linux-kernel - Re: [PATCH 3/7] pwm: dwc: add of/platform support

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Message-ID: <83b53b26-6621-d580-c704-b7c82bd96a12@sifive.com>
Date:   Wed, 13 Jul 2022 17:20:05 +0100
From:   Ben Dooks <ben.dooks@...ive.com>
To:     Uwe Kleine-König <u.kleine-koenig@...gutronix.de>
Cc:     Rob Herring <robh@...nel.org>, linux-pwm@...r.kernel.org,
        devicetree@...r.kernel.org, linux-kernel@...r.kernel.org,
        Lee Jones <lee.jones@...aro.org>,
        Thierry Reding <thierry.reding@...il.com>,
        Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>,
        Greentime Hu <greentime.hu@...ive.com>,
        Jude Onyenegecha <jude.onyenegecha@...ive.com>,
        Sudip Mukherjee <sudip.mukherjee@...ive.com>,
        William Salmon <william.salmon@...ive.com>,
        Adnan Chowdhury <adnan.chowdhury@...ive.com>
Subject: Re: [PATCH 3/7] pwm: dwc: add of/platform support

On 13/07/2022 16:07, Uwe Kleine-König wrote:
> On Wed, Jul 13, 2022 at 03:30:07PM +0100, Ben Dooks wrote:
>> On 13/07/2022 14:52, Uwe Kleine-König wrote:
>>> On Wed, Jul 13, 2022 at 12:56:55PM +0100, Ben Dooks wrote:
>>>> On 12/07/2022 23:17, Rob Herring wrote:
>>>>> On Tue, Jul 12, 2022 at 11:01:09AM +0100, Ben Dooks wrote:
>>>>>> The dwc pwm controller can be used in non-PCI systems, so allow
>>>>>> either platform or OF based probing.
>>>>>>
>>>>>> Signed-off-by: Ben Dooks <ben.dooks@...ive.com>
>>
>> [snip]
>>
>>>>>> +properties:
>>>>>> +  "#pwm-cells":
>>>>>> +    description: |
>>>>>> +      See pwm.yaml in this directory for a description of the cells format.
>>>>>
>>>>> pwm.yaml doesn't define how many cells. You need to. And you don't need
>>>>> generic descriptions.
>>>>
>>>>    "#pwm-cells":
>>>>       const: 1
>>>>
>>>> should be sufficient then?
>>>
>>> I would expect a value of (at least) 2 or (better) 3.
>>
>> OOPS, forgot the phandle.
>>
>> I will have to check if we have any support yet for dealing
>> with any of the pwm flags yet.
> 
> I didn't double check, but given that the driver only supports inversed
> polarity it might not even work without passing the flag for inversed
> polarity. Having said that, I expect you have to only add "#pwm-cells =
> <3>;" to your dts and then everything should work just fine.

I hadn't noticed, but we've been testing with the sysfs interface
as we're using qemu.