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ACPI(4) Device Drivers Manual ACPI(4)

acpi — Advanced Configuration and Power Management support

device acpi


options ACPI_DEBUG
options DDB

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 ACPICA reference implementation from Intel.

The acpi driver is usually compiled into the kernel, and it is automatically loaded by the loader(8) if it is not in the kernel configuration file. The loader menu provides a menu item to boot without ACPI. See also DISABLING ACPI below.

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.cpu_idle_hlt must be set to 2 (the default value).
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. Default 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 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.
Quick suspend to RAM. The CPU enters a lower power state, but most peripherals are left running.
Lower power state than S1, but with the same basic characteristics. Not supported by many systems.
Suspend to RAM. Most devices are powered off, and the system stops running except for memory refresh.
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.
System shuts down cleanly and powers off.
hw.acpi.verbose
Enable verbose printing from the various ACPI subsystems.

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. It is relative to /boot/kernel.
debug.acpi.allow_method_calls
If set, the acpicall(8) utility can be used to directly call ACPI methods for debugging and tweaking purposes.
debug.acpi.disabled
Selectively disables portions of ACPI that are enabled by default, for debugging purposes.
debug.acpi.enabled
Selectively enables portions of ACPI that are disabled by default, for debugging purposes.
debug.acpi.facs_addr32
Favor 32-bit FACS table addresses over the 64-bit addresses.
debug.acpi.fadt_addr32
Favor 32-bit FADT register addresses over the 64-bit addresses.
debug.acpi.ignore_xsdt
Ignore the XSDT, forcing the use of the RSDT.
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 the return value of the ‘_OSI’ query method. When an OS interface is specified in hw.acpi.install_interface, the _OSI query for the interface returns it is . Conversely, when an OS interface is specified in hw.acpi.remove_interface, the _OSI query returns it is . 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.auto_serialize_methods
Auto-serialization of control methods to proactively prevent problems with ill-behaved reentrant control methods that create named ACPI objects. Default is 1 (enabled).
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).

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.

Disabling all or part of ACPI 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:

Disable all ACPI features and devices.
(device) Supports AC adapter.
(feature) Probes and attaches subdevices. Disabling will avoid scanning the ACPI namespace entirely.
(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.
(device) Supports ACPI button devices (typically power and sleep buttons).
(device) Control-method batteries device.
(device) Supports CPU power-saving and speed-setting functions.
(device) Supports CPU power-saving. Disabling “cpu” will also disable this device.
(device) Supports CPU speed-setting. Disabling “cpu” will also disable this device.
(device) Docking station device.
(device) Supports the ACPI Embedded Controller interface, used to communicate with embedded platform controllers.
(feature) Supports the High Precision Event Timer.
(device) Supports an ISA bus bridge defined in the ACPI namespace, typically as a child of a PCI bus.
(device) Supports an ACPI laptop lid switch, which typically puts a system to sleep.
(feature) Do not honor quirks. Quirks automatically disable ACPI functionality based on the XSDT table's OEM vendor name and revision date.
(device) Supports Host to PCI bridges.
(feature) Performs PCI interrupt routing.
(device) Pseudo-devices containing resources which ACPI claims.
(device) Supports system cooling and heat management.
(device) Implements a timecounter using the ACPI fixed-frequency timer.
(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 ACPICA code will still know about the avoided region.

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 ACPICA components, and the second is for DragonFly drivers. The ACPICA layer descriptions include the prefix for the files they refer to. The supported layers are:

Utility ("ut") functions
Hardware access ("hw")
Event and GPE ("ev")
Table access ("tb")
Namespace evaluation ("ns")
AML parser ("ps")
Internal representation of interpreter state ("ds")
Execute AML methods ("ex")
Resource parsing ("rs")
Debugger implementation ("db", "dm")
Usermode support routines ("os")
Disassembler implementation (unused)
All the above ACPICA components
AC adapter driver
Control-method battery driver
ACPI, ISA, and PCI bus drivers
Power and sleep button driver
Embedded controller driver
Fan driver
Platform-specific driver for hotkeys, LED, etc.
Power resource driver
CPU driver
Thermal zone driver
Timer driver
All the above DragonFly ACPI drivers

The supported levels are:

Initialization progress
Stores to objects
General information and progress
Repair a common problem with predefined methods
All the previous levels
 
 
 
 
 
 
 
 
 
 
 
 
 
All the previous levels
 
 
 
All the previous levels
Alias for "ACPI_LV_VERBOSITY2"
 
 
 
 
All the previous levels
 
 
 
 
All levels after "ACPI_LV_VERBOSITY3"
Needs to be specified separately
Needs to be specified separately

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 ACPICA 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 ACPICA subsystem is prefixed with the module name in lowercase, followed by a source line number. Output from the DragonFly-local code follows the same format, but the module name is uppercased.

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. DragonFly 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, copy it to /boot/kernel/acpi_dsdt.aml and add the following line to /boot/loader.conf.

acpi_dsdt_load="YES"

In order to prepare your AML code, you will need the acpidump(8) and iasl(8) utilities and some ACPI knowledge.

kenv(1), acpi_asus(4), acpi_dock(4), acpi_fujitsu(4), acpi_hp(4), acpi_panasonic(4), acpi_sony(4), acpi_thermal(4), acpi_thinkpad(4), acpi_toshiba(4), acpi_video(4), aibs(4), loader.conf(5), acpibin(8), acpicall(8), acpiconf(8), acpidump(8), acpiexec(8), acpinames(8), acpixtract(8), config(8), iasl(8)

Hewlett-Packard Corporation, Intel Corporation, Microsoft Corporation, Phoenix Technologies Ltd., and Toshiba Corporation, Advanced Configuration and Power Interface Specification, November 13, 2013, http://acpi.info/spec.htm.

The ACPICA subsystem is developed and maintained by Intel Architecture Labs.

The following people made notable contributions to the ACPI subsystem in DragonFly: 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>.

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.

February 16, 2019 DragonFly-5.6.1