Updated:
I check the frequency of the CPU by `cat /proc/cpuinfo`.

On Wed, Jan 19, 2022 at 9:23 AM 孙世龙 sunshilong <sunshilong369@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?