dmaengine: Add support for BCM2835

Add support for DMA controller of BCM2835 as used in the Raspberry Pi.
Currently it only supports cyclic DMA.

Signed-off-by: Florian Meier <florian.meier@koalo.de>
Reviewed-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Acked-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Vinod Koul <vinod.koul@intel.com>

1 files changed, 57 insertions, 0 deletions

diff --git a/Documentation/devicetree/bindings/dma/bcm2835-dma.txt b/Documentation/devicetree/bindings/dma/bcm2835-dma.txt
new file mode 100644
index 000000000000..1396078d15ac
--- /dev/null
+++ b/Documentation/devicetree/bindings/dma/bcm2835-dma.txt
@@ -0,0 +1,57 @@
+* BCM2835 DMA controller
+
+The BCM2835 DMA controller has 16 channels in total.
+Only the lower 13 channels have an associated IRQ.
+Some arbitrary channels are used by the firmware
+(1,3,6,7 in the current firmware version).
+The channels 0,2 and 3 have special functionality
+and should not be used by the driver.
+
+Required properties:
+- compatible: Should be "brcm,bcm2835-dma".
+- reg: Should contain DMA registers location and length.
+- interrupts: Should contain the DMA interrupts associated
+                to the DMA channels in ascending order.
+- #dma-cells: Must be <1>, the cell in the dmas property of the
+                client device represents the DREQ number.
+- brcm,dma-channel-mask: Bit mask representing the channels
+                         not used by the firmware in ascending order,
+                         i.e. first channel corresponds to LSB.
+
+Example:
+
+dma: dma@7e007000 {
+        compatible = "brcm,bcm2835-dma";
+        reg = <0x7e007000 0xf00>;
+        interrupts = <1 16>,
+                     <1 17>,
+                     <1 18>,
+                     <1 19>,
+                     <1 20>,
+                     <1 21>,
+                     <1 22>,
+                     <1 23>,
+                     <1 24>,
+                     <1 25>,
+                     <1 26>,
+                     <1 27>,
+                     <1 28>;
+
+        #dma-cells = <1>;
+        brcm,dma-channel-mask = <0x7f35>;
+};
+
+DMA clients connected to the BCM2835 DMA controller must use the format
+described in the dma.txt file, using a two-cell specifier for each channel.
+
+Example:
+
+bcm2835_i2s: i2s@7e203000 {
+        compatible = "brcm,bcm2835-i2s";
+        reg = < 0x7e203000 0x20>,
+              < 0x7e101098 0x02>;
+
+        dmas = <&dma 2>,
+               <&dma 3>;
+        dma-names = "tx", "rx";
+};