ASoC: Add support for BCM2835

This driver adds support for digital audio (I2S)
for the BCM2835 SoC that is used by the
Raspberry Pi. External audio codecs can be
connected to the Raspberry Pi via P5 header.

It relies on cyclic DMA engine support for BCM2835.
Signed-off-by: NFlorian Meier <florian.meier@koalo.de>
Signed-off-by: NMark Brown <broonie@linaro.org>

Documentation/devicetree/bindings/sound/bcm2835-i2s.txt

+* Broadcom BCM2835 SoC I2S/PCM module
+
+Required properties:
+- compatible: "brcm,bcm2835-i2s"
+- reg: A list of base address and size entries:
+	* The first entry should cover the PCM registers
+	* The second entry should cover the PCM clock registers
+- dmas: List of DMA controller phandle and DMA request line ordered pairs.
+- dma-names: Identifier string for each DMA request line in the dmas property.
+  These strings correspond 1:1 with the ordered pairs in dmas.
+
+  One of the DMA channels will be responsible for transmission (should be
+  named "tx") and one for reception (should be named "rx").
+
+Example:
+
+bcm2835_i2s: i2s@7e203000 {
+	compatible = "brcm,bcm2835-i2s";
+	reg = <0x7e203000 0x20>,
+	      <0x7e101098 0x02>;
+
+	dmas = <&dma 2>,
+	       <&dma 3>;
+	dma-names = "tx", "rx";
+};

sound/soc/Kconfig

@@ -33,6 +33,7 @@ config SND_SOC_GENERIC_DMAENGINE_PCM
 # All the supported SoCs
 source "sound/soc/atmel/Kconfig"
 source "sound/soc/au1x/Kconfig"
+source "sound/soc/bcm/Kconfig"
 source "sound/soc/blackfin/Kconfig"
 source "sound/soc/cirrus/Kconfig"
 source "sound/soc/davinci/Kconfig"

sound/soc/Makefile

@@ -10,6 +10,7 @@ obj-$(CONFIG_SND_SOC)	+= codecs/
 obj-$(CONFIG_SND_SOC)	+= generic/
 obj-$(CONFIG_SND_SOC)	+= atmel/
 obj-$(CONFIG_SND_SOC)	+= au1x/
+obj-$(CONFIG_SND_SOC)	+= bcm/
 obj-$(CONFIG_SND_SOC)	+= blackfin/
 obj-$(CONFIG_SND_SOC)	+= cirrus/
 obj-$(CONFIG_SND_SOC)	+= davinci/

sound/soc/bcm/Kconfig

+config SND_BCM2835_SOC_I2S
+	tristate "SoC Audio support for the Broadcom BCM2835 I2S module"
+	depends on ARCH_BCM2835 || COMPILE_TEST
+	select SND_SOC_DMAENGINE_PCM
+	select SND_SOC_GENERIC_DMAENGINE_PCM
+	select REGMAP_MMIO
+	help
+	  Say Y or M if you want to add support for codecs attached to
+	  the BCM2835 I2S interface. You will also need
+	  to select the audio interfaces to support below.

sound/soc/bcm/Makefile

+# BCM2835 Platform Support
+snd-soc-bcm2835-i2s-objs := bcm2835-i2s.o
+
+obj-$(CONFIG_SND_BCM2835_SOC_I2S) += snd-soc-bcm2835-i2s.o
+