On Thu, Jul 18, 2019 at 6:12 PM Thinh Nguyen Thinh.Nguyen@synopsys.com wrote:

fei.yang@intel.com wrote:

...

From: Fei Yang fei.yang@intel.com

If scatter-gather operation is allowed, a large USB request is split into multiple TRBs. These TRBs are chained up by setting DWC3_TRB_CTRL_CHN bit except the last one which has DWC3_TRB_CTRL_IOC bit set instead. Since only the last TRB has IOC set for the whole USB request, the dwc3_gadget_ep_reclaim_trb_sg() gets called only once after the last TRB completes and all the TRBs allocated for this request are supposed to be reclaimed. However that is not what the current code does.

dwc3_gadget_ep_reclaim_trb_sg() is trying to reclaim all the TRBs in the following for-loop, for_each_sg(sg, s, pending, i) { trb = &dep->trb_pool[dep->trb_dequeue];

            if (trb->ctrl & DWC3_TRB_CTRL_HWO)
                    break;

            req->sg = sg_next(s);
            req->num_pending_sgs--;

            ret = dwc3_gadget_ep_reclaim_completed_trb(dep, req,
                            trb, event, status, chain);
            if (ret)
                    break;
    }

but since the interrupt comes only after the last TRB completes, the event->status has DEPEVT_STATUS_IOC bit set, so that the for-loop ends for the first TRB due to dwc3_gadget_ep_reclaim_completed_trb() returns 1. if (event->status & DEPEVT_STATUS_IOC) return 1;

This patch addresses the issue by checking each TRB in function dwc3_gadget_ep_reclaim_trb_sg() and maing sure the chained ones are properly reclaimed. dwc3_gadget_ep_reclaim_completed_trb() will return 1 Only for the last TRB.

Signed-off-by: Fei Yang fei.yang@intel.com Cc: stable stable@vger.kernel.org

---

v2: Better solution is to reclaim chained TRBs in dwc3_gadget_ep_reclaim_trb_sg() and leave the last TRB to the dwc3_gadget_ep_reclaim_completed_trb(). v3: Checking DWC3_TRB_CTRL_CHN bit for each TRB instead, and making sure that dwc3_gadget_ep_reclaim_completed_trb() returns 1 only for the last TRB.

---

drivers/usb/dwc3/gadget.c | 11 ++++++++--- 1 file changed, 8 insertions(+), 3 deletions(-)

diff --git a/drivers/usb/dwc3/gadget.c b/drivers/usb/dwc3/gadget.c index 173f532..88eed49 100644 --- a/drivers/usb/dwc3/gadget.c +++ b/drivers/usb/dwc3/gadget.c @@ -2394,7 +2394,7 @@ static int dwc3_gadget_ep_reclaim_completed_trb(struct dwc3_ep *dep, if (event->status & DEPEVT_STATUS_SHORT && !chain) return 1;

• if (event->status & DEPEVT_STATUS_IOC)
  

• if (event->status & DEPEVT_STATUS_IOC && !chain)
          return 1;
  
  return 0;
  

@@ -2404,11 +2404,12 @@ static int dwc3_gadget_ep_reclaim_trb_sg(struct dwc3_ep *dep, struct dwc3_request *req, const struct dwc3_event_depevt *event, int status) {

• struct dwc3_trb *trb = &dep->trb_pool[dep->trb_dequeue];
  

• struct dwc3_trb *trb;
  struct scatterlist *sg = req->sg;
  struct scatterlist *s;
  unsigned int pending = req->num_pending_sgs;
  unsigned int i;
  

• int chain = false;
  int ret = 0;
  
  for_each_sg(sg, s, pending, i) {
  

@@ -2419,9 +2420,13 @@ static int dwc3_gadget_ep_reclaim_trb_sg(struct dwc3_ep *dep,

          req->sg = sg_next(s);
          req->num_pending_sgs--;

•         if (trb->ctrl & DWC3_TRB_CTRL_CHN)
  

•                 chain = true;
  

•         else
  

•                 chain = false;
  
          ret = dwc3_gadget_ep_reclaim_completed_trb(dep, req,
  

•                         trb, event, status, true);
  

•                         trb, event, status, chain);
          if (ret)
                  break;
  }
  

There was already a fix a long time ago by Anurag. But it never made it to the kernel mainline. You can check this out: https://patchwork.kernel.org/patch/10640137/

So, back from a vacation last week, and just validated that both Fei's patch and a forward ported version of this patch Thinh pointed out both seem to resolve the usb stalls I've been seeing sinice 4.20 w/ dwc3 hardware on both hikey960 and dragonboard 845c.

Felipe: Does Anurag's patch above make more sense as a proper fix?

thanks -john

From: Anurag Kumar Vulisha anurag.kumar.vulisha@xilinx.com

The present code in dwc3_gadget_ep_reclaim_completed_trb() will check for IOC/LST bit in the event->status and returns if IOC/LST bit is set. This logic doesn't work if multiple TRBs are queued per request and the IOC/LST bit is set on the last TRB of that request. Consider an example where a queued request has multiple queued TRBs and IOC/LST bit is set only for the last TRB. In this case, the Core generates XferComplete/XferInProgress events only for the last TRB (since IOC/LST are set only for the last TRB). As per the logic in dwc3_gadget_ep_reclaim_completed_trb() event->status is checked for IOC/LST bit and returns on the first TRB. This makes the remaining TRBs left unhandled. To aviod this, changed the code to check for IOC/LST bits in both event->status & TRB->ctrl. This patch does the same.

At a practical level, this patch resolves USB transfer stalls seen with adb on dwc3 based Android devices after functionfs gadget added scatter-gather support around v4.20.

Cc: Felipe Balbi felipe.balbi@linux.intel.com Cc: Fei Yang fei.yang@intel.com Cc: Thinh Nguyen thinhn@synopsys.com Cc: Tejas Joglekar tejas.joglekar@synopsys.com Cc: Andrzej Pietrasiewicz andrzej.p@collabora.com Cc: Greg KH gregkh@linuxfoundation.org Cc: Linux USB List linux-usb@vger.kernel.org Cc: stable stable@vger.kernel.org Tested-By: Tejas Joglekar tejas.joglekar@synopsys.com Reviewed-by: Thinh Nguyen thinhn@synopsys.com Signed-off-by: Anurag Kumar Vulisha anurag.kumar.vulisha@xilinx.com [jstultz: forward ported to mainline, added note to commit log] Signed-off-by: John Stultz john.stultz@linaro.org --- Just wanted to send this out so we're all looking at the same thing. Not sure if its correct, but it seems to solve the adb stalls I've been seeing for awhile.

thanks -john

drivers/usb/dwc3/gadget.c | 7 ++++++- 1 file changed, 6 insertions(+), 1 deletion(-)

diff --git a/drivers/usb/dwc3/gadget.c b/drivers/usb/dwc3/gadget.c index c9cecb3a9670..1d9701dde69b 100644 --- a/drivers/usb/dwc3/gadget.c +++ b/drivers/usb/dwc3/gadget.c @@ -2394,7 +2394,12 @@ static int dwc3_gadget_ep_reclaim_completed_trb(struct dwc3_ep *dep, if (event->status & DEPEVT_STATUS_SHORT && !chain) return 1;

- if (event->status & DEPEVT_STATUS_IOC) + if ((event->status & DEPEVT_STATUS_IOC) && + (trb->ctrl & DWC3_TRB_CTRL_IOC)) + return 1; + + if ((event->status & DEPEVT_STATUS_LST) && + (trb->ctrl & DWC3_TRB_CTRL_LST)) return 1;

return 0;