iio: dac: AD8801: add Analog Devices AD8801/AD8803 support

Add support for Analog Devices AD8801/AD8803, 8 channels 8bits, Digital to
Analog converters.

Signed-off-by: Gwenhael Goavec-Merou <[e-mail]>
Signed-off-by: Jonathan Cameron <[e-mail]>

drivers/iio/dac/Kconfig

···
 	  base port addresses for the devices may be configured via the base
 	  array module parameter.
 
+config AD8801
+	tristate "Analog Devices AD8801/AD8803 DAC driver"
+	depends on SPI_MASTER
+	help
+	  Say yes here to build support for Analog Devices AD8801, AD8803 Digital to
+	  Analog Converters (DAC).
+
+	  To compile this driver as a module choose M here: the module will be called
+	  ad8801.
+
 config LPC18XX_DAC
 	tristate "NXP LPC18xx DAC driver"
 	depends on ARCH_LPC18XX || COMPILE_TEST

drivers/iio/dac/Makefile

···
 obj-$(CONFIG_AD5791) += ad5791.o
 obj-$(CONFIG_AD5686) += ad5686.o
 obj-$(CONFIG_AD7303) += ad7303.o
+obj-$(CONFIG_AD8801) += ad8801.o
 obj-$(CONFIG_CIO_DAC) += cio-dac.o
 obj-$(CONFIG_LPC18XX_DAC) += lpc18xx_dac.o
 obj-$(CONFIG_M62332) += m62332.o

