On Mon, May 20, 2019 at 9:23 AM Yang, Fei <fei.yang@xxxxxxxxx> wrote: > > >> One question that comes to my mind is this: Does the USB transmission > >> stall (e.g. endpoint stall) or not? In other words, is adb connection > >> broken because USB stops transmitting anything, or because the data is > >> transmitted but its integrity is broken during transmission and that > >> causes adb/adbd confusion which results in stopping their operation? > >> Does anything keep happening on FunctionFS when adb connection is > >> broken? > > > >Any discoveries about the problem? > > In my debugging, I'm seeing a lot of requests queued up through ffs_epfile_io (returning -EIOCBQUEUED), but > only a few of them came back through ffs_epfile_async_io_complete -> ffs_user_copy_worker. > I don’t think there is a USB transmission stall though, because if I manually disable io_data->use_sg, everything > goes back to normal. So it looks more likely to be a buffer handling problem in the DWC3 driver. Yea, I also did reconfirm that reverting 772a7a724f6, or setting gadget->sg_supported to false makes the isssue go away. And after spending a bunch of time trying to trace through the code last week, in particular the sg_supported checks, but I'm not seeing anything that is standing out with the f_fs logic. I'd start to agree it might be a buffer handling problem in dwc3, but it feels odd that I'm also seeing this w/ dwc2 hardware as well. Maybe the same bug was copied into both drivers? I'll try to dig a little on that theory today. thanks -john
