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#1 2009-03-16 10:53:12

vinvin
Member
Registered: 2009-03-12
Posts: 24

Power consumption: set devices in sleep mode

Hello,
I'm new in the laptop universe, with an Eee PC 900, and I am concerned about a few questions on power management and device sleep mode.

In the BIOS, I can choose not to use some internal devices, like the sound or ethernet chips. But then, I won't be able to find them or activate them from the OS. If I enable them in the BIOS, they are powered, the kernel finds them, but then, I am not able to power them down when I don't use them (I mean, I don't know how to do it).

I guess that linux is able to handle the fact that people are not always using every device present in their computer, and thus gives a way to power down some devices that the user doesn't need. My list would be: ethernet chip, wlan chip, sound chip, usb hub and all internal usb devices (camera, card reader), ps2 mouse.
There is a specific module for the laptop I'm using, which allows to standby and wake up the camera and the card reader, and there is the special sysfs item, rfkill for controlling the wlan activity. But what about the ethernet, the sound, usb hubs, and the mouse?


Second issue: is there a way to control the threshold of the low batt led indicator?
I can access battery level in /proc/acpi/battery/BAT0/state, and the led starts flashing at 20%. The problem is that 20% of this indicator lasts around 2 hours, while it takes 1 and a half hour to go from 100% to 20%. Is there a problem in the battery driver, or is it a hardware-programmed function? Can it be changed?

Thanks!

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#2 2009-03-18 01:06:40

big_gie
Member
Registered: 2005-01-19
Posts: 637

Re: Power consumption: set devices in sleep mode

You can disable some hw on the Eee.  For wifi and bluetooth, there is an rfkill switch and a disable switch.  There is also a disable switch for the webcam. As for the ethernet, either the driver has good power management, or you you modprobe -r the driver.

Usb has a power management too, I'm not sure if it is really efficient.

On my experience when devices are not used they dont draw too much power. I could be wrong though. Its hard to diagnose, since disabling some hw like your touchpad is hard on the usability.

Try powertop, it will tell you what is drawing power and what you can do. You could try my acpi-eeepc-generic package to control some parts of the eee.

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#3 2009-03-19 12:15:37

vinvin
Member
Registered: 2009-03-12
Posts: 24

Re: Power consumption: set devices in sleep mode

Thanks for the reply big_gie.
I have been looking for information on the net, and I found a few tricks that may be helpful.

For wifi, ok, there is rfkill.

For ethernet, ethtool seems to be promising. I don't know if removing the atl2 module is helps on power saving,
but I've seen something about wake-on-lan-aware device which were more often woken-up than non-supporting ones. Thus, WOL can be disabled with this command: ethtool -s eth0 wol d

For sound, there is an option in the snd_hda_intel driver, CONFIG_SND_HDA_POWER_SAVE which has a configurable timeout for sound chip activity before entering sleep mode. And indeed, the background fuzz disappears after the number of configured seconds after playing something.

For USB, powertop recommends some usb.autosuspend trick. I don't know how efficient this is. Card reader and Webcam have an entry in /proc to enable or disable them.

For touchpad, one told me that I can use gsynaptics to disable it.

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#4 2009-03-19 12:58:31

big_gie
Member
Registered: 2005-01-19
Posts: 637

Re: Power consumption: set devices in sleep mode

If you want to disable permanently your touchpad, then just don't load the driver at all. Don't load the driver _and_ the application just to disable it...

What gsynaptic does, and what you can do manually, is using SHMConfig to disable it through the driver. Look it up.

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#5 2009-03-19 13:00:36

vinvin
Member
Registered: 2009-03-12
Posts: 24

Re: Power consumption: set devices in sleep mode

Thanks for the information, i'll take a look to SHMConfig.

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