// SPDX-License-Identifier: GPL-2.0
/*
 * Analog Devices AD7292 SPI ADC driver
 *
 * Copyright 2019 Analog Devices Inc.
 */

#include <linux/bitfield.h>
#include <linux/device.h>
#include <linux/module.h>
#include <linux/regulator/consumer.h>
#include <linux/spi/spi.h>

#include <linux/iio/iio.h>

#define ADI_VENDOR_ID 0x0018

/* AD7292 registers definition */
#define AD7292_REG_VENDOR_ID            0x00
#define AD7292_REG_CONF_BANK            0x05
#define AD7292_REG_CONV_COMM            0x0E
#define AD7292_REG_ADC_CH(x)            (0x10 + (x))

/* AD7292 configuration bank subregisters definition */
#define AD7292_BANK_REG_VIN_RNG0        0x10
#define AD7292_BANK_REG_VIN_RNG1        0x11
#define AD7292_BANK_REG_SAMP_MODE       0x12

#define AD7292_RD_FLAG_MSK(x)           (BIT(7) | ((x) & 0x3F))

/* AD7292_REG_ADC_CONVERSION */
#define AD7292_ADC_DATA_MASK            GENMASK(15, 6)
#define AD7292_ADC_DATA(x)              FIELD_GET(AD7292_ADC_DATA_MASK, x)

/* AD7292_CHANNEL_SAMPLING_MODE */
#define AD7292_CH_SAMP_MODE(reg, ch)    (((reg) >> 8) & BIT(ch))

/* AD7292_CHANNEL_VIN_RANGE */
#define AD7292_CH_VIN_RANGE(reg, ch)    ((reg) & BIT(ch))

#define AD7292_VOLTAGE_CHAN(_chan)                                      \
{                                                                       \
        .type = IIO_VOLTAGE,                                            \
        .info_mask_separate = BIT(IIO_CHAN_INFO_RAW) |                  \
                              BIT(IIO_CHAN_INFO_SCALE),                 \
        .indexed = 1,                                                   \
        .channel = _chan,                                               \
}

static const struct iio_chan_spec ad7292_channels[] = {
        AD7292_VOLTAGE_CHAN(0),
        AD7292_VOLTAGE_CHAN(1),
        AD7292_VOLTAGE_CHAN(2),
        AD7292_VOLTAGE_CHAN(3),
        AD7292_VOLTAGE_CHAN(4),
        AD7292_VOLTAGE_CHAN(5),
        AD7292_VOLTAGE_CHAN(6),
        AD7292_VOLTAGE_CHAN(7)
};

static const struct iio_chan_spec ad7292_channels_diff[] = {
        {
                .type = IIO_VOLTAGE,
                .info_mask_separate = BIT(IIO_CHAN_INFO_RAW),
                .indexed = 1,
                .differential = 1,
                .channel = 0,
                .channel2 = 1,
        },
        AD7292_VOLTAGE_CHAN(2),
        AD7292_VOLTAGE_CHAN(3),
        AD7292_VOLTAGE_CHAN(4),
        AD7292_VOLTAGE_CHAN(5),
        AD7292_VOLTAGE_CHAN(6),
        AD7292_VOLTAGE_CHAN(7)
};

struct ad7292_state {
        struct spi_device *spi;
        struct regulator *reg;
        unsigned short vref_mv;

