(Missing) power states of an Atom N455-based netbook

[Vitaly Magerya]

Andriy Gapon <avg at freebsd.org> wrote:
>>     VDRV: 00 -> 01
>
> Looks like this variable should tell if OS has ACPI Video driver, to be precise
> if _BCL method was invoked at least once.
> Looks like in your case the driver doesn't attach for some reason?..

I don't have acpi_video loaded (it's not loaded by default). If I
do load it, VDRV indeed becomes 1 (brightness controls that acpi_video
exposes don't work though; this appears to be a known problem with
Samsung laptops).

> Unfortunately, I don't remember if or where you provided your dmesg.

It's at [1].

>> (Note that C1ON is 0 just as with FreeBSD, and yet powertop does
>> report C2 and C4).
>
> [...]
>
> Actually, it seems that they have them simply hardcoded:
> http://lxr.linux.no/#linux+v2.6.39/drivers/idle/intel_idle.c#L171
> I am not sure how to check on Linux which cpuidle driver is being used.  If you
> know, could please check that?  And if the driver is intel_idle, then there is
> no mystery, they use those hardcoded values.

I think the mystery is solved then:

    $ cat /sys/devices/system/cpu/cpuidle/current_driver
    intel_idle

>> Then, after about 4 minutes of uptime, C1ON changes to 1 (and
>> powertop still reports the same states).
>
> OK, no difference here.  So it's probably done by firmware based on some unknown
> logic.

It seems that way.

[1] http://tx97.net/~magv/dmesg-n143-verbose.82.txt