RE: Processor C states and USB problem

[Diego SANTA CRUZ <Diego.SantaCruz-p8DiymsW2f8@public.gmane.org>]

Hi,

I picked up this thread and I'm interested in knowing a bit more about
bus mastering and C3, as my laptop never goes into C3. I own a Dell
Inspiron 8500 (details at
http://ltswww.epfl.ch/~dsanta/resources/dell-i8500-linux).

This is what I get for the power states:
# cat /proc/acpi/processor/CPU0/power
active state:            C2
default state:           C1
bus master activity:     ffffffff
states:
    C1:                  promotion[C2] demotion[--] latency[000] usage[00039800]
   *C2:                  promotion[C3] demotion[C1] latency[050] usage[00573330]
    C3:                  promotion[--] demotion[C2] latency[050] usage[00000004]

I tried booting with init=/bin/sh and manually loading the processor
module, without any external hardware attached, so that no special
hardware is initialized, but still there is non-stopping bus mastering
activity. What could be causing it? Any ideas how could I find out?

BTW, I'm running the latest Fedora Core 1 kernel (2.4.22-1.2140.nptl)

Thanks for any info,

Diego

On Mon, 2004-01-05 at 10:06, Li, Shaohua wrote:
> Hi,
> C3 is a kind of idle, it means deep power saving.
> Actually, I observed the same symptom as you: USB devices caused many bus master activities, which make processor can't enter C3.
>  
> Thanks,
> Shaohua

-- 
-------------------------------------------------------
Diego Santa Cruz - PhD
Publications available at http://ltswww.epfl.ch/~dsanta
Signal Processing Institute (LTS1 / ITS / STI)
Swiss Federal Institute of Technology (EPFL)
EPFL - STI - ITS, CH-1015 Lausanne, Switzerland
E-mail:     Diego.SantaCruz-p8DiymsW2f8@public.gmane.org
Phone:      +41 - 21 - 693 26 57
Fax:        +41 - 21 - 693 76 00
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