On Wed, 22 Apr 2009, Daniel Smoczyk wrote: > On Wed, Apr 22, 2009 at 4:51 PM, Alan Stern <stern@xxxxxxxxxxxxxxxxxxx> wrote: > > > In fact the bug report says that 2.6.27 worked okay. > > Not true, didn't tested 2.6.27 - there wasn't such one in debian repos. I'm going by the data in http://bugzilla.kernel.org/attachment.cgi?id=19780 which is attached to bug #12391. > > However the changes to uhci-hcd between 2.6.27 and 2.6.28 are quite > > minimal. I can't see how any of them could have had this effect. It > > must be due to a change somewhere else in the kernel. > > Could You please check 26 <-> 27? In my opinion uhci-hcd was able to > autosuspend while mouse wasn't used in 2.6.26 and it isn't able to do > autosuspend now ( C3 works ok after "rmmod uhci-hcd") There was essentially no change to uhci-hcd between 2.6.26 and 2.6.27 (a static array definition got an added "const", that's all). uhci-hcd has been able to autosuspend all along, provided no active devices (like a mouse) are attached. If you unplug the mouse and any other USB devices attached to the UHCI controller under 2.6.28, it should autosuspend. But that's not what you were concerned about. Your original bug description said that the CPU wasn't going into C3 when the mouse _was_ attached. > This situation is very similar to using usb memory stick non-stop, > when watching move for eg. then processor also never goes below C2. Whenever a USB device is attached and not suspended, the host controller has to do DMA. Older processors are not able to enter C3 while DMA is active. So it would be good to verify whether your CPU is actually capable of doing it. Alan Stern -- To unsubscribe from this list: send the line "unsubscribe linux-usb" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
