Power off for PCI devices

Hasso Tepper hasso at estpak.ee
Wed Sep 10 23:56:48 PDT 2008

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 
	Status: D3 PME-Enable- DSel=0 DScale=0 PME-

Important bit is "Status: D3" - ie. this device is powered down.

[1] - 

Hasso Tepper

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