Re: [PATCH V3 0/4] cpufreq: cppc: Add support for frequency invariance

[Qian Cai]

On 6/25/2021 6:21 AM, Ionela Voinescu wrote:
>> scaling_driver: acpi_cppc
>                   ^^^^^^^^^
> I suppose you mean "cppc-cpufreq"?
> 
> "acpi_cppc" is not a scaling driver option.

Ionela, yes. Sorry about that.

> So your CPUs run at frequencies between 200MHz and 280MHz?

2000 to 2800 MHz.

> Based on your acpi_cppc information below I would have assumed 2GHz as
> lowest nonlinear and 2.8GHz as nominal. The reason for this is that
> according to the ACPI spec the frequency values in the _CPC objects are
> supposed to be in MHz, so 2800 MHz for nominal frequency would be
> 2.8GHz.
> 
> When you try more governors, make sure to check out the difference
> between scaling_cur_freq and cpuinfo_cur_freq at [2]. The first gives
> you the frequency that the governor (schedutil) is asking for, while the
> second is giving you the current frequency obtained from the counters.
> 
> So to check the actual frequency the cores are running at, please check
> cpuinfo_cur_freq.

The problem is that all CPUs are never scaling down. "cpuinfo_cur_freq" and "scaling_cur_freq" are always the 2800 MHz on all CPUs on this idle system. This looks like a regression somewhere as in 5.4-based kernel, I can see "cpuinfo_cur_freq" can go down to 2000 MHz in the same scenario. I'll bisect a bit unless you have better ideas?