// SPDX-License-Identifier: GPL-2.0-only
/*
 * MMC5983 - MEMSIC 3-axis Magnetic Sensor
 *
 * Copyright (c) 2026, Vlad Kulikov <vlad.kulikov.c@gmail.com>
 *
 * IIO driver for MMC5983
 */

#include <linux/array_size.h>
#include <linux/bits.h>
#include <linux/cleanup.h>
#include <linux/delay.h>
#include <linux/dev_printk.h>
#include <linux/err.h>
#include <linux/i2c.h>
#include <linux/iio/iio.h>
#include <linux/module.h>
#include <linux/mutex.h>
#include <linux/regmap.h>
#include <linux/time.h>
#include <linux/types.h>

#define MMC5983_REG_XOUT0       0x00
#define MMC5983_REG_XOUT1       0x01
#define MMC5983_REG_YOUT0       0x02
#define MMC5983_REG_YOUT1       0x03
#define MMC5983_REG_ZOUT0       0x04
#define MMC5983_REG_ZOUT1       0x05
#define MMC5983_REG_XYZOUT2     0x06

#define MMC5983_REG_STATUS      0x08

#define MMC5983_REG_CTRL0       0x09
#define MMC5983_REG_CTRL1       0x0A
#define MMC5983_REG_CTRL2       0x0B
#define MMC5983_REG_CTRL3       0x0C

#define MMC5983_REG_ID          0x2F

#define MMC5983_PRODUCT_ID      0x30

#define MMC5983_STATUS_MEAS_M_DONE_BIT  BIT(0)
#define MMC5983_STATUS_OTP_RD_DONE_BIT  BIT(4)

#define MMC5983_CTRL0_TM_M_BIT          BIT(0)
#define MMC5983_CTRL0_SET_BIT           BIT(3)
#define MMC5983_CTRL0_RESET_BIT         BIT(4)
#define MMC5983_CTRL0_OTP_RD_BIT        BIT(6)

#define MMC5983_CTRL1_SW_RST_BIT        BIT(7)

enum mmc5983_axis {
        MMC5983_AXIS_X,
        MMC5983_AXIS_Y,
        MMC5983_AXIS_Z,
};

struct mmc5983_data {
        struct regmap *regmap;
        /* Protects chip access during SET/RESET measurement sequence */
        struct mutex mutex;
};

#define MMC5983_CHANNEL(_axis) { \
        .type = IIO_MAGN, \
        .modified = 1, \
        .channel2 = IIO_MOD_##_axis, \
        .address = MMC5983_AXIS_##_axis, \
        .info_mask_separate = BIT(IIO_CHAN_INFO_RAW), \
        .info_mask_shared_by_type = BIT(IIO_CHAN_INFO_SCALE), \
}

static const struct iio_chan_spec mmc5983_channels[] = {
        MMC5983_CHANNEL(X),
        MMC5983_CHANNEL(Y),
        MMC5983_CHANNEL(Z),
};

static int mmc5983_pulse_coil(struct mmc5983_data *data, unsigned int coil_bit)
{
        int ret;

        ret = regmap_write(data->regmap, MMC5983_REG_CTRL0, coil_bit);
        if (ret)
                return ret;

        /*
         * Datasheet page 15: SET/RESET coil pulse is 500 ns.
         * Vendor sample code waits 500 us before the next operation.
         */
        fsleep(500);

        return 0;
}

static int mmc5983_take_measurement(struct mmc5983_data *data, int m[3])
{
        unsigned int status;
        u8 buf[7];
        int ret;

        ret = regmap_write(data->regmap, MMC5983_REG_CTRL0,
                           MMC5983_CTRL0_TM_M_BIT);
        if (ret)
                return ret;

