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Diffstat (limited to 'Documentation/devicetree')
-rw-r--r-- | Documentation/devicetree/bindings/dma/dma.txt | 81 |
1 files changed, 81 insertions, 0 deletions
diff --git a/Documentation/devicetree/bindings/dma/dma.txt b/Documentation/devicetree/bindings/dma/dma.txt new file mode 100644 index 000000000000..a4f59a5967d4 --- /dev/null +++ b/Documentation/devicetree/bindings/dma/dma.txt @@ -0,0 +1,81 @@ +* Generic DMA Controller and DMA request bindings + +Generic binding to provide a way for a driver using DMA Engine to retrieve the +DMA request or channel information that goes from a hardware device to a DMA +controller. + + +* DMA controller + +Required property: +- #dma-cells: Must be at least 1. Used to provide DMA controller + specific information. See DMA client binding below for + more details. + +Optional properties: +- #dma-channels: Number of DMA channels supported by the controller. +- #dma-requests: Number of DMA requests signals supported by the + controller. + +Example: + + dma: dma@48000000 { + compatible = "ti,omap-sdma" + reg = <0x48000000 0x1000>; + interrupts = <0 12 0x4 + 0 13 0x4 + 0 14 0x4 + 0 15 0x4>; + #dma-cells = <1>; + #dma-channels = <32>; + #dma-requests = <127>; + }; + + +* DMA client + +Client drivers should specify the DMA property using a phandle to the controller +followed by DMA controller specific data. + +Required property: +- dmas: List of one or more DMA specifiers, each consisting of + - A phandle pointing to DMA controller node + - A number of integer cells, as determined by the + #dma-cells property in the node referenced by phandle + containing DMA controller specific information. This + typically contains a DMA request line number or a + channel number, but can contain any data that is used + required for configuring a channel. +- dma-names: Contains one identifier string for each DMA specifier in + the dmas property. The specific strings that can be used + are defined in the binding of the DMA client device. + Multiple DMA specifiers can be used to represent + alternatives and in this case the dma-names for those + DMA specifiers must be identical (see examples). + +Examples: + +1. A device with one DMA read channel, one DMA write channel: + + i2c1: i2c@1 { + ... + dmas = <&dma 2 /* read channel */ + &dma 3>; /* write channel */ + dma-names = "rx", "tx" + ... + }; + +2. A single read-write channel with three alternative DMA controllers: + + dmas = <&dma1 5 + &dma2 7 + &dma3 2>; + dma-names = "rx-tx", "rx-tx", "rx-tx" + +3. A device with three channels, one of which has two alternatives: + + dmas = <&dma1 2 /* read channel */ + &dma1 3 /* write channel */ + &dma2 0 /* error read */ + &dma3 0>; /* alternative error read */ + dma-names = "rx", "tx", "error", "error"; |