spi: sunxi: Add Allwinner A10 SPI controller driver

The older Allwinner SoCs (A10, A13, A10s and A20) all have the same SPI
controller.

Unfortunately, this SPI controller, even though quite similar, is significantly
different from the recently supported A31 SPI controller (different registers
offset, split/merged registers, etc.). Supporting both controllers in a single
driver would be unreasonable, hence the addition of a new driver.

Like its more recent counterpart, it supports DMA, but the driver only does PIO
until we have a dmaengine driver for this platform.
Signed-off-by: Maxime Ripard <maxime.ripard@free-electrons.com>
Signed-off-by: Mark Brown <broonie@linaro.org>

Documentation/devicetree/bindings/spi/spi-sun4i.txt

+Allwinner A10 SPI controller
+
+Required properties:
+- compatible: Should be "allwinner,sun4-a10-spi".
+- reg: Should contain register location and length.
+- interrupts: Should contain interrupt.
+- clocks: phandle to the clocks feeding the SPI controller. Two are
+          needed:
+  - "ahb": the gated AHB parent clock
+  - "mod": the parent module clock
+- clock-names: Must contain the clock names described just above
+
+Example:
+
+spi1: spi@01c06000 {
+	compatible = "allwinner,sun4i-a10-spi";
+	reg = <0x01c06000 0x1000>;
+	interrupts = <11>;
+	clocks = <&ahb_gates 21>, <&spi1_clk>;
+	clock-names = "ahb", "mod";
+	status = "disabled";
+	#address-cells = <1>;
+	#size-cells = <0>;
+};

drivers/spi/Kconfig

@@ -446,6 +446,12 @@ config SPI_SIRF
 	help
 	  SPI driver for CSR SiRFprimaII SoCs
 
+config SPI_SUN4I
+	tristate "Allwinner A10 SoCs SPI controller"
+	depends on ARCH_SUNXI || COMPILE_TEST
+	help
+	  SPI driver for Allwinner sun4i, sun5i and sun7i SoCs
+
 config SPI_SUN6I
 	tristate "Allwinner A31 SPI controller"
 	depends on ARCH_SUNXI || COMPILE_TEST

drivers/spi/Makefile

@@ -70,6 +70,7 @@ obj-$(CONFIG_SPI_SH_HSPI)		+= spi-sh-hspi.o
 obj-$(CONFIG_SPI_SH_MSIOF)		+= spi-sh-msiof.o
 obj-$(CONFIG_SPI_SH_SCI)		+= spi-sh-sci.o
 obj-$(CONFIG_SPI_SIRF)		+= spi-sirf.o
+obj-$(CONFIG_SPI_SUN4I)			+= spi-sun4i.o
 obj-$(CONFIG_SPI_SUN6I)			+= spi-sun6i.o
 obj-$(CONFIG_SPI_TEGRA114)		+= spi-tegra114.o
 obj-$(CONFIG_SPI_TEGRA20_SFLASH)	+= spi-tegra20-sflash.o