Re: [PATCH v2 1/4] dt-bindings: rtc: add schema for NXP S32G2/S32G3 SoCs

[Rob Herring]

On Tue, Oct 15, 2024 at 01:51:30PM +0300, Ciprian Costea wrote:
> From: Ciprian Marian Costea <ciprianmarian.costea@xxxxxxxxxxx>
> 
> This patch adds the dt-bindings for NXP S32G2/S32G3 SoCs RTC driver.
> 
> Co-developed-by: Bogdan-Gabriel Roman <bogdan-gabriel.roman@xxxxxxx>
> Signed-off-by: Bogdan-Gabriel Roman <bogdan-gabriel.roman@xxxxxxx>
> Co-developed-by: Ghennadi Procopciuc <ghennadi.procopciuc@xxxxxxx>
> Signed-off-by: Ghennadi Procopciuc <ghennadi.procopciuc@xxxxxxx>
> Signed-off-by: Ciprian Marian Costea <ciprianmarian.costea@xxxxxxxxxxx>
> ---
>  .../devicetree/bindings/rtc/nxp,s32g-rtc.yaml | 102 ++++++++++++++++++
>  1 file changed, 102 insertions(+)
>  create mode 100644 Documentation/devicetree/bindings/rtc/nxp,s32g-rtc.yaml
> 
> diff --git a/Documentation/devicetree/bindings/rtc/nxp,s32g-rtc.yaml b/Documentation/devicetree/bindings/rtc/nxp,s32g-rtc.yaml
> new file mode 100644
> index 000000000000..3a77d4dd8f3d
> --- /dev/null
> +++ b/Documentation/devicetree/bindings/rtc/nxp,s32g-rtc.yaml
> @@ -0,0 +1,102 @@
> +# SPDX-License-Identifier: (GPL-2.0 OR BSD-2-Clause)
> +%YAML 1.2
> +---
> +$id: http://devicetree.org/schemas/rtc/nxp,s32g-rtc.yaml#
> +$schema: http://devicetree.org/meta-schemas/core.yaml#
> +
> +title: NXP S32G2/S32G3 Real Time Clock (RTC)
> +
> +maintainers:
> +  - Bogdan Hamciuc <bogdan.hamciuc@xxxxxxx>
> +  - Ciprian Marian Costea <ciprianmarian.costea@xxxxxxx>
> +
> +properties:
> +  compatible:
> +    oneOf:
> +      - enum:
> +          - nxp,s32g2-rtc
> +      - items:
> +          - const: nxp,s32g3-rtc
> +          - const: nxp,s32g2-rtc
> +
> +  reg:
> +    maxItems: 1
> +
> +  interrupts:
> +    maxItems: 1
> +
> +  "#clock-cells":
> +    const: 1
> +
> +  clocks:
> +    items:
> +      - description: ipg clock drives the access to the
> +          RTC iomapped registers
> +
> +  clock-names:
> +    items:
> +      - const: ipg
> +
> +  assigned-clocks:
> +    minItems: 1
> +    items:
> +      - description: Runtime clock source. It must be a clock
> +            source for the RTC module. It will be disabled by hardware
> +            during Standby/Suspend.
> +      - description: Standby/Suspend clock source. It is optional
> +            and can be used in case the RTC will continue ticking during
> +            platform/system suspend. RTC hardware module contains a
> +            hardware mux for clock source selection.

If the RTC h/w contains a mux, then your mux inputs should be listed in 
'clocks', not here.

> +
> +  assigned-clock-parents:
> +    description: List of phandles to each parent clock.
> +
> +  assigned-clock-rates:
> +    description: List of frequencies for RTC clock sources.
> +            RTC module contains 2 hardware divisors which can be
> +            enabled or not. Hence, available frequencies are the following
> +            parent_freq, parent_freq / 512, parent_freq / 32 or
> +            parent_freq / (512 * 32)

In general, assigned-clocks* do not need to be documented and should 
never be required.

> +
> +required:
> +  - compatible
> +  - reg
> +  - interrupts
> +  - "#clock-cells"
> +  - clocks
> +  - clock-names
> +  - assigned-clocks
> +  - assigned-clock-parents
> +  - assigned-clock-rates
> +
> +additionalProperties: false
> +
> +examples:
> +  - |
> +    #include <dt-bindings/interrupt-controller/arm-gic.h>
> +    #include <dt-bindings/interrupt-controller/irq.h>
> +
> +    rtc0: rtc@40060000 {
> +        compatible = "nxp,s32g3-rtc",
> +                   "nxp,s32g2-rtc";
> +        reg = <0x40060000 0x1000>;
> +        interrupts = <GIC_SPI 121 IRQ_TYPE_LEVEL_HIGH>;
> +        #clock-cells = <1>;
> +        clocks = <&clks 54>;
> +        clock-names = "ipg";
> +        /*
> +         * Configuration of default parent clocks.
> +         * 'assigned-clocks' 0-3 IDs are Runtime clock sources
> +         * 4-7 IDs are Suspend/Standby clock sources.
> +         */
> +        assigned-clocks = <&rtc0 2>, <&rtc0 4>;

That's weird...

> +        assigned-clock-parents = <&clks 56>, <&clks 55>;

I'd expect these should be in 'clocks'. I don't think this node should 
be a clock provider unless it provides a clock to something outside the 
RTC.

Looks like you are just using assigned-clocks to configure the clock mux 
in the RTC. That's way over complicated. Just define a vendor specific 
property with the mux settings. 

> +        /*
> +         * Clock frequency can be divided by value
> +         * 512 or 32 (or both) via hardware divisors.
> +         * Below configuration:
> +         * Runtime clock source: FIRC (51 MHz) / 512 (DIV512)
> +         * Suspend/Standby clock source: SIRC (32 KHz)
> +         */
> +        assigned-clock-rates = <99609>, <32000>;
> +    };
> -- 
> 2.45.2
>