This is not a NetworkManager problem. It is also reported by me in https://bugs.launchpad.net/ubuntu/+source/linux/+bug/1950385 and it is probably kernel bug. The problem is described by ModemManager's developer in our discussion: https://gitlab.freedesktop.org/mobile-broadband/ModemManager/-/issues/463#note_1157289 as a broken USB communication. According to diagnosis from kernel 5.1x the qmi_wwan module resets modem firmware in endless loop: https://gitlab.freedesktop.org/mobile-broadband/ModemManager/-/issues/463#note_1157919 although it was worked flawlessly earlier in kernel 5.8.x
The workaround is to use udev script for a modem to switch it to the MBIM mode which works ok under ModemManager & NetworkManager. Tested on kernels 5.8, 5,11, 5.13. Place the attached config file in: /etc/udev/rules.d instead of any old one. It uses usb_modeswitch to do the "magic" correctly. ** Bug watch added: gitlab.freedesktop.org/mobile-broadband/ModemManager/-/issues #463 https://gitlab.freedesktop.org/mobile-broadband/ModemManager/-/issues/463 ** Attachment added: "Udev script for switching modem" https://bugs.launchpad.net/ubuntu/+source/network-manager/+bug/1574582/+attachment/5541060/+files/99-hp-lt4120.rules -- You received this bug notification because you are a member of Ubuntu Bugs, which is subscribed to Ubuntu. https://bugs.launchpad.net/bugs/1574582 Title: HP lt4120 Snapdragon X5 LTE USB modem not recognized by network- manager To manage notifications about this bug go to: https://bugs.launchpad.net/ubuntu/+source/network-manager/+bug/1574582/+subscriptions -- ubuntu-bugs mailing list [email protected] https://lists.ubuntu.com/mailman/listinfo/ubuntu-bugs
