linux-kernel - [PATCH v4 5/9] dt-bindings: watchdog: renesas: Document `renesas,syscon-cpg-error-rst` property

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Message-ID: <20250210184910.161780-6-prabhakar.mahadev-lad.rj@bp.renesas.com>
Date: Mon, 10 Feb 2025 18:49:06 +0000
From: Prabhakar <prabhakar.csengg@...il.com>
To: Geert Uytterhoeven <geert+renesas@...der.be>,
	Michael Turquette <mturquette@...libre.com>,
	Stephen Boyd <sboyd@...nel.org>,
	Rob Herring <robh@...nel.org>,
	Krzysztof Kozlowski <krzk+dt@...nel.org>,
	Conor Dooley <conor+dt@...nel.org>,
	Wim Van Sebroeck <wim@...ux-watchdog.org>,
	Guenter Roeck <linux@...ck-us.net>,
	Magnus Damm <magnus.damm@...il.com>,
	Wolfram Sang <wsa+renesas@...g-engineering.com>
Cc: linux-renesas-soc@...r.kernel.org,
	linux-clk@...r.kernel.org,
	devicetree@...r.kernel.org,
	linux-kernel@...r.kernel.org,
	linux-watchdog@...r.kernel.org,
	Prabhakar <prabhakar.csengg@...il.com>,
	Biju Das <biju.das.jz@...renesas.com>,
	Fabrizio Castro <fabrizio.castro.jz@...esas.com>,
	Lad Prabhakar <prabhakar.mahadev-lad.rj@...renesas.com>
Subject: [PATCH v4 5/9] dt-bindings: watchdog: renesas: Document `renesas,syscon-cpg-error-rst` property

From: Lad Prabhakar <prabhakar.mahadev-lad.rj@...renesas.com>

The CPG block in the RZ/V2H(P) and RZ/G3E SoCs includes Error Reset Select
Registers (`CPG_ERRORRST_SELm`) and Error Reset Registers
(`CPG_ERROR_RSTm`). The `CPG_ERRORRST_SELm` register must be configured to
trigger a system reset in response to specific error conditions, while the
`CPG_ERROR_RSTm` registers store the error interrupt factors that caused
the system reset.

For the watchdog IP to trigger a system reset on a watchdog timer
underflow, the `CPG_ERRORRST_SEL2` and `CPG_ERROR_RST2` registers in the
CPG block must be configured. For example, setting `BIT(1)` in
`CPG_ERRORRST_SEL2` allows WDT1 to issue a system reset upon a watchdog
timer underflow. Similarly, `BIT(1)` in `CPG_ERROR_RST2` indicates whether
the system reset was caused by a WDT1 underflow. This functionality
enables the watchdog driver to configure the `CPG_ERRORRST_SEL2` register
and determine whether the system booted due to a `Power-on Reset` or a
`Watchdog Reset`.

To support this operation, add the `renesas,syscon-cpg-error-rst` property
to the WDT node. This property maps to the `syscon` CPG node, allowing the
watchdog driver to configure and retrieve the necessary reset information.

Additionally, this property is marked as required for the RZ/V2H(P) and
RZ/G3E SoC to ensure future compatibility and is explicitly disallowed
for other SoCs.

Signed-off-by: Lad Prabhakar <prabhakar.mahadev-lad.rj@...renesas.com>
---
Note, this change doesnt break any ABI, as the subsequent driver patch
handles the case elegantly if the `syscon` node is missing to handle
backward compatibility.

v3->v4
- Updated commit message

v2->v3
- No change

v1->v2
- Renamed `renesas,r9a09g057-syscon-wdt-errorrst` to `renesas,syscon-cpg-error-rst`
- Updated commit message
---
 .../bindings/watchdog/renesas,wdt.yaml          | 17 +++++++++++++++++
 1 file changed, 17 insertions(+)

diff --git a/Documentation/devicetree/bindings/watchdog/renesas,wdt.yaml b/Documentation/devicetree/bindings/watchdog/renesas,wdt.yaml
index 29ada89fdcdc..ca62ae8b1b0c 100644
--- a/Documentation/devicetree/bindings/watchdog/renesas,wdt.yaml
+++ b/Documentation/devicetree/bindings/watchdog/renesas,wdt.yaml
@@ -112,6 +112,19 @@ properties:

   timeout-sec: true

+  renesas,syscon-cpg-error-rst:
+    $ref: /schemas/types.yaml#/definitions/phandle-array
+    description:
+      The first cell is a phandle to the SYSCON entry required to obtain
+      the current boot status. The second cell specifies the CPG_ERROR_RSTm
+      register offset within the SYSCON, and the third cell indicates the
+      bit within the CPG_ERROR_RSTm register.
+    items:
+      - items:
+          - description: Phandle to the CPG node
+          - description: The CPG_ERROR_RSTm register offset
+          - description: The bit within CPG_ERROR_RSTm register of interest
+
 required:
   - compatible
   - reg
@@ -182,7 +195,11 @@ allOf:
       properties:
         interrupts: false
         interrupt-names: false
+      required:
+        - renesas,syscon-cpg-error-rst
     else:
+      properties:
+        renesas,syscon-cpg-error-rst: false
       required:
         - interrupts

-- 
2.43.0