iio: dac: support the ad9739a RF DAC

The AD9739A is a 14-bit, 2.5 GSPS high performance RF DACs that are capable
of synthesizing wideband signals from DC up to 3 GHz.

A dual-port, source synchronous, LVDS interface simplifies the digital
interface with existing FGPA/ASIC technology. On-chip controllers are used
to manage external and internal clock domain variations over temperature to
ensure reliable data transfer from the host to the DAC core.

Co-developed-by: Dragos Bogdan <dragos.bogdan@analog.com>
Signed-off-by: Dragos Bogdan <dragos.bogdan@analog.com>
Signed-off-by: Nuno Sa <nuno.sa@analog.com>
Link: https://lore.kernel.org/r/20240419-iio-backend-axi-dac-v4-10-5ca45b4de294@analog.com
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>

Documentation/ABI/testing/sysfs-bus-iio-ad9739a

@@ -0,0 +1,19 @@
+What:		/sys/bus/iio/devices/iio:deviceX/out_voltageY_operating_mode
+KernelVersion:	6.9
+Contact:	linux-iio@vger.kernel.org
+Description:
+		DAC operating mode. One of the following modes can be selected:
+
+		* normal: This is DAC normal mode.
+		* mixed-mode: In this mode the output is effectively chopped at
+			      the DAC sample rate. This has the effect of
+			      reducing the power of the fundamental signal while
+			      increasing the power of the images centered around
+			      the DAC sample rate, thus improving the output
+			      power of these images.
+
+What:		/sys/bus/iio/devices/iio:deviceX/out_voltageY_operating_mode_available
+KernelVersion:	6.9
+Contact:	linux-iio@vger.kernel.org
+Description:
+		Available operating modes.

MAINTAINERS

@@ -1241,6 +1241,7 @@ L:	linux-iio@vger.kernel.org
 S:	Supported
 W:	https://ez.analog.com/linux-software-drivers
 F:	Documentation/devicetree/bindings/iio/dac/adi,ad9739a.yaml
+F:	drivers/iio/dac/ad9739a.c
 
 ANALOG DEVICES INC ADA4250 DRIVER
 M:	Antoniu Miclaus <antoniu.miclaus@analog.com>

drivers/iio/dac/Kconfig

@@ -131,6 +131,22 @@ 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 AD9739A
+	tristate "Analog Devices AD9739A RF DAC spi driver"
+	depends on SPI || COMPILE_TEST
+	select REGMAP_SPI
+	select IIO_BACKEND
+	help
+	  Say yes here to build support for Analog Devices AD9739A Digital-to
+	  Analog Converter.
+
+	  The driver requires the assistance of the AXI DAC IP core to operate,
+	  since SPI is used for configuration only, while data has to be
+	  streamed into memory via DMA.
+
+	  To compile this driver as a module, choose M here: the module will be
+	  called ad9739a.
+
 config ADI_AXI_DAC
 	tristate "Analog Devices Generic AXI DAC IP core driver"
 	select IIO_BUFFER

drivers/iio/dac/Makefile

@@ -29,6 +29,7 @@ obj-$(CONFIG_AD5696_I2C) += ad5696-i2c.o
 obj-$(CONFIG_AD7293) += ad7293.o
 obj-$(CONFIG_AD7303) += ad7303.o
 obj-$(CONFIG_AD8801) += ad8801.o
+obj-$(CONFIG_AD9739A) += ad9739a.o
 obj-$(CONFIG_ADI_AXI_DAC) += adi-axi-dac.o
 obj-$(CONFIG_CIO_DAC) += cio-dac.o
 obj-$(CONFIG_DPOT_DAC) += dpot-dac.o