drivers/iio/adc/ad7949.c - linux - Git at Google

 // SPDX-License-Identifier: GPL-2.0
 /* ad7949.c - Analog Devices ADC driver 14/16 bits 4/8 channels
  *
  * Copyright (C) 2018 CMC NV
  *
  * https://www.analog.com/media/en/technical-documentation/data-sheets/AD7949.pdf
  */

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

 #define AD7949_CFG_MASK_TOTAL		GENMASK(13, 0)

 /* CFG: Configuration Update */
 #define AD7949_CFG_MASK_OVERWRITE	BIT(13)

 /* INCC: Input Channel Configuration */
 #define AD7949_CFG_MASK_INCC		GENMASK(12, 10)
 #define AD7949_CFG_VAL_INCC_UNIPOLAR_GND	7
 #define AD7949_CFG_VAL_INCC_UNIPOLAR_COMM	6
 #define AD7949_CFG_VAL_INCC_UNIPOLAR_DIFF	4
 #define AD7949_CFG_VAL_INCC_TEMP		3
 #define AD7949_CFG_VAL_INCC_BIPOLAR		2
 #define AD7949_CFG_VAL_INCC_BIPOLAR_DIFF	0

 /* INX: Input channel Selection in a binary fashion */
 #define AD7949_CFG_MASK_INX		GENMASK(9, 7)

 /* BW: select bandwidth for low-pass filter. Full or Quarter */
 #define AD7949_CFG_MASK_BW_FULL		BIT(6)

 /* REF: reference/buffer selection */
 #define AD7949_CFG_MASK_REF		GENMASK(5, 3)
 #define AD7949_CFG_VAL_REF_EXT_TEMP_BUF		3
 #define AD7949_CFG_VAL_REF_EXT_TEMP		2
 #define AD7949_CFG_VAL_REF_INT_4096		1
 #define AD7949_CFG_VAL_REF_INT_2500		0
 #define AD7949_CFG_VAL_REF_EXTERNAL		BIT(1)

 /* SEQ: channel sequencer. Allows for scanning channels */
 #define AD7949_CFG_MASK_SEQ		GENMASK(2, 1)

 /* RB: Read back the CFG register */
 #define AD7949_CFG_MASK_RBN		BIT(0)

 enum {
 	ID_AD7949 = 0,
 	ID_AD7682,
 	ID_AD7689,
 };

 struct ad7949_adc_spec {
 	u8 num_channels;
 	u8 resolution;
 };

 static const struct ad7949_adc_spec ad7949_adc_spec[] = {
 	[ID_AD7949] = { .num_channels = 8, .resolution = 14 },
 	[ID_AD7682] = { .num_channels = 4, .resolution = 16 },
 	[ID_AD7689] = { .num_channels = 8, .resolution = 16 },
 };

 /**
  * struct ad7949_adc_chip - AD ADC chip
  * @lock: protects write sequences
  * @vref: regulator generating Vref
  * @indio_dev: reference to iio structure
  * @spi: reference to spi structure
  * @refsel: reference selection
  * @resolution: resolution of the chip
  * @cfg: copy of the configuration register
  * @current_channel: current channel in use
  * @buffer: buffer to send / receive data to / from device
  * @buf8b: be16 buffer to exchange data with the device in 8-bit transfers
  */
 struct ad7949_adc_chip {
 	struct mutex lock;
 	struct regulator *vref;
 	struct iio_dev *indio_dev;
 	struct spi_device *spi;
 	u32 refsel;
 	u8 resolution;
 	u16 cfg;
 	unsigned int current_channel;
 	u16 buffer __aligned(IIO_DMA_MINALIGN);
 	__be16 buf8b;
 };

 static int ad7949_spi_write_cfg(struct ad7949_adc_chip *ad7949_adc, u16 val,
 				u16 mask)
 {
 	int ret;

 	ad7949_adc->cfg = (val & mask) | (ad7949_adc->cfg & ~mask);

