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Commit bc82222f authored by Michael Hennerich's avatar Michael Hennerich Committed by Jonathan Cameron
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iio:adc: Driver for Linear Technology LTC2497 ADC 



This patch adds support for the Analog Devices / Linear Technology
LTC2497 ADCs. The LTC2497 is a 16-channel (eight differential),
16-bit, high precision, delta-sigma ADC with an automatic, differential,
input current cancellation front end and a 2-wire, I2C interface.

Signed-off-by: default avatarMichael Hennerich <michael.hennerich@analog.com>
Signed-off-by: default avatarJonathan Cameron <jic23@kernel.org>
parent 13e283d6

Documentation/devicetree/bindings/iio/adc/ltc2497.txt

0 → 100644
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* Linear Technology / Analog Devices LTC2497 ADC



Required properties:

 - compatible: Must be "lltc,ltc2497"

 - reg: Must contain the ADC I2C address

 - vref-supply: The regulator supply for ADC reference voltage



Example:

	ltc2497: adc@76 {

		compatible = "lltc,ltc2497";

		reg = <0x76>;

		vref-supply = <&ltc2497_reg>;

	};

MAINTAINERS

+1 −0
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@@ -813,6 +813,7 @@ W: http://wiki.analog.com/ 
W:	http://ez.analog.com/community/linux-device-drivers

S:	Supported

F:	drivers/iio/*/ad*

F:	drivers/iio/adc/ltc2497*

X:	drivers/iio/*/adjd*

F:	drivers/staging/iio/*/ad*

F:	drivers/staging/iio/trigger/iio-trig-bfin-timer.c

drivers/iio/adc/Kconfig

+10 −0
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@@ -348,6 +348,16 @@ config LTC2485 
	  To compile this driver as a module, choose M here: the module will be

	  called ltc2485.



config LTC2497

	tristate "Linear Technology LTC2497 ADC driver"

	depends on I2C

	help

	  Say yes here to build support for Linear Technology LTC2497

	  16-Bit 8-/16-Channel Delta Sigma ADC.



	  To compile this driver as a module, choose M here: the module will be

	  called ltc2497.



config MAX1027

	tristate "Maxim max1027 ADC driver"

	depends on SPI

drivers/iio/adc/Makefile

+1 −0
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@@ -34,6 +34,7 @@ obj-$(CONFIG_LP8788_ADC) += lp8788_adc.o 
obj-$(CONFIG_LPC18XX_ADC) += lpc18xx_adc.o

obj-$(CONFIG_LPC32XX_ADC) += lpc32xx_adc.o

obj-$(CONFIG_LTC2485) += ltc2485.o

obj-$(CONFIG_LTC2497) += ltc2497.o

obj-$(CONFIG_MAX1027) += max1027.o

obj-$(CONFIG_MAX11100) += max11100.o

obj-$(CONFIG_MAX1363) += max1363.o

drivers/iio/adc/ltc2497.c

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/*

 * ltc2497.c - Driver for Analog Devices/Linear Technology LTC2497 ADC

 *

 * Copyright (C) 2017 Analog Devices Inc.

 *

 * Licensed under the GPL-2.

 *

 * Datasheet: http://cds.linear.com/docs/en/datasheet/2497fd.pdf

 */



#include <linux/delay.h>

#include <linux/i2c.h>

#include <linux/iio/iio.h>

#include <linux/iio/sysfs.h>

#include <linux/module.h>

#include <linux/of.h>

#include <linux/regulator/consumer.h>



#define LTC2497_ENABLE			0xA0

#define LTC2497_SGL			BIT(4)

#define LTC2497_DIFF			0

#define LTC2497_SIGN			BIT(3)

#define LTC2497_CONFIG_DEFAULT		LTC2497_ENABLE

#define LTC2497_CONVERSION_TIME_MS	150ULL



struct ltc2497_st {

	struct i2c_client *client;

	struct regulator *ref;

	ktime_t	time_prev;

	u8 addr_prev;

	/*

	 * DMA (thus cache coherency maintenance) requires the

	 * transfer buffers to live in their own cache lines.

