[RFC PATCH v2 5/6] dt-bindings: cpufreq: add bindings for virtual kvm cpufreq

[Rob Herring]

On Thu, Mar 30, 2023 at 8:45 PM David Dai <davidai at google.com> wrote:
>
> Add devicetree bindings for a virtual kvm cpufreq driver.
>
> Co-developed-by: Saravana Kannan <saravanak at google.com>
> Signed-off-by: Saravana Kannan <saravanak at google.com>
> Signed-off-by: David Dai <davidai at google.com>
> ---
>  .../bindings/cpufreq/cpufreq-virtual-kvm.yaml | 39 +++++++++++++++++++
>  1 file changed, 39 insertions(+)
>  create mode 100644 Documentation/devicetree/bindings/cpufreq/cpufreq-virtual-kvm.yaml
>
> diff --git a/Documentation/devicetree/bindings/cpufreq/cpufreq-virtual-kvm.yaml b/Documentation/devicetree/bindings/cpufreq/cpufreq-virtual-kvm.yaml
> new file mode 100644
> index 000000000000..31e64558a7f1
> --- /dev/null
> +++ b/Documentation/devicetree/bindings/cpufreq/cpufreq-virtual-kvm.yaml
> @@ -0,0 +1,39 @@
> +# SPDX-License-Identifier: GPL-2.0-only OR BSD-2-Clause
> +%YAML 1.2
> +---
> +$id: http://devicetree.org/schemas/cpufreq/cpufreq-virtual-kvm.yaml#
> +$schema: http://devicetree.org/meta-schemas/core.yaml#
> +
> +title: Virtual KVM CPUFreq
> +
> +maintainers:
> +  - David Dai <davidai at google.com>
> +
> +description: |
> +
> +  KVM CPUFreq is a virtualized driver in guest kernels that sends utilization
> +  of its vCPUs as a hint to the host. The host uses hint to schedule vCPU
> +  threads and select CPU frequency. It enables accurate Per-Entity Load
> +  Tracking for tasks running in the guest by querying host CPU frequency
> +  unless a virtualized FIE exists(Like AMUs).
> +
> +properties:
> +  compatible:
> +    const: virtual,kvm-cpufreq
> +
> +required:
> +  - compatible
> +
> +additionalProperties: false
> +
> +examples:
> +  - |
> +    {
> +      #address-cells = <2>;
> +      #size-cells = <2>;
> +
> +      cpufreq {
> +            compatible = "virtual,kvm-cpufreq";
> +      };

The same thing was tried on non-virtual h/w too. This is not a device
so it doesn't go in DT. It is just an abuse of DT as a kernel driver
instantiation mechanism.

Rob