iio: adc: add driver for the ti-adc084s021 chip

Submitted by Mårten Lindahl on April 21, 2017, 2:58 p.m.

Details

Message ID 1492786703-5149-1-git-send-email-marten.lindahl@axis.com
State New
Headers show

Commit Message

Mårten Lindahl April 21, 2017, 2:58 p.m.
From: Mårten Lindahl <martenli@axis.com>

This adds support for the Texas Instruments ADC084S021 ADC chip.

Signed-off-by: Mårten Lindahl <martenli@axis.com>
---
 .../devicetree/bindings/iio/adc/ti-adc084s021.txt  |  25 ++
 drivers/iio/adc/Kconfig                            |  12 +
 drivers/iio/adc/Makefile                           |   1 +
 drivers/iio/adc/ti-adc084s021.c                    | 342 +++++++++++++++++++++
 4 files changed, 380 insertions(+)
 create mode 100644 Documentation/devicetree/bindings/iio/adc/ti-adc084s021.txt
 create mode 100644 drivers/iio/adc/ti-adc084s021.c

Comments

Peter Meerwald April 21, 2017, 8:19 p.m.
> From: Mårten Lindahl <martenli@axis.com>

comments below
 
> This adds support for the Texas Instruments ADC084S021 ADC chip.
> 
> Signed-off-by: Mårten Lindahl <martenli@axis.com>
> ---
>  .../devicetree/bindings/iio/adc/ti-adc084s021.txt  |  25 ++
>  drivers/iio/adc/Kconfig                            |  12 +
>  drivers/iio/adc/Makefile                           |   1 +
>  drivers/iio/adc/ti-adc084s021.c                    | 342 +++++++++++++++++++++
>  4 files changed, 380 insertions(+)
>  create mode 100644 Documentation/devicetree/bindings/iio/adc/ti-adc084s021.txt
>  create mode 100644 drivers/iio/adc/ti-adc084s021.c
> 
> diff --git a/Documentation/devicetree/bindings/iio/adc/ti-adc084s021.txt b/Documentation/devicetree/bindings/iio/adc/ti-adc084s021.txt
> new file mode 100644
> index 0000000..921eb46
> --- /dev/null
> +++ b/Documentation/devicetree/bindings/iio/adc/ti-adc084s021.txt
> @@ -0,0 +1,25 @@
> +* Texas Instruments' ADC084S021
> +
> +Required properties:
> + - compatible        : Must be "ti,adc084s021"
> + - reg               : SPI chip select number for the device
> + - vref-supply       : The regulator supply for ADC reference voltage
> + - spi-max-frequency : Definition as per Documentation/devicetree/bindings/spi/spi-bus.txt
> +
> +Optional properties:
> + - spi-cpol          : SPI inverse clock polarity, as per spi-bus bindings
> + - spi-cpha          : SPI shifted clock phase (CPHA), as per spi-bus bindings
> + - spi-cs-high       : SPI chip select active high, as per spi-bus bindings
> +
> +
> +Example:
> +adc@0 {
> +	compatible = "ti,adc084s021";
> +	reg = <0>;
> +	vref-supply = <&adc_vref>;
> +	spi-cpol;
> +	spi-cpha;
> +	spi-cs-high;
> +	spi-max-frequency = <16000000>;
> +	pl022,com-mode = <0x2>; /* DMA */

what is this?

