RE: [PATCH v2 0/6] cpufreq: intel_pstate: Set cpuinfo_min_freq to a lower value with HWP enabled plus cleanups

[Doug Smythies]

On 2026.06.19 10:32 Rafael wrote:

> This is in v2 because technically it is an update of
>
> https://lore.kernel.org/linux-pm/2381464.iZASKD2KPV@rafael.j.wysocki/
>
> but it contains new patches.
>
> This series updates the intel_pstate driver to set cpuinfo_min_freq to a lower
> value when HWP is enabled to support systems in which CPUs can actually run
> at performance levels below the current minimum level.
>
> It also carries out some code cleanups, mostly related to HWP, either in
> preparation for the functional changes or top of them.
>
> Thanks!

Hi Rafael,

Is there a way to test this? I have tried everything I can think of and have
been unable to get the processor frequency below the old minimum of 800 MHz.
No matter what I do, I always see greater or equal to 8 for each CPU in the
IA32_PERF_STATUS register, or by looking at non stale entries in:

grep . /sys/devices/system/cpu/cpu*/cpufreq/scaling_cur_freq

Example:
doug@s19:~$ grep . /sys/devices/system/cpu/cpu*/cpufreq/scaling_cur_freq
/sys/devices/system/cpu/cpu0/cpufreq/scaling_cur_freq:100000
/sys/devices/system/cpu/cpu10/cpufreq/scaling_cur_freq:100000
/sys/devices/system/cpu/cpu11/cpufreq/scaling_cur_freq:100000
/sys/devices/system/cpu/cpu1/cpufreq/scaling_cur_freq:800013
/sys/devices/system/cpu/cpu2/cpufreq/scaling_cur_freq:800014
/sys/devices/system/cpu/cpu3/cpufreq/scaling_cur_freq:799996
/sys/devices/system/cpu/cpu4/cpufreq/scaling_cur_freq:800023
/sys/devices/system/cpu/cpu5/cpufreq/scaling_cur_freq:800053
/sys/devices/system/cpu/cpu6/cpufreq/scaling_cur_freq:100000
/sys/devices/system/cpu/cpu7/cpufreq/scaling_cur_freq:100000
/sys/devices/system/cpu/cpu8/cpufreq/scaling_cur_freq:100000
/sys/devices/system/cpu/cpu9/cpufreq/scaling_cur_freq:100000

Readers note:
Stale entries are just "scaling_min_freq".
Non-stale entries tend to be not nice round numbers.

For me this patch set introduces confusion between min and max
frequency settings and what I actually get. I can set " scaling_min_freq"
to 100 MHz and "scaling_max_freq" to 100MHz, but never get them.
Before this patch set, I always got what I asked for.

Other details:
Processor: Intel(R) Core(TM) i5-10600K CPU @ 4.10GHz
MSR_PLATFORM_INFO (0x0ce) 808083af1012900
Other stuff from my msr0decoder program:
doug@s19:~$ sudo c/msr-decoder
How many CPUs?: 12
8.) 0x198: IA32_PERF_STATUS     : CPU 11-0 :   8 :   8 :   8 :   8 :   8 :   8 :   8 :   8 :   8 :   8 :   8 :   8 :
B.) 0x770: IA32_PM_ENABLE: 1 : HWP enable
1.) 0x19C: IA32_THERM_STATUS: 88470000
2.) 0x1AA: MSR_MISC_PWR_MGMT: 401CC0 EIST enabled Coordination enabled OOB Bit 8 reset OOB Bit 18 reset
3.) 0x1B1: IA32_PACKAGE_THERM_STATUS: 88450000
4.) 0x64F: MSR_CORE_PERF_LIMIT_REASONS: 200000 RATLL
A.) 0x1FC: MSR_POWER_CTL: 3C005D : C1E disable : EEO disable : RHO disable
5.) 0x771: IA32_HWP_CAPABILITIES (performance): 10B2930 : high 48 : guaranteed 41 : efficient 11 : lowest 1
6.) 0x774: IA32_HWP_REQUEST:    CPU 11-0 :
    raw: 80010101 : 80010101 : 80010101 : 80010101 : 80010101 : 80010101 : 80010101 : 80010101 : 80010101 : 80010101 : 80010101 : 80010101 :
    min:        1 :        1 :        1 :        1 :        1 :        1 :        1 :        1 :        1 :        1 :        1 :        1 :
    max:        1 :        1 :        1 :        1 :        1 :        1 :        1 :        1 :        1 :        1 :        1 :        1 :
    des:        1 :        1 :        1 :        1 :        1 :        1 :        1 :        1 :        1 :        1 :        1 :        1 :
    epp:      128 :      128 :      128 :      128 :      128 :      128 :      128 :      128 :      128 :      128 :      128 :      128 :
    act:        0 :        0 :        0 :        0 :        0 :        0 :        0 :        0 :        0 :        0 :        0 :        0 :
7.) 0x777: IA32_HWP_STATUS: 0 : high 0 : guaranteed 0 : efficient 0 : lowest 0

The driver was intel_cpufreq, governor conservative (but I tried them all). I also tried epp = 255 so as to slow down the processor response time.

... Doug