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Message-ID: <11f8d986-3e97-4191-b46c-ad3166ee6dc7@linaro.org>
Date:   Wed, 29 Nov 2023 17:41:07 +0100
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From:   neil.armstrong@linaro.org
Reply-To: neil.armstrong@linaro.org
Subject: Re: [PATCH v3 2/4] dt-bindings: pwm: amlogic: add new compatible for
 meson8 pwm type
Content-Language: en-US, fr
To:     Jerome Brunet <jbrunet@baylibre.com>
Cc:     Thierry Reding <thierry.reding@gmail.com>,
        Rob Herring <robh+dt@kernel.org>,
        Krzysztof Kozlowski <krzysztof.kozlowski+dt@linaro.org>,
        Conor Dooley <conor+dt@kernel.org>,
        Kevin Hilman <khilman@baylibre.com>,
        devicetree@vger.kernel.org, linux-kernel@vger.kernel.org,
        linux-amlogic@lists.infradead.org, linux-pwm@vger.kernel.org,
        JunYi Zhao <junyi.zhao@amlogic.com>,
        =?UTF-8?Q?Uwe_Kleine-K=C3=B6nig?= <u.kleine-koenig@pengutronix.de>
References: <20231129134004.3642121-1-jbrunet@baylibre.com>
 <20231129134004.3642121-3-jbrunet@baylibre.com>
 <8e78be99-3d4d-4f79-9791-404e60bcb67c@linaro.org>
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Hi,

On 29/11/2023 17:26, Jerome Brunet wrote:
> 
> On Wed 29 Nov 2023 at 17:20, Neil Armstrong <neil.armstrong@linaro.org> wrote:
> 
>> Hi,
>>
>> On 29/11/2023 14:39, Jerome Brunet wrote:
>>> Add a new compatible for the pwm found in the meson8 to sm1 Amlogic SoCs,
>>> dealing with clocks differently. This does not enable new HW. It is meant
>>> to fix a bad DT ABI for the currently supported HW.
>>> The original clock bindings describe which input the PWM channel
>>> multiplexer should pick among its possible parents, which are
>>> hard-coded in the driver. As such, it is a setting tied to the driver
>>> implementation and does not describe the HW.
>>> The new bindings introduce here describe the clocks input of the PWM
>>> block
>>> as they exist.
>>> The old compatible is deprecated but kept to maintain ABI compatibility.
>>> The SoC specific compatibles introduced match the SoC families supported
>>> by the original bindings.
>>> Signed-off-by: Jerome Brunet <jbrunet@baylibre.com>
>>> ---
>>>    .../devicetree/bindings/pwm/pwm-amlogic.yaml  | 52 ++++++++++++++++---
>>>    1 file changed, 46 insertions(+), 6 deletions(-)
>>> diff --git a/Documentation/devicetree/bindings/pwm/pwm-amlogic.yaml
>>> b/Documentation/devicetree/bindings/pwm/pwm-amlogic.yaml
>>> index 387976ed36d5..eece390114a3 100644
>>> --- a/Documentation/devicetree/bindings/pwm/pwm-amlogic.yaml
>>> +++ b/Documentation/devicetree/bindings/pwm/pwm-amlogic.yaml
>>> @@ -21,23 +21,35 @@ properties:
>>>              - amlogic,meson-g12a-ee-pwm
>>>              - amlogic,meson-g12a-ao-pwm-ab
>>>              - amlogic,meson-g12a-ao-pwm-cd
>>> -          - amlogic,meson-s4-pwm
>>> +        deprecated: true
>>>          - items:
>>>              - const: amlogic,meson-gx-pwm
>>>              - const: amlogic,meson-gxbb-pwm
>>> +        deprecated: true
>>>          - items:
>>>              - const: amlogic,meson-gx-ao-pwm
>>>              - const: amlogic,meson-gxbb-ao-pwm
>>> +        deprecated: true
>>>          - items:
>>>              - const: amlogic,meson8-pwm
>>>              - const: amlogic,meson8b-pwm
>>> +        deprecated: true
>>
>> I think deprecated should be moved in a third patch
> 
> The complain on v2 was that it was not clear the new binding was making
> the old one obsolete. It looked to me that the deprecation old bindings
> needed to go together with the introduction of the new.
> 
> I don't mind one way or the other
> 
> Is there a rule somewhere about this ?

