On Wed, 1 Apr 2009, Andrew Morton wrote: > > http://bugzilla.kernel.org/show_bug.cgi?id=12996 > > > > Summary: Fall back to uhci if ehci is faulty > > I've got a laptop with faulty USB controller, that claims to work as USB 2.0 > > device but it manages only USB 1.1 operation. When I plug a mouse to one USB > > port, everything is OK. When I plug in some flash disk, the only result I get > > is flood of error lines in dmesg (see attachment: correctly recognized mouse in > > first few lines and flash disk errors in the rest). There is a workaround: to > > remove and blacklist module ehci_hcd, but it doesn't work if ehci_hcd module is > > compiled into kernel. This is exactly what Ubuntu folks did in beta of 9.04, > > from which I'm writing, so I can't show what is in dmesg when I remove and > > blaclist ehci_hcd... > > > > FYI, Windows XP on the same computer show "This device could perform" better > > message and use it in USB 1.1 mode automatically. It's not entirely clear what you are asking about. Do you want to know how to avoid using ehci-hcd without changing the Ubuntu kernel? That's easy enough; just do: echo -n 0000:00:1d.7 >/sys/bus/pci/drivers/ehci_hcd/unbind Do you want to know why Linux doesn't automatically fall back to UHCI? It depends on the kind of errors you're getting, and I can't tell from the information provided in the bug report. At a minimum I would need to see a usbmon trace showing what goes wrong with EHCI. Most likely it appears to the kernel as though the flash device is faulty, not the EHCI controller. 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
