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SubjectRe: [PATCH 2/6] dt-bindings: rtc: stm32: add alarm A out property to select output
On 23/05/2022 14:34:22+0200, 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@foss.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 ?
>


I still think that the pin has to be the property and the function the value.

Or we could find a generic name and provide an array of pin, function
pair

Or, go for pinmuxing

My point here is that this is a common feature an RTCs and I don't want
every vendor to come up with their own properties.

Regards,

--
Alexandre Belloni, co-owner and COO, Bootlin
Embedded Linux and Kernel engineering
https://bootlin.com

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