/*
 * Copyright (C) 2014 Angelo Compagnucci <angelo.compagnucci@gmail.com>
 *
 * Driver for Texas Instruments' ADC128S052 ADC chip.
 * Datasheet can be found here:
 * http://www.ti.com/lit/ds/symlink/adc128s052.pdf
 *
 * 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.
 */

#include <linux/err.h>
#include <linux/spi/spi.h>
#include <linux/module.h>
#include <linux/iio/iio.h>
#include <linux/regulator/consumer.h>

struct adc128 {
	struct spi_device *spi;

	struct regulator *reg;
	struct mutex lock;

	u8 buffer[2] ____cacheline_aligned;
};

static int adc128_adc_conversion(struct adc128 *adc, u8 channel)
{
	int ret;

	mutex_lock(&adc->lock);

	adc->buffer[0] = channel << 3;
	adc->buffer[1] = 0;

	ret = spi_write(adc->spi, &adc->buffer, 2);
	if (ret < 0) {
		mutex_unlock(&adc->lock);
		return ret;
	}

	ret = spi_read(adc->spi, &adc->buffer, 2);

	mutex_unlock(&adc->lock);

	if (ret < 0)
		return ret;

	return ((adc->buffer[0] << 8 | adc->buffer[1]) & 0xFFF);
}

static int adc128_read_raw(struct iio_dev *indio_dev,
			   struct iio_chan_spec const *channel, int *val,
			   int *val2, long mask)
{
	struct adc128 *adc = iio_priv(indio_dev);
	int ret;

	switch (mask) {
	case IIO_CHAN_INFO_RAW:

		ret = adc128_adc_conversion(adc, channel->channel);
		if (ret < 0)
			return ret;

		*val = ret;
		return IIO_VAL_INT;

	case IIO_CHAN_INFO_SCALE:

		ret = regulator_get_voltage(adc->reg);
		if (ret < 0)
			return ret;

		*val = ret / 1000;
		*val2 = 12;
		return IIO_VAL_FRACTIONAL_LOG2;

	default:
		return -EINVAL;
	}

}

#define ADC128_VOLTAGE_CHANNEL(num)	\
	{ \
		.type = IIO_VOLTAGE, \
		.indexed = 1, \
		.channel = (num), \
		.info_mask_separate = BIT(IIO_CHAN_INFO_RAW), \
		.info_mask_shared_by_type = BIT(IIO_CHAN_INFO_SCALE) \
	}

static const struct iio_chan_spec adc128_channels[] = {
	ADC128_VOLTAGE_CHANNEL(0),
	ADC128_VOLTAGE_CHANNEL(1),
	ADC128_VOLTAGE_CHANNEL(2),
	ADC128_VOLTAGE_CHANNEL(3),
	ADC128_VOLTAGE_CHANNEL(4),
	ADC128_VOLTAGE_CHANNEL(5),
	ADC128_VOLTAGE_CHANNEL(6),
	ADC128_VOLTAGE_CHANNEL(7),
};

static const struct iio_info adc128_info = {
	.read_raw = adc128_read_raw,
	.driver_module = THIS_MODULE,
};

static int adc128_probe(struct spi_device *spi)
{
	struct iio_dev *indio_dev;
	struct adc128 *adc;
	int ret;

	indio_dev = devm_iio_device_alloc(&spi->dev, sizeof(*adc));
	if (!indio_dev)
		return -ENOMEM;

	adc = iio_priv(indio_dev);
	adc->spi = spi;

	spi_set_drvdata(spi, indio_dev);

	indio_dev->dev.parent = &spi->dev;
	indio_dev->name = spi_get_device_id(spi)->name;
	indio_dev->modes = INDIO_DIRECT_MODE;
	indio_dev->info = &adc128_info;

	indio_dev->channels = adc128_channels;
	indio_dev->num_channels = ARRAY_SIZE(adc128_channels);

	adc->reg = devm_regulator_get(&spi->dev, "vref");
	if (IS_ERR(adc->reg))
		return PTR_ERR(adc->reg);

	ret = regulator_enable(adc->reg);
	if (ret < 0)
		return ret;

	mutex_init(&adc->lock);

	ret = iio_device_register(indio_dev);

	return ret;
}

static int adc128_remove(struct spi_device *spi)
{
	struct iio_dev *indio_dev = spi_get_drvdata(spi);
	struct adc128 *adc = iio_priv(indio_dev);

	iio_device_unregister(indio_dev);
	regulator_disable(adc->reg);

	return 0;
}

static const struct spi_device_id adc128_id[] = {
	{ "adc128s052", 0},
	{ }
};
MODULE_DEVICE_TABLE(spi, adc128_id);

static struct spi_driver adc128_driver = {
	.driver = {
		.name = "adc128s052",
		.owner = THIS_MODULE,
	},
	.probe = adc128_probe,
	.remove = adc128_remove,
	.id_table = adc128_id,
};
module_spi_driver(adc128_driver);

MODULE_AUTHOR("Angelo Compagnucci <angelo.compagnucci@gmail.com>");
MODULE_DESCRIPTION("Texas Instruments ADC128S052");
MODULE_LICENSE("GPL v2");