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. CC: <stable@xxxxxxxxxxxxxxx> Signed-off-by: Peter Chen <peter.chen@xxxxxxxxxxxxx> --- drivers/usb/gadget/fsl_udc_core.c | 2 ++ 1 files changed, 2 insertions(+), 0 deletions(-) diff --git a/drivers/usb/gadget/fsl_udc_core.c b/drivers/usb/gadget/fsl_udc_core.c index b30e21f..863dc9c 100644 --- a/drivers/usb/gadget/fsl_udc_core.c +++ b/drivers/usb/gadget/fsl_udc_core.c @@ -737,6 +737,8 @@ static void fsl_queue_td(struct fsl_ep *ep, struct fsl_req *req) 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) return; -- 1.7.0.4 -- To unsubscribe from this list: send the line "unsubscribe linux-usb" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
