iio:adc:ad7949: Add AD7949 ADC driver family

Compatible with AD7682 and AD7689 chips.
It is a Analog Devices ADC driver 14/16 bits 4/8 channels
with SPI protocol

Datasheet of the device:
http://www.analog.com/media/en/technical-documentation/data-sheets/AD7949.pdf

Signed-off-by: Charles-Antoine Couret <charles-antoine.couret@essensium.com>
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>

drivers/iio/adc/Kconfig

@@ -116,6 +116,16 @@ config AD7923
 	  To compile this driver as a module, choose M here: the
 	  module will be called ad7923.
 
+config AD7949
+	tristate "Analog Devices AD7949 and similar ADCs driver"
+	depends on SPI
+	help
+	  Say yes here to build support for Analog Devices
+	  AD7949, AD7682, AD7689 8 Channel ADCs.
+
+	  To compile this driver as a module, choose M here: the
+	  module will be called ad7949.
+
 config AD799X
 	tristate "Analog Devices AD799x ADC driver"
 	depends on I2C

drivers/iio/adc/Makefile

@@ -14,6 +14,7 @@ obj-$(CONFIG_AD7766) += ad7766.o
 obj-$(CONFIG_AD7791) += ad7791.o
 obj-$(CONFIG_AD7793) += ad7793.o
 obj-$(CONFIG_AD7887) += ad7887.o
+obj-$(CONFIG_AD7949) += ad7949.o
 obj-$(CONFIG_AD799X) += ad799x.o
 obj-$(CONFIG_ASPEED_ADC) += aspeed_adc.o
 obj-$(CONFIG_AT91_ADC) += at91_adc.o

