acpi(4)

NAME

acpi - Advanced Configuration and Power Management support

SYNOPSIS

device acpi
options ACPI_DEBUG

DESCRIPTION

The acpi driver provides support for the Intel/Mi
crosoft/Compaq/Toshiba
ACPI standard. This support includes platform hardware dis
covery (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 transi
tion 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 oc
curs.

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 en
abled.
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 white
out after
resume. Try setting this to 0 if this causes prob
lems for you.
hw.acpi.serialize_methods
Allow override of whether methods execute in paral
lel 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 recur
sive 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 envi
ronment 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. Dis
abling 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 se
lectively disabled in case of problems. To disable a sub-driver, list it
in the kernel environment variable debug.acpi.disabled. Multiple en
tries 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 en
tirely.
children (feature) Attaches standard ACPI sub
drivers and devices
enumerated in the ACPI namespace. Dis
abling this has a
similar effect to disabling ``bus'', except
that the
ACPI namespace will still be scanned.
button (device) Supports ACPI button devices (typ
ically 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 Con
troller inter
face, 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 typi
cally puts a system to sleep.
quirks (feature) Do not honor quirks. Quirks au
tomatically
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 re
sources which ACPI
claims.
thermal (device) Supports system cooling and heat
management.
timer (device) Implements a timecounter using the
ACPI fixed
frequency 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-sepa
rated 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 inter
preter 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 (un
used)
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 im
portant to avoid
massive amounts of debugging output. For example, the fol
lowing configuration is a good way to gather initial information. It en
ables 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 Mi
crosoft 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.

COMPATIBILITY

ACPI is only found and supported on i386/ia32, ia64, and
amd64.

SEE ALSO

kenv(1), acpi_thermal(4), device.hints(5), loader.conf(5),
acpiconf(8),
acpidump(8), config(8), iasl(8)
Compaq Computer Corporation, Intel Corporation, Microsoft
Corporation,
Phoenix Technologies Ltd., and Toshiba Corporation, Advanced Configuration and Power Interface Specification, August 25,
2003,
http://acpi.info/spec.htm.

AUTHORS

The ACPI CA subsystem is developed and maintained by Intel
Architecture
Labs.
The following people made notable contributions to the ACPI
subsystem in
FreeBSD: Michael Smith, Takanori Watanabe <takawa
ta@jp.FreeBSD.org>,
Mitsuru IWASAKI <iwasaki@jp.FreeBSD.org>, Munehiro Matsuda,
Nate Lawson,
the ACPI-jp mailing list at <acpi-jp@jp.FreeBSD.org>, and
many other contributors.
This manual page was written by Michael Smith <msmith@FreeB
SD.org>.

BUGS

If the acpi driver is loaded as a module when it is already
linked as
part of the kernel, odd things may happen.
BSD February 13, 2005
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