ModemManager - connecting multiple modems simultaneously always fail

[Lars Melin]

On 9/28/2021 02:24, Lucas Pelegrino wrote:

 > This modem works when I connect it by itself. I also tested
 > different permutations and it seems it’s always the third modem that> 
can’t get a connection, independently of which one I put on first.
 > This is the full log with debug on: https://pastebin.com/L3QWBppt
 > <https://pastebin.com/L3QWBppt>
 >
 > Any ideas?
 >

Your host controller has a limit of 16 hostchannels (see 
/drivers/usb/dwc2/core.h) which means that it can only handle 16 
endpoints at a time.
Your hardware is a Raspberry Pi and it is using an out-of-tree kernel 
driver (dwc_otg) which is known to be extremely buggy, one of many bugs 
is that it takes long time for it to release a hostchannel that is not 
in use.

cheers
Lars