Re: [PATCH 2/3] spi: dt-bindings: Add num-cs property for mpfs-spi

[Conor Dooley]

On Thu, May 02, 2024 at 03:34:09PM +0100, Prajna Rajendra Kumar wrote:
> The PolarFire SoC SPI controller supports multiple chip selects,but in
> the MSS, only one CS line is physically wired. To reflect this hardware
> limitation in the device tree, the binding enforces that the 'num-cs'
> property defaults to 1 and cannot exceed 1 unless additional
> chip select lines are explicitly defined using GPIO descriptors.
> 
> Fixes: 2da187304e55 ("spi: add bindings for microchip mpfs spi")
> Signed-off-by: Prajna Rajendra Kumar <prajna.rajendrakumar@xxxxxxxxxxxxx>
> ---
>  .../bindings/spi/microchip,mpfs-spi.yaml      | 19 ++++++++++++++++---
>  1 file changed, 16 insertions(+), 3 deletions(-)
> 
> diff --git a/Documentation/devicetree/bindings/spi/microchip,mpfs-spi.yaml b/Documentation/devicetree/bindings/spi/microchip,mpfs-spi.yaml
> index 74a817cc7d94..19951951fdd6 100644
> --- a/Documentation/devicetree/bindings/spi/microchip,mpfs-spi.yaml
> +++ b/Documentation/devicetree/bindings/spi/microchip,mpfs-spi.yaml
> @@ -13,9 +13,6 @@ description:
>  maintainers:
>    - Conor Dooley <conor.dooley@xxxxxxxxxxxxx>
>  
> -allOf:
> -  - $ref: spi-controller.yaml#
> -
>  properties:
>    compatible:
>      oneOf:
> @@ -43,6 +40,22 @@ required:
>    - interrupts
>    - clocks
>  
> +allOf:
> +  - $ref: spi-controller.yaml#
> +  - if:
> +      properties:
> +        compatible:
> +          contains:
> +            const: microchip,mpfs-spi
> +      not:
> +        required:
> +          - cs-gpios
> +    then:
> +      properties:
> +        num-cs:
> +          default: 1
> +          maximum: 1

I think this isn't quite right actually. The default for num-cs should
be 1, regardless of whether cs-gpios are used or not, only the maximum
is affected by using GPIOs for chip select.

> +
>  unevaluatedProperties: false
>  
>  examples:
> -- 
> 2.25.1
>

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