Documentation/devicetree/bindings/dma/dma.txt

   1 * Generic DMA Controller and DMA request bindings
   2
   3 Generic binding to provide a way for a driver using DMA Engine to retrieve the
   4 DMA request or channel information that goes from a hardware device to a DMA
   5 controller.
   6
   7
   8 * DMA controller
   9
  10 Required property:
  11 - #dma-cells:           Must be at least 1. Used to provide DMA controller
  12                         specific information. See DMA client binding below for
  13                         more details.
  14
  15 Optional properties:
  16 - dma-channels:         Number of DMA channels supported by the controller.
  17 - dma-requests:         Number of DMA request signals supported by the
  18                         controller.
  19
  20 Example:
  21
  22         dma: dma@48000000 {
  23                 compatible = "ti,omap-sdma";
  24                 reg = <0x48000000 0x1000>;
  25                 interrupts = <0 12 0x4
  26                               0 13 0x4
  27                               0 14 0x4
  28                               0 15 0x4>;
  29                 #dma-cells = <1>;
  30                 dma-channels = <32>;
  31                 dma-requests = <127>;
  32         };
  33
  34
  35 * DMA client
  36
  37 Client drivers should specify the DMA property using a phandle to the controller
  38 followed by DMA controller specific data.
  39
  40 Required property:
  41 - dmas:                 List of one or more DMA specifiers, each consisting of
  42                         - A phandle pointing to DMA controller node
  43                         - A number of integer cells, as determined by the
  44                           #dma-cells property in the node referenced by phandle
  45                           containing DMA controller specific information. This
  46                           typically contains a DMA request line number or a
  47                           channel number, but can contain any data that is
  48                           required for configuring a channel.
  49 - dma-names:            Contains one identifier string for each DMA specifier in
  50                         the dmas property. The specific strings that can be used
  51                         are defined in the binding of the DMA client device.
  52                         Multiple DMA specifiers can be used to represent
  53                         alternatives and in this case the dma-names for those
  54                         DMA specifiers must be identical (see examples).
  55
  56 Examples:
  57
  58 1. A device with one DMA read channel, one DMA write channel:
  59
  60         i2c1: i2c@1 {
  61                 ...
  62                 dmas = <&dma 2          /* read channel */
  63                         &dma 3>;        /* write channel */
  64                 dma-names = "rx", "tx";
  65                 ...
  66         };
  67
  68 2. A single read-write channel with three alternative DMA controllers:
  69
  70         dmas = <&dma1 5
  71                 &dma2 7
  72                 &dma3 2>;
  73         dma-names = "rx-tx", "rx-tx", "rx-tx";
  74
  75 3. A device with three channels, one of which has two alternatives:
  76
  77         dmas = <&dma1 2                 /* read channel */
  78                 &dma1 3                 /* write channel */
  79                 &dma2 0                 /* error read */
  80                 &dma3 0>;               /* alternative error read */
  81         dma-names = "rx", "tx", "error", "error";