// SPDX-License-Identifier: GPL-2.0
/*
 * Copyright (C) 2025 KEBA Industrial Automation GmbH
 *
 * Driver for KEBA battery monitoring controller FPGA IP core
 */

#include <linux/hwmon.h>
#include <linux/io.h>
#include <linux/delay.h>
#include <linux/module.h>
#include <linux/device.h>
#include <linux/auxiliary_bus.h>
#include <linux/misc/keba.h>
#include <linux/mutex.h>

#define KBATT "kbatt"

#define KBATT_CONTROL_REG               0x4
#define   KBATT_CONTROL_BAT_TEST        0x01

#define KBATT_STATUS_REG                0x8
#define   KBATT_STATUS_BAT_OK           0x01

#define KBATT_MAX_UPD_INTERVAL  (10 * HZ)
#define KBATT_SETTLE_TIME_US    (100 * USEC_PER_MSEC)

struct kbatt {
        /* update lock */
        struct mutex lock;
        void __iomem *base;

        unsigned long next_update; /* in jiffies */
        bool alarm;
};

static bool kbatt_alarm(struct kbatt *kbatt)
{
        mutex_lock(&kbatt->lock);

        if (!kbatt->next_update || time_after(jiffies, kbatt->next_update)) {
                /* switch load on */
                iowrite8(KBATT_CONTROL_BAT_TEST,
                         kbatt->base + KBATT_CONTROL_REG);

                /* wait some time to let things settle */
                fsleep(KBATT_SETTLE_TIME_US);

                /* check battery state */
                if (ioread8(kbatt->base + KBATT_STATUS_REG) &
                    KBATT_STATUS_BAT_OK)
                        kbatt->alarm = false;
                else
                        kbatt->alarm = true;

                /* switch load off */
                iowrite8(0, kbatt->base + KBATT_CONTROL_REG);

                kbatt->next_update = jiffies + KBATT_MAX_UPD_INTERVAL;
        }

        mutex_unlock(&kbatt->lock);

        return kbatt->alarm;
}

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

        *val = kbatt_alarm(kbatt) ? 1 : 0;

        return 0;
}

static umode_t kbatt_is_visible(const void *data, enum hwmon_sensor_types type,
                                u32 attr, int channel)
{
        if (channel == 0 && attr == hwmon_in_min_alarm)
                return 0444;

        return 0;
}

static const struct hwmon_channel_info *kbatt_info[] = {
        HWMON_CHANNEL_INFO(in,
                           /* 0: input minimum alarm channel */
                           HWMON_I_MIN_ALARM),
        NULL
};

static const struct hwmon_ops kbatt_hwmon_ops = {
        .is_visible = kbatt_is_visible,
        .read = kbatt_read,
};

static const struct hwmon_chip_info kbatt_chip_info = {
        .ops = &kbatt_hwmon_ops,
        .info = kbatt_info,
};

static int kbatt_probe(struct auxiliary_device *auxdev,
                       const struct auxiliary_device_id *id)
{
        struct keba_batt_auxdev *kbatt_auxdev =
                container_of(auxdev, struct keba_batt_auxdev, auxdev);
        struct device *dev = &auxdev->dev;
        struct device *hwmon_dev;
        struct kbatt *kbatt;
        int retval;

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

        retval = devm_mutex_init(dev, &kbatt->lock);
        if (retval)
                return retval;

        kbatt->base = devm_ioremap_resource(dev, &kbatt_auxdev->io);
        if (IS_ERR(kbatt->base))
                return PTR_ERR(kbatt->base);

        hwmon_dev = devm_hwmon_device_register_with_info(dev, KBATT, kbatt,
                                                         &kbatt_chip_info,
                                                         NULL);
        return PTR_ERR_OR_ZERO(hwmon_dev);
}

static const struct auxiliary_device_id kbatt_devtype_aux[] = {
        { .name = "keba.batt" },
        {}
};
MODULE_DEVICE_TABLE(auxiliary, kbatt_devtype_aux);

static struct auxiliary_driver kbatt_driver_aux = {
        .name = KBATT,
        .id_table = kbatt_devtype_aux,
        .probe = kbatt_probe,
};
module_auxiliary_driver(kbatt_driver_aux);

MODULE_AUTHOR("Petar Bojanic <boja@keba.com>");
MODULE_AUTHOR("Gerhard Engleder <eg@keba.com>");
MODULE_DESCRIPTION("KEBA battery monitoring controller driver");
MODULE_LICENSE("GPL");