/*
   * AD7303 Digital to analog converters driver
   *
   * Copyright 2013 Analog Devices Inc.
   *
   * Licensed under the GPL-2.
   */
  
  #include <linux/err.h>
  #include <linux/module.h>
  #include <linux/kernel.h>
  #include <linux/spi/spi.h>
  #include <linux/slab.h>
  #include <linux/sysfs.h>
  #include <linux/regulator/consumer.h>
  #include <linux/of.h>
  
  #include <linux/iio/iio.h>
  #include <linux/iio/sysfs.h>
  
  #include <linux/platform_data/ad7303.h>
  
  #define AD7303_CFG_EXTERNAL_VREF BIT(15)
  #define AD7303_CFG_POWER_DOWN(ch) BIT(11 + (ch))
  #define AD7303_CFG_ADDR_OFFSET	10
  
  #define AD7303_CMD_UPDATE_DAC	(0x3 << 8)
  
  /**
   * struct ad7303_state - driver instance specific data
   * @spi:		the device for this driver instance
   * @config:		cached config register value
   * @dac_cache:		current DAC raw value (chip does not support readback)
   * @data:		spi transfer buffer
   */
  
  struct ad7303_state {
  	struct spi_device *spi;
  	uint16_t config;
  	uint8_t dac_cache[2];
  
  	struct regulator *vdd_reg;
  	struct regulator *vref_reg;
  
  	/*
  	 * DMA (thus cache coherency maintenance) requires the
  	 * transfer buffers to live in their own cache lines.
  	 */
  	__be16 data ____cacheline_aligned;
  };
  
  static int ad7303_write(struct ad7303_state *st, unsigned int chan,
  	uint8_t val)
  {
  	st->data = cpu_to_be16(AD7303_CMD_UPDATE_DAC |
  		(chan << AD7303_CFG_ADDR_OFFSET) |
  		st->config | val);
  
  	return spi_write(st->spi, &st->data, sizeof(st->data));
  }
  
  static ssize_t ad7303_read_dac_powerdown(struct iio_dev *indio_dev,
  	uintptr_t private, const struct iio_chan_spec *chan, char *buf)
  {
  	struct ad7303_state *st = iio_priv(indio_dev);
  
  	return sprintf(buf, "%d
  ", (bool)(st->config &
  		AD7303_CFG_POWER_DOWN(chan->channel)));
  }
  
  static ssize_t ad7303_write_dac_powerdown(struct iio_dev *indio_dev,
  	 uintptr_t private, const struct iio_chan_spec *chan, const char *buf,
  	 size_t len)
  {
  	struct ad7303_state *st = iio_priv(indio_dev);
  	bool pwr_down;
  	int ret;
  
  	ret = strtobool(buf, &pwr_down);
  	if (ret)
  		return ret;
  
  	mutex_lock(&indio_dev->mlock);
  
  	if (pwr_down)
  		st->config |= AD7303_CFG_POWER_DOWN(chan->channel);
  	else
  		st->config &= ~AD7303_CFG_POWER_DOWN(chan->channel);
  
  	/* There is no noop cmd which allows us to only update the powerdown
  	 * mode, so just write one of the DAC channels again */
  	ad7303_write(st, chan->channel, st->dac_cache[chan->channel]);
  
  	mutex_unlock(&indio_dev->mlock);
  	return ret ? ret : len;
  }
  
  static int ad7303_get_vref(struct ad7303_state *st,
  	struct iio_chan_spec const *chan)
  {
  	int ret;
  
  	if (st->config & AD7303_CFG_EXTERNAL_VREF)
  		return regulator_get_voltage(st->vref_reg);
  
  	ret = regulator_get_voltage(st->vdd_reg);
  	if (ret < 0)
  		return ret;
  	return ret / 2;
  }
  
  static int ad7303_read_raw(struct iio_dev *indio_dev,
  	struct iio_chan_spec const *chan, int *val, int *val2, long info)
  {
  	struct ad7303_state *st = iio_priv(indio_dev);
  	int vref_uv;
  
  	switch (info) {
  	case IIO_CHAN_INFO_RAW:
  		*val = st->dac_cache[chan->channel];
  		return IIO_VAL_INT;
  	case IIO_CHAN_INFO_SCALE:
  		vref_uv = ad7303_get_vref(st, chan);
  		if (vref_uv < 0)
  			return vref_uv;
  
  		*val = 2 * vref_uv / 1000;
  		*val2 = chan->scan_type.realbits;
  
  		return IIO_VAL_FRACTIONAL_LOG2;
  	default:
  		break;
  	}
  	return -EINVAL;
  }
  
  static int ad7303_write_raw(struct iio_dev *indio_dev,
  	struct iio_chan_spec const *chan, int val, int val2, long mask)
  {
  	struct ad7303_state *st = iio_priv(indio_dev);
  	int ret;
  
  	switch (mask) {
  	case IIO_CHAN_INFO_RAW:
  		if (val >= (1 << chan->scan_type.realbits) || val < 0)
  			return -EINVAL;
  
  		mutex_lock(&indio_dev->mlock);
  		ret = ad7303_write(st, chan->address, val);
  		if (ret == 0)
  			st->dac_cache[chan->channel] = val;
  		mutex_unlock(&indio_dev->mlock);
  		break;
  	default:
  		ret = -EINVAL;
  	}
  
  	return ret;
  }
  
  static const struct iio_info ad7303_info = {
  	.read_raw = ad7303_read_raw,
  	.write_raw = ad7303_write_raw,
  	.driver_module = THIS_MODULE,
  };
  
  static const struct iio_chan_spec_ext_info ad7303_ext_info[] = {
  	{
  		.name = "powerdown",
  		.read = ad7303_read_dac_powerdown,
  		.write = ad7303_write_dac_powerdown,
  		.shared = IIO_SEPARATE,
  	},
  	{ },
  };
  
