[PATCH] Add mcp3422 kernel driver

[Angelo Compagnucci <angelo.compagnucci@gmail.com>]

Signed-off-by: Angelo Compagnucci <angelo.compagnucci@gmail.com>
---
 drivers/iio/adc/Kconfig   |   10 ++
 drivers/iio/adc/Makefile  |    1 +
 drivers/iio/adc/mcp3422.c |  400 +++++++++++++++++++++++++++++++++++++++++++++
 3 files changed, 411 insertions(+)
 create mode 100644 drivers/iio/adc/mcp3422.c

diff --git a/drivers/iio/adc/Kconfig b/drivers/iio/adc/Kconfig
index 93129ec..372667c 100644
--- a/drivers/iio/adc/Kconfig
+++ b/drivers/iio/adc/Kconfig
@@ -143,6 +143,16 @@ 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 TI_ADC081C
 	tristate "Texas Instruments ADC081C021/027"
 	depends on I2C
diff --git a/drivers/iio/adc/Makefile b/drivers/iio/adc/Makefile
index 8f475d3..bae9f67 100644
--- a/drivers/iio/adc/Makefile
+++ b/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-$(CONFIG_MCP3422) += mcp3422.o
 obj-$(CONFIG_TI_ADC081C) += ti-adc081c.o
 obj-$(CONFIG_TI_AM335X_ADC) += ti_am335x_adc.o
 obj-$(CONFIG_VIPERBOARD_ADC) += viperboard_adc.o
diff --git a/drivers/iio/adc/mcp3422.c b/drivers/iio/adc/mcp3422.c
new file mode 100644
index 0000000..d45bbbe
--- /dev/null
+++ b/drivers/iio/adc/mcp3422.c
@@ -0,0 +1,400 @@
+/*
+ * mcp3422.c - driver for the Microchip mcp3422/3/4 chip family
+ *
+ * Copyright (C) 2013, Angelo Compagnucci
+ * Author: Angelo Compagnucci <angelo.compagnucci@gmail.com>
+ *
+ * Datasheet: http://ww1.microchip.com/downloads/en/devicedoc/22088b.pdf
+ *
+ * This driver export 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/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_CHANNEL(config)	(((config) & MCP3422_CHANNEL_MASK) >> 5)
+#define MCP3422_PGA(config)	((config) & MCP3422_PGA_MASK)
+#define MCP3422_SAMPLE_RATE(config)	(((config) & MCP3422_SRATE_MASK) >> 2)
+
+#define VREF 2048
+
+#define MCP3422_CHAN(index) \
+	{ \
+		.type = IIO_VOLTAGE, \
+		.indexed = 1, \
+		.channel = index, \
+		.address = index, \
+		.scan_index = index, \
+		.info_mask_shared_by_type = BIT(IIO_CHAN_INFO_SCALE), \
+		.info_mask_separate = BIT(IIO_CHAN_INFO_RAW), \
+	}
+
+/* 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;
+};
+
+static int mcp3422_update_config(struct mcp3422 *adc)
+{
+	u8 buf[1];
+	buf[0] = adc->config;
+	return i2c_master_send(adc->i2c, buf, 1);
+}
+
+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'};
+
+	*value = 0;
+
+	if (sample_rate == MCP3422_SRATE_3) {
+		ret = i2c_master_recv(adc->i2c, buf, 4);
+		*value += (s8)buf[0];
+		*value <<= 16;
+		*value |= buf[1] << 8;
+		*value |= buf[2];
+		*config = buf[3];
+		if (*value == 0xFFFFFFFF)
+			*value = 0;
+	} else {
+		ret = i2c_master_recv(adc->i2c, buf, 3);
+		*value += (s8)buf[0];
+		*value <<= 8;
+		*value |= buf[1];
+		*config = buf[2];
+	}
+
+	return ret;
+}
+
+static int mcp3422_read_channel(struct mcp3422 *adc,
+				struct iio_chan_spec const *channel, int *value)
+{
+	int ret, mtime = 0;
+	u8 current_config = 0;
+	u8 req_channel = channel->channel - 1;
+
+	ret = mcp3422_read(adc, value, &current_config);
+
+	if (req_channel != MCP3422_CHANNEL(current_config)) {
+		adc->config &= ~MCP3422_CHANNEL_MASK;
+		adc->config |= ((req_channel << 5) & MCP3422_CHANNEL_MASK);
+		mcp3422_update_config(adc);
+		switch (MCP3422_SAMPLE_RATE(current_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);
+		ret = mcp3422_read(adc, value, &current_config);
+	}
+	return ret;
+}
+
+static int mcp3422_read_raw(struct iio_dev *iio,
+			    struct iio_chan_spec const *channel, int *value,
