// SPDX-License-Identifier: GPL-2.0-only
/*
 * sl28cpld hardware monitoring driver
 *
 * Copyright 2020 Kontron Europe GmbH
 */

#include <linux/bitfield.h>
#include <linux/hwmon.h>
#include <linux/kernel.h>
#include <linux/mod_devicetable.h>
#include <linux/module.h>
#include <linux/platform_device.h>
#include <linux/property.h>
#include <linux/regmap.h>

#define FAN_INPUT               0x00
#define   FAN_SCALE_X8          BIT(7)
#define   FAN_VALUE_MASK        GENMASK(6, 0)

struct sl28cpld_hwmon {
        struct regmap *regmap;
        u32 offset;
};

static int sl28cpld_hwmon_read(struct device *dev,
                               enum hwmon_sensor_types type, u32 attr,
                               int channel, long *input)
{
        struct sl28cpld_hwmon *hwmon = dev_get_drvdata(dev);
        unsigned int value;
        int ret;

        switch (attr) {
        case hwmon_fan_input:
                ret = regmap_read(hwmon->regmap, hwmon->offset + FAN_INPUT,
                                  &value);
                if (ret)
                        return ret;
                /*
                 * The register has a 7 bit value and 1 bit which indicates the
                 * scale. If the MSB is set, then the lower 7 bit has to be
                 * multiplied by 8, to get the correct reading.
                 */
                if (value & FAN_SCALE_X8)
                        value = FIELD_GET(FAN_VALUE_MASK, value) << 3;

                /*
                 * The counter period is 1000ms and the sysfs specification
                 * says we should assume 2 pulses per revolution.
                 */
                value *= 60 / 2;

                break;
        default:
                return -EOPNOTSUPP;
        }

        *input = value;
        return 0;
}

static const struct hwmon_channel_info * const sl28cpld_hwmon_info[] = {
        HWMON_CHANNEL_INFO(fan, HWMON_F_INPUT),
        NULL
};

static const struct hwmon_ops sl28cpld_hwmon_ops = {
        .visible = 0444,
        .read = sl28cpld_hwmon_read,
};

static const struct hwmon_chip_info sl28cpld_hwmon_chip_info = {
        .ops = &sl28cpld_hwmon_ops,
        .info = sl28cpld_hwmon_info,
};

static int sl28cpld_hwmon_probe(struct platform_device *pdev)
{
        struct sl28cpld_hwmon *hwmon;
        struct device *hwmon_dev;
        int ret;

        if (!pdev->dev.parent)
                return -ENODEV;

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

        hwmon->regmap = dev_get_regmap(pdev->dev.parent, NULL);
        if (!hwmon->regmap)
                return -ENODEV;

        ret = device_property_read_u32(&pdev->dev, "reg", &hwmon->offset);
        if (ret)
                return -EINVAL;

        hwmon_dev = devm_hwmon_device_register_with_info(&pdev->dev,
                                "sl28cpld_hwmon", hwmon,
                                &sl28cpld_hwmon_chip_info, NULL);
        if (IS_ERR(hwmon_dev))
                dev_err(&pdev->dev, "failed to register as hwmon device");

        return PTR_ERR_OR_ZERO(hwmon_dev);
}

static const struct of_device_id sl28cpld_hwmon_of_match[] = {
        { .compatible = "kontron,sl28cpld-fan" },
        {}
};
MODULE_DEVICE_TABLE(of, sl28cpld_hwmon_of_match);

static struct platform_driver sl28cpld_hwmon_driver = {
        .probe = sl28cpld_hwmon_probe,
        .driver = {
                .name = "sl28cpld-fan",
                .of_match_table = sl28cpld_hwmon_of_match,
        },
};
module_platform_driver(sl28cpld_hwmon_driver);

MODULE_DESCRIPTION("sl28cpld Hardware Monitoring Driver");
MODULE_AUTHOR("Michael Walle <michael@walle.cc>");
MODULE_LICENSE("GPL");