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.

---
Changes v2->v3:
- drop .owner = THIS_MODULE from the struct platform_driver initialization;
- rebase to 3.18-rc7.

Changes v1->v2:
- fix module name in the sound/soc/xtensa/Makefile;
- split PCM data transfer code and I2S interface setup code;
- move clock enabling/disabling to runtime PM code;
- document I2S interface RATIO field;
- rewrite I2S interface LEVEL field calculation to avoid overflows;
- drop select statements from Kconfig;
- document RCU usage for tx_substream;
- clean up code running in RCU read-side critical section;
- use threaded IRQ handler instead of IRQ + tasklet;
- remove empty PCM callback handlers;
- add const to static structures where applicable;
- use platform_set_drvdata instead of dev_set_drvdata;
- drop redundant error reporting code;
- use platform_get_irq instead of platform_get_resource;
- clean up xtfpga_i2s_remove;
- add comments.

 .../devicetree/bindings/sound/cdns,xtfpga-i2s.txt  |  18 +
 MAINTAINERS                                        |   1 +
 sound/soc/Kconfig                                  |   1 +
 sound/soc/Makefile                                 |   1 +
 sound/soc/xtensa/Kconfig                           |   7 +
 sound/soc/xtensa/Makefile                          |   3 +
 sound/soc/xtensa/xtfpga-i2s.c                      | 675 +++++++++++++++++++++
 7 files changed, 706 insertions(+)
 create mode 100644 Documentation/devicetree/bindings/sound/cdns,xtfpga-i2s.txt
 create mode 100644 sound/soc/xtensa/Kconfig
 create mode 100644 sound/soc/xtensa/Makefile
 create mode 100644 sound/soc/xtensa/xtfpga-i2s.c

new file mode 100644
index 0000000..befd125
@@ -0,0 +1,18 @@
+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>;
+	};

index ddb9ac8..f1eb40f 100644
@@ -10628,6 +10628,7 @@ M:	Max Filippov <[email protected]>
 L:	linux-xtensa-PjhNF2WwrV/[email protected]
 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 <[email protected]>

index 7d5d644..dcc79aa 100644
@@ -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"

index 865e090..5b3c8f6 100644
@@ -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/

new file mode 100644
index 0000000..c201beb
@@ -0,0 +1,7 @@
+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.

new file mode 100644
index 0000000..15efbf9
@@ -0,0 +1,3 @@
+snd-soc-xtfpga-i2s-objs := xtfpga-i2s.o
+
+obj-$(CONFIG_SND_SOC_XTFPGA_I2S) += snd-soc-xtfpga-i2s.o

1.8.1.4

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Applied, thanks - the revisions to the RCU stuff make it a lot clearer, thanks.