From 58db0fbeef2a2cceef452a874e9983ccd66f3e78 Mon Sep 17 00:00:00 2001 From: Sander Speetjens Date: Sun, 18 Oct 2026 17:10:55 +0200 Subject: [PATCH] dt-bindings: rtc: Add property for Raspberry Pi 5 RTC The Raspberry Pi 5 has a built-in RTC that can be battery-backed via the VBAT pin. When a rechargeable coin cell is used, the hardware requires a trickle-charge voltage to keep the battery topped up. Expose the trickle-voltage-millivolt DT property so the driver can program the correct charge voltage for board specific configurations with the attached battery. The property is added to the existing raspberrypi,bcm2835-firmware binding (rather than creating a new RTC node) because the RTC is accessed exclusively through the firmware mailbox interface. We only $ref the individual property from rtc.yaml and do not reference the full schema, because the firmware node name does not match the $nodename pattern required by rtc.yaml. Acked-by: Conor Dooley Acked-by: Krzysztof Kozlowski Signed-off-by: Sander Speetjens Link: https://patch.msgid.link/20261018151056.1051330-3-sander.speetjens@gmail.com Signed-off-by: Alexandre Belloni --- .../bindings/arm/bcm/raspberrypi,bcm2835-firmware.yaml | 6 ++++++ 1 file changed, 6 insertions(+) diff --git a/Documentation/devicetree/bindings/arm/bcm/raspberrypi,bcm2835-firmware.yaml b/Documentation/devicetree/bindings/arm/bcm/raspberrypi,bcm2835-firmware.yaml index 983ea80eaec9..dc71fd57834e 100644 --- a/Documentation/devicetree/bindings/arm/bcm/raspberrypi,bcm2835-firmware.yaml +++ b/Documentation/devicetree/bindings/arm/bcm/raspberrypi,bcm2835-firmware.yaml @@ -133,6 +133,11 @@ properties: required: - compatible + trickle-voltage-millivolt: + $ref: /schemas/rtc/rtc.yaml#/properties/trickle-voltage-millivolt + minimum: 1300 + maximum: 5000 + required: - compatible - mboxes @@ -144,6 +149,7 @@ examples: firmware { compatible = "raspberrypi,bcm2835-firmware", "simple-mfd"; mboxes = <&mailbox>; + trickle-voltage-millivolt = <3300>; firmware_clocks: clocks { compatible = "raspberrypi,firmware-clocks";