// SPDX-License-Identifier: GPL-2.0
/*
 * PNI RM3100 3-axis geomagnetic sensor driver core.
 *
 * Copyright (C) 2018 Song Qiang <songqiang1304521@gmail.com>
 *
 * User Manual available at
 * <https://www.pnicorp.com/download/rm3100-user-manual/>
 *
 * TODO: event generation, pm.
 */

#include <linux/delay.h>
#include <linux/interrupt.h>
#include <linux/module.h>
#include <linux/slab.h>

#include <linux/iio/buffer.h>
#include <linux/iio/iio.h>
#include <linux/iio/sysfs.h>
#include <linux/iio/trigger.h>
#include <linux/iio/triggered_buffer.h>
#include <linux/iio/trigger_consumer.h>

#include <linux/unaligned.h>

#include "rm3100.h"

/* Cycle Count Registers. */
#define RM3100_REG_CC_X                 0x05
#define RM3100_REG_CC_Y                 0x07
#define RM3100_REG_CC_Z                 0x09

/* Poll Measurement Mode register. */
#define RM3100_REG_POLL                 0x00
#define         RM3100_POLL_X           BIT(4)
#define         RM3100_POLL_Y           BIT(5)
#define         RM3100_POLL_Z           BIT(6)

/* Continuous Measurement Mode register. */
#define RM3100_REG_CMM                  0x01
#define         RM3100_CMM_START        BIT(0)
#define         RM3100_CMM_X            BIT(4)
#define         RM3100_CMM_Y            BIT(5)
#define         RM3100_CMM_Z            BIT(6)

/* TiMe Rate Configuration register. */
#define RM3100_REG_TMRC                 0x0B
#define RM3100_TMRC_OFFSET              0x92

/* Result Status register. */
#define RM3100_REG_STATUS               0x34
#define         RM3100_STATUS_DRDY      BIT(7)

/* Measurement result registers. */
#define RM3100_REG_MX2                  0x24
#define RM3100_REG_MY2                  0x27
#define RM3100_REG_MZ2                  0x2a

#define RM3100_W_REG_START              RM3100_REG_POLL
#define RM3100_W_REG_END                RM3100_REG_TMRC
#define RM3100_R_REG_START              RM3100_REG_POLL
#define RM3100_R_REG_END                RM3100_REG_STATUS
#define RM3100_V_REG_START              RM3100_REG_POLL
#define RM3100_V_REG_END                RM3100_REG_STATUS

/*
 * This is computed by hand, is the sum of channel storage bits and padding
 * bits, which is 4+4+4+12=24 in here.
 */
#define RM3100_SCAN_BYTES               24

#define RM3100_CMM_AXIS_SHIFT           4

struct rm3100_data {
        struct regmap *regmap;
        struct completion measuring_done;
        bool use_interrupt;
        int conversion_time;
        int scale;
        /* Ensure naturally aligned timestamp */
        u8 buffer[RM3100_SCAN_BYTES] __aligned(8);
        struct iio_trigger *drdy_trig;

        /*
         * This lock is for protecting the consistency of series of i2c
         * operations, that is, to make sure a measurement process will
         * not be interrupted by a set frequency operation, which should
         * be taken where a series of i2c operation starts, released where
         * the operation ends.
         */
        struct mutex lock;
};

static const struct regmap_range rm3100_readable_ranges[] = {
        regmap_reg_range(RM3100_R_REG_START, RM3100_R_REG_END),
};

const struct regmap_access_table rm3100_readable_table = {
        .yes_ranges = rm3100_readable_ranges,
        .n_yes_ranges = ARRAY_SIZE(rm3100_readable_ranges),
};
EXPORT_SYMBOL_NS_GPL(rm3100_readable_table, "IIO_RM3100");

static const struct regmap_range rm3100_writable_ranges[] = {
        regmap_reg_range(RM3100_W_REG_START, RM3100_W_REG_END),
};

const struct regmap_access_table rm3100_writable_table = {
        .yes_ranges = rm3100_writable_ranges,
        .n_yes_ranges = ARRAY_SIZE(rm3100_writable_ranges),
};
EXPORT_SYMBOL_NS_GPL(rm3100_writable_table, "IIO_RM3100");

static const struct regmap_range rm3100_volatile_ranges[] = {
        regmap_reg_range(RM3100_V_REG_START, RM3100_V_REG_END),
};

const struct regmap_access_table rm3100_volatile_table = {
        .yes_ranges = rm3100_volatile_ranges,
        .n_yes_ranges = ARRAY_SIZE(rm3100_volatile_ranges),
};
EXPORT_SYMBOL_NS_GPL(rm3100_volatile_table, "IIO_RM3100");

static irqreturn_t rm3100_thread_fn(int irq, void *d)
{
        struct iio_dev *indio_dev = d;
        struct rm3100_data *data = iio_priv(indio_dev);

