linux-kernel - Re: [PATCH v3 02/10] dt-bindings: iio: dac: axi-dac: add ad3552r axi variant

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Message-ID: <odkqq4oikux4766unjrixnw35qx7sa24byk5ob4bm7njq5bl3l@4zx4iyfwnsum>
Date: Sun, 22 Sep 2024 22:59:11 +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 02/10] dt-bindings: iio: dac: axi-dac: add ad3552r axi
 variant

On Thu, Sep 19, 2024 at 11:19:58AM +0200, Angelo Dureghello wrote:
> From: Angelo Dureghello <adureghello@...libre.com>
> 
> Add a new compatible and related bindigns for the fpga-based
> "ad3552r" AXI IP core, a variant of the generic AXI DAC IP.
> 
> The AXI "ad3552r" IP is a very similar HDL (fpga) variant of the
> generic AXI "DAC" IP, intended to control ad3552r and similar chips,
> mainly to reach high speed transfer rates using an additional QSPI
> DDR interface.
> 
> The ad3552r device is defined as a child of the AXI DAC, that in
> this case is acting as an SPI controller.


So who acts as an SPI controller? adi,axi-ad3552r? Why this is not
reflected in the binding?

> 
> Signed-off-by: Angelo Dureghello <adureghello@...libre.com>
> ---
>  .../devicetree/bindings/iio/dac/adi,axi-dac.yaml   | 40 ++++++++++++++++++++--
>  1 file changed, 37 insertions(+), 3 deletions(-)
> 
> diff --git a/Documentation/devicetree/bindings/iio/dac/adi,axi-dac.yaml b/Documentation/devicetree/bindings/iio/dac/adi,axi-dac.yaml
> index a55e9bfc66d7..6cf0c2cb84e7 100644
> --- a/Documentation/devicetree/bindings/iio/dac/adi,axi-dac.yaml
> +++ b/Documentation/devicetree/bindings/iio/dac/adi,axi-dac.yaml
> @@ -19,11 +19,13 @@ description: |
>    memory via DMA into the DAC.
>  
>    https://wiki.analog.com/resources/fpga/docs/axi_dac_ip
> +  https://analogdevicesinc.github.io/hdl/library/axi_ad3552r/index.html
>  
>  properties:
>    compatible:
>      enum:
>        - adi,axi-dac-9.1.b
> +      - adi,axi-ad3552r
>  
>    reg:
>      maxItems: 1
> @@ -41,22 +43,54 @@ properties:
>    '#io-backend-cells':
>      const: 0
>  
> +  '#address-cells':
> +    const: 1
> +
> +  '#size-cells':
> +    const: 0
> +
>  required:
>    - compatible
>    - dmas
>    - reg
>    - clocks
>  
> +patternProperties:
> +  "^.*@([0-9])$":

No need for ()

but this is pattern is quite permissive, so looks like you want to
achieve something else. Maybe spi controller? Not sure, I am just
guessing because empty example does not help me.

> +    type: object
> +    additionalProperties: true

No, this cannot be true.

> +    properties:
> +      io-backends:
> +        description: |
> +          AXI backend reference
> +    required:
> +      - io-backends

I don't get the point. Nodes with only one property are not really
useful.

> +
>  additionalProperties: false
>  
>  examples:
>    - |
>      dac@...00000 {
> -        compatible = "adi,axi-dac-9.1.b";
> -        reg = <0x44a00000 0x10000>;
> -        dmas = <&tx_dma 0>;
> +      compatible = "adi,axi-dac-9.1.b";
> +      reg = <0x44a00000 0x10000>;

Why are you changing this? It's even messier now - other example uses
different indentayion...

> +      dmas = <&tx_dma 0>;
> +      dma-names = "tx";
> +      #io-backend-cells = <0>;
> +      clocks = <&axi_clk>;
> +    };
> +
> +  - |
> +    axi_dac: spi@...70000 {
> +        compatible = "adi,axi-ad3552r";
> +        reg = <0x44a70000 0x1000>;
> +        dmas = <&dac_tx_dma 0>;
>          dma-names = "tx";
>          #io-backend-cells = <0>;
>          clocks = <&axi_clk>;
> +
> +        #address-cells = <1>;
> +        #size-cells = <0>;
> +
> +        /* DAC devices */

Your schema must be complete, example as well (minus repetitive pieces).

Best regards,
Krzysztof