Add Microchip MCP3422/3/4 high resolution ADC

I think this patch is more or less in it's final shape, please review it.

---
 drivers/iio/adc/Kconfig   |   10 ++
 drivers/iio/adc/Makefile  |    1 +
 drivers/iio/adc/mcp3422.c |  432 +++++++++++++++++++++++++++++++++++++++++++++
 3 files changed, 443 insertions(+)
 create mode 100644 drivers/iio/adc/mcp3422.c

drivers/iio/adc/Kconfig +10 -0

index f725b45..e9879e6 100644
@@ -145,6 +145,16 @@ config MCP320X
 	  This driver can also be built as a module. If so, the module will be
 	  called mcp320x.
 
+config MCP3422
+	tristate "Microchip Technology MCP3422/3/4 driver"
+	depends on I2C
+	help
+	  Say yes here to build support for Microchip Technology's MCP3422,
+	  MCP3423 or MCP3424 analog to digital converters.
+
+	  This driver can also be built as a module. If so, the module will be
+	  called mcp3422.
+
 config NAU7802
 	tristate "Nuvoton NAU7802 ADC driver"
 	depends on I2C

drivers/iio/adc/Makefile +1 -0

index 2a4324e..9772e3b 100644
@@ -16,6 +16,7 @@ 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-$(CONFIG_MCP3422) += mcp3422.o
 obj-$(CONFIG_NAU7802) += nau7802.o
 obj-$(CONFIG_TI_ADC081C) += ti-adc081c.o
 obj-$(CONFIG_TI_AM335X_ADC) += ti_am335x_adc.o