> +};
> diff --git a/drivers/iio/adc/Kconfig b/drivers/iio/adc/Kconfig
> index dedae7a..13141e5 100644
> --- a/drivers/iio/adc/Kconfig
> +++ b/drivers/iio/adc/Kconfig
> @@ -560,6 +560,18 @@ config TI_ADC0832
>  	  This driver can also be built as a module. If so, the module will be
>  	  called ti-adc0832.
>  
> +config TI_ADC084S021
> +	tristate "Texas Instruments ADC084S021"
> +	depends on SPI
> +	select IIO_BUFFER
> +	select IIO_TRIGGERED_BUFFER
> +	help
> +	  If you say yes here you get support for Texas Instruments ADC084S021
> +	  chips.
> +
> +	  This driver can also be built as a module. If so, the module will be
> +	  called ti-adc084s021.
> +
>  config TI_ADC12138
>  	tristate "Texas Instruments ADC12130/ADC12132/ADC12138"
>  	depends on SPI
> diff --git a/drivers/iio/adc/Makefile b/drivers/iio/adc/Makefile
> index d001262..b1a6158 100644
> --- a/drivers/iio/adc/Makefile
> +++ b/drivers/iio/adc/Makefile
> @@ -51,6 +51,7 @@ obj-$(CONFIG_STM32_ADC_CORE) += stm32-adc-core.o
>  obj-$(CONFIG_STM32_ADC) += stm32-adc.o
>  obj-$(CONFIG_TI_ADC081C) += ti-adc081c.o
>  obj-$(CONFIG_TI_ADC0832) += ti-adc0832.o
> +obj-$(CONFIG_TI_ADC084S021) += ti-adc084s021.o
>  obj-$(CONFIG_TI_ADC12138) += ti-adc12138.o
>  obj-$(CONFIG_TI_ADC128S052) += ti-adc128s052.o
>  obj-$(CONFIG_TI_ADC161S626) += ti-adc161s626.o
> diff --git a/drivers/iio/adc/ti-adc084s021.c b/drivers/iio/adc/ti-adc084s021.c
> new file mode 100644
> index 0000000..4f33b91
> --- /dev/null
> +++ b/drivers/iio/adc/ti-adc084s021.c
> @@ -0,0 +1,342 @@
> +/**
> + * Copyright (C) 2017 Axis Communications AB
> + *
> + * Driver for Texas Instruments' ADC084S021 ADC chip.
> + * Datasheets can be found here:
> + * http://www.ti.com/lit/ds/symlink/adc084s021.pdf
> + *
> + * This program is free software; you can redistribute it and/or modify
> + * it under the terms of the GNU General Public License version 2 as
> + * published by the Free Software Foundation.
> + */
> +
> +#include <linux/err.h>
> +#include <linux/spi/spi.h>
> +#include <linux/module.h>
> +#include <linux/interrupt.h>
> +#include <linux/iio/iio.h>
> +#include <linux/iio/buffer.h>
> +#include <linux/iio/events.h>
> +#include <linux/iio/triggered_buffer.h>
> +#include <linux/iio/trigger_consumer.h>
> +#include <linux/regulator/consumer.h>
> +
> +#define MODULE_NAME     "adc084s021"
> +#define DRIVER_VERSION  "1.0"

is only used once at the very end...

> +#define ADC_RESOLUTION  8
> +#define ADC_N_CHANNELS  4

we want a consistent prefix, such as ADC084S021_

> +
> +struct adc084s021_configuration {
> +	const struct iio_chan_spec *channels;
> +	u8 num_channels;

no need for u8, perhaps unsigned?

> +};
> +
> +struct adc084s021 {
> +	struct spi_device *spi;
> +	struct spi_message message;
> +	struct spi_transfer spi_trans[2];
> +	struct regulator *reg;
> +	struct mutex lock;
> +	/*
> +	 * DMA (thus cache coherency maintenance) requires the
> +	 * transfer buffers to live in their own cache lines.
> +	 */
> +	union {
> +		u8 tx_buf[2];
> +		u8 rx_buf[2];
> +	} ____cacheline_aligned;
> +	u8 cur_adc_values[ADC_N_CHANNELS];
> +};
> +
> +/**
> + * Event triggered when value changes on a channel
> + */
> +static const struct iio_event_spec adc084s021_event = {
> +	.type = IIO_EV_TYPE_CHANGE,
> +	.dir = IIO_EV_DIR_NONE,
> +};
> +
> +/**
> + * Channel specification
> + */
> +#define ADC084S021_VOLTAGE_CHANNEL(num)                  \
> +	{                                                      \
> +		.type = IIO_VOLTAGE,                                 \
> +		.channel = (num),                                    \
> +		.address = (num << 3),                               \

parenthesis should be around (num)

> +		.indexed = 1,                                        \
> +		.scan_index = num,                                   \

parenthesis?

> +		.scan_type = {                                       \
> +			.sign = 'u',                                       \
> +			.realbits = 8,                                     \
> +			.storagebits = 32,                                 \
> +			.shift = 24 - ((num << 3)),                        \

no need for (( )) around the expression, parenthesis should be around num

the shift doesn't make sense, you are shifting in 

adc084s021_adc_conversion() already and return just 8 bits (so storagebits 
should be 8)?

you could/should use realbits = 8, storagebits = 16, shift = 4 and 
endianness = IIO_BE if I read Figure 1 of the datasheet correctly

> +		},                                                   \
> +		.info_mask_separate = BIT(IIO_CHAN_INFO_RAW),        \

likely this is missing _SCALE
IIO expects data to be returned in millivolt, see 
Documentation/ABI/testing/sysfs-bus-iio

> +		.event_spec = &adc084s021_event,                     \
> +		.num_event_specs = 1,                                \

ARRAY_SIZE(&adc084s021_event) to be extensible?