 	switch (ad7949_adc->spi->bits_per_word) {
 	case 16:
 		ad7949_adc->buffer = ad7949_adc->cfg << 2;
 		ret = spi_write(ad7949_adc->spi, &ad7949_adc->buffer, 2);
 		break;
 	case 14:
 		ad7949_adc->buffer = ad7949_adc->cfg;
 		ret = spi_write(ad7949_adc->spi, &ad7949_adc->buffer, 2);
 		break;
 	case 8:
 		/* Here, type is big endian as it must be sent in two transfers */
 		ad7949_adc->buf8b = cpu_to_be16(ad7949_adc->cfg << 2);
 		ret = spi_write(ad7949_adc->spi, &ad7949_adc->buf8b, 2);
 		break;
 	default:
 		dev_err(&ad7949_adc->indio_dev->dev, "unsupported BPW\n");
 		return -EINVAL;
 	}

 	/*
 	 * This delay is to avoid a new request before the required time to
 	 * send a new command to the device
 	 */
 	udelay(2);
 	return ret;
 }

 static int ad7949_spi_read_channel(struct ad7949_adc_chip *ad7949_adc, int *val,
 				   unsigned int channel)
 {
 	int ret;
 	int i;

 	/*
 	 * 1: write CFG for sample N and read old data (sample N-2)
 	 * 2: if CFG was not changed since sample N-1 then we'll get good data
 	 *    at the next xfer, so we bail out now, otherwise we write something
 	 *    and we read garbage (sample N-1 configuration).
 	 */
 	for (i = 0; i < 2; i++) {
 		ret = ad7949_spi_write_cfg(ad7949_adc,
 					   FIELD_PREP(AD7949_CFG_MASK_INX, channel),
 					   AD7949_CFG_MASK_INX);
 		if (ret)
 			return ret;
 		if (channel == ad7949_adc->current_channel)
 			break;
 	}

 	/* 3: write something and read actual data */
 	if (ad7949_adc->spi->bits_per_word == 8)
 		ret = spi_read(ad7949_adc->spi, &ad7949_adc->buf8b, 2);
 	else
 		ret = spi_read(ad7949_adc->spi, &ad7949_adc->buffer, 2);

 	if (ret)
 		return ret;

 	/*
 	 * This delay is to avoid a new request before the required time to
 	 * send a new command to the device
 	 */
 	udelay(2);

 	ad7949_adc->current_channel = channel;

 	switch (ad7949_adc->spi->bits_per_word) {
 	case 16:
 		*val = ad7949_adc->buffer;
 		/* Shift-out padding bits */
 		*val >>= 16 - ad7949_adc->resolution;
 		break;
 	case 14:
 		*val = ad7949_adc->buffer & GENMASK(13, 0);
 		break;
 	case 8:
 		/* Here, type is big endian as data was sent in two transfers */
 		*val = be16_to_cpu(ad7949_adc->buf8b);
 		/* Shift-out padding bits */
 		*val >>= 16 - ad7949_adc->resolution;
 		break;
 	default:
 		dev_err(&ad7949_adc->indio_dev->dev, "unsupported BPW\n");
 		return -EINVAL;
 	}

 	return 0;
 }

 #define AD7949_ADC_CHANNEL(chan) {				\
 	.type = IIO_VOLTAGE,					\
 	.indexed = 1,						\
 	.channel = (chan),					\
 	.info_mask_separate = BIT(IIO_CHAN_INFO_RAW),		\
 	.info_mask_shared_by_type = BIT(IIO_CHAN_INFO_SCALE),	\
 }

 static const struct iio_chan_spec ad7949_adc_channels[] = {
 	AD7949_ADC_CHANNEL(0),
 	AD7949_ADC_CHANNEL(1),
 	AD7949_ADC_CHANNEL(2),
 	AD7949_ADC_CHANNEL(3),
 	AD7949_ADC_CHANNEL(4),
 	AD7949_ADC_CHANNEL(5),
 	AD7949_ADC_CHANNEL(6),
 	AD7949_ADC_CHANNEL(7),
 };

 static int ad7949_spi_read_raw(struct iio_dev *indio_dev,
 			   struct iio_chan_spec const *chan,
 			   int *val, int *val2, long mask)
 {
 	struct ad7949_adc_chip *ad7949_adc = iio_priv(indio_dev);
 	int ret;

 	if (!val)
 		return -EINVAL;

