dmaengine: apple-sio: Add Apple SIO driver

Add a dmaengine driver for the Apple SIO coprocessor found on Apple
SoCs where it provides DMA services. Have the driver support cyclic
transactions so that ALSA drivers can rely on it in audio output to
HDMI and DisplayPort.

Signed-off-by: Martin Povišer <povik+lin@cutebit.org>

Author: povik

MAINTAINERS

@@ -2397,9 +2397,11 @@ M:	Martin Povišer <povik+lin@cutebit.org>
 L:	asahi@lists.linux.dev
 L:	linux-sound@vger.kernel.org
 S:	Maintained
+F:	Documentation/devicetree/bindings/dma/apple,sio.yaml
 F:	Documentation/devicetree/bindings/sound/adi,ssm3515.yaml
 F:	Documentation/devicetree/bindings/sound/cirrus,cs42l84.yaml
 F:	Documentation/devicetree/bindings/sound/apple,*
+F:	drivers/dma/apple-sio.c
 F:	sound/soc/apple/*
 F:	sound/soc/codecs/cs42l83-i2c.c
 F:	sound/soc/codecs/cs42l84.*

drivers/dma/Kconfig

@@ -92,6 +92,16 @@ config APPLE_ADMAC
 	help
 	  Enable support for Audio DMA Controller found on Apple Silicon SoCs.
 
+config APPLE_SIO
+	tristate "Apple SIO support"
+	depends on ARCH_APPLE || COMPILE_TEST
+	depends on APPLE_RTKIT
+	depends on OF_ADDRESS
+	select DMA_ENGINE
+	help
+	  Enable support for the SIO coprocessor found on Apple Silicon SoCs
+	  where it provides DMA services.
+
 config ARM_DMA350
 	tristate "Arm DMA-350 support"
 	depends on ARM || ARM64 || COMPILE_TEST

drivers/dma/Makefile

@@ -17,6 +17,7 @@ obj-$(CONFIG_ALTERA_MSGDMA) += altera-msgdma.o
 obj-$(CONFIG_AMBA_PL08X) += amba-pl08x.o
 obj-$(CONFIG_AMCC_PPC440SPE_ADMA) += ppc4xx/
 obj-$(CONFIG_APPLE_ADMAC) += apple-admac.o
+obj-$(CONFIG_APPLE_SIO) += apple-sio.o
 obj-$(CONFIG_ARM_DMA350) += arm-dma350.o
 obj-$(CONFIG_AT_HDMAC) += at_hdmac.o
 obj-$(CONFIG_AT_XDMAC) += at_xdmac.o