About Kernel Documentation Linux Kernel Contact Linux Resources Linux Blog

Documentation / acpi / lpit.txt


Based on kernel version 4.16.1. Page generated on 2018-04-09 11:52 EST.

1	To enumerate platform Low Power Idle states, Intel platforms are using
2	“Low Power Idle Table” (LPIT). More details about this table can be
3	downloaded from:
4	http://www.uefi.org/sites/default/files/resources/Intel_ACPI_Low_Power_S0_Idle.pdf
5	
6	Residencies for each low power state can be read via FFH
7	(Function fixed hardware) or a memory mapped interface.
8	
9	On platforms supporting S0ix sleep states, there can be two types of
10	residencies:
11	- CPU PKG C10 (Read via FFH interface)
12	- Platform Controller Hub (PCH) SLP_S0 (Read via memory mapped interface)
13	
14	The following attributes are added dynamically to the cpuidle
15	sysfs attribute group:
16		/sys/devices/system/cpu/cpuidle/low_power_idle_cpu_residency_us
17		/sys/devices/system/cpu/cpuidle/low_power_idle_system_residency_us
18	
19	The "low_power_idle_cpu_residency_us" attribute shows time spent
20	by the CPU package in PKG C10
21	
22	The "low_power_idle_system_residency_us" attribute shows SLP_S0
23	residency, or system time spent with the SLP_S0# signal asserted.
24	This is the lowest possible system power state, achieved only when CPU is in
25	PKG C10 and all functional blocks in PCH are in a low power state.
Hide Line Numbers


About Kernel Documentation Linux Kernel Contact Linux Resources Linux Blog