ACPI 是在本质上是一种发现设备、管理电源使用， 提供过去由 BIOS 管理的访问不同硬件的标准化方法。 让 ACPI 在各种系统上都能正确使用的工作一直在进行， 但许多主板的 ACPI 机器语言 (AML) 字节代码中的 bug， FreeBSD 的内核中资系统设计的不完善， 以及 Intel ACPI-CA 解释器中的 bug 仍然市场会出现。
这份文档期望能够帮助您协助 FreeBSD ACPI 的维护人员来找到您所观察到的问题的根源， 并通过调试找到其解决方法。 感谢您阅读这份文档， 我们也希望能够解决您的系统上的问题。
注: 在提交问题之前， 请确认您已经在运行最新的 BIOS 版本， 此外， 也包括嵌入式控制器的固件版本。
如果您希望提交一个问题， 请确保将下述信息法到 freebsd-acpi@FreeBSD.org
问题行为的描述， 包括系统类型、型号，以及任何触发问题的相关信息。 另外， 请注意尽可能准确地描述这一问题是否对您是陌生的。
在 ``boot -v''之后得到的 dmesg 输出， 包括任何在重现 bug 之后出现的错误信息。
在禁用了 ACPI 之后的 ``boot -v'' 的 dmesg 输出， 如果您发现禁用 ACPI 能够帮助消除问题。
来自 ``sysctl hw.acpi'' 的输出。 这也是找到您的系统所提供的功能的一种好办法。
能够得到您的 ACPI Source Language (ASL) 的 URL。 不要 把 ASL 直接发到邮件列表中， 因为它们可能非常大。 为了得到 ASL 您可以运行这个命令：
# acpidump -t -d > name-system.asl
(把 name 改为您的登录名， 并把 system 改为您的硬件制造商及其型号。 例如： njl-FooCo6000.asl)
许多开发者也会订阅 FreeBSD-CURRENT 邮件列表 但还是请发到 freebsd-acpi 这样它会被更多人看到。 请耐心等待， 因为我们都有全职的其他工作。 如果您的 bug 不是显而易见的， 我们可能会要求您通过 send-pr(1) 来提交一个 PR。 在输入 PR 时，请将同样的信息包含进去。 这将帮助我们来追踪和解决问题。 不要在给 freebsd-acpi 写信之前发送 PR 因为我们把它当作已知文体的备忘录而不是报告机制。 您的问题很可能已经被其他人报告过了。
ACPI is present in all modern computers that conform to the ia32 (x86), ia64 (Itanium), and amd64 (AMD) architectures. The full standard has many features including CPU performance management, power planes control, thermal zones, various battery systems, embedded controllers, and bus enumeration. Most systems implement less than the full standard. For instance, a desktop system usually only implements the bus enumeration parts while a laptop might have cooling and battery management support as well. Laptops also have suspend and resume, with their own associated complexity.
An ACPI-compliant system has various components. The BIOS and chipset vendors provide various fixed tables (e.g., FADT) in memory that specify things like the APIC map (used for SMP), config registers, and simple configuration values. Additionally, a table of bytecode (the Differentiated System Description Table DSDT) is provided that specifies a tree-like name space of devices and methods.
The ACPI driver must parse the fixed tables, implement an interpreter for the bytecode, and modify device drivers and the kernel to accept information from the ACPI subsystem. For FreeBSD, Intel has provided an interpreter (ACPI-CA) that is shared with Linux and NetBSD. The path to the ACPI-CA source code is src/sys/contrib/dev/acpica. The glue code that allows ACPI-CA to work on FreeBSD is in src/sys/dev/acpica/Osd. Finally, drivers that implement various ACPI devices are found in src/sys/dev/acpica.
For ACPI to work correctly, all the parts have to work correctly. Here are some common problems, in order of frequency of appearance, and some possible workarounds or fixes.
ACPI has three suspend to RAM (STR) states, S1-S3, and one suspend to disk state (STD), called S4. S5 is ``soft off'' and is the normal state your system is in when plugged in but not powered up. S4 can actually be implemented two separate ways. S4BIOS is a BIOS-assisted suspend to disk. S4OS is implemented entirely by the operating system.
Start by checking sysctl hw.acpi for the suspend-related items. Here are the results for my Thinkpad:
hw.acpi.supported_sleep_state: S3 S4 S5
hw.acpi.s4bios: 0
This means that I can use acpiconf -s to test S3, S4OS, and S5. If s4bios was one (1), I would have S4BIOS support instead of S4 OS.
