linux-kernel - [PATCH v7 1/2] dt-bindings: cpufreq: add virtual cpufreq device

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Message-ID: <20240919000837.1004642-2-davidai@google.com>
Date: Wed, 18 Sep 2024 17:08:32 -0700
From: David Dai <davidai@...gle.com>
To: "Rafael J. Wysocki" <rafael@...nel.org>, Viresh Kumar <viresh.kumar@...aro.org>, 
	Rob Herring <robh@...nel.org>, Krzysztof Kozlowski <krzk+dt@...nel.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 v7 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 performance information or to request performance
selection. The virtual cpufreq device has an individual controller for
each performance domain. Performance points for a given domain can be
normalized across all domains for ease of allowing for virtual machines
to migrate between hosts.

Co-developed-by: Saravana Kannan <saravanak@...gle.com>
Signed-off-by: Saravana Kannan <saravanak@...gle.com>
Signed-off-by: David Dai <davidai@...gle.com>
Reviewed-by: Rob Herring (Arm) <robh@...nel.org>
---
 .../cpufreq/qemu,virtual-cpufreq.yaml         | 48 +++++++++++++++++++
 1 file changed, 48 insertions(+)
 create mode 100644 Documentation/devicetree/bindings/cpufreq/qemu,virtual-cpufreq.yaml

diff --git a/Documentation/devicetree/bindings/cpufreq/qemu,virtual-cpufreq.yaml b/Documentation/devicetree/bindings/cpufreq/qemu,virtual-cpufreq.yaml
new file mode 100644
index 000000000000..018d98bcdc82
--- /dev/null
+++ b/Documentation/devicetree/bindings/cpufreq/qemu,virtual-cpufreq.yaml
@@ -0,0 +1,48 @@
+# SPDX-License-Identifier: GPL-2.0-only OR BSD-2-Clause
+%YAML 1.2
+---
+$id: http://devicetree.org/schemas/cpufreq/qemu,virtual-cpufreq.yaml#
+$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 performance
+  selection of its vCPUs as a hint to the host through MMIO regions. Each vCPU
+  is associated with a performance domain which can be shared with other vCPUs.
+  Each performance domain has its own set of registers for performance controls.
+
+properties:
+  compatible:
+    const: qemu,virtual-cpufreq
+
+  reg:
+    maxItems: 1
+    description:
+      Address and size of region containing performance controls for each of the
+      performance domains. Regions for each performance domain is placed
+      contiguously and contain registers for controlling DVFS(Dynamic Frequency
+      and Voltage) characteristics. The size of the region is proportional to
+      total number of performance domains.
+
+required:
+  - compatible
+  - reg
+
+additionalProperties: false
+
+examples:
+  - |
+    soc {
+      #address-cells = <1>;
+      #size-cells = <1>;
+
+      cpufreq@...0000 {
+        compatible = "qemu,virtual-cpufreq";
+        reg = <0x1040000 0x2000>;
+      };
+    };
-- 
2.46.0.792.g87dc391469-goog