diff options
Diffstat (limited to 'Documentation/admin-guide/pm')
| -rw-r--r-- | Documentation/admin-guide/pm/amd-pstate.rst | 87 | ||||
| -rw-r--r-- | Documentation/admin-guide/pm/intel-speed-select.rst | 2 |
2 files changed, 78 insertions, 11 deletions
diff --git a/Documentation/admin-guide/pm/amd-pstate.rst b/Documentation/admin-guide/pm/amd-pstate.rst index e1771f2225d5..f8e7050fc762 100644 --- a/Documentation/admin-guide/pm/amd-pstate.rst +++ b/Documentation/admin-guide/pm/amd-pstate.rst @@ -239,8 +239,12 @@ control its functionality at the system level. They are located in the root@hr-test1:/home/ray# ls /sys/devices/system/cpu/cpufreq/policy0/*amd* /sys/devices/system/cpu/cpufreq/policy0/amd_pstate_highest_perf + /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 ``amd_pstate_highest_perf / amd_pstate_max_freq`` @@ -264,14 +268,46 @@ This attribute is read-only. ``amd_pstate_hw_prefcore`` -Whether the platform supports the preferred core feature and it has been -enabled. This attribute is read-only. +Whether the platform supports the preferred core feature and it has +been enabled. This attribute is read-only. This file is only visible +on platforms which support the preferred core feature. ``amd_pstate_prefcore_ranking`` The performance ranking of the core. This number doesn't have any unit, but larger numbers are preferred at the time of reading. This can change at -runtime based on platform conditions. This attribute is read-only. +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`` @@ -280,16 +316,22 @@ A list of all the supported EPP preferences that could be used for These profiles represent different hints that are provided to the low-level firmware about the user's desired energy vs efficiency tradeoff. ``default`` represents the epp value is set by platform -firmware. This attribute is read-only. +firmware. ``custom`` designates that integer values 0-255 may be written +as well. This attribute is read-only. ``energy_performance_preference`` The current energy performance preference can be read from this attribute. and user can change current preference according to energy or performance needs -Please get all support profiles list from -``energy_performance_available_preferences`` attribute, all the profiles are -integer values defined between 0 to 255 when EPP feature is enabled by platform -firmware, if EPP feature is disabled, driver will ignore the written value +Coarse named profiles are available in the attribute +``energy_performance_available_preferences``. +Users can also write individual integer values between 0 to 255. +When dynamic EPP is enabled, writes to energy_performance_preference are blocked +even when EPP feature is enabled by platform firmware. Lower epp values shift the bias +towards improved performance while a higher epp value shifts the bias towards +power-savings. The exact impact can change from one platform to the other. +If a valid integer was last written, then a number will be returned on future reads. +If a valid string was last written then a string will be returned on future reads. This attribute is read-write. ``boost`` @@ -311,6 +353,24 @@ boost or `1` to enable it, for the respective CPU using the sysfs path Other performance and frequency values can be read back from ``/sys/devices/system/cpu/cpuX/acpi_cppc/``, see :ref:`cppc_sysfs`. +Dynamic energy performance profile +================================== +The amd-pstate driver supports dynamically selecting the energy performance +profile based on whether the machine is running on AC or DC power. + +Whether this behavior is enabled by default depends on the kernel +config option `CONFIG_X86_AMD_PSTATE_DYNAMIC_EPP`. This behavior can also be overridden +at runtime by the sysfs file ``/sys/devices/system/cpu/cpufreq/policyX/dynamic_epp``. + +When set to enabled, the driver will select a different energy performance +profile when the machine is running on battery or AC power. The driver will +also register with the platform profile handler to receive notifications of +user desired power state and react to those. +When set to disabled, the driver will not change the energy performance profile +based on the power source and will not react to user desired power state. + +Attempting to manually write to the ``energy_performance_preference`` sysfs +file will fail when ``dynamic_epp`` is enabled. ``amd-pstate`` vs ``acpi-cpufreq`` ====================================== @@ -422,6 +482,13 @@ For systems that support ``amd-pstate`` preferred core, the core rankings will always be advertised by the platform. But OS can choose to ignore that via the kernel parameter ``amd_prefcore=disable``. +``amd_dynamic_epp`` + +When AMD pstate is in auto mode, dynamic EPP will control whether the kernel +autonomously changes the EPP mode. The default is configured by +``CONFIG_X86_AMD_PSTATE_DYNAMIC_EPP`` but can be explicitly enabled with +``amd_dynamic_epp=enable`` or disabled with ``amd_dynamic_epp=disable``. + User Space Interface in ``sysfs`` - General =========================================== @@ -790,13 +857,13 @@ Reference =========== .. [1] AMD64 Architecture Programmer's Manual Volume 2: System Programming, - https://www.amd.com/system/files/TechDocs/24593.pdf + https://docs.amd.com/v/u/en-US/24593_3.44_APM_Vol2 .. [2] Advanced Configuration and Power Interface Specification, https://uefi.org/sites/default/files/resources/ACPI_Spec_6_4_Jan22.pdf .. [3] Processor Programming Reference (PPR) for AMD Family 19h Model 51h, Revision A1 Processors - https://www.amd.com/system/files/TechDocs/56569-A1-PUB.zip + https://docs.amd.com/v/u/en-US/56569-A1-PUB_3.03 .. [4] Linux Kernel Selftests, https://www.kernel.org/doc/html/latest/dev-tools/kselftest.html diff --git a/Documentation/admin-guide/pm/intel-speed-select.rst b/Documentation/admin-guide/pm/intel-speed-select.rst index a2bfb971654f..dec2a25f10bc 100644 --- a/Documentation/admin-guide/pm/intel-speed-select.rst +++ b/Documentation/admin-guide/pm/intel-speed-select.rst @@ -287,7 +287,7 @@ level. Check presence of other Intel(R) SST features --------------------------------------------- -Each of the performance profiles also specifies weather there is support of +Each of the performance profiles also specifies whether there is support of other two Intel(R) SST features (Intel(R) Speed Select Technology - Base Frequency (Intel(R) SST-BF) and Intel(R) Speed Select Technology - Turbo Frequency (Intel SST-TF)). |