// SPDX-License-Identifier: GPL-2.0-or-later
/*
 * Copyright (C) 2023 Anshul Dalal <anshulusr@gmail.com>
 *
 * Driver for Microchip MCP4801, MCP4802, MCP4811, MCP4812, MCP4821 and MCP4822
 *
 * Based on the work of:
 *      Michael Welling (MCP4922 Driver)
 *
 * Datasheet:
 *      MCP48x1: https://ww1.microchip.com/downloads/en/DeviceDoc/22244B.pdf
 *      MCP48x2: https://ww1.microchip.com/downloads/en/DeviceDoc/20002249B.pdf
 *
 * TODO:
 *      - Regulator control
 */

#include <linux/module.h>
#include <linux/spi/spi.h>
#include <linux/units.h>

#include <linux/iio/iio.h>
#include <linux/iio/types.h>

#include <linux/unaligned.h>

#define MCP4821_ACTIVE_MODE BIT(12)
#define MCP4821_GAIN_ENABLE BIT(13)
#define MCP4802_SECOND_CHAN BIT(15)

/* DAC uses an internal Voltage reference of 2.048V */
#define MCP4821_VREF_MV 2048

/*
 * MCP48xx DAC output:
 *
 * Vout = (Vref * D / 2^N) * G
 *
 * where:
 *  - Vref = 2.048V (internal reference)
 *  - N = DAC resolution (12 bits for MCP4821)
 *  - G = gain selection:
 *        1x when GA bit = 1
 *        2x when GA bit = 0 (default)
 *
 * Therefore full-scale voltage is:
 *  - 1x gain: 2.048V
 *  - 2x gain: 4.096V
 *
 * Scale = Vfull-scale / 2^N
 */

enum mcp4821_supported_device_ids {
        ID_MCP4801,
        ID_MCP4802,
        ID_MCP4811,
        ID_MCP4812,
        ID_MCP4821,
        ID_MCP4822,
};

struct mcp4821_state {
        struct spi_device *spi;
        u16 dac_value[2];
        int gain;
        int scale_avail[4];
};

struct mcp4821_chip_info {
        const char *name;
        int num_channels;
        const struct iio_chan_spec channels[2];
};

#define MCP4821_CHAN(channel_id, resolution)                          \
        {                                                             \
                .type = IIO_VOLTAGE, .output = 1, .indexed = 1,       \
                .channel = (channel_id),                              \
                .info_mask_separate = BIT(IIO_CHAN_INFO_RAW),         \
                .info_mask_shared_by_type = BIT(IIO_CHAN_INFO_SCALE), \
                .info_mask_shared_by_type_available = BIT(IIO_CHAN_INFO_SCALE), \
                .scan_type = {                                        \
                        .realbits = (resolution),                     \
                        .shift = 12 - (resolution),                   \
                },                                                    \
        }

static const struct mcp4821_chip_info mcp4821_chip_info_table[6] = {
        [ID_MCP4801] = {
                        .name = "mcp4801",
                        .num_channels = 1,
                        .channels = {
                                MCP4821_CHAN(0, 8),
                        },
        },
        [ID_MCP4802] = {
                        .name = "mcp4802",
                        .num_channels = 2,
                        .channels = {
                                MCP4821_CHAN(0, 8),
                                MCP4821_CHAN(1, 8),
                        },
        },
        [ID_MCP4811] = {
                        .name = "mcp4811",
                        .num_channels = 1,
                        .channels = {
                                MCP4821_CHAN(0, 10),
                        },
        },
        [ID_MCP4812] = {
                        .name = "mcp4812",
                        .num_channels = 2,
                        .channels = {
                                MCP4821_CHAN(0, 10),
                                MCP4821_CHAN(1, 10),
                        },
        },
        [ID_MCP4821] = {
                        .name = "mcp4821",
                        .num_channels = 1,
                        .channels = {
                                MCP4821_CHAN(0, 12),
                        },
        },
        [ID_MCP4822] = {
                        .name = "mcp4822",
                        .num_channels = 2,
                        .channels = {
                                MCP4821_CHAN(0, 12),
                                MCP4821_CHAN(1, 12),
                        },
        },
};

static int mcp4821_read_raw(struct iio_dev *indio_dev,
                            struct iio_chan_spec const *chan, int *val,
                            int *val2, long mask)
{
        struct mcp4821_state *state = iio_priv(indio_dev);

        switch (mask) {
        case IIO_CHAN_INFO_RAW:
                *val = state->dac_value[chan->channel];
                return IIO_VAL_INT;

        case IIO_CHAN_INFO_SCALE:
                *val = MCP4821_VREF_MV * state->gain;
                *val2 = chan->scan_type.realbits;
                return IIO_VAL_FRACTIONAL_LOG2;
        default:
                return -EINVAL;
        }
}

static void mcp4821_calc_scale(int vref_mv, int resolution,
                                int *val, int *val2)
{
        s64 tmp;
        int micro;

        tmp = (s64)vref_mv * MICRO >> resolution;
        *val = div_s64_rem(tmp, MICRO, &micro);
        *val2 = micro;
}

static int mcp4821_write_raw(struct iio_dev *indio_dev,
                             struct iio_chan_spec const *chan, int val,
                             int val2, long mask)
{
        struct mcp4821_state *state = iio_priv(indio_dev);
        u16 write_val;
        __be16 write_buffer;
        int ret;
        int v, v2;

        switch (mask) {
        case IIO_CHAN_INFO_RAW:

                if (val2 != 0)
                        return -EINVAL;

                if (val < 0 || val >= BIT(chan->scan_type.realbits))
                        return -EINVAL;

                write_val = MCP4821_ACTIVE_MODE | val << chan->scan_type.shift;
                if (chan->channel)
                        write_val |= MCP4802_SECOND_CHAN;

