On modern Intel platforms, the intel_pstate driver is commonly used and
it provides turbo boost control via
/sys/devices/system/cpu/intel_pstate/no_turbo.

However, cpupower doesn't handle this. it
1. shows turbo boost as "active" blindly for Intel platforms
2. controls turbo boost functionality via the generic
   /sys/devices/system/cpu/cpufreq/boost sysfs interface only.

Enhance the cpupower tool to ensure the "--boost" command works
seamlessly on Intel platforms with intel_pstate driver running.

Without this patch,
   $ echo 1 | sudo tee /sys/devices/system/cpu/intel_pstate/no_turbo
   1
   $ sudo cpupower frequency-info --boost
   analyzing CPU 21:
     boost state support:
       Supported: yes
       Active: yes
   $ sudo cpupower set --boost 0
   Error setting turbo-boost
   $ sudo cpupower set --boost 1
   Error setting turbo-boost

With this patch,
   $ cat /sys/devices/system/cpu/intel_pstate/no_turbo
   0
   $ sudo cpupower set --boost 0
   $ sudo cpupower frequency-info --boost
   analyzing CPU 21:
     boost state support:
       Supported: yes
       Active: no
   $ cat /sys/devices/system/cpu/intel_pstate/no_turbo
   1
   $ sudo cpupower set --boost 1
   $ sudo cpupower frequency-info --boost
   analyzing CPU 28:
     boost state support:
       Supported: yes
       Active: yes
   $ cat /sys/devices/system/cpu/intel_pstate/no_turbo
   0

Signed-off-by: Zhang Rui <rui.zhang@intel.com>
Signed-off-by: Shuah Khan <skhan@linuxfoundation.org>

Extend the systemd service so that it can be used for tuning the Energy
Performance Preference (EPP) as well. Available options can be read from
/sys/devices/system/cpu/cpufreq/policy0/energy_performance_available_preferences.
The desired one can then be set in cpupower-service.conf.

Signed-off-by: Jan Kiszka <jan.kiszka@siemens.com>
Signed-off-by: Shuah Khan <skhan@linuxfoundation.org>

Fix error where microWatts and microJoules units were interchanged.

Signed-off-by: Kaushlendra Kumar <kaushlendra.kumar@intel.com>
Signed-off-by: Shuah Khan <skhan@linuxfoundation.org>

cpupower currently installs a cpupower.service unit file into unitdir
unconditionally, regardless of whether systemd is used by the host.

Improve the installation procedure by making this systemd step optional:
a 'SYSTEMD' build parameter that defaults to 'true' and can be set to
'false' to disable the installation of systemd's unit file.

Since 'SYSTEMD' defaults to true, the current behavior is kept as the
default.

Link: https://lore.kernel.org/r/20260113132753.1730020-2-joaomarcos.costa@bootlin.com
Signed-off-by: João Marcos Costa <joaomarcos.costa@bootlin.com>
Signed-off-by: Shuah Khan <skhan@linuxfoundation.org>

`cpupower idle-info -o` skipped C0 because the loop began at 1:

  before:
    states:
      C1 ... latency[002] residency[00002]
      C2 ... latency[010] residency[00020]
      C3 ... latency[133] residency[00600]

  after:
    states:
      C0 ... latency[000] residency[00000]
      C1 ... latency[002] residency[00002]
      C2 ... latency[010] residency[00020]
      C3 ... latency[133] residency[00600]

Start iterating at index 0 so the idle report mirrors sysfs and
includes C0 stats.

Link: https://lore.kernel.org/r/20251202065403.1492807-1-kaushlendra.kumar@intel.com
Signed-off-by: Kaushlendra Kumar <kaushlendra.kumar@intel.com>
Signed-off-by: Shuah Khan <skhan@linuxfoundation.org>

cpuidle_state_get_one_value() never cleared errno before calling
strtoull(), so a prior ERANGE caused every cpuidle counter read to
return zero. Reset errno to 0 before the conversion so each sysfs read
is evaluated independently.

Link: https://lore.kernel.org/r/20251201121745.3776703-1-kaushlendra.kumar@intel.com
Signed-off-by: Kaushlendra Kumar <kaushlendra.kumar@intel.com>
Signed-off-by: Shuah Khan <skhan@linuxfoundation.org>

Replace manual newline removal with strcspn() which is safer and
cleaner. This avoids potential out-of-bounds access on empty strings
and handles the case where no newline exists.

Link: https://lore.kernel.org/r/20251127044536.715722-1-kaushlendra.kumar@intel.com
Signed-off-by: Kaushlendra Kumar <kaushlendra.kumar@intel.com>
Signed-off-by: Shuah Khan <skhan@linuxfoundation.org>

The capability check was inverted, causing the function to return
error when APERF support is available and proceed when it is not.

Negate the condition to return error only when APERF capability
is absent.

Link: https://lore.kernel.org/r/20251126091613.567480-1-kaushlendra.kumar@intel.com
Signed-off-by: Kaushlendra Kumar <kaushlendra.kumar@intel.com>
Signed-off-by: Shuah Khan <skhan@linuxfoundation.org>

The cpuidle sysfs monitor printed the previous sample’s counter
value in cpuidle_stop() instead of the freshly read one. The dprint
line used previous_count[cpu][state] while current_count[cpu][state]
had just been populated. This caused misleading debug output.

Switch the logging to current_count so the post-interval snapshot
matches the displayed value.

Link: https://lore.kernel.org/r/20251202044012.3844790-1-kaushlendra.kumar@intel.com
Signed-off-by: Kaushlendra Kumar <kaushlendra.kumar@intel.com>
Signed-off-by: Shuah Khan <skhan@linuxfoundation.org>

The cpupower Makefile built and installed libcpupower as a shared
library (libcpupower.so) without passing `STATIC=true`, but did not
build a static version of the library even with `STATIC=true`. (Only the
programs were static). Thus, out-of-tree programs using libcpupower
were unable to link statically against the library without having access
to intermediate object files produced during the build.

This fixes that situation by ensuring that libcpupower.a is built and
installed when `STATIC=true` is specified.

Link: https://lore.kernel.org/r/x7geegquiks3zndiavw2arihdc2rk7e2dx3lk7yxkewqii6zpg@tzjijqxyzwmu
Signed-off-by: Zuo An <zuoan.penguin@gmail.com>
Signed-off-by: Shuah Khan <skhan@linuxfoundation.org>