[PATCH v2 01/11] dt-bindings: rtc: Add Apple SMC RTC

James Calligeros
2025-08-27T11:22:59Z

From: Sven Peter <sven@kernel.org>

Apple Silicon Macs (M1, etc.) have an RTC that is part of the PMU IC,
but most of the PMU functionality is abstracted out by the SMC.
An additional RTC offset stored inside NVMEM is required to compute
the current date/time.

Reviewed-by: Mark Kettenis <kettenis@openbsd.org>
Reviewed-by: Neal Gompa <neal@gompa.dev>
Reviewed-by: Rob Herring (Arm) <robh@kernel.org>
Signed-off-by: Sven Peter <sven@kernel.org>
Signed-off-by: James Calligeros <jcalligeros99@gmail.com>
---
.../bindings/mfd/apple,smc.yaml | 9 +++++++
.../bindings/rtc/apple,smc-rtc.yaml | 35 +++++++++++++++++++++++++
MAINTAINERS | 1 +
3 files changed, 45 insertions(+)

diff --git a/Documentation/devicetree/bindings/mfd/apple,smc.yaml b/Documentation/devicetree/bindings/mfd/apple,smc.yaml
index 8a10e270d421ecd703848f64af597de351fcfd74..38f077867bdeedba8a486a63e366e9c943a75681 100644
--- a/Documentation/devicetree/bindings/mfd/apple,smc.yaml
+++ b/Documentation/devicetree/bindings/mfd/apple,smc.yaml
@@ -41,6 +41,9 @@ properties:
reboot:
$ref: /schemas/power/reset/apple,smc-reboot.yaml

+ rtc:
+ $ref: /schemas/rtc/apple,smc-rtc.yaml
+
additionalProperties: false

required:
@@ -75,5 +78,11 @@ examples:
nvmem-cell-names = "shutdown_flag", "boot_stage",
"boot_error_count", "panic_count";
};
+
+ rtc {
+ compatible = "apple,smc-rtc";
+ nvmem-cells = <&rtc_offset>;
+ nvmem-cell-names = "rtc_offset";
+ };
};
};
diff --git a/Documentation/devicetree/bindings/rtc/apple,smc-rtc.yaml b/Documentation/devicetree/bindings/rtc/apple,smc-rtc.yaml
new file mode 100644
index 0000000000000000000000000000000000000000..607b610665a28b3ea2e86bd90cb5f3f28ebac726
--- /dev/null
+++ b/Documentation/devicetree/bindings/rtc/apple,smc-rtc.yaml
@@ -0,0 +1,35 @@
+# SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause)
+%YAML 1.2
+---
+$id: http://devicetree.org/schemas/rtc/apple,smc-rtc.yaml#
+$schema: http://devicetree.org/meta-schemas/core.yaml#
+
+title: Apple SMC RTC
+
+description:
+ Apple Silicon Macs (M1, etc.) have an RTC that is part of the PMU IC,
+ but most of the PMU functionality is abstracted out by the SMC.
+ An additional RTC offset stored inside NVMEM is required to compute
+ the current date/time.
+
+maintainers:
+ - Sven Peter <sven@kernel.org>
+
+properties:
+ compatible:
+ const: apple,smc-rtc
+
+ nvmem-cells:
+ items:
+ - description: 48bit RTC offset, specified in 32768 (2^15) Hz clock ticks
+
+ nvmem-cell-names:
+ items:
+ - const: rtc_offset
+
+required:
+ - compatible
+ - nvmem-cells
+ - nvmem-cell-names
+
+additionalProperties: false
diff --git a/MAINTAINERS b/MAINTAINERS
index fe168477caa45799dfe07de2f54de6d6a1ce0615..aaef8634985b35f54de1123ebb4176602066d177 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -2397,6 +2397,7 @@ F: Documentation/devicetree/bindings/pinctrl/apple,pinctrl.yaml
F: Documentation/devicetree/bindings/power/apple*
F: Documentation/devicetree/bindings/power/reset/apple,smc-reboot.yaml
F: Documentation/devicetree/bindings/pwm/apple,s5l-fpwm.yaml
+F: Documentation/devicetree/bindings/rtc/apple,smc-rtc.yaml
F: Documentation/devicetree/bindings/spi/apple,spi.yaml
F: Documentation/devicetree/bindings/spmi/apple,spmi.yaml
F: Documentation/devicetree/bindings/watchdog/apple,wdt.yaml

--
2.51.0