Re: [PATCH v2 1/2] dt-bindings: pwm: Add Loongson PWM controller

[Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>]

On 11/04/2024 13:01, Binbin Zhou wrote:
> On Thu, Apr 11, 2024 at 4:26 PM Krzysztof Kozlowski
> <krzysztof.kozlowski@linaro.org> wrote:
>>
>> On 11/04/2024 11:16, Binbin Zhou wrote:
>>> Add Loongson PWM controller binding with DT schema format using
>>> json-schema.
>>>
>>> Signed-off-by: Binbin Zhou <zhoubinbin@loongson.cn>
>>
>>
>>> +properties:
>>> +  compatible:
>>> +    oneOf:
>>> +      - const: loongson,ls7a-pwm
>>> +      - items:
>>> +          - enum:
>>> +              - loongson,ls2k0500-pwm
>>> +              - loongson,ls2k1000-pwm
>>> +              - loongson,ls2k2000-pwm
>>> +          - const: loongson,ls7a-pwm
>>> +
>>> +  reg:
>>> +    maxItems: 1
>>> +
>>> +  interrupts:
>>> +    maxItems: 1
>>> +
>>> +  clocks:
>>> +    maxItems: 1
>>> +
>>> +  '#pwm-cells':
>>> +    description:
>>> +      The first cell must have a value of 0, which specifies the PWM output signal;
>>
>> If you have always the same value in PWM phandle, why encoding it in the
>> phandle in the first place? What's the benefit of passing 0?
> 
> Hi Krzysztof:
> 
> My thoughts are:
> First of all, our pwm has only one output signal, so it can only be 0.
> Also, as you know from the pwm xlate function, the first cell is the
> pwm index, so I fixed it to be 0 here.
> 
> The xlate function:
> https://elixir.bootlin.com/linux/v6.8/source/drivers/pwm/core.c#L106

You refer for xlate for PWM with three cells. You do not have three
cells, as you have only on signal, so why insisting on using other
xlate? Do you do the same for clocks? Or resets?

I don't think you use appropriate argument in this discussion. We talk
about hardware and your argument "I don't want to use my own xlate in
the driver" is about driver.


Best regards,
Krzysztof