From 3606288af5e8c09a14ab5b19e121feec75296354 Mon Sep 17 00:00:00 2001 From: Ryan Brue Date: Thu, 17 Sep 2026 23:57:46 -0500 Subject: [PATCH] dt-bindings: mfd: mediatek: mt6397: describe the RTC's nvmem layout 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 Reviewed-by: Rob Herring (Arm) Reviewed-by: AngeloGioacchino Del Regno Link: https://patch.msgid.link/20260917-rbrue-suez-upstreaming-mt6397-rtc-nvmem-v1-1-558b8f95cfbc@gmail.com Signed-off-by: Lee Jones --- .../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 bbd56e522a75..055625362951 100644 --- a/Documentation/devicetree/bindings/mfd/mediatek,mt6397.yaml +++ b/Documentation/devicetree/bindings/mfd/mediatek,mt6397.yaml @@ -84,6 +84,15 @@ 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