linux-kernel - Re: [PATCH v3 3/4] dt-bindings: reserved-memory: Make DMA-BUF CMA heap DT-configurable

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Message-ID: <20210114140138.GA2796092@robh.at.kernel.org>
Date:   Thu, 14 Jan 2021 08:01:38 -0600
From:   Rob Herring <robh@...nel.org>
To:     Minchan Kim <minchan@...nel.org>
Cc:     Andrew Morton <akpm@...ux-foundation.org>,
        linux-mm <linux-mm@...ck.org>,
        LKML <linux-kernel@...r.kernel.org>, hyesoo.yu@...sung.com,
        david@...hat.com, mhocko@...e.com, surenb@...gle.com,
        pullip.cho@...sung.com, joaodias@...gle.com, hridya@...gle.com,
        john.stultz@...aro.org, sumit.semwal@...aro.org,
        linux-media@...r.kernel.org, devicetree@...r.kernel.org,
        hch@...radead.org, linaro-mm-sig@...ts.linaro.org
Subject: Re: [PATCH v3 3/4] dt-bindings: reserved-memory: Make DMA-BUF CMA
 heap DT-configurable

On Tue, Jan 12, 2021 at 05:21:42PM -0800, Minchan Kim wrote:
> From: Hyesoo Yu <hyesoo.yu@...sung.com>
> 
> Document devicetree binding for chunk cma heap on dma heap framework.
> 
> The DMA chunk heap supports the bulk allocation of higher order pages.

Why do we need this? What does this do that CMA doesn't?

With a CMA area I can believe a carve out is a common, OS independent 
thing. This looks too closely tied to some Linux thing to go into DT.

> 
> Signed-off-by: Hyesoo Yu <hyesoo.yu@...sung.com>
> Signed-off-by: Minchan Kim <minchan@...nel.org>
> Signed-off-by: Hridya Valsaraju <hridya@...gle.com>
> Change-Id: I8fb231e5a8360e2d8f65947e155b12aa664dde01

Drop this.

> ---
>  .../reserved-memory/dma_heap_chunk.yaml       | 58 +++++++++++++++++++
>  1 file changed, 58 insertions(+)
>  create mode 100644 Documentation/devicetree/bindings/reserved-memory/dma_heap_chunk.yaml
> 
> diff --git a/Documentation/devicetree/bindings/reserved-memory/dma_heap_chunk.yaml b/Documentation/devicetree/bindings/reserved-memory/dma_heap_chunk.yaml
> new file mode 100644
> index 000000000000..3e7fed5fb006
> --- /dev/null
> +++ b/Documentation/devicetree/bindings/reserved-memory/dma_heap_chunk.yaml
> @@ -0,0 +1,58 @@
> +# SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause)
> +%YAML 1.2
> +---
> +$id: http://devicetree.org/schemas/reserved-memory/dma_heap_chunk.yaml#
> +$schema: http://devicetree.org/meta-schemas/core.yaml#
> +
> +title: Device tree binding for chunk heap on DMA HEAP FRAMEWORK
> +
> +description: |
> +  The DMA chunk heap is backed by the Contiguous Memory Allocator (CMA) and
> +  supports bulk allocation of fixed size pages.
> +
> +maintainers:
> +  - Hyesoo Yu <hyesoo.yu@...sung.com>
> +  - John Stultz <john.stultz@...aro.org>
> +  - Minchan Kim <minchan@...nel.org>
> +  - Hridya Valsaraju<hridya@...gle.com>

space                  ^

> +
> +
> +properties:
> +  compatible:
> +    enum:
> +      - dma_heap,chunk

The format is <vendor>,<something> and 'dma_heap' is not a vendor.

> +
> +  chunk-order:
> +    description: |
> +            order of pages that will get allocated from the chunk DMA heap.
> +    maxItems: 1
> +
> +  size:
> +    maxItems: 1
> +
> +  alignment:
> +    maxItems: 1
> +
> +required:
> +  - compatible
> +  - size
> +  - alignment
> +  - chunk-order
> +
> +additionalProperties: false
> +
> +examples:
> +  - |
> +    reserved-memory {
> +        #address-cells = <2>;
> +        #size-cells = <1>;
> +
> +        chunk_memory: chunk_memory {
> +            compatible = "dma_heap,chunk";
> +            size = <0x3000000>;
> +            alignment = <0x0 0x00010000>;
> +            chunk-order = <4>;
> +        };
> +    };
> +
> +
> -- 
> 2.30.0.284.gd98b1dd5eaa7-goog
>