linux-kernel - Re: [PATCH v3 2/3] dt-bindings: pwm: Document clk based PWM controller

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Date:   Sat, 22 Jan 2022 11:13:46 +0100
From:   Krzysztof Kozlowski <krzk@...nel.org>
To:     Sean Anderson <sean.anderson@...o.com>,
        Nikita Travkin <nikita@...n.ru>
Cc:     thierry.reding@...il.com, lee.jones@...aro.org,
        u.kleine-koenig@...gutronix.de, robh+dt@...nel.org,
        sboyd@...nel.org, linus.walleij@...aro.org, masneyb@...tation.org,
        linux-pwm@...r.kernel.org, devicetree@...r.kernel.org,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        ~postmarketos/upstreaming@...ts.sr.ht
Subject: Re: [PATCH v3 2/3] dt-bindings: pwm: Document clk based PWM
 controller

On 21/01/2022 22:34, Sean Anderson wrote:
> 
> 
> On 1/21/22 2:34 AM, Krzysztof Kozlowski wrote:
>> On Thu, 20 Jan 2022 at 17:15, Nikita Travkin <nikita@...n.ru> wrote:
>>>
>>> Add YAML devicetree binding for clk based PWM controller
>>>
>>> Signed-off-by: Nikita Travkin <nikita@...n.ru>
>>> --
>>> Changes in v2:
>>>  - fix the file name.
>>> ---
>>>  .../devicetree/bindings/pwm/clk-pwm.yaml      | 45 +++++++++++++++++++
>>>  1 file changed, 45 insertions(+)
>>>  create mode 100644 Documentation/devicetree/bindings/pwm/clk-pwm.yaml
>>>
>>> diff --git a/Documentation/devicetree/bindings/pwm/clk-pwm.yaml b/Documentation/devicetree/bindings/pwm/clk-pwm.yaml
>>> new file mode 100644
>>> index 000000000000..4fb2c1baaad4
>>> --- /dev/null
>>> +++ b/Documentation/devicetree/bindings/pwm/clk-pwm.yaml
>>> @@ -0,0 +1,45 @@
>>> +# SPDX-License-Identifier: GPL-2.0-only OR BSD-2-Clause
>>> +%YAML 1.2
>>> +---
>>> +$id: http://devicetree.org/schemas/pwm/clk-pwm.yaml#
>>> +$schema: http://devicetree.org/meta-schemas/core.yaml#
>>> +
>>> +title: Clock based PWM controller
>>> +
>>> +maintainers:
>>> +  - Nikita Travkin <nikita@...n.ru>
>>> +
>>> +description: |
>>> +  Some systems have clocks that can be exposed to external devices.
>>> +  (e.g. by muxing them to GPIO pins)
>>> +  It's often possible to control duty-cycle of such clocks which makes them
>>> +  suitable for generating PWM signal.
>>> +
>>> +allOf:
>>> +  - $ref: pwm.yaml#
>>> +
>>> +properties:
>>> +  compatible:
>>> +    const: clk-pwm
>>> +
>>> +  clocks:
>>> +    description: Clock used to generate the signal.
>>> +    maxItems: 1
>>> +
>>> +  "#pwm-cells":
>>> +    const: 2
>>> +
>>> +unevaluatedProperties: false
>>> +
>>> +required:
>>> +  - clocks
>>> +
>>> +examples:
>>> +  - |
>>> +    pwm-flash {
>>
>> Node names should be generic (see devicetree specification), so just "pwm".
> 
> And then what will you do if you have two clock-based pwms?

The same as we do with fixed clocks, keys and so on:
pwm-0
pwm-1
pwm-2

A descriptive suffix also appears, but there is no justification to use
it here. There is only one node in the example.


Best regards,
Krzysztof