ada4250.c

// SPDX-License-Identifier: GPL-2.0-only
/*
 * ADA4250 driver
 *
 * Copyright 2022 Analog Devices Inc.
 */

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

#include <asm/unaligned.h>

/* ADA4250 Register Map */
#define ADA4250_REG_GAIN_MUX        0x00
#define ADA4250_REG_REFBUF_EN       0x01
#define ADA4250_REG_RESET           0x02
#define ADA4250_REG_SNSR_CAL_VAL    0x04
#define ADA4250_REG_SNSR_CAL_CNFG   0x05
#define ADA4250_REG_DIE_REV         0x18
#define ADA4250_REG_CHIP_ID         0x19

/* ADA4250_REG_GAIN_MUX Map */
#define ADA4250_GAIN_MUX_MSK        GENMASK(2, 0)

/* ADA4250_REG_REFBUF Map */
#define ADA4250_REFBUF_MSK          BIT(0)

/* ADA4250_REG_RESET Map */
#define ADA4250_RESET_MSK           BIT(0)

/* ADA4250_REG_SNSR_CAL_VAL Map */
#define ADA4250_CAL_CFG_BIAS_MSK    GENMASK(7, 0)

/* ADA4250_REG_SNSR_CAL_CNFG Bit Definition */
#define ADA4250_BIAS_SET_MSK        GENMASK(3, 2)
#define ADA4250_RANGE_SET_MSK       GENMASK(1, 0)

/* Miscellaneous definitions */
#define ADA4250_CHIP_ID             0x4250
#define ADA4250_RANGE1              0
#define	ADA4250_RANGE4              3

/* ADA4250 current bias set */
enum ada4250_current_bias {
	ADA4250_BIAS_DISABLED,
	ADA4250_BIAS_BANDGAP,
	ADA4250_BIAS_AVDD,
};

struct ada4250_state {
	struct spi_device	*spi;
	struct regmap		*regmap;
	struct regulator	*reg;
	/* Protect against concurrent accesses to the device and data content */
	struct mutex		lock;
	u8			bias;
	u8			gain;
	int			offset_uv;
	bool			refbuf_en;
};

/* ADA4250 Current Bias Source Settings: Disabled, Bandgap Reference, AVDD */
static const int calibbias_table[] = {0, 1, 2};

/* ADA4250 Gain (V/V) values: 1, 2, 4, 8, 16, 32, 64, 128 */
static const int hwgain_table[] = {1, 2, 4, 8, 16, 32, 64, 128};

static const struct regmap_config ada4250_regmap_config = {
	.reg_bits = 8,
	.val_bits = 8,
	.read_flag_mask = BIT(7),
	.max_register = 0x1A,
};

static int ada4250_set_offset_uv(struct iio_dev *indio_dev,
				 const struct iio_chan_spec *chan,
				 int offset_uv)
{
	struct ada4250_state *st = iio_priv(indio_dev);

	int i, ret, x[8], max_vos, min_vos, voltage_v, vlsb = 0;
	u8 offset_raw, range = ADA4250_RANGE1;
	u32 lsb_coeff[6] = {1333, 2301, 4283, 8289, 16311, 31599};

	if (st->bias == 0 || st->bias == 3)
		return -EINVAL;

	voltage_v = regulator_get_voltage(st->reg);
	voltage_v = DIV_ROUND_CLOSEST(voltage_v, 1000000);

	if (st->bias == ADA4250_BIAS_AVDD)
		x[0] = voltage_v;
	else
		x[0] = 5;

	x[1] = 126 * (x[0] - 1);

	for (i = 0; i < 6; i++)
		x[i + 2] = DIV_ROUND_CLOSEST(x[1] * 1000, lsb_coeff[i]);

	if (st->gain == 0)
		return -EINVAL;

	/*
	 * Compute Range and Voltage per LSB for the Sensor Offset Calibration
	 * Example of computation for Range 1 and Range 2 (Curren Bias Set = AVDD):
	 *                     Range 1                            Range 2
	 *   Gain   | Max Vos(mV) |   LSB(mV)        |  Max Vos(mV)  | LSB(mV) |
	 *    2     |    X1*127   | X1=0.126(AVDD-1) |   X1*3*127    |  X1*3   |
	 *    4     |    X2*127   | X2=X1/1.3333     |   X2*3*127    |  X2*3   |
	 *    8     |    X3*127   | X3=X1/2.301      |   X3*3*127    |  X3*3   |
	 *    16    |    X4*127   | X4=X1/4.283      |   X4*3*127    |  X4*3   |
	 *    32    |    X5*127   | X5=X1/8.289      |   X5*3*127    |  X5*3   |
	 *    64    |    X6*127   | X6=X1/16.311     |   X6*3*127    |  X6*3   |
	 *    128   |    X7*127   | X7=X1/31.599     |   X7*3*127    |  X7*3   |
	 */
	for (i = ADA4250_RANGE1; i <= ADA4250_RANGE4; i++) {
		max_vos = x[st->gain] *  127 * ((1 << (i + 1)) - 1);
		min_vos = -1 * max_vos;
		if (offset_uv > min_vos && offset_uv < max_vos) {
			range = i;
			vlsb = x[st->gain] * ((1 << (i + 1)) - 1);
			break;
		}
	}

