Re: [PATCH v4] usb: dwc3: gadget: Add 1ms delay after end transfer command without IOC

[Wesley Cheng]

Hi Thinh,

On 3/1/2023 2:44 PM, Thinh Nguyen wrote:
> On Tue, Feb 28, 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
>
> Can we also note here that we rely on End Transfer command completion
> interrupt on newer versions.
>
> > the delay back in, and increase the duration to 1ms for the controller to
> > complete the command.
> >
> > 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)
> > 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.
>
> I think this also needs a Fixes tag.
>
> Everything else looks good to me.

Thanks for the reviews, Thinh.  Will fix the above and resubmit.

Thanks
Wesley Cheng