/*
   * Copyright (C) 2013 Oskar Andero <oskar.andero@gmail.com>
   *
   * Driver for Microchip Technology's MCP3204 and MCP3208 ADC chips.
   * Datasheet can be found here:
   * http://ww1.microchip.com/downloads/en/devicedoc/21298c.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>
  
  #define MCP_SINGLE_ENDED	(1 << 3)
  #define MCP_START_BIT		(1 << 4)
  
  enum {
  	mcp3204,
  	mcp3208,
  };
  
  struct mcp320x {
  	struct spi_device *spi;
  	struct spi_message msg;
  	struct spi_transfer transfer[2];
  
  	u8 tx_buf;
  	u8 rx_buf[2];
  
  	struct regulator *reg;
  	struct mutex lock;
  };
  
  static int mcp320x_adc_conversion(struct mcp320x *adc, u8 msg)
  {
  	int ret;
  
  	adc->tx_buf = msg;
  	ret = spi_sync(adc->spi, &adc->msg);
  	if (ret < 0)
  		return ret;
  
  	return ((adc->rx_buf[0] & 0x3f) << 6)  |
  		(adc->rx_buf[1] >> 2);
  }
  
  static int mcp320x_read_raw(struct iio_dev *indio_dev,
  			    struct iio_chan_spec const *channel, int *val,
  			    int *val2, long mask)
  {
  	struct mcp320x *adc = iio_priv(indio_dev);
  	int ret = -EINVAL;
  
  	mutex_lock(&adc->lock);
  
  	switch (mask) {
  	case IIO_CHAN_INFO_RAW:
  		if (channel->differential)
  			ret = mcp320x_adc_conversion(adc,
  				MCP_START_BIT | channel->address);
  		else
  			ret = mcp320x_adc_conversion(adc,
  				MCP_START_BIT | MCP_SINGLE_ENDED |
  				channel->address);
  		if (ret < 0)
  			goto out;
  
  		*val = ret;
  		ret = IIO_VAL_INT;
  		break;
  
  	case IIO_CHAN_INFO_SCALE:
  		/* Digital output code = (4096 * Vin) / Vref */
  		ret = regulator_get_voltage(adc->reg);
  		if (ret < 0)
  			goto out;
  
  		*val = ret / 1000;
  		*val2 = 12;
  		ret = IIO_VAL_FRACTIONAL_LOG2;
  		break;
  
  	default:
  		break;
  	}
  
  out:
  	mutex_unlock(&adc->lock);
  
  	return ret;
  }
  
  #define MCP320X_VOLTAGE_CHANNEL(num)				\
  	{							\
  		.type = IIO_VOLTAGE,				\
  		.indexed = 1,					\
  		.channel = (num),				\
  		.address = (num),				\
  		.info_mask_separate = BIT(IIO_CHAN_INFO_RAW),	\
  		.info_mask_shared_by_type = BIT(IIO_CHAN_INFO_SCALE) \
  	}
  
  #define MCP320X_VOLTAGE_CHANNEL_DIFF(num)			\
  	{							\
  		.type = IIO_VOLTAGE,				\
  		.indexed = 1,					\
  		.channel = (num * 2),				\
  		.channel2 = (num * 2 + 1),			\
  		.address = (num * 2),				\
  		.differential = 1,				\
  		.info_mask_separate = BIT(IIO_CHAN_INFO_RAW),	\
  		.info_mask_shared_by_type = BIT(IIO_CHAN_INFO_SCALE) \
  	}
  
  static const struct iio_chan_spec mcp3204_channels[] = {
  	MCP320X_VOLTAGE_CHANNEL(0),
  	MCP320X_VOLTAGE_CHANNEL(1),
  	MCP320X_VOLTAGE_CHANNEL(2),
  	MCP320X_VOLTAGE_CHANNEL(3),
  	MCP320X_VOLTAGE_CHANNEL_DIFF(0),
  	MCP320X_VOLTAGE_CHANNEL_DIFF(1),
  };
  
