linux-kernel - Re: [PATCH v2 1/3] dt-bindings: spi: renesas,rzv2h-rspi: allow multiple DMAs

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Message-ID: <20260128-sequence-platypus-59ae3318318a@spud>
Date: Wed, 28 Jan 2026 18:08:43 +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 v2 1/3] dt-bindings: spi: renesas,rzv2h-rspi: allow
 multiple DMAs

On Tue, Jan 27, 2026 at 10:17:04PM +0200, Cosmin Tanislav wrote:
> The Renesas RZ/T2H and RZ/N2H 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.
> 
> Allow multiple DMAs by only restricting the possible names of the DMA
> channels.
> 

> All '.*-names$' properties must conform to the string-array.yaml
> meta-schema, which requires both minItems and maxItems properties to be
> present before the items can be a schema. Otherwise, the items need to
> be an array.

Why is this in the commit message?

> 
> Declare a generous maxItems of 32, which should be enough for 16 DMA
> controllers, so that we don't have to update this value ever again, even
> if currently the maximum number of DMA controllers on a Renesas SoC is
> 5.

Huh, No. The binding should constrain this to fit what the actual
devices do.


> 
> Signed-off-by: Cosmin Tanislav <cosmin-gabriel.tanislav.xa@...esas.com>
> ---
> 
> V2:
>  * new patch
> 
>  .../devicetree/bindings/spi/renesas,rzv2h-rspi.yaml    | 10 ++++++----
>  1 file changed, 6 insertions(+), 4 deletions(-)
> 
> diff --git a/Documentation/devicetree/bindings/spi/renesas,rzv2h-rspi.yaml b/Documentation/devicetree/bindings/spi/renesas,rzv2h-rspi.yaml
> index a588b112e11e..383e97f0dabd 100644
> --- a/Documentation/devicetree/bindings/spi/renesas,rzv2h-rspi.yaml
> +++ b/Documentation/devicetree/bindings/spi/renesas,rzv2h-rspi.yaml
> @@ -57,13 +57,15 @@ properties:
>        - const: presetn
>        - const: tresetn
>  
> -  dmas:
> -    maxItems: 2
> +  dmas: true

This should have the same constraints as dma-names. You've now allowed
this to have 1 and 33 dmas, because there's no requirement to have
dma-names when you have dmas.

>  
>    dma-names:
> +    minItems: 2
> +    maxItems: 32
>      items:
> -      - const: rx
> -      - const: tx
> +      enum:
> +        - rx
> +        - tx

You've changed this to allow 32 dma-names, but they all need to be
called either "rx" or "tx", how is a driver meant to use dma-names to
get the second pair of dma channels? Shouldn't anything in excess of the
first two start getting numbers appended so that a driver can actually
request them?

pw-bot: changes-requested

Conor.

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