Documentation/devicetree/bindings/dma/brcm,bcm2835-dma.txt

   1 * BCM2835 DMA controller
   2
   3 The BCM2835 DMA controller has 16 channels in total.
   4 Only the lower 13 channels have an associated IRQ.
   5 Some arbitrary channels are used by the firmware
   6 (1,3,6,7 in the current firmware version).
   7 The channels 0,2 and 3 have special functionality
   8 and should not be used by the driver.
   9
  10 Required properties:
  11 - compatible: Should be "brcm,bcm2835-dma".
  12 - reg: Should contain DMA registers location and length.
  13 - interrupts: Should contain the DMA interrupts associated
  14                 to the DMA channels in ascending order.
  15 - #dma-cells: Must be <1>, the cell in the dmas property of the
  16                 client device represents the DREQ number.
  17 - brcm,dma-channel-mask: Bit mask representing the channels
  18                          not used by the firmware in ascending order,
  19                          i.e. first channel corresponds to LSB.
  20
  21 Example:
  22
  23 dma: dma@7e007000 {
  24         compatible = "brcm,bcm2835-dma";
  25         reg = <0x7e007000 0xf00>;
  26         interrupts = <1 16>,
  27                      <1 17>,
  28                      <1 18>,
  29                      <1 19>,
  30                      <1 20>,
  31                      <1 21>,
  32                      <1 22>,
  33                      <1 23>,
  34                      <1 24>,
  35                      <1 25>,
  36                      <1 26>,
  37                      <1 27>,
  38                      <1 28>;
  39
  40         #dma-cells = <1>;
  41         brcm,dma-channel-mask = <0x7f35>;
  42 };
  43
  44 DMA clients connected to the BCM2835 DMA controller must use the format
  45 described in the dma.txt file, using a two-cell specifier for each channel.
  46
  47 Example:
  48
  49 bcm2835_i2s: i2s@7e203000 {
  50         compatible = "brcm,bcm2835-i2s";
  51         reg = < 0x7e203000 0x20>,
  52               < 0x7e101098 0x02>;
  53
  54         dmas = <&dma 2>,
  55                <&dma 3>;
  56         dma-names = "tx", "rx";
  57 };