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

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Message-ID: <ats2unrml5a7vbpdrqrzowodrsfj44bnubpbujg2igk3imeklx@nrpmg5oeq3gz>
Date: Thu, 30 Jan 2025 14:28:59 +0100
From: Maxime Ripard <mripard@...nel.org>
To: Florent Tomasin <florent.tomasin@....com>
Cc: Vinod Koul <vkoul@...nel.org>, Rob Herring <robh@...nel.org>, 
	Krzysztof Kozlowski <krzk+dt@...nel.org>, Conor Dooley <conor+dt@...nel.org>, 
	Boris Brezillon <boris.brezillon@...labora.com>, Steven Price <steven.price@....com>, 
	Liviu Dudau <liviu.dudau@....com>, Maarten Lankhorst <maarten.lankhorst@...ux.intel.com>, 
	Thomas Zimmermann <tzimmermann@...e.de>, David Airlie <airlied@...il.com>, 
	Simona Vetter <simona@...ll.ch>, Sumit Semwal <sumit.semwal@...aro.org>, 
	Benjamin Gaignard <benjamin.gaignard@...labora.com>, Brian Starkey <Brian.Starkey@....com>, 
	John Stultz <jstultz@...gle.com>, "T . J . Mercier" <tjmercier@...gle.com>, 
	Christian König <christian.koenig@....com>, Matthias Brugger <matthias.bgg@...il.com>, 
	AngeloGioacchino Del Regno <angelogioacchino.delregno@...labora.com>, Yong Wu <yong.wu@...iatek.com>, dmaengine@...r.kernel.org, 
	devicetree@...r.kernel.org, linux-kernel@...r.kernel.org, dri-devel@...ts.freedesktop.org, 
	linux-media@...r.kernel.org, linaro-mm-sig@...ts.linaro.org, 
	linux-arm-kernel@...ts.infradead.org, linux-mediatek@...ts.infradead.org, nd@....com, 
	Akash Goel <akash.goel@....com>
Subject: Re: [RFC PATCH 1/5] dt-bindings: dma: Add CMA Heap bindings

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@....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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