[RFC PATCH v3 1/3] dt-bindings: mfd: rk808: add board level power hold GPIOs

[Yaozhong Li <yaozhonguwl@gmail.com>]

Some boards route "power hold" lines from the SoC into the board's power
circuitry. Those lines have to be held asserted while the system is
running and released before the PMIC shutdown request is written,
otherwise the rails can drop and come back up instead of staying off.

Add power-hold-gpios to describe those lines and power-hold-delay-ms for
the settle time.

The array is bounded at two entries. Firefly's vendor kernel handles
exactly two such lines, pmic,hold-gpio and pmic,stby-gpio, and its board
files use one or both of them.

The lines are released from the PMIC's power-off path, so they are only
meaningful when the PMIC is the system power controller. Require that,
accepting both the current and the deprecated spelling of the property.

Assisted-by: LLM
Signed-off-by: Yaozhong Li <yaozhonguwl@gmail.com>
---
 .../bindings/mfd/rockchip,rk808.yaml          | 27 +++++++++++++++++++
 1 file changed, 27 insertions(+)

diff --git a/Documentation/devicetree/bindings/mfd/rockchip,rk808.yaml b/Documentation/devicetree/bindings/mfd/rockchip,rk808.yaml
index 50dfffa..9120222 100644
--- a/Documentation/devicetree/bindings/mfd/rockchip,rk808.yaml
+++ b/Documentation/devicetree/bindings/mfd/rockchip,rk808.yaml
@@ -43,6 +43,24 @@ properties:
 
   system-power-controller: true
 
+  power-hold-gpios:
+    minItems: 1
+    maxItems: 2
+    description:
+      Board level power hold lines driven by the SoC. They have to be held
+      asserted while the system is running and released before the PMIC
+      shutdown request is written, otherwise the rails can drop and come
+      back up instead of staying off. Only meaningful when this PMIC is the
+      system power controller, through either system-power-controller or
+      the deprecated rockchip,system-power-controller, as the lines are
+      released as part of its power-off path.
+
+  power-hold-delay-ms:
+    default: 0
+    description:
+      Time to wait after releasing power-hold-gpios before the shutdown
+      request is written, to let the lines settle.
+
   wakeup-source:
     type: boolean
     description:
@@ -113,6 +131,15 @@ properties:
         unevaluatedProperties: false
     unevaluatedProperties: false
 
+dependencies:
+  power-hold-delay-ms: [ power-hold-gpios ]
+
+dependentSchemas:
+  power-hold-gpios:
+    anyOf:
+      - required: [ system-power-controller ]
+      - required: [ 'rockchip,system-power-controller' ]
+
 required:
   - compatible
   - reg
-- 
2.55.0.windows.3