linux-kernel - Re: [PATCH 2/6] dt-bindings: rtc: stm32: add alarm A out property to select output

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Message-ID: <952b1ffb-5589-60ac-6ea9-6076cb13d433@foss.st.com>
Date:   Fri, 24 Jun 2022 10:35:57 +0200
From:   Valentin CARON <valentin.caron@...s.st.com>
To:     Alexandre Belloni <alexandre.belloni@...tlin.com>
CC:     Alessandro Zummo <a.zummo@...ertech.it>,
        Rob Herring <robh+dt@...nel.org>,
        Krzysztof Kozlowski <krzk+dt@...nel.org>,
        Alexandre Torgue <alexandre.torgue@...s.st.com>,
        Gabriel Fernandez <gabriel.fernandez@...s.st.com>,
        Amelie Delaunay <amelie.delaunay@...s.st.com>,
        <linux-rtc@...r.kernel.org>, <devicetree@...r.kernel.org>,
        <linux-stm32@...md-mailman.stormreply.com>,
        <linux-arm-kernel@...ts.infradead.org>,
        <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 2/6] dt-bindings: rtc: stm32: add alarm A out property to
 select output

Hi Alexandre,

May I have your view regarding these new elements ?

Thank you,
Valentin

On 5/23/22 14:34, Valentin CARON wrote:
> Hi Alexandre,
>
> On 5/4/22 22:27, Alexandre Belloni wrote:
>> Hello,
>>
>> On 04/05/2022 15:06:13+0200, Valentin Caron wrote:
>>> STM32 RTC can pulse some SOC pins when an alarm of RTC expires.
>>>
>>> This patch adds property to activate alarm A output. The pulse can
>>> output on three pins RTC_OUT1, RTC_OUT2, RTC_OUT2_RMP
>>> (PC13, PB2, PI8 on stm32mp15) (PC13, PB2, PI1 on stm32mp13).
>>>
>>> Signed-off-by: Valentin Caron <valentin.caron@...s.st.com>
>>> ---
>>>   .../devicetree/bindings/rtc/st,stm32-rtc.yaml | 19 
>>> ++++++++++++++++++-
>>>   1 file changed, 18 insertions(+), 1 deletion(-)
>>>
>>> diff --git a/Documentation/devicetree/bindings/rtc/st,stm32-rtc.yaml 
>>> b/Documentation/devicetree/bindings/rtc/st,stm32-rtc.yaml
>>> index 56d46ea35c5d..71e02604e8de 100644
>>> --- a/Documentation/devicetree/bindings/rtc/st,stm32-rtc.yaml
>>> +++ b/Documentation/devicetree/bindings/rtc/st,stm32-rtc.yaml
>>> @@ -59,6 +59,13 @@ properties:
>>>         Refer to <include/dt-bindings/rtc/rtc-stm32.h> for the 
>>> supported values.
>>>         Pinctrl state named "default" may be defined to reserve pin 
>>> for RTC output.
>>>   +  st,alarm:
>>> +    $ref: "/schemas/types.yaml#/definitions/uint32"
>>> +    description: |
>>> +      To select and enable RTC Alarm A output.
>>> +      Refer to <include/dt-bindings/rtc/rtc-stm32.h> for the 
>>> supported values.
>>> +      Pinctrl state named "default" may be defined to reserve pin 
>>> for RTC output.
>>> +
>>>   allOf:
>>>     - if:
>>>         properties:
>>> @@ -75,6 +82,9 @@ allOf:
>>>           st,lsco:
>>>             maxItems: 0
>>>   +        st,alarm:
>>> +          maxItems: 0
>>> +
>>>           clock-names: false
>>>           required:
>>> @@ -95,6 +105,9 @@ allOf:
>>>           st,lsco:
>>>             maxItems: 0
>>>   +        st,alarm:
>>> +          maxItems: 0
>>> +
>>>         required:
>>>           - clock-names
>>>           - st,syscfg
>>> @@ -117,6 +130,9 @@ allOf:
>>>           st,lsco:
>>>             maxItems: 1
>>>   +        st,alarm:
>>> +          maxItems: 1
>>> +
>>>         required:
>>>           - clock-names
>>>   @@ -153,8 +169,9 @@ examples:
>>>         clocks = <&rcc RTCAPB>, <&rcc RTC>;
>>>         clock-names = "pclk", "rtc_ck";
>>>         interrupts = <GIC_SPI 3 IRQ_TYPE_LEVEL_HIGH>;
>>> +      st,alarm = <RTC_OUT1>;
>>>         st,lsco = <RTC_OUT2_RMP>;
>> Shouldn't that be exactly the opposite? You have two pins that can
>> output different functions. The property should be the pin and the value
>> the function. I'd go even further and I would say this is actually
>> pinmuxing.
>>
> You're right, if the property is the pin and the value the function, 
> this looks like a pinctrl node.
> We choose to develop theses functionalities in the reverse order, to 
> avoid the complexity of adding
> the pinctrl framework to our driver. Moreover, LSCO and AlarmA may 
> haven't a peripheral client and
> this would probably require to also implement pinctrl hogging.
>
> Is the implementation that we have proposed is acceptable regarding 
> theses elements ?
>
> Thank you,
> Valentin
>