[PATCH v3 2/2] iio: dac: ad5706r: Add support for AD5706R DAC

[Alexis Czezar Torreno <alexisczezar.torreno@analog.com>]

Add support for the Analog Devices AD5706R, a 4-channel 16-bit
current output digital-to-analog converter with SPI interface.

Features:
  - 4 independent DAC channels
  - Hardware and software LDAC trigger
  - Configurable output range
  - PWM-based LDAC control
  - Dither and toggle modes
  - Dynamically configurable SPI speed

Signed-off-by: Alexis Czezar Torreno <alexisczezar.torreno@analog.com>

---
Changes since v1:
  - Removed PWM, GPIO, clock generator, debugfs, regmap, IIO_BUFFER
  - Removed all custom ext_info sysfs attributes
  - Simplified to basic raw read/write and read-only scale
  - SPI read/write can handle multibyte registers
---
---
 MAINTAINERS               |   1 +
 drivers/iio/dac/Kconfig   |  10 +++
 drivers/iio/dac/Makefile  |   1 +
 drivers/iio/dac/ad5706r.c | 222 ++++++++++++++++++++++++++++++++++++++++++++++
 4 files changed, 234 insertions(+)

diff --git a/MAINTAINERS b/MAINTAINERS
index 17a3d2d45fccb9cd3c93fd35666fb85d17d53cde..3d7bd98b4d1b55836e40687a9a3ac9f4935a8acb 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -1502,6 +1502,7 @@ L:	linux-iio@vger.kernel.org
 S:	Supported
 W:	https://ez.analog.com/linux-software-drivers
 F:	Documentation/devicetree/bindings/iio/dac/adi,ad5706r.yaml
+F:	drivers/iio/dac/ad5706r.c
 
 ANALOG DEVICES INC AD7091R DRIVER
 M:	Marcelo Schmitt <marcelo.schmitt@analog.com>
diff --git a/drivers/iio/dac/Kconfig b/drivers/iio/dac/Kconfig
index db9f5c711b3df90641f017652fbbef594cc1627d..8ccbdf6dfbca8640a47bf05b4afc6b4bf90a7e26 100644
--- a/drivers/iio/dac/Kconfig
+++ b/drivers/iio/dac/Kconfig
@@ -178,6 +178,16 @@ config AD5624R_SPI
 	  Say yes here to build support for Analog Devices AD5624R, AD5644R and
 	  AD5664R converters (DAC). This driver uses the common SPI interface.
 
