Commit 88d2ca6a authored by Gautham R. Shenoy's avatar Gautham R. Shenoy Committed by Mario Limonciello (AMD)
Browse files

Documentation/amd-pstate: Add documentation for amd_pstate_floor_{freq,count} 



Add documentation for the sysfs files
/sys/devices/system/cpu/cpufreq/policy*/amd_pstate_floor_freq
and
/sys/devices/system/cpu/cpufreq/policy*/amd_pstate_floor_count.

Reviewed-by: default avatarMario Limonciello (AMD) <superm1@kernel.org>
Signed-off-by: default avatarGautham R. Shenoy <gautham.shenoy@amd.com>
Signed-off-by: default avatarMario Limonciello (AMD) <superm1@kernel.org>
parent a5bc4c44

Documentation/admin-guide/pm/amd-pstate.rst

+32 −0
Original line number Diff line number Diff line
@@ -242,6 +242,8 @@ control its functionality at the system level. They are located in the 
 /sys/devices/system/cpu/cpufreq/policy0/amd_pstate_hw_prefcore

 /sys/devices/system/cpu/cpufreq/policy0/amd_pstate_lowest_nonlinear_freq

 /sys/devices/system/cpu/cpufreq/policy0/amd_pstate_max_freq

 /sys/devices/system/cpu/cpufreq/policy0/amd_pstate_floor_freq

 /sys/devices/system/cpu/cpufreq/policy0/amd_pstate_floor_count

 /sys/devices/system/cpu/cpufreq/policy0/amd_pstate_prefcore_ranking
@@ -277,6 +279,36 @@ larger numbers are preferred at the time of reading. This can change at 
runtime based on platform conditions. This attribute is read-only. This file

is only visible on platforms which support the preferred core feature.



``amd_pstate_floor_freq``



The floor frequency associated with each CPU. Userspace can write any

value between ``cpuinfo_min_freq`` and ``scaling_max_freq`` into this

file. When the system is under power or thermal constraints, the

platform firmware will attempt to throttle the CPU frequency to the

value specified in ``amd_pstate_floor_freq`` before throttling it

further. This allows userspace to specify different floor frequencies

to different CPUs. For optimal results, threads of the same core

should have the same floor frequency value. This file is only visible

on platforms that support the CPPC Performance Priority feature.





``amd_pstate_floor_count``



The number of distinct Floor Performance levels supported by the

platform. For example, if this value is 2, then the number of unique

values obtained from the command ``cat

/sys/devices/system/cpu/cpufreq/policy*/amd_pstate_floor_freq |

sort -n | uniq`` should be at most this number for the behavior

described in ``amd_pstate_floor_freq`` to take effect. A zero value

implies that the platform supports unlimited floor performance levels.

This file is only visible on platforms that support the CPPC

Performance Priority feature.



**Note**: When ``amd_pstate_floor_count`` is non-zero, the frequency to

which the CPU is throttled under power or thermal constraints is

undefined when the number of unique values of ``amd_pstate_floor_freq``

across all CPUs in the system exceeds ``amd_pstate_floor_count``.



``energy_performance_available_preferences``



A list of all the supported EPP preferences that could be used for