drivers/iio/adc/ad7949.c

@@ -0,0 +1,347 @@
+// SPDX-License-Identifier: GPL-2.0
+/* ad7949.c - Analog Devices ADC driver 14/16 bits 4/8 channels
+ *
+ * Copyright (C) 2018 CMC NV
+ *
+ * http://www.analog.com/media/en/technical-documentation/data-sheets/AD7949.pdf
+ */
+
+#include <linux/delay.h>
+#include <linux/iio/iio.h>
+#include <linux/module.h>
+#include <linux/regulator/consumer.h>
+#include <linux/spi/spi.h>
+
+#define AD7949_MASK_CHANNEL_SEL		GENMASK(9, 7)
+#define AD7949_MASK_TOTAL		GENMASK(13, 0)
+#define AD7949_OFFSET_CHANNEL_SEL	7
+#define AD7949_CFG_READ_BACK		0x1
+#define AD7949_CFG_REG_SIZE_BITS	14
+
+enum {
+	ID_AD7949 = 0,
+	ID_AD7682,
+	ID_AD7689,
+};
+
+struct ad7949_adc_spec {
+	u8 num_channels;
+	u8 resolution;
+};
+
+static const struct ad7949_adc_spec ad7949_adc_spec[] = {
+	[ID_AD7949] = { .num_channels = 8, .resolution = 14 },
+	[ID_AD7682] = { .num_channels = 4, .resolution = 16 },
+	[ID_AD7689] = { .num_channels = 8, .resolution = 16 },
+};
+
+/**
+ * struct ad7949_adc_chip - AD ADC chip
+ * @lock: protects write sequences
+ * @vref: regulator generating Vref
+ * @iio_dev: reference to iio structure
+ * @spi: reference to spi structure
+ * @resolution: resolution of the chip
+ * @cfg: copy of the configuration register
+ * @current_channel: current channel in use
+ * @buffer: buffer to send / receive data to / from device
+ */
+struct ad7949_adc_chip {
+	struct mutex lock;
+	struct regulator *vref;
+	struct iio_dev *indio_dev;
+	struct spi_device *spi;
+	u8 resolution;
+	u16 cfg;
+	unsigned int current_channel;
+	u32 buffer ____cacheline_aligned;
+};
+
+static bool ad7949_spi_cfg_is_read_back(struct ad7949_adc_chip *ad7949_adc)
+{
+	if (!(ad7949_adc->cfg & AD7949_CFG_READ_BACK))
+		return true;
+
+	return false;
+}
+
+static int ad7949_spi_bits_per_word(struct ad7949_adc_chip *ad7949_adc)
+{
+	int ret = ad7949_adc->resolution;
+
+	if (ad7949_spi_cfg_is_read_back(ad7949_adc))
+		ret += AD7949_CFG_REG_SIZE_BITS;
+
+	return ret;
+}
+
+static int ad7949_spi_write_cfg(struct ad7949_adc_chip *ad7949_adc, u16 val,
+				u16 mask)
+{
+	int ret;
+	int bits_per_word = ad7949_spi_bits_per_word(ad7949_adc);
+	int shift = bits_per_word - AD7949_CFG_REG_SIZE_BITS;
+	struct spi_message msg;
+	struct spi_transfer tx[] = {
+		{
+			.tx_buf = &ad7949_adc->buffer,
+			.len = 4,
+			.bits_per_word = bits_per_word,
+		},
+	};
+
+	ad7949_adc->cfg = (val & mask) | (ad7949_adc->cfg & ~mask);
+	ad7949_adc->buffer = ad7949_adc->cfg << shift;
+	spi_message_init_with_transfers(&msg, tx, 1);
+	ret = spi_sync(ad7949_adc->spi, &msg);
+
+	/*
+	 * This delay is to avoid a new request before the required time to
+	 * send a new command to the device
+	 */
+	udelay(2);
+	return ret;
+}
+
+static int ad7949_spi_read_channel(struct ad7949_adc_chip *ad7949_adc, int *val,
+				   unsigned int channel)
+{
+	int ret;
+	int bits_per_word = ad7949_spi_bits_per_word(ad7949_adc);
+	int mask = GENMASK(ad7949_adc->resolution, 0);
+	struct spi_message msg;
+	struct spi_transfer tx[] = {
+		{
+			.rx_buf = &ad7949_adc->buffer,
+			.len = 4,
+			.bits_per_word = bits_per_word,
+		},
+	};
+
+	ret = ad7949_spi_write_cfg(ad7949_adc,
+				   channel << AD7949_OFFSET_CHANNEL_SEL,
+				   AD7949_MASK_CHANNEL_SEL);
+	if (ret)
+		return ret;
+
+	ad7949_adc->buffer = 0;
+	spi_message_init_with_transfers(&msg, tx, 1);
+	ret = spi_sync(ad7949_adc->spi, &msg);
+	if (ret)
+		return ret;
+
+	/*
+	 * This delay is to avoid a new request before the required time to
+	 * send a new command to the device
+	 */
+	udelay(2);
+
+	ad7949_adc->current_channel = channel;
+
+	if (ad7949_spi_cfg_is_read_back(ad7949_adc))
+		*val = (ad7949_adc->buffer >> AD7949_CFG_REG_SIZE_BITS) & mask;
+	else
+		*val = ad7949_adc->buffer & mask;
+
+	return 0;
+}
+
+#define AD7949_ADC_CHANNEL(chan) {				\
+	.type = IIO_VOLTAGE,					\
+	.indexed = 1,						\
+	.channel = (chan),					\
+	.info_mask_separate = BIT(IIO_CHAN_INFO_RAW),		\
+	.info_mask_shared_by_type = BIT(IIO_CHAN_INFO_SCALE),	\
+}
+
+static const struct iio_chan_spec ad7949_adc_channels[] = {
+	AD7949_ADC_CHANNEL(0),
+	AD7949_ADC_CHANNEL(1),
+	AD7949_ADC_CHANNEL(2),
+	AD7949_ADC_CHANNEL(3),
+	AD7949_ADC_CHANNEL(4),
+	AD7949_ADC_CHANNEL(5),
+	AD7949_ADC_CHANNEL(6),
+	AD7949_ADC_CHANNEL(7),
+};
+
+static int ad7949_spi_read_raw(struct iio_dev *indio_dev,
+			   struct iio_chan_spec const *chan,
+			   int *val, int *val2, long mask)
