Re: [PATCH 06/11] dt-bindings: dma: stm32-dma3: introduce st,axi-max-burst-len property

Rob Herring
2024-10-10T18:16:47Z

On Thu, Oct 10, 2024 at 04:27:56PM +0200, Amelie Delaunay wrote:
> DMA3 maximum burst length (in unit of beat) may be restricted depending
> on bus interconnect.
>
> As mentionned in STM32MP2 reference manual [1], "the maximum allowed AXI
> burst length is 16. The user must set [S|D]BL_1 lower or equal to 15
> if the Source/Destination allocated port is AXI (if [S|D]AP=0)".

This should be implied by the SoC specific compatible.

>
> Introduce st,axi-max-burst-len. If used, it will clamp the burst length
> to that value if AXI port is used, if not, the maximum burst length value
> supported by DMA3 is used.
>
> [1] https://www.st.com/resource/en/reference_manual/rm0457-stm32mp2325xx-advanced-armbased-3264bit-mpus-stmicroelectronics.pdf
>
> Signed-off-by: Amelie Delaunay <amelie.delaunay@foss.st.com>
> ---
> .../devicetree/bindings/dma/stm32/st,stm32-dma3.yaml | 11 +++++++++++
> 1 file changed, 11 insertions(+)
>
> diff --git a/Documentation/devicetree/bindings/dma/stm32/st,stm32-dma3.yaml b/Documentation/devicetree/bindings/dma/stm32/st,stm32-dma3.yaml
> index 38c30271f732e0c8da48199a224a88bb647eeca7..90ad70bb24eb790afe72bf2085478fa4cec60b94 100644
> --- a/Documentation/devicetree/bindings/dma/stm32/st,stm32-dma3.yaml
> +++ b/Documentation/devicetree/bindings/dma/stm32/st,stm32-dma3.yaml
> @@ -51,6 +51,16 @@ properties:
> power-domains:
> maxItems: 1
>
> + st,axi-max-burst-len:
> + description: |
> + Restrict AXI burst length in unit of beat by value specified in this property.
> + The value specified in this property is clamped to the maximum burst length supported by DMA3.
> + If this property is missing, the maximum burst length supported by DMA3 is used.
> + $ref: /schemas/types.yaml#/definitions/uint32
> + minimum: 1
> + maximum: 256
> + default: 64
> +
> "#dma-cells":
> const: 3
> description: |
> @@ -137,5 +147,6 @@ examples:
> <GIC_SPI 48 IRQ_TYPE_LEVEL_HIGH>;
> clocks = <&rcc CK_BUS_HPDMA1>;
> #dma-cells = <3>;
> + st,axi-max-burst-len = <16>;
> };
> ...
>
> --
> 2.25.1
>