[ltp] Aggressive Powersaving

Karsten König linux-thinkpad@linux-thinkpad.org
Thu, 25 Feb 2010 22:57:04 +0100

Am Dienstag, 9. Februar 2010 16:16:36 schrieb Henrique de Moraes Holschuh:
> On Tue, 09 Feb 2010, Karsten König wrote:
> > the new kernels really brought down the power consumption and I am
> > interested in getting it a little bit further, on the road I don't use =
> > DVD drive nor ExpressCard nor USB nor Firewire nor Touchpad, is there a
> > way to cleany cut the power to these devices/buses?
> Yes.  Disable them on the BIOS where possible, Linux doesn't put PCI
>  devices in D3 state yet as a rule, so once a driver loads and brings that
>  device to D0 state, the device will stay powered up.  There might be
>  exceptions.

Hmm I disabled things like parallel port, bus disabling FireWire USB etc in 
the BIOS is not very practical as I want to use them without having to switch 
in the BIOS
But the PCI D3 states got me to 
http://www.mjmwired.net/kernel/Documentation/power/pci.txt where the different 
states and their transitions are documented, but I can't find sysfs knobs for 
it, so I can't tell the kernel to just suspend the whole USB stack unless 
something blocks it? I imagine this as a smaller part of the suspend cycle, I 
only want parts of the system to switch off.

> As for the DVD, eject the bay through sysfs (which will power it down with
> the device still inside), and tell the kernel to put the SATA link in the
> highest power saving mode (sysfs again).

Ok, this is the same as the eject script right? This does indeed still save 
0.5W, too bad this can't be done automatically.

> > I don't know about VGA and modem, but I think they aren't that easy
> > accessible because they are part of the graphics driver and alsa (it do=
> > drive the winmodem right?)
> Disable the modem in the BIOS when not in use.  Same for serial ports, IR
> ports, the floppy controller, parallel ports...

Yeah I went through the stuff I never need already, seemed to have helped a 
little =)