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authorRafael J. Wysocki <rafael.j.wysocki@intel.com>2017-11-13 01:41:11 +0100
committerRafael J. Wysocki <rafael.j.wysocki@intel.com>2017-11-13 01:41:11 +0100
commit794c33555f704047e4014d4601b3972cfbfe7e50 (patch)
tree014bcdc36e4d1fbd3083dba8fae43993ec3a7084 /Documentation
parent28da43956b04d2bd854d8db3ab1883a223bee07d (diff)
parentff1656790b3a4caca94505c52fd0250f981ea187 (diff)
downloadlinux-794c33555f704047e4014d4601b3972cfbfe7e50.tar.bz2
Merge branch 'acpi-pm'
* acpi-pm: ACPI / PM: Fix acpi_pm_notifier_lock vs flush_workqueue() deadlock ACPI / LPSS: Consolidate runtime PM and system sleep handling ACPI / PM: Combine device suspend routines ACPI / LPIT: Add Low Power Idle Table (LPIT) support ACPI / PM: Split code validating need for runtime resume in ->prepare() ACPI / PM: Restore acpi_subsys_complete() ACPI / PM: Combine two identical device resume routines ACPI / PM: Remove stale function header
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+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:
+http://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.