https://bugzilla.kernel.org/show_bug.cgi?id=210993

--- Comment #6 from Karol Herbst (karolherbst@gmail.com) ---

(In reply to Francisco Jerez from comment #5)

O_o, that's really weird. I guess this could also be some sort of
electromagnetic interference (E.g. with your soundcard?  Does the problem
occur with the loudspeakers turned off?), or an issue with your PSU.

It is very quiet. Definitely you can hear it only with slowly spinning fans and
no background noise. Searching through the web it sounds like a common issue
and disabling sleep states is supposed to be the proper "fix" for this.

But at least muting the speakers don't help.

The apparent frequency dropping below scaling_min_freq might be an artifact
of how the busy frequency of a CPU thread is calculated: It should
approximate the ratio of executed clock cycles to the time it spent in C0
state, which can deviate from its actual working frequency if the processor
enters and exits some C1+ state repeatedly since the transition may have
some significant latency.  According to your turbostat log the CPU cores
that report a busy frequency below scaling_min_freq seem to be handling
quite a few interrupts which is consistent with that explanation.  It
doesn't necessarily indicate a power management bug.

Does disabling some specific idle state (e.g via
/sys/devices/system/cpu/cpu*/cpuidle/state*/disable) have any effect on the
noise?

disabling all except state0 stops the noise.

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