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.Dd July 15, 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 ACPI CA reference implementation
from Intel.
.Pp
Note that the
.Nm
driver is automatically loaded by the
.Xr loader 8 ,
and should only be
compiled into the kernel on platforms where ACPI is mandatory.
.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.
Note that some variables will be available only if the given hardware supports
them (such as
.Va hw.acpi.acline ) .
.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 dev.cpu.N.cx_usage
Debugging information listing the percent of total usage for each sleep state.
The values are reset when
.Va dev.cpu.N.cx_lowest
is modified.
.It Va dev.cpu.N.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.idle
should be set to
.Li acpi
if it is listed in
.Va machdep.idle_available .
.It Va dev.cpu.N.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 dev.cpu.N.cx_method
List of supported CPU idle states and their transition methods, as
directed by the firmware.
.It Va hw.acpi.acline
AC line state (1 means online, 0 means on battery power).
.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.
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, or
.Dq Li NONE
.Pq do nothing .
Default is
.Dq Li NONE .
.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, or
.Dq Li NONE
.Pq do nothing .
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 Va debug.acpi.disabled
Selectively disables portions of ACPI for debugging purposes.
.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 return value of
.Ql _OSI
query method.
When an OS interface is specified in
.Va hw.acpi.install_interface ,
.Li _OSI
query for the interface returns it is
.Em supported .
Conversely, when an OS interface is specified in
.Va hw.acpi.remove_interface ,
.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.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.serialize_methods
Allow override of whether methods execute in parallel or not.
Enable this for serial behavior, which fixes
.Qq Li AE_ALREADY_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.
.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
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.
.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 ec
.Pq Vt device
Supports the ACPI Embedded Controller interface, used to communicate
with embedded platform controllers.
.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 mwait
.Pq Vt feature
Do not ask firmware for available x86-vendor specific methods to enter
.Li Cx
sleep states.
Only query and use the generic I/O-based entrance method.
The knob is provided to work around inconsistencies in the tables
filled by firmware.
.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
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 ACPI CA 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 ACPI-CA components, and the second is for
.Fx
drivers.
The ACPI-CA 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 ACPI-CA 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_POWER
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
.Fx
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_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
Synonym 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
.It Li ACPI_LV_LOAD
.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 ACPI-CA 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 ACPI CA subsystem is prefixed with the
module name in lowercase, followed by a source line number.
Output from the
.Fx 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.
.Fx
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, you must edit
.Pa /boot/loader.conf
and include the following lines.
.Bd -literal -offset indent
acpi_dsdt_load="YES"
acpi_dsdt_name="/boot/acpi_dsdt.aml" # You may change this name.
.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 COMPATIBILITY
ACPI is only found and supported on i386/ia32 and amd64.
.Sh SEE ALSO
.Xr kenv 1 ,
.Xr acpi_thermal 4 ,
.Xr device.hints 5 ,
.Xr loader.conf 5 ,
.Xr acpiconf 8 ,
.Xr acpidump 8 ,
.Xr config 8 ,
.Xr iasl 8
.Rs
.%A "Compaq Computer Corporation"
.%A "Intel Corporation"
.%A "Microsoft Corporation"
.%A "Phoenix Technologies Ltd."
.%A "Toshiba Corporation"
.%D August 25, 2003
.%T "Advanced Configuration and Power Interface Specification"
.%U http://acpi.info/spec.htm
.Re
.Sh AUTHORS
.An -nosplit
The ACPI CA subsystem is developed and maintained by
Intel Architecture Labs.
.Pp
The following people made notable contributions to the ACPI subsystem
in
.Fx :
.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 .