linux-kernel - [PATCH RFC v2 1/2] dt-bindings: power: add nexus map for power-domains

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Message-Id: <20250528-pmdomain-hierarchy-onecell-v2-1-7885ae45e59c@baylibre.com>
Date: Wed, 28 May 2025 14:58:51 -0700
From: Kevin Hilman <khilman@...libre.com>
To: Ulf Hansson <ulf.hansson@...aro.org>, Rob Herring <robh@...nel.org>, 
 Krzysztof Kozlowski <krzk+dt@...nel.org>, 
 Conor Dooley <conor+dt@...nel.org>, "Rafael J. Wysocki" <rjw@...ysocki.net>
Cc: linux-pm@...r.kernel.org, devicetree@...r.kernel.org, 
 linux-kernel@...r.kernel.org, arm-scmi@...r.kernel.org
Subject: [PATCH RFC v2 1/2] dt-bindings: power: add nexus map for
 power-domains

Add support for nexus map to be able to support hierarchical power
domains for providers with #power-domain-cells > 0.

Suggested-by: Rob Herring <robh@...nel.org>
Signed-off-by: Kevin Hilman <khilman@...libre.com>
---
 Documentation/devicetree/bindings/power/power-domain.yaml | 35 +++++++++++++++++++++++++++++++++++
 1 file changed, 35 insertions(+)

diff --git a/Documentation/devicetree/bindings/power/power-domain.yaml b/Documentation/devicetree/bindings/power/power-domain.yaml
index 8fdb529d560b..9f099d326aee 100644
--- a/Documentation/devicetree/bindings/power/power-domain.yaml
+++ b/Documentation/devicetree/bindings/power/power-domain.yaml
@@ -68,6 +68,15 @@ properties:
       by the given provider should be subdomains of the domain specified
       by this binding.
 
+  power-domains-map:
+    $ref: /schemas/types.yaml#/definitions/uint32-array
+    description:
+      Nexus node mapping property that establishes parent-child relationships
+      for PM domains using the format defined in the Device Tree specification
+      section 2.5.1. Each map entry consists of child domain specifier,
+      parent phandle, and optional parent specifier arguments. This property
+      is only supported for onecell providers (#power-domain-cells = 1).
+
 required:
   - "#power-domain-cells"
 
@@ -133,3 +142,29 @@ examples:
             min-residency-us = <7000>;
         };
     };
+
+  - |
+    // Example using power-domains-map for Nexus mapping
+    main_pd: power-controller@...70000 {
+        compatible = "foo,power-controller";
+        reg = <0x12370000 0x1000>;
+        #power-domain-cells = <0>;
+    };
+
+    wkup_pd: power-controller@...80000 {
+        compatible = "foo,power-controller";
+        reg = <0x12380000 0x1000>;
+        #power-domain-cells = <0>;
+    };
+
+    scmi_pds protocol@11 {
+        compatible = "arm,scmi-power-domain";
+        reg = <0x11>;
+        #power-domain-cells = <1>;
+        power-domains-map = <15 &main_pd>,
+                            <19 &wkup_pd>;
+    };
+
+    // In this example using Nexus node mapping:
+    // - Child domain 15 (scmi_pds 15) becomes a subdomain of main_pd
+    // - Child domain 19 (scmi_pds 19) becomes a subdomain of wkup_pd

-- 
2.49.0