man ACPI (4) | Special files and drivers | Unix Manual Pages

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man ACPI (4) | Special files and drivers | Unix Manual Pages | :man▋

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.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 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.

LOADER TUNABLES

Tunables can be set at the loader(8) prompt before booting the kernel or stored in /boot/loader.conf.

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. 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.
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.pci.link.%d.%d.%d.irq
	Override the interrupt to use.
hw.acpi.reset_video
	Enables calling the VESA reset BIOS vector on the resume path. Some graphic chips have problems such as LCD white-out after resume. Try setting this to 0 if this causes problems for you.
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.

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 (Vt device) Supports AC adapter.

bus (Vt feature) Probes and attaches subdevices. Disabling will avoid scanning the ACPI namespace entirely.

children (Vt 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 (Vt device) Supports ACPI button devices (typically power and sleep buttons).

cmbat (Vt device) Control-method batteries device.

cpu (Vt device) Supports CPU power-saving and speed-setting functions.

ec (Vt device) Supports the ACPI Embedded Controller interface, used to communicate with embedded platform controllers.

isa (Vt device) Supports an ISA bus bridge defined in the ACPI namespace, typically as a child of a PCI bus.

lid (Vt device) Supports an ACPI laptop lid switch, which typically puts a system to sleep.

quirks (Vt feature) Do not honor quirks. Quirks automatically disable ACPI functionality based on the XSDT table’s OEM vendor name and revision date.

pci (Vt device) Supports Host to PCI bridges.

pci_link (Vt feature) Performs PCI interrupt routing.

sysresource (Vt device) Pseudo-devices containing resources which ACPI claims.

thermal (Vt device) Supports system cooling and heat management.

timer (Vt device) Implements a timecounter using the ACPI fixed-frequency timer.

video (Vt 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
.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.

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
.Fx 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
.Fx 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 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
.Fx Ns -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.
.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.

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.