iio: adc: adi-axi-adc: add support for AXI ADC IP core

This change adds support for the Analog Devices Generic AXI ADC IP core.
The IP core is used for interfacing with analog-to-digital (ADC) converters
that require either a high-speed serial interface (JESD204B/C) or a source
synchronous parallel interface (LVDS/CMOS).

Usually, some other interface type (i.e SPI) is used as a control interface
for the actual ADC, while the IP core (controlled via this driver), will
interface to the data-lines of the ADC and handle  the streaming of data
into memory via DMA.

Because of this, the AXI ADC driver needs the other SPI-ADC driver to
register with it. The SPI-ADC needs to be register via the SPI framework,
while the AXI ADC registers as a platform driver. The two cannot be ordered
in a hierarchy as both drivers have their own registers, and trying to
organize this [in a hierarchy becomes] problematic when trying to map
memory/registers.

There are some modes where the AXI ADC can operate as standalone ADC, but
those will be implemented at a later point in time.

DocLink: https://wiki.analog.com/resources/fpga/docs/axi_adc_ip

Signed-off-by: Michael Hennerich <michael.hennerich@analog.com>
Signed-off-by: Lars-Peter Clausen <lars@metafoo.de>
Signed-off-by: Alexandru Ardelean <alexandru.ardelean@analog.com>
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>

drivers/iio/adc/Kconfig

@@ -246,6 +246,26 @@ config AD799X
 	  To compile this driver as a module, choose M here: the module will be
 	  called ad799x.
 
+config ADI_AXI_ADC
+	tristate "Analog Devices Generic AXI ADC IP core driver"
+	select IIO_BUFFER
+	select IIO_BUFFER_HW_CONSUMER
+	select IIO_BUFFER_DMAENGINE
+	help
+	  Say yes here to build support for Analog Devices Generic
+	  AXI ADC IP core. The IP core is used for interfacing with
+	  analog-to-digital (ADC) converters that require either a high-speed
+	  serial interface (JESD204B/C) or a source synchronous parallel
+	  interface (LVDS/CMOS).
+	  Typically (for such devices) SPI will be used for configuration only,
+	  while this IP core handles the streaming of data into memory via DMA.
+
+	  Link: https://wiki.analog.com/resources/fpga/docs/axi_adc_ip
+	  If unsure, say N (but it's safe to say "Y").
+
+	  To compile this driver as a module, choose M here: the
+	  module will be called adi-axi-adc.
+
 config ASPEED_ADC
 	tristate "Aspeed ADC"
 	depends on ARCH_ASPEED || COMPILE_TEST

drivers/iio/adc/Makefile

@@ -26,6 +26,7 @@ obj-$(CONFIG_AD7793) += ad7793.o
 obj-$(CONFIG_AD7887) += ad7887.o
 obj-$(CONFIG_AD7949) += ad7949.o
 obj-$(CONFIG_AD799X) += ad799x.o
+obj-$(CONFIG_ADI_AXI_ADC) += adi-axi-adc.o
 obj-$(CONFIG_ASPEED_ADC) += aspeed_adc.o
 obj-$(CONFIG_AT91_ADC) += at91_adc.o
 obj-$(CONFIG_AT91_SAMA5D2_ADC) += at91-sama5d2_adc.o