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

[John Stultz]

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:
> >    https://git.linaro.org/people/john.stultz/android-dev.git/commit/?h=dev/hikey960-5.1&id=dcdadaaec9db7a7b78ea9b838dd1453359a2f388
> >
> > Then dwc2 added sg support, and I ended up having to revert it to get
> > by on HiKey:
> >    https://git.linaro.org/people/john.stultz/android-dev.git/commit/?h=dev/hikey-5.1&id=6e91b4c7bd1e94bdd835263403c53e85a677b848
> >
> > (See thread here: https://lkml.org/lkml/2019/3/8/765)
>
> 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
(https://lkml.org/lkml/2019/3/8/765) 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.

thanks
-john