DMA: sa11x0: add SA-11x0 DMA driver

Add support for the SA-11x0 DMA driver, which replaces the private
API version in arch/arm/mach-sa1100/dma.c.

We model this as a set of virtual DMA channels, one for each request
signal, and assign the virtual DMA channel to a physical DMA channel
when there is work to be done.  This allows DMA users to claim their
channels, and hold them while not in use, without affecting the
availability of the physical channels.

Another advantage over this approach, compared to the private version,
is that a channel can be reconfigured on the fly without having to
release and re-request it - which for the IrDA driver, allows us to
use DMA for SIR mode transmit without eating up three physical
channels.  As IrDA is half-duplex, we actually only need one physical
channel, and this architecture allows us to achieve that.

Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>

drivers/dma/Kconfig

@@ -252,6 +252,15 @@ config EP93XX_DMA
 	help
 	  Enable support for the Cirrus Logic EP93xx M2P/M2M DMA controller.
 
+config DMA_SA11X0
+	tristate "SA-11x0 DMA support"
+	depends on ARCH_SA1100
+	select DMA_ENGINE
+	help
+	  Support the DMA engine found on Intel StrongARM SA-1100 and
+	  SA-1110 SoCs.  This DMA engine can only be used with on-chip
+	  devices.
+
 config DMA_ENGINE
 	bool
 

drivers/dma/Makefile

@@ -27,3 +27,4 @@ obj-$(CONFIG_PL330_DMA) += pl330.o
 obj-$(CONFIG_PCH_DMA) += pch_dma.o
 obj-$(CONFIG_AMBA_PL08X) += amba-pl08x.o
 obj-$(CONFIG_EP93XX_DMA) += ep93xx_dma.o
+obj-$(CONFIG_DMA_SA11X0) += sa11x0-dma.o