ASoC: add xtensa xtfpga I2S interface and platform

XTFPGA boards provides an audio subsystem that consists of TI CDCE706
clock synthesizer, I2S transmitter and TLV320AIC23 audio codec.

I2S transmitter has MMIO-based interface that resembles that of the
OpenCores I2S transmitter. I2S transmitter is always a master on I2S
bus. There's no specialized audio DMA, sample data are transferred to
I2S transmitter FIFO by CPU through memory-mapped queue interface.
Signed-off-by: Max Filippov <jcmvbkbc@gmail.com>
Signed-off-by: Mark Brown <broonie@kernel.org>

Documentation/devicetree/bindings/sound/cdns,xtfpga-i2s.txt

+Bindings for I2S controller built into xtfpga Xtensa bitstreams.
+
+Required properties:
+- compatible: shall be "cdns,xtfpga-i2s".
+- reg: memory region (address and length) with device registers.
+- interrupts: interrupt for the device.
+- clocks: phandle to the clk used as master clock. I2S bus clock
+  is derived from it.
+
+Examples:
+
+	i2s0: xtfpga-i2s@0d080000 {
+		#sound-dai-cells = <0>;
+		compatible = "cdns,xtfpga-i2s";
+		reg = <0x0d080000 0x40>;
+		interrupts = <2 1>;
+		clocks = <&cdce706 4>;
+	};

MAINTAINERS

@@ -10628,6 +10628,7 @@ M:	Max Filippov <jcmvbkbc@gmail.com>
 L:	linux-xtensa@linux-xtensa.org
 S:	Maintained
 F:	drivers/spi/spi-xtensa-xtfpga.c
+F:	sound/soc/xtensa/xtfpga-i2s.c
 
 YAM DRIVER FOR AX.25
 M:	Jean-Paul Roubelat <jpr@f6fbb.org>

sound/soc/Kconfig

@@ -55,6 +55,7 @@ source "sound/soc/spear/Kconfig"
 source "sound/soc/tegra/Kconfig"
 source "sound/soc/txx9/Kconfig"
 source "sound/soc/ux500/Kconfig"
+source "sound/soc/xtensa/Kconfig"
 
 # Supported codecs
 source "sound/soc/codecs/Kconfig"

sound/soc/Makefile

@@ -36,3 +36,4 @@ obj-$(CONFIG_SND_SOC)	+= spear/
 obj-$(CONFIG_SND_SOC)	+= tegra/
 obj-$(CONFIG_SND_SOC)	+= txx9/
 obj-$(CONFIG_SND_SOC)	+= ux500/
+obj-$(CONFIG_SND_SOC)	+= xtensa/

sound/soc/xtensa/Kconfig

+config SND_SOC_XTFPGA_I2S
+	tristate "XTFPGA I2S master"
+	select REGMAP_MMIO
+	help
+	  Say Y or M if you want to add support for codecs attached to the
+	  I2S interface on XTFPGA daughter board. You will also need to select
+	  the drivers for the rest of XTFPGA audio subsystem.

sound/soc/xtensa/Makefile

+snd-soc-xtfpga-i2s-objs := xtfpga-i2s.o
+
+obj-$(CONFIG_SND_SOC_XTFPGA_I2S) += snd-soc-xtfpga-i2s.o