+{
+	struct ad7949_adc_chip *ad7949_adc = iio_priv(indio_dev);
+	int ret;
+
+	if (!val)
+		return -EINVAL;
+
+	switch (mask) {
+	case IIO_CHAN_INFO_RAW:
+		mutex_lock(&ad7949_adc->lock);
+		ret = ad7949_spi_read_channel(ad7949_adc, val, chan->channel);
+		mutex_unlock(&ad7949_adc->lock);
+
+		if (ret < 0)
+			return ret;
+
+		return IIO_VAL_INT;
+
+	case IIO_CHAN_INFO_SCALE:
+		ret = regulator_get_voltage(ad7949_adc->vref);
+		if (ret < 0)
+			return ret;
+
+		*val = ret / 5000;
+		return IIO_VAL_INT;
+	}
+
+	return -EINVAL;
+}
+
+static int ad7949_spi_reg_access(struct iio_dev *indio_dev,
+			unsigned int reg, unsigned int writeval,
+			unsigned int *readval)
+{
+	struct ad7949_adc_chip *ad7949_adc = iio_priv(indio_dev);
+	int ret = 0;
+
+	if (readval)
+		*readval = ad7949_adc->cfg;
+	else
+		ret = ad7949_spi_write_cfg(ad7949_adc,
+			writeval & AD7949_MASK_TOTAL, AD7949_MASK_TOTAL);
+
+	return ret;
+}
+
+static const struct iio_info ad7949_spi_info = {
+	.read_raw = ad7949_spi_read_raw,
+	.debugfs_reg_access = ad7949_spi_reg_access,
+};
+
+static int ad7949_spi_init(struct ad7949_adc_chip *ad7949_adc)
+{
+	int ret;
+	int val;
+
+	/* Sequencer disabled, CFG readback disabled, IN0 as default channel */
+	ad7949_adc->current_channel = 0;
+	ret = ad7949_spi_write_cfg(ad7949_adc, 0x3C79, AD7949_MASK_TOTAL);
+
+	/*
+	 * Do two dummy conversions to apply the first configuration setting.
+	 * Required only after the start up of the device.
+	 */
+	ad7949_spi_read_channel(ad7949_adc, &val, ad7949_adc->current_channel);
+	ad7949_spi_read_channel(ad7949_adc, &val, ad7949_adc->current_channel);
+
+	return ret;
+}
+
+static int ad7949_spi_probe(struct spi_device *spi)
+{
+	struct device *dev = &spi->dev;
+	const struct ad7949_adc_spec *spec;
+	struct ad7949_adc_chip *ad7949_adc;
+	struct iio_dev *indio_dev;
+	int ret;
+
+	indio_dev = devm_iio_device_alloc(dev, sizeof(*ad7949_adc));
+	if (!indio_dev) {
+		dev_err(dev, "can not allocate iio device\n");
+		return -ENOMEM;
+	}
+
+	indio_dev->dev.parent = dev;
+	indio_dev->dev.of_node = dev->of_node;
+	indio_dev->info = &ad7949_spi_info;
+	indio_dev->name = spi_get_device_id(spi)->name;
+	indio_dev->modes = INDIO_DIRECT_MODE;
+	indio_dev->channels = ad7949_adc_channels;
+	spi_set_drvdata(spi, indio_dev);
+
+	ad7949_adc = iio_priv(indio_dev);
+	ad7949_adc->indio_dev = indio_dev;
+	ad7949_adc->spi = spi;
+
+	spec = &ad7949_adc_spec[spi_get_device_id(spi)->driver_data];
+	indio_dev->num_channels = spec->num_channels;
+	ad7949_adc->resolution = spec->resolution;
+
+	ad7949_adc->vref = devm_regulator_get(dev, "vref");
+	if (IS_ERR(ad7949_adc->vref)) {
+		dev_err(dev, "fail to request regulator\n");
+		return PTR_ERR(ad7949_adc->vref);
+	}
+
+	ret = regulator_enable(ad7949_adc->vref);
+	if (ret < 0) {
+		dev_err(dev, "fail to enable regulator\n");
+		return ret;
+	}
+
+	mutex_init(&ad7949_adc->lock);
+
+	ret = ad7949_spi_init(ad7949_adc);
+	if (ret) {
+		dev_err(dev, "enable to init this device: %d\n", ret);
+		goto err;
+	}
+
+	ret = iio_device_register(indio_dev);
+	if (ret) {
+		dev_err(dev, "fail to register iio device: %d\n", ret);
+		goto err;
+	}
+
+	return 0;
+
+err:
+	mutex_destroy(&ad7949_adc->lock);
+	regulator_disable(ad7949_adc->vref);
+
+	return ret;
+}
+
+static int ad7949_spi_remove(struct spi_device *spi)
+{
+	struct iio_dev *indio_dev = spi_get_drvdata(spi);
+	struct ad7949_adc_chip *ad7949_adc = iio_priv(indio_dev);
+
+	iio_device_unregister(indio_dev);
+	mutex_destroy(&ad7949_adc->lock);
+	regulator_disable(ad7949_adc->vref);
+
+	return 0;
+}
+
+static const struct of_device_id ad7949_spi_of_id[] = {
+	{ .compatible = "adi,ad7949" },
+	{ .compatible = "adi,ad7682" },
+	{ .compatible = "adi,ad7689" },
+	{ }
+};
+MODULE_DEVICE_TABLE(of, ad7949_spi_of_id);
+
+static const struct spi_device_id ad7949_spi_id[] = {
+	{ "ad7949", ID_AD7949  },
+	{ "ad7682", ID_AD7682 },
+	{ "ad7689", ID_AD7689 },
+	{ }
+};
+MODULE_DEVICE_TABLE(spi, ad7949_spi_id);
+
+static struct spi_driver ad7949_spi_driver = {
+	.driver = {
+		.name		= "ad7949",
+		.of_match_table	= ad7949_spi_of_id,
+	},
+	.probe	  = ad7949_spi_probe,
+	.remove   = ad7949_spi_remove,
+	.id_table = ad7949_spi_id,
+};
+module_spi_driver(ad7949_spi_driver);
+
+MODULE_AUTHOR("Charles-Antoine Couret <charles-antoine.couret@essensium.com>");
+MODULE_DESCRIPTION("Analog Devices 14/16-bit 8-channel ADC driver");
+MODULE_LICENSE("GPL v2");