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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.

     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.  De-
	     fault is 0, use legacy reboot support.  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.disabled
	     Selectively disables portions of ACPI for debugging purposes.

     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.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_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_VERBOSITY3"

     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,	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   <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 APIC mode with hint.apic.0.disabled or do	not  use
     the C2 and C3 states if APIC mode is enabled.

FreeBSD 7.1			  July 29, 2006 			 ACPI(4)
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