drivers/iio/dac/ad8801.c

···
+/*
+ * IIO DAC driver for Analog Devices AD8801 DAC
+ *
+ * Copyright (C) 2016 Gwenhael Goavec-Merou
+ * 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.
+ *
+ * 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/iio/iio.h>
+#include <linux/module.h>
+#include <linux/regulator/consumer.h>
+#include <linux/spi/spi.h>
+#include <linux/sysfs.h>
+
+#define AD8801_CFG_ADDR_OFFSET 8
+
+enum ad8801_device_ids {
+	ID_AD8801,
+	ID_AD8803,
+};
+
+struct ad8801_state {
+	struct spi_device *spi;
+	unsigned char dac_cache[8]; /* Value write on each channel */
+	unsigned int vrefh_mv;
+	unsigned int vrefl_mv;
+	struct regulator *vrefh_reg;
+	struct regulator *vrefl_reg;
+
+	__be16 data ____cacheline_aligned;
+};
+
+static int ad8801_spi_write(struct ad8801_state *state,
+	u8 channel, unsigned char value)
+{
+	state->data = cpu_to_be16((channel << AD8801_CFG_ADDR_OFFSET) | value);
+	return spi_write(state->spi, &state->data, sizeof(state->data));
+}
+
+static int ad8801_write_raw(struct iio_dev *indio_dev,
+	struct iio_chan_spec const *chan, int val, int val2, long mask)
+{
+	struct ad8801_state *state = iio_priv(indio_dev);
+	int ret;
+
+	switch (mask) {
+	case IIO_CHAN_INFO_RAW:
+		if (val >= 256 || val < 0)
+			return -EINVAL;
+
+		ret = ad8801_spi_write(state, chan->channel, val);
+		if (ret == 0)
+			state->dac_cache[chan->channel] = val;
+		break;
+	default:
+		ret = -EINVAL;
+	}
+
+	return ret;
+}
+
+static int ad8801_read_raw(struct iio_dev *indio_dev,
+	struct iio_chan_spec const *chan, int *val, int *val2, long info)
+{
+	struct ad8801_state *state = iio_priv(indio_dev);
+
+	switch (info) {
+	case IIO_CHAN_INFO_RAW:
+		*val = state->dac_cache[chan->channel];
+		return IIO_VAL_INT;
+	case IIO_CHAN_INFO_SCALE:
+		*val = state->vrefh_mv - state->vrefl_mv;
+		*val2 = 8;
+		return IIO_VAL_FRACTIONAL_LOG2;
+	case IIO_CHAN_INFO_OFFSET:
+		*val = state->vrefl_mv;
+		return IIO_VAL_INT;
+	default:
+		return -EINVAL;
+	}
+
+	return -EINVAL;
+}
+
+static const struct iio_info ad8801_info = {
+	.read_raw = ad8801_read_raw,
+	.write_raw = ad8801_write_raw,
+	.driver_module = THIS_MODULE,
+};
+
+#define AD8801_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) |	\
+		BIT(IIO_CHAN_INFO_OFFSET), \
+}
+
+static const struct iio_chan_spec ad8801_channels[] = {
+	AD8801_CHANNEL(0),
+	AD8801_CHANNEL(1),
+	AD8801_CHANNEL(2),
+	AD8801_CHANNEL(3),
+	AD8801_CHANNEL(4),
+	AD8801_CHANNEL(5),
+	AD8801_CHANNEL(6),
+	AD8801_CHANNEL(7),
+};
+
+static int ad8801_probe(struct spi_device *spi)
+{
+	struct iio_dev *indio_dev;
+	struct ad8801_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;
+	id = spi_get_device_id(spi);
+
+	state->vrefh_reg = devm_regulator_get(&spi->dev, "vrefh");
+	if (IS_ERR(state->vrefh_reg)) {
+		dev_err(&spi->dev, "Vrefh regulator not specified\n");
+		return PTR_ERR(state->vrefh_reg);
+	}
+
+	ret = regulator_enable(state->vrefh_reg);
+	if (ret) {
+		dev_err(&spi->dev, "Failed to enable vrefh regulator: %d\n",
+				ret);
+		return ret;
+	}
+
+	ret = regulator_get_voltage(state->vrefh_reg);
+	if (ret < 0) {
+		dev_err(&spi->dev, "Failed to read vrefh regulator: %d\n",
+				ret);
+		goto error_disable_vrefh_reg;
+	}
+	state->vrefh_mv = ret / 1000;
+
+	if (id->driver_data == ID_AD8803) {
+		state->vrefl_reg = devm_regulator_get(&spi->dev, "vrefl");
+		if (IS_ERR(state->vrefl_reg)) {
+			dev_err(&spi->dev, "Vrefl regulator not specified\n");
+			ret = PTR_ERR(state->vrefl_reg);
+			goto error_disable_vrefh_reg;
+		}
+
+		ret = regulator_enable(state->vrefl_reg);
+		if (ret) {
+			dev_err(&spi->dev, "Failed to enable vrefl regulator: %d\n",
+					ret);
+			goto error_disable_vrefh_reg;
+		}
+
+		ret = regulator_get_voltage(state->vrefl_reg);
+		if (ret < 0) {
+			dev_err(&spi->dev, "Failed to read vrefl regulator: %d\n",
+					ret);
+			goto error_disable_vrefl_reg;
+		}
+		state->vrefl_mv = ret / 1000;
+	} else {
+		state->vrefl_mv = 0;
+		state->vrefl_reg = NULL;
+	}
+
+	spi_set_drvdata(spi, indio_dev);
+	indio_dev->dev.parent = &spi->dev;
+	indio_dev->info = &ad8801_info;
+	indio_dev->modes = INDIO_DIRECT_MODE;
+	indio_dev->channels = ad8801_channels;
+	indio_dev->num_channels = ARRAY_SIZE(ad8801_channels);
+	indio_dev->name = id->name;
+
+	ret = iio_device_register(indio_dev);
+	if (ret) {
+		dev_err(&spi->dev, "Failed to register iio device: %d\n",
+				ret);
+		goto error_disable_vrefl_reg;
+	}
+
+	return 0;
+
+error_disable_vrefl_reg:
+	if (state->vrefl_reg)
+		regulator_disable(state->vrefl_reg);
+error_disable_vrefh_reg:
+	regulator_disable(state->vrefh_reg);
+	return ret;
+}
+
+static int ad8801_remove(struct spi_device *spi)
+{
+	struct iio_dev *indio_dev = spi_get_drvdata(spi);
+	struct ad8801_state *state = iio_priv(indio_dev);
+
+	iio_device_unregister(indio_dev);
+	if (state->vrefl_reg)
+		regulator_disable(state->vrefl_reg);
+	regulator_disable(state->vrefh_reg);
+
+	return 0;
+}
+
+static const struct spi_device_id ad8801_ids[] = {
+	{"ad8801", ID_AD8801},
+	{"ad8803", ID_AD8803},
+	{}
+};
+MODULE_DEVICE_TABLE(spi, ad8801_ids);
+
+static struct spi_driver ad8801_driver = {
+	.driver = {
+		.name	= "ad8801",
+	},
+	.probe		= ad8801_probe,
+	.remove		= ad8801_remove,
+	.id_table	= ad8801_ids,
+};
+module_spi_driver(ad8801_driver);
+
+MODULE_AUTHOR("Gwenhael Goavec-Merou <[e-mail]>");
+MODULE_DESCRIPTION("Analog Devices AD8801/AD8803 DAC");
+MODULE_LICENSE("GPL v2");