Commit 8c9e7b1b authored by Alison Schofield's avatar Alison Schofield Committed by Jonathan Cameron
Browse files

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: default avatarAlison Schofield <amsfield22@gmail.com>
Cc: Daniel Baluta <daniel.baluta@gmail.com>
Signed-off-by: default avatarJonathan Cameron <jic23@kernel.org>
parent a5211b0d

drivers/iio/adc/Kconfig

+9 −0
Original line number Diff line number Diff line
@@ -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

drivers/iio/adc/Makefile

+1 −0
Original line number Diff line number Diff line
@@ -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

drivers/iio/adc/ltc2485.c

0 → 100644
+148 −0
Original line number Diff line number Diff line 
/*

 * 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");