> +	}
> +
> +static const struct iio_chan_spec adc084s021_channels[] = {
> +	ADC084S021_VOLTAGE_CHANNEL(0),
> +	ADC084S021_VOLTAGE_CHANNEL(1),
> +	ADC084S021_VOLTAGE_CHANNEL(2),
> +	ADC084S021_VOLTAGE_CHANNEL(3),
> +	IIO_CHAN_SOFT_TIMESTAMP(4),
> +};
> +
> +static const struct adc084s021_configuration adc084s021_config[] = {
> +	{ adc084s021_channels, ARRAY_SIZE(adc084s021_channels) },

for just one configuration, this is not really needed; so you plan/forsee 
more chips being added soonish?

> +};
> +
> +/**
> + * Read an ADC channel and return its value.
> + *
> + * @adc: The ADC SPI data.
> + * @channel: The IIO channel data structure.
> + */
> +static int adc084s021_adc_conversion(struct adc084s021 *adc,
> +			   struct iio_chan_spec const *channel)
> +{
> +	u16 value;

value should be u8, but is not really needed

> +	int ret;
> +
> +	mutex_lock(&adc->lock);
> +	adc->tx_buf[0] = channel->address;
> +
> +	/* Do the transfer */
> +	ret = spi_sync(adc->spi, &adc->message);
> +

no newline here please

> +	if (ret < 0) {
> +		mutex_unlock(&adc->lock);
> +		return ret;
> +	}
> +
> +	value = (adc->rx_buf[0] << 4) | (adc->rx_buf[1] >> 4);

I recommend using __be16 for rx_buf and
ret = (be16_to_cpu(adc->rx_buf) >> 4) & 0xff;

> +	mutex_unlock(&adc->lock);
> +
> +	dev_dbg(&adc->spi->dev, "value 0x%02X on channel %d\n",
> +			     value, channel->channel);
> +	return value;
> +}
> +
> +/**
> + * Make a readout of requested IIO channel info.

no need to document this, it is found in every IIO driver...

> + *
> + * @indio_dev: The industrial I/O device.
> + * @channel: The IIO channel data structure.
> + * @val: First element of value (integer).
> + * @val2: Second element of value (fractional).
> + * @mask: The info_mask to read.
> + */
> +static int adc084s021_read_raw(struct iio_dev *indio_dev,
> +			   struct iio_chan_spec const *channel, int *val,
> +			   int *val2, long mask)
> +{
> +	struct adc084s021 *adc = iio_priv(indio_dev);
> +	int retval;

how about using ret everywhere?

> +
> +	switch (mask) {
> +	case IIO_CHAN_INFO_RAW:

probably want iio_device_claim_direct_mode() so to not interfere with 
buffered access

> +		retval = adc084s021_adc_conversion(adc, channel);
> +		if (retval < 0)
> +			return retval;
> +
> +		*val = retval;
> +		return IIO_VAL_INT;
> +
> +	default:
> +		return -EINVAL;
> +	}
> +}
> +
> +/**
> + * Read enabled ADC channels and push data to the buffer.
> + *
> + * @irq: The interrupt number (not used).
> + * @pollfunc: Pointer to the poll func.
> + */
> +static irqreturn_t adc084s021_trigger_handler(int irq, void *pollfunc)
> +{
> +	struct iio_poll_func *pf = pollfunc;
> +	struct iio_dev *indio_dev = pf->indio_dev;
> +	struct adc084s021 *adc = iio_priv(indio_dev);
> +	u8 *data;
> +	s64 timestamp;
> +	int value, scan_index;
> +
> +	data = kzalloc(indio_dev->scan_bytes, GFP_KERNEL);

pre-allocate buffer with maximum size statically; allocation is 
potentially expensive; don't forget space for the timestamp and padding...

> +	if (!data) {
> +		iio_trigger_notify_done(indio_dev->trig);
> +		return IRQ_NONE;
> +	}
> +
> +	timestamp = iio_get_time_ns(indio_dev);
> +
> +	for_each_set_bit(scan_index, indio_dev->active_scan_mask,
> +			 indio_dev->masklength) {
> +		const struct iio_chan_spec *channel =
> +			&indio_dev->channels[scan_index];
> +		value = adc084s021_adc_conversion(adc, channel);

lock is taken and released for each channel, probably want to do it just 
once?

