Documentation/firmware-guide/acpi/lpit.rst
Source file repositories/reference/linux-study-clean/Documentation/firmware-guide/acpi/lpit.rst
File Facts
- System
- Linux kernel
- Corpus path
Documentation/firmware-guide/acpi/lpit.rst- Extension
.rst- Size
- 1275 bytes
- Lines
- 34
- Domain
- Support Tooling And Documentation
- Bucket
- Documentation
- Inferred role
- Support Tooling And Documentation: documentation
- Status
- atlas-only
Why This File Exists
Repository support layer: documentation, build tooling, samples, user-space helper tools, generated initramfs support, licenses, and validation utilities.
- Repository support layer: documentation, build tooling, samples, user-space helper tools, generated initramfs support, licenses, and validation utilities.
Dependency Surface
- No C-style include directives detected by the generator.
Detected Declarations
- No top-level syscall, struct, function, initcall, or export declaration detected by the generator.
Annotated Snippet
.. 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.Annotation
- Atlas domain: Support Tooling And Documentation / Documentation.
- Implementation status: atlas-only.
Implementation Notes
- This generated page is the file-by-file coverage layer; curated subsystem chapters should link here when they synthesize a multi-file control flow.
- Core OS pages should be promoted from atlas-only to deep-reviewed when they explain data structures, invariants, locking, lifecycle, and C implementation snippets.
- Driver-family pages are intentionally pattern-oriented unless they are part of the selected PCIe/NVMe representative device path.