_get_optional(dev, "pullup",
                                                          GPIOD_OUT_LOW);
        if (IS_ERR(gpio_vbus->pullup_gpiod)) {
                err = PTR_ERR(gpio_vbus->pullup_gpiod);
                dev_err(&pdev->dev, "can't request pullup gpio, err: %d\n",
                        err);
                return err;
        }
        if (gpio_vbus->pullup_gpiod)
                gpiod_set_consumer_name(gpio_vbus->pullup_gpiod, "udc_pullup");

        err = devm_request_irq(&pdev->dev, irq, gpio_vbus_irq, irqflags,
                               "vbus_detect", pdev);
        if (err) {
                dev_err(&pdev->dev, "can't request irq %i, err: %d\n",
                        irq, err);
                return err;
        }

        INIT_DELAYED_WORK(&gpio_vbus->work, gpio_vbus_work);

        gpio_vbus->vbus_draw = devm_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;
        }

        /* only active when a gadget is registered */
        err = usb_add_phy(&gpio_vbus->phy, USB_PHY_TYPE_USB2);
        if (err) {
                dev_err(&pdev->dev, "can't register transceiver, err: %d\n",
                        err);
                return err;
        }

        /* TODO: wakeup could be enabled here with device_init_wakeup(dev, 1) */

        return 0;
}

static void gpio_vbus_remove(struct platform_device *pdev)
{
        struct gpio_vbus_data *gpio_vbus = platform_get_drvdata(pdev);

        device_init_wakeup(&pdev->dev, 0);
        cancel_delayed_work_sync(&gpio_vbus->work);

        usb_remove_phy(&gpio_vbus->phy);
}

#ifdef CONFIG_PM
static int gpio_vbus_pm_suspend(struct device *dev)
{
        struct gpio_vbus_data *gpio_vbus = dev_get_drvdata(dev);

        if (device_may_wakeup(dev))
                enable_irq_wake(gpio_vbus->irq);

        return 0;
}

static int gpio_vbus_pm_resume(struct device *dev)
{
        struct gpio_vbus_data *gpio_vbus = dev_get_drvdata(dev);

        if (device_may_wakeup(dev))
                disable_irq_wake(gpio_vbus->irq);

        return 0;
}

static const struct dev_pm_ops gpio_vbus_dev_pm_ops = {
        .suspend        = gpio_vbus_pm_suspend,
        .resume         = gpio_vbus_pm_resume,
};
#endif

MODULE_ALIAS("platform:gpio-vbus");

/*
 * NOTE: this driver matches against "gpio-usb-b-connector" for
 * devices that do NOT support role switch.
 */
static const struct of_device_id gpio_vbus_of_match[] = {
        {
                .compatible = "gpio-usb-b-connector",
        },
        {},
};
MODULE_DEVICE_TABLE(of, gpio_vbus_of_match);

static struct platform_driver gpio_vbus_driver = {
        .driver = {
                .name  = "gpio-vbus",
#ifdef CONFIG_PM
                .pm = &gpio_vbus_dev_pm_ops,
#endif
                .of_match_table = gpio_vbus_of_match,
        },
        .probe          = gpio_vbus_probe,
        .remove         = gpio_vbus_remove,
};

module_platform_driver(gpio_vbus_driver);

MODULE_DESCRIPTION("simple GPIO controlled OTG transceiver driver");
MODULE_AUTHOR("Philipp Zabel");
MODULE_LICENSE("GPL");