[PATCH/RFC v9 ] Add Microchip MCP3422/3/4 high resolution ADC

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

I think this patch solves last Jonathan's concerns.

Following a use case from a running chip, just to be sure the driver
works like it should:

# cat in_voltage0_*
2047
0.001000000 //this is the scale
# echo 3 > in_voltage_sampling_frequency 
# cat in_voltage0_*
131071
0.000015625 //this is the scale
# echo 8 > in_voltage0_scale 
# cat in_voltage0_*
25          //small voltage value to see the pga in action
0.000001953 //this is the scale

So in the first case, 2047 * 0.001 = 2.047, 
in the second one 131071 * 0.000015625 = 2.047984375, 
in the third one 25 * 0.000001953 = 0.000048825, 
on all three cases I have the expected values.

Is ths correct?

Thank you!

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(+), 0 deletions(-)
 create mode 100644 drivers/iio/adc/mcp3422.c

diff --git a/drivers/iio/adc/Kconfig b/drivers/iio/adc/Kconfig
index f725b45..e9879e6 100644
--- a/drivers/iio/adc/Kconfig
+++ b/drivers/iio/adc/Kconfig
@@ -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
diff --git a/drivers/iio/adc/Makefile b/drivers/iio/adc/Makefile
index 2a4324e..9772e3b 100644
--- a/drivers/iio/adc/Makefile
+++ b/drivers/iio/adc/Makefile
@@ -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
diff --git a/drivers/iio/adc/mcp3422.c b/drivers/iio/adc/mcp3422.c
new file mode 100644
index 0000000..722a835
--- /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 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/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)
+#define MCP3422_PGA(config)	((config) & MCP3422_PGA_MASK)
+#define MCP3422_SAMPLE_RATE(config)	(((config) & MCP3422_SRATE_MASK) >> 2)
+
+#define MCP3422_CHANNEL_VALUE(value) (((value) << 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), \
+		.info_mask_shared_by_type = BIT(IIO_CHAN_INFO_SAMP_FREQ), \
+	}
+
+/* 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;
+		ret = 0;
+	}
+
+	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, ret;
+	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]);
+		ret = mcp3422_update_config(adc, config);
+		if (ret <= 0)
+			return ret;
+		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 = rates_to_lsb[sample_rate] / (pga ? 1 << pga : 1);
+
+		*val1 = 0;
+		*val2 = temp;
+		return IIO_VAL_INT_PLUS_NANO;
+
+	case IIO_CHAN_INFO_SAMP_FREQ:
+		switch (MCP3422_SAMPLE_RATE(adc->config)) {
+		case MCP3422_SRATE_240:
+			*val1 = 240;
+			break;
+		case MCP3422_SRATE_60:
+			*val1 = 60;
+			break;
+		case MCP3422_SRATE_15:
+			*val1 = 15;
+			break;
+		case MCP3422_SRATE_3:
+			*val1 = 3;
+			break;
+		}
+		return IIO_VAL_INT;
+
+	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 temp;
+	u8 config = adc->config;
+	u8 req_channel = channel->channel;
+
+	switch (mask) {
+	case IIO_CHAN_INFO_SCALE:
+		switch (val1) {
+		case 1:
+			temp = MCP3422_PGA_1;
+			break;
+		case 2:
+			temp = MCP3422_PGA_2;
+			break;
+		case 4:
+			temp = MCP3422_PGA_4;
+			break;
+		case 8:
+			temp = MCP3422_PGA_8;
+			break;
+		default:
+			return -EINVAL;
+		}
+
+		adc->pga[req_channel] = temp;
+
+		config &= ~MCP3422_CHANNEL_MASK;
+		config |= MCP3422_CHANNEL_VALUE(req_channel);
+		config &= ~MCP3422_PGA_MASK;
+		config |= MCP3422_PGA_VALUE(adc->pga[req_channel]);
+		
+		return mcp3422_update_config(adc, config);
+
+	case IIO_CHAN_INFO_SAMP_FREQ:
+		switch (val1) {
+		case 240:
+			temp = MCP3422_SRATE_240;
+			break;
+		case 60:
+			temp = MCP3422_SRATE_60;
+			break;
+		case 15:
+			temp = MCP3422_SRATE_15;
+			break;
+		case 3:
+			temp = MCP3422_SRATE_3;
+			break;
+		default:
+			return -EINVAL;
+		}
+
+		config &= ~MCP3422_CHANNEL_MASK;
+		config |= MCP3422_CHANNEL_VALUE(req_channel);
+		config &= ~MCP3422_SRATE_MASK;
+		config |= MCP3422_SAMPLE_RATE_VALUE(temp);
+
+		return mcp3422_update_config(adc, config);
+		
+	default:
+		break;
+	}
+
+	return -EINVAL;
+}
+
+static IIO_CONST_ATTR_SAMP_FREQ_AVAIL("240 60 15 3");
+static IIO_CONST_ATTR(in_voltage_scale_available, "1 2 4 8");
+
+static struct attribute *mcp3422_attributes[] = {
+	&iio_const_attr_sampling_frequency_available.dev_attr.attr,
+	&iio_const_attr_in_voltage_scale_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(0),
+	MCP3422_CHAN(1),
+};
+
+static const struct iio_chan_spec mcp3424_channels[] = {
+	MCP3422_CHAN(0),
+	MCP3422_CHAN(1),
+	MCP3422_CHAN(2),
+	MCP3422_CHAN(3),
+};
+
+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;
+
+	if (!i2c_check_functionality(client->adapter, I2C_FUNC_I2C))
+		return -ENODEV;
+
+	indio_dev = devm_iio_device_alloc(&client->dev, sizeof(*adc));
+	if (!indio_dev)
+		return -ENOMEM;
+
+	adc = iio_priv(indio_dev);
+	adc->i2c = client;
+
+	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;
+	}
+
+	/* meaningful default configuration */
+	config = (MCP3422_CONT_SAMPLING
+		| MCP3422_CHANNEL_VALUE(1)
+		| MCP3422_PGA_VALUE(MCP3422_PGA_1)
+		| MCP3422_SAMPLE_RATE_VALUE(MCP3422_SRATE_240));
+	mcp3422_update_config(adc, config);
+
+	err = iio_device_register(indio_dev);
+	if (err < 0)
+		return err;
+
+	i2c_set_clientdata(client, indio_dev);
+
+	return 0;
+}
+
+static int mcp3422_remove(struct i2c_client *client)
+{
+	iio_device_unregister(i2c_get_clientdata(client));
+	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");
-- 
1.7.5.4