.\"
.\" Copyright (c) 2001 Michael Smith
.\" All rights reserved.
.\"
.\" Redistribution and use in source and binary forms, with or without
.\" modification, are permitted provided that the following conditions
.\" are met:
.\" 1. Redistributions of source code must retain the above copyright
.\"    notice, this list of conditions and the following disclaimer.
.\" 2. Redistributions in binary form must reproduce the above copyright
.\"    notice, this list of conditions and the following disclaimer in the
.\"    documentation and/or other materials provided with the distribution.
.\"
.\" THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
.\" ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
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.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
.\" SUCH DAMAGE.
.\"
.\" $FreeBSD: src/share/man/man4/acpi.4,v 1.61.8.1 2009/04/15 03:14:26 kensmith Exp $
.\"
.Dd July 25, 2024
.Dt ACPI 4
.Os
.Sh NAME
.Nm acpi
.Nd Advanced Configuration and Power Management support
.Sh SYNOPSIS
.Cd "device acpi"
.Pp
.Cd "options ACPI_DEBUG"
.Cd "options DDB"
.Sh DESCRIPTION
The
.Nm
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 ACPICA reference implementation
from Intel.
.Pp
The
.Nm
driver is usually compiled into the kernel, and it is automatically loaded
by the
.Xr loader 8
if it is not in the kernel configuration file.
The loader menu provides a menu item to boot without ACPI.
See also
.Sx DISABLING ACPI
below.
.Sh SYSCTL VARIABLES
The
.Nm
driver is intended to provide power management without user intervention.
If the default settings are not optimal, the following sysctls can be
used to modify or monitor
.Nm
behavior.
.Bl -tag -width indent
.It Va debug.acpi.enable_debug_objects
Enable dumping Debug objects without
.Cd "options ACPI_DEBUG" .
Default is 0, ignore Debug objects.
.It Va hw.acpi.acline
AC line state (1 means online, 0 means on battery power).
.It Va hw.acpi.cpu.cx_usage
Debugging information listing the percent of total usage for each sleep state.
The values are reset when
.Va hw.acpi.cpu.cx_lowest
is modified.
.It Va hw.acpi.cpu.cx_lowest
Lowest Cx state to use for idling the CPU.
A scheduling algorithm will select states between
.Li C1
and this setting
as system load dictates.
To enable ACPI CPU idling control,
.Va machdep.cpu_idle_hlt
must be set to 2 (the default value).
.It Va hw.acpi.cpu.cx_supported
List of supported CPU idle states and their transition latency
in microseconds.
Each state has a type (e.g.,
.Li C2 ) .
.Li C1
is equivalent to the ia32
.Li HLT
instruction,
.Li C2
provides a deeper
sleep with the same semantics, and
.Li C3
provides the deepest sleep
but additionally requires bus mastering to be disabled.
States greater than
.Li C3
provide even more power savings with the same
semantics as the
.Li C3
state.
Deeper sleeps provide more power savings but increased transition
latency when an interrupt occurs.
.It Va hw.acpi.disable_on_reboot
Disable ACPI during the reboot process.
Most systems reboot fine with ACPI still enabled, but some require
exiting to legacy mode first.
Default is 0, leave ACPI enabled.
.It Va hw.acpi.handle_reboot
Use the ACPI Reset Register capability to reboot the system.
Default is 0, use legacy reboot support.
Some newer systems require use of this register, while some only work
with legacy rebooting support.
.It Va hw.acpi.lid_switch_state
Suspend state
.Pq Li S1 Ns \[en] Ns Li S5
to enter when the lid switch (i.e., a notebook screen) is closed.
Default is
.Dq Li NONE
(do nothing).
.It Va hw.acpi.power_button_state
Suspend state
.Pq Li S1 Ns \[en] Ns Li S5
to enter when the power button is pressed.
Default is
.Li S5
(power-off nicely).
.It Va hw.acpi.reset_video
Reset the video adapter from real mode during the resume path.
Some systems need this help, others have display problems if it is enabled.
Default is 0 (disabled).
.It Va hw.acpi.s4bios
Indicate whether the system supports
.Li S4BIOS .
This means that the BIOS can handle all the functions of suspending the
system to disk.
Otherwise, the OS is responsible for suspending to disk
.Pq Li S4OS .
Most current systems do not support
.Li S4BIOS .
