drivers/iio/adc/nau7802.c - kernel/msm-4.9 - Gitiles

 /*
  * Driver for the Nuvoton NAU7802 ADC
  *
  * Copyright 2013 Free Electrons
  *
  * Licensed under the GPLv2 or later.
  */

 #include <linux/delay.h>
 #include <linux/i2c.h>
 #include <linux/interrupt.h>
 #include <linux/module.h>
 #include <linux/wait.h>
 #include <linux/log2.h>

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

 #define NAU7802_REG_PUCTRL	0x00
 #define NAU7802_PUCTRL_RR(x)		(x << 0)
 #define NAU7802_PUCTRL_RR_BIT		NAU7802_PUCTRL_RR(1)
 #define NAU7802_PUCTRL_PUD(x)		(x << 1)
 #define NAU7802_PUCTRL_PUD_BIT		NAU7802_PUCTRL_PUD(1)
 #define NAU7802_PUCTRL_PUA(x)		(x << 2)
 #define NAU7802_PUCTRL_PUA_BIT		NAU7802_PUCTRL_PUA(1)
 #define NAU7802_PUCTRL_PUR(x)		(x << 3)
 #define NAU7802_PUCTRL_PUR_BIT		NAU7802_PUCTRL_PUR(1)
 #define NAU7802_PUCTRL_CS(x)		(x << 4)
 #define NAU7802_PUCTRL_CS_BIT		NAU7802_PUCTRL_CS(1)
 #define NAU7802_PUCTRL_CR(x)		(x << 5)
 #define NAU7802_PUCTRL_CR_BIT		NAU7802_PUCTRL_CR(1)
 #define NAU7802_PUCTRL_AVDDS(x)		(x << 7)
 #define NAU7802_PUCTRL_AVDDS_BIT	NAU7802_PUCTRL_AVDDS(1)
 #define NAU7802_REG_CTRL1	0x01
 #define NAU7802_CTRL1_VLDO(x)		(x << 3)
 #define NAU7802_CTRL1_GAINS(x)		(x)
 #define NAU7802_CTRL1_GAINS_BITS	0x07
 #define NAU7802_REG_CTRL2	0x02
 #define NAU7802_CTRL2_CHS(x)		(x << 7)
 #define NAU7802_CTRL2_CRS(x)		(x << 4)
 #define NAU7802_SAMP_FREQ_320	0x07
 #define NAU7802_CTRL2_CHS_BIT		NAU7802_CTRL2_CHS(1)
 #define NAU7802_REG_ADC_B2	0x12
 #define NAU7802_REG_ADC_B1	0x13
 #define NAU7802_REG_ADC_B0	0x14
 #define NAU7802_REG_ADC_CTRL	0x15

 #define NAU7802_MIN_CONVERSIONS 6

 struct nau7802_state {
 	struct i2c_client	*client;
 	s32			last_value;
 	struct mutex		lock;
 	struct mutex		data_lock;
 	u32			vref_mv;
 	u32			conversion_count;
 	u32			min_conversions;
 	u8			sample_rate;
 	u32			scale_avail[8];
 	struct completion	value_ok;
 };

 #define NAU7802_CHANNEL(chan) {					\
 	.type = IIO_VOLTAGE,					\
 	.indexed = 1,						\
 	.channel = (chan),					\
 	.scan_index = (chan),					\
 	.info_mask_separate = BIT(IIO_CHAN_INFO_RAW),		\
 	.info_mask_shared_by_type = BIT(IIO_CHAN_INFO_SCALE) |	\
 				BIT(IIO_CHAN_INFO_SAMP_FREQ)	\
 }

 static const struct iio_chan_spec nau7802_chan_array[] = {
 	NAU7802_CHANNEL(0),
 	NAU7802_CHANNEL(1),
 };

 static const u16 nau7802_sample_freq_avail[] = {10, 20, 40, 80,
 						10, 10, 10, 320};

 static IIO_CONST_ATTR_SAMP_FREQ_AVAIL("10 40 80 320");

 static struct attribute *nau7802_attributes[] = {
 	&iio_const_attr_sampling_frequency_available.dev_attr.attr,
 	NULL
 };

 static const struct attribute_group nau7802_attribute_group = {
 	.attrs = nau7802_attributes,
 };

 static int nau7802_set_gain(struct nau7802_state *st, int gain)
 {
 	int ret;

 	mutex_lock(&st->lock);
 	st->conversion_count = 0;

 	ret = i2c_smbus_read_byte_data(st->client, NAU7802_REG_CTRL1);
 	if (ret < 0)
 		goto nau7802_sysfs_set_gain_out;
 	ret = i2c_smbus_write_byte_data(st->client, NAU7802_REG_CTRL1,
 					(ret & (~NAU7802_CTRL1_GAINS_BITS)) |
 					gain);

 nau7802_sysfs_set_gain_out:
 	mutex_unlock(&st->lock);

 	return ret;
 }

 static int nau7802_read_conversion(struct nau7802_state *st)
 {
 	int data;

