From 4d0947dec4db1224354e2f6f00ae22ce38e62a43 Mon Sep 17 00:00:00 2001 From: Peter Chen Date: Sun, 1 Apr 2012 15:17:16 +0800 Subject: [PATCH] usb: gadget: fsl_udc_core: dTD's next dtd pointer need to be updated once written 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: Signed-off-by: Peter Chen Acked-by: Li Yang Signed-off-by: Felipe Balbi --- drivers/usb/gadget/fsl_udc_core.c | 2 ++ 1 file changed, 2 insertions(+) diff --git a/drivers/usb/gadget/fsl_udc_core.c b/drivers/usb/gadget/fsl_udc_core.c index 8f6fc7046f8c..5a52d4279050 100644 --- a/drivers/usb/gadget/fsl_udc_core.c +++ b/drivers/usb/gadget/fsl_udc_core.c @@ -735,6 +735,8 @@ 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; -- 2.20.1