.It Va hw.acpi.sleep_button_state
Suspend state
.Pq Li S1 Ns \[en] Ns Li S5
to enter when the sleep button is pressed.
This is usually a special function button on the keyboard.
Default is
.Li S3
(suspend-to-RAM).
.It Va hw.acpi.sleep_delay
Wait this number of seconds between preparing the system to suspend and
actually entering the suspend state.
Default is 1 second.
.It Va hw.acpi.supported_sleep_state
Suspend states
.Pq Li S1 Ns \[en] Ns Li S5
supported by the BIOS.
.Bl -tag -width indent
.It Li S1
Quick suspend to RAM.
The CPU enters a lower power state, but most peripherals are left running.
.It Li S2
Lower power state than
.Li S1 ,
but with the same basic characteristics.
Not supported by many systems.
.It Li S3
Suspend to RAM.
Most devices are powered off, and the system stops running except for
memory refresh.
.It Li S4
Suspend to disk.
All devices are powered off, and the system stops running.
When resuming, the system starts as if from a cold power on.
Not yet supported by
.Fx
unless
.Li S4BIOS
is available.
.It Li S5
System shuts down cleanly and powers off.
.El
.It Va hw.acpi.verbose
Enable verbose printing from the various ACPI subsystems.
.El
.Sh LOADER TUNABLES
Tunables can be set at the
.Xr loader 8
prompt before booting the kernel or stored in
.Pa /boot/loader.conf .
Many of these tunables also have a matching
.Xr sysctl 8
entry for access after boot.
.Bl -tag -width indent
.It Va acpi_dsdt_load
Enables loading of a custom ACPI DSDT.
.It Va acpi_dsdt_name
Name of the DSDT table to load, if loading is enabled.
It is relative to
.Pa /boot/kernel .
.It Va debug.acpi.allow_method_calls
If set, the
.Xr acpicall 8
utility can be used to directly call ACPI methods for debugging and
tweaking purposes.
.It Va debug.acpi.disabled
Selectively disables portions of ACPI that are enabled by default, for
debugging purposes.
.It Va debug.acpi.enabled
Selectively enables portions of ACPI that are disabled by default, for
debugging purposes.
.It Va debug.acpi.facs_addr32
Favor 32-bit FACS table addresses over the 64-bit addresses.
.It Va debug.acpi.fadt_addr32
Favor 32-bit FADT register addresses over the 64-bit addresses.
.It Va debug.acpi.ignore_xsdt
Ignore the XSDT, forcing the use of the RSDT.
.It Va debug.acpi.interpreter_slack
Enable less strict ACPI implementations.
Default is 1, ignore common BIOS mistakes.
.It Va 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.
.It Va debug.acpi.quirks
Override any automatic quirks completely.
.It Va debug.acpi.resume_beep
Beep the PC speaker on resume.
This can help diagnose suspend/resume problems.
Default is 0 (disabled).
.It Va 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.
.It Va hw.acpi.ec.poll_timeout
Delay in milliseconds to wait for the EC to respond.
Try increasing this number if you get the error
.Qq Li AE_NO_HARDWARE_RESPONSE .
.It Va hw.acpi.host_mem_start
Override the assumed memory starting address for PCI host bridges.
.It Va hw.acpi.install_interface , hw.acpi.remove_interface
Install or remove OS interface(s) to control the return value of the
.Ql _OSI
query method.
When an OS interface is specified in
.Va hw.acpi.install_interface ,
the
.Li _OSI
query for the interface returns it is
.Em supported .
Conversely, when an OS interface is specified in
.Va hw.acpi.remove_interface ,
the
.Li _OSI
query returns it is
.Em not supported .
Multiple interfaces can be specified in a comma-separated list and
any leading white spaces will be ignored.
For example,
.Qq Li FreeBSD, Linux
is a valid list of two interfaces
.Qq Li FreeBSD
and
.Qq Li Linux .
.It Va hw.acpi.override_isa_irq_polarity (x86)
Forces active-lo polarity for edge-triggered ISA interrupts.
Some older systems incorrectly specify active-lo polarity for ISA
interrupts and this override fixes those systems.
This override is enabled by default on systems with Intel CPUs,
but can be enabled or disabled by setting the tunable explicitly.
.It Va hw.acpi.reset_video
Enables calling the VESA reset BIOS vector on the resume path.
