On Fri, Jan 26, 2024 at 04:43:15PM -0800, David Dai wrote:
> 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. 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@xxxxxxxxxx>
> Signed-off-by: Saravana Kannan <saravanak@xxxxxxxxxx>
> Signed-off-by: David Dai <davidai@xxxxxxxxxx>
> ---
> .../cpufreq/qemu,cpufreq-virtual.yaml | 110 ++++++++++++++++++
> + const: qemu,virtual-cpufreq
Well, the filename almost matches the compatible.
> +
> + 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
> + contiguously and contain registers for controlling DVFS(Dynamic Frequency
> + and Voltage) characteristics. The size of the region is proportional to
> + total number of frequency domains. This device also needs the CPUs to
> + list their OPPs using operating-points-v2 tables. The OPP tables for the
> + CPUs should use normalized "frequency" values where the OPP with the
> + highest performance among all the vCPUs is listed as 1024 KHz. The rest
> + of the frequencies of all the vCPUs should be normalized based on their
> + performance relative to that 1024 KHz OPP. This makes it much easier to
> + migrate the VM across systems which might have different physical CPU
> + OPPs.
> +
> +required:
> + - compatible
> + - reg
> +
> +additionalProperties: false
> +
> +examples:
> + - |
> + // This example shows a two CPU configuration with a frequency domain
> + // for each CPU showing normalized performance points.
> + 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";
> +
> + opp64000 { opp-hz = /bits/ 64 <64000>; };
opp-64000 is the preferred form.
> + opp128000 { opp-hz = /bits/ 64 <128000>; };
> + opp192000 { opp-hz = /bits/ 64 <192000>; };
> + opp256000 { opp-hz = /bits/ 64 <256000>; };
> + opp320000 { opp-hz = /bits/ 64 <320000>; };
> + opp384000 { opp-hz = /bits/ 64 <384000>; };
> + opp425000 { opp-hz = /bits/ 64 <425000>; };
> + };
> +
> + opp_table1: opp-table-1 {
> + compatible = "operating-points-v2";
> +
> + opp64000 { opp-hz = /bits/ 64 <64000>; };
> + opp128000 { opp-hz = /bits/ 64 <128000>; };
> + opp192000 { opp-hz = /bits/ 64 <192000>; };
> + opp256000 { opp-hz = /bits/ 64 <256000>; };
> + opp320000 { opp-hz = /bits/ 64 <320000>; };
> + opp384000 { opp-hz = /bits/ 64 <384000>; };
> + opp448000 { opp-hz = /bits/ 64 <448000>; };
> + opp512000 { opp-hz = /bits/ 64 <512000>; };
> + opp576000 { opp-hz = /bits/ 64 <576000>; };
> + opp640000 { opp-hz = /bits/ 64 <640000>; };
> + opp704000 { opp-hz = /bits/ 64 <704000>; };
> + opp768000 { opp-hz = /bits/ 64 <768000>; };
> + opp832000 { opp-hz = /bits/ 64 <832000>; };
> + opp896000 { opp-hz = /bits/ 64 <896000>; };
> + opp960000 { opp-hz = /bits/ 64 <960000>; };
> + opp1024000 { opp-hz = /bits/ 64 <1024000>; };
> +
> + };
I don't recall your prior versions having an OPP table. Maybe it was
incomplete. You are designing the "h/w" interface. Why don't you make it
discoverable or implicit (fixed for the h/w)? Do you really need it if
the frequency is normalized?
Also, we have "opp-level" for opaque values that aren't Hz.
Rob
