Copy of my issue here. Sorry for opening an issue here too, I do not know where else to ask as it seems more related to hardware itself than something software like Modem Manager. I have several (similar) usb enclosures that can fit a wwan card and I have been using to flash/use Sierra EM7455 and similar and also use it for L850's I got out of some refurbished laptops.
I've set the L850s into usb mode and they work fine on cold boot but somehow disappear when rebooting and then can only be made to work by replugging the enclosure. This happens in every single distro I have tried. From Debian to Arch to OpenWrt. Every single one behaves the same. As soon as I reboot the modem disappears, it is not even listed in lsusb anymore. This does not happen with Sierra cards in the same enclosure.
Do you have any idea what could cause this? I find it odd that the device completely disappears, nothing in lsusb or in /dev/tty* is showing but as soon and I plug it back in it works fine again. My first guess was that maybe Modem Manager does something "bad" when doing its shutdown but even when there is no Modem Manager installed the device disappears on a reboot. So I think it has something to do with the driver itself somehow switching into some kind of state it can't recover from that makes it disappear until a replug.
Once again sorry for opening an issue here, I don't really know where else to ask where there is so much knowledge of the L850. My guess is that the root cause is somewhere in the driver/kernel. As a sanity check I tried in Windows 10 and 11 and it works fine between reboot there. I have not tested BSD but on macOS it does not disappear between reboots either. Seems to be limited to Linux.
Sorry again for opening an issue here, please direct me to a better place to try and solve this issue if I'm in the wrong place.
tl;dr
modem disappears on reboot in every single Linux distro I tried
modem works fine on cold boots and when re-plugging usb enclosure
Copy of my issue here. Sorry for opening an issue here too, I do not know where else to ask as it seems more related to hardware itself than something software like Modem Manager. I have several (similar) usb enclosures that can fit a wwan card and I have been using to flash/use Sierra EM7455 and similar and also use it for L850's I got out of some refurbished laptops.
I've set the L850s into usb mode and they work fine on cold boot but somehow disappear when rebooting and then can only be made to work by replugging the enclosure. This happens in every single distro I have tried. From Debian to Arch to OpenWrt. Every single one behaves the same. As soon as I reboot the modem disappears, it is not even listed in
lsusbanymore. This does not happen with Sierra cards in the same enclosure.Do you have any idea what could cause this? I find it odd that the device completely disappears, nothing in
lsusbor in/dev/tty*is showing but as soon and I plug it back in it works fine again. My first guess was that maybe Modem Manager does something "bad" when doing its shutdown but even when there is no Modem Manager installed the device disappears on a reboot. So I think it has something to do with the driver itself somehow switching into some kind of state it can't recover from that makes it disappear until a replug.Once again sorry for opening an issue here, I don't really know where else to ask where there is so much knowledge of the L850. My guess is that the root cause is somewhere in the driver/kernel. As a sanity check I tried in Windows 10 and 11 and it works fine between reboot there. I have not tested BSD but on macOS it does not disappear between reboots either. Seems to be limited to Linux.
Sorry again for opening an issue here, please direct me to a better place to try and solve this issue if I'm in the wrong place.