linux-kernel - Re: [PATCH 1/6] dt-bindings: pwm: amlogic: fix s4 bindings

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Date:   Wed, 8 Nov 2023 11:04:48 -0600
From:   Rob Herring <robh@...nel.org>
To:     Jerome Brunet <jbrunet@...libre.com>
Cc:     Thierry Reding <thierry.reding@...il.com>,
        Neil Armstrong <neil.armstrong@...aro.org>,
        Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>,
        Conor Dooley <conor+dt@...nel.org>,
        Kevin Hilman <khilman@...libre.com>,
        devicetree@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-amlogic@...ts.infradead.org, linux-pwm@...r.kernel.org,
        JunYi Zhao <junyi.zhao@...ogic.com>
Subject: Re: [PATCH 1/6] dt-bindings: pwm: amlogic: fix s4 bindings

On Mon, Nov 06, 2023 at 11:32:48AM +0100, Jerome Brunet wrote:
> s4 has been added to the compatible list while converting the Amlogic PWM
> binding documentation from txt to yaml.
> 
> However, on the s4, the clock bindings have different meaning compared to
> previous SoCs.
> 
> On previous SoCs the clock bindings used to describe which input the PWM
> channel multiplexer should pick among its possible parents.
> 
> This is very much tied to the driver implementation, instead of describing
> the HW for what it is. When support for the Amlogic PWM was first added,
> how to deal with clocks through DT was not as clear as it nowadays.
> The Linux driver now ignores this DT setting, but still relies on the
> hard-coded list of clock sources.
> 
> On the s4, the input multiplexer is gone. The clock bindings actually
> describe the clock as it exists, not a setting. The property has a
> different meaning, even if it is still 2 clocks and it would pass the check
> when support is actually added.
> 
> Also the s4 cannot work if the clocks are not provided, so the property no
> longer optional.
> 
> Finally, for once it makes sense to see the input as being numbered
> somehow. No need to bother with clock-names on the s4 type of PWM.
> 
> Fixes: 43a1c4ff3977 ("dt-bindings: pwm: Convert Amlogic Meson PWM binding")
> Signed-off-by: Jerome Brunet <jbrunet@...libre.com>
> ---
>  .../devicetree/bindings/pwm/pwm-amlogic.yaml  | 68 ++++++++++++++++---
>  1 file changed, 59 insertions(+), 9 deletions(-)
> 
> diff --git a/Documentation/devicetree/bindings/pwm/pwm-amlogic.yaml b/Documentation/devicetree/bindings/pwm/pwm-amlogic.yaml
> index 527864a4d855..754b70fc2db0 100644
> --- a/Documentation/devicetree/bindings/pwm/pwm-amlogic.yaml
> +++ b/Documentation/devicetree/bindings/pwm/pwm-amlogic.yaml
> @@ -9,9 +9,6 @@ title: Amlogic PWM
>  maintainers:
>    - Heiner Kallweit <hkallweit1@...il.com>
>  
> -allOf:
> -  - $ref: pwm.yaml#
> -
>  properties:
>    compatible:
>      oneOf:
> @@ -43,12 +40,8 @@ properties:
>      maxItems: 2
>  
>    clock-names:
> -    oneOf:
> -      - items:
> -          - enum: [clkin0, clkin1]
> -      - items:
> -          - const: clkin0
> -          - const: clkin1
> +    minItems: 1
> +    maxItems: 2
>  
>    "#pwm-cells":
>      const: 3
> @@ -57,6 +50,56 @@ required:
>    - compatible
>    - reg
>  
> +allOf:
> +  - $ref: pwm.yaml#
> +
> +  - if:
> +      properties:
> +        compatible:
> +          contains:
> +            enum:
> +              - amlogic,meson8-pwm
> +              - amlogic,meson8b-pwm
> +              - amlogic,meson-gxbb-pwm
> +              - amlogic,meson-gxbb-ao-pwm
> +              - amlogic,meson-axg-ee-pwm
> +              - amlogic,meson-axg-ao-pwm
> +              - amlogic,meson-g12a-ee-pwm
> +              - amlogic,meson-g12a-ao-pwm-ab
> +              - amlogic,meson-g12a-ao-pwm-cd
> +              - amlogic,meson-gx-pwm
> +              - amlogic,meson-gx-ao-pwm
> +    then:
> +      # Historic bindings tied to the driver implementation
> +      # The clocks provided here are meant to be matched with the input
> +      # known (hard-coded) in the driver and used to select pwm clock
> +      # source. Currently, the linux driver ignores this.
> +      properties:
> +        clock-names:
> +          oneOf:
> +            - items:
> +                - enum: [clkin0, clkin1]
> +            - items:
> +                - const: clkin0
> +                - const: clkin1
> +
> +  # Newer IP block take a single input per channel, instead of 4 inputs
> +  # for both channels
> +  - if:
> +      properties:
> +        compatible:
> +          contains:
> +            enum:
> +              - amlogic,meson-s4-pwm
> +    then:
> +      properties:
> +        clocks:
> +          items:
> +            - description: input clock of PWM channel A
> +            - description: input clock of PWM channel B
> +      required:
> +        - clocks

What are the 'clock-names' in this case? Because it's still allowed.

Rob