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

[Peter Robinson]

On Mon, 2 Nov 2026 at 19:39, Conor Dooley <conor at kernel.org> wrote:
>
> 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 at gmail.com>
> > Cc: Rob Herring <robh at kernel.org>
> > Cc: Krzysztof Kozlowski <krzk+dt at kernel.org>
> > Cc: Conor Dooley <conor+dt at 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 at 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?

This is the way it's done in the downstream kernel, unfortunately
Broadcom doesn't publish the HW details so either they'd need to
contribute the support (which they've not done since the RPi4 was
available) or I'm not sure what the other options would be. Open to
suggestions.

> 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 at 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
> >