When testing suspend/resume, start with S1, if supported. This state is most likely to work since it doesn't require much driver support. No one has implemented S2 but if you have it, it's similar to S1. The next thing to try is S3. This is the deepest STR state and requires a lot of driver support to properly reinitialize your hardware. If you have problems resuming, feel free to email the freebsd-acpi list but do not expect the problem to be resolved since there are a lot of drivers/hardware that need more testing and work.
To help isolate the problem, remove as many drivers from your kernel as possible. If it works, you can narrow down which driver is the problem by loading drivers until it fails again. Typically binary drivers like nvidia.ko, X11 display drivers, and USB will have the most problems while Ethernet interfaces usually work fine. If you can load/unload the drivers ok, you can automate this by putting the appropriate commands in /etc/rc.suspend and /etc/rc.resume. There is a commented-out example for unloading and loading a driver. Try setting hw.acpi.reset_video to zero (0) if your display is messed up after resume. Try setting longer or shorter values for hw.acpi.sleep_delay to see if that helps.
Another thing to try is load a recent Linux distribution with ACPI support and test their suspend/resume support on the same hardware. If it works on Linux, it's likely a FreeBSD driver problem and narrowing down which driver causes the problems will help us fix the problem. Note that the ACPI maintainers do not usually maintain other drivers (e.g sound, ATA, etc.) so any work done on tracking down a driver problem should probably eventually be posted to the freebsd-current list and mailed to the driver maintainer. If you are feeling adventurous, go ahead and start putting some debugging printf(3)s in a problematic driver to track down where in its resume function it hangs.
Finally, try disabling ACPI and enabling APM instead. If suspend/resume works with APM, you may be better off sticking with APM, especially on older hardware (pre-2000). It took vendors a while to get ACPI support correct and older hardware is more likely to have BIOS problems with ACPI.
Most system hangs are a result of lost interrupts or an interrupt storm. Chipsets have a lot of problems based on how the BIOS configures interrupts before boot, correctness of the APIC (MADT) table, and routing of the System Control Interrupt (SCI).
Interrupt storms can be distinguished from lost interrupts by checking the output of vmstat -i and looking at the line that has acpi0. If the counter is increasing at more than a couple per second, you have an interrupt storm. If the system appears hung, try breaking to DDB (CTRL+ALT+ESC on console) and type show interrupts.
Your best hope when dealing with interrupt problems is to try disabling APIC support with hint.apic.0.disabled="1" in loader.conf.
Panics are relatively rare for ACPI and are the top priority to be fixed. The first step is to isolate the steps to reproduce the panic (if possible) and get a backtrace. Follow the advice for enabling options DDB and setting up a serial console (see 第 20.6.5.3 节) or setting up a dump(8) partition. You can get a backtrace in DDB with tr. If you have to handwrite the backtrace, be sure to at least get the lowest five (5) and top five (5) lines in the trace.
Then, try to isolate the problem by booting with ACPI disabled. If that works, you can isolate the ACPI subsystem by using various values of debug.acpi.disable. See the acpi(4) manual page for some examples.
First, try setting hw.acpi.disable_on_poweroff=``0'' in loader.conf(5). This keeps ACPI from disabling various events during the shutdown process. Some systems need this value set to ``1'' (the default) for the same reason. This usually fixes the problem of a system powering up spontaneously after a suspend or poweroff.
If you have other problems with ACPI (working with a docking station, devices not detected, etc.), please email a description to the mailing list as well; however, some of these issues may be related to unfinished parts of the ACPI subsystem so they might take a while to be implemented. Please be patient and prepared to test patches we may send you.
The most common problem is the BIOS vendors providing incorrect (or outright buggy!) bytecode. This is usually manifested by kernel console messages like this:
ACPI-1287: *** Error: Method execution failed [\\_SB_.PCI0.LPC0.FIGD._STA] \\ (Node 0xc3f6d160), AE_NOT_FOUND
Often, you can resolve these problems by updating your BIOS to the latest revision. Most console messages are harmless but if you have other problems like battery status not working, they're a good place to start looking for problems in the AML. The bytecode, known as AML, is compiled from a source language called ASL. The AML is found in the table known as the DSDT. To get a copy of your ASL, use acpidump(8). You should use both the -t (show contents of the fixed tables) and -d (disassemble AML to ASL) options. See the Submitting Debugging Information section for an example syntax.
