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

[Valentin CARON]

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@xxxxxxxxxxx>
> > ---
> >   .../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