Bug#890365: linux-image 4.14 messing up with CPU frequency

Package: linux-image-4.14.0-0.bpo.3-amd64

Distro: Debian 9 Stretch

When I try to set CPU frequency to the minimum, it doesn't work. This works perfectly with kernel 4.9.5 (but with 4.9.5 I cannot hibernate).

Steps to reproduce the bug:

Have this in your grub: GRUB_CMDLINE_LINUX_DEFAULT="intel_pstate=disable"

cpufreq-set -c 0 -g userspace

cpufreq-set -c 0 -f 400MHz

With kernel 4.9 this resulted in the cpu running cold and silently at 400 MHz (check with cpufreq-info or with mate indicator applet).

After updating to 4.14 (linux-image-4.14.0-0.bpo.3-amd64 and corresponding linux-header) the above mentioned use of cpufreq-set sets a variable frequency policy.

Remark: this is happening too in Ubuntu 16.04 with kernel 4.10 and 4.13, so probably the bug was introduced in 4.10.

(remark: reportbug is crashing in my system and that is why I send an email. See screen capture at https://unix.stackexchange.com/questions/424037/how-do-i-report-a-bug-to-debian-when-reportbug-crashes-because-it-has-itself-an)

Please send further instructions to provide any kind of log you need.

Thanks.

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Eduardo Guerras Valera

Homer L. Dodge Department of Physics and Astronomy

440 W. Brooks St. - Norman, OK 73019-0225 - USA

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