[arch-general] usb-storage and processor C-states

JM fijam at archlinux.us
Sun Aug 22 08:57:38 EDT 2010


I have two boxes: Pentium M / i915 / ICH7 and Via C7 / CN 700 /
VT8237R. Both processors support C-states 0 through 3. Both
southbridges support USB 2.0 (ehci). Yet when I plug in an usb flash
drive into the Via C7 box the processor can no longer go into the C3
sleep state (C2 becomes the lowest possible) while the Pentium M box
does not display this behavior and still happily idles in the C3

I'd like to poke upstream about it but I need to know more. What is to
blame? Could this be a Southbridge/CPU/BIOS limitation, or is it
driver's fault? How do I debug this further?

Any help would be appreciated.


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