        /*
         * Write operation to any register or read operation
         * to first byte of results will clear the interrupt.
         */
        regmap_write(data->regmap, RM3100_REG_POLL, 0);

        return IRQ_HANDLED;
}

static irqreturn_t rm3100_irq_handler(int irq, void *d)
{
        struct iio_dev *indio_dev = d;
        struct rm3100_data *data = iio_priv(indio_dev);

        if (!iio_buffer_enabled(indio_dev))
                complete(&data->measuring_done);
        else
                iio_trigger_poll(data->drdy_trig);

        return IRQ_WAKE_THREAD;
}

static int rm3100_wait_measurement(struct rm3100_data *data)
{
        struct regmap *regmap = data->regmap;
        unsigned int val;
        int tries = 20;
        int ret;

        /*
         * A read cycle of 400kbits i2c bus is about 20us, plus the time
         * used for scheduling, a read cycle of fast mode of this device
         * can reach 1.7ms, it may be possible for data to arrive just
         * after we check the RM3100_REG_STATUS. In this case, irq_handler is
         * called before measuring_done is reinitialized, it will wait
         * forever for data that has already been ready.
         * Reinitialize measuring_done before looking up makes sure we
         * will always capture interrupt no matter when it happens.
         */
        if (data->use_interrupt)
                reinit_completion(&data->measuring_done);

        ret = regmap_read(regmap, RM3100_REG_STATUS, &val);
        if (ret < 0)
                return ret;

        if ((val & RM3100_STATUS_DRDY) != RM3100_STATUS_DRDY) {
                if (data->use_interrupt) {
                        ret = wait_for_completion_timeout(&data->measuring_done,
                                msecs_to_jiffies(data->conversion_time));
                        if (!ret)
                                return -ETIMEDOUT;
                } else {
                        do {
                                usleep_range(1000, 5000);

                                ret = regmap_read(regmap, RM3100_REG_STATUS,
                                                  &val);
                                if (ret < 0)
                                        return ret;

                                if (val & RM3100_STATUS_DRDY)
                                        break;
                        } while (--tries);
                        if (!tries)
                                return -ETIMEDOUT;
                }
        }
        return 0;
}

static int rm3100_read_mag(struct rm3100_data *data, int idx, int *val)
{
        struct regmap *regmap = data->regmap;
        u8 buffer[3];
        int ret;

        mutex_lock(&data->lock);
        ret = regmap_write(regmap, RM3100_REG_POLL, BIT(4 + idx));
        if (ret < 0)
                goto unlock_return;

        ret = rm3100_wait_measurement(data);
        if (ret < 0)
                goto unlock_return;

        ret = regmap_bulk_read(regmap, RM3100_REG_MX2 + 3 * idx, buffer, 3);
        if (ret < 0)
                goto unlock_return;
        mutex_unlock(&data->lock);

        *val = sign_extend32(get_unaligned_be24(&buffer[0]), 23);

        return IIO_VAL_INT;

unlock_return:
        mutex_unlock(&data->lock);
        return ret;
}

#define RM3100_CHANNEL(axis, idx)                                       \
        {                                                               \
                .type = IIO_MAGN,                                       \
                .modified = 1,                                          \
                .channel2 = IIO_MOD_##axis,                             \
                .info_mask_separate = BIT(IIO_CHAN_INFO_RAW),           \
                .info_mask_shared_by_type = BIT(IIO_CHAN_INFO_SCALE) |  \
                        BIT(IIO_CHAN_INFO_SAMP_FREQ),                   \
                .scan_index = idx,                                      \
                .scan_type = {                                          \
                        .sign = 's',                                    \
                        .realbits = 24,                                 \
                        .storagebits = 32,                              \
                        .shift = 8,                                     \
                        .endianness = IIO_BE,                           \
                },                                                      \
        }