 	switch (mask) {
 	case IIO_CHAN_INFO_RAW:
 		mutex_lock(&ad7949_adc->lock);
 		ret = ad7949_spi_read_channel(ad7949_adc, val, chan->channel);
 		mutex_unlock(&ad7949_adc->lock);

 		if (ret < 0)
 			return ret;

 		return IIO_VAL_INT;

 	case IIO_CHAN_INFO_SCALE:
 		switch (ad7949_adc->refsel) {
 		case AD7949_CFG_VAL_REF_INT_2500:
 			*val = 2500;
 			break;
 		case AD7949_CFG_VAL_REF_INT_4096:
 			*val = 4096;
 			break;
 		case AD7949_CFG_VAL_REF_EXT_TEMP:
 		case AD7949_CFG_VAL_REF_EXT_TEMP_BUF:
 			ret = regulator_get_voltage(ad7949_adc->vref);
 			if (ret < 0)
 				return ret;

 			/* convert value back to mV */
 			*val = ret / 1000;
 			break;
 		}

 		*val2 = (1 << ad7949_adc->resolution) - 1;
 		return IIO_VAL_FRACTIONAL;
 	}

 	return -EINVAL;
 }

 static int ad7949_spi_reg_access(struct iio_dev *indio_dev,
 			unsigned int reg, unsigned int writeval,
 			unsigned int *readval)
 {
 	struct ad7949_adc_chip *ad7949_adc = iio_priv(indio_dev);
 	int ret = 0;

 	if (readval)
 		*readval = ad7949_adc->cfg;
 	else
 		ret = ad7949_spi_write_cfg(ad7949_adc, writeval,
 					   AD7949_CFG_MASK_TOTAL);

 	return ret;
 }

 static const struct iio_info ad7949_spi_info = {
 	.read_raw = ad7949_spi_read_raw,
 	.debugfs_reg_access = ad7949_spi_reg_access,
 };

 static int ad7949_spi_init(struct ad7949_adc_chip *ad7949_adc)
 {
 	int ret;
 	int val;
 	u16 cfg;

 	ad7949_adc->current_channel = 0;

 	cfg = FIELD_PREP(AD7949_CFG_MASK_OVERWRITE, 1) |
 		FIELD_PREP(AD7949_CFG_MASK_INCC, AD7949_CFG_VAL_INCC_UNIPOLAR_GND) |
 		FIELD_PREP(AD7949_CFG_MASK_INX, ad7949_adc->current_channel) |
 		FIELD_PREP(AD7949_CFG_MASK_BW_FULL, 1) |
 		FIELD_PREP(AD7949_CFG_MASK_REF, ad7949_adc->refsel) |
 		FIELD_PREP(AD7949_CFG_MASK_SEQ, 0x0) |
 		FIELD_PREP(AD7949_CFG_MASK_RBN, 1);

 	ret = ad7949_spi_write_cfg(ad7949_adc, cfg, AD7949_CFG_MASK_TOTAL);

 	/*
 	 * Do two dummy conversions to apply the first configuration setting.
 	 * Required only after the start up of the device.
 	 */
 	ad7949_spi_read_channel(ad7949_adc, &val, ad7949_adc->current_channel);
 	ad7949_spi_read_channel(ad7949_adc, &val, ad7949_adc->current_channel);

 	return ret;
 }

 static void ad7949_disable_reg(void *reg)
 {
 	regulator_disable(reg);
 }

 static int ad7949_spi_probe(struct spi_device *spi)
 {
 	u32 spi_ctrl_mask = spi->controller->bits_per_word_mask;
 	struct device *dev = &spi->dev;
 	const struct ad7949_adc_spec *spec;
 	struct ad7949_adc_chip *ad7949_adc;
 	struct iio_dev *indio_dev;
 	u32 tmp;
 	int ret;

 	indio_dev = devm_iio_device_alloc(dev, sizeof(*ad7949_adc));
 	if (!indio_dev) {
 		dev_err(dev, "can not allocate iio device\n");
 		return -ENOMEM;
 	}

 	indio_dev->info = &ad7949_spi_info;
 	indio_dev->name = spi_get_device_id(spi)->name;
 	indio_dev->modes = INDIO_DIRECT_MODE;
 	indio_dev->channels = ad7949_adc_channels;
 	spi_set_drvdata(spi, indio_dev);

 	ad7949_adc = iio_priv(indio_dev);
 	ad7949_adc->indio_dev = indio_dev;
 	ad7949_adc->spi = spi;

 	spec = &ad7949_adc_spec[spi_get_device_id(spi)->driver_data];
 	indio_dev->num_channels = spec->num_channels;
 	ad7949_adc->resolution = spec->resolution;

