xref: /freebsd/sys/contrib/device-tree/Bindings/dma/brcm,bcm2835-dma.txt (revision 7ab1a32cd43cbae61ad4dd435d6a482bbf61cb52) 
1* 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- interrupt-names: Should contain the names of the interrupt
16		   in the form "dmaXX".
17		   Use "dma-shared-all" for the common interrupt line
18		   that is shared by all dma channels.
19- #dma-cells: Must be <1>, the cell in the dmas property of the
20		client device represents the DREQ number.
21- brcm,dma-channel-mask: Bit mask representing the channels
22			 not used by the firmware in ascending order,
23			 i.e. first channel corresponds to LSB.
24
25Example:
26
27dma: dma@7e007000 {
28	compatible = "brcm,bcm2835-dma";
29	reg = <0x7e007000 0xf00>;
30	interrupts = <1 16>,
31		     <1 17>,
32		     <1 18>,
33		     <1 19>,
34		     <1 20>,
35		     <1 21>,
36		     <1 22>,
37		     <1 23>,
38		     <1 24>,
39		     <1 25>,
40		     <1 26>,
41		     /* dma channel 11-14 share one irq */
42		     <1 27>,
43		     <1 27>,
44		     <1 27>,
45		     <1 27>,
46		     /* unused shared irq for all channels */
47		     <1 28>;
48	interrupt-names = "dma0",
49			  "dma1",
50			  "dma2",
51			  "dma3",
52			  "dma4",
53			  "dma5",
54			  "dma6",
55			  "dma7",
56			  "dma8",
57			  "dma9",
58			  "dma10",
59			  "dma11",
60			  "dma12",
61			  "dma13",
62			  "dma14",
63			  "dma-shared-all";
64
65	#dma-cells = <1>;
66	brcm,dma-channel-mask = <0x7f35>;
67};
68
69
70DMA clients connected to the BCM2835 DMA controller must use the format
71described in the dma.txt file, using a two-cell specifier for each channel.
72
73Example:
74
75bcm2835_i2s: i2s@7e203000 {
76	compatible = "brcm,bcm2835-i2s";
77	reg = <	0x7e203000 0x24>;
78	clocks = <&clocks BCM2835_CLOCK_PCM>;
79
80	dmas = <&dma 2>,
81	       <&dma 3>;
82	dma-names = "tx", "rx";
83};
84