	if (vlsb <= 0)
		return -EINVAL;

	offset_raw = DIV_ROUND_CLOSEST(abs(offset_uv), vlsb);

	mutex_lock(&st->lock);
	ret = regmap_update_bits(st->regmap, ADA4250_REG_SNSR_CAL_CNFG,
				 ADA4250_RANGE_SET_MSK,
				 FIELD_PREP(ADA4250_RANGE_SET_MSK, range));
	if (ret)
		goto exit;

	st->offset_uv = offset_raw * vlsb;

	/*
	 * To set the offset calibration value, use bits [6:0] and bit 7 as the
	 * polarity bit (set to "0" for a negative offset and "1" for a positive
	 * offset).
	 */
	if (offset_uv < 0) {
		offset_raw |= BIT(7);
		st->offset_uv *= (-1);
	}

	ret = regmap_write(st->regmap, ADA4250_REG_SNSR_CAL_VAL, offset_raw);

exit:
	mutex_unlock(&st->lock);

	return ret;
}

static int ada4250_read_raw(struct iio_dev *indio_dev,
			    struct iio_chan_spec const *chan,
			    int *val, int *val2, long info)
{
	struct ada4250_state *st = iio_priv(indio_dev);
	int ret;

	switch (info) {
	case IIO_CHAN_INFO_HARDWAREGAIN:
		ret = regmap_read(st->regmap, ADA4250_REG_GAIN_MUX, val);
		if (ret)
			return ret;

		*val = BIT(*val);

		return IIO_VAL_INT;
	case IIO_CHAN_INFO_OFFSET:
		*val = st->offset_uv;

		return IIO_VAL_INT;
	case IIO_CHAN_INFO_CALIBBIAS:
		ret = regmap_read(st->regmap, ADA4250_REG_SNSR_CAL_CNFG, val);
		if (ret)
			return ret;

		*val = FIELD_GET(ADA4250_BIAS_SET_MSK, *val);

		return IIO_VAL_INT;
	case IIO_CHAN_INFO_SCALE:
		*val = 1;
		*val2 = 1000000;

		return IIO_VAL_FRACTIONAL;
	default:
		return -EINVAL;
	}
}

static int ada4250_write_raw(struct iio_dev *indio_dev,
			     struct iio_chan_spec const *chan,
			     int val, int val2, long info)
{
	struct ada4250_state *st = iio_priv(indio_dev);
	int ret;

	switch (info) {
	case IIO_CHAN_INFO_HARDWAREGAIN:
		ret = regmap_write(st->regmap, ADA4250_REG_GAIN_MUX,
				   FIELD_PREP(ADA4250_GAIN_MUX_MSK, ilog2(val)));
		if (ret)
			return ret;

		st->gain = ilog2(val);

		return ret;
	case IIO_CHAN_INFO_OFFSET:
		return ada4250_set_offset_uv(indio_dev, chan, val);
	case IIO_CHAN_INFO_CALIBBIAS:
		ret = regmap_update_bits(st->regmap, ADA4250_REG_SNSR_CAL_CNFG,
					 ADA4250_BIAS_SET_MSK,
					 FIELD_PREP(ADA4250_BIAS_SET_MSK, val));
		if (ret)
			return ret;

		st->bias = val;

		return ret;
	default:
		return -EINVAL;
	}
}

static int ada4250_read_avail(struct iio_dev *indio_dev,
			      struct iio_chan_spec const *chan,
			      const int **vals, int *type, int *length,
			      long mask)
{
	switch (mask) {
	case IIO_CHAN_INFO_CALIBBIAS:
		*vals = calibbias_table;
		*type = IIO_VAL_INT;
		*length = ARRAY_SIZE(calibbias_table);

		return IIO_AVAIL_LIST;
	case IIO_CHAN_INFO_HARDWAREGAIN:
		*vals = hwgain_table;
		*type = IIO_VAL_INT;
		*length = ARRAY_SIZE(hwgain_table);