        /*
         * Datasheet page 15: measurement time is 8 ms at BW=00 (default,
         * slowest setting). Use a 50 ms timeout for margin.
         */
        ret = regmap_read_poll_timeout(data->regmap, MMC5983_REG_STATUS,
                                       status,
                                       status & MMC5983_STATUS_MEAS_M_DONE_BIT,
                                       10 * USEC_PER_MSEC,
                                       50 * USEC_PER_MSEC);
        if (ret)
                return ret;

        ret = regmap_bulk_read(data->regmap, MMC5983_REG_XOUT0, buf,
                               sizeof(buf));
        if (ret)
                return ret;

        m[0] = (buf[0] << 10) | (buf[1] << 2) | ((buf[6] >> 6) & 0x3);
        m[1] = (buf[2] << 10) | (buf[3] << 2) | ((buf[6] >> 4) & 0x3);
        m[2] = (buf[4] << 10) | (buf[5] << 2) | ((buf[6] >> 2) & 0x3);

        return 0;
}

static int mmc5983_read_raw(struct iio_dev *indio_dev,
                             const struct iio_chan_spec *chan, int *val,
                             int *val2, long mask)
{
        struct mmc5983_data *data = iio_priv(indio_dev);
        int m1[3], m2[3];
        int ret;

        switch (mask) {
        case IIO_CHAN_INFO_RAW: {
                guard(mutex)(&data->mutex);

                /* SET: magnetize sensor elements in forward direction */
                ret = mmc5983_pulse_coil(data, MMC5983_CTRL0_SET_BIT);
                if (ret)
                        return ret;

                ret = mmc5983_take_measurement(data, m1);
                if (ret)
                        return ret;

                /* RESET: magnetize sensor elements in reverse direction */
                ret = mmc5983_pulse_coil(data, MMC5983_CTRL0_RESET_BIT);
                if (ret)
                        return ret;

                ret = mmc5983_take_measurement(data, m2);
                if (ret)
                        return ret;

                *val = (m1[chan->address] - m2[chan->address]) / 2;
                return IIO_VAL_INT;
        }
        case IIO_CHAN_INFO_SCALE:
                *val = 0;
                *val2 = 61035;
                return IIO_VAL_INT_PLUS_NANO;
        default:
                return -EINVAL;
        }
}

static const struct iio_info mmc5983_info = {
        .read_raw = mmc5983_read_raw,
};

static bool mmc5983_is_writeable_reg(struct device *dev, unsigned int reg)
{
        switch (reg) {
        case MMC5983_REG_CTRL0:
        case MMC5983_REG_CTRL1:
        case MMC5983_REG_CTRL2:
        case MMC5983_REG_CTRL3:
                return true;
        default:
                return false;
        }
}

static bool mmc5983_is_readable_reg(struct device *dev, unsigned int reg)
{
        switch (reg) {
        case MMC5983_REG_XOUT0:
        case MMC5983_REG_XOUT1:
        case MMC5983_REG_YOUT0:
        case MMC5983_REG_YOUT1:
        case MMC5983_REG_ZOUT0:
        case MMC5983_REG_ZOUT1:
        case MMC5983_REG_XYZOUT2:
        case MMC5983_REG_STATUS:
        case MMC5983_REG_CTRL0:
        case MMC5983_REG_CTRL1:
        case MMC5983_REG_CTRL2:
        case MMC5983_REG_CTRL3:
        case MMC5983_REG_ID:
                return true;
        default:
                return false;
        }
}

static bool mmc5983_is_volatile_reg(struct device *dev, unsigned int reg)
{
        switch (reg) {
        case MMC5983_REG_XOUT0:
        case MMC5983_REG_XOUT1:
        case MMC5983_REG_YOUT0:
        case MMC5983_REG_YOUT1:
        case MMC5983_REG_ZOUT0:
        case MMC5983_REG_ZOUT1:
        case MMC5983_REG_XYZOUT2:
        case MMC5983_REG_STATUS:
        case MMC5983_REG_CTRL0:
        case MMC5983_REG_CTRL1:
                return true;
        default:
                return false;
        }
}

static const struct regmap_config mmc5983_regmap_config = {
        .name = "mmc5983_regmap",
        .reg_bits = 8,
        .val_bits = 8,
        .max_register = MMC5983_REG_ID,
        .writeable_reg = mmc5983_is_writeable_reg,
        .readable_reg = mmc5983_is_readable_reg,
        .volatile_reg = mmc5983_is_volatile_reg,
};

