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Date:   Thu, 16 Jun 2022 09:27:38 +0000
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Subject: [PATCH v6 1/2] dt-bindings: vcpu_stall_detector: Add
 qemu,vcpu-stall-detector compatible
From:   Sebastian Ene <sebastianene@google.com>
To:     Rob Herring <robh+dt@kernel.org>,
        Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        Arnd Bergmann <arnd@arndb.de>,
        Dragan Cvetic <dragan.cvetic@xilinx.com>
Cc:     linux-kernel@vger.kernel.org, devicetree@vger.kernel.org,
        maz@kernel.org, will@kernel.org, vdonnefort@google.com,
        Guenter Roeck <linux@roeck-us.net>,
        Sebastian Ene <sebastianene@google.com>
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Precedence: bulk

The VCPU stall detection mechanism allows to configure the expiration
duration and the internal counter clock frequency measured in Hz.
Add these properties in the schema.

While this is a memory mapped virtual device, it is expected to be loaded
when the DT contains the compatible: "qemu,vcpu-stall-detector" node.
In a protected VM we trust the generated DT nodes and we don't rely on
the host to present the hardware peripherals.

Signed-off-by: Sebastian Ene <sebastianene@google.com>
---
 .../bindings/misc/vcpu_stall_detector.yaml    | 49 +++++++++++++++++++
 1 file changed, 49 insertions(+)
 create mode 100644 Documentation/devicetree/bindings/misc/vcpu_stall_detector.yaml

diff --git a/Documentation/devicetree/bindings/misc/vcpu_stall_detector.yaml b/Documentation/devicetree/bindings/misc/vcpu_stall_detector.yaml
new file mode 100644
index 000000000000..55323676194b
--- /dev/null
+++ b/Documentation/devicetree/bindings/misc/vcpu_stall_detector.yaml
@@ -0,0 +1,49 @@
+# SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause)
+%YAML 1.2
+---
+$id: http://devicetree.org/schemas/misc/vcpu_stall_detector.yaml#
+$schema: http://devicetree.org/meta-schemas/core.yaml#
+
+title: VCPU stall detector
+
+description: |
+  This binding describes a CPU stall detector mechanism for virtual cpus
+  which is accessed through MMIO.
+
+maintainers:
+  - Sebastian Ene <sebastianene@google.com>
+
+properties:
+  compatible:
+    enum:
+      - qemu,vcpu-stall-detector
+
+  clock-frequency:
+    $ref: /schemas/types.yaml#/definitions/uint32
+    description: |
+      The internal clock of the stall detector peripheral measure in Hz used
+      to decrement its internal counter register on each tick.
+      Defaults to 10 if unset.
+
+  timeout-sec:
+    $ref: /schemas/types.yaml#/definitions/uint32
+    description: |
+      The stall detector expiration timeout measured in seconds.
+      Defaults to 8 if unset. Please note that it also takes into account the
+      time spent while the VCPU is not running.
+
+required:
+  - compatible
+
+additionalProperties: false
+
+examples:
+  - |
+    vmwdt@9030000 {
+      compatible = "qemu,vcpu-stall-detector";
+      clock-frequency = <10>;
+      timeout-sec = <8>;
+      reg = <0x0 0x9030000 0x0 0x10000>;
+    };
+
+...
-- 
2.36.1.476.g0c4daa206d-goog