Re: [PATCH v3 2/2] dt-bindings: dma: hisi: Add bindings for Hisi Ascend sdma

[Rob Herring <robh@kernel.org>]

On Thu, Aug 24, 2023 at 12:00:07PM +0800, Guo Mengqi wrote:
> Add device-tree binding documentation for the Hisi Ascend sdma
> controller.
> 
> Signed-off-by: Guo Mengqi <guomengqi3@huawei.com>
> ---
>  .../bindings/dma/hisi,ascend-sdma.yaml        | 75 +++++++++++++++++++
>  1 file changed, 75 insertions(+)
>  create mode 100644 Documentation/devicetree/bindings/dma/hisi,ascend-sdma.yaml
> 
> diff --git a/Documentation/devicetree/bindings/dma/hisi,ascend-sdma.yaml b/Documentation/devicetree/bindings/dma/hisi,ascend-sdma.yaml
> new file mode 100644
> index 000000000000..87b6132c1b4b
> --- /dev/null
> +++ b/Documentation/devicetree/bindings/dma/hisi,ascend-sdma.yaml
> @@ -0,0 +1,75 @@
> +# SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause)
> +%YAML 1.2
> +---
> +$id: http://devicetree.org/schemas/dma/hisi,ascend-sdma.yaml#
> +$schema: http://devicetree.org/meta-schemas/core.yaml#
> +
> +title: HISI Ascend System DMA (SDMA) controller
> +
> +description: |
> +  The Ascend SDMA controller is used for transferring data
> +  in system memory. It utilizes IOMMU SVA feature and accepts
> +  virtual address from user process.
> +
> +maintainers:
> +  - Guo Mengqi <guomengqi3@huawei.com>
> +
> +allOf:
> +  - $ref: dma-controller.yaml#
> +
> +properties:
> +  compatible:
> +    enum:
> +      - hisilicon,ascend310-sdma
> +      - hisilicon,ascend910-sdma
> +
> +  reg:
> +    maxItems: 1
> +
> +  '#dma-cells':
> +    const: 1
> +    description:
> +      Clients specify a single cell with channel number.
> +
> +  hisilicon,ascend-sdma-channel-map:
> +    description: |
> +      bitmap, each bit stands for a channel that is allowed to
> +      use by this system. Maximum 64 bits.
> +    $ref: /schemas/types.yaml#/definitions/uint64

Sounds like the common property dma-channel-mask. Use that.

> +
> +  iommus:
> +    maxItems: 1
> +
> +  pasid-num-bits:

Needs a vendor prefix.

> +    description: |
> +      sdma utilizes iommu sva feature to transfer user space data.

Isn't shared VA mostly a s/w concept?

> +      It acts as a basic dma controller if not bound to user space.

I don't understand what this means.

> +    const: 0x10

If only 1 value is allowed, what is the point of this property.

Rob