acpi (4)

Name

acpi - Advanced Configuration and Power Management support

Synopsis

device acpi

options ACPI_DEBUG

The acpi driver provides support for the Intel/Microsoft/Compaq/Toshiba
ACPI standard. This support includes platform hardware discovery (superseding
the PnP and PCI BIOS), as well as power management (superseding
APM) and other features. ACPI core support is provided by the ACPI CA
reference implementation from Intel.

Note that the acpi driver is automatically loaded by the loader(8) , and
should only be compiled into the kernel on platforms where

ACPI is mandatory.

Sysctl Variables

The acpi driver is intended to provide power management without user
intervention. Thus, some of these sysctls are controlled automatically
by the power_profile rc(8) script, which can be configured via
rc.conf(5) . If values are specified manually, they may be overridden.

hw.acpi.cpu.cx_usage
Debugging information listing the percent of total usage for each
sleep state. The values are reset when hw.acpi.cpu.cx_lowest is
modified.

hw.acpi.cpu.cx_lowest
Lowest Cx state to use for idling the CPU. A scheduling algorithm
will select states between C1 and this setting as system
load dictates. To enable ACPI CPU idling control, machdep.cpu_idle_hlt must be set to 1.

hw.acpi.cpu.cx_supported
List of supported CPU idle states and their transition latency in
microseconds. Each state has a type (e.g., C2). C1 is equivalent
to the ia32 HLT instruction, C2 provides a deeper sleep with
the same semantics, and C3 provides the deepest sleep but additionally
requires bus mastering to be disabled.

States greater

than C3 provide even more power savings with the same semantics
as the C3 state. Deeper sleeps provide more power savings but
increased transition latency when an interrupt occurs.

Loader Tunables

Tunables can be set at the loader(8) prompt before booting the kernel or
stored in /boot/loader.conf.

acpi_dsdt_load
Enables loading of a custom ACPI DSDT.

acpi_dsdt_name
Name of the DSDT table to load, if loading is enabled.

debug.acpi.disabled
Selectively disables portions of ACPI for debugging purposes.

debug.acpi.max_threads
Specify the number of task threads that are started on boot.
Limiting this to 1 may help work around various

BIOSes that cannot

handle parallel requests. The default value is 3.

debug.acpi.quirks
Override any automatic quirks completely.

hint.acpi.0.disabled
Set this to 1 to disable all of ACPI. If ACPI has been disabled
on your system due to a blacklist entry for your

BIOS, you can

set this to 0 to re-enable ACPI for testing.

hw.acpi.ec.poll_timeout
Delay in milliseconds to wait for the EC to respond.

Try

increasing this number if you get the error “AE_NO_HARDWARE_RESPONSE".

hw.acpi.host_mem_start
Override the assumed memory starting address for PCI host
bridges.

hw.acpi.pci.link.%d.%d.%d.irq
Override the interrupt to use.

hw.acpi.reset_video
Enables calling the VESA reset BIOS vector on the resume path.
Some graphic chips have problems such as LCD whiteout after
resume. Try setting this to 0 if this causes problems for you.

hw.acpi.serialize_methods
Allow override of whether methods execute in parallel or not.
Enable this for serial behavior, which fixes “AE_AL-

Ready_exists"

errors for AML that really cannot handle parallel method execution.
It is off by default since this breaks recursive methods
and some IBMs use such code.

hw.acpi.verbose
Turn on verbose debugging information about what

ACPI is doing.

Disabling Acpi

Since ACPI support on different platforms varies greatly, there are many
debugging and tuning options available.

For machines known not to work with acpi enabled, there is a

BIOS blacklist.

Currently, the blacklist only controls whether acpi should be disabled
or not. In the future, it will have more granularity to control
features (the infrastructure for that is already there).

To enable acpi (for debugging purposes, etc.) on machines that are on the
blacklist, set the kernel environment variable hint.acpi.0.disabled to 0.
Before trying this, consider updating your BIOS to a more recent version
that may be compatible with ACPI.

To disable the acpi driver completely, set the kernel environment variable
hint.acpi.0.disabled to 1.

Some i386 machines totally fail to operate with some or all of ACPI disabled.
Other i386 machines fail with ACPI enabled. Disabling all or
part of ACPI on non-i386 platforms (i.e., platforms where

ACPI support is

mandatory) may result in a non-functional system.

The acpi driver comprises a set of drivers, which may be selectively disabled
in case of problems. To disable a sub-driver, list it in the kernel
environment variable debug.acpi.disabled. Multiple entries can be
listed, separated by a space.

ACPI sub-devices and features that can be disabled:

all: Disable all ACPI features and devices.
acad: (device) Supports AC adapter.
bus: (feature) Probes and attaches subdevices.

Disabling

will avoid scanning the ACPI namespace entirely.

children: (feature) Attaches standard ACPI subdrivers and devices enumerated in the ACPI namespace. Disabling this has a similar effect to disabling ‘‘bus’’, except that the ACPI namespace will still be scanned.
button: (device) Supports ACPI button devices (typically power and sleep buttons).
cmbat: (device) Control-method batteries device.
cpu: (device) Supports CPU power-saving and speed-setting functions.
ec: (device) Supports the ACPI Embedded Controller interface, used to communicate with embedded platform controllers.
isa: (device) Supports an ISA bus bridge defined in the ACPI namespace, typically as a child of a PCI bus.
lid: (device) Supports an ACPI laptop lid switch, which typically puts a system to sleep.
quirks: (feature) Do not honor quirks. Quirks automatically disable ACPI functionality based on the XS-

DT table’s OEM

vendor name and revision date.

pci: (device) Supports Host to PCI bridges.
pci_link: (feature) Performs PCI interrupt routing.
sysresource: (device) Pseudo-devices containing resources which ACPI claims.
thermal: (device) Supports system cooling and heat management.
timer: (device) Implements a timecounter using the

ACPI fixedfrequency

timer.

video: (device) Supports acpi_video(4) which may conflict with agp(4) device.

