Re: [REGRESSION] usb: gadget: f_fs: Allow scatter-gather buffers

From: John Stultz
Date: Thu May 09 2019 - 14:26:41 EST

On Thu, May 9, 2019 at 7:02 AM Andrzej Pietrasiewicz
<andrzej.p@xxxxxxxxxxxxx> wrote:
> Hi John,
> W dniu 08.05.2019 o 04:18, John Stultz pisze:
> > Since commit 772a7a724f69 ("usb: gadget: f_fs: Allow scatter-gather
> > buffers"), I've been seeing trouble with adb transfers in Android on
> > HiKey960, HiKey and now Dragonboard 845c.
> >
> > Sometimes things crash, but often the transfers just stop w/o any
> > obvious error messages.
> >
> > Initially I thought it was an issue with the HiKey960 dwc3 usb patches
> > being upstreamed, and was using the following hack workaround:
> >
> >
> > Then dwc2 added sg support, and I ended up having to revert it to get
> > by on HiKey:
> >
> >
> > (See thread here:
> So the thread says there are problems at boot, but here you mention about
> adb transfers, which must obviously be happening after the board has booted.
> Do you experience problems at boot or not?
> If a crash happens, what is in the log?

So, yes. Sorry, I am maybe muddling two issues (though they both seem
to be tied to f_fs sg). On dwc2, with the current code, we often (but
not always) crash as soon as adb starts up in the boot process. Thus
I'm running with a revert of "usb: dwc2: gadget: Add scatter-gather
mode" to get by.

As for example crashes, there is a crash in the thread linked above
( and also the one I sent yesterday
when testing with your zlp patch. Let me know if you're looking for
something more specific.

One thing I didn't do, but I should is run w/ the zlp + your
memset/kzalloc patch. See if that helps get dwc2 further along at
least. I'll test that shortly here and get back to you.