Greg Kroah-Hartman
598cf27219
Link: https://lore.kernel.org/r/20260217200002.683975158@linuxfoundation.org Tested-by: Florian Fainelli <florian.fainelli@broadcom.com> Tested-by: Takeshi Ogasawara <takeshi.ogasawara@futuring-girl.com> Tested-by: Peter Schneider <pschneider1968@googlemail.com> Tested-by: Jon Hunter <jonathanh@nvidia.com> Tested-by: Salvatore Bonaccorso <carnil@debian.org> Tested-by: Brett A C Sheffield <bacs@librecast.net> Tested-by: Mark Brown <broonie@kernel.org> Tested-by: Luna Jernberg <droidbittin@gmail.com> Tested-by: Ronald Warsow <rwarsow@gmx.de> Tested-by: Justin M. Forbes <jforbes@fedoraproject.org> Tested-by: Ron Economos <re@w6rz.net> Tested-by: Miguel Ojeda <ojeda@kernel.org> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
34 lines
1.2 KiB
ReStructuredText
34 lines
1.2 KiB
ReStructuredText
.. SPDX-License-Identifier: GPL-2.0
|
|
|
|
===========================
|
|
Low Power Idle Table (LPIT)
|
|
===========================
|
|
|
|
To enumerate platform Low Power Idle states, Intel platforms are using
|
|
“Low Power Idle Table” (LPIT). More details about this table can be
|
|
downloaded from:
|
|
https://www.uefi.org/sites/default/files/resources/Intel_ACPI_Low_Power_S0_Idle.pdf
|
|
|
|
Residencies for each low power state can be read via FFH
|
|
(Function fixed hardware) or a memory mapped interface.
|
|
|
|
On platforms supporting S0ix sleep states, there can be two types of
|
|
residencies:
|
|
|
|
- CPU PKG C10 (Read via FFH interface)
|
|
- Platform Controller Hub (PCH) SLP_S0 (Read via memory mapped interface)
|
|
|
|
The following attributes are added dynamically to the cpuidle
|
|
sysfs attribute group::
|
|
|
|
/sys/devices/system/cpu/cpuidle/low_power_idle_cpu_residency_us
|
|
/sys/devices/system/cpu/cpuidle/low_power_idle_system_residency_us
|
|
|
|
The "low_power_idle_cpu_residency_us" attribute shows time spent
|
|
by the CPU package in PKG C10
|
|
|
|
The "low_power_idle_system_residency_us" attribute shows SLP_S0
|
|
residency, or system time spent with the SLP_S0# signal asserted.
|
|
This is the lowest possible system power state, achieved only when CPU is in
|
|
PKG C10 and all functional blocks in PCH are in a low power state.
|