[PATCH 1/2] dt-bindings: mfd: mediatek: mt6397: describe the RTC's nvmem layout
From: Ryan Brue <hidden>
Date: 2026-09-18 04:58:09
Also in:
linux-devicetree, linux-mediatek, linux-pm, linux-rtc, lkml
Subsystem:
mediatek board level shutdown drivers, mediatek pmic led driver, multifunction devices (mfd), open firmware and flattened device tree bindings, the rest · Maintainers:
Sen Chu, Sean Wang, Macpaul Lin, Lee Jones, Rob Herring, Krzysztof Kozlowski, Conor Dooley, Linus Torvalds
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 <redacted> --- 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
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2.55.0