Bug#751408: linux-3.2: xhci_hcd: "ERR: no room for command on command ring"
On some laptops such as HP's ZBook 15 that only have USB 3 ports, I
can reproducibly make the kernel ignore usb devices, in which case
syslog reads as follows:
ERROR no room on ep ring
ERR: No room for command on command ring
device not accepting address 5, error -12
couldn't allocate port 6 usb_device
So far I have reproduced it by plugging a USB 2.0 device on any of the
ports, by doing it several times (plugging & unplugging) the kernel
reaches the state where plugging again any device leads to the above
Searching for the error message on $subject it shows several reports
of the same problem.
This problem can no longer be reproduced with a kernel backported
So, searching a bit on the git log leads to the following commits:
"xhci: Reset reserved command ring TRBs on cleanup. " - likely to fix
the no room for command bug
"xHCI: add aborting command ring function" - unlikely to be it, but
maybe a fix for other bugs
"xHCI: dynamic ring expansion" - likely to fix other bugs, and maybe
help on this one
I intend to test those, but sending the report in advance.
Raphael Geissert - Debian Developer
www.debian.org - get.debian.net