iio: adc: ltc2485: add support for Linear Technology LTC2485 ADC
Adds basic support for the LTC2485 ADC - a delta-sigma analog-to-digital
converter with an I2C interface that operates in single shot conversion
mode.
The driver supports an on board 5V reference and the power-on default
configuration which rejects both 50hz & 60hz line frequencies and
operates in 1x speed mode.
Signed-off-by: Alison Schofield <amsfield22@gmail.com>
Cc: Daniel Baluta <daniel.baluta@gmail.com>
Signed-off-by: Jonathan Cameron <jic23@kernel.org>
diff --git a/drivers/iio/adc/ltc2485.c b/drivers/iio/adc/ltc2485.c
new file mode 100644
index 0000000..eab91f12
--- /dev/null
+++ b/drivers/iio/adc/ltc2485.c
@@ -0,0 +1,148 @@
+/*
+ * ltc2485.c - Driver for Linear Technology LTC2485 ADC
+ *
+ * Copyright (C) 2016 Alison Schofield <amsfield22@gmail.com>
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License version 2 as
+ * published by the Free Software Foundation.
+ *
+ * Datasheet: http://cds.linear.com/docs/en/datasheet/2485fd.pdf
+ */
+
+#include <linux/delay.h>
+#include <linux/i2c.h>
+#include <linux/module.h>
+
+#include <linux/iio/iio.h>
+#include <linux/iio/sysfs.h>
+
+/* Power-on configuration: rejects both 50/60Hz, operates at 1x speed */
+#define LTC2485_CONFIG_DEFAULT 0
+
+struct ltc2485_data {
+ struct i2c_client *client;
+ ktime_t time_prev; /* last conversion */
+};
+
+static void ltc2485_wait_conv(struct ltc2485_data *data)
+{
+ const unsigned int conv_time = 147; /* conversion time ms */
+ unsigned int time_elapsed;
+
+ /* delay if conversion time not passed since last read or write */
+ time_elapsed = ktime_ms_delta(ktime_get(), data->time_prev);
+
+ if (time_elapsed < conv_time)
+ msleep(conv_time - time_elapsed);
+}
+
+static int ltc2485_read(struct ltc2485_data *data, int *val)
+{
+ struct i2c_client *client = data->client;
+ __be32 buf = 0;
+ int ret;
+
+ ltc2485_wait_conv(data);
+
+ ret = i2c_master_recv(client, (char *)&buf, 4);
+ if (ret < 0) {
+ dev_err(&client->dev, "i2c_master_recv failed\n");
+ return ret;
+ }
+ data->time_prev = ktime_get();
+ *val = sign_extend32(be32_to_cpu(buf) >> 6, 24);
+
+ return ret;
+}
+
+static int ltc2485_read_raw(struct iio_dev *indio_dev,
+ struct iio_chan_spec const *chan,
+ int *val, int *val2, long mask)
+{
+ struct ltc2485_data *data = iio_priv(indio_dev);
+ int ret;
+
+ if (mask == IIO_CHAN_INFO_RAW) {
+ ret = ltc2485_read(data, val);
+ if (ret < 0)
+ return ret;
+
+ return IIO_VAL_INT;
+
+ } else if (mask == IIO_CHAN_INFO_SCALE) {
+ *val = 5000; /* on board vref millivolts */
+ *val2 = 25; /* 25 (24 + sign) data bits */
+ return IIO_VAL_FRACTIONAL_LOG2;
+
+ } else {
+ return -EINVAL;
+ }
+}
+
+static const struct iio_chan_spec ltc2485_channel[] = {
+ {
+ .type = IIO_VOLTAGE,
+ .info_mask_separate = BIT(IIO_CHAN_INFO_RAW),
+ .info_mask_shared_by_type = BIT(IIO_CHAN_INFO_SCALE)
+ },
+};
+
+static const struct iio_info ltc2485_info = {
+ .read_raw = ltc2485_read_raw,
+ .driver_module = THIS_MODULE,
+};
+
+static int ltc2485_probe(struct i2c_client *client,
+ const struct i2c_device_id *id)
+{
+ struct iio_dev *indio_dev;
+ struct ltc2485_data *data;
+ int ret;
+
+ if (!i2c_check_functionality(client->adapter, I2C_FUNC_I2C |
+ I2C_FUNC_SMBUS_WRITE_BYTE))
+ 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 = <c2485_info;
+ indio_dev->modes = INDIO_DIRECT_MODE;
+ indio_dev->channels = ltc2485_channel;
+ indio_dev->num_channels = ARRAY_SIZE(ltc2485_channel);
+
+ ret = i2c_smbus_write_byte(data->client, LTC2485_CONFIG_DEFAULT);
+ if (ret < 0)
+ return ret;
+
+ data->time_prev = ktime_get();
+
+ return devm_iio_device_register(&client->dev, indio_dev);
+}
+
+static const struct i2c_device_id ltc2485_id[] = {
+ { "ltc2485", 0 },
+ { }
+};
+MODULE_DEVICE_TABLE(i2c, ltc2485_id);
+
+static struct i2c_driver ltc2485_driver = {
+ .driver = {
+ .name = "ltc2485",
+ },
+ .probe = ltc2485_probe,
+ .id_table = ltc2485_id,
+};
+module_i2c_driver(ltc2485_driver);
+
+MODULE_AUTHOR("Alison Schofield <amsfield22@gmail.com>");
+MODULE_DESCRIPTION("Linear Technology LTC2485 ADC driver");
+MODULE_LICENSE("GPL v2");