	 */

	__be32 buf ____cacheline_aligned;

};



static int ltc2497_wait_conv(struct ltc2497_st *st)

{

	s64 time_elapsed;



	time_elapsed = ktime_ms_delta(ktime_get(), st->time_prev);



	if (time_elapsed < LTC2497_CONVERSION_TIME_MS) {

		/* delay if conversion time not passed

		 * since last read or write

		 */

		if (msleep_interruptible(

		    LTC2497_CONVERSION_TIME_MS - time_elapsed))

			return -ERESTARTSYS;



		return 0;

	}



	if (time_elapsed - LTC2497_CONVERSION_TIME_MS <= 0) {

		/* We're in automatic mode -

		 * so the last reading is stil not outdated

		 */

		return 0;

	}



	return 1;

}



static int ltc2497_read(struct ltc2497_st *st, u8 address, int *val)

{

	struct i2c_client *client = st->client;

	int ret;



	ret = ltc2497_wait_conv(st);

	if (ret < 0)

		return ret;



	if (ret || st->addr_prev != address) {

		ret = i2c_smbus_write_byte(st->client,

					   LTC2497_ENABLE | address);

		if (ret < 0)

			return ret;

		st->addr_prev = address;

		if (msleep_interruptible(LTC2497_CONVERSION_TIME_MS))

			return -ERESTARTSYS;

	}

	ret = i2c_master_recv(client, (char *)&st->buf, 3);

	if (ret < 0)  {

		dev_err(&client->dev, "i2c_master_recv failed\n");

		return ret;

	}

	st->time_prev = ktime_get();



	/* convert and shift the result,

	 * and finally convert from offset binary to signed integer

	 */

	*val = (be32_to_cpu(st->buf) >> 14) - (1 << 17);



	return ret;

}



static int ltc2497_read_raw(struct iio_dev *indio_dev,

			    struct iio_chan_spec const *chan,

			    int *val, int *val2, long mask)

{

	struct ltc2497_st *st = iio_priv(indio_dev);

	int ret;



	switch (mask) {

	case IIO_CHAN_INFO_RAW:

		mutex_lock(&indio_dev->mlock);

		ret = ltc2497_read(st, chan->address, val);

		mutex_unlock(&indio_dev->mlock);

		if (ret < 0)

			return ret;



		return IIO_VAL_INT;



	case IIO_CHAN_INFO_SCALE:

		ret = regulator_get_voltage(st->ref);

		if (ret < 0)

			return ret;



		*val = ret / 1000;

		*val2 = 17;



		return IIO_VAL_FRACTIONAL_LOG2;



	default:

		return -EINVAL;