drivers/iio/adc/mcp3422.c new file +212 -0

new file mode 100644
index 0000000..eda5d39
@@ -0,0 +1,432 @@
+/*
+ * mcp3422.c - driver for the Microchip mcp3422/3/4 chip family
+ *
+ * Copyright (C) 2013, Angelo Compagnucci
+ * Author: Angelo Compagnucci <[email protected]>
+ *
+ * Datasheet: http://ww1.microchip.com/downloads/en/devicedoc/22088b.pdf
+ *
+ * This driver exports the value of analog input voltage to sysfs, the
+ * voltage unit is nV.
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ */
+
+#include <linux/err.h>
+#include <linux/i2c.h>
+#include <linux/module.h>
+#include <linux/delay.h>
+#include <linux/sysfs.h>
+#include <linux/string.h>
+
+#include <linux/iio/iio.h>
+#include <linux/iio/sysfs.h>
+
+/* Masks */
+#define MCP3422_CHANNEL_MASK	0x60
+#define MCP3422_PGA_MASK	0x03
+#define MCP3422_SRATE_MASK	0x0C
+#define MCP3422_SRATE_240	0x0
+#define MCP3422_SRATE_60	0x1
+#define MCP3422_SRATE_15	0x2
+#define MCP3422_SRATE_3	0x3
+#define MCP3422_PGA_1	0
+#define MCP3422_PGA_2	1
+#define MCP3422_PGA_4	2
+#define MCP3422_PGA_8	3
+#define MCP3422_CONT_SAMPLING	0x10
+
+#define MCP3422_CHANNEL(config)	((((config) & MCP3422_CHANNEL_MASK) >> 5) + 1)
+#define MCP3422_PGA(config)	((config) & MCP3422_PGA_MASK)
+#define MCP3422_SAMPLE_RATE(config)	(((config) & MCP3422_SRATE_MASK) >> 2)
+
+#define MCP3422_CHANNEL_VALUE(value) (((value - 1) << 5) & MCP3422_CHANNEL_MASK)
+#define MCP3422_PGA_VALUE(value) ((value) & MCP3422_PGA_MASK)
+#define MCP3422_SAMPLE_RATE_VALUE(value) ((value << 2) & MCP3422_SRATE_MASK)
+
+#define MCP3422_CHAN(index) \
+	{ \
+		.type = IIO_VOLTAGE, \
+		.indexed = 1, \
+		.channel = index, \
+		.info_mask_separate = BIT(IIO_CHAN_INFO_RAW) \
+				| BIT(IIO_CHAN_INFO_SCALE), \
+	}
+
+/* LSB is in nV to eliminate floating point */
+static const u32 rates_to_lsb[] = {1000000, 250000, 62500, 15625};
+
+/* Client data (each client gets its own) */
+struct mcp3422 {
+	struct i2c_client *i2c;
+	u8 config;
+	u8 pga[4];
+	struct mutex lock;
+};
+
+static int mcp3422_update_config(struct mcp3422 *adc, u8 newconfig)
+{
+	int ret;
+
+	mutex_lock(&adc->lock);
+
+	ret = i2c_master_send(adc->i2c, &newconfig, 1);
+	if (ret > 0)
+		adc->config = newconfig;
+
+	mutex_unlock(&adc->lock);
+
+	return ret;
+}
+
+static int mcp3422_read(struct mcp3422 *adc, int *value, u8 *config)
+{
+	int ret = 0;
+	u8 sample_rate = MCP3422_SAMPLE_RATE(adc->config);
+	u8 buf[4] = {0, 0, 0, 0};
+	u32 temp;
+
+	if (sample_rate == MCP3422_SRATE_3) {
+		ret = i2c_master_recv(adc->i2c, buf, 4);
+		temp = buf[0] << 16 | buf[1] << 8 | buf[2];
+		*config = buf[3];
+	} else {
+		ret = i2c_master_recv(adc->i2c, buf, 3);
+		temp = buf[0] << 8 | buf[1];
+		*config = buf[2];
+	}
+
+	switch (sample_rate) {
+	case MCP3422_SRATE_240:
+		*value = sign_extend32(temp, 12);
+		break;
+	case MCP3422_SRATE_60:
+		*value = sign_extend32(temp, 14);
+		break;
+	case MCP3422_SRATE_15:
+		*value = sign_extend32(temp, 16);
+		break;
+	case MCP3422_SRATE_3:
+		*value = sign_extend32(temp, 18);
+		break;
+	}
+
+	return ret;
+}
+
+static int mcp3422_read_channel(struct mcp3422 *adc,
+				struct iio_chan_spec const *channel, int *value)
+{
+	int mtime = 0;
+	u8 config = 0;
+	u8 req_channel = channel->channel;
+
+	if (req_channel != MCP3422_CHANNEL(adc->config)) {
+		config = adc->config;
+		config &= ~MCP3422_CHANNEL_MASK;
+		config |= MCP3422_CHANNEL_VALUE(req_channel);
+		config &= ~MCP3422_PGA_MASK;
+		config |= MCP3422_PGA_VALUE(adc->pga[req_channel-1]);
+		mcp3422_update_config(adc, config);
+		switch (MCP3422_SAMPLE_RATE(config)) {
+		case MCP3422_SRATE_240:
+			mtime = 1000 / 240;
+			break;
+		case MCP3422_SRATE_60:
+			mtime = 1000 / 60;
+			break;
+		case MCP3422_SRATE_15:
+			mtime = 1000 / 15;
+			break;
+		case MCP3422_SRATE_3:
+			mtime = 1000 / 3;
+			break;
+		}
+		msleep(mtime);
+	}
+
+	return mcp3422_read(adc, value, &config);
+}
+
+static int mcp3422_read_raw(struct iio_dev *iio,
+			struct iio_chan_spec const *channel, int *val1,
+			int *val2, long mask)
+{
+	struct mcp3422 *adc = iio_priv(iio);
+	int err, temp = 0;
+
+	u8 sample_rate = MCP3422_SAMPLE_RATE(adc->config);
+	u8 pga		 = MCP3422_PGA(adc->config);
+
+	err = mcp3422_read_channel(adc, channel, &temp);
+	if (err < 0)
+		return err;
+
+	switch (mask) {
+	case IIO_CHAN_INFO_RAW:
+		*val1 = temp;
+
+		return IIO_VAL_INT;
+
+	case IIO_CHAN_INFO_SCALE:
+
+		temp = (temp * rates_to_lsb[sample_rate])
+			/ (pga ? 1 << pga : 1);
+
+		*val1 = temp / 1000000000;
+		*val2 = temp % 1000000000;
+
+		return IIO_VAL_INT_PLUS_NANO;
+
+	default:
+		break;
+	}
+
+	return -EINVAL;
+}
+
+static int mcp3422_write_raw(struct iio_dev *iio,
+			struct iio_chan_spec const *channel, int val1,
+			int val2, long mask)
+{
+	struct mcp3422 *adc = iio_priv(iio);
+	u8 pga, config;
+	u8 req_channel = channel->channel;
+
+	switch (mask) {
+	case IIO_CHAN_INFO_SCALE:
+		switch (val1) {
+		case 1:
+			pga = MCP3422_PGA_1;
+			break;
+		case 2:
+			pga = MCP3422_PGA_2;
+			break;
+		case 4:
+			pga = MCP3422_PGA_4;
+			break;
+		case 8:
+			pga = MCP3422_PGA_8;

drivers/iio/adc/mcp3422.c new file +12 -0

+
+		config &= ~MCP3422_CHANNEL_MASK;
+		config |= MCP3422_CHANNEL_VALUE(req_channel);
+		config &= ~MCP3422_PGA_MASK;
+		config |= MCP3422_PGA_VALUE(adc->pga[req_channel-1]);
+		mcp3422_update_config(adc, config);
+		return 0;
+	default:
+		break;
+	}
+
+	return -EINVAL;

