[ltp] C4 after powertop-update

[Arno Trautmann]

Hi Guys!

You often helped me to better understand my machine, and I am very 
thankful for this… so now I have again a question that is for 
understanding, and not a problem… so everything works fine, but I want 
to know why…

X61s, Arch Linux
Yesterday I upgradet my system (pacman -Syu) and downloaded a new 
powertop-version. When I start it, I get the output

Your CPU supports the following C-states : C1 C2 C3 C4
Your BIOS reports the following C-states : C1 C2 C3

which has never been there before. And just now I am really confused: 
yesterday it showed me for the BIOS C1 C2 C4… and in powertop itself it 
showed me that the CPU was in C4—I was really happy about this ;)
powertop says:

Cn                Avg residency       P-states (frequencies)
C0 (cpu running)        ( 4.2%)         1.61 Ghz     0.0%
polling           0.0ms ( 0.0%)         1.60 Ghz     0.0%
C1                0.0ms ( 0.0%)         1200 Mhz     0.0%
C2                0.0ms ( 0.0%)          800 Mhz   100.0%
C3                3.3ms (95.8%)

ok, this is nearly what I am used to. Yesterday, there was C4 instead of 
C3… but new is ”polling“—what does that mean? And before the upgrade, 
the first and second P-state had the same frequency. Why is there now a 
difference of 10MHz?…

But now really the question: How can I get into C4 again? Do I have to 
check my BIOS for this? Why did I have C4 yesterday but not now?…

Hope, you can help me or give me some hints where I can get good 
information about this behaviour.

Thanks,
Arno