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

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Message-ID: <1jbkc4cgrp.fsf@starbuckisacylon.baylibre.com>
Date:   Wed, 08 Nov 2023 18:08:55 +0100
From:   Jerome Brunet <jbrunet@...libre.com>
To:     Rob Herring <robh@...nel.org>
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 Wed 08 Nov 2023 at 11:04, Rob Herring <robh@...nel.org> wrote:

> 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.
>

Indeed, it should not be.
I should add 'clock-names: false' , right ?

> Rob