> +		data[scan_index] = value;
> +
> +		/*
> +		 * Compare read data to previous read. If it differs send
> +		 * event notification for affected channel.
> +		 */
> +		if (adc->cur_adc_values[scan_index] != (u8)value) {

cur_adc_values is not initialized (probably set to 0);
so on first read, should the notification be sent?

> +			adc->cur_adc_values[scan_index] = (u8)value;
> +			iio_push_event(indio_dev,
> +						  IIO_EVENT_CODE(IIO_VOLTAGE, 0,
> +						    IIO_NO_MOD, IIO_EV_DIR_NONE,
> +						    IIO_EV_TYPE_CHANGE,
> +						    channel->channel, 0, 0),
> +						  timestamp);
> +			dev_dbg(&indio_dev->dev,
> +					    "new value on ch%d: 0x%02X (ts %llu)\n",
> +					    channel->channel, value, timestamp);
> +		}
> +	}
> +
> +	iio_push_to_buffers_with_timestamp(indio_dev, data, timestamp);
> +	iio_trigger_notify_done(indio_dev->trig);
> +	kfree(data);
> +	return IRQ_HANDLED;
> +}
> +
> +static const struct iio_info adc084s021_info = {
> +	.read_raw = adc084s021_read_raw,
> +	.driver_module = THIS_MODULE,
> +};
> +
> +/**
> + * Create and register ADC IIO device for SPI.

comment is rather pointless

> + */
> +static int adc084s021_probe(struct spi_device *spi)
> +{
> +	struct iio_dev *indio_dev;
> +	struct adc084s021 *adc;
> +	int config = spi_get_device_id(spi)->driver_data;
> +	int retval;

ret maybe

> +
> +	/* Allocate an Industrial I/O device */

obviously...

> +	indio_dev = devm_iio_device_alloc(&spi->dev, sizeof(*adc));
> +	if (!indio_dev) {
> +		dev_err(&spi->dev, "Failed to allocate IIO device\n");
> +		return -ENOMEM;
> +	}
> +
> +	adc = iio_priv(indio_dev);
> +	adc->spi = spi;
> +	spi->bits_per_word = ADC_RESOLUTION;
> +
> +	/* Update the SPI device with config and connect the iio dev */
> +	retval = spi_setup(spi);
> +	if (retval) {
> +		dev_err(&spi->dev, "Failed to update SPI device\n");
> +		return retval;
> +	}
> +	spi_set_drvdata(spi, indio_dev);
> +
> +	/* Initiate the Industrial I/O device */
> +	indio_dev->dev.parent = &spi->dev;
> +	indio_dev->dev.of_node = spi->dev.of_node;
> +	indio_dev->name = spi_get_device_id(spi)->name;
> +	indio_dev->modes = INDIO_DIRECT_MODE;
> +	indio_dev->info = &adc084s021_info;
> +	indio_dev->channels = adc084s021_config[config].channels;
> +	indio_dev->num_channels = adc084s021_config[config].num_channels;

could do it directly as long there is just one configuration

> +
> +	/* Create SPI transfer for channel reads */
> +	adc->spi_trans[0].tx_buf = &adc->tx_buf[0];
> +	adc->spi_trans[0].len = 2;
> +	adc->spi_trans[0].speed_hz = spi->max_speed_hz;
> +	adc->spi_trans[0].bits_per_word = spi->bits_per_word;
> +	adc->spi_trans[1].rx_buf = &adc->rx_buf[0];
> +	adc->spi_trans[1].len = 2;
> +	adc->spi_trans[1].speed_hz = spi->max_speed_hz;
> +	adc->spi_trans[1].bits_per_word = spi->bits_per_word;
> +
> +	/* Setup SPI message for channel reads */
> +	spi_message_init(&adc->message);
> +	spi_message_add_tail(&adc->spi_trans[0], &adc->message);
> +	spi_message_add_tail(&adc->spi_trans[1], &adc->message);
> +
> +	adc->reg = devm_regulator_get(&spi->dev, "vref");
> +	if (IS_ERR(adc->reg))
> +		return PTR_ERR(adc->reg);
> +
> +	retval = regulator_enable(adc->reg);
> +	if (retval < 0)
> +		return retval;
> +
> +	mutex_init(&adc->lock);
> +
> +	/* Setup triggered buffer with pollfunction */
> +	retval = iio_triggered_buffer_setup(indio_dev, NULL,

devm_()

