On 18/09/17 12:27, Bjørn Mork wrote: > Andreas Böhler <news@xxxxxxxxxxx> writes: > >> I recently bought a Thinkpad T470 notebook and added the Fibocom >> L831-EAU WWAN card. It's mbim-based, but unfortunately I can't get it >> to work correctly. In fact I'm experiencing similar issues to Patrick >> Chilton, who reported this behaviour a few months ago also on this >> list: https://www.spinics.net/lists/linux-usb/msg158286.html >> >> After a new boot, the card works for me for a few minutes, then all >> transfers stall. Finally, I receive the infamous 'cdc_mbim 1-6:1.0: >> nonzero urb status received: -EPIPE' message in my system log. >> >> I also tried to disable MBIM by adding an option to modprobe. During >> connect, pppd then just hangs up (again similar to what Patrick >> Chilton experienced). >> >> I'm on Arch Linux and Kernel 4.12.13, I tried with and without >> NetworkManager/ModemManager. >> >> Any ideas how I might be able to debug this? > > Are you able to test the attached patch? It should apply cleanly to any > of the 4.9, 4.12 and 4.13 stable trees. yes, of course! > Let me just admit that this is a long shot. I don't actually understand > what happens here. But I believe the problem started appearing with > v4.9, which had two patches touching this part of the driver in > suspicious ways. One of those patches have already been reverted due to > other issues. But the second is still present. And I can't see > anything else which could possibly explain the problems. > > If you can test this patch, then we can either confirm or refute this > theory. Unfortunately, it doesn't change anything. I applied the patch, recompiled the kernel (it updated to 4.13.2 at the same time), rebooted and upon connecting, I can see the 'cdc_mbim 1-6:1.0: nonzero urb status received: -EPIPE' message again. What makes it work for this session only is the following (also works without your patch, though): * connect to /dev/ttyACM0 using a terminal emulator (PuTTY in my case) * send AT+CFUN=15 to reset the modem Then, the device re-appears as /dev/cdc-wdm1 (instead of /dev/cdc-wdm0) and connecting to the web is possible. If I then disable and re-enable the modem (in this case, using NetworkManager/ModemManager), the nonzero urb status message reappears. I can make it work again by resetting the modem a second time (and stopping ModemManager before the reset, starting it again after the reset). I can also provide you with Wireshark USB traces, if that helps? Andreas -- To unsubscribe from this list: send the line "unsubscribe linux-usb" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
