[Openchrome-users] OpenChrome driver and power saving

[Andrey Melentyev]

A few days ago Intel released PowerTOP software: "PowerTOP is a Linux tool 
that finds the software component(s) that make your laptop use more power 
than necessary while it is idle." http://www.linuxpowertop.org/

I'm running a laptop with Unichrome Pro IGP on VIA VN800 and I've made some 
simple tests with PowerTOP. The results are not optimistic mainly because of 
X server. When X is running with OpenChrome driver and nothing happens on the 
screen, "<interrupt> via at pci:0000:01:00.0" causes 60-70% of wakeups (absolute 
value is 60 per second). We can see a very similar behaivor of i915 graphics 
driver: http://www.linuxpowertop.org/powertop.php - Intel guys say that there 
is a bug (See section "Top causes for wakeups" on this page and 
http://www.linuxpowertop.org/known.php#intelgfx for more info).

When X server is not running, powertop doesn't report any wakeups and 'libata' 
takes the top position in the list. So I suggested that there can be a 
similar bug in OpenChrome driver. Futhermore it is very suspicious that the 
number of caused wakeups is equally 60. It reminds me of my refresh rate 
which is 60Hz. = 60 1 / second. And PowerTOP's site says: "The Intel graphics 
driver used to have a bug where it set up the hardware to generate an 
interrupt (called VBLANK) each time the screen finished refreshing (typically 
at 60Hz or 72Hz)."

PS: a screenshot with powertop running on my system is attached

Best regards, 
Andrew.
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