Re: Information regarding C3 cpu state and bus mastering activity

[Erik Slagter <erik-KW7PGP3XNp7a5EbDDlwbIw@public.gmane.org>]

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On Tue, 2005-12-13 at 15:06 +0100, Pavel Machek wrote:
> On Ne 11-12-05 21:10:53, Marco Calviani wrote:
> > Hi acpi-devel list,
> >    I have a problem regarding C3 states and usb. When i'm plugging in any
> > usb devices, the my busmaster activity starts couting preventing the
> > cpu to go to C3 state. Obviously if i unload all usb-related modules,
> > C3 state goes in, my battery lives longer and the laptop stays quiter;
> > unfortunately i need an usb-mouse (and possibly also an external USB drive.
> > I've read somewhere that this is a specific ACPI standard behaviuor
> > but i'm asking if this can be modified in some way, i.d. is it
> > possible, with some workarounds, to enter C3 state also with the usb
> > modules?
> 
> Fix USB to send mouse into runtime-sleep state. That will allow C3 to
> be used as long as you are not actively moving the mouse.

Weird. I have a usb mouse (amongst others) connected and I have this:

active state:            C4
max_cstate:              C8
bus master activity:     10180000
states:
    C1:                  type[C1] promotion[C2] demotion[--] latency[001] usage[00000010]
    C2:                  type[C2] promotion[C3] demotion[C1] latency[001] usage[145683351]
    C3:                  type[C3] promotion[C4] demotion[C2] latency[085] usage[31777840]
   *C4:                  type[C3] promotion[--] demotion[C3] latency[185] usage[66550298]

So, is this phenomenon specific to a certain hardware layout?

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