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 * DMA router
  35
  36 DMA routers are transparent IP blocks used to route DMA request lines from
  37 devices to the DMA controller. Some SoCs (like TI DRA7x) have more peripherals
  38 integrated with DMA requests than what the DMA controller can handle directly.
  39
  40 Required property:
  41 - dma-masters:          phandle of the DMA controller or list of phandles for
  42                         the DMA controllers the router can direct the signal to.
  43 - #dma-cells:           Must be at least 1. Used to provide DMA router specific
  44                         information. See DMA client binding below for more
  45                         details.
  46
  47 Optional properties:
  48 - dma-requests:         Number of incoming request lines the router can handle.
  49 - In the node pointed by the dma-masters:
  50         - dma-requests: The router driver might need to look for this in order
  51                         to configure the routing.
  52
  53 Example:
  54         sdma_xbar: dma-router@4a002b78 {
  55                 compatible = "ti,dra7-dma-crossbar";
  56                 reg = <0x4a002b78 0xfc>;
  57                 #dma-cells = <1>;
  58                 dma-requests = <205>;
  59                 ti,dma-safe-map = <0>;
  60                 dma-masters = <&sdma>;
  61         };
  62
  63 * DMA client
  64
  65 Client drivers should specify the DMA property using a phandle to the controller
  66 followed by DMA controller specific data.
  67
  68 Required property:
  69 - dmas:                 List of one or more DMA specifiers, each consisting of
  70                         - A phandle pointing to DMA controller node
  71                         - A number of integer cells, as determined by the
  72                           #dma-cells property in the node referenced by phandle
  73                           containing DMA controller specific information. This
  74                           typically contains a DMA request line number or a
  75                           channel number, but can contain any data that is
  76                           required for configuring a channel.
  77 - dma-names:            Contains one identifier string for each DMA specifier in
  78                         the dmas property. The specific strings that can be used
  79                         are defined in the binding of the DMA client device.
  80                         Multiple DMA specifiers can be used to represent
  81                         alternatives and in this case the dma-names for those
  82                         DMA specifiers must be identical (see examples).
  83
  84 Examples:
  85
  86 1. A device with one DMA read channel, one DMA write channel:
  87
  88         i2c1: i2c@1 {
  89                 ...
  90                 dmas = <&dma 2          /* read channel */
  91                         &dma 3>;        /* write channel */
  92                 dma-names = "rx", "tx";
  93                 ...
  94         };
  95
  96 2. A single read-write channel with three alternative DMA controllers:
  97
  98         dmas = <&dma1 5
  99                 &dma2 7
 100                 &dma3 2>;
 101         dma-names = "rx-tx", "rx-tx", "rx-tx";
 102
 103 3. A device with three channels, one of which has two alternatives:
 104
 105         dmas = <&dma1 2                 /* read channel */
 106                 &dma1 3                 /* write channel */
 107                 &dma2 0                 /* error read */
 108                 &dma3 0>;               /* alternative error read */
 109         dma-names = "rx", "tx", "error", "error";