Ubuntu: Can't scale frequencies of AMD Turion CPU, it always jumps to lowest



Question:

I have similar problem to this: Can't scale frequencies, always jumps to lowest .

This time on a HP Compaq 6715B notebook with AMD Turion CPU TL-58 and powernow-k8 cpufreq driver :

$ cpufreq-info   cpufrequtils 008: cpufreq-info (C) Dominik Brodowski 2004-2009  Report errors and bugs to cpufreq@vger.kernel.org, please.  analyzing CPU 0:    driver: powernow-k8    CPUs which run at the same hardware frequency: 0 1    CPUs which need to have their frequency coordinated by software: 0 1    maximum transition latency: 109 us.    hardware limits: 800 MHz - 1.90 GHz    available frequency steps: 1.90 GHz, 1.80 GHz, 1.60 GHz, 800 MHz    available cpufreq governors: conservative, ondemand, userspace, powersave, performance    current policy: frequency should be within 800 MHz and 800 MHz.                    The governor "ondemand" may decide which speed to use                    within this range.    current CPU frequency is 800 MHz.    cpufreq stats: 1.90 GHz:0,07%, 1.80 GHz:0,00%, 1.60 GHz:0,00%, 800 MHz:99,93%  (1)  analyzing CPU 1:    driver: powernow-k8    CPUs which run at the same hardware frequency: 0 1    CPUs which need to have their frequency coordinated by software: 0 1    maximum transition latency: 109 us.    hardware limits: 800 MHz - 1.90 GHz    available frequency steps: 1.90 GHz, 1.80 GHz, 1.60 GHz, 800 MHz    available cpufreq governors: conservative, ondemand, userspace, powersave, performance    current policy: frequency should be within 800 MHz and 800 MHz.                    The governor "ondemand" may decide which speed to use                    within this range.    current CPU frequency is 800 MHz.    cpufreq stats: 1.90 GHz:0,07%, 1.80 GHz:0,00%, 1.60 GHz:0,00%, 800 MHz:99,93%  (1)  

The solution in cited post above does not work nor other solutions that was found in the Internet. The BIOS does not impose any limits on the OS (as seen in other solutions due to battery/power supply problems). The CPU scaling in Windows Vista works correctly (so this should not be any hardware problem). Setting the performance governor does not work too.

$uname -a  Linux kaspat 4.2.0-27-generic #32~14.04.1-Ubuntu SMP Fri Jan 22 15:32:26 UTC 2016 x86_64 x86_64 x86_64 GNU/Linux      lsb_release -a  No LSB modules are available.  Distributor ID: Ubuntu  Description:    Ubuntu 14.04.4 LTS  Release:        14.04  Codename:       trusty  
  1. How can I correct the powernow-k8 behavior ?
  2. Alternatively can I switch off powernow-k8 in favor of acpi-cpufreq without recompiling kernel ?

update 1: I filled a kernel bug: https://bugs.launchpad.net/ubuntu/+source/linux-lts-wily/+bug/1598312


Solution:1

I had an answer here. I wanted to tick it as a correct answer but it was removed (by answer's author ?). The answer was a workaround to the problem. I am going to repeat it below. Maybe it can help somebody else:

The CPU frequency scaling works after adding acpi=off to the kernel boot parameters but there is downside: only 1 processor core.

To have all cores and CPU frequency scaling one need to downgrade the kernel to 4.1.26. http://kernel.ubuntu.com/~kernel-ppa/mainline/v4.1.26-wily/ .

As a side note: Using this kernel version I had some troubles with WiFi driver (b43). It does not load automatically by NetworkManager, but it must be loaded manually in rc.local .


Solution:2

Setting acpi=noirq for kernel boot parameters enables the possibilities to have the kernel scale the CPU frequency correctly on the newer kernels.


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