        __be16 d16 ____cacheline_aligned;
        u8 d8[2];
};

static int ad7292_spi_reg_read(struct ad7292_state *st, unsigned int addr)
{
        int ret;

        st->d8[0] = AD7292_RD_FLAG_MSK(addr);

        ret = spi_write_then_read(st->spi, st->d8, 1, &st->d16, 2);
        if (ret < 0)
                return ret;

        return be16_to_cpu(st->d16);
}

static int ad7292_spi_subreg_read(struct ad7292_state *st, unsigned int addr,
                                  unsigned int sub_addr, unsigned int len)
{
        unsigned int shift = 16 - (8 * len);
        int ret;

        st->d8[0] = AD7292_RD_FLAG_MSK(addr);
        st->d8[1] = sub_addr;

        ret = spi_write_then_read(st->spi, st->d8, 2, &st->d16, len);
        if (ret < 0)
                return ret;

        return (be16_to_cpu(st->d16) >> shift);
}

static int ad7292_single_conversion(struct ad7292_state *st,
                                    unsigned int chan_addr)
{
        int ret;

        struct spi_transfer t[] = {
                {
                        .tx_buf = &st->d8,
                        .len = 4,
                        .delay = {
                                .value = 6,
                                .unit = SPI_DELAY_UNIT_USECS
                        },
                }, {
                        .rx_buf = &st->d16,
                        .len = 2,
                },
        };

        st->d8[0] = chan_addr;
        st->d8[1] = AD7292_RD_FLAG_MSK(AD7292_REG_CONV_COMM);

        ret = spi_sync_transfer(st->spi, t, ARRAY_SIZE(t));

        if (ret < 0)
                return ret;

        return be16_to_cpu(st->d16);
}

static int ad7292_vin_range_multiplier(struct ad7292_state *st, int channel)
{
        int samp_mode, range0, range1, factor = 1;

        /*
         * Every AD7292 ADC channel may have its input range adjusted according
         * to the settings at the ADC sampling mode and VIN range subregisters.
         * For a given channel, the minimum input range is equal to Vref, and it
         * may be increased by a multiplier factor of 2 or 4 according to the
         * following rule:
         * If channel is being sampled with respect to AGND:
         *      factor = 4 if VIN range0 and VIN range1 equal 0
         *      factor = 2 if only one of VIN ranges equal 1
         *      factor = 1 if both VIN range0 and VIN range1 equal 1
         * If channel is being sampled with respect to AVDD:
         *      factor = 4 if VIN range0 and VIN range1 equal 0
         *      Behavior is undefined if any of VIN range doesn't equal 0
         */

        samp_mode = ad7292_spi_subreg_read(st, AD7292_REG_CONF_BANK,
                                           AD7292_BANK_REG_SAMP_MODE, 2);

        if (samp_mode < 0)
                return samp_mode;

        range0 = ad7292_spi_subreg_read(st, AD7292_REG_CONF_BANK,
                                        AD7292_BANK_REG_VIN_RNG0, 2);

        if (range0 < 0)
                return range0;

        range1 = ad7292_spi_subreg_read(st, AD7292_REG_CONF_BANK,
                                        AD7292_BANK_REG_VIN_RNG1, 2);

        if (range1 < 0)
                return range1;

        if (AD7292_CH_SAMP_MODE(samp_mode, channel)) {
                /* Sampling with respect to AGND */
                if (!AD7292_CH_VIN_RANGE(range0, channel))
                        factor *= 2;

                if (!AD7292_CH_VIN_RANGE(range1, channel))
                        factor *= 2;

        } else {
                /* Sampling with respect to AVDD */
                if (AD7292_CH_VIN_RANGE(range0, channel) ||
                    AD7292_CH_VIN_RANGE(range1, channel))
                        return -EPERM;

                factor = 4;
        }

        return factor;
}

static int ad7292_read_raw(struct iio_dev *indio_dev,
                           const struct iio_chan_spec *chan,
                           int *val, int *val2, long info)
{
        struct ad7292_state *st = iio_priv(indio_dev);
        unsigned int ch_addr;
        int ret;

        switch (info) {
        case IIO_CHAN_INFO_RAW:
                ch_addr = AD7292_REG_ADC_CH(chan->channel);
                ret = ad7292_single_conversion(st, ch_addr);
                if (ret < 0)
                        return ret;

