// SPDX-License-Identifier: GPL-2.0-only
/*
 * Toggles a GPIO pin to restart a device
 *
 * Copyright (C) 2014 Google, Inc.
 *
 * Based on the gpio-poweroff driver.
 */
#include <linux/reboot.h>
#include <linux/kernel.h>
#include <linux/init.h>
#include <linux/delay.h>
#include <linux/platform_device.h>
#include <linux/gpio/consumer.h>
#include <linux/module.h>
#include <linux/of.h>

struct gpio_restart {
        struct gpio_desc *reset_gpio;
        u32 active_delay_ms;
        u32 inactive_delay_ms;
        u32 wait_delay_ms;
};

static int gpio_restart_notify(struct sys_off_data *data)
{
        struct gpio_restart *gpio_restart = data->cb_data;

        /* drive it active, also inactive->active edge */
        gpiod_direction_output(gpio_restart->reset_gpio, 1);
        mdelay(gpio_restart->active_delay_ms);

        /* drive inactive, also active->inactive edge */
        gpiod_set_value(gpio_restart->reset_gpio, 0);
        mdelay(gpio_restart->inactive_delay_ms);

        /* drive it active, also inactive->active edge */
        gpiod_set_value(gpio_restart->reset_gpio, 1);

        /* give it some time */
        mdelay(gpio_restart->wait_delay_ms);

        WARN_ON(1);

        return NOTIFY_DONE;
}

static int gpio_restart_probe(struct platform_device *pdev)
{
        struct gpio_restart *gpio_restart;
        bool open_source = false;
        int priority = 129;
        u32 property;
        int ret;

        gpio_restart = devm_kzalloc(&pdev->dev, sizeof(*gpio_restart),
                        GFP_KERNEL);
        if (!gpio_restart)
                return -ENOMEM;

        open_source = of_property_read_bool(pdev->dev.of_node, "open-source");

        gpio_restart->reset_gpio = devm_gpiod_get(&pdev->dev, NULL,
                        open_source ? GPIOD_IN : GPIOD_OUT_LOW);
        ret = PTR_ERR_OR_ZERO(gpio_restart->reset_gpio);
        if (ret) {
                if (ret != -EPROBE_DEFER)
                        dev_err(&pdev->dev, "Could not get reset GPIO\n");
                return ret;
        }

        gpio_restart->active_delay_ms = 100;
        gpio_restart->inactive_delay_ms = 100;
        gpio_restart->wait_delay_ms = 3000;

        ret = of_property_read_u32(pdev->dev.of_node, "priority", &property);
        if (!ret) {
                if (property > 255)
                        dev_err(&pdev->dev, "Invalid priority property: %u\n",
                                        property);
                else
                        priority = property;
        }

        of_property_read_u32(pdev->dev.of_node, "active-delay",
                        &gpio_restart->active_delay_ms);
        of_property_read_u32(pdev->dev.of_node, "inactive-delay",
                        &gpio_restart->inactive_delay_ms);
        of_property_read_u32(pdev->dev.of_node, "wait-delay",
                        &gpio_restart->wait_delay_ms);

        ret = devm_register_sys_off_handler(&pdev->dev,
                                            SYS_OFF_MODE_RESTART,
                                            priority,
                                            gpio_restart_notify,
                                            gpio_restart);
        if (ret) {
                dev_err(&pdev->dev, "%s: cannot register restart handler, %d\n",
                                __func__, ret);
                return -ENODEV;
        }

        return 0;
}

static const struct of_device_id of_gpio_restart_match[] = {
        { .compatible = "gpio-restart", },
        {},
};

static struct platform_driver gpio_restart_driver = {
        .probe = gpio_restart_probe,
        .driver = {
                .name = "restart-gpio",
                .of_match_table = of_gpio_restart_match,
        },
};

module_platform_driver(gpio_restart_driver);

MODULE_AUTHOR("David Riley <davidriley@chromium.org>");
MODULE_DESCRIPTION("GPIO restart driver");