> +					    adc084s021_trigger_handler, NULL);
> +	if (retval) {
> +		dev_err(&spi->dev, "Failed to setup triggered buffer\n");
> +		goto buffer_setup_failed;
> +	}
> +
> +	retval = iio_device_register(indio_dev);
> +	if (retval) {
> +		dev_err(&spi->dev, "Failed to register IIO device\n");
> +		goto device_register_failed;
> +	}
> +
> +	dev_info(&spi->dev, "probed!\n");

no logging please, just outputs clutter

> +	return 0;
> +
> +device_register_failed:
> +	iio_triggered_buffer_cleanup(indio_dev);
> +buffer_setup_failed:
> +	regulator_disable(adc->reg);
> +	return retval;
> +}
> +
> +/**
> + * Unregister ADC IIO device for SPI.
> + */
> +static int adc084s021_remove(struct spi_device *spi)
> +{
> +	struct iio_dev *indio_dev = spi_get_drvdata(spi);
> +	struct adc084s021 *adc = iio_priv(indio_dev);
> +
> +	iio_device_unregister(indio_dev);
> +	iio_triggered_buffer_cleanup(indio_dev);
> +	regulator_disable(adc->reg);
> +	return 0;
> +}
> +
> +static const struct of_device_id adc084s021_of_match[] = {
> +	{ .compatible = "ti,adc084s021", },
> +	{},
> +};
> +
> +MODULE_DEVICE_TABLE(of, adc084s021_of_match);
> +
> +static const struct spi_device_id adc084s021_id[] = {
> +	{ MODULE_NAME, 0},
> +	{}
> +};
> +
> +MODULE_DEVICE_TABLE(spi, adc084s021_id);
> +
> +static struct spi_driver adc084s021_driver = {
> +	.driver = {
> +		.name = MODULE_NAME,
> +		.of_match_table = of_match_ptr(adc084s021_of_match),
> +	},
> +	.probe = adc084s021_probe,
> +	.remove = adc084s021_remove,
> +	.id_table = adc084s021_id,
> +};
> +
> +module_spi_driver(adc084s021_driver);
> +
> +MODULE_AUTHOR("Mårten Lindahl <martenli@axis.com>");
> +MODULE_DESCRIPTION("Texas Instruments ADC084S021");
> +MODULE_LICENSE("GPL v2");
> +MODULE_VERSION(DRIVER_VERSION);
>

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diff --git a/Documentation/devicetree/bindings/iio/adc/ti-adc084s021.txt b/Documentation/devicetree/bindings/iio/adc/ti-adc084s021.txt
new file mode 100644
index 0000000..921eb46
--- /dev/null
+++ b/Documentation/devicetree/bindings/iio/adc/ti-adc084s021.txt
@@ -0,0 +1,25 @@ 
+* Texas Instruments' ADC084S021
+
+Required properties:
+ - compatible        : Must be "ti,adc084s021"
+ - reg               : SPI chip select number for the device
+ - vref-supply       : The regulator supply for ADC reference voltage
+ - spi-max-frequency : Definition as per Documentation/devicetree/bindings/spi/spi-bus.txt
+
+Optional properties:
+ - spi-cpol          : SPI inverse clock polarity, as per spi-bus bindings
+ - spi-cpha          : SPI shifted clock phase (CPHA), as per spi-bus bindings
+ - spi-cs-high       : SPI chip select active high, as per spi-bus bindings
+
+
+Example:
+adc@0 {
+	compatible = "ti,adc084s021";
+	reg = <0>;
+	vref-supply = <&adc_vref>;
+	spi-cpol;
+	spi-cpha;
+	spi-cs-high;
+	spi-max-frequency = <16000000>;
+	pl022,com-mode = <0x2>; /* DMA */
+};
diff --git a/drivers/iio/adc/Kconfig b/drivers/iio/adc/Kconfig
index dedae7a..13141e5 100644
--- a/drivers/iio/adc/Kconfig
+++ b/drivers/iio/adc/Kconfig
@@ -560,6 +560,18 @@  config TI_ADC0832
 	  This driver can also be built as a module. If so, the module will be
 	  called ti-adc0832.
 