The simplest first check you can do is to recompile your ASL to check for errors. Warnings can usually be ignored but errors are bugs that will usually prevent ACPI from working correctly. To recompile your ASL, issue the following command:
# iasl your.asl
In the long run, our goal is for almost everyone to have ACPI work without any user intervention. At this point, however, we are still developing workarounds for common mistakes made by the BIOS vendors. The Microsoft interpreter (acpi.sys and acpiec.sys) does not strictly check for adherence to the standard, and thus many BIOS vendors who only test ACPI under Windows never fix their ASL. We hope to continue to identify and document exactly what non-standard behavior is allowed by Microsoft's interpreter and replicate it so FreeBSD can work without forcing users to fix the ASL. As a workaround and to help us identify behavior, you can fix the ASL manually. If this works for you, please send a diff(1) of the old and new ASL so we can possibly work around the buggy behavior in ACPI-CA and thus make your fix unnecessary.
Here is a list of common error messages, their cause, and how to fix them:
Some AML assumes the world consists of various Windows versions. You can tell FreeBSD to claim it is any OS to see if this fixes problems you may have. An easy way to override this is to set hw.acpi.osname=``Windows 2001'' in /boot/loader.conf or other similar strings you find in the ASL.
Some methods do not explicitly return a value as the standard requires. While ACPI-CA does not handle this, FreeBSD has a workaround that allows it to return the value implicitly. You can also add explicit Return statements where required if you know what value should be returned. To force iasl to compile the ASL, use the -f flag.
After you customize your.asl, you will want to compile it, run:
# iasl your.asl
You can add the -f flag to force creation of the AML, even if there are errors during compilation. Remember that some errors (e.g., missing Return statements) are automatically worked around by the interpreter.
DSDT.aml is the default output filename for iasl. You can load this instead of your BIOS's buggy copy (which is still present in flash memory) by editing /boot/loader.conf as follows:
acpi_dsdt_load="YES" acpi_dsdt_name="/boot/DSDT.aml"
Be sure to copy your DSDT.aml to the /boot directory.
The ACPI driver has a very flexible debugging facility. It allows you to specify a set of subsystems as well as the level of verbosity. The subsystems you wish to debug are specified as ``layers'' and are broken down into ACPI-CA components (ACPI_ALL_COMPONENTS) and ACPI hardware support (ACPI_ALL_DRIVERS). The verbosity of debugging output is specified as the ``level'' and ranges from ACPI_LV_ERROR (just report errors) to ACPI_LV_VERBOSE (everything). The ``level'' is a bitmask so multiple options can be set at once, separated by spaces. In practice, you will want to use a serial console to log the output if it is so long it flushes the console message buffer. A full list of the individual layers and levels is found in the acpi(4) manual page.
Debugging output is not enabled by default. To enable it, add options ACPI_DEBUG to your kernel config if ACPI is compiled into the kernel. You can add ACPI_DEBUG=1 to your /etc/make.conf to enable it globally. If it is a module, you can recompile just your acpi.ko module as follows:
# cd /sys/modules/acpi/acpi && make clean && make ACPI_DEBUG=1
Install acpi.ko in /boot/kernel and add your desired level and layer to loader.conf. This example enables debug messages for all ACPI-CA components and all ACPI hardware drivers (CPU, LID, etc.) It will only output error messages, the least verbose level.
debug.acpi.layer="ACPI_ALL_COMPONENTS ACPI_ALL_DRIVERS" debug.acpi.level="ACPI_LV_ERROR"
If the information you want is triggered by a specific event (say, a suspend and then resume), you can leave out changes to loader.conf and instead use sysctl to specify the layer and level after booting and preparing your system for the specific event. The sysctls are named the same as the tunables in loader.conf.
More information about ACPI may be found in the following locations:
The ACPI Mailing List Archives http://lists.freebsd.org/pipermail/freebsd-acpi/
The old ACPI Mailing List Archives http://home.jp.FreeBSD.org/mail-list/acpi-jp/
The ACPI 2.0 标准 http://acpi.info/spec.htm
FreeBSD 手册页: acpi(4), acpi_thermal(4), acpidump(8), iasl(8), acpidb(8)
DSDT 调试资源. (使用 Compaq 作为例子但通常情况下都很有用。)