linux-kernel - Re: [PATCH v3 1/3] dt-bindings: spi: renesas,rzv2h-rspi: allow multiple DMAs

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Message-ID: <20260129-thigh-yoyo-b1e6cf9d455d@spud>
Date: Thu, 29 Jan 2026 17:44:59 +0000
From: Conor Dooley <conor@...nel.org>
To: Cosmin Tanislav <cosmin-gabriel.tanislav.xa@...esas.com>
Cc: Fabrizio Castro <fabrizio.castro.jz@...esas.com>,
	Mark Brown <broonie@...nel.org>, Rob Herring <robh@...nel.org>,
	Krzysztof Kozlowski <krzk+dt@...nel.org>,
	Conor Dooley <conor+dt@...nel.org>,
	Geert Uytterhoeven <geert+renesas@...der.be>,
	Magnus Damm <magnus.damm@...il.com>, linux-spi@...r.kernel.org,
	linux-renesas-soc@...r.kernel.org, devicetree@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH v3 1/3] dt-bindings: spi: renesas,rzv2h-rspi: allow
 multiple DMAs

On Wed, Jan 28, 2026 at 11:51:30PM +0200, Cosmin Tanislav wrote:
> All supported SoCs have multiple DMA controllers that can be used with
> the RSPI peripheral. The current bindings only allow a single pair of RX
> and TX DMAs.
> 
> The DMA core allows specifying multiple DMAs with the same name, and it
> will pick the first available one.
> 
> There is an exception in the base dt-schema rules specifically for
> allowing this behavior (dtschema/schemas/dma/dma.yaml).
> 
> dma-names:
>   anyOf:
>     - uniqueItems: true
>     - items:
>         # Hack around Renesas bindings which repeat entries to support
>         # multiple possible DMA providers
>         enum: [rx, tx]
> 
> Allow multiple DMAs to have the same name and only restrict the possible
> names of the DMA channels, not their count.
> 
> For RZ/T2H and RZ/N2H SoCs, limit the number of DMA channels to 6, as
> they have 3 DMA controllers.

What's the rationale behind not setting minItems to 6 here

> 
> For RZ/V2H and RZ/V2N SoCs, limit the number of DMA channels to 10, as
> they have 5 DMA controllers.

and to 10 here? Do any of the spi controllers on these SoCs not have the
ability to use all of the available dma controllers?

> 
> Signed-off-by: Cosmin Tanislav <cosmin-gabriel.tanislav.xa@...esas.com>
> ---
> 
> V3:
>  * impose proper maxItems for each device
>  * impose maxItems for dmas property
> 
> V2:
>  * new patch
> 
>  .../bindings/spi/renesas,rzv2h-rspi.yaml         | 16 +++++++++++++---
>  1 file changed, 13 insertions(+), 3 deletions(-)
> 
> diff --git a/Documentation/devicetree/bindings/spi/renesas,rzv2h-rspi.yaml b/Documentation/devicetree/bindings/spi/renesas,rzv2h-rspi.yaml
> index a588b112e11e..cf8b733b766d 100644
> --- a/Documentation/devicetree/bindings/spi/renesas,rzv2h-rspi.yaml
> +++ b/Documentation/devicetree/bindings/spi/renesas,rzv2h-rspi.yaml
> @@ -58,12 +58,16 @@ properties:
>        - const: tresetn
>  
>    dmas:
> -    maxItems: 2
> +    minItems: 2
> +    maxItems: 10
>  
>    dma-names:
> +    minItems: 2
> +    maxItems: 10
>      items:
> -      - const: rx
> -      - const: tx
> +      enum:
> +        - rx
> +        - tx
>  
>    power-domains:
>      maxItems: 1
> @@ -121,6 +125,12 @@ allOf:
>          resets: false
>          reset-names: false
>  
> +        dmas:
> +          maxItems: 6
> +
> +        dma-names:
> +          maxItems: 6
> +
>  unevaluatedProperties: false
>  
>  examples:
> -- 
> 2.52.0

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