110 lines
3.3 KiB
Plaintext
Executable file
110 lines
3.3 KiB
Plaintext
Executable file
* Generic DMA Controller and DMA request bindings
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Generic binding to provide a way for a driver using DMA Engine to retrieve the
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DMA request or channel information that goes from a hardware device to a DMA
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controller.
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* DMA controller
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Required property:
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- #dma-cells: Must be at least 1. Used to provide DMA controller
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specific information. See DMA client binding below for
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more details.
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Optional properties:
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- dma-channels: Number of DMA channels supported by the controller.
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- dma-requests: Number of DMA request signals supported by the
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controller.
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Example:
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dma: dma@48000000 {
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compatible = "ti,omap-sdma";
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reg = <0x48000000 0x1000>;
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interrupts = <0 12 0x4
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0 13 0x4
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0 14 0x4
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0 15 0x4>;
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#dma-cells = <1>;
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dma-channels = <32>;
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dma-requests = <127>;
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};
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* DMA router
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DMA routers are transparent IP blocks used to route DMA request lines from
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devices to the DMA controller. Some SoCs (like TI DRA7x) have more peripherals
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integrated with DMA requests than what the DMA controller can handle directly.
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Required property:
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- dma-masters: phandle of the DMA controller or list of phandles for
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the DMA controllers the router can direct the signal to.
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- #dma-cells: Must be at least 1. Used to provide DMA router specific
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information. See DMA client binding below for more
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details.
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Optional properties:
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- dma-requests: Number of incoming request lines the router can handle.
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- In the node pointed by the dma-masters:
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- dma-requests: The router driver might need to look for this in order
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to configure the routing.
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Example:
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sdma_xbar: dma-router@4a002b78 {
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compatible = "ti,dra7-dma-crossbar";
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reg = <0x4a002b78 0xfc>;
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#dma-cells = <1>;
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dma-requests = <205>;
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ti,dma-safe-map = <0>;
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dma-masters = <&sdma>;
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};
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* DMA client
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Client drivers should specify the DMA property using a phandle to the controller
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followed by DMA controller specific data.
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Required property:
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- dmas: List of one or more DMA specifiers, each consisting of
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- A phandle pointing to DMA controller node
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- A number of integer cells, as determined by the
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#dma-cells property in the node referenced by phandle
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containing DMA controller specific information. This
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typically contains a DMA request line number or a
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channel number, but can contain any data that is
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required for configuring a channel.
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- dma-names: Contains one identifier string for each DMA specifier in
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the dmas property. The specific strings that can be used
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are defined in the binding of the DMA client device.
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Multiple DMA specifiers can be used to represent
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alternatives and in this case the dma-names for those
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DMA specifiers must be identical (see examples).
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Examples:
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1. A device with one DMA read channel, one DMA write channel:
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i2c1: i2c@1 {
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...
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dmas = <&dma 2 /* read channel */
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&dma 3>; /* write channel */
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dma-names = "rx", "tx";
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...
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};
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2. A single read-write channel with three alternative DMA controllers:
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dmas = <&dma1 5
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&dma2 7
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&dma3 2>;
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dma-names = "rx-tx", "rx-tx", "rx-tx";
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3. A device with three channels, one of which has two alternatives:
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dmas = <&dma1 2 /* read channel */
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&dma1 3 /* write channel */
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&dma2 0 /* error read */
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&dma3 0>; /* alternative error read */
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dma-names = "rx", "tx", "error", "error";
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