 	/* Set SPI bits per word */
 	if (spi_ctrl_mask & SPI_BPW_MASK(ad7949_adc->resolution)) {
 		spi->bits_per_word = ad7949_adc->resolution;
 	} else if (spi_ctrl_mask == SPI_BPW_MASK(16)) {
 		spi->bits_per_word = 16;
 	} else if (spi_ctrl_mask == SPI_BPW_MASK(8)) {
 		spi->bits_per_word = 8;
 	} else {
 		dev_err(dev, "unable to find common BPW with spi controller\n");
 		return -EINVAL;
 	}

 	/* Setup internal voltage reference */
 	tmp = 4096000;
 	device_property_read_u32(dev, "adi,internal-ref-microvolt", &tmp);

 	switch (tmp) {
 	case 2500000:
 		ad7949_adc->refsel = AD7949_CFG_VAL_REF_INT_2500;
 		break;
 	case 4096000:
 		ad7949_adc->refsel = AD7949_CFG_VAL_REF_INT_4096;
 		break;
 	default:
 		dev_err(dev, "unsupported internal voltage reference\n");
 		return -EINVAL;
 	}

 	/* Setup external voltage reference, buffered? */
 	ad7949_adc->vref = devm_regulator_get_optional(dev, "vrefin");
 	if (IS_ERR(ad7949_adc->vref)) {
 		ret = PTR_ERR(ad7949_adc->vref);
 		if (ret != -ENODEV)
 			return ret;
 		/* unbuffered? */
 		ad7949_adc->vref = devm_regulator_get_optional(dev, "vref");
 		if (IS_ERR(ad7949_adc->vref)) {
 			ret = PTR_ERR(ad7949_adc->vref);
 			if (ret != -ENODEV)
 				return ret;
 		} else {
 			ad7949_adc->refsel = AD7949_CFG_VAL_REF_EXT_TEMP;
 		}
 	} else {
 		ad7949_adc->refsel = AD7949_CFG_VAL_REF_EXT_TEMP_BUF;
 	}

 	if (ad7949_adc->refsel & AD7949_CFG_VAL_REF_EXTERNAL) {
 		ret = regulator_enable(ad7949_adc->vref);
 		if (ret < 0) {
 			dev_err(dev, "fail to enable regulator\n");
 			return ret;
 		}

 		ret = devm_add_action_or_reset(dev, ad7949_disable_reg,
 					       ad7949_adc->vref);
 		if (ret)
 			return ret;
 	}

 	mutex_init(&ad7949_adc->lock);

 	ret = ad7949_spi_init(ad7949_adc);
 	if (ret) {
 		dev_err(dev, "fail to init this device: %d\n", ret);
 		return ret;
 	}

 	ret = devm_iio_device_register(dev, indio_dev);
 	if (ret)
 		dev_err(dev, "fail to register iio device: %d\n", ret);

 	return ret;
 }

 static const struct of_device_id ad7949_spi_of_id[] = {
 	{ .compatible = "adi,ad7949" },
 	{ .compatible = "adi,ad7682" },
 	{ .compatible = "adi,ad7689" },
 	{ }
 };
 MODULE_DEVICE_TABLE(of, ad7949_spi_of_id);

 static const struct spi_device_id ad7949_spi_id[] = {
 	{ "ad7949", ID_AD7949  },
 	{ "ad7682", ID_AD7682 },
 	{ "ad7689", ID_AD7689 },
 	{ }
 };
 MODULE_DEVICE_TABLE(spi, ad7949_spi_id);

 static struct spi_driver ad7949_spi_driver = {
 	.driver = {
 		.name		= "ad7949",
 		.of_match_table	= ad7949_spi_of_id,
 	},
 	.probe	  = ad7949_spi_probe,
 	.id_table = ad7949_spi_id,
 };
 module_spi_driver(ad7949_spi_driver);