		return IIO_AVAIL_LIST;
	default:
		return -EINVAL;
	}
}

static int ada4250_reg_access(struct iio_dev *indio_dev,
			      unsigned int reg,
			      unsigned int write_val,
			      unsigned int *read_val)
{
	struct ada4250_state *st = iio_priv(indio_dev);

	if (read_val)
		return regmap_read(st->regmap, reg, read_val);
	else
		return regmap_write(st->regmap, reg, write_val);
}

static const struct iio_info ada4250_info = {
	.read_raw = ada4250_read_raw,
	.write_raw = ada4250_write_raw,
	.read_avail = &ada4250_read_avail,
	.debugfs_reg_access = &ada4250_reg_access,
};

static const struct iio_chan_spec ada4250_channels[] = {
	{
		.type = IIO_VOLTAGE,
		.output = 1,
		.indexed = 1,
		.channel = 0,
		.info_mask_separate = BIT(IIO_CHAN_INFO_HARDWAREGAIN) |
				BIT(IIO_CHAN_INFO_OFFSET) |
				BIT(IIO_CHAN_INFO_CALIBBIAS) |
				BIT(IIO_CHAN_INFO_SCALE),
		.info_mask_separate_available = BIT(IIO_CHAN_INFO_CALIBBIAS) |
						BIT(IIO_CHAN_INFO_HARDWAREGAIN),
	}
};

static void ada4250_reg_disable(void *data)
{
	regulator_disable(data);
}

static int ada4250_init(struct ada4250_state *st)
{
	int ret;
	u16 chip_id;
	u8 data[2] __aligned(8) = {};
	struct spi_device *spi = st->spi;

	st->refbuf_en = device_property_read_bool(&spi->dev, "adi,refbuf-enable");

	st->reg = devm_regulator_get(&spi->dev, "avdd");
	if (IS_ERR(st->reg))
		return dev_err_probe(&spi->dev, PTR_ERR(st->reg),
				     "failed to get the AVDD voltage\n");

	ret = regulator_enable(st->reg);
	if (ret) {
		dev_err(&spi->dev, "Failed to enable specified AVDD supply\n");
		return ret;
	}

	ret = devm_add_action_or_reset(&spi->dev, ada4250_reg_disable, st->reg);
	if (ret)
		return ret;

	ret = regmap_write(st->regmap, ADA4250_REG_RESET,
			   FIELD_PREP(ADA4250_RESET_MSK, 1));
	if (ret)
		return ret;

	ret = regmap_bulk_read(st->regmap, ADA4250_REG_CHIP_ID, data, 2);
	if (ret)
		return ret;

	chip_id = get_unaligned_le16(data);

	if (chip_id != ADA4250_CHIP_ID) {
		dev_err(&spi->dev, "Invalid chip ID.\n");
		return -EINVAL;
	}

	return regmap_write(st->regmap, ADA4250_REG_REFBUF_EN,
			    FIELD_PREP(ADA4250_REFBUF_MSK, st->refbuf_en));
}

static int ada4250_probe(struct spi_device *spi)
{
	struct iio_dev *indio_dev;
	struct regmap *regmap;
	struct ada4250_state *st;
	int ret;

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

	regmap = devm_regmap_init_spi(spi, &ada4250_regmap_config);
	if (IS_ERR(regmap))
		return PTR_ERR(regmap);

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

	indio_dev->info = &ada4250_info;
	indio_dev->name = "ada4250";
	indio_dev->channels = ada4250_channels;
	indio_dev->num_channels = ARRAY_SIZE(ada4250_channels);

	mutex_init(&st->lock);

	ret = ada4250_init(st);
	if (ret) {
		dev_err(&spi->dev, "ADA4250 init failed\n");
		return ret;
	}

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

static const struct spi_device_id ada4250_id[] = {
	{ "ada4250", 0 },
	{}
};
MODULE_DEVICE_TABLE(spi, ada4250_id);

static const struct of_device_id ada4250_of_match[] = {
	{ .compatible = "adi,ada4250" },
	{},
};
MODULE_DEVICE_TABLE(of, ada4250_of_match);

static struct spi_driver ada4250_driver = {
	.driver = {
			.name = "ada4250",
			.of_match_table = ada4250_of_match,
		},
	.probe = ada4250_probe,
	.id_table = ada4250_id,
};
module_spi_driver(ada4250_driver);

MODULE_AUTHOR("Antoniu Miclaus <antoniu.miclaus@analog.com");
MODULE_DESCRIPTION("Analog Devices ADA4250");
MODULE_LICENSE("GPL v2");