drivers/iio/adc/mcp3422.c new file +51 -0

+	u8 config = adc->config;
+
+	if (kstrtou8(buf, 10, &value) < 0)
+		return -EINVAL;
+
+	switch (value) {
+	case 240:
+		value = MCP3422_SRATE_240;
+		break;
+	case 60:
+		value = MCP3422_SRATE_60;
+		break;
+	case 15:
+		value = MCP3422_SRATE_15;
+		break;
+	case 3:
+		value = MCP3422_SRATE_3;
+		break;
+	default:
+		return -EINVAL;
+	}
+
+	config &= ~MCP3422_SRATE_MASK;
+	config |= MCP3422_SAMPLE_RATE_VALUE(value);
+
+	mcp3422_update_config(adc, config);
+
+	return count;
+}
+
+static ssize_t mcp3422_get_sample_rate(struct device *dev,
+		struct device_attribute *attr,
+		char *buf)
+{
+	struct i2c_client *client = to_i2c_client(dev);
+	struct iio_dev *iio = i2c_get_clientdata(client);
+	struct mcp3422 *adc = iio_priv(iio);
+	u8 value = 0;
+
+	switch (MCP3422_SAMPLE_RATE(adc->config)) {
+	case MCP3422_SRATE_240:
+		value = 240;
+		break;
+	case MCP3422_SRATE_60:
+		value = 60;
+		break;
+	case MCP3422_SRATE_15:
+		value = 15;
+		break;
+	case MCP3422_SRATE_3:
+		value = 3;

drivers/iio/adc/mcp3422.c new file +5 -0

+static IIO_CONST_ATTR(scale_available, "1 2 4 8");
+
+static struct attribute *mcp3422_attributes[] = {
+	&iio_dev_attr_sampling_frequency.dev_attr.attr,
+	&iio_const_attr_sampling_frequency_available.dev_attr.attr,

drivers/iio/adc/mcp3422.c new file +25 -0

+	MCP3422_CHAN(2),
+};
+
+static const struct iio_chan_spec mcp3424_channels[] = {
+	MCP3422_CHAN(1),
+	MCP3422_CHAN(2),
+	MCP3422_CHAN(3),
+	MCP3422_CHAN(4),
+};
+
+static const struct iio_info mcp3422_info = {
+	.read_raw = mcp3422_read_raw,
+	.write_raw = mcp3422_write_raw,
+	.attrs = &mcp3422_attribute_group,
+	.driver_module = THIS_MODULE,
+};
+
+static int mcp3422_probe(struct i2c_client *client,
+			 const struct i2c_device_id *id)
+{
+	struct iio_dev *indio_dev;
+	struct mcp3422 *adc;
+	int err;
+	u8 config;
+

drivers/iio/adc/mcp3422.c new file +22 -0

+
+	mutex_init(&adc->lock);
+
+	indio_dev->dev.parent = &client->dev;
+	indio_dev->name = dev_name(&client->dev);
+	indio_dev->modes = INDIO_DIRECT_MODE;
+	indio_dev->info = &mcp3422_info;
+
+	switch ((unsigned int)(id->driver_data)) {
+	case 2:
+	case 3:
+		indio_dev->channels = mcp3422_channels;
+		indio_dev->num_channels = ARRAY_SIZE(mcp3422_channels);
+		break;
+	case 4:
+		indio_dev->channels = mcp3424_channels;
+		indio_dev->num_channels = ARRAY_SIZE(mcp3424_channels);
+		break;
+	}
+
+	err = iio_device_register(indio_dev);
+	if (err < 0)

drivers/iio/adc/mcp3422.c new file +45 -0

+
+	return 0;
+}
+
+static int mcp3422_remove(struct i2c_client *client)
+{
+	struct iio_dev *iio = i2c_get_clientdata(client);
+
+	iio_device_unregister(iio);
+	iio_device_free(iio);
+
+	return 0;
+}
+
+static const struct i2c_device_id mcp3422_id[] = {
+	{ "mcp3422", 2 },
+	{ "mcp3423", 3 },
+	{ "mcp3424", 4 },
+	{ }
+};
+MODULE_DEVICE_TABLE(i2c, mcp3422_id);
+
+#ifdef CONFIG_OF
+static const struct of_device_id mcp3422_of_match[] = {
+	{ .compatible = "mcp3422" },
+	{ }
+};
+MODULE_DEVICE_TABLE(of, mcp3422_of_match);
+#endif
+
+static struct i2c_driver mcp3422_driver = {
+	.driver = {
+		.name = "mcp3422",
+		.owner = THIS_MODULE,
+		.of_match_table = of_match_ptr(mcp3422_of_match),
+	},
+	.probe = mcp3422_probe,
+	.remove = mcp3422_remove,
+	.id_table = mcp3422_id,
+};
+module_i2c_driver(mcp3422_driver);
+
+MODULE_AUTHOR("Angelo Compagnucci <[email protected]>");
+MODULE_DESCRIPTION("Microchip mcp3422/3/4 driver");
+MODULE_LICENSE("GPL v2");