iio: Add Nuvoton NAU7802 ADC driver

The Nuvoton NAU7802 ADC is a 24-bit 2-channels I2C ADC, with adjustable
gain and sampling rates.
Signed-off-by: NAlexandre Belloni <alexandre.belloni@free-electrons.com>
Signed-off-by: NMaxime Ripard <maxime.ripard@free-electrons.com>
Reviewed-by: NLars-Peter Clausen <lars@metafoo.de>
Signed-off-by: NJonathan Cameron <jic23@kernel.org>

Documentation/devicetree/bindings/iio/adc/nuvoton-nau7802.txt

+* Nuvoton NAU7802 Analog to Digital Converter (ADC)
+
+Required properties:
+  - compatible: Should be "nuvoton,nau7802"
+  - reg: Should contain the ADC I2C address
+
+Optional properties:
+  - nuvoton,vldo: Internal reference voltage in millivolts to be
+    configured valid values are between 2400 mV and 4500 mV.
+  - interrupts: IRQ line for the ADC. If not used the driver will use
+    polling.
+
+Example:
+adc2: nau7802@2a {
+	compatible = "nuvoton,nau7802";
+	reg = <0x2a>;
+	nuvoton,vldo = <3000>;
+};

drivers/iio/adc/Kconfig

@@ -143,6 +143,15 @@ config MCP320X
 	  This driver can also be built as a module. If so, the module will be
 	  called mcp320x.
 
+config NAU7802
+	tristate "Nuvoton NAU7802 ADC driver"
+	depends on I2C
+	help
+	  Say yes here to build support for Nuvoton NAU7802 ADC.
+
+	  To compile this driver as a module, choose M here: the
+	  module will be called nau7802.
+
 config TI_ADC081C
 	tristate "Texas Instruments ADC081C021/027"
 	depends on I2C

drivers/iio/adc/Makefile

@@ -15,6 +15,7 @@ obj-$(CONFIG_EXYNOS_ADC) += exynos_adc.o
 obj-$(CONFIG_LP8788_ADC) += lp8788_adc.o
 obj-$(CONFIG_MAX1363) += max1363.o
 obj-$(CONFIG_MCP320X) += mcp320x.o
+obj-$(CONFIG_NAU7802) += nau7802.o
 obj-$(CONFIG_TI_ADC081C) += ti-adc081c.o
 obj-$(CONFIG_TI_AM335X_ADC) += ti_am335x_adc.o
 obj-$(CONFIG_VIPERBOARD_ADC) += viperboard_adc.o

drivers/iio/adc/nau7802.c

+/*
+ * 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 = iio_device_alloc(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)
+		goto error_free_indio;
+
+	/* Enter normal operation mode */
+	ret = i2c_smbus_write_byte_data(st->client, NAU7802_REG_PUCTRL,
+				  NAU7802_PUCTRL_PUD_BIT);
+	if (ret < 0)
+		goto error_free_indio;
+
+	/*
+	 * 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)
+		goto error_free_indio;
+	if (!(ret & NAU7802_PUCTRL_PUR_BIT))
+		goto error_free_indio;
+
+	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)
+		goto error_free_indio;
+	ret = i2c_smbus_write_byte_data(st->client, NAU7802_REG_ADC_CTRL, 0x30);
+	if (ret < 0)
+		goto error_free_indio;
+
+	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)
+			goto error_free_indio;
+	}
+
+	/* 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);
+error_free_indio:
+	iio_device_free(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);
+	iio_device_free(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>");