 MODULE_AUTHOR("Charles-Antoine Couret <charles-antoine.couret@essensium.com>");
 MODULE_DESCRIPTION("Analog Devices 14/16-bit 8-channel ADC driver");
 MODULE_LICENSE("GPL v2");
	// SPDX-License-Identifier: GPL-2.0
	/* ad7949.c - Analog Devices ADC driver 14/16 bits 4/8 channels
	*
	* Copyright (C) 2018 CMC NV
	*
	* https://www.analog.com/media/en/technical-documentation/data-sheets/AD7949.pdf
	*/

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

	#define AD7949_CFG_MASK_TOTAL GENMASK(13, 0)

	/* CFG: Configuration Update */
	#define AD7949_CFG_MASK_OVERWRITE BIT(13)

	/* INCC: Input Channel Configuration */
	#define AD7949_CFG_MASK_INCC GENMASK(12, 10)
	#define AD7949_CFG_VAL_INCC_UNIPOLAR_GND 7
	#define AD7949_CFG_VAL_INCC_UNIPOLAR_COMM 6
	#define AD7949_CFG_VAL_INCC_UNIPOLAR_DIFF 4
	#define AD7949_CFG_VAL_INCC_TEMP 3
	#define AD7949_CFG_VAL_INCC_BIPOLAR 2
	#define AD7949_CFG_VAL_INCC_BIPOLAR_DIFF 0

	/* INX: Input channel Selection in a binary fashion */
	#define AD7949_CFG_MASK_INX GENMASK(9, 7)

	/* BW: select bandwidth for low-pass filter. Full or Quarter */
	#define AD7949_CFG_MASK_BW_FULL BIT(6)

	/* REF: reference/buffer selection */
	#define AD7949_CFG_MASK_REF GENMASK(5, 3)
	#define AD7949_CFG_VAL_REF_EXT_TEMP_BUF 3
	#define AD7949_CFG_VAL_REF_EXT_TEMP 2
	#define AD7949_CFG_VAL_REF_INT_4096 1
	#define AD7949_CFG_VAL_REF_INT_2500 0
	#define AD7949_CFG_VAL_REF_EXTERNAL BIT(1)

	/* SEQ: channel sequencer. Allows for scanning channels */
	#define AD7949_CFG_MASK_SEQ GENMASK(2, 1)

	/* RB: Read back the CFG register */
	#define AD7949_CFG_MASK_RBN BIT(0)

	enum {
	ID_AD7949 = 0,
	ID_AD7682,
	ID_AD7689,
	};

	struct ad7949_adc_spec {
	u8 num_channels;
	u8 resolution;
	};

	static const struct ad7949_adc_spec ad7949_adc_spec[] = {
	[ID_AD7949] = { .num_channels = 8, .resolution = 14 },
	[ID_AD7682] = { .num_channels = 4, .resolution = 16 },
	[ID_AD7689] = { .num_channels = 8, .resolution = 16 },
	};

	/**
	* struct ad7949_adc_chip - AD ADC chip
	* @lock: protects write sequences
	* @vref: regulator generating Vref
	* @indio_dev: reference to iio structure
	* @spi: reference to spi structure
	* @refsel: reference selection
	* @resolution: resolution of the chip
	* @cfg: copy of the configuration register
	* @current_channel: current channel in use
	* @buffer: buffer to send / receive data to / from device
	* @buf8b: be16 buffer to exchange data with the device in 8-bit transfers
	*/
	struct ad7949_adc_chip {
	struct mutex lock;
	struct regulator *vref;
	struct iio_dev *indio_dev;
	struct spi_device *spi;
	u32 refsel;
	u8 resolution;
	u16 cfg;
	unsigned int current_channel;
	u16 buffer __aligned(IIO_DMA_MINALIGN);
	__be16 buf8b;
	};

	static int ad7949_spi_write_cfg(struct ad7949_adc_chip *ad7949_adc, u16 val,
	u16 mask)
	{
	int ret;

	ad7949_adc->cfg = (val & mask) \| (ad7949_adc->cfg & ~mask);