+config TI_ADC084S021
+	tristate "Texas Instruments ADC084S021"
+	depends on SPI
+	select IIO_BUFFER
+	select IIO_TRIGGERED_BUFFER
+	help
+	  If you say yes here you get support for Texas Instruments ADC084S021
+	  chips.
+
+	  This driver can also be built as a module. If so, the module will be
+	  called ti-adc084s021.
+
 config TI_ADC12138
 	tristate "Texas Instruments ADC12130/ADC12132/ADC12138"
 	depends on SPI
diff --git a/drivers/iio/adc/Makefile b/drivers/iio/adc/Makefile
index d001262..b1a6158 100644
--- a/drivers/iio/adc/Makefile
+++ b/drivers/iio/adc/Makefile
@@ -51,6 +51,7 @@  obj-$(CONFIG_STM32_ADC_CORE) += stm32-adc-core.o
 obj-$(CONFIG_STM32_ADC) += stm32-adc.o
 obj-$(CONFIG_TI_ADC081C) += ti-adc081c.o
 obj-$(CONFIG_TI_ADC0832) += ti-adc0832.o
+obj-$(CONFIG_TI_ADC084S021) += ti-adc084s021.o
 obj-$(CONFIG_TI_ADC12138) += ti-adc12138.o
 obj-$(CONFIG_TI_ADC128S052) += ti-adc128s052.o
 obj-$(CONFIG_TI_ADC161S626) += ti-adc161s626.o
diff --git a/drivers/iio/adc/ti-adc084s021.c b/drivers/iio/adc/ti-adc084s021.c
new file mode 100644
index 0000000..4f33b91
--- /dev/null
+++ b/drivers/iio/adc/ti-adc084s021.c
@@ -0,0 +1,342 @@ 
+/**
+ * Copyright (C) 2017 Axis Communications AB
+ *
+ * Driver for Texas Instruments' ADC084S021 ADC chip.
+ * Datasheets can be found here:
+ * http://www.ti.com/lit/ds/symlink/adc084s021.pdf
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License version 2 as
+ * published by the Free Software Foundation.
+ */
+
+#include <linux/err.h>
+#include <linux/spi/spi.h>
+#include <linux/module.h>
+#include <linux/interrupt.h>
+#include <linux/iio/iio.h>
+#include <linux/iio/buffer.h>
+#include <linux/iio/events.h>
+#include <linux/iio/triggered_buffer.h>
+#include <linux/iio/trigger_consumer.h>
+#include <linux/regulator/consumer.h>
+
+#define MODULE_NAME     "adc084s021"
+#define DRIVER_VERSION  "1.0"
+#define ADC_RESOLUTION  8
+#define ADC_N_CHANNELS  4
+
+struct adc084s021_configuration {
+	const struct iio_chan_spec *channels;
+	u8 num_channels;
+};
+
+struct adc084s021 {
+	struct spi_device *spi;
+	struct spi_message message;
+	struct spi_transfer spi_trans[2];
+	struct regulator *reg;
+	struct mutex lock;
+	/*
+	 * DMA (thus cache coherency maintenance) requires the
+	 * transfer buffers to live in their own cache lines.
+	 */
+	union {
+		u8 tx_buf[2];
+		u8 rx_buf[2];
+	} ____cacheline_aligned;
+	u8 cur_adc_values[ADC_N_CHANNELS];
+};
+
+/**
+ * Event triggered when value changes on a channel
+ */
+static const struct iio_event_spec adc084s021_event = {
+	.type = IIO_EV_TYPE_CHANGE,
+	.dir = IIO_EV_DIR_NONE,
+};
+
+/**
+ * Channel specification
+ */
+#define ADC084S021_VOLTAGE_CHANNEL(num)                  \
+	{                                                      \
+		.type = IIO_VOLTAGE,                                 \
+		.channel = (num),                                    \
+		.address = (num << 3),                               \
+		.indexed = 1,                                        \
+		.scan_index = num,                                   \
+		.scan_type = {                                       \
+			.sign = 'u',                                       \
+			.realbits = 8,                                     \
+			.storagebits = 32,                                 \
+			.shift = 24 - ((num << 3)),                        \
+		},                                                   \
+		.info_mask_separate = BIT(IIO_CHAN_INFO_RAW),        \
+		.event_spec = &adc084s021_event,                     \
+		.num_event_specs = 1,                                \
