1. 11 May, 2011 1 commit
    • Sarah Sharp's avatar
      xhci: Fix bug in control transfer cancellation. · 3abeca99
      Sarah Sharp authored
      When the xHCI driver attempts to cancel a transfer, it issues a Stop
      Endpoint command and waits for the host controller to indicate which TRB
      it was in the middle of processing.  The host will put an event TRB with
      completion code COMP_STOP on the event ring if it stops on a control
      transfer TRB (or other types of transfer TRBs).  The ring handling code
      is supposed to set ep->stopped_trb to the TRB that the host stopped on
      when this happens.
      
      Unfortunately, there is a long-standing bug in the control transfer
      completion code.  It doesn't actually check to see if COMP_STOP is set
      before attempting to process the transfer based on which part of the
      control TD completed.  So when we get an event on the data phase of the
      control TRB with COMP_STOP set, it thinks it's a normal completion of
      the transfer and doesn't set ep->stopped_td or ep->stopped_trb.
      
      When the ring handling code goes on to process the completion of the Stop
      Endpoint command, it sees that ep->stopped_trb is not a part of the TD
      it's trying to cancel.  It thinks the hardware has its enqueue pointer
      somewhere further up in the ring, and thinks it's safe to turn the control
      TRBs into no-op TRBs.  Since the hardware was in the middle of the control
      TRBs to be cancelled, the proper software behavior is to issue a Set TR
      dequeue pointer command.
      
      It turns out that the NEC host controllers can handle active TRBs being
      set to no-op TRBs after a stop endpoint command, but other host
      controllers have issues with this out-of-spec software behavior.  Fix this
      behavior.
      
      This patch should be backported to kernels as far back as 2.6.31, but it
      may be a bit challenging, since process_ctrl_td() was introduced in some
      refactoring done in 2.6.36, and some endian-safe patches added in 2.6.40
      that touch the same lines.
      Signed-off-by: default avatarSarah Sharp <sarah.a.sharp@linux.intel.com>
      Cc: Dmitry Torokhov <dmitry.torokhov@gmail.com>
      Cc: stable@kernel.org
      3abeca99
  2. 10 May, 2011 14 commits
  3. 09 May, 2011 25 commits