[PATCH v4 01/11] dt-bindings: rtc: Add Apple SMC RTC

[James Calligeros]

From: Sven Peter <sven at 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 at openbsd.org>
Reviewed-by: Neal Gompa <neal at gompa.dev>
Reviewed-by: Rob Herring (Arm) <robh at kernel.org>
Signed-off-by: Sven Peter <sven at kernel.org>
Signed-off-by: James Calligeros <jcalligeros99 at 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 5429538f7e2e..0410e712c900 100644
--- a/Documentation/devicetree/bindings/mfd/apple,smc.yaml
+++ b/Documentation/devicetree/bindings/mfd/apple,smc.yaml
@@ -46,6 +46,9 @@ properties:
   reboot:
     $ref: /schemas/power/reset/apple,smc-reboot.yaml
 
+  rtc:
+    $ref: /schemas/rtc/apple,smc-rtc.yaml
+
 additionalProperties: false
 
 required:
@@ -80,5 +83,11 @@ 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 000000000000..607b610665a2
--- /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 at 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 b45db73e55df..745d85b66365 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -2435,6 +2435,7 @@ 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