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Florian Meier96286b52014-01-06 20:18:24 +01001* BCM2835 DMA controller
2
3The BCM2835 DMA controller has 16 channels in total.
4Only the lower 13 channels have an associated IRQ.
5Some arbitrary channels are used by the firmware
6(1,3,6,7 in the current firmware version).
7The channels 0,2 and 3 have special functionality
8and should not be used by the driver.
9
10Required 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
21Example:
22
23dma: 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
44DMA clients connected to the BCM2835 DMA controller must use the format
45described in the dma.txt file, using a two-cell specifier for each channel.
46
47Example:
48
49bcm2835_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};