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~tfa

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From: Germany

Registered: 2021-11-03

Posts: 14

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Question: mainline amd_pstate driver

Hello community,

I hope I picked the right subforum.

I have compiled the latest mainline kernel 5.17-rc1 with the amd_pstate driver. It seeems to be working, my battery power draw got down by 0,1 amps on idle, compared with the lts kernel, I used before. Yet the lowest posible clock frequency achieved is 1,4 Ghz. cpupower gives me a variable frequency from 400 Mhz - 2900 Mhz, yet the clock will always cling to 1,4 Ghz on idle.

I am on a 4800H, laptop is a tuxedo, so pretty freely configurable and its a UEFI system, no dual boot.

$ sudo cpupower frequency-info
CPU 0 wird analysiert:
driver: amd-pstate
CPUs, die mit der gleichen Hardwarefrequenz laufen: 0
CPUs, die ihre Frequenz mit Software koordinieren müssen: 0
Maximale Dauer eines Taktfrequenzwechsels: 131 us
Hardwarebegrenzungen: 400 MHz - 2.90 GHz
verfügbare cpufreq-Regler: conservative ondemand userspace powersave performance schedutil
momentane Richtlinie: Frequenz sollte innerhalb 400 MHz und 2.90 GHz.
sein. Der Regler "ondemand" kann frei entscheiden,
welche Geschwindigkeit er in diesem Bereich verwendet.
current CPU frequency: Unable to call hardware
current CPU frequency: 1.41 GHz (asserted by call to kernel)
boost state support:
Unterstützt: ja
Aktiv: ja
Boost-Zustände: 0
Gesamtzustände: 3
Pstate-P0:  2900MHz
Pstate-P1:  1700MHz
Pstate-P2:  1400MHz

Hope you get the main points, tho its mixed with another language.

I figured this:

$ cat /sys/devices/system/cpu/cpufreq/policy0/amd_pstate_lowest_nonlinear_freq
1416000
$ cat /sys/devices/system/cpu/cpufreq/policy0/scaling_min_freq
400000

So lowest nonlinear freq is the only option giving the 1,4 Ghz.
Furthermore:

cat /sys/devices/system/cpu/cpu0/acpi_cppc/lowest_nonlinear_perf
84

So it seems like the value 1,4 Ghz is derived from the ACPI spec: https://www.kernel.org/doc/html/latest/ … sysfs.html

Now my question, do I need to change this (if I can at all) or is the processor just meant to be run at 1,4 Ghz and all is fine ?

Thank you and greetings,
~tfa