This can fix some graphics cards that have problems such as LCD white-out
after resume.
Default is 0 (disabled).
.It Va hw.acpi.auto_serialize_methods
Auto-serialization of control methods to proactively prevent problems with
ill-behaved reentrant control methods that create named ACPI objects.
Default is 1 (enabled).
.It Va hw.acpi.verbose
Turn on verbose debugging information about what ACPI is doing.
.It Va hw.pci.link.%s.%d.irq
Override the interrupt to use for this link and index.
This capability should be used carefully, and only if a device is not
working with
.Nm
enabled.
.Qq %s
is the name of the link (e.g., LNKA).
.Qq %d
is the resource index when the link supports multiple IRQs.
Most PCI links only have one IRQ resource, so the below form should be used.
.It Va hw.pci.link.%s.irq
Override the interrupt to use.
This capability should be used carefully, and only if a device is not
working with
.Nm
enabled.
.Qq %s
is the name of the link (e.g., LNKA).
.El
.Sh DISABLING ACPI
Since ACPI support on different platforms varies greatly, there are many
debugging and tuning options available.
.Pp
For machines known not to work with
.Nm
enabled, there is a BIOS blacklist.
Currently, the blacklist only controls whether
.Nm
should be disabled or not.
In the future, it will have more granularity to control features (the
infrastructure for that is already there).
.Pp
To enable
.Nm
(for debugging purposes, etc.) on machines that are on the blacklist, set the
kernel environment variable
.Va hint.acpi.0.disabled
to 0.
Before trying this, consider updating your BIOS to a more recent version that
may be compatible with ACPI.
.Pp
To disable the
.Nm
driver completely, set the kernel environment variable
.Va hint.acpi.0.disabled
to 1.
.Pp
Disabling all or part of ACPI may result in a non-functional system.
.Pp
The
.Nm
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
.Va debug.acpi.disabled .
Multiple entries can be listed, separated by a space.
.Pp
ACPI sub-devices and features that can be disabled:
.Bl -tag -width ".Li sysresource"
.It Li all
Disable all ACPI features and devices.
.It Li acad
.Pq Vt device
Supports AC adapter.
.It Li bus
.Pq Vt feature
Probes and attaches subdevices.
Disabling will avoid scanning the ACPI namespace entirely.
.It Li children
.Pq Vt feature
Attaches standard ACPI sub-drivers and devices enumerated in the
ACPI namespace.
Disabling this has a similar effect to disabling
.Dq Li bus ,
except that the
ACPI namespace will still be scanned.
.It Li button
.Pq Vt device
Supports ACPI button devices (typically power and sleep buttons).
.It Li cmbat
.Pq Vt device
Control-method batteries device.
.It Li cpu
.Pq Vt device
Supports CPU power-saving and speed-setting functions.
.It Li cpu_cst
.Pq Vt device
Supports CPU power-saving.
Disabling
.Dq Li cpu
will also disable this device.
.It Li cpu_pst
.Pq Vt device
Supports CPU speed-setting.
Disabling
.Dq Li cpu
will also disable this device.
.It Li dock
.Pq Vt device
Docking station device.
.It Li ec
.Pq Vt device
Supports the ACPI Embedded Controller interface, used to communicate
with embedded platform controllers.
.It Li hpet
.Pq Vt feature
Supports the High Precision Event Timer.
.It Li isa
.Pq Vt device
Supports an ISA bus bridge defined in the ACPI namespace,
typically as a child of a PCI bus.
.It Li lid
.Pq Vt device
Supports an ACPI laptop lid switch, which typically puts a
system to sleep.
.It Li quirks
.Pq Vt feature
Do not honor quirks.
Quirks automatically disable ACPI functionality based on the XSDT table's
OEM vendor name and revision date.
.It Li pci
.Pq Vt device
Supports Host to PCI bridges.
.It Li pci_link
.Pq Vt feature
Performs PCI interrupt routing.
.It Li sysresource
.Pq Vt device
Pseudo-devices containing resources which ACPI claims.
.It Li thermal
.Pq Vt device
Supports system cooling and heat management.
.It Li timer
.Pq Vt device
Implements a timecounter using the ACPI fixed-frequency timer.
.It Li video
.Pq Vt device
Supports
.Xr acpi_video 4
which may conflict with
.Xr agp 4
device.
