On Tue, Feb 28, 2023, Thinh Nguyen wrote:
> On Mon, Feb 27, 2023, Wesley Cheng wrote:
> > Previously, there was a 100uS delay inserted after issuing an end transfer
> > command for specific controller revisions. This was due to the fact that
> > there was a GUCTL2 bit field which enabled synchronous completion of the
> > end transfer command once the CMDACT bit was cleared in the DEPCMD
> > register. Since this bit does not exist for all controller revisions, add
> > the delay back in.
> >
> > An issue was seen where the USB request buffer was unmapped while the DWC3
> > controller was still accessing the TRB. However, it was confirmed that the
> > end transfer command was successfully submitted. (no end transfer timeout)
>
> Currently we only check for command active, not completion on teardown.
>
> > In situations, such as dwc3_gadget_soft_disconnect() and
> > __dwc3_gadget_ep_disable(), the dwc3_remove_request() is utilized, which
> > will issue the end transfer command, and follow up with
> > dwc3_gadget_giveback(). At least for the USB ep disable path, it is
> > required for any pending and started requests to be completed and returned
> > to the function driver in the same context of the disable call. Without
> > the GUCTL2 bit, it is not ensured that the end transfer is completed before
> > the buffers are unmapped.
> >
> > Signed-off-by: Wesley Cheng <quic_wcheng@xxxxxxxxxxx>
>
> This is expected. We're supposed to make sure the End Transfer command
> complete before accessing the request. Usually on device/endpoint
> teardown, the gadget drivers don't access the stale/incomplete requests
> with -ESHUTDOWN status. There will be problems if we do, and we haven't
> fixed that.
>
> Adding 100uS may not apply for every device, and we don't need to do
> that for every End Transfer command. Can you try this untested diff
> instead:
>
>
> diff --git a/drivers/usb/dwc3/gadget.c b/drivers/usb/dwc3/gadget.c
> index 30408bafe64e..5ae5ff4c8858 100644
> --- a/drivers/usb/dwc3/gadget.c
> +++ b/drivers/usb/dwc3/gadget.c
> @@ -1962,6 +1962,34 @@ static int __dwc3_gadget_get_frame(struct dwc3 *dwc)
> return DWC3_DSTS_SOFFN(reg);
> }
>
> +static int dwc3_poll_ep_completion(struct dwc3_ep *dep)
> +{
> + if (!list_empty(&dep->started_list)) {
> + struct dwc3_request *req;
> + int timeout = 500;
> +
> + req = next_request(&dep->started_list);
> + while(--timeout) {
> + /*
> + * Note: don't check the last enqueued TRB in case
> + * of short transfer. Check first TRB of a started
> + * request instead.
> + */
> + if (!(req->trb->ctrl & DWC3_TRB_CTRL_HWO))
> + break;
> +
> + udelay(2);
> + }
> + if (!timeout) {
> + dev_warn(dep->dwc->dev,
> + "%s is still in-progress\n", dep->name);
> + return -ETIMEDOUT;
> + }
> + }
> +
> + return 0;
> +}
> +
> /**
> * __dwc3_stop_active_transfer - stop the current active transfer
> * @dep: isoc endpoint
> @@ -2003,10 +2031,12 @@ static int __dwc3_stop_active_transfer(struct dwc3_ep *dep, bool force, bool int
> WARN_ON_ONCE(ret);
> dep->resource_index = 0;
>
> - if (!interrupt)
> + if (!interrupt) {
> + ret = dwc3_poll_ep_completion(dep);
Actually, the TRB status may not get updated, so this may not work,
instead of polling, may need to add the delay here instead.
> dep->flags &= ~DWC3_EP_TRANSFER_STARTED;
> - else if (!ret)
> + } else if (!ret) {
> dep->flags |= DWC3_EP_END_TRANSFER_PENDING;
> + }
>
> dep->flags &= ~DWC3_EP_DELAY_STOP;
> return ret;
>
>
Thanks,
Thinh
