laptop battery story

05 July, 2009

Power Management Guide(Troubleshooting)

Q: I'm trying to change the CPU frequency, but /sys/devices/system/cpu/cpu0/cpufreq/scaling_governor Hp laptop battery does not exist.
A: Make sure your processor supports CPU frequency scaling and you chose the right CPUFreq driver for your processor. Here is a list of processors that are supported by cpufreq (kernel 2.6.7): ARM Integrator, ARM-SA1100, ARM-SA1110, AMD Elan - SC400, SC410, AMD mobile K6-2+, AMD mobile K6-3+, AMD mobile Duron, AMD mobile Athlon, AMD Opteron, AMD Athlon 64, Cyrix Media GXm, Intel mobile PIII and Intel mobile PIII-M on certain Hp EV087AA battery chipsets, Intel Pentium 4, Intel Xeon, Intel Pentium M (Centrino), National Semiconductors Geode GX, Transmeta Crusoe, VIA Cyrix 3 / C3, UltraSPARC-III, SuperH SH-3, SH-4, several "PowerBook" and "iBook2" and various processors on some ACPI 2.0-compatible systems (only if "ACPI Processor Performance States" are available to the ACPI/BIOS interface).

Q: My laptop supports frequency scaling, but /sys/devices/system/cpu/cpu0/cpufreq/ is empty.

A: Look for ACPI related error messages with dmesg | grep ACPI. Try to update the BIOS, especially if a broken DSDT is reported. You can also try to fix it yourself (which is beyond the scope of this guide).

Q: My laptop supports frequency scaling, but according to /proc/cpuinfo the speed never changes.

A: Probably you have activated symmetric multiprocessing support (CONFIG_SMP) in your kernel. Deactivate it and it should work. Some older kernels had a bug Hp EX942AA battery causing this. In that case, run emerge x86info, update your kernel as asked and check the current frequency with x86info -mhz.

Q: I can change the CPU frequency, but the range is not as wide as in another OS.

A: You can combine frequency scaling with ACPI throttling to get a lower minimum frequency. Notice that throttling doesn't save much energy and is mainly used for thermal management (keeping your laptop cool and quiet). You can read the current throttling state Hp Pavilion ZT3000 battery with cat /proc/acpi/processor/CPU/throttling and change it with echo -n "0:x" > /proc/acpi/processor/CPU/limit, where x is one of the Tx states listed in /proc/acpi/processor/CPU/throttling.

Q: When configuring the kernel, powersave, performance and userspace governors show up, but that ondemand thing is missing. Where do I get it?

A: The ondemand governor is only included in recent kernel sources. Try updating them.

Q: Battery life time seems to be worse than before.

A: Check your BIOS settings. Maybe you forgot to re-enable some of the Hp 337607-001 battery settings.

Q: My battery is charged, but KDE reports there would be 0% left and immediately shuts down.

A: Check that battery support is compiled into your kernel. If you use it as a module, make sure the module is loaded.

Q: My system logger reports things like "logger: ACPI group battery / action battery Hp 337607-003 battery is not defined".

A: This message is generated by the /etc/acpi/default.sh script that is shipped with acpid. You can safely ignore it. If you like to get rid of it, you can comment the appropriate line in /etc/acpi/default.sh as shown below:

Code Listing 8.1: Disabling warnings about unknown acpi events

*) # logger "ACPI action $action is not defined"

Q: I have a Dell Inspiron 51XX and I don't get any ACPI events.

A: This seems to be a kernel bug. Read Hp 398876-001 battery on here.

Q: I activated the DynamicClocks option in xorg.conf and now X.org crashes / the screen stays black / my laptop doesn't shutdown properly.

A: This happens on some systems. You have to disable DynamicClocks.

Q: I want to use TuxOnIce, but it tells me my swap partition is too small. Resizing is not an option.

A: If there is enough free space on your system, you can use the filewriter instead of the swapwriter. The hibernate-script supports it as well. More information can be found in /usr/src/linux/Documentation/power/tuxonice.txt.

Q: I just bought a brand new battery, but it only lasts for some minutes! What am I doing wrong?

A: First follow your manufacturer's advice on how to charge the battery Hp PB992A battery correctly.

Q: The above didn't help. What should I do then?

A: Some batteries sold as "new" are in fact old ones. Try the following:

Code Listing 8.2: Querying battery Hp PB994A battery state

$ grep capacity /proc/acpi/battery/BAT0/info
design capacity: 47520 mWh
last full capacity: 41830 mWh

If the "last full capacity" differs significantly from the design capacity, your battery is probably broken. Try to claim your warranty.

Q: My problem is not listed above. Where should I go next?

A: Don't fear to contact me, Dennis Nienhüser, directly. The Gentoo Forums are a good place to get help as well. If you prefer IRC, try the #gentoo-laptop Hp PB991A battery channel

Power Management Guide(Troubleshooting)

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