+	}
+
+static const struct iio_chan_spec adc084s021_channels[] = {
+	ADC084S021_VOLTAGE_CHANNEL(0),
+	ADC084S021_VOLTAGE_CHANNEL(1),
+	ADC084S021_VOLTAGE_CHANNEL(2),
+	ADC084S021_VOLTAGE_CHANNEL(3),
+	IIO_CHAN_SOFT_TIMESTAMP(4),
+};
+
+static const struct adc084s021_configuration adc084s021_config[] = {
+	{ adc084s021_channels, ARRAY_SIZE(adc084s021_channels) },
+};
+
+/**
+ * Read an ADC channel and return its value.
+ *
+ * @adc: The ADC SPI data.
+ * @channel: The IIO channel data structure.
+ */
+static int adc084s021_adc_conversion(struct adc084s021 *adc,
+			   struct iio_chan_spec const *channel)
+{
+	u16 value;
+	int ret;
+
+	mutex_lock(&adc->lock);
+	adc->tx_buf[0] = channel->address;
+
+	/* Do the transfer */
+	ret = spi_sync(adc->spi, &adc->message);
+
+	if (ret < 0) {
+		mutex_unlock(&adc->lock);
+		return ret;
+	}
+
+	value = (adc->rx_buf[0] << 4) | (adc->rx_buf[1] >> 4);
+	mutex_unlock(&adc->lock);
+
+	dev_dbg(&adc->spi->dev, "value 0x%02X on channel %d\n",
+			     value, channel->channel);
+	return value;
+}
+
+/**
+ * Make a readout of requested IIO channel info.
+ *
+ * @indio_dev: The industrial I/O device.
+ * @channel: The IIO channel data structure.
+ * @val: First element of value (integer).
+ * @val2: Second element of value (fractional).
+ * @mask: The info_mask to read.
+ */
+static int adc084s021_read_raw(struct iio_dev *indio_dev,
+			   struct iio_chan_spec const *channel, int *val,
+			   int *val2, long mask)
+{
+	struct adc084s021 *adc = iio_priv(indio_dev);
+	int retval;
+
+	switch (mask) {
+	case IIO_CHAN_INFO_RAW:
+		retval = adc084s021_adc_conversion(adc, channel);
+		if (retval < 0)
+			return retval;
+
+		*val = retval;
+		return IIO_VAL_INT;
+
+	default:
+		return -EINVAL;
+	}
+}
+
+/**
+ * Read enabled ADC channels and push data to the buffer.
+ *
+ * @irq: The interrupt number (not used).
+ * @pollfunc: Pointer to the poll func.
+ */
+static irqreturn_t adc084s021_trigger_handler(int irq, void *pollfunc)
+{
+	struct iio_poll_func *pf = pollfunc;
+	struct iio_dev *indio_dev = pf->indio_dev;
+	struct adc084s021 *adc = iio_priv(indio_dev);
+	u8 *data;
+	s64 timestamp;
+	int value, scan_index;
+
+	data = kzalloc(indio_dev->scan_bytes, GFP_KERNEL);
+	if (!data) {
+		iio_trigger_notify_done(indio_dev->trig);
+		return IRQ_NONE;
+	}
+
+	timestamp = iio_get_time_ns(indio_dev);
+
+	for_each_set_bit(scan_index, indio_dev->active_scan_mask,
+			 indio_dev->masklength) {
+		const struct iio_chan_spec *channel =
+			&indio_dev->channels[scan_index];
+		value = adc084s021_adc_conversion(adc, channel);
+		data[scan_index] = value;
+
+		/*
+		 * Compare read data to previous read. If it differs send
+		 * event notification for affected channel.
+		 */
+		if (adc->cur_adc_values[scan_index] != (u8)value) {
+			adc->cur_adc_values[scan_index] = (u8)value;
+			iio_push_event(indio_dev,
+						  IIO_EVENT_CODE(IIO_VOLTAGE, 0,
+						    IIO_NO_MOD, IIO_EV_DIR_NONE,
+						    IIO_EV_TYPE_CHANGE,
+						    channel->channel, 0, 0),
+						  timestamp);
+			dev_dbg(&indio_dev->dev,
+					    "new value on ch%d: 0x%02X (ts %llu)\n",
+					    channel->channel, value, timestamp);
+		}
+	}
+
+	iio_push_to_buffers_with_timestamp(indio_dev, data, timestamp);
+	iio_trigger_notify_done(indio_dev->trig);
+	kfree(data);
+	return IRQ_HANDLED;
+}
+
+static const struct iio_info adc084s021_info = {
+	.read_raw = adc084s021_read_raw,
+	.driver_module = THIS_MODULE,
+};
+
+/**
+ * Create and register ADC IIO device for SPI.
+ */
+static int adc084s021_probe(struct spi_device *spi)
