[PATCH] iio: Add LTC2471/LTC2473 driver

Mike Looijmans
2017-06-30T07:21:18Z

The LTC2741 and LTC2473 are single voltage ADC chips. The LTC2473
is similar to the LTC2471 but outputs a signed differential value.

Datasheet:
http://cds.linear.com/docs/en/datasheet/24713fb.pdf

Signed-off-by: Mike Looijmans <mike.looijmans@topic.nl>
---
Note: Moved from "hwmon" subsystem to "iio" as discussed per e-mail,
see also: https://patchwork.kernel.org/patch/9816607/
Only tested the LTC2741 in real life.

drivers/iio/adc/Kconfig | 10 +++
drivers/iio/adc/Makefile | 1 +
drivers/iio/adc/ltc2471.c | 163 ++++++++++++++++++++++++++++++++++++++++++++++
3 files changed, 174 insertions(+)
create mode 100644 drivers/iio/adc/ltc2471.c

diff --git a/drivers/iio/adc/Kconfig b/drivers/iio/adc/Kconfig
index 401f47b..fbee44a 100644
--- a/drivers/iio/adc/Kconfig
+++ b/drivers/iio/adc/Kconfig
@@ -362,6 +362,16 @@ config LPC32XX_ADC
activate only one via device tree selection. Provides direct access
via sysfs.