	switch (ad7949_adc->spi->bits_per_word) {
	case 16:
	ad7949_adc->buffer = ad7949_adc->cfg << 2;
	ret = spi_write(ad7949_adc->spi, &ad7949_adc->buffer, 2);
	break;
	case 14:
	ad7949_adc->buffer = ad7949_adc->cfg;
	ret = spi_write(ad7949_adc->spi, &ad7949_adc->buffer, 2);
	break;
	case 8:
	/* Here, type is big endian as it must be sent in two transfers */
	ad7949_adc->buf8b = cpu_to_be16(ad7949_adc->cfg << 2);
	ret = spi_write(ad7949_adc->spi, &ad7949_adc->buf8b, 2);
	break;
	default:
	dev_err(&ad7949_adc->indio_dev->dev, "unsupported BPW\n");
	return -EINVAL;
	}

	/*
	* This delay is to avoid a new request before the required time to
	* send a new command to the device
	*/
	udelay(2);
	return ret;
	}

	static int ad7949_spi_read_channel(struct ad7949_adc_chip ad7949_adc, int val,
	unsigned int channel)
	{
	int ret;
	int i;

	/*
	* 1: write CFG for sample N and read old data (sample N-2)
	* 2: if CFG was not changed since sample N-1 then we'll get good data
	* at the next xfer, so we bail out now, otherwise we write something
	* and we read garbage (sample N-1 configuration).
	*/
	for (i = 0; i < 2; i++) {
	ret = ad7949_spi_write_cfg(ad7949_adc,
	FIELD_PREP(AD7949_CFG_MASK_INX, channel),
	AD7949_CFG_MASK_INX);
	if (ret)
	return ret;
	if (channel == ad7949_adc->current_channel)
	break;
	}

	/* 3: write something and read actual data */
	if (ad7949_adc->spi->bits_per_word == 8)
	ret = spi_read(ad7949_adc->spi, &ad7949_adc->buf8b, 2);
	else
	ret = spi_read(ad7949_adc->spi, &ad7949_adc->buffer, 2);

	if (ret)
	return ret;

	/*
	* This delay is to avoid a new request before the required time to
	* send a new command to the device
	*/
	udelay(2);

	ad7949_adc->current_channel = channel;

	switch (ad7949_adc->spi->bits_per_word) {
	case 16:
	*val = ad7949_adc->buffer;
	/* Shift-out padding bits */
	*val >>= 16 - ad7949_adc->resolution;
	break;
	case 14:
	*val = ad7949_adc->buffer & GENMASK(13, 0);
	break;
	case 8:
	/* Here, type is big endian as data was sent in two transfers */
	*val = be16_to_cpu(ad7949_adc->buf8b);
	/* Shift-out padding bits */
	*val >>= 16 - ad7949_adc->resolution;
	break;
	default:
	dev_err(&ad7949_adc->indio_dev->dev, "unsupported BPW\n");
	return -EINVAL;
	}

	return 0;
	}

	#define AD7949_ADC_CHANNEL(chan) { \
	.type = IIO_VOLTAGE, \
	.indexed = 1, \
	.channel = (chan), \
	.info_mask_separate = BIT(IIO_CHAN_INFO_RAW), \
	.info_mask_shared_by_type = BIT(IIO_CHAN_INFO_SCALE), \
	}

	static const struct iio_chan_spec ad7949_adc_channels[] = {
	AD7949_ADC_CHANNEL(0),
	AD7949_ADC_CHANNEL(1),
	AD7949_ADC_CHANNEL(2),
	AD7949_ADC_CHANNEL(3),
	AD7949_ADC_CHANNEL(4),
	AD7949_ADC_CHANNEL(5),
	AD7949_ADC_CHANNEL(6),
	AD7949_ADC_CHANNEL(7),
	};

	static int ad7949_spi_read_raw(struct iio_dev *indio_dev,
	struct iio_chan_spec const *chan,
	int val, int val2, long mask)
	{
	struct ad7949_adc_chip *ad7949_adc = iio_priv(indio_dev);
	int ret;

	if (!val)
	return -EINVAL;

