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

@@ -1978,8 +1978,10 @@ M:	Martin Povišer <povik+lin@cutebit.org>
 L:	asahi@lists.linux.dev
 L:	alsa-devel@alsa-project.org (moderated for non-subscribers)
 S:	Maintained
+F:	Documentation/devicetree/bindings/dma/apple,sio.yaml
 F:	Documentation/devicetree/bindings/sound/adi,ssm3515.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/ssm3515.c

drivers/dma/Kconfig

@@ -89,10 +89,21 @@ config APPLE_ADMAC
 	tristate "Apple ADMAC support"
 	depends on ARCH_APPLE || COMPILE_TEST
 	select DMA_ENGINE
+	select DMA_VIRTUAL_CHANNELS
 	default ARCH_APPLE
 	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
+	select DMA_ENGINE
+	default m if ARCH_APPLE
+	help
+	  Enable support for the SIO coprocessor found on Apple Silicon SoCs
+	  where it provides DMA services.
+
 config AT_HDMAC
 	tristate "Atmel AHB DMA support"
 	depends on ARCH_AT91

drivers/dma/Makefile

@@ -18,6 +18,7 @@ obj-$(CONFIG_AMBA_PL08X) += amba-pl08x.o
 obj-$(CONFIG_AMCC_PPC440SPE_ADMA) += ppc4xx/
 obj-$(CONFIG_AMD_PTDMA) += ptdma/
 obj-$(CONFIG_APPLE_ADMAC) += apple-admac.o
+obj-$(CONFIG_APPLE_SIO) += apple-sio.o
 obj-$(CONFIG_AT_HDMAC) += at_hdmac.o
 obj-$(CONFIG_AT_XDMAC) += at_xdmac.o
 obj-$(CONFIG_AXI_DMAC) += dma-axi-dmac.o