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| author | Changbin Du <changbin.du@gmail.com> | 2019-04-25 01:53:04 +0800 |
|---|---|---|
| committer | Rafael J. Wysocki <rafael.j.wysocki@intel.com> | 2019-04-25 23:07:20 +0200 |
| commit | 4887954cac779abe38d3ba6446dec341ccca04ea (patch) | |
| tree | ab9ec6c57324c628188cad0a2911a50fd28ffd43 /Documentation/firmware-guide | |
| parent | 3e57460f007c86476c376a08e31da441cae0b195 (diff) | |
| download | lwn-4887954cac779abe38d3ba6446dec341ccca04ea.tar.gz lwn-4887954cac779abe38d3ba6446dec341ccca04ea.zip | |
Documentation: ACPI: move lpit.txt to firmware-guide/acpi and convert to reST
This converts the plain text documentation to reStructuredText format
and adds it to Sphinx TOC tree.
No essential content change.
Signed-off-by: Changbin Du <changbin.du@gmail.com>
Reviewed-by: Mauro Carvalho Chehab <mchehab+samsung@kernel.org>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Diffstat (limited to 'Documentation/firmware-guide')
| -rw-r--r-- | Documentation/firmware-guide/acpi/index.rst | 1 | ||||
| -rw-r--r-- | Documentation/firmware-guide/acpi/lpit.rst | 33 |
2 files changed, 34 insertions, 0 deletions
diff --git a/Documentation/firmware-guide/acpi/index.rst b/Documentation/firmware-guide/acpi/index.rst index fca854f017d8..0e60f4b7129a 100644 --- a/Documentation/firmware-guide/acpi/index.rst +++ b/Documentation/firmware-guide/acpi/index.rst @@ -22,3 +22,4 @@ ACPI Support gpio-properties i2c-muxes acpi-lid + lpit diff --git a/Documentation/firmware-guide/acpi/lpit.rst b/Documentation/firmware-guide/acpi/lpit.rst new file mode 100644 index 000000000000..aca928fab027 --- /dev/null +++ b/Documentation/firmware-guide/acpi/lpit.rst @@ -0,0 +1,33 @@ +.. 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: +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. |