linux-kernel - [PATCH v3 1/2] dt-bindings: cpufreq: add bindings for virtual cpufreq

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Message-ID: <20230731174613.4133167-2-davidai@google.com>
Date:   Mon, 31 Jul 2023 10:46:08 -0700
From:   David Dai <davidai@...gle.com>
To:     "Rafael J. Wysocki" <rafael@...nel.org>,
        Viresh Kumar <viresh.kumar@...aro.org>,
        Rob Herring <robh+dt@...nel.org>,
        Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>,
        Conor Dooley <conor+dt@...nel.org>,
        Sudeep Holla <sudeep.holla@....com>,
        David Dai <davidai@...gle.com>,
        Saravana Kannan <saravanak@...gle.com>
Cc:     Quentin Perret <qperret@...gle.com>,
        Masami Hiramatsu <mhiramat@...gle.com>,
        Will Deacon <will@...nel.org>,
        Peter Zijlstra <peterz@...radead.org>,
        Vincent Guittot <vincent.guittot@...aro.org>,
        Marc Zyngier <maz@...nel.org>,
        Oliver Upton <oliver.upton@...ux.dev>,
        Dietmar Eggemann <dietmar.eggemann@....com>,
        Pavan Kondeti <quic_pkondeti@...cinc.com>,
        Gupta Pankaj <pankaj.gupta@....com>,
        Mel Gorman <mgorman@...e.de>, kernel-team@...roid.com,
        linux-pm@...r.kernel.org, devicetree@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: [PATCH v3 1/2] dt-bindings: cpufreq: add bindings for virtual cpufreq

Adding bindings to represent a virtual cpufreq device.

Virtual machines may expose MMIO regions for a virtual cpufreq device for
guests to read frequency information or to request frequency selection. The
virtual cpufreq device has an individual controller for each CPU.

Co-developed-by: Saravana Kannan <saravanak@...gle.com>
Signed-off-by: Saravana Kannan <saravanak@...gle.com>
Signed-off-by: David Dai <davidai@...gle.com>
---
 .../bindings/cpufreq/cpufreq-virtual.yaml     | 89 +++++++++++++++++++
 1 file changed, 89 insertions(+)
 create mode 100644 Documentation/devicetree/bindings/cpufreq/cpufreq-virtual.yaml

diff --git a/Documentation/devicetree/bindings/cpufreq/cpufreq-virtual.yaml b/Documentation/devicetree/bindings/cpufreq/cpufreq-virtual.yaml
new file mode 100644
index 000000000000..f377cfc972ca
--- /dev/null
+++ b/Documentation/devicetree/bindings/cpufreq/cpufreq-virtual.yaml
@@ -0,0 +1,89 @@
+# SPDX-License-Identifier: GPL-2.0-only OR BSD-2-Clause
+%YAML 1.2
+---
+$id: http://devicetree.org/schemas/cpufreq/cpufreq-virtual.yaml#
+$schema: http://devicetree.org/meta-schemas/core.yamll#
+
+title: Virtual CPUFreq
+
+maintainers:
+  - David Dai <davidai@...gle.com>
+  - Saravana Kannan <saravanak@...gle.com>
+
+description:
+  Virtual CPUFreq is a virtualized driver in guest kernels that sends frequency
+  selection of its vCPUs as a hint to the host through MMIO regions. The host
+  uses the hint to schedule vCPU threads and select physical CPU frequency. It
+  enables accurate Per-Entity Load Tracking for tasks running in the guest by
+  querying host CPU frequency unless a virtualized FIE (ex. AMU) exists.
+
+properties:
+  compatible:
+    const: virtual,cpufreq
+  reg:
+    maxItems: 1
+
+required:
+  - compatible
+  - reg
+
+additionalProperties: false
+
+examples:
+  - |
+    cpus {
+      #address-cells = <1>;
+      #size-cells = <0>;
+
+      cpu@0 {
+        compatible = "arm,arm-v8";
+        device_type = "cpu";
+        reg = <0x0>;
+        operating-points-v2 = <&opp_table0>;
+      };
+
+      cpu@1 {
+        compatible = "arm,arm-v8";
+        device_type = "cpu";
+        reg = <0x0>;
+        operating-points-v2 = <&opp_table1>;
+      };
+    };
+
+    opp_table0: opp-table-0 {
+      compatible = "operating-points-v2";
+
+      opp1098000000 {
+        opp-hz = /bits/ 64 <1098000000>;
+        opp-level = <1>;
+      };
+
+      opp1197000000 {
+        opp-hz = /bits/ 64 <1197000000>;
+        opp-level = <2>;
+      };
+    };
+
+    opp_table1: opp-table-1 {
+      compatible = "operating-points-v2";
+
+      opp1106000000 {
+        opp-hz = /bits/ 64 <1106000000>;
+        opp-level = <1>;
+      };
+
+      opp1277000000 {
+        opp-hz = /bits/ 64 <1277000000>;
+        opp-level = <2>;
+      };
+    };
+
+    soc {
+      #address-cells = <1>;
+      #size-cells = <1>;
+
+      cpufreq {
+        reg = <0x1040000 0x10>;
+        compatible = "virtual,cpufreq";
+      };
+    };
-- 
2.41.0.585.gd2178a4bd4-goog