+config LTC2471
+ tristate "Linear Technology LTC2471 and LTC2473 ADC driver"
+ depends on I2C
+ help
+ Say yes here to build support for Linear Technology LTC2471 and
+ LTC2473 ADC.
+
+ This driver can also be built as a module. If so, the module will
+ be called ltc2471.
+
config LTC2485
tristate "Linear Technology LTC2485 ADC driver"
depends on I2C
diff --git a/drivers/iio/adc/Makefile b/drivers/iio/adc/Makefile
index 9339bec..afafe85 100644
--- a/drivers/iio/adc/Makefile
+++ b/drivers/iio/adc/Makefile
@@ -34,6 +34,7 @@ obj-$(CONFIG_INA2XX_ADC) += ina2xx-adc.o
obj-$(CONFIG_LP8788_ADC) += lp8788_adc.o
obj-$(CONFIG_LPC18XX_ADC) += lpc18xx_adc.o
obj-$(CONFIG_LPC32XX_ADC) += lpc32xx_adc.o
+obj-$(CONFIG_LTC2471) += ltc2471.o
obj-$(CONFIG_LTC2485) += ltc2485.o
obj-$(CONFIG_LTC2497) += ltc2497.o
obj-$(CONFIG_MAX1027) += max1027.o
diff --git a/drivers/iio/adc/ltc2471.c b/drivers/iio/adc/ltc2471.c
new file mode 100644
index 0000000..f26bdad
--- /dev/null
+++ b/drivers/iio/adc/ltc2471.c
@@ -0,0 +1,163 @@
+/*
+ * Driver for Linear Technology LTC2471 and LTC2473 voltage monitors
+ * The LTC2473 is identical to the 2471, but reports a differential signal.
+ *
+ * Copyright (C) 2017 Topic Embedded Products
+ * Author: Mike Looijmans <mike.looijmans@topic.nl>
+ *
+ * License: GPLv2
+ */
+
+#include <linux/err.h>
+#include <linux/i2c.h>
+#include <linux/kernel.h>
+#include <linux/module.h>
+#include <linux/iio/iio.h>
+#include <linux/iio/sysfs.h>
+
+enum chips {
+ ltc2471,
+ ltc2473
+};
+
+struct ltc2471_data {
+ struct i2c_client *client;
+};
+
+/* Reference voltage is 1.25V */
+#define LTC2471_VREF 1250
+
+/* Read two bytes from the I2C bus to obtain the ADC result */
+static int ltc2471_get_value(struct i2c_client *client)
+{
+ int ret;
+ __be16 buf;
+
+ ret = i2c_master_recv(client, (char *)&buf, 2);
+ if (ret < 0)
+ return ret;
+ if (ret != 2)
+ return -EIO;
+
+ /* MSB first */
+ return be16_to_cpu(buf);
+}
+
+static int ltc2471_read_raw(struct iio_dev *indio_dev,
+ struct iio_chan_spec const *chan,
+ int *val, int *val2, long info)
+{
+ struct ltc2471_data *data = iio_priv(indio_dev);
+ int ret;
+
+ switch (info) {
+ case IIO_CHAN_INFO_RAW:
+ ret = ltc2471_get_value(data->client);
+ if (ret < 0)
+ return ret;
+ *val = ret;
+ return IIO_VAL_INT;
+
+ case IIO_CHAN_INFO_SCALE:
+ if (chan->differential)
+ /* Output ranges from -VREF to +VREF */
+ *val = 2 * LTC2471_VREF;
+ else
+ /* Output ranges from 0 to VREF */
+ *val = LTC2471_VREF;
+ *val2 = 16; /* 16 data bits */
+ return IIO_VAL_FRACTIONAL_LOG2;
+
+ case IIO_CHAN_INFO_OFFSET:
+ if (chan->differential)
+ *val = -LTC2471_VREF;
+ else
+ *val = 0;
+ return IIO_VAL_INT;
+
+ default:
+ return -EINVAL;
+ }
+}
+
+static const struct iio_chan_spec ltc2471_channel[] = {
+ {
+ .type = IIO_VOLTAGE,
+ .info_mask_separate = BIT(IIO_CHAN_INFO_RAW),
+ .info_mask_shared_by_type = BIT(IIO_CHAN_INFO_SCALE),
+ .differential = 0,
+ },
+};
+static const struct iio_chan_spec ltc2473_channel[] = {
+ {
+ .type = IIO_VOLTAGE,
+ .info_mask_separate = BIT(IIO_CHAN_INFO_RAW),
+ .info_mask_shared_by_type = BIT(IIO_CHAN_INFO_SCALE) |
+ BIT(IIO_CHAN_INFO_OFFSET),
+ .differential = 1,
+ },
+};
+
+static const struct iio_info ltc2471_info = {
+ .read_raw = ltc2471_read_raw,
+ .driver_module = THIS_MODULE,
+};
+
+static int ltc2471_i2c_probe(struct i2c_client *client,
+ const struct i2c_device_id *id)
+{
+ struct iio_dev *indio_dev;
+ struct ltc2471_data *data;
+ int ret;
+
+ if (!i2c_check_functionality(client->adapter, I2C_FUNC_I2C))
+ return -EOPNOTSUPP;
+
+ indio_dev = devm_iio_device_alloc(&client->dev, sizeof(*data));
+ if (!indio_dev)
+ return -ENOMEM;
+
+ data = iio_priv(indio_dev);
+ i2c_set_clientdata(client, indio_dev);
+ data->client = client;
+
+ indio_dev->dev.parent = &client->dev;
+ indio_dev->name = id->name;
+ indio_dev->info = &ltc2471_info;
+ indio_dev->modes = INDIO_DIRECT_MODE;
+ if (id->driver_data == ltc2473)
+ indio_dev->channels = ltc2473_channel;
+ else
+ indio_dev->channels = ltc2471_channel;
+ indio_dev->num_channels = 1;
+
+ /* Trigger once to start conversion and check if chip is there */
+ ret = ltc2471_get_value(client);
+ if (ret < 0) {
+ dev_err(&client->dev, "Cannot read from device.\n");
+ return ret;
+ }
+
+ return devm_iio_device_register(&client->dev, indio_dev);
+}
+
+static const struct i2c_device_id ltc2471_i2c_id[] = {
+ { "ltc2471", ltc2471 },
+ { "ltc2473", ltc2473 },
+ {}
+};
+MODULE_DEVICE_TABLE(i2c, ltc2471_i2c_id);
+
+static struct i2c_driver ltc2471_i2c_driver = {
+ .driver = {
+ .name = "ltc2471",
+ },
+ .probe = ltc2471_i2c_probe,
+ .id_table = ltc2471_i2c_id,
+};
+
+module_i2c_driver(ltc2471_i2c_driver);
+
+MODULE_DESCRIPTION("LTC2471/LTC2473 Sensor Driver");
+MODULE_AUTHOR("Topic Embedded Products");
+MODULE_LICENSE("GPL v2");
--
1.9.1