static const struct iio_chan_spec rm3100_channels[] = {
        RM3100_CHANNEL(X, 0),
        RM3100_CHANNEL(Y, 1),
        RM3100_CHANNEL(Z, 2),
        IIO_CHAN_SOFT_TIMESTAMP(3),
};

static IIO_CONST_ATTR_SAMP_FREQ_AVAIL(
        "600 300 150 75 37 18 9 4.5 2.3 1.2 0.6 0.3 0.015 0.075"
);

static struct attribute *rm3100_attributes[] = {
        &iio_const_attr_sampling_frequency_available.dev_attr.attr,
        NULL,
};

static const struct attribute_group rm3100_attribute_group = {
        .attrs = rm3100_attributes,
};

#define RM3100_SAMP_NUM                 14

/*
 * Frequency : rm3100_samp_rates[][0].rm3100_samp_rates[][1]Hz.
 * Time between reading: rm3100_sam_rates[][2]ms.
 * The first one is actually 1.7ms.
 */
static const int rm3100_samp_rates[RM3100_SAMP_NUM][3] = {
        {600, 0, 2}, {300, 0, 3}, {150, 0, 7}, {75, 0, 13}, {37, 0, 27},
        {18, 0, 55}, {9, 0, 110}, {4, 500000, 220}, {2, 300000, 440},
        {1, 200000, 800}, {0, 600000, 1600}, {0, 300000, 3300},
        {0, 15000, 6700},  {0, 75000, 13000}
};

static int rm3100_get_samp_freq(struct rm3100_data *data, int *val, int *val2)
{
        unsigned int tmp;
        int ret;

        mutex_lock(&data->lock);
        ret = regmap_read(data->regmap, RM3100_REG_TMRC, &tmp);
        mutex_unlock(&data->lock);
        if (ret < 0)
                return ret;
        *val = rm3100_samp_rates[tmp - RM3100_TMRC_OFFSET][0];
        *val2 = rm3100_samp_rates[tmp - RM3100_TMRC_OFFSET][1];

        return IIO_VAL_INT_PLUS_MICRO;
}

static int rm3100_set_cycle_count(struct rm3100_data *data, int val)
{
        int ret;
        u8 i;

        for (i = 0; i < 3; i++) {
                ret = regmap_write(data->regmap, RM3100_REG_CC_X + 2 * i, val);
                if (ret < 0)
                        return ret;
        }

        /*
         * The scale of this sensor depends on the cycle count value, these
         * three values are corresponding to the cycle count value 50, 100,
         * 200. scale = output / gain * 10^4.
         */
        switch (val) {
        case 50:
                data->scale = 500;
                break;
        case 100:
                data->scale = 263;
                break;
        /*
         * case 200:
         * This function will never be called by users' code, so here we
         * assume that it will never get a wrong parameter.
         */
        default:
                data->scale = 133;
        }

        return 0;
}

static int rm3100_set_samp_freq(struct iio_dev *indio_dev, int val, int val2)
{
        struct rm3100_data *data = iio_priv(indio_dev);
        struct regmap *regmap = data->regmap;
        unsigned int cycle_count;
        int ret;
        int i;

        mutex_lock(&data->lock);
        /* All cycle count registers use the same value. */
        ret = regmap_read(regmap, RM3100_REG_CC_X, &cycle_count);
        if (ret < 0)
                goto unlock_return;

        for (i = 0; i < RM3100_SAMP_NUM; i++) {
                if (val == rm3100_samp_rates[i][0] &&
                    val2 == rm3100_samp_rates[i][1])
                        break;
        }
        if (i == RM3100_SAMP_NUM) {
                ret = -EINVAL;
                goto unlock_return;
        }

        ret = regmap_write(regmap, RM3100_REG_TMRC, i + RM3100_TMRC_OFFSET);
        if (ret < 0)
                goto unlock_return;

