> > > For notebooks, devices *are* islands. powerop tries to push > > > everything-depends-on-everything model that may be good for some SoC, > > > but sucks for notebooks. We need some middle ground. > > > > USB being enabled and causing your laptop battery to dry up is a case > > where laptop device dependency has been shown. There are likely many > > more cases. I would expect BIOS/chip set developers are all too aware > > of these in their sub-domains. > > No, it is because USB enabled prevents cpu from sleeping; it is > actually well known. I vaguely recall hearing the why. It has some DMAs which are going on and I suppose the processor must service the completions. Now, if you coordinated with the USB device some how, you could try and place the USB bus into suspend mode, and only wake up on USB remote wake up or data to be sent, they you could likely spend a lot more time in a lower P state. How are you to know when it is ok to shut off the USB bus? Is that something which could be coordinated with the processor and the active use case. If I don't need high performance I could go in and out of suspend to save power. Knowing high, or low performance helps in this case :) Regards, Richard W.