  #define AD7303_CHANNEL(chan) {					\
  	.type = IIO_VOLTAGE,					\
  	.indexed = 1,						\
  	.output = 1,						\
  	.channel = (chan),					\
  	.info_mask_separate = BIT(IIO_CHAN_INFO_RAW),		\
  	.info_mask_shared_by_type = BIT(IIO_CHAN_INFO_SCALE),	\
  	.address = (chan),					\
  	.scan_type = {						\
  		.sign = 'u',					\
  		.realbits = '8',				\
  		.storagebits = '8',				\
  		.shift = '0',					\
  	},							\
  	.ext_info = ad7303_ext_info,				\
  }
  
  static const struct iio_chan_spec ad7303_channels[] = {
  	AD7303_CHANNEL(0),
  	AD7303_CHANNEL(1),
  };
  
  static int ad7303_probe(struct spi_device *spi)
  {
  	const struct spi_device_id *id = spi_get_device_id(spi);
  	struct iio_dev *indio_dev;
  	struct ad7303_state *st;
  	bool ext_ref;
  	int ret;
  
  	indio_dev = devm_iio_device_alloc(&spi->dev, sizeof(*st));
  	if (indio_dev == NULL)
  		return -ENOMEM;
  
  	st = iio_priv(indio_dev);
  	spi_set_drvdata(spi, indio_dev);
  
  	st->spi = spi;
  
  	st->vdd_reg = devm_regulator_get(&spi->dev, "Vdd");
  	if (IS_ERR(st->vdd_reg))
  		return PTR_ERR(st->vdd_reg);
  
  	ret = regulator_enable(st->vdd_reg);
  	if (ret)
  		return ret;
  
  	if (spi->dev.of_node) {
  		ext_ref = of_property_read_bool(spi->dev.of_node,
  				"REF-supply");
  	} else {
  		struct ad7303_platform_data *pdata = spi->dev.platform_data;
  		if (pdata && pdata->use_external_ref)
  			ext_ref = true;
  		else
  		    ext_ref = false;
  	}
  
  	if (ext_ref) {
  		st->vref_reg = devm_regulator_get(&spi->dev, "REF");
  		if (IS_ERR(st->vref_reg)) {
  			ret = PTR_ERR(st->vref_reg);
  			goto err_disable_vdd_reg;
  		}
  
  		ret = regulator_enable(st->vref_reg);
  		if (ret)
  			goto err_disable_vdd_reg;
  
  		st->config |= AD7303_CFG_EXTERNAL_VREF;
  	}
  
  	indio_dev->dev.parent = &spi->dev;
  	indio_dev->name = id->name;
  	indio_dev->info = &ad7303_info;
  	indio_dev->modes = INDIO_DIRECT_MODE;
  	indio_dev->channels = ad7303_channels;
  	indio_dev->num_channels = ARRAY_SIZE(ad7303_channels);
  
  	ret = iio_device_register(indio_dev);
  	if (ret)
  		goto err_disable_vref_reg;
  
  	return 0;
  
  err_disable_vref_reg:
  	if (st->vref_reg)
  		regulator_disable(st->vref_reg);
  err_disable_vdd_reg:
  	regulator_disable(st->vdd_reg);
  	return ret;
  }
  
  static int ad7303_remove(struct spi_device *spi)
  {
  	struct iio_dev *indio_dev = spi_get_drvdata(spi);
  	struct ad7303_state *st = iio_priv(indio_dev);
  
  	iio_device_unregister(indio_dev);
  
  	if (st->vref_reg)
  		regulator_disable(st->vref_reg);
  	regulator_disable(st->vdd_reg);
  
  	return 0;
  }
  
  static const struct spi_device_id ad7303_spi_ids[] = {
  	{ "ad7303", 0 },
  	{}
  };
  MODULE_DEVICE_TABLE(spi, ad7303_spi_ids);
  
  static struct spi_driver ad7303_driver = {
  	.driver = {
  		.name = "ad7303",
  		.owner = THIS_MODULE,
  	},
  	.probe = ad7303_probe,
  	.remove = ad7303_remove,
  	.id_table = ad7303_spi_ids,
  };
  module_spi_driver(ad7303_driver);
  
  MODULE_AUTHOR("Lars-Peter Clausen <lars@metafoo.de>");
  MODULE_DESCRIPTION("Analog Devices AD7303 DAC driver");
  MODULE_LICENSE("GPL v2");