                /* GA bit = 1 -> 1x gain */
                if (state->gain == 1)
                        write_val |= MCP4821_GAIN_ENABLE;

                write_buffer = cpu_to_be16(write_val);
                ret = spi_write(state->spi, &write_buffer, sizeof(write_buffer));
                if (ret) {
                        dev_err(&state->spi->dev, "Failed to write to device: %d", ret);
                        return ret;
                }

                state->dac_value[chan->channel] = val;
                return 0;

        case IIO_CHAN_INFO_SCALE:
                mcp4821_calc_scale(MCP4821_VREF_MV, chan->scan_type.realbits, &v, &v2);
                if (val == v && val2 == v2) {
                        state->gain = 1;
                        return 0;
                }

                mcp4821_calc_scale(MCP4821_VREF_MV * 2,
                                chan->scan_type.realbits, &v, &v2);
                if (val == v && val2 == v2) {
                        state->gain = 2;
                        return 0;
                }
                return -EINVAL;
        default:
                return -EINVAL;
        }
}

static inline void mcp4821_init_avail_gain(struct mcp4821_state *state,
                                int resolution)
{
        state->scale_avail[0] = MCP4821_VREF_MV;
        state->scale_avail[1] = resolution;
        state->scale_avail[2] = MCP4821_VREF_MV * 2;
        state->scale_avail[3] = resolution;
}

static int mcp4821_read_avail(struct iio_dev *indio_dev,
                             struct iio_chan_spec const *chan,
                             const int **vals, int *type, int *length,
                             long info)
{
        struct mcp4821_state *state = iio_priv(indio_dev);

        switch (info) {
        case IIO_CHAN_INFO_SCALE:
                *vals = state->scale_avail;
                *type = IIO_VAL_FRACTIONAL_LOG2;
                *length = ARRAY_SIZE(state->scale_avail);
                return IIO_AVAIL_LIST;
        default:
                return -EINVAL;
        }
}

static const struct iio_info mcp4821_info = {
        .read_raw = &mcp4821_read_raw,
        .write_raw = &mcp4821_write_raw,
        .read_avail = &mcp4821_read_avail,
};

static int mcp4821_probe(struct spi_device *spi)
{
        struct iio_dev *indio_dev;
        struct mcp4821_state *state;
        const struct mcp4821_chip_info *info;

        indio_dev = devm_iio_device_alloc(&spi->dev, sizeof(*state));
        if (indio_dev == NULL)
                return -ENOMEM;

        state = iio_priv(indio_dev);
        state->spi = spi;

        /* default gain is 2x */
        state->gain = 2;
        info = spi_get_device_match_data(spi);
        indio_dev->name = info->name;
        indio_dev->info = &mcp4821_info;
        indio_dev->modes = INDIO_DIRECT_MODE;
        indio_dev->channels = info->channels;
        indio_dev->num_channels = info->num_channels;
        mcp4821_init_avail_gain(state, info->channels[0].scan_type.realbits);

        return devm_iio_device_register(&spi->dev, indio_dev);
}

#define MCP4821_COMPATIBLE(of_compatible, id)        \
        {                                            \
                .compatible = of_compatible,         \
                .data = &mcp4821_chip_info_table[id] \
        }

static const struct of_device_id mcp4821_of_table[] = {
        MCP4821_COMPATIBLE("microchip,mcp4801", ID_MCP4801),
        MCP4821_COMPATIBLE("microchip,mcp4802", ID_MCP4802),
        MCP4821_COMPATIBLE("microchip,mcp4811", ID_MCP4811),
        MCP4821_COMPATIBLE("microchip,mcp4812", ID_MCP4812),
        MCP4821_COMPATIBLE("microchip,mcp4821", ID_MCP4821),
        MCP4821_COMPATIBLE("microchip,mcp4822", ID_MCP4822),
        { }
};
MODULE_DEVICE_TABLE(of, mcp4821_of_table);

static const struct spi_device_id mcp4821_id_table[] = {
        { "mcp4801", (kernel_ulong_t)&mcp4821_chip_info_table[ID_MCP4801]},
        { "mcp4802", (kernel_ulong_t)&mcp4821_chip_info_table[ID_MCP4802]},
        { "mcp4811", (kernel_ulong_t)&mcp4821_chip_info_table[ID_MCP4811]},
        { "mcp4812", (kernel_ulong_t)&mcp4821_chip_info_table[ID_MCP4812]},
        { "mcp4821", (kernel_ulong_t)&mcp4821_chip_info_table[ID_MCP4821]},
        { "mcp4822", (kernel_ulong_t)&mcp4821_chip_info_table[ID_MCP4822]},
        { }
};
MODULE_DEVICE_TABLE(spi, mcp4821_id_table);

static struct spi_driver mcp4821_driver = {
        .driver = {
                .name = "mcp4821",
                .of_match_table = mcp4821_of_table,
        },
        .probe = mcp4821_probe,
        .id_table = mcp4821_id_table,
};
module_spi_driver(mcp4821_driver);

MODULE_AUTHOR("Anshul Dalal <anshulusr@gmail.com>");
MODULE_DESCRIPTION("Microchip MCP4821 DAC Driver");
MODULE_LICENSE("GPL");