On Tue, Jan 28, 2020 at 5:23 AM Felipe Balbi balbi@kernel.org wrote:
Hi,
John Stultz john.stultz@linaro.org writes:
From: Anurag Kumar Vulisha anurag.kumar.vulisha@xilinx.com
The current 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 leaves the remaining TRBs left unhandled.
Similarly, if the gadget function enqueues an unaligned request with sglist already in it, it should fail the same way, since we will append another TRB to something that already uses more than one TRB.
To aviod this, this patch changes the code to check for IOC/LST bits in TRB->ctrl instead.
At a practical level, this patch resolves USB transfer stalls seen with adb on dwc3 based HiKey960 after functionfs gadget added scatter-gather support around v4.20.
Cc: Felipe Balbi balbi@kernel.org Cc: Yang Fei 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: Jack Pham jackp@codeaurora.org Cc: Todd Kjos tkjos@google.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, reworded commit log, reworked to only check trb->ctrl as suggested by Felipe] Signed-off-by: John Stultz john.stultz@linaro.org
v2:
- Rework to only check trb->ctrl as suggested by Felipe
- Reword the commit message to include more of Felipe's assessment
drivers/usb/dwc3/gadget.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-)
diff --git a/drivers/usb/dwc3/gadget.c b/drivers/usb/dwc3/gadget.c index 154f3f3e8cff..9a085eee1ae3 100644 --- a/drivers/usb/dwc3/gadget.c +++ b/drivers/usb/dwc3/gadget.c @@ -2420,7 +2420,8 @@ 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 ((trb->ctrl & DWC3_TRB_CTRL_IOC) ||(trb->ctrl & DWC3_TRB_CTRL_LST))why the LST bit here? It wasn't there before. In fact, we never set LST in dwc3 anymore :-)
So, it was in the patch before, just on separate lines: https://lore.kernel.org/lkml/20200122222645.38805-2-john.stultz@linaro.org/
- 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;
So I just merged the two checks into one line. But I'm ok to drop the CTRL_LST check if that really isn't used. Let me know and I'll rework and resend.
thanks -john