C-States lower than C2 impossible with USB?

[Arjan van de Ven]

Peter Ganzhorn wrote:
> After searching for possible causes for my problem I identified USB to
> be the problem - disconnecting all USB devices from my system will make
> the CPU enter C3 state a lot, about 50% with more than 20ms are reported
> by powertop.
> Unfortunately I have a usb mouse, usb keyboard und two external usb hard
> drives - and I don't want to miss any of them. Using USB-to-PS2 adapters
> may be an imperfect solution for mouse and keyboard, but the hard drives
> will remain an issue for sure.
> Is there any possible way to make the system to go to C3 with USB
> devices attached???
> On Google I read that Microsoft released a hot-fix for Windows which is
> said to fix this issue, so I hope there is a way to do this with Linux
> as well.
> 

as far as I know, Linux unfortunately does not support this feature 
(HID auto suspend) yet... I hope people are working on it; if not I 
might end up spending some time (or time of people working in my group 
;) on it...