                *val = AD7292_ADC_DATA(ret);

                return IIO_VAL_INT;
        case IIO_CHAN_INFO_SCALE:
                /*
                 * To convert a raw value to standard units, the IIO defines
                 * this formula: Scaled value = (raw + offset) * scale.
                 * For the scale to be a correct multiplier for (raw + offset),
                 * it must be calculated as the input range divided by the
                 * number of possible distinct input values. Given the ADC data
                 * is 10 bit long, it may assume 2^10 distinct values.
                 * Hence, scale = range / 2^10. The IIO_VAL_FRACTIONAL_LOG2
                 * return type indicates to the IIO API to divide *val by 2 to
                 * the power of *val2 when returning from read_raw.
                 */

                ret = ad7292_vin_range_multiplier(st, chan->channel);
                if (ret < 0)
                        return ret;

                *val = st->vref_mv * ret;
                *val2 = 10;
                return IIO_VAL_FRACTIONAL_LOG2;
        default:
                break;
        }
        return -EINVAL;
}

static const struct iio_info ad7292_info = {
        .read_raw = ad7292_read_raw,
};

static void ad7292_regulator_disable(void *data)
{
        struct ad7292_state *st = data;

        regulator_disable(st->reg);
}

static int ad7292_probe(struct spi_device *spi)
{
        struct ad7292_state *st;
        struct iio_dev *indio_dev;
        struct device_node *child;
        bool diff_channels = false;
        int ret;

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

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

        ret = ad7292_spi_reg_read(st, AD7292_REG_VENDOR_ID);
        if (ret != ADI_VENDOR_ID) {
                dev_err(&spi->dev, "Wrong vendor id 0x%x\n", ret);
                return -EINVAL;
        }

        st->reg = devm_regulator_get_optional(&spi->dev, "vref");
        if (!IS_ERR(st->reg)) {
                ret = regulator_enable(st->reg);
                if (ret) {
                        dev_err(&spi->dev,
                                "Failed to enable external vref supply\n");
                        return ret;
                }

                ret = devm_add_action_or_reset(&spi->dev,
                                               ad7292_regulator_disable, st);
                if (ret) {
                        regulator_disable(st->reg);
                        return ret;
                }

                ret = regulator_get_voltage(st->reg);
                if (ret < 0)
                        return ret;

                st->vref_mv = ret / 1000;
        } else {
                /* Use the internal voltage reference. */
                st->vref_mv = 1250;
        }

        indio_dev->name = spi_get_device_id(spi)->name;
        indio_dev->modes = INDIO_DIRECT_MODE;
        indio_dev->info = &ad7292_info;

        for_each_available_child_of_node(spi->dev.of_node, child) {
                diff_channels = of_property_read_bool(child, "diff-channels");
                if (diff_channels) {
                        of_node_put(child);
                        break;
                }
        }

        if (diff_channels) {
                indio_dev->num_channels = ARRAY_SIZE(ad7292_channels_diff);
                indio_dev->channels = ad7292_channels_diff;
        } else {
                indio_dev->num_channels = ARRAY_SIZE(ad7292_channels);
                indio_dev->channels = ad7292_channels;
        }

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

static const struct spi_device_id ad7292_id_table[] = {
        { "ad7292", 0 },
        {}
};
MODULE_DEVICE_TABLE(spi, ad7292_id_table);

static const struct of_device_id ad7292_of_match[] = {
        { .compatible = "adi,ad7292" },
        { },
};
MODULE_DEVICE_TABLE(of, ad7292_of_match);

static struct spi_driver ad7292_driver = {
        .driver = {
                .name = "ad7292",
                .of_match_table = ad7292_of_match,
        },
        .probe = ad7292_probe,
        .id_table = ad7292_id_table,
};
module_spi_driver(ad7292_driver);

MODULE_AUTHOR("Marcelo Schmitt <marcelo.schmitt1@gmail.com>");
MODULE_DESCRIPTION("Analog Devices AD7292 ADC driver");
MODULE_LICENSE("GPL v2");