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

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Message-ID: <20240908132925.331c5175@jic23-huawei>
Date: Sun, 8 Sep 2024 13:29:25 +0100
From: Jonathan Cameron <jic23@...nel.org>
To: Angelo Dureghello <adureghello@...libre.com>
Cc: Lars-Peter Clausen <lars@...afoo.de>, Michael Hennerich
 <Michael.Hennerich@...log.com>, Nuno Sá <nuno.sa@...log.com>,
 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,
 devicetree@...r.kernel.org, linux-kernel@...r.kernel.org, David Lechner
 <dlechner@...libre.com>
Subject: Re: [PATCH v2 1/9] dt-bindings: iio: dac: ad3552r: add io-backend
 property

On Thu, 05 Sep 2024 17:17:31 +0200
Angelo Dureghello <adureghello@...libre.com> 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. 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@...libre.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@...70000 {
> +        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)>;
> +            };
> +        };
> +    };
> +
>  ...
>