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

[Amelie Delaunay]

On 10/10/24 20:16, Rob Herring wrote:
> 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.

I took an example from snps,dw-axi-dmac.yaml (snps,axi-max-burst-len). 
But I agree, it will be implied by st,stm32mp25-dma3 compatible in V2.
Patch 8/11 will then be dropped.

Regards,
Amelie

> > 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@xxxxxxxxxxx>
> > ---
> >   .../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