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Documentation / devicetree / bindings / dma / dma.txt




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Based on kernel version 4.7.2. Page generated on 2016-08-22 22:41 EST.

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";
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