Sascha Heid wrote: > Hi List! > > Is there any way to figure out what is causing the CPU to stay in C2? > > I currently have this happening for 2 reasons: > > - uhci_hcd is loaded. I dont think that usb autosuspension is working > at all but nobody seems to care. I guess i should install a vanilla > kernel so that i can annoy the kernel mailing-list directly. Currently > since 2.6.24 from Ubuntu Hardy there is no way for both my cores to go > into C3 unless i unload uhci_hcd myself. > > - sometimes for an totally unknown reason and only after longer > uptimes one core is suddenly stuck in C2 as well and i have no idea > why. > > What are your experiences with usb-autosuspension? > > Regards, > Sascha > I have uhci loaded on 2.6.24.4, configured starting from the Ubuntu 2.6.22 configuration. My EEE PC spends most of it's idle time in C3 - even when I have a USB keyboard plugged in.
I'm still not very clear about USB autosuspend. IIRC, uhci is supposed to necessarily stop the CPU entering C3 because the hardware requires constant DMA activity, and ehci doesn't have this same problem. I have ehci loaded as well as uhci, but if I remove uhci altogether then the USB keyboard stops working, so it is actually using uhci. I need to check my notes on this! I did once play with forcing my USB keyboard to autosuspend. I could suspend it manually and it would resumed fine, but I couldn't get it to autosuspend. The last time I looked for information I came to the conclusion that autosuspend of input devices was not yet supported. People were thinking about enabling it - on the condition that all the keyboard LEDs are already off - because the suspend will turn the LEDs off and it would be very confusing. Alan _______________________________________________ Discuss mailing list [email protected] http://mail.lesswatts.org/mailman/listinfo/discuss
