linux-kernel - Re: [PATCH v1] dt-bindings: dma: st-stm32-dmamux: Add description for dma-cell values

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Message-ID: <CADRqkYAg5k3xM81-qBBiiLsvVdJCGdCVyAJgEexMw4s-1PeQkQ@mail.gmail.com>
Date: Fri, 6 Dec 2024 05:40:16 -0500
From: Ken Sloat <ksloat@...nersoftsolutions.com>
To: Amelie Delaunay <amelie.delaunay@...s.st.com>
Cc: Krzysztof Kozlowski <krzk@...nel.org>, linux-kernel@...r.kernel.org, 
	linux-arm-kernel@...ts.infradead.org, devicetree@...r.kernel.org, 
	linux-stm32@...md-mailman.stormreply.com, dmaengine@...r.kernel.org, 
	alexandre.torgue@...s.st.com, mcoquelin.stm32@...il.com, conor+dt@...nel.org, 
	krzk+dt@...nel.org, robh@...nel.org, vkoul@...nel.org, 
	Ken Sloat <ksloat@...nersoftsolutions.com>
Subject: Re: [PATCH v1] dt-bindings: dma: st-stm32-dmamux: Add description for
 dma-cell values

Hi Amelie,

Thanks for reviewing

On Thu, Dec 5, 2024 at 1:06 PM Amelie Delaunay
<amelie.delaunay@...s.st.com> wrote:
>
>
> On 12/5/24 17:09, Krzysztof Kozlowski wrote:
> > On 05/12/2024 17:07, Ken Sloat wrote:
> >>>> + 1. The mux input number/line for the request
> >>>> + 2. Bitfield representing DMA channel configuration that is passed
> >>>> + to the real DMA controller
> >>>> + 3. Bitfield representing device dependent DMA features passed to
> >>>> + the real DMA controller
> >>>> +
> >>>> + For bitfield definitions of cells 2 and 3, see the associated
> >>>> + bindings doc for the actual DMA controller the mux is connected
> >>>
> >>> This does not sound right. This is the binding for DMA controller, so
> >>> you are saying "please look at itself". I suggest to drop this as well.
> >>>
> >>
> >> While logically it is the DMA controller, this doc is specifically for
> >> the mux - the DMA controller has its own driver and binding docs in
> >> Documentation/devicetree/bindings/dma/stm32/st,stm32-dma.yaml
> >>
> >> I can reference st,stm32-dma.yaml directly, but I was unsure if this
> >> mux IP was used with another DMA controller from ST on a different
> >> SoC.
> >>
> >> What do you suggest here?
> >
> > Thanks for explanation, I think it is fine.
> >
> > Best regards,
> > Krzysztof
>
> This description was lost when STM32 DMAMUX binding txt file was
> converted to yaml:
> 0b7c446fa9f7 ("dt-bindings: dma: Convert stm32 DMAMUX bindings to
> json-schema")
>
> -- #dma-cells:  Should be set to <3>.
> -               First parameter is request line number.
> -               Second is DMA channel configuration
> -               Third is Fifo threshold

Thanks for the info, this aligns with what I have

> -               For more details about the three cells, please see
> -               stm32-dma.txt documentation binding file
>
>
> stm32-dmamux exclusively muxes stm32-dma channels. It is not used with
> other ST DMA controllers (STM32 MDMA, STM32 DMA3).
>
> So it is fine to refer to st,stm32-dma.yaml.

Ok, I can add that on v2

>
> Regards,
> Amelie

-- 
Sincerely,
Ken Sloat