+{
+	struct iio_dev *indio_dev;
+	struct adc084s021 *adc;
+	int config = spi_get_device_id(spi)->driver_data;
+	int retval;
+
+	/* Allocate an Industrial I/O device */
+	indio_dev = devm_iio_device_alloc(&spi->dev, sizeof(*adc));
+	if (!indio_dev) {
+		dev_err(&spi->dev, "Failed to allocate IIO device\n");
+		return -ENOMEM;
+	}
+
+	adc = iio_priv(indio_dev);
+	adc->spi = spi;
+	spi->bits_per_word = ADC_RESOLUTION;
+
+	/* Update the SPI device with config and connect the iio dev */
+	retval = spi_setup(spi);
+	if (retval) {
+		dev_err(&spi->dev, "Failed to update SPI device\n");
+		return retval;
+	}
+	spi_set_drvdata(spi, indio_dev);
+
+	/* Initiate the Industrial I/O device */
+	indio_dev->dev.parent = &spi->dev;
+	indio_dev->dev.of_node = spi->dev.of_node;
+	indio_dev->name = spi_get_device_id(spi)->name;
+	indio_dev->modes = INDIO_DIRECT_MODE;
+	indio_dev->info = &adc084s021_info;
+	indio_dev->channels = adc084s021_config[config].channels;
+	indio_dev->num_channels = adc084s021_config[config].num_channels;
+
+	/* Create SPI transfer for channel reads */
+	adc->spi_trans[0].tx_buf = &adc->tx_buf[0];
+	adc->spi_trans[0].len = 2;
+	adc->spi_trans[0].speed_hz = spi->max_speed_hz;
+	adc->spi_trans[0].bits_per_word = spi->bits_per_word;
+	adc->spi_trans[1].rx_buf = &adc->rx_buf[0];
+	adc->spi_trans[1].len = 2;
+	adc->spi_trans[1].speed_hz = spi->max_speed_hz;
+	adc->spi_trans[1].bits_per_word = spi->bits_per_word;
+
+	/* Setup SPI message for channel reads */
+	spi_message_init(&adc->message);
+	spi_message_add_tail(&adc->spi_trans[0], &adc->message);
+	spi_message_add_tail(&adc->spi_trans[1], &adc->message);
+
+	adc->reg = devm_regulator_get(&spi->dev, "vref");
+	if (IS_ERR(adc->reg))
+		return PTR_ERR(adc->reg);
+
+	retval = regulator_enable(adc->reg);
+	if (retval < 0)
+		return retval;
+
+	mutex_init(&adc->lock);
+
+	/* Setup triggered buffer with pollfunction */
+	retval = iio_triggered_buffer_setup(indio_dev, NULL,
+					    adc084s021_trigger_handler, NULL);
+	if (retval) {
+		dev_err(&spi->dev, "Failed to setup triggered buffer\n");
+		goto buffer_setup_failed;
+	}
+
+	retval = iio_device_register(indio_dev);
+	if (retval) {
+		dev_err(&spi->dev, "Failed to register IIO device\n");
+		goto device_register_failed;
+	}
+
+	dev_info(&spi->dev, "probed!\n");
+	return 0;
+
+device_register_failed:
+	iio_triggered_buffer_cleanup(indio_dev);
+buffer_setup_failed:
+	regulator_disable(adc->reg);
+	return retval;
+}
+
+/**
+ * Unregister ADC IIO device for SPI.
+ */
+static int adc084s021_remove(struct spi_device *spi)
+{
+	struct iio_dev *indio_dev = spi_get_drvdata(spi);
+	struct adc084s021 *adc = iio_priv(indio_dev);
+
+	iio_device_unregister(indio_dev);
+	iio_triggered_buffer_cleanup(indio_dev);
+	regulator_disable(adc->reg);
+	return 0;
+}
+
+static const struct of_device_id adc084s021_of_match[] = {
+	{ .compatible = "ti,adc084s021", },
+	{},
+};
+
+MODULE_DEVICE_TABLE(of, adc084s021_of_match);
+
+static const struct spi_device_id adc084s021_id[] = {
+	{ MODULE_NAME, 0},
+	{}
+};
+
+MODULE_DEVICE_TABLE(spi, adc084s021_id);
+
+static struct spi_driver adc084s021_driver = {
+	.driver = {
+		.name = MODULE_NAME,
+		.of_match_table = of_match_ptr(adc084s021_of_match),
+	},
+	.probe = adc084s021_probe,
+	.remove = adc084s021_remove,
+	.id_table = adc084s021_id,
+};
+
+module_spi_driver(adc084s021_driver);
+
+MODULE_AUTHOR("Mårten Lindahl <martenli@axis.com>");
+MODULE_DESCRIPTION("Texas Instruments ADC084S021");
+MODULE_LICENSE("GPL v2");
+MODULE_VERSION(DRIVER_VERSION);