Re: [PATCH v2 1/9] dt-bindings: iio: dac: ad3552r: add io-backend property

[Jonathan Cameron <jic23@kernel.org>]

On Thu, 05 Sep 2024 17:17:31 +0200
Angelo Dureghello <adureghello@baylibre.com> wrote:

> From: Angelo Dureghello <adureghello@baylibre.com>
> 
> There is a version AXI DAC IP block (for FPGAs) that provides
> a physical bus for AD3552R and similar chips. This can be used
> instead of a typical SPI controller to be able to use the chip
> in ways that typical SPI controllers are not capable of.
> 
> The binding is modified so that either the device is a SPI
> peripheral or it uses an io-backend.
> 
> Signed-off-by: Angelo Dureghello <adureghello@baylibre.com>

>  
>  required:
>    - compatible
> -  - reg
> -  - spi-max-frequency
Sort of feels like both reg and spi-max-frequency
are valid things to specify. 

Maybe we have an excellent IP and dodgy wiring so want
to clamp the frequency (long term - don't need to support
in the driver today).

Maybe we have an axi_dac IP that supports multiple
front end devices?  So maybe just keep reg?
>  
>  additionalProperties: false
>  
> @@ -238,4 +254,26 @@ examples:
>              };
>          };
>      };
> +
> +  - |
> +    backend: axi_dac@44a70000 {
> +        compatible = "adi,axi-dac-ad3552r";
> +        reg = <0x44a70000 0x1000>;
> +        dmas = <&dac_tx_dma 0>;
> +        dma-names = "tx";
> +        #io-backend-cells = <0>;
> +        clocks = <&ref_clk>;
> +        dac {
> +            compatible = "adi,ad3552r";
> +            reset-gpios = <&gpio0 92 1>;
> +            io-backends = <&backend>;
> +            #address-cells = <1>;
> +            #size-cells = <0>;
> +            channel@0 {
> +                reg = <0>;
> +                adi,output-range-microvolt = <(-10000000) (10000000)>;
> +            };
> +        };
> +    };
> +
>  ...
>