	}

}



#define LTC2497_CHAN(_chan, _addr) { \

	.type = IIO_VOLTAGE, \

	.indexed = 1, \

	.channel = (_chan), \

	.address = (_addr | (_chan / 2) | ((_chan & 1) ? LTC2497_SIGN : 0)), \

	.info_mask_separate = BIT(IIO_CHAN_INFO_RAW), \

	.info_mask_shared_by_type = BIT(IIO_CHAN_INFO_SCALE), \

}



#define LTC2497_CHAN_DIFF(_chan, _addr) { \

	.type = IIO_VOLTAGE, \

	.indexed = 1, \

	.channel = (_chan) * 2 + ((_addr) & LTC2497_SIGN ? 1 : 0), \

	.channel2 = (_chan) * 2 + ((_addr) & LTC2497_SIGN ? 0 : 1),\

	.address = (_addr | _chan), \

	.info_mask_separate = BIT(IIO_CHAN_INFO_RAW), \

	.info_mask_shared_by_type = BIT(IIO_CHAN_INFO_SCALE), \

	.differential = 1, \

}



static const struct iio_chan_spec ltc2497_channel[] = {

	LTC2497_CHAN(0, LTC2497_SGL),

	LTC2497_CHAN(1, LTC2497_SGL),

	LTC2497_CHAN(2, LTC2497_SGL),

	LTC2497_CHAN(3, LTC2497_SGL),

	LTC2497_CHAN(4, LTC2497_SGL),

	LTC2497_CHAN(5, LTC2497_SGL),

	LTC2497_CHAN(6, LTC2497_SGL),

	LTC2497_CHAN(7, LTC2497_SGL),

	LTC2497_CHAN(8, LTC2497_SGL),

	LTC2497_CHAN(9, LTC2497_SGL),

	LTC2497_CHAN(10, LTC2497_SGL),

	LTC2497_CHAN(11, LTC2497_SGL),

	LTC2497_CHAN(12, LTC2497_SGL),

	LTC2497_CHAN(13, LTC2497_SGL),

	LTC2497_CHAN(14, LTC2497_SGL),

	LTC2497_CHAN(15, LTC2497_SGL),

	LTC2497_CHAN_DIFF(0, LTC2497_DIFF),

	LTC2497_CHAN_DIFF(1, LTC2497_DIFF),

	LTC2497_CHAN_DIFF(2, LTC2497_DIFF),

	LTC2497_CHAN_DIFF(3, LTC2497_DIFF),

	LTC2497_CHAN_DIFF(4, LTC2497_DIFF),

	LTC2497_CHAN_DIFF(5, LTC2497_DIFF),

	LTC2497_CHAN_DIFF(6, LTC2497_DIFF),

	LTC2497_CHAN_DIFF(7, LTC2497_DIFF),

	LTC2497_CHAN_DIFF(0, LTC2497_DIFF | LTC2497_SIGN),

	LTC2497_CHAN_DIFF(1, LTC2497_DIFF | LTC2497_SIGN),

	LTC2497_CHAN_DIFF(2, LTC2497_DIFF | LTC2497_SIGN),

	LTC2497_CHAN_DIFF(3, LTC2497_DIFF | LTC2497_SIGN),

	LTC2497_CHAN_DIFF(4, LTC2497_DIFF | LTC2497_SIGN),

	LTC2497_CHAN_DIFF(5, LTC2497_DIFF | LTC2497_SIGN),

	LTC2497_CHAN_DIFF(6, LTC2497_DIFF | LTC2497_SIGN),

	LTC2497_CHAN_DIFF(7, LTC2497_DIFF | LTC2497_SIGN),

};



static const struct iio_info ltc2497_info = {

	.read_raw = ltc2497_read_raw,

	.driver_module = THIS_MODULE,

};



static int ltc2497_probe(struct i2c_client *client,

			 const struct i2c_device_id *id)

{

	struct iio_dev *indio_dev;

	struct ltc2497_st *st;

	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(*st));

	if (!indio_dev)

		return -ENOMEM;



	st = iio_priv(indio_dev);

	i2c_set_clientdata(client, indio_dev);

	st->client = client;



	indio_dev->dev.parent = &client->dev;

	indio_dev->name = id->name;

	indio_dev->info = &ltc2497_info;

	indio_dev->modes = INDIO_DIRECT_MODE;

	indio_dev->channels = ltc2497_channel;

	indio_dev->num_channels = ARRAY_SIZE(ltc2497_channel);



	st->ref = devm_regulator_get(&client->dev, "vref");

	if (IS_ERR(st->ref))

		return PTR_ERR(st->ref);



	ret = regulator_enable(st->ref);

	if (ret < 0)

		return ret;



	ret = i2c_smbus_write_byte(st->client, LTC2497_CONFIG_DEFAULT);

	if (ret < 0)

		goto err_regulator_disable;



	st->addr_prev = LTC2497_CONFIG_DEFAULT;

	st->time_prev = ktime_get();



	ret = iio_device_register(indio_dev);

	if (ret < 0)

		goto err_regulator_disable;



	return 0;



err_regulator_disable:

	regulator_disable(st->ref);



	return ret;

}



static int ltc2497_remove(struct i2c_client *client)

{

	struct iio_dev *indio_dev = i2c_get_clientdata(client);

	struct ltc2497_st *st = iio_priv(indio_dev);



	iio_device_unregister(indio_dev);

	regulator_disable(st->ref);



	return 0;

}



static const struct i2c_device_id ltc2497_id[] = {

	{ "ltc2497", 0 },

	{ }

};

MODULE_DEVICE_TABLE(i2c, ltc2497_id);



static const struct of_device_id ltc2497_of_match[] = {

	{ .compatible = "lltc,ltc2497", },

	{},

};

MODULE_DEVICE_TABLE(of, ltc2497_of_match);



static struct i2c_driver ltc2497_driver = {

	.driver = {

		.name = "ltc2497",

		.of_match_table = of_match_ptr(ltc2497_of_match),

	},

	.probe = ltc2497_probe,

	.remove = ltc2497_remove,

	.id_table = ltc2497_id,

};

module_i2c_driver(ltc2497_driver);



MODULE_AUTHOR("Michael Hennerich <michael.hennerich@analog.com>");

MODULE_DESCRIPTION("Linear Technology LTC2497 ADC driver");

MODULE_LICENSE("GPL v2");