	switch (mask) {
	case IIO_CHAN_INFO_RAW:
	mutex_lock(&ad7949_adc->lock);
	ret = ad7949_spi_read_channel(ad7949_adc, val, chan->channel);
	mutex_unlock(&ad7949_adc->lock);

	if (ret < 0)
	return ret;

	return IIO_VAL_INT;

	case IIO_CHAN_INFO_SCALE:
	switch (ad7949_adc->refsel) {
	case AD7949_CFG_VAL_REF_INT_2500:
	*val = 2500;
	break;
	case AD7949_CFG_VAL_REF_INT_4096:
	*val = 4096;
	break;
	case AD7949_CFG_VAL_REF_EXT_TEMP:
	case AD7949_CFG_VAL_REF_EXT_TEMP_BUF:
	ret = regulator_get_voltage(ad7949_adc->vref);
	if (ret < 0)
	return ret;

	/* convert value back to mV */
	*val = ret / 1000;
	break;
	}

	*val2 = (1 << ad7949_adc->resolution) - 1;
	return IIO_VAL_FRACTIONAL;
	}

	return -EINVAL;
	}

	static int ad7949_spi_reg_access(struct iio_dev *indio_dev,
	unsigned int reg, unsigned int writeval,
	unsigned int *readval)
	{
	struct ad7949_adc_chip *ad7949_adc = iio_priv(indio_dev);
	int ret = 0;

	if (readval)
	*readval = ad7949_adc->cfg;
	else
	ret = ad7949_spi_write_cfg(ad7949_adc, writeval,
	AD7949_CFG_MASK_TOTAL);

	return ret;
	}

	static const struct iio_info ad7949_spi_info = {
	.read_raw = ad7949_spi_read_raw,
	.debugfs_reg_access = ad7949_spi_reg_access,
	};

	static int ad7949_spi_init(struct ad7949_adc_chip *ad7949_adc)
	{
	int ret;
	int val;
	u16 cfg;

	ad7949_adc->current_channel = 0;

	cfg = FIELD_PREP(AD7949_CFG_MASK_OVERWRITE, 1) \|
	FIELD_PREP(AD7949_CFG_MASK_INCC, AD7949_CFG_VAL_INCC_UNIPOLAR_GND) \|
	FIELD_PREP(AD7949_CFG_MASK_INX, ad7949_adc->current_channel) \|
	FIELD_PREP(AD7949_CFG_MASK_BW_FULL, 1) \|
	FIELD_PREP(AD7949_CFG_MASK_REF, ad7949_adc->refsel) \|
	FIELD_PREP(AD7949_CFG_MASK_SEQ, 0x0) \|
	FIELD_PREP(AD7949_CFG_MASK_RBN, 1);

	ret = ad7949_spi_write_cfg(ad7949_adc, cfg, AD7949_CFG_MASK_TOTAL);

	/*
	* Do two dummy conversions to apply the first configuration setting.
	* Required only after the start up of the device.
	*/
	ad7949_spi_read_channel(ad7949_adc, &val, ad7949_adc->current_channel);
	ad7949_spi_read_channel(ad7949_adc, &val, ad7949_adc->current_channel);

	return ret;
	}

	static void ad7949_disable_reg(void *reg)
	{
	regulator_disable(reg);
	}

	static int ad7949_spi_probe(struct spi_device *spi)
	{
	u32 spi_ctrl_mask = spi->controller->bits_per_word_mask;
	struct device *dev = &spi->dev;
	const struct ad7949_adc_spec *spec;
	struct ad7949_adc_chip *ad7949_adc;
	struct iio_dev *indio_dev;
	u32 tmp;
	int ret;

	indio_dev = devm_iio_device_alloc(dev, sizeof(*ad7949_adc));
	if (!indio_dev) {
	dev_err(dev, "can not allocate iio device\n");
	return -ENOMEM;
	}

	indio_dev->info = &ad7949_spi_info;
	indio_dev->name = spi_get_device_id(spi)->name;
	indio_dev->modes = INDIO_DIRECT_MODE;
	indio_dev->channels = ad7949_adc_channels;
	spi_set_drvdata(spi, indio_dev);

	ad7949_adc = iio_priv(indio_dev);
	ad7949_adc->indio_dev = indio_dev;
	ad7949_adc->spi = spi;

	spec = &ad7949_adc_spec[spi_get_device_id(spi)->driver_data];
	indio_dev->num_channels = spec->num_channels;
	ad7949_adc->resolution = spec->resolution;

