linux-kernel - [PATCH v4 1/2] dt-bindings: cpufreq: add virtual cpufreq device

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Date:   Fri, 10 Nov 2023 17:49:29 -0800
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 v4 1/2] dt-bindings: cpufreq: add virtual cpufreq device

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 frequency domain.

Co-developed-by: Saravana Kannan <saravanak@...gle.com>
Signed-off-by: Saravana Kannan <saravanak@...gle.com>
Signed-off-by: David Dai <davidai@...gle.com>
---
 .../cpufreq/qemu,cpufreq-virtual.yaml         | 99 +++++++++++++++++++
 1 file changed, 99 insertions(+)
 create mode 100644 Documentation/devicetree/bindings/cpufreq/qemu,cpufreq-virtual.yaml

diff --git a/Documentation/devicetree/bindings/cpufreq/qemu,cpufreq-virtual.yaml b/Documentation/devicetree/bindings/cpufreq/qemu,cpufreq-virtual.yaml
new file mode 100644
index 000000000000..16606cf1fd1a
--- /dev/null
+++ b/Documentation/devicetree/bindings/cpufreq/qemu,cpufreq-virtual.yaml
@@ -0,0 +1,99 @@
+# SPDX-License-Identifier: GPL-2.0-only OR BSD-2-Clause
+%YAML 1.2
+---
+$id: http://devicetree.org/schemas/cpufreq/qemu,cpufreq-virtual.yaml#
+$schema: http://devicetree.org/meta-schemas/core.yaml#
+
+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. Each vCPU
+  is associated with a frequency domain which can be shared with other vCPUs.
+  Each frequency domain has its own set of registers for frequency controls.
+
+properties:
+  compatible:
+    const: qemu,virtual-cpufreq
+
+  reg:
+    maxItems: 1
+    description:
+      Address and size of region containing frequency controls for each of the
+      frequency domains. Regions for each frequency domain is placed
+      contiugously and contain registers for controlling DVFS(Dynamic Frequency
+      and Voltage) characteristics. The size of the region is proportional to
+      total number of frequency domains.
+
+required:
+  - compatible
+  - reg
+
+additionalProperties: false
+
+examples:
+  - |
+    // This example shows a two CPU configuration with a frequency domain
+    // for each CPU.
+    cpus {
+      #address-cells = <1>;
+      #size-cells = <0>;
+
+      cpu@0 {
+        compatible = "arm,armv8";
+        device_type = "cpu";
+        reg = <0x0>;
+        operating-points-v2 = <&opp_table0>;
+      };
+
+      cpu@1 {
+        compatible = "arm,armv8";
+        device_type = "cpu";
+        reg = <0x0>;
+        operating-points-v2 = <&opp_table1>;
+      };
+    };
+
+    opp_table0: opp-table-0 {
+      compatible = "operating-points-v2";
+      opp-shared;
+
+      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";
+      opp-shared;
+
+      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@...0000 {
+        compatible = "qemu,virtual-cpufreq";
+        reg = <0x1040000 0x10>;
+      };
+    };
-- 
2.42.0.869.gea05f2083d-goog