 	mutex_lock(&st->data_lock);
 	data = i2c_smbus_read_byte_data(st->client, NAU7802_REG_ADC_B2);
 	if (data < 0)
 		goto nau7802_read_conversion_out;
 	st->last_value = data << 16;

 	data = i2c_smbus_read_byte_data(st->client, NAU7802_REG_ADC_B1);
 	if (data < 0)
 		goto nau7802_read_conversion_out;
 	st->last_value |= data << 8;

 	data = i2c_smbus_read_byte_data(st->client, NAU7802_REG_ADC_B0);
 	if (data < 0)
 		goto nau7802_read_conversion_out;
 	st->last_value |= data;

 	st->last_value = sign_extend32(st->last_value, 23);

 nau7802_read_conversion_out:
 	mutex_unlock(&st->data_lock);

 	return data;
 }

 /*
  * Conversions are synchronised on the rising edge of NAU7802_PUCTRL_CS_BIT
  */
 static int nau7802_sync(struct nau7802_state *st)
 {
 	int ret;

 	ret = i2c_smbus_read_byte_data(st->client, NAU7802_REG_PUCTRL);
 	if (ret < 0)
 		return ret;
 	ret = i2c_smbus_write_byte_data(st->client, NAU7802_REG_PUCTRL,
 				ret | NAU7802_PUCTRL_CS_BIT);

 	return ret;
 }

 static irqreturn_t nau7802_eoc_trigger(int irq, void *private)
 {
 	struct iio_dev *indio_dev = private;
 	struct nau7802_state *st = iio_priv(indio_dev);
 	int status;

 	status = i2c_smbus_read_byte_data(st->client, NAU7802_REG_PUCTRL);
 	if (status < 0)
 		return IRQ_HANDLED;

 	if (!(status & NAU7802_PUCTRL_CR_BIT))
 		return IRQ_NONE;

 	if (nau7802_read_conversion(st) < 0)
 		return IRQ_HANDLED;

 	/*
 	 * Because there is actually only one ADC for both channels, we have to
 	 * wait for enough conversions to happen before getting a significant
 	 * value when changing channels and the values are far apart.
 	 */
 	if (st->conversion_count < NAU7802_MIN_CONVERSIONS)
 		st->conversion_count++;
 	if (st->conversion_count >= NAU7802_MIN_CONVERSIONS)
 		complete_all(&st->value_ok);

 	return IRQ_HANDLED;
 }

 static int nau7802_read_irq(struct iio_dev *indio_dev,
 			struct iio_chan_spec const *chan,
 			int *val)
 {
 	struct nau7802_state *st = iio_priv(indio_dev);
 	int ret;

 	INIT_COMPLETION(st->value_ok);
 	enable_irq(st->client->irq);

 	nau7802_sync(st);

 	/* read registers to ensure we flush everything */
 	ret = nau7802_read_conversion(st);
 	if (ret < 0)
 		goto read_chan_info_failure;

 	/* Wait for a conversion to finish */
 	ret = wait_for_completion_interruptible_timeout(&st->value_ok,
 			msecs_to_jiffies(1000));
 	if (ret == 0)
 		ret = -ETIMEDOUT;

 	if (ret < 0)
 		goto read_chan_info_failure;

 	disable_irq(st->client->irq);

 	*val = st->last_value;

 	return IIO_VAL_INT;

 read_chan_info_failure:
 	disable_irq(st->client->irq);

 	return ret;
 }

 static int nau7802_read_poll(struct iio_dev *indio_dev,
 			struct iio_chan_spec const *chan,
 			int *val)
 {
 	struct nau7802_state *st = iio_priv(indio_dev);
 	int ret;

 	nau7802_sync(st);

 	/* read registers to ensure we flush everything */
 	ret = nau7802_read_conversion(st);
 	if (ret < 0)
 		return ret;

 	/*
 	 * Because there is actually only one ADC for both channels, we have to
 	 * wait for enough conversions to happen before getting a significant
 	 * value when changing channels and the values are far appart.
 	 */
 	do {
 		ret = i2c_smbus_read_byte_data(st->client, NAU7802_REG_PUCTRL);
 		if (ret < 0)
 			return ret;

 		while (!(ret & NAU7802_PUCTRL_CR_BIT)) {
 			if (st->sample_rate != NAU7802_SAMP_FREQ_320)
 				msleep(20);
 			else
 				mdelay(4);
 			ret = i2c_smbus_read_byte_data(st->client,
 							NAU7802_REG_PUCTRL);
 			if (ret < 0)
 				return ret;
 		}

 		ret = nau7802_read_conversion(st);
 		if (ret < 0)
 			return ret;
 		if (st->conversion_count < NAU7802_MIN_CONVERSIONS)
 			st->conversion_count++;
 	} while (st->conversion_count < NAU7802_MIN_CONVERSIONS);

