[ltp] Re: T410 does not have a power state below C3

Robert Tomsick linux-thinkpad@linux-thinkpad.org
Wed, 15 Dec 2010 10:35:23 -0500

On Wed, 2010-12-15 at 14:58 +0000, Pedro Ribeiro wrote:
> On 6 December 2010 21:26, Pedro Ribeiro <pedrib@gmail.com> wrote:
> > Hi all,
> >
> > I've just received my shiny new T410 and I'm trying to set up
> > everything correctly.
> >
> > One of the things I've noticed is that powertop shows that there is no
> > power state below C3.
> > I find this strange, since my T400 has C6 and its an older laptop.
> >
> > I've already upgraded to the latest BIOS and I tried changing the
> > power settings in the BIOS to automatic from the defaults and nothing
> > changed.
> >
> > One of the problems I've had with the T400 is that why an USB 1.1
> > device I could not hit a power state lower than C3 - however, I have
> > no such devices attached nor ohci_hcd loaded.
> >
> > Any ideas what I can do or why this doesn't work?
> >
> > Thanks for the help!
> > Pedro
> >
> Sorry for the insistence, but this is severely impacting my battery
> life, as well as creating a lot of heat.
> Does anyone here with a T410 have the same problem?
> Henrique, what's your take on this?

Perhaps C6 is somehow hidden by the BIOS?  (Just grasping at straws

Have we considered that powertop might be mis-reporting?  From the FAQ

"I see only C0, C1, and C2. Why don't the other C-states show?

It's mostly a BIOS thing. Some BIOS hide C3/C4 when on AC power, and
others show only C3 which is really a C4 underneath when on battery.
Note that the 'max_cstate:C8' value in /proc/acpi/processor/*/power
tells the maximum number of C-states the Linux kernel can handle, not
the number of C-states implemented in your hardware."

Some quick searching turned up a potentially-related kernel bugzilla
thread [2], but I don't know if it'll be of any help.

[1] http://www.linuxpowertop.org/faq.php
[2] https://bugzilla.kernel.org/show_bug.cgi?id=15064