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ACPI(4) 		     Kernel Interfaces Manual			 ACPI(4)

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  (super-
     seding 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  manda-
     tory.

SYSCTL VARIABLES
     The acpi driver is intended to provide power management without user inter-
     vention.	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  dic-
	     tates.   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 pro-
	     vide 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  note-
	     book 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  charac-
		     teristics.  Not supported by many systems.

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

	     S4      Suspend to disk.  All devices are powered off, and the sys-
		     tem  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 con-
	     sistent 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 com-
	     mon BIOS mistakes.

     debug.acpi.max_threads
	     Specify the number of task threads that are started on boot.   Lim-
	     iting  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/re-
	     sume 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	increas-
	     ing 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.  En-
	     able this for serial behavior, which fixes "AE_ALREADY_EXISTS"  er-
	     rors  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 capa-
	     bility should be used carefully, and only if a device is not  work-
	     ing  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  black-
     list.   Currently,  the blacklist only controls whether acpi should be dis-
     abled or not.  In the future, it will have more granularity to control fea-
     tures (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  dis-
     abled.   Other i386 machines fail with ACPI enabled.  Disabling all or part
     of ACPI on non-i386 platforms (i.e., platforms where ACPI support is manda-
     tory) may result in a non-functional system.

     The acpi driver comprises a set of drivers, which may be  selectively  dis-
     abled  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  enu-
		  merated  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 func-
		  tions.

     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  name-
		  space, 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-fre-
		  quency 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 debug-
     ging output.

     Both layers and levels are specified as a whitespace-separated list of  to-
     kens,    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 configura-
     tion is a good way to gather initial information.	It enables debug  output
     for  both ACPI-CA and the acpi driver, printing basic information about er-
     rors, 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  upper-
     cased.

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  con-
     tains  a  bug that does not appear when parsed by the Microsoft implementa-
     tion.  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,  http://acpi.info/spec.htm,  August  25,
     2003.

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 con-
     tributors.

     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.

FreeBSD 9.1			   May 4, 2012				 ACPI(4)
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