.El
.Pp
.\"The
.\".Nm
.\"driver comprises a set of drivers,
.\"which may be selectively enabled in case of testing.
.\"To enable a sub-driver,
.\"list it in the kernel environment variable
.\".Va debug.acpi.enabled .
.\"Multiple entries can be listed,
.\"separated by a space.
.\".Pp
.\"ACPI sub-devices and features that can be enabled:
.\".Bl -tag -width ".Li sysresource"
.\"[...]
.\".El
.\".Pp
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
.Va debug.acpi.avoid .
The object and all of its children will be ignored during the
bus/children scan of the namespace.
The ACPICA code will still know about the avoided region.
.Sh DEBUGGING OUTPUT
To enable debugging output,
.Nm
must be compiled with
.Cd "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.
.Pp
Both layers and levels are specified as a whitespace-separated list of
tokens, with layers listed in
.Va debug.acpi.layer
and levels in
.Va debug.acpi.level .
.Pp
The first set of layers is for ACPICA components, and the second is for
.Dx
drivers.
The ACPICA layer descriptions include the prefix for the files they
refer to.
The supported layers are:
.Pp
.Bl -tag -compact -width ".Li ACPI_CA_DISASSEMBLER"
.It Li ACPI_UTILITIES
Utility ("ut") functions
.It Li ACPI_HARDWARE
Hardware access ("hw")
.It Li ACPI_EVENTS
Event and GPE ("ev")
.It Li ACPI_TABLES
Table access ("tb")
.It Li ACPI_NAMESPACE
Namespace evaluation ("ns")
.It Li ACPI_PARSER
AML parser ("ps")
.It Li ACPI_DISPATCHER
Internal representation of interpreter state ("ds")
.It Li ACPI_EXECUTER
Execute AML methods ("ex")
.It Li ACPI_RESOURCES
Resource parsing ("rs")
.It Li ACPI_CA_DEBUGGER
Debugger implementation ("db", "dm")
.It Li ACPI_OS_SERVICES
Usermode support routines ("os")
.It Li ACPI_CA_DISASSEMBLER
Disassembler implementation (unused)
.It Li ACPI_ALL_COMPONENTS
All the above ACPICA components
.It Li ACPI_AC_ADAPTER
AC adapter driver
.It Li ACPI_BATTERY
Control-method battery driver
.It Li ACPI_BUS
ACPI, ISA, and PCI bus drivers
.It Li ACPI_BUTTON
Power and sleep button driver
.It Li ACPI_EC
Embedded controller driver
.It Li ACPI_FAN
Fan driver
.It Li ACPI_OEM
Platform-specific driver for hotkeys, LED, etc.
.It Li ACPI_POWERRES
Power resource driver
.It Li ACPI_PROCESSOR
CPU driver
.It Li ACPI_THERMAL
Thermal zone driver
.It Li ACPI_TIMER
Timer driver
.It Li ACPI_ALL_DRIVERS
All the above
.Dx
ACPI drivers
.El
.Pp
The supported levels are:
.Pp
.Bl -tag -compact -width ".Li ACPI_LV_AML_DISASSEMBLE"
.It Li ACPI_LV_INIT
Initialization progress
.It Li ACPI_LV_DEBUG_OBJECT
Stores to objects
.It Li ACPI_LV_INFO
General information and progress
.It Li ACPI_LV_REPAIR
Repair a common problem with predefined methods
.It Li ACPI_LV_ALL_EXCEPTIONS
All the previous levels
.It Li ACPI_LV_PARSE
.It Li ACPI_LV_DISPATCH
.It Li ACPI_LV_EXEC
.It Li ACPI_LV_NAMES
.It Li ACPI_LV_OPREGION
.It Li ACPI_LV_BFIELD
.It Li ACPI_LV_TABLES
.It Li ACPI_LV_VALUES
.It Li ACPI_LV_OBJECTS
.It Li ACPI_LV_RESOURCES
.It Li ACPI_LV_USER_REQUESTS
.It Li ACPI_LV_PACKAGE
.It Li ACPI_LV_EVALUATION
.It Li ACPI_LV_VERBOSITY1
All the previous levels
.It Li ACPI_LV_ALLOCATIONS
.It Li ACPI_LV_FUNCTIONS
.It Li ACPI_LV_OPTIMIZATIONS
.It Li ACPI_LV_VERBOSITY2
All the previous levels
.It Li ACPI_LV_ALL
Alias for
.Qq Li ACPI_LV_VERBOSITY2
.It Li ACPI_LV_MUTEX
.It Li ACPI_LV_THREADS
.It Li ACPI_LV_IO
.It Li ACPI_LV_INTERRUPTS
.It Li ACPI_LV_VERBOSITY3
All the previous levels
.It Li ACPI_LV_AML_DISASSEMBLE
.It Li ACPI_LV_VERBOSE_INFO
.It Li ACPI_LV_FULL_TABLES
.It Li ACPI_LV_EVENTS
.It Li ACPI_LV_VERBOSE
All levels after
.Qq Li ACPI_LV_VERBOSITY3
.It Li ACPI_LV_INIT_NAMES
Needs to be specified separately
.It Li ACPI_LV_LOAD
Needs to be specified separately
.El
.Pp
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 ACPICA and the
.Nm
driver, printing basic information about errors, warnings, and progress.
