Re: [alsa-devel] [PATCHv3] dmaengine: Add support for BCM2835

On Nov 11, 2013, at 4:05 PM, Florian Meier florian.meier@koalo.de wrote:

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

Thank you for your comments! I hope I have now removed all leftovers of the sg struct. Regarding the endian-ness: I have not found any hint about that in the datasheet. Therefore, I chose uint32_t. If you think fixed le32 is more likely I will change it. The PAD fields do not seem to be used, but the datasheet states they should be set to 0.

.../devicetree/bindings/dma/bcm2835-dma.txt | 57 ++ arch/arm/boot/dts/bcm2835.dtsi | 23 + drivers/dma/Kconfig | 6 + drivers/dma/Makefile | 1 + drivers/dma/bcm2835-dma.c | 810 ++++++++++++++++++++ 5 files changed, 897 insertions(+) create mode 100644 Documentation/devicetree/bindings/dma/bcm2835-dma.txt create mode 100644 drivers/dma/bcm2835-dma.c

diff --git a/Documentation/devicetree/bindings/dma/bcm2835-dma.txt b/Documentation/devicetree/bindings/dma/bcm2835-dma.txt new file mode 100644 index 0000000..9542ac8 --- /dev/null +++ b/Documentation/devicetree/bindings/dma/bcm2835-dma.txt @@ -0,0 +1,57 @@ +* BCM2835 DMA controller

+Required properties: +- compatible: Should be "brcm,bcm2835-dma". +- reg: Should contain DMA registers location and length. +- interrupts: Should contain all DMA interrupts. First cell is the IRQ bank

• Second cell is the IRQ number.
  

Can you be more specific about what you mean by ‘all DMA interrupts’?

+- #dma-cells: Must be <1>, used to represent the number of integer cells in +the dmas property of client devices. +- dma-channels: Maximum number of DMA channels available +- dma-requests: Number of DMA Requests. +- dma-channel-mask: Bit mask representing the channels available.

Should be brcm,dma-channel-mask

+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>;
• dma-channels = <15>;
• dma-requests = <32>;
• 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: +a phandle plus one integer cells. +The two cells in order are:

+1. A phandle pointing to the DMA controller. +2. The DREQ number.

+Example:

+bcm2835_i2s: i2s@7e203000 {

• compatible = "brcm,bcm2835-i2s";
• reg = < 0x7e203000 0x20

• 0x7e101098 0x02>;
  

• dmas = <&dma 2

• &dma 3>;
  

• dma-names = "tx", "rx";

+};

- k