linux-kernel - Re: [PATCH v3 04/10] dt-bindings: iio: dac: ad3552r: add io-backend support

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Message-ID: <gojq6ardhvt6vcs2kawdhdn2cj6qbpzp4p5mjjgwsypuatm5eo@3u6k4q7le46s>
Date: Sun, 22 Sep 2024 23:02:51 +0200
From: Krzysztof Kozlowski <krzk@...nel.org>
To: Angelo Dureghello <adureghello@...libre.com>
Cc: Lars-Peter Clausen <lars@...afoo.de>, 
	Michael Hennerich <Michael.Hennerich@...log.com>, Nuno Sa <nuno.sa@...log.com>, 
	Jonathan Cameron <jic23@...nel.org>, Rob Herring <robh@...nel.org>, 
	Krzysztof Kozlowski <krzk+dt@...nel.org>, Conor Dooley <conor+dt@...nel.org>, 
	Olivier Moysan <olivier.moysan@...s.st.com>, linux-iio@...r.kernel.org, linux-kernel@...r.kernel.org, 
	devicetree@...r.kernel.org, dlechner@...libre.com
Subject: Re: [PATCH v3 04/10] dt-bindings: iio: dac: ad3552r: add io-backend
 support

On Thu, Sep 19, 2024 at 11:20:00AM +0200, Angelo Dureghello wrote:
> From: Angelo Dureghello <adureghello@...libre.com>
> 
> There is a version AXI DAC IP block (for FPGAs) that provides
> a physical bus for AD3552R and similar chips, and acts as
> an SPI controller.
> 
> For this case, the binding is modified to include some
> additional properties.
> 
> Signed-off-by: Angelo Dureghello <adureghello@...libre.com>
> ---
>  .../devicetree/bindings/iio/dac/adi,ad3552r.yaml   | 42 ++++++++++++++++++++++
>  1 file changed, 42 insertions(+)
> 
> diff --git a/Documentation/devicetree/bindings/iio/dac/adi,ad3552r.yaml b/Documentation/devicetree/bindings/iio/dac/adi,ad3552r.yaml
> index 41fe00034742..aca4a41c2633 100644
> --- a/Documentation/devicetree/bindings/iio/dac/adi,ad3552r.yaml
> +++ b/Documentation/devicetree/bindings/iio/dac/adi,ad3552r.yaml
> @@ -60,6 +60,18 @@ properties:
>      $ref: /schemas/types.yaml#/definitions/uint32
>      enum: [0, 1, 2, 3]
>  
> +  io-backends:
> +    description: The iio backend reference.
> +      An example backend can be found at
> +        https://analogdevicesinc.github.io/hdl/library/axi_ad3552r/index.html
> +    maxItems: 1
> +
> +  adi,synchronous-mode:
> +    description: Enable waiting for external synchronization signal.
> +      Some AXI IP configuration can implement a dual-IP layout, with internal
> +      wirings for streaming synchronization.
> +    type: boolean
> +
>    '#address-cells':
>      const: 1
>  
> @@ -128,6 +140,7 @@ patternProperties:
>            - custom-output-range-config
>  
>  allOf:
> +  - $ref: /schemas/spi/spi-peripheral-props.yaml#
>    - if:
>        properties:
>          compatible:
> @@ -238,4 +251,33 @@ examples:
>              };
>          };
>      };
> +
> +  - |
> +    axi_dac: spi@...70000 {
> +        compatible = "adi,axi-ad3552r";

That is either redundant or entire example should go to the parent node,
if this device is fixed child of complex device (IOW, adi,ad3552r cannot
be used outside of adi,axi-ad3552r).


> +        reg = <0x44a70000 0x1000>;
> +        dmas = <&dac_tx_dma 0>;
> +        dma-names = "tx";
> +        #io-backend-cells = <0>;
> +        clocks = <&ref_clk>;
> +
> +        #address-cells = <1>;
> +        #size-cells = <0>;
> +
> +        dac@0 {
> +            compatible = "adi,ad3552r";
> +            reg = <0>;
> +            reset-gpios = <&gpio0 92 0>;

Use standard defines for GPIO flags.

> +            io-backends = <&axi_dac>;

Why do you need to point to the parent? How much coupled are these
devices? Child pointing to parent is not usually expected, because
that's obvious.

Best regards,
Krzysztof