Re: Failure prints during format or mounting a usb storage device

[Paul Zimmerman <pauldzim@gmail.com>]

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On Tue, Jul 7, 2020 at 12:57 AM Gerd Hoffmann <kraxel@redhat.com> wrote:

>   Hi,
> >
> > Gerd, do you know the purpose of the 'short_not_ok' parameter to
> > usb_packet_setup()?
>
> Well, some usb host controllers have a flag in the transfer control
> blocks to indicate the host controller should stop processing requests
> in case of a short transfer.
>
> The usb core uses the flag to just to that (i.e. halt the endpoint on
> short transfers).  It is also checked when usb-host pipelines requests
> (requests queued after a short-not-ok packet can't be pipelined because
> we don't know yet whenever we should continue processing the endpoint or
> not).
>
> xhci has no such flag so the flag is never set.
>
> > The simple patch below fixes the reported problem,
> > but I don't know if it could cause some other problems for XHCI.
> > hcd-ehci, hcd-ohci, hcd-uhci all set the parameter conditionally,
> > but hcd-xhci never sets it. I don't understand the purpose of the
> > parameter myself.
> >
> > diff --git a/hw/usb/hcd-xhci.c b/hw/usb/hcd-xhci.c
> > index b330e36fe6..9fb96fdd66 100644
> > --- a/hw/usb/hcd-xhci.c
> > +++ b/hw/usb/hcd-xhci.c
> > @@ -1614,7 +1614,7 @@ static int xhci_setup_packet(XHCITransfer *xfer)
> >      xhci_xfer_create_sgl(xfer, dir == USB_TOKEN_IN); /* Also sets
> int_req */
> >      usb_packet_setup(&xfer->packet, dir, ep, xfer->streamid,
> > -                     xfer->trbs[0].addr, false, xfer->int_req);
> > +                     xfer->trbs[0].addr, dir == USB_TOKEN_IN,
> xfer->int_req);
>
> I suspect this might lead to queues being halted even though they should
> not.
>
> Why does 7ad3d51ebb8a522ffcad391c4bef281245739dde look at short-not-ok?
>

Because the patch changes dev-storage to terminate the transfer if a
short packet is received, so I figured 'short-not-ok' should affect
that behavior.

I guess instead I could add another flag that only hcd-dwc2 sets. Does
that sound OK to you?

Thanks,
Paul


> take care,
>   Gerd
>
>

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