linux-kernel - [RFC PATCH 2/3] dt-bindings: firmware: Document the MediaTek Hardware Voter (HWV)

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Message-ID: <20250701151149.136365-3-angelogioacchino.delregno@collabora.com>
Date: Tue,  1 Jul 2025 17:11:48 +0200
From: AngeloGioacchino Del Regno <angelogioacchino.delregno@...labora.com>
To: krzk@...nel.org
Cc: robh@...nel.org,
	conor+dt@...nel.org,
	matthias.bgg@...il.com,
	angelogioacchino.delregno@...labora.com,
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Subject: [RFC PATCH 2/3] dt-bindings: firmware: Document the MediaTek Hardware Voter (HWV)

Add documentation for the new MediaTek Hardware Voter, found in
MediaTek SoCs like the MT8196 Kompanio Ultra for Chromebooks and
the MT6991 Dimensity 9400 for Smartphones.

Signed-off-by: AngeloGioacchino Del Regno <angelogioacchino.delregno@...labora.com>
---
 .../mediatek,mt6991-hardware-voter.yaml       | 70 +++++++++++++++++++
 1 file changed, 70 insertions(+)
 create mode 100644 Documentation/devicetree/bindings/firmware/mediatek,mt6991-hardware-voter.yaml

diff --git a/Documentation/devicetree/bindings/firmware/mediatek,mt6991-hardware-voter.yaml b/Documentation/devicetree/bindings/firmware/mediatek,mt6991-hardware-voter.yaml
new file mode 100644
index 000000000000..173b74c23a91
--- /dev/null
+++ b/Documentation/devicetree/bindings/firmware/mediatek,mt6991-hardware-voter.yaml
@@ -0,0 +1,70 @@
+# SPDX-License-Identifier: (GPL-2.0 OR BSD-2-Clause)
+# Copyright 2025 Collabora Ltd
+%YAML 1.2
+---
+$id: http://devicetree.org/schemas/firmware/mediatek,mt6991-hardware-voter.yaml#
+$schema: http://devicetree.org/meta-schemas/core.yaml#
+
+title: MediaTek Hardware Voter (HWV)
+
+maintainers:
+  - AngeloGioacchino Del Regno <angelogioacchino.delregno@...labora.com>
+
+description:
+  The MediaTek Hardware Voter (HWV) is a SoC-internal fixed-function MCU
+  used to collect votes from both the Application Processor and from the
+  various other remote processors present in the SoC, and transparently
+  turn on or off various hardware resources (for example, power domains
+  or system clocks) based on aggregation of votes done in the HWV MCU's
+  internal state machine, therefore guaranteeing synchronization of the
+  hardware resource requests between all components of the SoC and hence
+  avoiding, for example, unclocked or unpowered access to the hardware.
+
+properties:
+  $nodename:
+    pattern: "^system-controller@[0-9a-f]+$"
+
+  compatible:
+    const: mediatek,mt6991-hardware-voter
+
+  reg:
+    items:
+      - description: Address and size of the Hardware Voter MMIO
+
+  power-controller:
+    $ref: /schemas/power/mediatek,power-controller.yaml
+
+required:
+  - compatible
+  - reg
+
+additionalProperties: true
+
+examples:
+ - |
+   scp_hwv: system-controller@...00000 {
+     compatible = "mediatek,mt6991-hardware-voter";
+     reg = <0 0x14500000 0 0x3000>;
+
+     power-controller {
+       compatible = "mediatek,mt8196-hwv-scp-power-controller";
+       #address-cells = <1>;
+       #size-cells = <0>;
+       #power-domain-cells = <1>;
+     };
+   };
+
+   /*
+    * For RFC patch only, this will be removed at patch v1
+    * Note 1: Clock controllers have more than 90 registers in HWV
+    * Note 2: The HWV integrates the power controller, so that's why
+    *         that is a child node of HWV, but the clock controllers
+    *         are completely separated (in hardware) from the HWV's
+    *         physical location (other than address space)... so it
+    *         would be wrong to place those as children of HWV I think.
+    */
+   clock-controller@...40000 {
+     comaptible = "mediatek,mt8196-pericfg-ao";
+     mediatek,hardware-voter = <&scp_hwv>;
+     #clock-cells = <1>;
+   };
-- 
2.49.0