37afb0003242 ("cpufreq: intel_pstate: Use ACPI perf configuration") makes intel_pstate kaputt

[Borislav Petkov <bp@alien8.de>]

Hi,

patch in $Subject breaks my IVB laptop here. It does not go over 1.2GHz
during load like building a kernel with -j4, for example. 1.2GHz
according to cpupower in tools/power/cpupower is the lowest P-state:

# LD_LIBRARY_PATH=. ./cpupower frequency-info
analyzing CPU 0:
  driver: intel_pstate
  CPUs which run at the same hardware frequency: 0
  CPUs which need to have their frequency coordinated by software: 0
  maximum transition latency: 0.97 ms.
  hardware limits: 1.20 GHz - 3.60 GHz
  available cpufreq governors: performance, powersave
  current policy: frequency should be within 1.20 GHz and 3.60 GHz.
                  The governor "powersave" may decide which speed to use
                  within this range.
  current CPU frequency is 1.20 GHz (asserted by call to hardware).
  boost state support:
    Supported: yes
    Active: yes
    3400 MHz max turbo 4 active cores
    3400 MHz max turbo 3 active cores
    3400 MHz max turbo 2 active cores
    3600 MHz max turbo 1 active cores
---

turbostat output during building a kernel is:

     CPU Avg_MHz   %Busy Bzy_MHz TSC_MHz
       -    1194   99.70    1200    2893
       0    1196   99.92    1200    2893
       1    1197   99.97    1200    2893
       2    1197   99.95    1200    2893
       3    1185   98.95    1200    2893

I've enabled the pr_debug's in intel_pstate_init_perf_limits() and it
says:

[    0.826111] intel_pstate: default limits 0xc 0x1d 0x24
[    0.829252] intel_pstate: CPU0 - ACPI _PSS perf data
[    0.830337] intel_pstate: Updated limits using _PSS 0xc 0x1d 0x24
[    0.830356] intel_pstate: policy max_freq=3600000 Khz min_freq = 1200000 KHz
[    0.830908] intel_pstate: default limits 0xc 0x1d 0x24
[    0.833002] intel_pstate: CPU1 - ACPI _PSS perf data
[    0.833339] intel_pstate: Updated limits using _PSS 0xc 0x1d 0x24
[    0.833361] intel_pstate: policy max_freq=3600000 Khz min_freq = 1200000 KHz
[    0.833535] intel_pstate: default limits 0xc 0x1d 0x24
[    0.835727] intel_pstate: CPU2 - ACPI _PSS perf data
[    0.836036] intel_pstate: Updated limits using _PSS 0xc 0x1d 0x24
[    0.836058] intel_pstate: policy max_freq=3600000 Khz min_freq = 1200000 KHz
[    0.836237] intel_pstate: default limits 0xc 0x1d 0x24
[    0.838432] intel_pstate: CPU3 - ACPI _PSS perf data
[    0.838731] intel_pstate: Updated limits using _PSS 0xc 0x1d 0x24
[    0.838753] intel_pstate: policy max_freq=3600000 Khz min_freq = 1200000 KHz

during boot.

When I boot with "intel_pstate=no_acpi" it boosts normally to 3.4GHz and
above and turbostat says:

     CPU Avg_MHz   %Busy Bzy_MHz TSC_MHz
       -    3392   99.92    3400    2895
       0    3395   99.96    3400    2897
       1    3390   99.88    3400    2895
       2    3391   99.89    3400    2895
       3    3391   99.95    3400    2893

which is what it should be saying. :)

Thanks.

-- 
Regards/Gruss,
    Boris.

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