staging:iio:adc: Add SPEAr ADC driver

This patch implements the basic single data conversion support for
the SPEAr600 SoC ADC. The register layout of SPEAr600 differs a bit
from other SPEAr SoC variants (e.g. SPEAr3xx). These differences are
handled via DT compatible testing. Resulting in a multi-arch binary.

This driver is currently tested only on SPEAr600. Future patches may add
support for other SoC variants (SPEAr3xx) and features like software
buffer or DMA.
Signed-off-by: Stefan Roese <sr@denx.de>
Acked-by: Jonathan Cameron <jic23@kernel.org>
Acked-by: Viresh Kumar <viresh.kumar@st.com>
Cc: Greg KH <greg@kroah.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

Documentation/devicetree/bindings/staging/iio/adc/spear-adc.txt

+* ST SPEAr ADC device driver
+
+Required properties:
+- compatible: Should be "st,spear600-adc"
+- reg: Address and length of the register set for the device
+- interrupt-parent: Should be the phandle for the interrupt controller
+  that services interrupts for this device
+- interrupts: Should contain the ADC interrupt
+- sampling-frequency: Default sampling frequency
+
+Optional properties:
+- vref-external: External voltage reference in milli-volts. If omitted
+  the internal voltage reference will be used.
+- average-samples: Number of samples to generate an average value. If
+  omitted, single data conversion will be used.
+
+Examples:
+
+	adc: adc@d8200000 {
+		compatible = "st,spear600-adc";
+		reg = <0xd8200000 0x1000>;
+		interrupt-parent = <&vic1>;
+		interrupts = <6>;
+		sampling-frequency = <5000000>;
+		vref-external = <2500>;	/* 2.5V VRef */
+	};

drivers/staging/iio/adc/Kconfig

@@ -202,4 +202,11 @@ config LPC32XX_ADC
 	  touchscreen driver, so you can only select one of the two drivers
 	  (lpc32xx_adc or lpc32xx_ts). Provides direct access via sysfs.
 
+config SPEAR_ADC
+	tristate "ST SPEAr ADC"
+	depends on PLAT_SPEAR
+	help
+	  Say yes here to build support for the integrated ADC inside the
+	  ST SPEAr SoC. Provides direct access via sysfs.
+
 endmenu

drivers/staging/iio/adc/Makefile

@@ -38,3 +38,4 @@ obj-$(CONFIG_ADT7310) += adt7310.o
 obj-$(CONFIG_ADT7410) += adt7410.o
 obj-$(CONFIG_AD7280) += ad7280a.o
 obj-$(CONFIG_LPC32XX_ADC) += lpc32xx_adc.o
+obj-$(CONFIG_SPEAR_ADC) += spear_adc.o