84 lines
2.0 KiB
Plaintext
84 lines
2.0 KiB
Plaintext
* BCM2835 DMA controller
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The BCM2835 DMA controller has 16 channels in total.
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Only the lower 13 channels have an associated IRQ.
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Some arbitrary channels are used by the firmware
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(1,3,6,7 in the current firmware version).
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The channels 0,2 and 3 have special functionality
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and should not be used by the driver.
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Required properties:
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- compatible: Should be "brcm,bcm2835-dma".
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- reg: Should contain DMA registers location and length.
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- interrupts: Should contain the DMA interrupts associated
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to the DMA channels in ascending order.
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- interrupt-names: Should contain the names of the interrupt
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in the form "dmaXX".
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Use "dma-shared-all" for the common interrupt line
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that is shared by all dma channels.
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- #dma-cells: Must be <1>, the cell in the dmas property of the
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client device represents the DREQ number.
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- brcm,dma-channel-mask: Bit mask representing the channels
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not used by the firmware in ascending order,
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i.e. first channel corresponds to LSB.
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Example:
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dma: dma@7e007000 {
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compatible = "brcm,bcm2835-dma";
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reg = <0x7e007000 0xf00>;
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interrupts = <1 16>,
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<1 17>,
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<1 18>,
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<1 19>,
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<1 20>,
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<1 21>,
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<1 22>,
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<1 23>,
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<1 24>,
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<1 25>,
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<1 26>,
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/* dma channel 11-14 share one irq */
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<1 27>,
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<1 27>,
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<1 27>,
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<1 27>,
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/* unused shared irq for all channels */
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<1 28>;
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interrupt-names = "dma0",
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"dma1",
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"dma2",
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"dma3",
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"dma4",
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"dma5",
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"dma6",
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"dma7",
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"dma8",
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"dma9",
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"dma10",
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"dma11",
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"dma12",
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"dma13",
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"dma14",
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"dma-shared-all";
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#dma-cells = <1>;
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brcm,dma-channel-mask = <0x7f35>;
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};
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DMA clients connected to the BCM2835 DMA controller must use the format
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described in the dma.txt file, using a two-cell specifier for each channel.
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Example:
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bcm2835_i2s: i2s@7e203000 {
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compatible = "brcm,bcm2835-i2s";
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reg = < 0x7e203000 0x24>;
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clocks = <&clocks BCM2835_CLOCK_PCM>;
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dmas = <&dma 2>,
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<&dma 3>;
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dma-names = "tx", "rx";
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};
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