 	*val = st->last_value;

 	return IIO_VAL_INT;
 }

 static int nau7802_read_raw(struct iio_dev *indio_dev,
 			    struct iio_chan_spec const *chan,
 			    int *val, int *val2, long mask)
 {
 	struct nau7802_state *st = iio_priv(indio_dev);
 	int ret;

 	switch (mask) {
 	case IIO_CHAN_INFO_RAW:
 		mutex_lock(&st->lock);
 		/*
 		 * Select the channel to use
 		 *   - Channel 1 is value 0 in the CHS register
 		 *   - Channel 2 is value 1 in the CHS register
 		 */
 		ret = i2c_smbus_read_byte_data(st->client, NAU7802_REG_CTRL2);
 		if (ret < 0) {
 			mutex_unlock(&st->lock);
 			return ret;
 		}

 		if (((ret & NAU7802_CTRL2_CHS_BIT) && !chan->channel) ||
 				(!(ret & NAU7802_CTRL2_CHS_BIT) &&
 				 chan->channel)) {
 			st->conversion_count = 0;
 			ret = i2c_smbus_write_byte_data(st->client,
 					NAU7802_REG_CTRL2,
 					NAU7802_CTRL2_CHS(chan->channel) |
 					NAU7802_CTRL2_CRS(st->sample_rate));

 			if (ret < 0) {
 				mutex_unlock(&st->lock);
 				return ret;
 			}
 		}

 		if (st->client->irq)
 			ret = nau7802_read_irq(indio_dev, chan, val);
 		else
 			ret = nau7802_read_poll(indio_dev, chan, val);

 		mutex_unlock(&st->lock);
 		return ret;

 	case IIO_CHAN_INFO_SCALE:
 		ret = i2c_smbus_read_byte_data(st->client, NAU7802_REG_CTRL1);
 		if (ret < 0)
 			return ret;

 		/*
 		 * We have 24 bits of signed data, that means 23 bits of data
 		 * plus the sign bit
 		 */
 		*val = st->vref_mv;
 		*val2 = 23 + (ret & NAU7802_CTRL1_GAINS_BITS);

 		return IIO_VAL_FRACTIONAL_LOG2;

 	case IIO_CHAN_INFO_SAMP_FREQ:
 		*val =  nau7802_sample_freq_avail[st->sample_rate];
 		*val2 = 0;
 		return IIO_VAL_INT;

 	default:
 		break;
 	}

 	return -EINVAL;
 }

 static int nau7802_write_raw(struct iio_dev *indio_dev,
 			     struct iio_chan_spec const *chan,
 			     int val, int val2, long mask)
 {
 	struct nau7802_state *st = iio_priv(indio_dev);
 	int i, ret;

 	switch (mask) {
 	case IIO_CHAN_INFO_SCALE:
 		for (i = 0; i < ARRAY_SIZE(st->scale_avail); i++)
 			if (val2 == st->scale_avail[i])
 				return nau7802_set_gain(st, i);

 		break;

 	case IIO_CHAN_INFO_SAMP_FREQ:
 		for (i = 0; i < ARRAY_SIZE(nau7802_sample_freq_avail); i++)
 			if (val == nau7802_sample_freq_avail[i]) {
 				mutex_lock(&st->lock);
 				st->sample_rate = i;
 				st->conversion_count = 0;
 				ret = i2c_smbus_write_byte_data(st->client,
 					NAU7802_REG_CTRL2,
 					NAU7802_CTRL2_CRS(st->sample_rate));
 				mutex_unlock(&st->lock);
 				return ret;
 			}

 		break;

 	default:
 		break;
 	}

 	return -EINVAL;
 }

 static int nau7802_write_raw_get_fmt(struct iio_dev *indio_dev,
 				     struct iio_chan_spec const *chan,
 				     long mask)
 {
 	return IIO_VAL_INT_PLUS_NANO;
 }

 static const struct iio_info nau7802_info = {
 	.driver_module = THIS_MODULE,
 	.read_raw = &nau7802_read_raw,
 	.write_raw = &nau7802_write_raw,
 	.write_raw_get_fmt = nau7802_write_raw_get_fmt,
 	.attrs = &nau7802_attribute_group,
 };

 static int nau7802_probe(struct i2c_client *client,
 			const struct i2c_device_id *id)
 {
 	struct iio_dev *indio_dev;
 	struct nau7802_state *st;
 	struct device_node *np = client->dev.of_node;
 	int i, ret;
 	u8 data;
 	u32 tmp = 0;

 	if (!client->dev.of_node) {
 		dev_err(&client->dev, "No device tree node available.\n");
 		return -EINVAL;
 	}

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

 	st = iio_priv(indio_dev);

 	i2c_set_clientdata(client, indio_dev);

 	indio_dev->dev.parent = &client->dev;
 	indio_dev->name = dev_name(&client->dev);
 	indio_dev->modes = INDIO_DIRECT_MODE;
 	indio_dev->info = &nau7802_info;

 	st->client = client;

 	/* Reset the device */
 	ret = i2c_smbus_write_byte_data(st->client, NAU7802_REG_PUCTRL,
 				  NAU7802_PUCTRL_RR_BIT);
 	if (ret < 0)
 		return ret;