        /* Checking if cycle count registers need changing. */
        if (val == 600 && cycle_count == 200) {
                ret = rm3100_set_cycle_count(data, 100);
                if (ret < 0)
                        goto unlock_return;
        } else if (val != 600 && cycle_count == 100) {
                ret = rm3100_set_cycle_count(data, 200);
                if (ret < 0)
                        goto unlock_return;
        }

        if (iio_buffer_enabled(indio_dev)) {
                /* Writing TMRC registers requires CMM reset. */
                ret = regmap_write(regmap, RM3100_REG_CMM, 0);
                if (ret < 0)
                        goto unlock_return;
                ret = regmap_write(data->regmap, RM3100_REG_CMM,
                        (*indio_dev->active_scan_mask & 0x7) <<
                        RM3100_CMM_AXIS_SHIFT | RM3100_CMM_START);
                if (ret < 0)
                        goto unlock_return;
        }
        mutex_unlock(&data->lock);

        data->conversion_time = rm3100_samp_rates[i][2] * 2;
        return 0;

unlock_return:
        mutex_unlock(&data->lock);
        return ret;
}

static int rm3100_read_raw(struct iio_dev *indio_dev,
                           const struct iio_chan_spec *chan,
                           int *val, int *val2, long mask)
{
        struct rm3100_data *data = iio_priv(indio_dev);
        int ret;

        switch (mask) {
        case IIO_CHAN_INFO_RAW:
                if (!iio_device_claim_direct(indio_dev))
                        return -EBUSY;

                ret = rm3100_read_mag(data, chan->scan_index, val);
                iio_device_release_direct(indio_dev);

                return ret;
        case IIO_CHAN_INFO_SCALE:
                *val = 0;
                *val2 = data->scale;

                return IIO_VAL_INT_PLUS_MICRO;
        case IIO_CHAN_INFO_SAMP_FREQ:
                return rm3100_get_samp_freq(data, val, val2);
        default:
                return -EINVAL;
        }
}

static int rm3100_write_raw(struct iio_dev *indio_dev,
                            struct iio_chan_spec const *chan,
                            int val, int val2, long mask)
{
        switch (mask) {
        case IIO_CHAN_INFO_SAMP_FREQ:
                return rm3100_set_samp_freq(indio_dev, val, val2);
        default:
                return -EINVAL;
        }
}

static const struct iio_info rm3100_info = {
        .attrs = &rm3100_attribute_group,
        .read_raw = rm3100_read_raw,
        .write_raw = rm3100_write_raw,
};

static int rm3100_buffer_preenable(struct iio_dev *indio_dev)
{
        struct rm3100_data *data = iio_priv(indio_dev);

        /* Starting channels enabled. */
        return regmap_write(data->regmap, RM3100_REG_CMM,
                (*indio_dev->active_scan_mask & 0x7) << RM3100_CMM_AXIS_SHIFT |
                RM3100_CMM_START);
}

static int rm3100_buffer_postdisable(struct iio_dev *indio_dev)
{
        struct rm3100_data *data = iio_priv(indio_dev);

        return regmap_write(data->regmap, RM3100_REG_CMM, 0);
}

static const struct iio_buffer_setup_ops rm3100_buffer_ops = {
        .preenable = rm3100_buffer_preenable,
        .postdisable = rm3100_buffer_postdisable,
};

static irqreturn_t rm3100_trigger_handler(int irq, void *p)
{
        struct iio_poll_func *pf = p;
        struct iio_dev *indio_dev = pf->indio_dev;
        unsigned long scan_mask = *indio_dev->active_scan_mask;
        unsigned int mask_len = iio_get_masklength(indio_dev);
        struct rm3100_data *data = iio_priv(indio_dev);
        struct regmap *regmap = data->regmap;
        int ret, i, bit;