+config AD5706R
+	tristate "Analog Devices AD5706R DAC driver"
+	depends on SPI
+	help
+	  Say yes here to build support for Analog Devices AD5706R 4-channel,
+	  16-bit current output DAC.
+
+	  To compile this driver as a module, choose M here: the
+	  module will be called ad5706r.
+
 config AD9739A
 	tristate "Analog Devices AD9739A RF DAC spi driver"
 	depends on SPI
diff --git a/drivers/iio/dac/Makefile b/drivers/iio/dac/Makefile
index 2a80bbf4e80ad557da79ed916027cedff286984b..0034317984985035f7987a744899924bfd4612e3 100644
--- a/drivers/iio/dac/Makefile
+++ b/drivers/iio/dac/Makefile
@@ -21,6 +21,7 @@ obj-$(CONFIG_AD5449) += ad5449.o
 obj-$(CONFIG_AD5592R_BASE) += ad5592r-base.o
 obj-$(CONFIG_AD5592R) += ad5592r.o
 obj-$(CONFIG_AD5593R) += ad5593r.o
+obj-$(CONFIG_AD5706R) += ad5706r.o
 obj-$(CONFIG_AD5755) += ad5755.o
 obj-$(CONFIG_AD5758) += ad5758.o
 obj-$(CONFIG_AD5761) += ad5761.o
diff --git a/drivers/iio/dac/ad5706r.c b/drivers/iio/dac/ad5706r.c
new file mode 100644
index 0000000000000000000000000000000000000000..840ee7b6db2e05ea35b27ff776f0c5c8a961d9c1
--- /dev/null
+++ b/drivers/iio/dac/ad5706r.c
@@ -0,0 +1,222 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * AD5706R 16-bit Current Output Digital to Analog Converter
+ *
+ * Copyright 2026 Analog Devices Inc.
+ */
+
+#include <linux/array_size.h>
+#include <linux/bits.h>
+#include <linux/cleanup.h>
+#include <linux/iio/iio.h>
+#include <linux/module.h>
+#include <linux/mutex.h>
+#include <linux/spi/spi.h>
+#include <linux/unaligned.h>
+
+/* SPI frame layout */
+#define AD5706R_RD_MASK			BIT(15)
+#define AD5706R_ADDR_MASK		GENMASK(11, 0)
+
+/* Registers */
+#define AD5706R_REG_DAC_INPUT_A_CH(x)		(0x60 + ((x) * 2))
+#define AD5706R_REG_DAC_DATA_READBACK_CH(x)	(0x68 + ((x) * 2))
+
+#define AD5706R_DAC_RESOLUTION		16
+#define AD5706R_DAC_MAX_CODE		BIT(16)
+#define AD5706R_MULTIBYTE_REG_START	0x14
+#define AD5706R_MULTIBYTE_REG_END	0x71
+#define AD5706R_SINGLE_BYTE_LEN		1
+#define AD5706R_DOUBLE_BYTE_LEN		2
+
+struct ad5706r_state {
+	struct spi_device *spi;
+	struct mutex lock; /* Protects SPI transfers */
+
+	u8 tx_buf[4] __aligned(ARCH_DMA_MINALIGN);
+	u8 rx_buf[2];
+};
+
+static int ad5706r_reg_len(unsigned int reg)
+{
+	if (reg >= AD5706R_MULTIBYTE_REG_START && reg <= AD5706R_MULTIBYTE_REG_END)
+		return AD5706R_DOUBLE_BYTE_LEN;
+
+	return AD5706R_SINGLE_BYTE_LEN;
+}
+
+static int ad5706r_spi_write(struct ad5706r_state *st, u16 reg, u16 val)
+{
+	unsigned int num_bytes = ad5706r_reg_len(reg);
+	struct spi_transfer xfer = {
+		.tx_buf = st->tx_buf,
+		.len = num_bytes + 2,
+	};
+
+	put_unaligned_be16(reg, &st->tx_buf[0]);
+
+	if (num_bytes == 1)
+		st->tx_buf[2] = val;
+	else if (num_bytes == 2)
+		put_unaligned_be16(val, &st->tx_buf[2]);
+	else
+		return -EINVAL;
+
+	return spi_sync_transfer(st->spi, &xfer, 1);
+}
+
+static int ad5706r_spi_read(struct ad5706r_state *st, u16 reg, u16 *val)
+{
+	unsigned int num_bytes = ad5706r_reg_len(reg);
+	u16 cmd;
+	int ret;
+
+	struct spi_transfer xfer[] = {
+		{
+			.tx_buf = st->tx_buf,
+			.len = 2,
+		},
+		{
+			.rx_buf = st->rx_buf,
+			.len = num_bytes,
+		},
+	};
+
+	cmd = AD5706R_RD_MASK | (reg & AD5706R_ADDR_MASK);
