ACPI

Summary:

Fan status (on/off) and temperatures are displayed correctly.
CPU frequency changing (cpufreq) works and can give you a few
minutes of extra battery life.

You may want to install a program like cpufreq to automagically
adjust the CPU speed depending on the required computing power.

You can also manually limit the max. and min. CPU speed
by doing a:

echo "0%$MIN%$MAX%powersave" > /proc/cpufreq

For example the command

echo "0%40%70%powersave" > /proc/cpufreq

will limit the maximum CPU speed to 70% and will slow down the CPU when it is idle to 40%.

Note: As of kernel 2.6.10 /proc/cpufreq is deprecated, use /sys/devices/system/cpu/cpu0/cpufreq/scaling_*_freq instead.

Tested suspend methods:

Method	Status	Comments
Suspend-to-RAM (S3)	Works	In a very hackish way heh
Suspend-to-Disk (S4)	Doesn't work	Machine hangs on suspend
SoftwareSuspend 1	Works	Unload USB modules before suspending, or USB will cease to work after a resume.
SoftwareSuspend 2	Doesn't Work	Random hangs on suspend.

Suspend-to-RAM (S3)

I've put together a dedicated page about S3 on the P30

ACPI BIOS

The processor Cn states are not correctly recognised
because of an ACPI BIOS bug. "Throttling" doesn't work
because of the same bug.

This can be fixed by editing your DSDT and compiling it
into the kernel.

Below you'll find an already fixed DSDT and the required
kernel patch.

Installation:

• Patch your kernel to accept an external DSDT
• Copy dsdt.hex to /tmp
• Recompile your kernel

More information and HowTo's about DSDT's can be found
at the ACPI4Linux homepage.


But what excatly did you fix?

Many BIOS vendors use old and outdated BIOS manuals from INTEL.
Some of the manuals state that a certain value to identifiy wether a
CPU supports C2 / C3 / throttling has to be 0x07 if the CPU supports
these features.
However, this is wrong. The newer manuals state that the value has
to be 0x06, not 0x07. Linux discards a 0x07 which
is not a bug.
This simple fix allows the DSDT to compile and
changes this value from 0x07 to 0x06.
Credits go the ACPI-Devel mailing list where i've found this tip.

If BIOS vendors continue to ship DSDT's with a 0x07, Linux may one
day support this faulty value. This is not the case for 2.6.4-rc2-mm1.

Files of interest:

• "Custom DSDT" kernel patch against 2.6.4-rc2-mm1  (signature)
  
• Fixed DSDT table (HEX) - 512Mb RAM  (signature)
• Fixed DSDT table (dsl/ASCII)  (signature)
• Patch for the original DSDT (.dsl)  (signature)
• Original DSDT from Samsung  (signature)

The fixed DSDT can also be obtained from the ACPI4Linux homepage.