 	/* Enter normal operation mode */
 	ret = i2c_smbus_write_byte_data(st->client, NAU7802_REG_PUCTRL,
 				  NAU7802_PUCTRL_PUD_BIT);
 	if (ret < 0)
 		return ret;

 	/*
 	 * After about 200 usecs, the device should be ready and then
 	 * the Power Up bit will be set to 1. If not, wait for it.
 	 */
 	udelay(210);
 	ret = i2c_smbus_read_byte_data(st->client, NAU7802_REG_PUCTRL);
 	if (ret < 0)
 		return ret;
 	if (!(ret & NAU7802_PUCTRL_PUR_BIT))
 		return ret;

 	of_property_read_u32(np, "nuvoton,vldo", &tmp);
 	st->vref_mv = tmp;

 	data = NAU7802_PUCTRL_PUD_BIT | NAU7802_PUCTRL_PUA_BIT |
 		NAU7802_PUCTRL_CS_BIT;
 	if (tmp >= 2400)
 		data |= NAU7802_PUCTRL_AVDDS_BIT;

 	ret = i2c_smbus_write_byte_data(st->client, NAU7802_REG_PUCTRL, data);
 	if (ret < 0)
 		return ret;
 	ret = i2c_smbus_write_byte_data(st->client, NAU7802_REG_ADC_CTRL, 0x30);
 	if (ret < 0)
 		return ret;

 	if (tmp >= 2400) {
 		data = NAU7802_CTRL1_VLDO((4500 - tmp) / 300);
 		ret = i2c_smbus_write_byte_data(st->client, NAU7802_REG_CTRL1,
 						data);
 		if (ret < 0)
 			return ret;
 	}

 	/* Populate available ADC input ranges */
 	for (i = 0; i < ARRAY_SIZE(st->scale_avail); i++)
 		st->scale_avail[i] = (((u64)st->vref_mv) * 1000000000ULL)
 					   >> (23 + i);

 	init_completion(&st->value_ok);

 	/*
 	 * The ADC fires continuously and we can't do anything about
 	 * it. So we need to have the IRQ disabled by default, and we
 	 * will enable them back when we will need them..
 	 */
 	if (client->irq) {
 		ret = request_threaded_irq(client->irq,
 				NULL,
 				nau7802_eoc_trigger,
 				IRQF_TRIGGER_HIGH | IRQF_ONESHOT,
 				client->dev.driver->name,
 				indio_dev);
 		if (ret) {
 			/*
 			 * What may happen here is that our IRQ controller is
 			 * not able to get level interrupt but this is required
 			 * by this ADC as when going over 40 sample per second,
 			 * the interrupt line may stay high between conversions.
 			 * So, we continue no matter what but we switch to
 			 * polling mode.
 			 */
 			dev_info(&client->dev,
 				"Failed to allocate IRQ, using polling mode\n");
 			client->irq = 0;
 		} else
 			disable_irq(client->irq);
 	}

 	if (!client->irq) {
 		/*
 		 * We are polling, use the fastest sample rate by
 		 * default
 		 */
 		st->sample_rate = NAU7802_SAMP_FREQ_320;
 		ret = i2c_smbus_write_byte_data(st->client, NAU7802_REG_CTRL2,
 					  NAU7802_CTRL2_CRS(st->sample_rate));
 		if (ret)
 			goto error_free_irq;
 	}

 	/* Setup the ADC channels available on the board */
 	indio_dev->num_channels = ARRAY_SIZE(nau7802_chan_array);
 	indio_dev->channels = nau7802_chan_array;

 	mutex_init(&st->lock);
 	mutex_init(&st->data_lock);

 	ret = iio_device_register(indio_dev);
 	if (ret < 0) {
 		dev_err(&client->dev, "Couldn't register the device.\n");
 		goto error_device_register;
 	}

 	return 0;

 error_device_register:
 	mutex_destroy(&st->lock);
 	mutex_destroy(&st->data_lock);
 error_free_irq:
 	if (client->irq)
 		free_irq(client->irq, indio_dev);

 	return ret;
 }

 static int nau7802_remove(struct i2c_client *client)
 {
 	struct iio_dev *indio_dev = i2c_get_clientdata(client);
 	struct nau7802_state *st = iio_priv(indio_dev);

 	iio_device_unregister(indio_dev);
 	mutex_destroy(&st->lock);
 	mutex_destroy(&st->data_lock);
 	if (client->irq)
 		free_irq(client->irq, indio_dev);

 	return 0;
 }

 static const struct i2c_device_id nau7802_i2c_id[] = {
 	{ "nau7802", 0 },
 	{ }
 };
 MODULE_DEVICE_TABLE(i2c, nau7802_i2c_id);

 static const struct of_device_id nau7802_dt_ids[] = {
 	{ .compatible = "nuvoton,nau7802" },
 	{},
 };
 MODULE_DEVICE_TABLE(of, nau7802_dt_ids);

 static struct i2c_driver nau7802_driver = {
 	.probe = nau7802_probe,
 	.remove = nau7802_remove,
 	.id_table = nau7802_i2c_id,
 	.driver = {
 		   .name = "nau7802",
 		   .of_match_table = of_match_ptr(nau7802_dt_ids),
 	},
 };

 module_i2c_driver(nau7802_driver);

