On Sat, 19 Apr 2014, Dainius (GreatEmerald) wrote:
> Hi,
> I have an external hard drive (well, actually a case for an internal
> one, but this may not be relevant) that connects to the PC via USB3.
> However, I've been experiencing erratic behaviour with it. So far
> there have been two issues.
>
> One is that if I boot with the cable plugged in already, then it fails
> to mount the volume (or, indeed, report that it even exists). However,
> if I either remove the cable and replug it into another USB3 socket or
> if I plug it in only after it's done booting, then everything is fine
> and I can see and mount the volume. I'll attach the dmesg errors about
> it.
>
> The other issue is rather peculiar. When I get it mounted, doing
> certain I/O tasks (I'm testing with btrfs send/receive) results in the
> device disconnecting and unmounting (the key error seems to be "xHCI
> xhci_drop_endpoint called with disabled ep ffff8801aced5d40"). When
> it's connected through a USB2 port, I also get errors ("reset
> high-speed USB device number 6 using ehci-pci"), but they don't result
> in unmounting the volume. And if I do large file copying instead of
> btrfs send/receive, then everything works fine even when connected
> through USB3. I'll also attach the error logs in question.
>
> I also tested this with a separate USB2 cable, and the results are the
> same as when I use the USB3 cable but connect it to a USB2 port.
That's to be expected. More to the point would be to test with a USB-2
cable connected to a USB-3 port.
> I'm currently using kernel 3.10.11.
You really should upgrade to 3.14. I don't know whether all the
changes to xhci-hcd have been back-ported to the stable kernels.
> Any ideas about what could be causing this behaviour with USB3?
Not much idea regarding the USB-3 problems. Under USB-2, you can try
to find out the reason for the resets by collecting a usbmon trace.
(It's probably the same as the reason for the USB-3 resets.) See the
kernel source file Documentation/usb/usbmon.txt for instructions.
Alan Stern
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