34 lines · plain
1.. SPDX-License-Identifier: GPL-2.02 3===========================4Low Power Idle Table (LPIT)5===========================6 7To enumerate platform Low Power Idle states, Intel platforms are using8“Low Power Idle Table” (LPIT). More details about this table can be9downloaded from:10https://www.uefi.org/sites/default/files/resources/Intel_ACPI_Low_Power_S0_Idle.pdf11 12Residencies for each low power state can be read via FFH13(Function fixed hardware) or a memory mapped interface.14 15On platforms supporting S0ix sleep states, there can be two types of16residencies:17 18 - CPU PKG C10 (Read via FFH interface)19 - Platform Controller Hub (PCH) SLP_S0 (Read via memory mapped interface)20 21The following attributes are added dynamically to the cpuidle22sysfs attribute group::23 24 /sys/devices/system/cpu/cpuidle/low_power_idle_cpu_residency_us25 /sys/devices/system/cpu/cpuidle/low_power_idle_system_residency_us26 27The "low_power_idle_cpu_residency_us" attribute shows time spent28by the CPU package in PKG C1029 30The "low_power_idle_system_residency_us" attribute shows SLP_S031residency, or system time spent with the SLP_S0# signal asserted.32This is the lowest possible system power state, achieved only when CPU is in33PKG C10 and all functional blocks in PCH are in a low power state.34