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

[Andrzej Pietrasiewicz]

Hi John,

+= Marek

W dniu 08.05.2019 oÂ04:18, 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)
>
> And now I've reproduced the same issue (with the same dwc3 workaround)
> on the already upstream code for Dragonboard 845c.
>
> Fei Yang has also reached out and mentioned he was seeing similar
> problems with the f_fs sg support.
>
> Andrzej: Do you have any ideas or suggestions on this? I'm happy to
> test or run any debug patches, if it would help narrow the issue down.

There is a patch:

https://www.spinics.net/lists/linux-usb/msg178536.html
https://www.spinics.net/lists/linux-usb/msg179653.html

which fixes a subtle bug, but hasn't been applied yet.

Can you please try it?

> If not, should we consider reverting the f_fs sg support?

Andrzej