NACK[M]: [SRU J/L/M][PATCH 0/1] Unable to Interpret the Frequency Values in Cpuinfo_min_freq and Cpuino_max_freq Sysfs Files

[Andrea Righi]

On Thu, Aug 10, 2023 at 11:48:13AM -0500, Michael Reed wrote:
> From: Michael Reed <Michael.Reed at canonical.com>
> 
> BugLink: https://bugs.launchpad.net/bugs/2030924
> 
> SRU Justification:
> 
> [Impact]
> 
> On DELL EMC PowerEdge system when Ubuntu 22.04.1 OS is Installed, Unable to Interpret the values in cpuinfo_max_freq and cpuinfo_min_freq sysfs files as per the Intel specs document.
> 
> Steps to Reproduce:
> 
> 1. Install one CPU that supports DBS "Demand-Based Power Management".
> 2. Install Ubuntu 22.04.1 OS.
> 2. Enable "Logical Processor" under CPU Information menu from F2 setup.
> 3. Save changes and reboot to Ubuntu 22.04.1 OS.
> 4. Right click on "Computer" and select "File system" and check for the following CPU directories.
> 
>    /sys/devices/system/cpu/cpu0/cpufreq/cpu0
>    /sys/devices/system/cpu/cpu0/cpufreq/cpu1
> 
> 5. View the Max Frequency and Min Frequency under CPU0 and CPU1 directory.
> 6. The Max and Min Frequency did not match as per the Intel specs datasheet.
> 
> Actual results:
> 
>  /sys/devices/system/cpu/cpu0/cpufreq/cpu0/cpuinfo_max_freq -> 6800000
>  /sys/devices/system/cpu/cpu0/cpufreq/cpu0/cpuinfo_min_freq -> 800000
>  /sys/devices/system/cpu/cpu0/cpufreq/cpu0/base_frequency -> 3900000
> 
>  Expected results: As per Intel datasheet specification.
> 
>  /sys/devices/system/cpu/cpu0/cpufreq/cpu0/cpuinfo_max_freq -> 5300 MHz
>  /sys/devices/system/cpu/cpu0/cpufreq/cpu0/cpuinfo_min_freq -> 800 MHz
>  /sys/devices/system/cpu/cpu0/cpufreq/cpu0/base_frequency -> 3000 MHz
> 
> [Fix]
> cpufreq: intel_pstate: Fix scaling for hybrid-capable systems with disabled E-cores
> https://github.com/torvalds/linux/commit/0fcfc9e51990246a9813475716746ff5eb98c6aa [github.com]
> 
> [Test Plan]
> 
> Same as steps to reproduce
> 
> [ Where problems could occur ]
> 
> This issue is seen on Intel based system under development which supports DBS "Demand-Based Power Management", then install Ubuntu-22.04 and boot into OS then
> check for the frequency values under /sys/devices/system/cpu/cpu0/cpufreq/cpu0
> Regression risk = Low to medium
> 
> [ Other Info ]
> 
> Jammy
> https://code.launchpad.net/~mreed8855/ubuntu/+source/linux/+git/jammy/+ref/cpuinfo_freq
> 
> lunar
> https://code.launchpad.net/~mreed8855/ubuntu/+source/linux/+git/lunar/+ref/cpuinfo_freq_lunar_2
> 
> Mantic
> https://code.launchpad.net/~mreed8855/ubuntu/+source/linux/+git/mantic/+ref/cpuinfo_freq_mantic

Already applied to mantic/linux-unstable via periodic upstream rebase.

Thanks,
-Andrea