Re: [PATCH 1/9] dt-bindings: dma: brcm,bcm2835-dma: Add BCM2711 and BCM2712

[Conor Dooley <conor@kernel.org>]

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On Mon, Nov 02, 2026 at 09:06:51AM +0000, Peter Robinson wrote:
> Add compatibles for the BCM2711 40-bit DMA4 channels, which are
> described by a separate node covering channels 11-14, and for the
> BCM2712 DMA controllers. The register address of a node identifies its
> first channel, allowing a controller to be split across nodes.
> 
> Signed-off-by: Peter Robinson <pbrobinson@gmail.com>
> Cc: Rob Herring <robh@kernel.org>
> Cc: Krzysztof Kozlowski <krzk+dt@kernel.org>
> Cc: Conor Dooley <conor+dt@kernel.org>
> 
> ---
>  .../bindings/dma/brcm,bcm2835-dma.yaml        | 31 +++++++++++++++++--
>  1 file changed, 29 insertions(+), 2 deletions(-)
> 
> diff --git a/Documentation/devicetree/bindings/dma/brcm,bcm2835-dma.yaml b/Documentation/devicetree/bindings/dma/brcm,bcm2835-dma.yaml
> index c9b9a5490826c..31d97a10a0ea9 100644
> --- a/Documentation/devicetree/bindings/dma/brcm,bcm2835-dma.yaml
> +++ b/Documentation/devicetree/bindings/dma/brcm,bcm2835-dma.yaml
> @@ -9,18 +9,27 @@ title: BCM2835 DMA controller
>  maintainers:
>    - Nicolas Saenz Julienne <nsaenz@kernel.org>
>  
> -description:
> +description: |
>    The BCM2835 DMA controller has 16 channels in total. Only the lower
>    13 channels have an associated IRQ. Some arbitrary channels are used by the
>    VideoCore firmware (1,3,6,7 in the current firmware version). The channels
>    0, 2 and 3 have special functionality and should not be used by the driver.
>  
> +  BCM2711 channels 11 to 14 are 40-bit capable DMA4 channels, described by a
> +  separate brcm,bcm2711-dma node. BCM2712 has 40-bit addressing on all
> +  channels, with channels 6 to 11 being DMA4 channels. A controller may be
> +  split across several nodes, the register address identifies the first
> +  channel of a node.

Uh no, a device should not be split across different nodes. This should
not be needed, why can't your driver handle the upper channels having
different capabilities?

Thanks,
Conor.

> +
>  allOf:
>    - $ref: dma-controller.yaml#
>  
>  properties:
>    compatible:
> -    const: brcm,bcm2835-dma
> +    enum:
> +      - brcm,bcm2835-dma
> +      - brcm,bcm2711-dma
> +      - brcm,bcm2712-dma
>  
>    reg:
>      maxItems: 1
> @@ -99,4 +108,22 @@ examples:
>          brcm,dma-channel-mask = <0x7f35>;
>      };
>  
> +  - |
> +    #include <dt-bindings/interrupt-controller/arm-gic.h>
> +
> +    dma-controller@7e007b00 {
> +      compatible = "brcm,bcm2711-dma";
> +      reg = <0x7e007b00 0x400>;
> +      interrupts = <GIC_SPI 89 IRQ_TYPE_LEVEL_HIGH>,
> +                   <GIC_SPI 90 IRQ_TYPE_LEVEL_HIGH>,
> +                   <GIC_SPI 91 IRQ_TYPE_LEVEL_HIGH>,
> +                   <GIC_SPI 92 IRQ_TYPE_LEVEL_HIGH>;
> +      interrupt-names = "dma11",
> +                        "dma12",
> +                        "dma13",
> +                        "dma14";
> +      #dma-cells = <1>;
> +      brcm,dma-channel-mask = <0x7000>;
> +    };
> +
>  ...
> -- 
> 2.56.0
> 

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