+			    int *shift, 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);
+
+	switch (mask) {
+	case IIO_CHAN_INFO_RAW:
+		err = mcp3422_read_channel(adc, channel, &temp);
+		if (err < 0)
+			return err;
+
+		/*
+		* Converting the output
+		*/
+		*value = (temp * rates_to_lsb[sample_rate])
+					/ (pga ? 1 << pga : 1);
+
+		return IIO_VAL_INT;
+
+	case IIO_CHAN_INFO_SCALE:
+
+		*value = VREF * 1000000;
+
+		return IIO_VAL_INT;
+
+	default:
+		break;
+	}
+
+	return -EINVAL;
+}
+
+static ssize_t mcp3422_set_sample_rate(struct device *dev,
+		struct device_attribute *attr,
+		const char *buf, size_t count)
+{
+	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;
+
+	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;
+	}
+
+	adc->config &= ~MCP3422_SRATE_MASK;
+	adc->config |= ((value << 2) & MCP3422_SRATE_MASK);
+
+	mcp3422_update_config(adc);
+
+	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 0:
+		value = 240;
+		break;
+	case 1:
+		value = 60;
+		break;
+	case 2:
+		value = 15;
+		break;
+	case 3:
+		value = 3;
+		break;
+	}
+
+	return sprintf(buf, "%d\n", value);
+}
+
+static ssize_t mcp3422_set_pga(struct device *dev,
+		struct device_attribute *attr,
+		const char *buf, size_t count)
+{
+	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;
+
+	if (kstrtou8(buf, 10, &value) < 0)
+		return -EINVAL;
+
+	switch (value) {
+	case 1:
+		value = 0;
+		break;
+	case 2:
+		value = 1;
+		break;
+	case 4:
+		value = 2;
+		break;
+	case 8:
+		value = 3;
+		break;
+	default:
+		return -EINVAL;
+	}
+
+	adc->config &= ~MCP3422_PGA_MASK;
+	adc->config |= (value & MCP3422_PGA_MASK);
+
+	mcp3422_update_config(adc);
+
+	return count;
+}
+
+static ssize_t mcp3422_get_pga(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);
+
+	return sprintf(buf, "%d\n", 1 << MCP3422_PGA(adc->config));
+}
+
+static IIO_DEV_ATTR_SAMP_FREQ(S_IRUGO | S_IWUSR,
+			mcp3422_get_sample_rate,
+			mcp3422_set_sample_rate);
+static IIO_DEVICE_ATTR(pga,
+			S_IRUGO | S_IWUSR,
+			mcp3422_get_pga,
+			mcp3422_set_pga, 0);
+static IIO_CONST_ATTR(sampling_frequency_available, "240 60 15 3");
+static IIO_CONST_ATTR(pga_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,
+	&iio_dev_attr_pga.dev_attr.attr,
+	&iio_const_attr_pga_available.dev_attr.attr,
+	NULL,
+};
+
+static const struct attribute_group mcp3422_attribute_group = {
+	.attrs = mcp3422_attributes,
+};
+
+static const struct iio_chan_spec mcp3422_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,
+	.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 *iio;
+	struct mcp3422 *adc;
+	int err;
+
+	if (!i2c_check_functionality(client->adapter, I2C_FUNC_SMBUS_WORD_DATA))
+		return -ENODEV;
+
+	iio = iio_device_alloc(sizeof(*adc));
+	if (!iio)
+		return -ENOMEM;
+
+	adc = iio_priv(iio);
+	adc->i2c = client;
+
+	/* meaningful default configuration */
+	adc->config = 0x10;
+
+	iio->dev.parent = &client->dev;
+	iio->name = dev_name(&client->dev);
+	iio->modes = INDIO_DIRECT_MODE;
+	iio->info = &mcp3422_info;
+
+	iio->channels = mcp3422_channels;
+	iio->num_channels = ARRAY_SIZE(mcp3422_channels);
+
+	err = iio_device_register(iio);
+	if (err < 0)
+		goto iio_free;
+
+	i2c_set_clientdata(client, iio);
+
+	mcp3422_update_config(adc);
+
+	return 0;
+
+iio_free:
+	iio_device_free(iio);
+
+	return err;
+}
+
+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 <angelo.compagnucci@gmail.com>");
+MODULE_DESCRIPTION("Microchip mcp3422/3/4 driver");
+MODULE_LICENSE("GPL v2");
-- 
1.7.9.5