linux-kernel - [PATCH v4 2/9] dt-bindings: power: reboot: Add Apple Mac SMC Reboot Controller

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Message-Id: <20250503-smc-6-15-v4-2-500b9b6546fc@svenpeter.dev>
Date: Sat, 03 May 2025 10:06:49 +0000
From: Sven Peter via B4 Relay <devnull+sven.svenpeter.dev@...nel.org>
To: Sven Peter <sven@...npeter.dev>, Janne Grunau <j@...nau.net>, 
 Alyssa Rosenzweig <alyssa@...enzweig.io>, Neal Gompa <neal@...pa.dev>, 
 Hector Martin <marcan@...can.st>, Linus Walleij <linus.walleij@...aro.org>, 
 Bartosz Golaszewski <brgl@...ev.pl>, Rob Herring <robh@...nel.org>, 
 Krzysztof Kozlowski <krzk+dt@...nel.org>, 
 Conor Dooley <conor+dt@...nel.org>, Sebastian Reichel <sre@...nel.org>, 
 Lee Jones <lee@...nel.org>, Marc Zyngier <maz@...nel.org>, 
 "Russell King (Oracle)" <rmk+kernel@...linux.org.uk>
Cc: asahi@...ts.linux.dev, linux-arm-kernel@...ts.infradead.org, 
 linux-gpio@...r.kernel.org, devicetree@...r.kernel.org, 
 linux-kernel@...r.kernel.org, linux-pm@...r.kernel.org
Subject: [PATCH v4 2/9] dt-bindings: power: reboot: Add Apple Mac SMC
 Reboot Controller

From: Sven Peter <sven@...npeter.dev>

On Apple Silicon machines a clean shutdown or reboot requires
talking to SMC and writing to NVMEM cells. Add a binding for
this MFD sub-device.

Signed-off-by: Sven Peter <sven@...npeter.dev>
---
 .../bindings/power/reset/apple,smc-reboot.yaml     | 52 ++++++++++++++++++++++
 MAINTAINERS                                        |  1 +
 2 files changed, 53 insertions(+)

diff --git a/Documentation/devicetree/bindings/power/reset/apple,smc-reboot.yaml b/Documentation/devicetree/bindings/power/reset/apple,smc-reboot.yaml
new file mode 100644
index 0000000000000000000000000000000000000000..e55e524914c2f57f7acf239fdefcbdc7a993b69f
--- /dev/null
+++ b/Documentation/devicetree/bindings/power/reset/apple,smc-reboot.yaml
@@ -0,0 +1,52 @@
+# SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause)
+%YAML 1.2
+---
+$id: http://devicetree.org/schemas/power/reset/apple,smc-reboot.yaml#
+$schema: http://devicetree.org/meta-schemas/core.yaml#
+
+title: Apple SMC Reboot Controller
+
+description: |
+  The Apple System Management Controller (SMC) provides reboot functionality
+  on Apple Silicon SoCs. It uses NVMEM cells to store and track various
+  system state information related to boot, shutdown, and panic events.
+
+maintainers:
+  - Sven Peter <sven@...npeter.dev>
+
+properties:
+  compatible:
+    const: apple,smc-reboot
+
+  nvmem-cells:
+    items:
+      - description: Flag indicating shutdown (as opposed to reboot)
+      - description: Stage at which the boot process stopped (0x30 for normal boot)
+      - description: Counter for boot errors
+      - description: Counter for system panics
+      - description: Power management settings
+
+  nvmem-cell-names:
+    items:
+      - const: shutdown_flag
+      - const: boot_stage
+      - const: boot_error_count
+      - const: panic_count
+      - const: pm_setting
+
+required:
+  - compatible
+  - nvmem-cells
+  - nvmem-cell-names
+
+additionalProperties: false
+
+examples:
+  - |
+    reboot {
+      compatible = "apple,smc-reboot";
+      nvmem-cells = <&shutdown_flag>, <&boot_stage>,
+                    <&boot_error_count>, <&panic_count>, <&pm_setting>;
+      nvmem-cell-names = "shutdown_flag", "boot_stage",
+                         "boot_error_count", "panic_count", "pm_setting";
+    };
diff --git a/MAINTAINERS b/MAINTAINERS
index 7f91f0225133490607ba0d79ad4225892ef31a66..d85d9d9065db4dc5869788f8a81d9d9a425d7ce3 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -2282,6 +2282,7 @@ F:	Documentation/devicetree/bindings/nvmem/apple,spmi-nvmem.yaml
 F:	Documentation/devicetree/bindings/pci/apple,pcie.yaml
 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/spi/apple,spi.yaml
 F:	Documentation/devicetree/bindings/spmi/apple,spmi.yaml

-- 
2.34.1