[RFC PATCH 1/5] dt-bindings: dma: Add CMA Heap bindings

[Maxime Ripard]

Hi,

On Thu, Jan 30, 2025 at 01:08:57PM +0000, Florent Tomasin wrote:
> Introduce a CMA Heap dt-binding allowing custom
> CMA heap registrations.
> 
> * Note to the reviewers:
> The patch was used for the development of the protected mode
> feature in Panthor CSF kernel driver and is not initially thought
> to land in the Linux kernel. It is mostly relevant if someone
> wants to reproduce the environment of testing. Please, raise
> interest if you think the patch has value in the Linux kernel.
> 
> Signed-off-by: Florent Tomasin <florent.tomasin at arm.com>
> ---
>  .../devicetree/bindings/dma/linux,cma.yml     | 43 +++++++++++++++++++
>  1 file changed, 43 insertions(+)
>  create mode 100644 Documentation/devicetree/bindings/dma/linux,cma.yml
> 
> diff --git a/Documentation/devicetree/bindings/dma/linux,cma.yml b/Documentation/devicetree/bindings/dma/linux,cma.yml
> new file mode 100644
> index 000000000000..c532e016bbe5
> --- /dev/null
> +++ b/Documentation/devicetree/bindings/dma/linux,cma.yml
> @@ -0,0 +1,43 @@
> +# SPDX-License-Identifier: GPL-2.0-only OR BSD-2-Clause
> +%YAML 1.2
> +---
> +$id: http://devicetree.org/schemas/dma/linux-cma.yaml#
> +$schema: http://devicetree.org/meta-schemas/core.yaml#
> +
> +title: Custom Linux CMA heap
> +
> +description:
> +  The custom Linux CMA heap device tree node allows registering
> +  of multiple CMA heaps.
> +
> +  The CMA heap name will match the node name of the "memory-region".
> +
> +properties:
> +  compatible:
> +    enum:
> +      - linux,cma
> +
> +  memory-region:
> +    maxItems: 1
> +    description: |
> +      Phandle to the reserved memory node associated with the CMA Heap.
> +      The reserved memory node must follow this binding convention:
> +       - Documentation/devicetree/bindings/reserved-memory/reserved-memory.txt
> +
> +examples:
> +  - |
> +    reserved-memory {
> +      #address-cells = <2>;
> +      #size-cells = <2>;
> +
> +      custom_cma_heap: custom-cma-heap {
> +        compatible = "shared-dma-pool";
> +        reg = <0x0 0x90600000 0x0 0x1000000>;
> +        reusable;
> +      };
> +    };
> +
> +    device_cma_heap: device-cma-heap {
> +      compatible = "linux,cma";
> +      memory-region = <&custom_cma_heap>;
> +    };

Isn't it redundant with the linux,cma-default shared-dma-pool property
already?

Maxime
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