Power off for PCI devices

Johannes Hofmann johannes.hofmann at gmx.de
Thu Sep 11 09:21:39 PDT 2008

Hasso Tepper <hasso at estpak.ee> wrote:
> Johannes Hofmann wrote:
>> Ah ok. Is there a way to verify the state of the pci devices?
>> On my T42 thinkpad I don't see any difference in power consumption
>> with hw.pci.do_power_nodriver=1 (measured with an external device and
>> battery removed). I'm always around 20 Watt, with est enabled,
>> "DynamicClocks" "on" in xorg.conf, and screen backlight set to the
>> lowest possible value.
> I use hw.pci.do_power_nodriver=3, btw, but it shouldn't matter much. Is 
> there unused devices at all? And these devices have to have power 
> management capabilities, not all PCI devices have these.
> I use sysutils/pciutils from pkgsrc to play with PCI configuration space. 
> It doesn't compile in DragonFly without the patch, pkgsrc bugreport is 
> there about year or so :(. Take patch is available at [1]. lspci -vvv 
> shows to you all devices with decoded configuration space. For example 
> ABOUT my wireless card it shows this:
> Capabilities: [40] Power Management version 2
>        Flags: PMEClk- DSI- D1+ D2- AuxCurrent=375mA 
>                PME(D0+,D1+,D2-,D3hot+,D3cold-)
>        Status: D3 PME-Enable- DSel=0 DScale=0 PME-
> Important bit is "Status: D3" - ie. this device is powered down.

lspci -vv indeed shows some devices (usb controller, sound card, ethernet card,
and modem) in D3 state.


> [1] - 
> http://leaf.dragonflybsd.org/~hasso/pkgsrc-patches/pkgsrc-sysutils-pciutils.patch

More information about the Submit mailing list