/*
   * mcp4922.c
   *
   * Driver for Microchip Digital to Analog Converters.
   * Supports MCP4902, MCP4912, and MCP4922.
   *
   * Copyright (c) 2014 EMAC Inc.
   *
   * This program is free software; you can redistribute it and/or modify
   * it under the terms of the GNU General Public License as published by
   * the Free Software Foundation; either version 2 of the License, or
   * (at your option) any later version.
   *
   * This program is distributed in the hope that it will be useful,
   * but WITHOUT ANY WARRANTY; without even the implied warranty of
   * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
   * GNU General Public License for more details.
   *
   */
  
  #include <linux/module.h>
  #include <linux/init.h>
  #include <linux/spi/spi.h>
  #include <linux/iio/iio.h>
  #include <linux/iio/sysfs.h>
  #include <linux/regulator/consumer.h>
  #include <linux/bitops.h>
  
  #define MCP4922_NUM_CHANNELS	2
  
  enum mcp4922_supported_device_ids {
  	ID_MCP4902,
  	ID_MCP4912,
  	ID_MCP4922,
  };
  
  struct mcp4922_state {
  	struct spi_device *spi;
  	unsigned int value[MCP4922_NUM_CHANNELS];
  	unsigned int vref_mv;
  	struct regulator *vref_reg;
  	u8 mosi[2] ____cacheline_aligned;
  };
  
  #define MCP4922_CHAN(chan, bits) {			\
  	.type = IIO_VOLTAGE,				\
  	.output = 1,					\
  	.indexed = 1,					\
  	.channel = chan,				\
  	.info_mask_separate = BIT(IIO_CHAN_INFO_RAW),	\
  	.info_mask_shared_by_type = BIT(IIO_CHAN_INFO_SCALE),	\
  	.scan_type = {					\
  		.sign = 'u',				\
  		.realbits = (bits),			\
  		.storagebits = 16,			\
  		.shift = 12 - (bits),			\
  	},						\
  }
  
  static int mcp4922_spi_write(struct mcp4922_state *state, u8 addr, u32 val)
  {
  	state->mosi[1] = val & 0xff;
  	state->mosi[0] = (addr == 0) ? 0x00 : 0x80;
  	state->mosi[0] |= 0x30 | ((val >> 8) & 0x0f);
  
  	return spi_write(state->spi, state->mosi, 2);
  }
  
  static int mcp4922_read_raw(struct iio_dev *indio_dev,
  		struct iio_chan_spec const *chan,
  		int *val,
  		int *val2,
  		long mask)
  {
  	struct mcp4922_state *state = iio_priv(indio_dev);
  
  	switch (mask) {
  	case IIO_CHAN_INFO_RAW:
  		*val = state->value[chan->channel];
  		return IIO_VAL_INT;
  	case IIO_CHAN_INFO_SCALE:
  		*val = state->vref_mv;
  		*val2 = chan->scan_type.realbits;
  		return IIO_VAL_FRACTIONAL_LOG2;
  	default:
  		return -EINVAL;
  	}
  }
  
  static int mcp4922_write_raw(struct iio_dev *indio_dev,
  		struct iio_chan_spec const *chan,
  		int val,
  		int val2,
  		long mask)
  {
  	struct mcp4922_state *state = iio_priv(indio_dev);
  
  	if (val2 != 0)
  		return -EINVAL;
  
  	switch (mask) {
  	case IIO_CHAN_INFO_RAW:
  		if (val > GENMASK(chan->scan_type.realbits-1, 0))
  			return -EINVAL;
  		val <<= chan->scan_type.shift;
  		state->value[chan->channel] = val;
  		return mcp4922_spi_write(state, chan->channel, val);
  	default:
  		return -EINVAL;
  	}
  }
  
  static const struct iio_chan_spec mcp4922_channels[3][MCP4922_NUM_CHANNELS] = {
  	[ID_MCP4902] = { MCP4922_CHAN(0, 8),	MCP4922_CHAN(1, 8) },
  	[ID_MCP4912] = { MCP4922_CHAN(0, 10),	MCP4922_CHAN(1, 10) },
  	[ID_MCP4922] = { MCP4922_CHAN(0, 12),	MCP4922_CHAN(1, 12) },
  };
  
  static const struct iio_info mcp4922_info = {
  	.read_raw = &mcp4922_read_raw,
  	.write_raw = &mcp4922_write_raw,
  	.driver_module = THIS_MODULE,
  };
  
  static int mcp4922_probe(struct spi_device *spi)
  {
  	struct iio_dev *indio_dev;
  	struct mcp4922_state *state;
  	const struct spi_device_id *id;
  	int ret;
  
  	indio_dev = devm_iio_device_alloc(&spi->dev, sizeof(*state));
  	if (indio_dev == NULL)
  		return -ENOMEM;
  
  	state = iio_priv(indio_dev);
  	state->spi = spi;
  	state->vref_reg = devm_regulator_get(&spi->dev, "vref");
  	if (IS_ERR(state->vref_reg)) {
  		dev_err(&spi->dev, "Vref regulator not specified
  ");
  		return PTR_ERR(state->vref_reg);
  	}
  
  	ret = regulator_enable(state->vref_reg);
  	if (ret) {
  		dev_err(&spi->dev, "Failed to enable vref regulator: %d
  ",
  				ret);
  		return ret;
  	}
  
  	ret = regulator_get_voltage(state->vref_reg);
  	if (ret < 0) {
  		dev_err(&spi->dev, "Failed to read vref regulator: %d
  ",
  				ret);
  		goto error_disable_reg;
  	}
  	state->vref_mv = ret / 1000;
  
  	spi_set_drvdata(spi, indio_dev);
  	id = spi_get_device_id(spi);
  	indio_dev->dev.parent = &spi->dev;
  	indio_dev->info = &mcp4922_info;
  	indio_dev->modes = INDIO_DIRECT_MODE;
  	indio_dev->channels = mcp4922_channels[id->driver_data];
  	indio_dev->num_channels = MCP4922_NUM_CHANNELS;
  	indio_dev->name = id->name;
  
  	ret = iio_device_register(indio_dev);
  	if (ret) {
  		dev_err(&spi->dev, "Failed to register iio device: %d
  ",
  				ret);
  		goto error_disable_reg;
  	}
  
  	return 0;
  
  error_disable_reg:
  	regulator_disable(state->vref_reg);
  
  	return ret;
  }
  
  static int mcp4922_remove(struct spi_device *spi)
  {
  	struct iio_dev *indio_dev = spi_get_drvdata(spi);
  	struct mcp4922_state *state;
  
  	iio_device_unregister(indio_dev);
  	state = iio_priv(indio_dev);
  	regulator_disable(state->vref_reg);
  
  	return 0;
  }
  
  static const struct spi_device_id mcp4922_id[] = {
  	{"mcp4902", ID_MCP4902},
  	{"mcp4912", ID_MCP4912},
  	{"mcp4922", ID_MCP4922},
  	{}
  };
  MODULE_DEVICE_TABLE(spi, mcp4922_id);
  
  static struct spi_driver mcp4922_driver = {
  	.driver = {
  		   .name = "mcp4922",
  		   },
  	.probe = mcp4922_probe,
  	.remove = mcp4922_remove,
  	.id_table = mcp4922_id,
  };
  module_spi_driver(mcp4922_driver);
  
  MODULE_AUTHOR("Michael Welling <mwelling@ieee.org>");
  MODULE_DESCRIPTION("Microchip MCP4902, MCP4912, MCP4922 DAC");
  MODULE_LICENSE("GPL v2");