.Bd -literal -offset indent
debug.acpi.layer="ACPI_ALL_COMPONENTS ACPI_ALL_DRIVERS"
debug.acpi.level="ACPI_LV_ALL_EXCEPTIONS"
.Ed
.Pp
Debugging output by the ACPICA subsystem is prefixed with the
module name in lowercase, followed by a source line number.
Output from the
.Dx Ns -local
code follows the same format, but
the module name is uppercased.
.Sh 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.
.Dx
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.
.Pp
In order to load your AML code, copy it to
.Pa /boot/kernel/acpi_dsdt.aml
and add the following line to
.Pa /boot/loader.conf .
.Bd -literal -offset indent
acpi_dsdt_load="YES"
.Ed
.Pp
In order to prepare your AML code, you will need the
.Xr acpidump 8
and
.Xr iasl 8
utilities and some ACPI knowledge.
.Sh SEE ALSO
.Xr kenv 1 ,
.Xr acpi_asus 4 ,
.Xr acpi_dock 4 ,
.Xr acpi_fujitsu 4 ,
.Xr acpi_hp 4 ,
.Xr acpi_panasonic 4 ,
.Xr acpi_sony 4 ,
.Xr acpi_thermal 4 ,
.Xr acpi_thinkpad 4 ,
.Xr acpi_toshiba 4 ,
.Xr acpi_video 4 ,
.Xr aibs 4 ,
.Xr loader.conf 5 ,
.Xr acpibin 8 ,
.Xr acpicall 8 ,
.Xr acpiconf 8 ,
.Xr acpidump 8 ,
.Xr acpiexec 8 ,
.Xr acpixtract 8 ,
.Xr iasl 8
.Rs
.%A "Hewlett-Packard Corporation"
.%A "Intel Corporation"
.%A "Microsoft Corporation"
.%A "Phoenix Technologies Ltd."
.%A "Toshiba Corporation"
.%D November 13, 2013
.%T "Advanced Configuration and Power Interface Specification"
.%U http://acpi.info/spec.htm
.Re
.Sh AUTHORS
.An -nosplit
The ACPICA subsystem is developed and maintained by
Intel Architecture Labs.
.Pp
The following people made notable contributions to the ACPI subsystem
in
.Dx :
.An Michael Smith ,
.An Takanori Watanabe Aq Mt takawata@jp.FreeBSD.org ,
.An Mitsuru IWASAKI Aq Mt iwasaki@jp.FreeBSD.org ,
.An Munehiro Matsuda ,
.An Nate Lawson ,
the ACPI-jp mailing list at
.Aq Mt acpi-jp@jp.FreeBSD.org ,
and many other contributors.
.Pp
This manual page was written by
.An Michael Smith Aq Mt msmith@FreeBSD.org .
.Sh BUGS
Many BIOS versions have serious bugs that may cause system instability,
break suspend/resume, or prevent devices from operating properly due to
IRQ routing problems.
Upgrade your BIOS to the latest version available from the vendor before
deciding it is a problem with
.Nm .
.\".Pp
.\"The
.\".Nm
.\"CPU idle power management drive conflicts with the local APIC (LAPIC)
.\"timer.
.\"Disable APIC mode with
.\".Va hint.apic.0.disabled
.\"or do not use the
.\".Li C2
.\"and
.\".Li C3
.\"states if APIC mode is enabled.