tree 27889eb4e928866b5ea6496dbcdd9abc1c23e9e3
parent cdb4dd15e62eb984d9461b520d15d00ff2b88d9d
author Alan Stern <stern@rowland.harvard.edu> 1405715172 -0400
committer Greg Kroah-Hartman <gregkh@linuxfoundation.org> 1405726447 -0700

USB: OHCI: add I/O watchdog for orphan TDs

Some OHCI controllers have a bug: They fail to add completed TDs to
the done queue.  Examining this queue is the only method ohci-hcd has
for telling when a transfer is complete; failure to add a TD can
result in an URB that never completes and cannot be unlinked.

This patch adds a watchdog routine to ohci-hcd.  The routine
periodically scans the active ED and TD lists, looking for TDs which
are finished but not on the done queue.  When one is found, and it is
certain that the controller hardware will never add the TD to the done
queue, the watchdog routine manually puts the TD on the done list so
that it can be handled normally.

The watchdog routine also checks for a condition indicating the
controller has died.  If the done queue is non-empty but the
HccaDoneHead pointer hasn't been updated for a few hundred
milliseconds, we assume the controller will never update it and
therefore is dead.

Signed-off-by: Alan Stern <stern@rowland.harvard.edu>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>