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[212.71.14.70]) by smtp.gmail.com with ESMTPSA id ffacd0b85a97d-48dfd503a0dsm17743957f8f.47.2026.10.18.08.10.59 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Sun, 18 Oct 2026 08:10:59 -0700 (PDT) From: Sander Speetjens To: Alexandre Belloni Cc: Rob Herring , Krzysztof Kozlowski , Conor Dooley , Florian Fainelli , Jonathan Bell , Stefan Wahren , linux-rtc@vger.kernel.org, devicetree@vger.kernel.org, linux-rpi-kernel@lists.infradead.org, linux-arm-kernel@lists.infradead.org, sander.speetjens@gmail.com, pbrobinson@gmail.com, Conor Dooley , Krzysztof Kozlowski Subject: [PATCH v14 2/3] dt-bindings: rtc: Add property for Raspberry Pi 5 RTC Date: Sun, 18 Oct 2026 17:10:55 +0200 Message-ID: <20261018151056.1051330-3-sander.speetjens@gmail.com> X-Mailer: git-send-email 2.56.0 In-Reply-To: <20261018151056.1051330-1-sander.speetjens@gmail.com> References: <20261018151056.1051330-1-sander.speetjens@gmail.com> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.9.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20261018_081101_989308_6DA47386 X-CRM114-Status: GOOD ( 11.78 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org 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 --- V13 -> V14: No changes V13: https://lore.kernel.org/linux-rtc/20261018150028.1047172-1-sander.speetjens@gmail.com .../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"; -- 2.56.0