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/Kconfig b/drivers/iio/adc/Kconfig
index e4022fd..6eac923 100644 (file)
--- a/drivers/iio/adc/Kconfig
+++ b/drivers/iio/adc/Kconfig
@@ -264,6 +264,15 @@ config LPC18XX_ADC
          To compile this driver as a module, choose M here: the module will be
          called lpc18xx_adc.
 
+config LTC2485
+       tristate "Linear Technology LTC2485 ADC driver"
+       depends on I2C
+       help
+         Say yes here to build support for Linear Technology LTC2485 ADC.
+
+         To compile this driver as a module, choose M here: the module will be
+         called ltc2485.
+
 config MAX1027
        tristate "Maxim max1027 ADC driver"
        depends on SPI

diff --git a/drivers/iio/adc/Makefile b/drivers/iio/adc/Makefile
index 33254eb..f46dd1f 100644 (file)
--- a/drivers/iio/adc/Makefile
+++ b/drivers/iio/adc/Makefile
@@ -27,6 +27,7 @@ obj-$(CONFIG_IMX7D_ADC) += imx7d_adc.o
 obj-$(CONFIG_INA2XX_ADC) += ina2xx-adc.o
 obj-$(CONFIG_LP8788_ADC) += lp8788_adc.o
 obj-$(CONFIG_LPC18XX_ADC) += lpc18xx_adc.o
+obj-$(CONFIG_LTC2485) += ltc2485.o
 obj-$(CONFIG_MAX1027) += max1027.o
 obj-$(CONFIG_MAX1363) += max1363.o
 obj-$(CONFIG_MCP320X) += mcp320x.o

diff --git a/drivers/iio/adc/ltc2485.c b/drivers/iio/adc/ltc2485.c
new file mode 100644 (file)
index 0000000..eab91f1
--- /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 = &ltc2485_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");