  static const struct iio_chan_spec mcp3208_channels[] = {
  	MCP320X_VOLTAGE_CHANNEL(0),
  	MCP320X_VOLTAGE_CHANNEL(1),
  	MCP320X_VOLTAGE_CHANNEL(2),
  	MCP320X_VOLTAGE_CHANNEL(3),
  	MCP320X_VOLTAGE_CHANNEL(4),
  	MCP320X_VOLTAGE_CHANNEL(5),
  	MCP320X_VOLTAGE_CHANNEL(6),
  	MCP320X_VOLTAGE_CHANNEL(7),
  	MCP320X_VOLTAGE_CHANNEL_DIFF(0),
  	MCP320X_VOLTAGE_CHANNEL_DIFF(1),
  	MCP320X_VOLTAGE_CHANNEL_DIFF(2),
  	MCP320X_VOLTAGE_CHANNEL_DIFF(3),
  };
  
  static const struct iio_info mcp320x_info = {
  	.read_raw = mcp320x_read_raw,
  	.driver_module = THIS_MODULE,
  };
  
  struct mcp3208_chip_info {
  	const struct iio_chan_spec *channels;
  	unsigned int num_channels;
  };
  
  static const struct mcp3208_chip_info mcp3208_chip_infos[] = {
  	[mcp3204] = {
  		.channels = mcp3204_channels,
  		.num_channels = ARRAY_SIZE(mcp3204_channels)
  	},
  	[mcp3208] = {
  		.channels = mcp3208_channels,
  		.num_channels = ARRAY_SIZE(mcp3208_channels)
  	},
  };
  
  static int mcp320x_probe(struct spi_device *spi)
  {
  	struct iio_dev *indio_dev;
  	struct mcp320x *adc;
  	const struct mcp3208_chip_info *chip_info;
  	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;
  
  	indio_dev->dev.parent = &spi->dev;
  	indio_dev->name = spi_get_device_id(spi)->name;
  	indio_dev->modes = INDIO_DIRECT_MODE;
  	indio_dev->info = &mcp320x_info;
  
  	chip_info = &mcp3208_chip_infos[spi_get_device_id(spi)->driver_data];
  	indio_dev->channels = chip_info->channels;
  	indio_dev->num_channels = chip_info->num_channels;
  
  	adc->transfer[0].tx_buf = &adc->tx_buf;
  	adc->transfer[0].len = sizeof(adc->tx_buf);
  	adc->transfer[1].rx_buf = adc->rx_buf;
  	adc->transfer[1].len = sizeof(adc->rx_buf);
  
  	spi_message_init_with_transfers(&adc->msg, adc->transfer,
  					ARRAY_SIZE(adc->transfer));
  
  	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);
  	if (ret < 0)
  		goto reg_disable;
  
  	return 0;
  
  reg_disable:
  	regulator_disable(adc->reg);
  
  	return ret;
  }
  
  static int mcp320x_remove(struct spi_device *spi)
  {
  	struct iio_dev *indio_dev = spi_get_drvdata(spi);
  	struct mcp320x *adc = iio_priv(indio_dev);
  
  	iio_device_unregister(indio_dev);
  	regulator_disable(adc->reg);
  
  	return 0;
  }
  
  static const struct spi_device_id mcp320x_id[] = {
  	{ "mcp3204", mcp3204 },
  	{ "mcp3208", mcp3208 },
  	{ }
  };
  MODULE_DEVICE_TABLE(spi, mcp320x_id);
  
  static struct spi_driver mcp320x_driver = {
  	.driver = {
  		.name = "mcp320x",
  		.owner = THIS_MODULE,
  	},
  	.probe = mcp320x_probe,
  	.remove = mcp320x_remove,
  	.id_table = mcp320x_id,
  };
  module_spi_driver(mcp320x_driver);
  
  MODULE_AUTHOR("Oskar Andero <oskar.andero@gmail.com>");
  MODULE_DESCRIPTION("Microchip Technology MCP3204/08");
  MODULE_LICENSE("GPL v2");