Re: [PATCH 1/2] dt-bindings: mfd: mediatek: mt6397: describe the RTC's nvmem layout

[AngeloGioacchino Del Regno]

On 9/18/26 06:57, Ryan Brue wrote:
> Four of the MT6397 RTC's alarm registers use only their low bits; the
> high byte of each is storage the clock and the alarm don't touch.
> MediaTek's documentation names them RTC_NEW_SPARE0 to RTC_NEW_SPARE3 and
> assigns the first to a fuel gauge, which is what a battery driver reads
> at boot so that the reported capacity does not jump across a reboot.
>
> They sit in the RTC's always-on domain, so the driver can offer them as
> a battery-backed nvmem provider. Allow a board to lay cells out over
> them.
>
> Assisted-by: LLM
> Signed-off-by: Ryan Brue <ryanbrue.dev@xxxxxxxxx>

Makes a lot of sense to me.

Reviewed-by: AngeloGioacchino Del Regno <angelogioacchino.delregno@xxxxxxxxxxxxx>

> ---
>   Documentation/devicetree/bindings/mfd/mediatek,mt6397.yaml | 9 +++++++++
>   1 file changed, 9 insertions(+)
>
> diff --git a/Documentation/devicetree/bindings/mfd/mediatek,mt6397.yaml b/Documentation/devicetree/bindings/mfd/mediatek,mt6397.yaml
> index 3cbc0dc12c31..5c89c589b53c 100644
> --- a/Documentation/devicetree/bindings/mfd/mediatek,mt6397.yaml
> +++ b/Documentation/devicetree/bindings/mfd/mediatek,mt6397.yaml
> @@ -81,6 +81,15 @@ properties:
>   
>         start-year: true
>   
> +      nvmem-layout:
> +        $ref: /schemas/nvmem/layouts/nvmem-layout.yaml
> +        description:
> +          The RTC carries four bytes of storage that neither the clock nor the
> +          alarm uses, in the high half of four of the alarm registers, and
> +          offers them as a battery-backed nvmem provider. MediaTek's
> +          documentation names them RTC_NEW_SPARE0 to RTC_NEW_SPARE3 and gives
> +          the first to a fuel gauge.
> +
>       required:
>         - compatible
>