Re: [PATCH v2 2/2] usb: dwc3: gadget: Don't set IMI for no_interrupt

[Jeff Vanhoof <jdv1029@gmail.com>]

Hi Thinh,

On Mon, Oct 24, 2022 at 11:51:50PM -0500, Jeff Vanhoof wrote:
> On Mon, Oct 24, 2022 at 06:28:04PM -0700, Thinh Nguyen wrote:
> > The gadget driver may have a certain expectation of how the request
> > completion flow should be from to its configuration. Make sure the
> > controller driver respect that. That is, don't set IMI (Interrupt on
> > Missed Isoc) when usb_request->no_interrupt is set.
> > 
> > Fixes: 72246da40f37 ("usb: Introduce DesignWare USB3 DRD Driver")
> > Cc: stable@vger.kernel.org
> > Signed-off-by: Thinh Nguyen <Thinh.Nguyen@synopsys.com>
> > ---
> >  Changes in v2:
> >  - None
> > 
> >  drivers/usb/dwc3/gadget.c | 4 ++--
> >  1 file changed, 2 insertions(+), 2 deletions(-)
> > 
> > diff --git a/drivers/usb/dwc3/gadget.c b/drivers/usb/dwc3/gadget.c
> > index 230b3c660054..702bdf42ad2f 100644
> > --- a/drivers/usb/dwc3/gadget.c
> > +++ b/drivers/usb/dwc3/gadget.c
> > @@ -1292,8 +1292,8 @@ static void dwc3_prepare_one_trb(struct dwc3_ep *dep,
> >  			trb->ctrl = DWC3_TRBCTL_ISOCHRONOUS;
> >  		}
> >  
> > -		/* always enable Interrupt on Missed ISOC */
> > -		trb->ctrl |= DWC3_TRB_CTRL_ISP_IMI;
> > +		if (!req->request.no_interrupt)
> > +			trb->ctrl |= DWC3_TRB_CTRL_ISP_IMI;
> >  		break;
> >  
> >  	case USB_ENDPOINT_XFER_BULK:
> > -- 
> > 2.28.0
> >
> 
<snip>

For scatter gather, shouldn't the IMI bit be set only for the TRB associated
to the last item in the sg list?  Do we need to do something similar to what
that was done for IOC in this area?

For ex.:
+	if ((!req->request.no_interrupt && !chain) || must_interrupt)
+		trb->ctrl |= DWC3_TRB_CTRL_ISP_IMI;

BTW, Dan indicated that this seems to help resolve the crash mentioned in
[PATCH v2 1/2] of this chain.

Thanks,
Jeff