162306a36Sopenharmony_ci.. SPDX-License-Identifier: GPL-2.0 262306a36Sopenharmony_ci 362306a36Sopenharmony_ci=========================== 462306a36Sopenharmony_ciLow Power Idle Table (LPIT) 562306a36Sopenharmony_ci=========================== 662306a36Sopenharmony_ci 762306a36Sopenharmony_ciTo enumerate platform Low Power Idle states, Intel platforms are using 862306a36Sopenharmony_ci“Low Power Idle Table” (LPIT). More details about this table can be 962306a36Sopenharmony_cidownloaded from: 1062306a36Sopenharmony_cihttps://www.uefi.org/sites/default/files/resources/Intel_ACPI_Low_Power_S0_Idle.pdf 1162306a36Sopenharmony_ci 1262306a36Sopenharmony_ciResidencies for each low power state can be read via FFH 1362306a36Sopenharmony_ci(Function fixed hardware) or a memory mapped interface. 1462306a36Sopenharmony_ci 1562306a36Sopenharmony_ciOn platforms supporting S0ix sleep states, there can be two types of 1662306a36Sopenharmony_ciresidencies: 1762306a36Sopenharmony_ci 1862306a36Sopenharmony_ci - CPU PKG C10 (Read via FFH interface) 1962306a36Sopenharmony_ci - Platform Controller Hub (PCH) SLP_S0 (Read via memory mapped interface) 2062306a36Sopenharmony_ci 2162306a36Sopenharmony_ciThe following attributes are added dynamically to the cpuidle 2262306a36Sopenharmony_cisysfs attribute group:: 2362306a36Sopenharmony_ci 2462306a36Sopenharmony_ci /sys/devices/system/cpu/cpuidle/low_power_idle_cpu_residency_us 2562306a36Sopenharmony_ci /sys/devices/system/cpu/cpuidle/low_power_idle_system_residency_us 2662306a36Sopenharmony_ci 2762306a36Sopenharmony_ciThe "low_power_idle_cpu_residency_us" attribute shows time spent 2862306a36Sopenharmony_ciby the CPU package in PKG C10 2962306a36Sopenharmony_ci 3062306a36Sopenharmony_ciThe "low_power_idle_system_residency_us" attribute shows SLP_S0 3162306a36Sopenharmony_ciresidency, or system time spent with the SLP_S0# signal asserted. 3262306a36Sopenharmony_ciThis is the lowest possible system power state, achieved only when CPU is in 3362306a36Sopenharmony_ciPKG C10 and all functional blocks in PCH are in a low power state. 34