	/* Set SPI bits per word */
	if (spi_ctrl_mask & SPI_BPW_MASK(ad7949_adc->resolution)) {
	spi->bits_per_word = ad7949_adc->resolution;
	} else if (spi_ctrl_mask == SPI_BPW_MASK(16)) {
	spi->bits_per_word = 16;
	} else if (spi_ctrl_mask == SPI_BPW_MASK(8)) {
	spi->bits_per_word = 8;
	} else {
	dev_err(dev, "unable to find common BPW with spi controller\n");
	return -EINVAL;
	}

	/* Setup internal voltage reference */
	tmp = 4096000;
	device_property_read_u32(dev, "adi,internal-ref-microvolt", &tmp);

	switch (tmp) {
	case 2500000:
	ad7949_adc->refsel = AD7949_CFG_VAL_REF_INT_2500;
	break;
	case 4096000:
	ad7949_adc->refsel = AD7949_CFG_VAL_REF_INT_4096;
	break;
	default:
	dev_err(dev, "unsupported internal voltage reference\n");
	return -EINVAL;
	}

	/* Setup external voltage reference, buffered? */
	ad7949_adc->vref = devm_regulator_get_optional(dev, "vrefin");
	if (IS_ERR(ad7949_adc->vref)) {
	ret = PTR_ERR(ad7949_adc->vref);
	if (ret != -ENODEV)
	return ret;
	/* unbuffered? */
	ad7949_adc->vref = devm_regulator_get_optional(dev, "vref");
	if (IS_ERR(ad7949_adc->vref)) {
	ret = PTR_ERR(ad7949_adc->vref);
	if (ret != -ENODEV)
	return ret;
	} else {
	ad7949_adc->refsel = AD7949_CFG_VAL_REF_EXT_TEMP;
	}
	} else {
	ad7949_adc->refsel = AD7949_CFG_VAL_REF_EXT_TEMP_BUF;
	}

	if (ad7949_adc->refsel & AD7949_CFG_VAL_REF_EXTERNAL) {
	ret = regulator_enable(ad7949_adc->vref);
	if (ret < 0) {
	dev_err(dev, "fail to enable regulator\n");
	return ret;
	}

	ret = devm_add_action_or_reset(dev, ad7949_disable_reg,
	ad7949_adc->vref);
	if (ret)
	return ret;
	}

	mutex_init(&ad7949_adc->lock);

	ret = ad7949_spi_init(ad7949_adc);
	if (ret) {
	dev_err(dev, "fail to init this device: %d\n", ret);
	return ret;
	}

	ret = devm_iio_device_register(dev, indio_dev);
	if (ret)
	dev_err(dev, "fail to register iio device: %d\n", ret);

	return ret;
	}

	static const struct of_device_id ad7949_spi_of_id[] = {
	{ .compatible = "adi,ad7949" },
	{ .compatible = "adi,ad7682" },
	{ .compatible = "adi,ad7689" },
	{ }
	};
	MODULE_DEVICE_TABLE(of, ad7949_spi_of_id);

	static const struct spi_device_id ad7949_spi_id[] = {
	{ "ad7949", ID_AD7949 },
	{ "ad7682", ID_AD7682 },
	{ "ad7689", ID_AD7689 },
	{ }
	};
	MODULE_DEVICE_TABLE(spi, ad7949_spi_id);

	static struct spi_driver ad7949_spi_driver = {
	.driver = {
	.name = "ad7949",
	.of_match_table = ad7949_spi_of_id,
	},
	.probe = ad7949_spi_probe,
	.id_table = ad7949_spi_id,
	};
	module_spi_driver(ad7949_spi_driver);

	MODULE_AUTHOR("Charles-Antoine Couret <charles-antoine.couret@essensium.com>");
	MODULE_DESCRIPTION("Analog Devices 14/16-bit 8-channel ADC driver");
	MODULE_LICENSE("GPL v2");