linux-kernel - Re: [PATCH 1/2] dt-bindings: dma: Add Apple ADMAC

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Message-ID: <YkW2OG3dU4YFYJEZ@matsya>
Date:   Thu, 31 Mar 2022 19:40:00 +0530
From:   Vinod Koul <vkoul@...nel.org>
To:     Martin Povišer <povik@...ebit.org>
Cc:     Martin Povišer <povik+lin@...ebit.org>,
        Hector Martin <marcan@...can.st>,
        Sven Peter <sven@...npeter.dev>,
        Rob Herring <robh+dt@...nel.org>,
        Krzysztof Kozlowski <krzk+dt@...nel.org>,
        Alyssa Rosenzweig <alyssa@...enzweig.io>,
        linux-arm-kernel@...ts.infradead.org, dmaengine@...r.kernel.org,
        devicetree@...r.kernel.org, linux-kernel@...r.kernel.org,
        Mark Kettenis <kettenis@...nbsd.org>
Subject: Re: [PATCH 1/2] dt-bindings: dma: Add Apple ADMAC

On 31-03-22, 09:06, Martin Povišer wrote:
> 
> > On 31. 3. 2022, at 8:50, Martin Povišer <povik@...ebit.org> wrote:
> > 
> >> 
> >> On 31. 3. 2022, at 7:23, Vinod Koul <vkoul@...nel.org> wrote:
> >> 
> >> On 30-03-22, 18:44, Martin Povišer wrote:
> >>> Apple's Audio DMA Controller (ADMAC) is used to fetch and store audio
> >>> samples on Apple SoCs from the "Apple Silicon" family.
> >>> 
> >>> Signed-off-by: Martin Povišer <povik+lin@...ebit.org>
> >>> ---
> >>> .../devicetree/bindings/dma/apple,admac.yaml  | 73 +++++++++++++++++++
> >>> 1 file changed, 73 insertions(+)
> >>> create mode 100644 Documentation/devicetree/bindings/dma/apple,admac.yaml
> >>> 
> >>> diff --git a/Documentation/devicetree/bindings/dma/apple,admac.yaml b/Documentation/devicetree/bindings/dma/apple,admac.yaml
> >>> new file mode 100644
> >>> index 000000000000..34f76a9a2983
> >>> --- /dev/null
> >>> +++ b/Documentation/devicetree/bindings/dma/apple,admac.yaml
> > 
> >>> +  apple,internal-irq-destination:
> >>> +    $ref: /schemas/types.yaml#/definitions/uint32
> >>> +    description: Index influencing internal routing of the IRQs
> >>> +      within the peripheral.
> >> 
> >> do you have more details for this, is this for peripheral and if so
> >> suited to be in dam-cells?
> > 
> > By peripheral I meant the DMA controller itself here. 

Dmaengine convention is that peripheral is device which we are doing dma
to/from, like audio controller/fifo here

> > Effectively the controller has four independent IRQ outputs and the driver
> > needs to know which one we are using. (It need to be the same output even
> > for different ADMAC instances on one die.)

That smells like a mux to me.. why not use dma-requests for this?

-- 
~Vinod