+	put_unaligned_be16(cmd, &st->tx_buf[0]);
+
+	ret = spi_sync_transfer(st->spi, xfer, ARRAY_SIZE(xfer));
+	if (ret)
+		return ret;
+
+	if (num_bytes == 1)
+		*val = st->rx_buf[0];
+	else if (num_bytes == 2)
+		*val = get_unaligned_be16(st->rx_buf);
+	else
+		return -EINVAL;
+
+	return 0;
+}
+
+static int ad5706r_read_raw(struct iio_dev *indio_dev,
+			    struct iio_chan_spec const *chan, int *val,
+			    int *val2, long mask)
+{
+	struct ad5706r_state *st = iio_priv(indio_dev);
+	u16 reg_val;
+	int ret;
+
+	switch (mask) {
+	case IIO_CHAN_INFO_RAW:
+		scoped_guard(mutex, &st->lock) {
+			ret = ad5706r_spi_read(st, AD5706R_REG_DAC_DATA_READBACK_CH(chan->channel),
+					       &reg_val);
+
+			if (ret)
+				return ret;
+
+			*val = reg_val;
+		}
+		return IIO_VAL_INT;
+	case IIO_CHAN_INFO_SCALE:
+		*val = 50;
+		*val2 = AD5706R_DAC_RESOLUTION;
+		return IIO_VAL_FRACTIONAL_LOG2;
+	}
+
+	return -EINVAL;
+}
+
+static int ad5706r_write_raw(struct iio_dev *indio_dev,
+			     struct iio_chan_spec const *chan, int val,
+			     int val2, long mask)
+{
+	struct ad5706r_state *st = iio_priv(indio_dev);
+
+	switch (mask) {
+	case IIO_CHAN_INFO_RAW:
+		if (val < 0 || val >= AD5706R_DAC_MAX_CODE)
+			return -EINVAL;
+
+		guard(mutex)(&st->lock);
+		return ad5706r_spi_write(st,
+					 AD5706R_REG_DAC_INPUT_A_CH(chan->channel),
+					 val);
+	default:
+		return -EINVAL;
+	}
+}
+
+static const struct iio_info ad5706r_info = {
+	.read_raw = ad5706r_read_raw,
+	.write_raw = ad5706r_write_raw,
+};
+
+#define AD5706R_CHAN(_channel) {				\
+	.type = IIO_CURRENT,					\
+	.info_mask_separate = BIT(IIO_CHAN_INFO_RAW) |		\
+			      BIT(IIO_CHAN_INFO_SCALE),	\
+	.output = 1,						\
+	.indexed = 1,						\
+	.channel = _channel,					\
+}
+
+static const struct iio_chan_spec ad5706r_channels[] = {
+	AD5706R_CHAN(0),
+	AD5706R_CHAN(1),
+	AD5706R_CHAN(2),
+	AD5706R_CHAN(3),
+};
+
+static int ad5706r_probe(struct spi_device *spi)
+{
+	struct iio_dev *indio_dev;
+	struct ad5706r_state *st;
+	int ret;
+
+	indio_dev = devm_iio_device_alloc(&spi->dev, sizeof(*st));
+	if (!indio_dev)
+		return -ENOMEM;
+
+	st = iio_priv(indio_dev);
+	st->spi = spi;
+
+	ret = devm_mutex_init(&spi->dev, &st->lock);
+	if (ret)
+		return ret;
+
+	indio_dev->name = "ad5706r";
+	indio_dev->info = &ad5706r_info;
+	indio_dev->modes = INDIO_DIRECT_MODE;
+	indio_dev->channels = ad5706r_channels;
+	indio_dev->num_channels = ARRAY_SIZE(ad5706r_channels);
+
+	return devm_iio_device_register(&spi->dev, indio_dev);
+}
+
+static const struct of_device_id ad5706r_of_match[] = {
+	{ .compatible = "adi,ad5706r" },
+	{}
+};
+MODULE_DEVICE_TABLE(of, ad5706r_of_match);
+
+static const struct spi_device_id ad5706r_id[] = {
+	{ "ad5706r" },
+	{}
+};
+MODULE_DEVICE_TABLE(spi, ad5706r_id);
+
+static struct spi_driver ad5706r_driver = {
+	.driver = {
+		.name = "ad5706r",
+		.of_match_table = ad5706r_of_match,
+	},
+	.probe = ad5706r_probe,
+	.id_table = ad5706r_id,
+};
+module_spi_driver(ad5706r_driver);
+
+MODULE_AUTHOR("Alexis Czezar Torreno <alexisczezar.torreno@analog.com>");
+MODULE_DESCRIPTION("AD5706R 16-bit Current Output DAC driver");
+MODULE_LICENSE("GPL");

-- 
2.34.1