brcm,bcm2835-dma.txt (2059B)
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};