USB: EHCI: fix regression during bus resume
authorAlan Stern <stern@rowland.harvard.edu>
Fri, 15 Mar 2013 18:40:26 +0000 (14:40 -0400)
committerGreg Kroah-Hartman <gregkh@linuxfoundation.org>
Thu, 28 Mar 2013 19:18:02 +0000 (12:18 -0700)
commit77bc8f4f1038463a3bc7889606f0d7334bda1ad8
tree516ed115de9efa87333562041ab150f6cc693f25
parent5557c6706441e7ad797b8b5c95579a9a1146502b
USB: EHCI: fix regression during bus resume

commit 2a40f324541ee61c22146214349c2ce9f5c30bcf upstream.

This patch (as1663) fixes a regression caused by commit
6e0c3339a6f19d748f16091d0a05adeb1e1f822b (USB: EHCI: unlink one async
QH at a time).  In order to avoid keeping multiple QHs in an unusable
intermediate state, that commit changed unlink_empty_async() so that
it unlinks only one empty QH at a time.

However, when the EHCI root hub is suspended, _all_ async QHs need to
be unlinked.  ehci_bus_suspend() used to do this by calling
unlink_empty_async(), but now this only unlinks one of the QHs, not
all of them.

The symptom is that when the root hub is resumed, USB communications
don't work for some period of time.  This is because ehci-hcd doesn't
realize it needs to restart the async schedule; it assumes that
because some QHs are already on the schedule, the schedule must be
running.

The easiest way to fix the problem is add a new function that unlinks
all the async QHs when the root hub is suspended.

This patch should be applied to all kernels that have the 6e0c3339a6f1
commit.

Signed-off-by: Alan Stern <stern@rowland.harvard.edu>
Reported-and-tested-by: Adrian Bassett <adrian.bassett@hotmail.co.uk>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
drivers/usb/host/ehci-hcd.c
drivers/usb/host/ehci-hub.c
drivers/usb/host/ehci-q.c