 MODULE_LICENSE("GPL");
 MODULE_DESCRIPTION("Nuvoton NAU7802 ADC Driver");
 MODULE_AUTHOR("Maxime Ripard <maxime.ripard@free-electrons.com>");
 MODULE_AUTHOR("Alexandre Belloni <alexandre.belloni@free-electrons.com>");
	/*
	* Driver for the Nuvoton NAU7802 ADC
	*
	* Copyright 2013 Free Electrons
	*
	* Licensed under the GPLv2 or later.
	*/

	#include <linux/delay.h>
	#include <linux/i2c.h>
	#include <linux/interrupt.h>
	#include <linux/module.h>
	#include <linux/wait.h>
	#include <linux/log2.h>

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

	#define NAU7802_REG_PUCTRL 0x00
	#define NAU7802_PUCTRL_RR(x) (x << 0)
	#define NAU7802_PUCTRL_RR_BIT NAU7802_PUCTRL_RR(1)
	#define NAU7802_PUCTRL_PUD(x) (x << 1)
	#define NAU7802_PUCTRL_PUD_BIT NAU7802_PUCTRL_PUD(1)
	#define NAU7802_PUCTRL_PUA(x) (x << 2)
	#define NAU7802_PUCTRL_PUA_BIT NAU7802_PUCTRL_PUA(1)
	#define NAU7802_PUCTRL_PUR(x) (x << 3)
	#define NAU7802_PUCTRL_PUR_BIT NAU7802_PUCTRL_PUR(1)
	#define NAU7802_PUCTRL_CS(x) (x << 4)
	#define NAU7802_PUCTRL_CS_BIT NAU7802_PUCTRL_CS(1)
	#define NAU7802_PUCTRL_CR(x) (x << 5)
	#define NAU7802_PUCTRL_CR_BIT NAU7802_PUCTRL_CR(1)
	#define NAU7802_PUCTRL_AVDDS(x) (x << 7)
	#define NAU7802_PUCTRL_AVDDS_BIT NAU7802_PUCTRL_AVDDS(1)
	#define NAU7802_REG_CTRL1 0x01
	#define NAU7802_CTRL1_VLDO(x) (x << 3)
	#define NAU7802_CTRL1_GAINS(x) (x)
	#define NAU7802_CTRL1_GAINS_BITS 0x07
	#define NAU7802_REG_CTRL2 0x02
	#define NAU7802_CTRL2_CHS(x) (x << 7)
	#define NAU7802_CTRL2_CRS(x) (x << 4)
	#define NAU7802_SAMP_FREQ_320 0x07
	#define NAU7802_CTRL2_CHS_BIT NAU7802_CTRL2_CHS(1)
	#define NAU7802_REG_ADC_B2 0x12
	#define NAU7802_REG_ADC_B1 0x13
	#define NAU7802_REG_ADC_B0 0x14
	#define NAU7802_REG_ADC_CTRL 0x15

	#define NAU7802_MIN_CONVERSIONS 6

	struct nau7802_state {
	struct i2c_client *client;
	s32 last_value;
	struct mutex lock;
	struct mutex data_lock;
	u32 vref_mv;
	u32 conversion_count;
	u32 min_conversions;
	u8 sample_rate;
	u32 scale_avail[8];
	struct completion value_ok;
	};

	#define NAU7802_CHANNEL(chan) { \
	.type = IIO_VOLTAGE, \
	.indexed = 1, \
	.channel = (chan), \
	.scan_index = (chan), \
	.info_mask_separate = BIT(IIO_CHAN_INFO_RAW), \
	.info_mask_shared_by_type = BIT(IIO_CHAN_INFO_SCALE) \| \
	BIT(IIO_CHAN_INFO_SAMP_FREQ) \
	}

	static const struct iio_chan_spec nau7802_chan_array[] = {
	NAU7802_CHANNEL(0),
	NAU7802_CHANNEL(1),
	};

	static const u16 nau7802_sample_freq_avail[] = {10, 20, 40, 80,
	10, 10, 10, 320};

	static IIO_CONST_ATTR_SAMP_FREQ_AVAIL("10 40 80 320");

	static struct attribute *nau7802_attributes[] = {
	&iio_const_attr_sampling_frequency_available.dev_attr.attr,
	NULL
	};

	static const struct attribute_group nau7802_attribute_group = {
	.attrs = nau7802_attributes,
	};

	static int nau7802_set_gain(struct nau7802_state *st, int gain)
	{
	int ret;

	mutex_lock(&st->lock);
	st->conversion_count = 0;

	ret = i2c_smbus_read_byte_data(st->client, NAU7802_REG_CTRL1);
	if (ret < 0)
	goto nau7802_sysfs_set_gain_out;
	ret = i2c_smbus_write_byte_data(st->client, NAU7802_REG_CTRL1,
	(ret & (~NAU7802_CTRL1_GAINS_BITS)) \|
	gain);