static int mmc5983_init(struct mmc5983_data *data)
{
        struct regmap *regmap = data->regmap;
        struct device *dev = regmap_get_device(regmap);
        unsigned int reg_id, status;
        int ret;

        ret = regmap_read(regmap, MMC5983_REG_ID, &reg_id);
        if (ret)
                return dev_err_probe(dev, ret, "Error reading product id\n");

        if (reg_id != MMC5983_PRODUCT_ID)
                dev_info(dev, "unexpected product id 0x%02x\n", reg_id);

        ret = regmap_write(regmap, MMC5983_REG_CTRL1, MMC5983_CTRL1_SW_RST_BIT);
        if (ret)
                return ret;

        /* Datasheet page 15: power-on time after SW_RST is 10 ms */
        fsleep(10 * USEC_PER_MSEC);

        ret = regmap_write(regmap, MMC5983_REG_CTRL0, MMC5983_CTRL0_OTP_RD_BIT);
        if (ret)
                return ret;

        /*
         * Datasheet page 15: OTP read completes and self-clears. No separate
         * OTP refresh timeout is specified, so use the 10 ms power-on time as
         * a conservative upper bound.
         */
        ret = regmap_read_poll_timeout(regmap, MMC5983_REG_STATUS, status,
                                       status & MMC5983_STATUS_OTP_RD_DONE_BIT,
                                       USEC_PER_MSEC,
                                       10 * USEC_PER_MSEC);
        if (ret)
                return ret;

        /* SET: magnetize sensor elements in forward direction */
        ret = mmc5983_pulse_coil(data, MMC5983_CTRL0_SET_BIT);
        if (ret)
                return ret;

        /* RESET: magnetize sensor elements in reverse direction */
        return mmc5983_pulse_coil(data, MMC5983_CTRL0_RESET_BIT);
}

static int mmc5983_probe(struct i2c_client *i2c)
{
        struct device *dev = &i2c->dev;
        struct mmc5983_data *data;
        struct iio_dev *indio_dev;
        int ret;

        indio_dev = devm_iio_device_alloc(dev, sizeof(*data));
        if (!indio_dev)
                return -ENOMEM;

        data = iio_priv(indio_dev);

        ret = devm_mutex_init(dev, &data->mutex);
        if (ret)
                return ret;

        data->regmap = devm_regmap_init_i2c(i2c, &mmc5983_regmap_config);
        if (IS_ERR(data->regmap))
                return dev_err_probe(dev, PTR_ERR(data->regmap),
                                     "failed to allocate register map\n");

        indio_dev->info = &mmc5983_info;
        indio_dev->modes = INDIO_DIRECT_MODE;
        indio_dev->name = "mmc5983";
        indio_dev->channels = mmc5983_channels;
        indio_dev->num_channels = ARRAY_SIZE(mmc5983_channels);

        ret = mmc5983_init(data);
        if (ret)
                return dev_err_probe(dev, ret, "mmc5983 chip init failed\n");

        return devm_iio_device_register(dev, indio_dev);
}

static const struct of_device_id mmc5983_of_match[] = {
        { .compatible = "memsic,mmc5983" },
        { }
};
MODULE_DEVICE_TABLE(of, mmc5983_of_match);

static const struct i2c_device_id mmc5983_id[] = {
        { "mmc5983" },
        { }
};
MODULE_DEVICE_TABLE(i2c, mmc5983_id);

static struct i2c_driver mmc5983_driver = {
        .driver = {
                .name = "mmc5983",
                .of_match_table = mmc5983_of_match,
        },
        .probe = mmc5983_probe,
        .id_table = mmc5983_id,
};
module_i2c_driver(mmc5983_driver);

MODULE_AUTHOR("Vladislav Kulikov <vlad.kulikov.c@gmail.com>");
MODULE_DESCRIPTION("MEMSIC MMC5983 magnetic sensor driver");
MODULE_LICENSE("GPL");