About the kernel configuration(CONFIG_CPU_FREQ and CONFIG_CPU_IDLE.)

[jim.cromie at gmail.com]

On Tue, Jan 18, 2022 at 6:23 PM 孙世龙 sunshilong <sunshilong369 at gmail.com> wrote:
>
> Hi, list
> I am using Linux 5.4.78 with PREEMPT_RT patch.
> Hardware name: UNO-2372G-J021AE.
>
> It's strange that the frequency of the CPU is not constant(i.e.
> not fixed at a specific frequency) if I both disable CONFIG_CPU_FREQ
> and CONFIG_CPU_IDLE
> whereas
> the frequency of the CPU is constant if I only disable CONFIG_CPU_FREQ
> (leave CONFIG_CPU_IDLE enabled).
>
> Could somebody please shed some light on this matter?

just a WAG, but

lower power draw has been hugely important for years,
nobody would sacrifice that for "simplicity", such a feature would be unused.
I could imagine enterprise SMM bios disallowing such operation.

On dozens of processors over time, TSC has been marked unstable
by the kernel, Id suppose that signals a certain distrust of some clocks.