DW5821e Modem no CDC MBIM interface

Hardware Questions and Recommendations
1

Hi! I'm trying to connect Dell DW5821e miniPCIe modem (works in USB3.0 mode) to ZBT WG1608 router. CDC works on Rooter firmware but no luck with Openwrt (tried multiple 23.05 builds). Whatever I tried it does not expose /dev/cdc_wdm interface. I still can establish connection with Modemanager and can chat with modem via /dev/ttyUSB0 with picocom.
Anybody has same issue or working config? Can you please help

2

Get rid of MM and show the output of cat /sys/kernel/debug/usb/devices

3 
T:  Bus=02 Lev=02 Prnt=02 Port=01 Cnt=01 Dev#=  5 Spd=5000 MxCh= 0
D:  Ver= 3.10 Cls=ef(misc ) Sub=02 Prot=01 MxPS= 9 #Cfgs=  2
P:  Vendor=413c ProdID=81d7 Rev= 3.18
S:  Manufacturer=Dell Inc.
S:  Product=DW5821e Snapdragon X20 LTE
S:  SerialNumber=0123456789ABCDEF
C:  #Ifs= 6 Cfg#= 1 Atr=a0 MxPwr=896mA
I:  If#= 0 Alt= 0 #EPs= 3 Cls=ff(vend.) Sub=ff Prot=ff Driver=
E:  Ad=81(I) Atr=03(Int.) MxPS=   8 Ivl=32ms
E:  Ad=8e(I) Atr=02(Bulk) MxPS=1024 Ivl=0ms
E:  Ad=0f(O) Atr=02(Bulk) MxPS=1024 Ivl=0ms
I:  If#= 1 Alt= 0 #EPs= 1 Cls=03(HID  ) Sub=00 Prot=00 Driver=
E:  Ad=82(I) Atr=03(Int.) MxPS=   1 Ivl=4096ms
I:  If#= 2 Alt= 0 #EPs= 3 Cls=ff(vend.) Sub=00 Prot=00 Driver=
E:  Ad=84(I) Atr=03(Int.) MxPS=  10 Ivl=32ms
E:  Ad=83(I) Atr=02(Bulk) MxPS=1024 Ivl=0ms
E:  Ad=01(O) Atr=02(Bulk) MxPS=1024 Ivl=0ms
I:  If#= 3 Alt= 0 #EPs= 3 Cls=ff(vend.) Sub=00 Prot=00 Driver=
E:  Ad=86(I) Atr=03(Int.) MxPS=  10 Ivl=32ms
E:  Ad=85(I) Atr=02(Bulk) MxPS=1024 Ivl=0ms
E:  Ad=02(O) Atr=02(Bulk) MxPS=1024 Ivl=0ms
I:  If#= 4 Alt= 0 #EPs= 3 Cls=ff(vend.) Sub=00 Prot=00 Driver=
E:  Ad=88(I) Atr=03(Int.) MxPS=  10 Ivl=32ms
E:  Ad=87(I) Atr=02(Bulk) MxPS=1024 Ivl=0ms
E:  Ad=03(O) Atr=02(Bulk) MxPS=1024 Ivl=0ms
I:  If#= 5 Alt= 0 #EPs= 2 Cls=ff(vend.) Sub=ff Prot=ff Driver=
E:  Ad=89(I) Atr=02(Bulk) MxPS=1024 Ivl=0ms
E:  Ad=04(O) Atr=02(Bulk) MxPS=1024 Ivl=0ms
C:* #Ifs= 7 Cfg#= 2 Atr=a0 MxPwr=896mA
A:  FirstIf#= 0 IfCount= 2 Cls=02(comm.) Sub=0e Prot=00
I:* If#= 0 Alt= 0 #EPs= 1 Cls=02(comm.) Sub=0e Prot=00 Driver=(none)
E:  Ad=81(I) Atr=03(Int.) MxPS=  64 Ivl=32ms
I:* If#= 1 Alt= 0 #EPs= 0 Cls=0a(data ) Sub=00 Prot=02 Driver=(none)
I:  If#= 1 Alt= 1 #EPs= 2 Cls=0a(data ) Sub=00 Prot=02 Driver=(none)
E:  Ad=8e(I) Atr=02(Bulk) MxPS=1024 Ivl=0ms
E:  Ad=0f(O) Atr=02(Bulk) MxPS=1024 Ivl=0ms
I:* If#= 2 Alt= 0 #EPs= 3 Cls=ff(vend.) Sub=00 Prot=00 Driver=option
E:  Ad=83(I) Atr=03(Int.) MxPS=  10 Ivl=32ms
E:  Ad=82(I) Atr=02(Bulk) MxPS=1024 Ivl=0ms
E:  Ad=01(O) Atr=02(Bulk) MxPS=1024 Ivl=0ms
I:* If#= 3 Alt= 0 #EPs= 3 Cls=ff(vend.) Sub=00 Prot=00 Driver=option
E:  Ad=85(I) Atr=03(Int.) MxPS=  10 Ivl=32ms
E:  Ad=84(I) Atr=02(Bulk) MxPS=1024 Ivl=0ms
E:  Ad=02(O) Atr=02(Bulk) MxPS=1024 Ivl=0ms
I:* If#= 4 Alt= 0 #EPs= 3 Cls=ff(vend.) Sub=00 Prot=00 Driver=option
E:  Ad=87(I) Atr=03(Int.) MxPS=  10 Ivl=32ms
E:  Ad=86(I) Atr=02(Bulk) MxPS=1024 Ivl=0ms
E:  Ad=03(O) Atr=02(Bulk) MxPS=1024 Ivl=0ms
I:* If#= 5 Alt= 0 #EPs= 2 Cls=ff(vend.) Sub=ff Prot=ff Driver=option
E:  Ad=88(I) Atr=02(Bulk) MxPS=1024 Ivl=0ms
E:  Ad=04(O) Atr=02(Bulk) MxPS=1024 Ivl=0ms
I:* If#= 6 Alt= 0 #EPs= 1 Cls=ff(vend.) Sub=ff Prot=ff Driver=(none)
E:  Ad=89(I) Atr=03(Int.) MxPS=  64 Ivl=32ms
4

This is your MBIM. Follow https://openwrt.org/docs/guide-user/network/wan/wwan/ltedongle

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5

My issue was due to usb-modeswitch. I removed package and /dev/cdc_wdm0 appeared after reboot. Took almost a day... Thank you.