About Kernel Documentation Linux Kernel Contact Linux Resources Linux Blog

Documentation / devicetree / bindings / dma / dma.txt




Custom Search

Based on kernel version 3.13. Page generated on 2014-01-20 22:00 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 requests 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	
35	* DMA client
36	
37	Client drivers should specify the DMA property using a phandle to the controller
38	followed by DMA controller specific data.
39	
40	Required property:
41	- dmas:			List of one or more DMA specifiers, each consisting of
42				- A phandle pointing to DMA controller node
43				- A number of integer cells, as determined by the
44				  #dma-cells property in the node referenced by phandle
45				  containing DMA controller specific information. This
46				  typically contains a DMA request line number or a
47				  channel number, but can contain any data that is used
48				  required for configuring a channel.
49	- dma-names: 		Contains one identifier string for each DMA specifier in
50				the dmas property. The specific strings that can be used
51				are defined in the binding of the DMA client device.
52				Multiple DMA specifiers can be used to represent
53				alternatives and in this case the dma-names for those
54				DMA specifiers must be identical (see examples).
55	
56	Examples:
57	
58	1. A device with one DMA read channel, one DMA write channel:
59	
60		i2c1: i2c@1 {
61			...
62			dmas = <&dma 2		/* read channel */
63				&dma 3>;	/* write channel */
64			dma-names = "rx", "tx";
65			...
66		};
67	
68	2. A single read-write channel with three alternative DMA controllers:
69	
70		dmas = <&dma1 5
71			&dma2 7
72			&dma3 2>;
73		dma-names = "rx-tx", "rx-tx", "rx-tx";
74	
75	3. A device with three channels, one of which has two alternatives:
76	
77		dmas = <&dma1 2			/* read channel */
78			&dma1 3			/* write channel */
79			&dma2 0			/* error read */
80			&dma3 0>;		/* alternative error read */
81		dma-names = "rx", "tx", "error", "error";
Hide Line Numbers
About Kernel Documentation Linux Kernel Contact Linux Resources Linux Blog

Information is copyright its respective author. All material is available from the Linux Kernel Source distributed under a GPL License. This page is provided as a free service by mjmwired.net.