	nau7802_sysfs_set_gain_out:
	mutex_unlock(&st->lock);

	return ret;
	}

	static int nau7802_read_conversion(struct nau7802_state *st)
	{
	int data;

	mutex_lock(&st->data_lock);
	data = i2c_smbus_read_byte_data(st->client, NAU7802_REG_ADC_B2);
	if (data < 0)
	goto nau7802_read_conversion_out;
	st->last_value = data << 16;

	data = i2c_smbus_read_byte_data(st->client, NAU7802_REG_ADC_B1);
	if (data < 0)
	goto nau7802_read_conversion_out;
	st->last_value \|= data << 8;

	data = i2c_smbus_read_byte_data(st->client, NAU7802_REG_ADC_B0);
	if (data < 0)
	goto nau7802_read_conversion_out;
	st->last_value \|= data;

	st->last_value = sign_extend32(st->last_value, 23);

	nau7802_read_conversion_out:
	mutex_unlock(&st->data_lock);

	return data;
	}

	/*
	* Conversions are synchronised on the rising edge of NAU7802_PUCTRL_CS_BIT
	*/
	static int nau7802_sync(struct nau7802_state *st)
	{
	int ret;

	ret = i2c_smbus_read_byte_data(st->client, NAU7802_REG_PUCTRL);
	if (ret < 0)
	return ret;
	ret = i2c_smbus_write_byte_data(st->client, NAU7802_REG_PUCTRL,
	ret \| NAU7802_PUCTRL_CS_BIT);

	return ret;
	}

	static irqreturn_t nau7802_eoc_trigger(int irq, void *private)
	{
	struct iio_dev *indio_dev = private;
	struct nau7802_state *st = iio_priv(indio_dev);
	int status;

	status = i2c_smbus_read_byte_data(st->client, NAU7802_REG_PUCTRL);
	if (status < 0)
	return IRQ_HANDLED;

	if (!(status & NAU7802_PUCTRL_CR_BIT))
	return IRQ_NONE;

	if (nau7802_read_conversion(st) < 0)
	return IRQ_HANDLED;

	/*
	* Because there is actually only one ADC for both channels, we have to
	* wait for enough conversions to happen before getting a significant
	* value when changing channels and the values are far apart.
	*/
	if (st->conversion_count < NAU7802_MIN_CONVERSIONS)
	st->conversion_count++;
	if (st->conversion_count >= NAU7802_MIN_CONVERSIONS)
	complete_all(&st->value_ok);

	return IRQ_HANDLED;
	}

	static int nau7802_read_irq(struct iio_dev *indio_dev,
	struct iio_chan_spec const *chan,
	int *val)
	{
	struct nau7802_state *st = iio_priv(indio_dev);
	int ret;

	INIT_COMPLETION(st->value_ok);
	enable_irq(st->client->irq);

	nau7802_sync(st);

	/* read registers to ensure we flush everything */
	ret = nau7802_read_conversion(st);
	if (ret < 0)
	goto read_chan_info_failure;

	/* Wait for a conversion to finish */
	ret = wait_for_completion_interruptible_timeout(&st->value_ok,
	msecs_to_jiffies(1000));
	if (ret == 0)
	ret = -ETIMEDOUT;

	if (ret < 0)
	goto read_chan_info_failure;

	disable_irq(st->client->irq);

	*val = st->last_value;

	return IIO_VAL_INT;

	read_chan_info_failure:
	disable_irq(st->client->irq);

	return ret;
	}

	static int nau7802_read_poll(struct iio_dev *indio_dev,
	struct iio_chan_spec const *chan,
	int *val)
	{
	struct nau7802_state *st = iio_priv(indio_dev);
	int ret;

	nau7802_sync(st);

	/* read registers to ensure we flush everything */
	ret = nau7802_read_conversion(st);
	if (ret < 0)
	return ret;

	/*
	* Because there is actually only one ADC for both channels, we have to
	* wait for enough conversions to happen before getting a significant
	* value when changing channels and the values are far appart.
	*/
	do {
	ret = i2c_smbus_read_byte_data(st->client, NAU7802_REG_PUCTRL);
	if (ret < 0)
	return ret;

	while (!(ret & NAU7802_PUCTRL_CR_BIT)) {
	if (st->sample_rate != NAU7802_SAMP_FREQ_320)
	msleep(20);
	else
	mdelay(4);
	ret = i2c_smbus_read_byte_data(st->client,
	NAU7802_REG_PUCTRL);
	if (ret < 0)
	return ret;
	}

	ret = nau7802_read_conversion(st);
	if (ret < 0)
	return ret;
	if (st->conversion_count < NAU7802_MIN_CONVERSIONS)
	st->conversion_count++;
	} while (st->conversion_count < NAU7802_MIN_CONVERSIONS);