It is also possible to avoid portions of the ACPI namespace which may be
causing problems, by listing the full path of the root of the region to
be avoided in the kernel environment variable debug.acpi.avoid. The
object and all of its children will be ignored during the bus/children
scan of the namespace. The ACPI CA code will still know about the
avoided region.

Debugging Output

To enable debugging output, acpi must be compiled with options
ACPI_DEBUG. Debugging output is separated between layers and levels,
where a layer is a component of the ACPI subsystem, and a level is a particular
kind of debugging output.

Both layers and levels are specified as a whitespace-separated list of
tokens, with layers listed in debug.acpi.layer and levels in debug.acpi.level.

The first set of layers is for ACPI-CA components, and the second is for
FreeBSD drivers. The ACPI-CA layer descriptions include the prefix for
the files they refer to. The supported layers are:

ACPI_UTILITIES: Utility ("ut") functions
ACPI_HARDWARE: Hardware access ("hw")
ACPI_EVENTS: Event and GPE ("ev")
ACPI_TABLES: Table access ("tb")
ACPI_NAMESPACE: Namespace evaluation ("ns")
ACPI_PARSER: AML parser ("ps")
ACPI_DISPATCHER: Internal representation of interpreter state ("ds")
ACPI_EXECUTER: Execute AML methods ("ex")
ACPI_RESOURCES: Resource parsing ("rs")
ACPI_CA_DEBUGGER: Debugger implementation ("db", “dm")
ACPI_OS_SERVICES: Usermode support routines ("os")
ACPI_CA_DISASSEMBLER: Disassembler implementation (unused)
ACPI_ALL_COMPONENTS: All the above ACPI-CA components
ACPI_AC_ADAPTER: AC adapter driver
ACPI_BATTERY: Control-method battery driver
ACPI_BUS: ACPI, ISA, and PCI bus drivers
ACPI_BUTTON: Power and sleep button driver
ACPI_EC: Embedded controller driver
ACPI_FAN: Fan driver
ACPI_OEM: Platform-specific driver for hotkeys, LED, etc.
ACPI_POWER: Power resource driver
ACPI_PROCESSOR: CPU driver
ACPI_THERMAL: Thermal zone driver
ACPI_TIMER: Timer driver
ACPI_ALL_DRIVERS: All the above FreeBSD ACPI drivers

The supported levels are:

ACPI_LV_ERROR: Fatal error conditions
ACPI_LV_WARN: Warnings and potential problems
ACPI_LV_INIT: Initialization progress
ACPI_LV_DEBUG_OBJECT: Stores to objects
ACPI_LV_INFO: General information and progress
ACPI_LV_ALL_EXCEPTIONS: All the previous levels ACPI_LV_INIT_NAMES ACPI_LV_PARSE ACPI_LV_LOAD ACPI_LV_DISPATCH ACPI_LV_EXEC ACPI_LV_NAMES ACPI_LV_OPREGION ACPI_LV_BFIELD ACPI_LV_TABLES ACPI_LV_VALUES ACPI_LV_OBJECTS ACPI_LV_RESOURCES ACPI_LV_USER_REQUESTS ACPI_LV_PACKAGE
ACPI_LV_VERBOSITY1: All the previous levels ACPI_LV_ALLOCATIONS ACPI_LV_FUNCTIONS ACPI_LV_OPTIMIZATIONS ACPI_LV_VERBOSITY2 ACPI_LV_ALL ACPI_LV_MUTEX ACPI_LV_THREADS ACPI_LV_IO ACPI_LV_INTERRUPTS
ACPI_LV_VERBOSITY3: All the previous levels ACPI_LV_AML_DISASSEMBLE ACPI_LV_VERBOSE_INFO ACPI_LV_FULL_TABLES ACPI_LV_EVENTS
ACPI_LV_VERBOSE: All levels after “ACPI_LV_VER-

Bosity3"

Selection of the appropriate layer and level values is important to avoid
massive amounts of debugging output. For example, the following configuration
is a good way to gather initial information. It enables debug
output for both ACPI-CA and the acpi driver, printing basic information
about errors, warnings, and progress.

debug.acpi.layer="ACPI_ALL_COMPONENTS

Acpi_all_drivers"

debug.acpi.level="ACPI_LV_ALL_EXCEPTIONS"

Debugging output by the ACPI CA subsystem is prefixed with the module
name in lowercase, followed by a source line number. Output from the
FreeBSD-local code follows the same format, but the module name is uppercased.

Overriding Your Bios Bytecode

ACPI interprets bytecode named AML (ACPI Machine Language) provided by
the BIOS vendor as a memory image at boot time. Sometimes, the AML code
contains a bug that does not appear when parsed by the Microsoft implementation.
FreeBSD provides a way to override it with your own AML code
to work around or debug such problems. Note that all AML in your DSDT
and any SSDT tables is overridden.

In order to load your AML code, you must edit /boot/loader.conf and
include the following lines.

acpi_dsdt_load="YES"
acpi_dsdt_name="/boot/acpi_dsdt.aml” # You may change this name.

In order to prepare your AML code, you will need the acpidump(8) and
iasl(8) utilities and some ACPI knowledge.