Not sure about that, I don't think it's a problem to have both valid
at the same time, setting them deprecated afterwards looks cleaner
to avoid mixing too much changes at the same time.

Neil

> 
>>
>>> +      - const: amlogic,meson8-pwm-v2
>>> +      - items:
>>> +          - enum:
>>> +              - amlogic,meson8b-pwm-v2
>>> +              - amlogic,meson-gxbb-pwm-v2
>>> +              - amlogic,meson-axg-pwm-v2
>>> +              - amlogic,meson-g12-pwm-v2
>>> +          - const: amlogic,meson8-pwm-v2
>>> +      - const: amlogic,meson-s4-pwm
>>>        reg:
>>>        maxItems: 1
>>>        clocks:
>>>        minItems: 1
>>> -    maxItems: 2
>>> +    maxItems: 4
>>>        clock-names:
>>>        minItems: 1
>>> @@ -58,7 +70,6 @@ allOf:
>>>            compatible:
>>>              contains:
>>>                enum:
>>> -              - amlogic,meson8-pwm
>>>                  - amlogic,meson8b-pwm
>>>                  - amlogic,meson-gxbb-pwm
>>>                  - amlogic,meson-gxbb-ao-pwm
>>> @@ -67,14 +78,15 @@ allOf:
>>>                  - 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
>>
>> I don't understand why those entries are removed
> 
> It's a mistake. It should not have been added to begin with in
> the first patch. "amlogic,meson-gx-*" must go along with
> "amlogic,meson-gxbb-*" so it matches correctly without it.
> 
> I'll fix it
> 
>>
>>>        then:
>>> -      # Historic bindings tied to the driver implementation
>>> +      # Obsolete 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.
>>> +      # This is kept to maintain ABI backward compatibility.
>>
>> Same here, this should go in a third patch
>>
>>>          properties:
>>> +        clocks:
>>> +          maxItems: 2
>>>            clock-names:
>>>              oneOf:
>>>                - items:
>>> @@ -83,6 +95,27 @@ allOf:
>>>                    - const: clkin0
>>>                    - const: clkin1
>>>    +  # Newer binding where clock describe the actual clock inputs of the
>>> pwm
>>> +  # block. These are necessary but some inputs may be grounded.
>>> +  - if:
>>> +      properties:
>>> +        compatible:
>>> +          contains:
>>> +            enum:
>>> +              - amlogic,meson8-pwm-v2
>>> +    then:
>>> +      properties:
>>> +        clocks:
>>> +          minItems: 1
>>> +          items:
>>> +            - description: input clock 0 of the pwm block
>>> +            - description: input clock 1 of the pwm block
>>> +            - description: input clock 2 of the pwm block
>>> +            - description: input clock 3 of the pwm block
>>> +        clock-names: false
>>> +      required:
>>> +        - clocks
>>> +
>>>      # Newer IP block take a single input per channel, instead of 4 inputs
>>>      # for both channels
>>>      - if:
>>> @@ -112,6 +145,13 @@ examples:
>>>          clock-names = "clkin0", "clkin1";
>>>          #pwm-cells = <3>;
>>>        };
>>> +  - |
>>> +    pwm@2000 {
>>> +      compatible = "amlogic,meson8-pwm-v2";
>>> +      reg = <0x1000 0x10>;
>>> +      clocks = <&xtal>, <0>, <&fdiv4>, <&fdiv5>;
>>> +      #pwm-cells = <3>;
>>> +    };
>>>      - |
>>>        pwm@1000 {
>>>          compatible = "amlogic,meson-s4-pwm";
>>
>> Neil
> 
>