	*val = st->last_value;

	return IIO_VAL_INT;
	}

	static int nau7802_read_raw(struct iio_dev *indio_dev,
	struct iio_chan_spec const *chan,
	int val, int val2, long mask)
	{
	struct nau7802_state *st = iio_priv(indio_dev);
	int ret;

	switch (mask) {
	case IIO_CHAN_INFO_RAW:
	mutex_lock(&st->lock);
	/*
	* Select the channel to use
	* - Channel 1 is value 0 in the CHS register
	* - Channel 2 is value 1 in the CHS register
	*/
	ret = i2c_smbus_read_byte_data(st->client, NAU7802_REG_CTRL2);
	if (ret < 0) {
	mutex_unlock(&st->lock);
	return ret;
	}

	if (((ret & NAU7802_CTRL2_CHS_BIT) && !chan->channel) \|\|
	(!(ret & NAU7802_CTRL2_CHS_BIT) &&
	chan->channel)) {
	st->conversion_count = 0;
	ret = i2c_smbus_write_byte_data(st->client,
	NAU7802_REG_CTRL2,
	NAU7802_CTRL2_CHS(chan->channel) \|
	NAU7802_CTRL2_CRS(st->sample_rate));

	if (ret < 0) {
	mutex_unlock(&st->lock);
	return ret;
	}
	}

	if (st->client->irq)
	ret = nau7802_read_irq(indio_dev, chan, val);
	else
	ret = nau7802_read_poll(indio_dev, chan, val);

	mutex_unlock(&st->lock);
	return ret;

	case IIO_CHAN_INFO_SCALE:
	ret = i2c_smbus_read_byte_data(st->client, NAU7802_REG_CTRL1);
	if (ret < 0)
	return ret;

	/*
	* We have 24 bits of signed data, that means 23 bits of data
	* plus the sign bit
	*/
	*val = st->vref_mv;
	*val2 = 23 + (ret & NAU7802_CTRL1_GAINS_BITS);

	return IIO_VAL_FRACTIONAL_LOG2;

	case IIO_CHAN_INFO_SAMP_FREQ:
	*val = nau7802_sample_freq_avail[st->sample_rate];
	*val2 = 0;
	return IIO_VAL_INT;

	default:
	break;
	}

	return -EINVAL;
	}

	static int nau7802_write_raw(struct iio_dev *indio_dev,
	struct iio_chan_spec const *chan,
	int val, int val2, long mask)
	{
	struct nau7802_state *st = iio_priv(indio_dev);
	int i, ret;

	switch (mask) {
	case IIO_CHAN_INFO_SCALE:
	for (i = 0; i < ARRAY_SIZE(st->scale_avail); i++)
	if (val2 == st->scale_avail[i])
	return nau7802_set_gain(st, i);

	break;

	case IIO_CHAN_INFO_SAMP_FREQ:
	for (i = 0; i < ARRAY_SIZE(nau7802_sample_freq_avail); i++)
	if (val == nau7802_sample_freq_avail[i]) {
	mutex_lock(&st->lock);
	st->sample_rate = i;
	st->conversion_count = 0;
	ret = i2c_smbus_write_byte_data(st->client,
	NAU7802_REG_CTRL2,
	NAU7802_CTRL2_CRS(st->sample_rate));
	mutex_unlock(&st->lock);
	return ret;
	}

	break;

	default:
	break;
	}

	return -EINVAL;
	}

	static int nau7802_write_raw_get_fmt(struct iio_dev *indio_dev,
	struct iio_chan_spec const *chan,
	long mask)
	{
	return IIO_VAL_INT_PLUS_NANO;
	}

	static const struct iio_info nau7802_info = {
	.driver_module = THIS_MODULE,
	.read_raw = &nau7802_read_raw,
	.write_raw = &nau7802_write_raw,
	.write_raw_get_fmt = nau7802_write_raw_get_fmt,
	.attrs = &nau7802_attribute_group,
	};

	static int nau7802_probe(struct i2c_client *client,
	const struct i2c_device_id *id)
	{
	struct iio_dev *indio_dev;
	struct nau7802_state *st;
	struct device_node *np = client->dev.of_node;
	int i, ret;
	u8 data;
	u32 tmp = 0;

	if (!client->dev.of_node) {
	dev_err(&client->dev, "No device tree node available.\n");
	return -EINVAL;
	}

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

	st = iio_priv(indio_dev);

	i2c_set_clientdata(client, indio_dev);

	indio_dev->dev.parent = &client->dev;
	indio_dev->name = dev_name(&client->dev);
	indio_dev->modes = INDIO_DIRECT_MODE;
	indio_dev->info = &nau7802_info;

	st->client = client;

	/* Reset the device */
	ret = i2c_smbus_write_byte_data(st->client, NAU7802_REG_PUCTRL,
	NAU7802_PUCTRL_RR_BIT);
	if (ret < 0)
	return ret;

	/* Enter normal operation mode */
	ret = i2c_smbus_write_byte_data(st->client, NAU7802_REG_PUCTRL,
	NAU7802_PUCTRL_PUD_BIT);
	if (ret < 0)
	return ret;

