How to make ACPI work

general

First of all you'll have to enable ACPI support in your kernel (if your distro doesn't already have an ACPI enabled kernel). To do this open your kernel config, go to Power management options, enable Power Management support, go to ACPI and enable the needed options. You'd most likely want to enable Sleep States, AC Adapter, Battery, Fan, Processor and Thermal Zone. Then recompile your kernel.

If you prefer editing your .config file directly, you should set at least the following variables:

CONFIG_PM=y
CONFIG_ACPI_BOOT=y
CONFIG_ACPI_INTERPRETER=y
CONFIG_ACPI_SLEEP=y
CONFIG_ACPI_SLEEP_PROC_FS=y
CONFIG_ACPI_AC=y
CONFIG_ACPI_BATTERY=y
CONFIG_ACPI_BUTTON=y
CONFIG_ACPI_FAN=y
CONFIG_ACPI_PROCESSOR=y
CONFIG_ACPI_THERMAL=y
CONFIG_ACPI_BUS=y
CONFIG_ACPI_EC=y
CONFIG_ACPI_POWER=y
CONFIG_ACPI_PCI=y
CONFIG_ACPI_SYSTEM=y

Unfortunately, special drivers for ACPI on ThinkPads were not included with kernels prior 2.6.10. So you'll have to compile one yourself. You have the choice between thinkpad-acpi and ibm-acpi, with the latter being the recommended one.

Also you'll need to install acpid, if it isn't present on your system. acpid is a daemon that handles the ACPI events generated by the system. Basically, acpid just executes scripts residing in /etc/acpi/actions. Which script to launch at which event is configured in several files in /etc/acpi/events. See man acpid for more information on how to configure acpid. The ibm-acpi packages includes example scripts in the config folder inside the tarball. They are a good starting point to adjust them to your needs. You also might have a look at the ACPI section of the Configs page and you can find information about the event strings ibm-acpi generates for certain keys at the Special Keys HOWTO.

In general it is a good idea to read the README included with the ibm-acpi source tarball.

Screen blanking (Standby)

Make sure you have

• Option "DPMS"

in the Monitor section of your XF86Config/xorg.conf.

Running xset +dpms and then xset dpms force off will turn off the backlight on a laptop screen.
To force a screen off that is using a radeon chipset, install the radeontool package.

Suspend to RAM (Sleep)

ACPI Sleep and suspend-to-ram with recent 2.6.x kernels usually works fine. However, the following glitches may or may not occur:

• With a 2.6.9 or 2.6.10 kernel, when resuming from a suspend-to-ram the display might remain black (the system is still rebootable via ctrl-alt-del). This can be fixed by adding "acpi_sleep=s3_bios" to the kernel boot parameters. It seems this problem is solved in 2.6.11-rc1.
• When your system is equiped with a Radeon Mobility graphic controller your LCD backlight may not turn off automatically. Use radeontool to switch off your backlight prior suspend in your script.
• Also, you might want to take note of the Problem with high power drain in ACPI sleep.
• You may experience problems when using "echo standby > /sys/power/state" (machine goes to sleep and wakes up immediately). This can be avoided by using "echo -n 3 >/proc/acpi/sleep" to get it to sleep.
• Problems with the serial port of the port replicator after the wake up from ram have also been experienced.

Suspend to disk (Hibernate)

There are two drivers for this available:

• swsusp, which is in the kernel and
• SoftwareSuspend2 which is more feature rich, but not yet in the kernel, so you have to patch it in yourself

Both are reported to work fine as long as you use open-source graphic drivers. A comparison of the features can be found on this page.

Just in case you are in doubt...yes, it is safe in both cases to use the same swap partition as active swap and as suspend partition.

using swsusp

Software Suspend (swsusp) is included in the 2.6 kernel series. It seems like no patches for 2.4 kernels are available.

To enable it, go to Power management options and enable Power management support and Software Suspend in the kernel config menu. You'll also want to give the swap partition to suspend to in Default resume partition.

In case you prefer to edit your config file directly, you should have the following three entries look like here...

CONFIG_PM=y
CONFIG_SOFTWARE_SUSPEND=y
CONFIG_PM_STD_PARTITION="/dev/resume_partition"

...where /dev/resume_partition needs to be replaced by the swap partition you want to use for suspending. (Use fdisk -l /dev/hda if unsure.)

You can override the default resume partition anytime by giving resume=/dev/resume_partition as kernel boot parameter. Also, in case you suspended, but want to boot up normally (without resuming from the saved image - loosing all data that was unsaved at suspend time), you can give the noresume kernel boot parameter.

To suspend you can either do a simple echo -n 4 > /proc/acpi/sleep (recommended) or use the patched SysVInit and call swsusp or shutdown -z now.

Ideally you would do this from a script like /etc/acpi/actions/hibernate.sh. It has proven to be a good idea to shutdown the following processes/drivers within the script before you do the actual suspend.

• any running mysql server
• the madwifi driver, if you happen to use it
• the linuxant driver may require stopping in a acpi script as well. dldrstop does the trick.

Afterwards you might want to enable them again, as well as run a script that does necessary configurations according to the ac power state. Furthermore, the system clock is not readjusted automatically, so you will probably also want the do that from that script (i.e. by restarting your systemclock bootup script).

Finally you should take note that swsusp does not set the ACPI S4 state. Instead it goes to S5. This means that the machine itself doesn't know that it was suspend rather than shutdown. Hence you can i.e. boot a parallel installed other operating system and resume your linux session later, as long as you don't touch the swap partition the image was saved to.

using SoftwareSuspend2

Todo...