From: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
To: Binbin Zhou <zhoubb.aaron@gmail.com>
Cc: "Binbin Zhou" <zhoubinbin@loongson.cn>,
"Huacai Chen" <chenhuacai@loongson.cn>,
"Uwe Kleine-König" <u.kleine-koenig@pengutronix.de>,
"Rob Herring" <robh+dt@kernel.org>,
"Krzysztof Kozlowski" <krzysztof.kozlowski+dt@linaro.org>,
"Conor Dooley" <conor+dt@kernel.org>,
"Juxin Gao" <gaojuxin@loongson.cn>,
"Huacai Chen" <chenhuacai@kernel.org>,
loongson-kernel@lists.loongnix.cn, linux-pwm@vger.kernel.org,
devicetree@vger.kernel.org, "Xuerui Wang" <kernel@xen0n.name>,
loongarch@lists.linux.dev
Subject: Re: [PATCH v2 1/2] dt-bindings: pwm: Add Loongson PWM controller
Date: Thu, 11 Apr 2024 16:44:37 +0200 [thread overview]
Message-ID: <b551f712-ed95-4d90-b0fd-7cf471bc9eee@linaro.org> (raw)
In-Reply-To: <CAMpQs4KgzOjJe52BAhTb5P4t5ZynkW9AUEzPBkX_1h5XHuk5Ew@mail.gmail.com>
On 11/04/2024 16:35, Binbin Zhou wrote:
> On Thu, Apr 11, 2024 at 5:07 PM Krzysztof Kozlowski
> <krzysztof.kozlowski@linaro.org> wrote:
>>
>> 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.
>>
> Hi Krzysztof:
>
> Thanks for your comments.
>
> Emm... Indeed, I used to think about it from the driver's perspective.
> From the binding perspective, two cells really should be more appropriate.
> I try to make the following changes in the next version patchset:
>
> '#pwm-cells':
> description:
> The first cell is the period in nanoseconds;
> The second cell flag supported by this binding is PWM_POLARITY_INVERTED.
> const: 2
>
> Accordingly, the custom xlate function will be used in the driver.
If your other, upcoming variants had more PWM outputs, then I would find
reasonable keeping cells=3 to have one approach for all of them. But I
guess that's not the case here.
Best regards,
Krzysztof
next prev parent reply other threads:[~2024-04-11 14:44 UTC|newest]
Thread overview: 13+ messages / expand[flat|nested] mbox.gz Atom feed top
2024-04-11 9:16 [PATCH v2 0/2] pwm: Introduce pwm driver for the Loongson family chips Binbin Zhou
2024-04-11 9:16 ` [PATCH v2 1/2] dt-bindings: pwm: Add Loongson PWM controller Binbin Zhou
2024-04-11 10:26 ` Krzysztof Kozlowski
2024-04-11 11:01 ` Binbin Zhou
2024-04-11 11:07 ` Krzysztof Kozlowski
2024-04-11 14:35 ` Binbin Zhou
2024-04-11 14:44 ` Krzysztof Kozlowski [this message]
2024-04-11 15:21 ` Uwe Kleine-König
2024-04-11 19:10 ` Krzysztof Kozlowski
2024-04-11 19:12 ` Krzysztof Kozlowski
2024-04-11 9:16 ` [PATCH v2 2/2] pwm: Add Loongson PWM controller support Binbin Zhou
2024-04-12 6:47 ` Huacai Chen
2024-04-12 7:30 ` Binbin Zhou
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