git.ipfire.org Git - thirdparty/kernel/stable-queue.git/blob

   1 From db89960e50f45274c07dc60926b5a49489b8a7a0 Mon Sep 17 00:00:00 2001
   2 From: Michael Grzeschik <m.grzeschik@pengutronix.de>
   3 Date: Wed, 12 Sep 2012 14:58:04 +0300
   4 Subject: usb: chipidea: udc: don't stall endpoint if request list is empty in isr_tr_complete_low
   5
   6 From: Michael Grzeschik <m.grzeschik@pengutronix.de>
   7
   8 commit db89960e50f45274c07dc60926b5a49489b8a7a0 upstream.
   9
  10 When attaching an imx28 or imx53 in USB gadget mode to a Windows host and
  11 starting a rndis connection we see this message every 4-10 seconds:
  12
  13     g_ether gadget: high speed config #2: RNDIS
  14
  15 Analysis shows that each time this message is printed, the rndis connection is
  16 re-establish due to a reset because of a stalled endpoint (ep 0, dir 1). The
  17 endpoint is stalled because the reqeust complete bit on that endpoint is set,
  18 but in isr_tr_complete_low() the endpoint request list (mEp->qh.queue) is
  19 empty.
  20
  21 This patch removed this check, because the code doesn't take the following
  22 situation into account:
  23
  24 The loop over all endpoints in isr_tr_complete_handler() will call ep_nuke() on
  25 both ep0/dir0 and ep/dir1 in the first loop. Pending reqeusts will be flushed
  26 and completed here. There seems to be a race condition, the request is nuked,
  27 but the request complete bit will be set, too. The subsequent check (in
  28 ep0/dir1's loop cycle) for endpoint request list (mEp->qh.queue) empty will
  29 fail.
  30
  31 Both other mainline chipidea drivers (mv_udc_core.c and fsl_udc_core.c) don't
  32 have this check.
  33
  34 Signed-off-by: Michael Grzeschik <m.grzeschik@pengutronix.de>
  35 Signed-off-by: Marc Kleine-Budde <mkl@pengutronix.de>
  36 Signed-off-by: Alexander Shishkin <alexander.shishkin@linux.intel.com>
  37 Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
  38
  39 ---
  40  drivers/usb/chipidea/udc.c |    5 +----
  41  1 file changed, 1 insertion(+), 4 deletions(-)
  42
  43 --- a/drivers/usb/chipidea/udc.c
  44 +++ b/drivers/usb/chipidea/udc.c
  45 @@ -771,10 +771,7 @@ __acquires(mEp->lock)
  46  {
  47         struct ci13xxx_req *mReq, *mReqTemp;
  48         struct ci13xxx_ep *mEpTemp = mEp;
  49 -       int uninitialized_var(retval);
  50 -
  51 -       if (list_empty(&mEp->qh.queue))
  52 -               return -EINVAL;
  53 +       int retval = 0;
  54
  55         list_for_each_entry_safe(mReq, mReqTemp, &mEp->qh.queue,
  56                         queue) {