Ubuntu Manpage: acpi — Advanced Configuration and Power Management support

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NAME

       acpi — Advanced Configuration and Power Management support

SYNOPSIS

       device acpi

       options ACPI_DEBUG
       options DDB

DESCRIPTION

       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. If the default
settings are not optimal, the following sysctls can be used to modify or monitor acpi behavior.

debug.acpi.enable_debug_objects
Enable dumping Debug objects without options ACPI_DEBUG. Default is 0, ignore Debug objects.

hw.acpi.acline
AC line state (1 means online, 0 means on battery power).

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.idle should
be set to acpi if it is listed in machdep.idle_available

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.

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.

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.

hw.acpi.lid_switch_state
Suspend state (S1–S5) to enter when the lid switch (i.e., a notebook screen) is closed. Default
is “NONE” (do nothing).

hw.acpi.power_button_state
Suspend state (S1–S5) to enter when the power button is pressed. Default is S5 (power-off
nicely).

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).

hw.acpi.s4bios
Indicate whether the system supports 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 (S4OS). Most current systems do not support S4BIOS.

hw.acpi.sleep_button_state
Suspend state (S1–S5) to enter when the sleep button is pressed. This is usually a special
function button on the keyboard. Default is S3 (suspend-to-RAM).

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.

hw.acpi.supported_sleep_state
Suspend states (S1–S5) supported by the BIOS.

S1 Quick suspend to RAM. The CPU enters a lower power state, but most peripherals are left
running.

S2 Lower power state than S1, but with the same basic characteristics. Not supported by
many systems.

S3 Suspend to RAM. Most devices are powered off, and the system stops running except for
memory refresh.

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 FreeBSD
unless S4BIOS is available.

S5 System shuts down cleanly and powers off.

hw.acpi.verbose
Enable verbose printing from the various ACPI subsystems.

LOADER TUNABLES

Tunables can be set at the loader(8) prompt before booting the kernel or stored in /boot/loader.conf.
Many of these tunables also have a matching sysctl(8) entry for access after boot.

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.cpu_unordered
Do not use the MADT to match ACPI Processor objects to CPUs. This is needed on a few systems
with a buggy BIOS that does not use consistent processor IDs. Default is 0 (disabled).

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

debug.acpi.interpreter_slack
Enable less strict ACPI implementations. Default is 1, ignore common BIOS mistakes.

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.

debug.acpi.resume_beep
Beep the PC speaker on resume. This can help diagnose suspend/resume problems. Default is 0
(disabled).

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.install_interface, hw.acpi.remove_interface
Install or remove OS interface(s) to control return value of ‘_OSI’ query method. When an OS
interface is specified in hw.acpi.install_interface, _OSI query for the interface returns it is
supported. Conversely, when an OS interface is specified in hw.acpi.remove_interface, _OSI query
returns it is not supported. Multiple interfaces can be specified in a comma-separated list and
any leading white spaces will be ignored. For example, "FreeBSD, Linux" is a valid list of two
interfaces "FreeBSD" and "Linux".

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).

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

hw.acpi.verbose
Turn on verbose debugging information about what ACPI is doing.

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 acpi enabled. "%s" is the name of the link (e.g.,
LNKA). "%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.

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 acpi enabled. "%s" is the name of the link (e.g., LNKA).

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 sub-drivers 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
XSDT 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 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-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_INIT             Initialization progress
       ACPI_LV_DEBUG_OBJECT     Stores to objects
       ACPI_LV_INFO             General information and progress
       ACPI_LV_REPAIR           Repair a common problem with predefined methods
       ACPI_LV_ALL_EXCEPTIONS   All the previous levels
       ACPI_LV_PARSE
       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       All the previous levels
       ACPI_LV_ALL              Synonym for "ACPI_LV_VERBOSITY2"
       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_VERBOSITY3"
       ACPI_LV_INIT_NAMES
       ACPI_LV_LOAD

       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.

COMPATIBILITY

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

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  <takawata@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@FreeBSD.org>.

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 acpi.

       The acpi CPU idle power management drive conflicts with the local APIC (LAPIC) timer.  Disable the  local
       APIC  timer  with  hint.apic.0.clock=0  or do not use the C3 and deeper states if the local APIC timer is
       enabled.

Debian                                             May 4, 2012                                           ACPI(4)