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    Subject[ 37/55] usb: gadget: fsl_udc_core: dTDs next dtd pointer need to be updated once written
    3.0-stable review patch.  If anyone has any objections, please let me know.


    From: Peter Chen <>

    commit 4d0947dec4db1224354e2f6f00ae22ce38e62a43 upstream.

    dTD's next dtd pointer need to be updated once CPU writes it, or this
    request may not be handled by controller, then host will get NAK from
    device forever.

    This problem occurs when there is a request is handling, we need to add
    a new request to dTD list, if this new request is added before the current
    one is finished, the new request is intended to added as next dtd pointer
    at current dTD, but without wmb(), the dTD's next dtd pointer may not be
    updated when the controller reads it. In that case, the controller will
    still get Terminate Bit is 1 at dTD's next dtd pointer, that means there is
    no next request, then this new request is missed by controller.

    Signed-off-by: Peter Chen <>
    Acked-by: Li Yang <>
    Signed-off-by: Felipe Balbi <>
    Signed-off-by: Greg Kroah-Hartman <>

    drivers/usb/gadget/fsl_udc_core.c | 2 ++
    1 file changed, 2 insertions(+)

    --- a/drivers/usb/gadget/fsl_udc_core.c
    +++ b/drivers/usb/gadget/fsl_udc_core.c
    @@ -717,6 +717,8 @@ static void fsl_queue_td(struct fsl_ep *
    lastreq = list_entry(ep->queue.prev, struct fsl_req, queue);
    lastreq->tail->next_td_ptr =
    cpu_to_hc32(req->head->td_dma & DTD_ADDR_MASK);
    + /* Ensure dTD's next dtd pointer to be updated */
    + wmb();
    /* Read prime bit, if 1 goto done */
    if (fsl_readl(&dr_regs->endpointprime) & bitmask)
    goto out;

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      Last update: 2012-05-27 03:41    [W:0.033 / U:89.788 seconds]
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