Re: [PATCH v8 1/6] dt-bindings: rtc: Add pinctrl for S35390A

[Markus Probst <markus.probst@posteo.de>]

[-- Attachment #1: Type: text/plain, Size: 4763 bytes --]

On Tue, 2026-09-01 at 12:05 +0200, Krzysztof Kozlowski wrote:
> On Mon, Aug 31, 2026 at 05:42:22PM +0000, Markus Probst wrote:
> > Synology NAS devices use the output pin for interrupt signal 1 to wake up
> > the system.
> > 
> > Move devicetree bindings for sii,s35390a into its own file.
> > Add necessary properties to configure the individual pins via pinctrl,
> > which allows the interrupt signal 1 to be used for wakeup alarm.
> > 
> > Signed-off-by: Markus Probst <markus.probst@posteo.de>
> > ---
> >  .../devicetree/bindings/rtc/sii,s35390a.yaml       | 117 +++++++++++++++++++++
> >  .../devicetree/bindings/rtc/trivial-rtc.yaml       |   3 -
> >  2 files changed, 117 insertions(+), 3 deletions(-)
> > 
> > diff --git a/Documentation/devicetree/bindings/rtc/sii,s35390a.yaml b/Documentation/devicetree/bindings/rtc/sii,s35390a.yaml
> > new file mode 100644
> > index 000000000000..dfe632c4b2c8
> > --- /dev/null
> > +++ b/Documentation/devicetree/bindings/rtc/sii,s35390a.yaml
> > @@ -0,0 +1,117 @@
> > +# SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause)
> > +%YAML 1.2
> > +---
> > +$id: http://devicetree.org/schemas/rtc/sii,s35390a.yaml#
> > +$schema: http://devicetree.org/meta-schemas/core.yaml#
> > +
> > +title: S-35390A 2-WIRE REAL-TIME CLOCK
> > +
> > +maintainers:
> > +  - Markus Probst <markus.probst@posteo.de>
> > +
> > +description:
> > +  The S-35390A is a CMOS 2-wire real-time clock IC which operates with the
> > +  very low current consumption in the wide range of operation voltage.
> > +
> > +allOf:
> > +  - $ref: rtc.yaml#
> > +
> > +properties:
> > +  compatible:
> > +    const: sii,s35390a
> > +
> > +  reg:
> > +    maxItems: 1
> > +
> > +  interrupts:
> > +    minItems: 1
> > +    maxItems: 2
> > +    description: Supports up to 2 interrupt lines via the INT1 and INT2 pins.
> > +
> > +  interrupt-names:
> > +    items:
> > +      - const: int1
> > +      - const: int2
> > +
> > +  wakeup-parent: true
> > +
> > +  wakeup-source: true
> > +
> > +  "#clock-cells":
> > +    const: 1
> > +
> > +patternProperties:
> > +  "^pins":
> > +    type: object
> > +    additionalProperties: false
> > +
> > +    patternProperties:
> > +      "-pins$":
> > +        type: object
> > +        additionalProperties: false
> > +
> > +        allOf:
> > +          - $ref: /schemas/pinctrl/pinmux-node.yaml#
> > +
> > +        properties:
> > +          pins:
> > +            minItems: 1
> > +            items:
> > +              enum:
> > +                - int1
> > +                - int2
> > +
> > +          function:
> > +            description: |
> > +              Pin function:
> > +              - ignore:  Preserve the previous state.
> > +              - disable: Disable pin output.
> > +              - wakeup:  Output wakes up the system.
> > +              - clock:   Output clock pulse.
> > +              - pmin1:   Minute periodical output with 50% duty.
> > +              - pmin2:   Minute periodical output L for 7.81 ms.
> > +                         Can only be used with pin int1.
> > +            enum:
> > +              - ignore
> > +              - disable
> > +              - wakeup
> > +              - clock
> > +              - pmin1
> > +              - pmin2
> > +
> > +        required:
> > +          - pins
> > +          - function
> > +
> > +required:
> > +  - compatible
> > +  - reg
> > +
> > +unevaluatedProperties: false
> > +
> > +examples:
> > +  - |
> > +    i2c {
> > +        #address-cells = <1>;
> > +        #size-cells = <0>;
> > +
> > +        rtc@30 {
> > +            compatible = "sii,s35390a";
> > +            reg = <0x30>;
> > +            pinctrl-0 = <&rtc_pins_default>;
> > +            pinctrl-names = "default";
> > +
> > +            wakeup-parent = <&int>;
> 
> I don't understand this need. Device does not generate interrupts - no
> interrupts property - thus how can it wakeup?
It is just an example.

> 
> As explained in commit msg, the signal at int1 goes to the SoC, right?
I assume.

> So where does it go? To which pin of which device? &int?
For my Synology DS923+ NAS, I do not have schematics. I only know for
sure from source code that INT1 is used for wakeup and I can confirm
that this does indeed wake the device up. 

> 
> Can you show complete upstream DTS using this?
There is arch/arm/boot/dts/ti/omap/am3517-som.dtsi, which has the pin
output of INT1 routed to a gpio pin. INT2 isn't connected at all.
According to the public schematic [1], this looks accurate.


Thanks
- Markus Probst

[1] https://www.scribd.com/doc/60133698/SOM-M2-Schematic

> 
> 
> Best regards,
> Krzysztof

[-- Attachment #2: This is a digitally signed message part --]
[-- Type: application/pgp-signature, Size: 870 bytes --]