// SPDX-License-Identifier: GPL-2.0+
/*
 * Raspberry Pi voltage sensor driver
 *
 * Based on firmware/raspberrypi.c by Noralf Trønnes
 *
 * Copyright (C) 2018 Stefan Wahren <stefan.wahren@i2se.com>
 */
#include <linux/device.h>
#include <linux/devm-helpers.h>
#include <linux/err.h>
#include <linux/hwmon.h>
#include <linux/module.h>
#include <linux/platform_device.h>
#include <linux/slab.h>
#include <linux/workqueue.h>
#include <soc/bcm2835/raspberrypi-firmware.h>

#define UNDERVOLTAGE_STICKY_BIT BIT(16)

struct rpi_hwmon_data {
        struct device *hwmon_dev;
        struct rpi_firmware *fw;
        u32 last_throttled;
        struct delayed_work get_values_poll_work;
};

static void rpi_firmware_get_throttled(struct rpi_hwmon_data *data)
{
        u32 new_uv, old_uv, value;
        int ret;

        /* Request firmware to clear sticky bits */
        value = 0xffff;

        ret = rpi_firmware_property(data->fw, RPI_FIRMWARE_GET_THROTTLED,
                                    &value, sizeof(value));
        if (ret) {
                dev_err_once(data->hwmon_dev, "Failed to get throttled (%d)\n",
                             ret);
                return;
        }

        new_uv = value & UNDERVOLTAGE_STICKY_BIT;
        old_uv = data->last_throttled & UNDERVOLTAGE_STICKY_BIT;
        data->last_throttled = value;

        if (new_uv == old_uv)
                return;

        if (new_uv)
                dev_crit(data->hwmon_dev, "Undervoltage detected!\n");
        else
                dev_info(data->hwmon_dev, "Voltage normalised\n");

        hwmon_notify_event(data->hwmon_dev, hwmon_in, hwmon_in_lcrit_alarm, 0);
}

static void get_values_poll(struct work_struct *work)
{
        struct rpi_hwmon_data *data;

        data = container_of(work, struct rpi_hwmon_data,
                            get_values_poll_work.work);

        rpi_firmware_get_throttled(data);

        /*
         * We can't run faster than the sticky shift (100ms) since we get
         * flipping in the sticky bits that are cleared.
         */
        schedule_delayed_work(&data->get_values_poll_work, 2 * HZ);
}

static int rpi_read(struct device *dev, enum hwmon_sensor_types type,
                    u32 attr, int channel, long *val)
{
        struct rpi_hwmon_data *data = dev_get_drvdata(dev);

        *val = !!(data->last_throttled & UNDERVOLTAGE_STICKY_BIT);
        return 0;
}

static const struct hwmon_channel_info * const rpi_info[] = {
        HWMON_CHANNEL_INFO(in,
                           HWMON_I_LCRIT_ALARM),
        NULL
};

static const struct hwmon_ops rpi_hwmon_ops = {
        .visible = 0444,
        .read = rpi_read,
};

static const struct hwmon_chip_info rpi_chip_info = {
        .ops = &rpi_hwmon_ops,
        .info = rpi_info,
};

static int rpi_hwmon_probe(struct platform_device *pdev)
{
        struct device *dev = &pdev->dev;
        struct rpi_hwmon_data *data;
        int ret;

        data = devm_kzalloc(dev, sizeof(*data), GFP_KERNEL);
        if (!data)
                return -ENOMEM;

        /* Parent driver assure that firmware is correct */
        data->fw = dev_get_drvdata(dev->parent);

        data->hwmon_dev = devm_hwmon_device_register_with_info(dev, "rpi_volt",
                                                               data,
                                                               &rpi_chip_info,
                                                               NULL);
        if (IS_ERR(data->hwmon_dev))
                return PTR_ERR(data->hwmon_dev);

        ret = devm_delayed_work_autocancel(dev, &data->get_values_poll_work,
                                           get_values_poll);
        if (ret)
                return ret;
        platform_set_drvdata(pdev, data);

        schedule_delayed_work(&data->get_values_poll_work, 2 * HZ);

        return 0;
}

static int rpi_hwmon_suspend(struct device *dev)
{
        struct rpi_hwmon_data *data = dev_get_drvdata(dev);

        cancel_delayed_work_sync(&data->get_values_poll_work);

        return 0;
}

static int rpi_hwmon_resume(struct device *dev)
{
        struct rpi_hwmon_data *data = dev_get_drvdata(dev);

        get_values_poll(&data->get_values_poll_work.work);

        return 0;
}

static DEFINE_SIMPLE_DEV_PM_OPS(rpi_hwmon_pm_ops, rpi_hwmon_suspend,
                                rpi_hwmon_resume);

static struct platform_driver rpi_hwmon_driver = {
        .probe = rpi_hwmon_probe,
        .driver = {
                .name = "raspberrypi-hwmon",
                .pm = pm_ptr(&rpi_hwmon_pm_ops),
        },
};
module_platform_driver(rpi_hwmon_driver);

MODULE_AUTHOR("Stefan Wahren <wahrenst@gmx.net>");
MODULE_DESCRIPTION("Raspberry Pi voltage sensor driver");
MODULE_LICENSE("GPL v2");
MODULE_ALIAS("platform:raspberrypi-hwmon");