        mutex_lock(&data->lock);
        switch (scan_mask) {
        case BIT(0) | BIT(1) | BIT(2):
                ret = regmap_bulk_read(regmap, RM3100_REG_MX2, data->buffer, 9);
                mutex_unlock(&data->lock);
                if (ret < 0)
                        goto done;
                /* Convert XXXYYYZZZxxx to XXXxYYYxZZZx. x for paddings. */
                for (i = 2; i > 0; i--)
                        memmove(data->buffer + i * 4, data->buffer + i * 3, 3);
                break;
        case BIT(0) | BIT(1):
                ret = regmap_bulk_read(regmap, RM3100_REG_MX2, data->buffer, 6);
                mutex_unlock(&data->lock);
                if (ret < 0)
                        goto done;
                memmove(data->buffer + 4, data->buffer + 3, 3);
                break;
        case BIT(1) | BIT(2):
                ret = regmap_bulk_read(regmap, RM3100_REG_MY2, data->buffer, 6);
                mutex_unlock(&data->lock);
                if (ret < 0)
                        goto done;
                memmove(data->buffer + 4, data->buffer + 3, 3);
                break;
        case BIT(0) | BIT(2):
                ret = regmap_bulk_read(regmap, RM3100_REG_MX2, data->buffer, 9);
                mutex_unlock(&data->lock);
                if (ret < 0)
                        goto done;
                memmove(data->buffer + 4, data->buffer + 6, 3);
                break;
        default:
                for_each_set_bit(bit, &scan_mask, mask_len) {
                        ret = regmap_bulk_read(regmap, RM3100_REG_MX2 + 3 * bit,
                                               data->buffer, 3);
                        if (ret < 0) {
                                mutex_unlock(&data->lock);
                                goto done;
                        }
                }
                mutex_unlock(&data->lock);
        }
        /*
         * Always using the same buffer so that we wouldn't need to set the
         * paddings to 0 in case of leaking any data.
         */
        iio_push_to_buffers_with_ts(indio_dev, data->buffer, sizeof(data->buffer),
                                    pf->timestamp);
done:
        iio_trigger_notify_done(indio_dev->trig);

        return IRQ_HANDLED;
}

int rm3100_common_probe(struct device *dev, struct regmap *regmap, int irq)
{
        struct iio_dev *indio_dev;
        struct rm3100_data *data;
        unsigned int tmp;
        int ret;
        int samp_rate_index;

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

        data = iio_priv(indio_dev);
        data->regmap = regmap;

        mutex_init(&data->lock);

        indio_dev->name = "rm3100";
        indio_dev->info = &rm3100_info;
        indio_dev->channels = rm3100_channels;
        indio_dev->num_channels = ARRAY_SIZE(rm3100_channels);
        indio_dev->modes = INDIO_DIRECT_MODE;

        if (!irq)
                data->use_interrupt = false;
        else {
                data->use_interrupt = true;

                init_completion(&data->measuring_done);
                ret = devm_request_threaded_irq(dev,
                                                irq,
                                                rm3100_irq_handler,
                                                rm3100_thread_fn,
                                                IRQF_TRIGGER_HIGH |
                                                IRQF_ONESHOT,
                                                indio_dev->name,
                                                indio_dev);
                if (ret < 0) {
                        dev_err(dev, "request irq line failed.\n");
                        return ret;
                }

                data->drdy_trig = devm_iio_trigger_alloc(dev, "%s-drdy%d",
                                                         indio_dev->name,
                                                         iio_device_id(indio_dev));
                if (!data->drdy_trig)
                        return -ENOMEM;

                ret = devm_iio_trigger_register(dev, data->drdy_trig);
                if (ret < 0)
                        return ret;
        }

        ret = devm_iio_triggered_buffer_setup(dev, indio_dev,
                                              &iio_pollfunc_store_time,
                                              rm3100_trigger_handler,
                                              &rm3100_buffer_ops);
        if (ret < 0)
                return ret;

        ret = regmap_read(regmap, RM3100_REG_TMRC, &tmp);
        if (ret < 0)
                return ret;

        samp_rate_index = tmp - RM3100_TMRC_OFFSET;
        if (samp_rate_index < 0 || samp_rate_index >=  RM3100_SAMP_NUM) {
                dev_err(dev, "The value read from RM3100_REG_TMRC is invalid!\n");
                return -EINVAL;
        }
        /* Initializing max wait time, which is double conversion time. */
        data->conversion_time = rm3100_samp_rates[samp_rate_index][2] * 2;

        /* Cycle count values may not be what we want. */
        if ((tmp - RM3100_TMRC_OFFSET) == 0)
                rm3100_set_cycle_count(data, 100);
        else
                rm3100_set_cycle_count(data, 200);

        return devm_iio_device_register(dev, indio_dev);
}
EXPORT_SYMBOL_NS_GPL(rm3100_common_probe, "IIO_RM3100");

MODULE_AUTHOR("Song Qiang <songqiang1304521@gmail.com>");
MODULE_DESCRIPTION("PNI RM3100 3-axis magnetometer i2c driver");
MODULE_LICENSE("GPL v2");