	/*
	* After about 200 usecs, the device should be ready and then
	* the Power Up bit will be set to 1. If not, wait for it.
	*/
	udelay(210);
	ret = i2c_smbus_read_byte_data(st->client, NAU7802_REG_PUCTRL);
	if (ret < 0)
	return ret;
	if (!(ret & NAU7802_PUCTRL_PUR_BIT))
	return ret;

	of_property_read_u32(np, "nuvoton,vldo", &tmp);
	st->vref_mv = tmp;

	data = NAU7802_PUCTRL_PUD_BIT \| NAU7802_PUCTRL_PUA_BIT \|
	NAU7802_PUCTRL_CS_BIT;
	if (tmp >= 2400)
	data \|= NAU7802_PUCTRL_AVDDS_BIT;

	ret = i2c_smbus_write_byte_data(st->client, NAU7802_REG_PUCTRL, data);
	if (ret < 0)
	return ret;
	ret = i2c_smbus_write_byte_data(st->client, NAU7802_REG_ADC_CTRL, 0x30);
	if (ret < 0)
	return ret;

	if (tmp >= 2400) {
	data = NAU7802_CTRL1_VLDO((4500 - tmp) / 300);
	ret = i2c_smbus_write_byte_data(st->client, NAU7802_REG_CTRL1,
	data);
	if (ret < 0)
	return ret;
	}

	/* Populate available ADC input ranges */
	for (i = 0; i < ARRAY_SIZE(st->scale_avail); i++)
	st->scale_avail[i] = (((u64)st->vref_mv) * 1000000000ULL)
	>> (23 + i);

	init_completion(&st->value_ok);

	/*
	* The ADC fires continuously and we can't do anything about
	* it. So we need to have the IRQ disabled by default, and we
	* will enable them back when we will need them..
	*/
	if (client->irq) {
	ret = request_threaded_irq(client->irq,
	NULL,
	nau7802_eoc_trigger,
	IRQF_TRIGGER_HIGH \| IRQF_ONESHOT,
	client->dev.driver->name,
	indio_dev);
	if (ret) {
	/*
	* What may happen here is that our IRQ controller is
	* not able to get level interrupt but this is required
	* by this ADC as when going over 40 sample per second,
	* the interrupt line may stay high between conversions.
	* So, we continue no matter what but we switch to
	* polling mode.
	*/
	dev_info(&client->dev,
	"Failed to allocate IRQ, using polling mode\n");
	client->irq = 0;
	} else
	disable_irq(client->irq);
	}

	if (!client->irq) {
	/*
	* We are polling, use the fastest sample rate by
	* default
	*/
	st->sample_rate = NAU7802_SAMP_FREQ_320;
	ret = i2c_smbus_write_byte_data(st->client, NAU7802_REG_CTRL2,
	NAU7802_CTRL2_CRS(st->sample_rate));
	if (ret)
	goto error_free_irq;
	}

	/* Setup the ADC channels available on the board */
	indio_dev->num_channels = ARRAY_SIZE(nau7802_chan_array);
	indio_dev->channels = nau7802_chan_array;

	mutex_init(&st->lock);
	mutex_init(&st->data_lock);

	ret = iio_device_register(indio_dev);
	if (ret < 0) {
	dev_err(&client->dev, "Couldn't register the device.\n");
	goto error_device_register;
	}

	return 0;

	error_device_register:
	mutex_destroy(&st->lock);
	mutex_destroy(&st->data_lock);
	error_free_irq:
	if (client->irq)
	free_irq(client->irq, indio_dev);

	return ret;
	}

	static int nau7802_remove(struct i2c_client *client)
	{
	struct iio_dev *indio_dev = i2c_get_clientdata(client);
	struct nau7802_state *st = iio_priv(indio_dev);

	iio_device_unregister(indio_dev);
	mutex_destroy(&st->lock);
	mutex_destroy(&st->data_lock);
	if (client->irq)
	free_irq(client->irq, indio_dev);

	return 0;
	}

	static const struct i2c_device_id nau7802_i2c_id[] = {
	{ "nau7802", 0 },
	{ }
	};
	MODULE_DEVICE_TABLE(i2c, nau7802_i2c_id);

	static const struct of_device_id nau7802_dt_ids[] = {
	{ .compatible = "nuvoton,nau7802" },
	{},
	};
	MODULE_DEVICE_TABLE(of, nau7802_dt_ids);

	static struct i2c_driver nau7802_driver = {
	.probe = nau7802_probe,
	.remove = nau7802_remove,
	.id_table = nau7802_i2c_id,
	.driver = {
	.name = "nau7802",
	.of_match_table = of_match_ptr(nau7802_dt_ids),
	},
	};

	module_i2c_driver(nau7802_driver);

	MODULE_LICENSE("GPL");
	MODULE_DESCRIPTION("Nuvoton NAU7802 ADC Driver");
	MODULE_AUTHOR("Maxime Ripard <maxime.ripard@free-electrons.com>");
	MODULE_AUTHOR("Alexandre Belloni <alexandre.belloni@free-electrons.com>");