PDU session not establishing in Quectel RG255C-GL

Technical Subjects
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1

Hello all,

I am using Quectel RG255C-GL with version RG255CGLABR01A08M4G_A0.001.A0.001. I am facing issues with connectivity as the module is not establishing a PDU session or obtaining an IP address.

Below are the logs:

When I start the UE, the following logs appear, but there is no wwan interface:

[  671.464682] usb 1-1.1: new high-speed USB device number 5 using xhci_hcd
[  671.566501] usb 1-1.1: New USB device found, idVendor=2c7c, idProduct=0316, bcdDevice= 5.15
[  671.566534] usb 1-1.1: New USB device strings: Mfr=1, Product=2, SerialNumber=3
[  671.566550] usb 1-1.1: Product: RG255C-GL
[  671.566564] usb 1-1.1: Manufacturer: Quectel
[  671.566577] usb 1-1.1: SerialNumber: 4b9b150c

When using the command lsusb -t, the output is:

/:  Bus 03.Port 1: Dev 1, Class=root_hub, Driver=dwc2/1p, 480M
/:  Bus 02.Port 1: Dev 1, Class=root_hub, Driver=xhci_hcd/4p, 5000M
/:  Bus 01.Port 1: Dev 1, Class=root_hub, Driver=xhci_hcd/1p, 480M
    |__ Port 1: Dev 2, If 0, Class=Hub, Driver=hub/4p, 480M
        |__ Port 1: Dev 5, If 0, Class=Vendor Specific Class, Driver=, 480M
        |__ Port 1: Dev 5, If 1, Class=Vendor Specific Class, Driver=, 480M
        |__ Port 1: Dev 5, If 2, Class=Vendor Specific Class, Driver=qmi_wwan, 480M
        |__ Port 1: Dev 5, If 3, Class=Vendor Specific Class, Driver=qmi_wwan, 480M

After manually forcing /dev/cdc-wdm, two interfaces appear:

wwan0, wwan1

However, the module is still not establishing a PDU session.

Some extra information from the UE side after running start script:

./start.sh 
error: couldn't open the QmiDevice: Couldn't spawn the qmi-proxy
error: couldn't open the QmiDevice: Couldn't spawn the qmi-proxy
error: couldn't open the QmiDevice: Couldn't spawn the qmi-proxy
error: couldn't open the QmiDevice: Couldn't spawn the qmi-proxy
Error: argument "" is wrong: "dev" not a valid ifname
tee: /sys/class/net//qmi/raw_ip: No such file or directory
Y
Error: argument "" is wrong: "dev" not a valid ifname
udhcpc: SIOCGIFINDEX: No such device
2

Hi @khan,

the qmi_wwan driver should not bind to USB interface 2 as it is the AT port.
Please see Making sure you're not a bot! for comparison.

Regards,
Reinhard

3

Hello @rspmn

Thank you for the answering. I tried a lot of stuff but still has the same issue. The device is correctly recognized via USB, but after manually binding, /dev/cdc-wdm0 and sometimes /dev/cdc-wdm1 are created. Occasionally, wwan0 and wwan1 interfaces appear but not always. However, /dev/ttyUSBx interfaces are unreliable or missing, making it impossible to send AT commands (e.g., to set the APN).
Any guidance, working configurations would be greatly appreciated
thanks

4

Hi @khan,

if you can’t rebuild the Linux kernel modules like qmi_wwan.ko with support for RG255C-GL added and you are using the new_id mechanism instead you have to ensure that the bindings don’t overlap, e.g. by using

rmmod option
rmmod qmi_wwan
modprobe option
modprobe qmi_wwan
echo 2c7c 0316 ff 05c6 90fa > /sys/bus/usb-serial/drivers/option1/new_id
echo 2c7c 0316 ff 1bc7 1031 > /sys/bus/usb/drivers/qmi_wwan/new_id

Regards,
Reinhard

5

Thanks @rspmn for the answer.

I have resolved interface and driver issues (ttyUSB and wwan devices are correctly bound), I’m now stuck at the PDU session step.

When trying to start the network using qmicli or a QMI script, I receive the following error:

[/dev/cdc-wdm0] Operating mode set successfully
[/dev/cdc-wdm0] Operating mode set successfully
error: couldn't start network: QMI protocol error (14): 'CallFailed'
call end reason (3): generic-no-service
verbose call end reason (3,2001): [cm] no-service
[/dev/cdc-wdm0] Client ID not released:
	Service: 'wds'
	    CID: '15'
Y
udhcpc: started, v1.30.1
udhcpc: sending discover
udhcpc: sending discover
^CRTNETLINK answers: No such proces

Additionally:

AT+CEREG? shows 0,0

AT+COPS? doesn't select the operator automatically.

Even manual selection with AT+COPS=1,2,"99940" (PLMN for my Open5GS core) sometimes fails or doesn't lead to registration.

Signal strength shows "SEARCHING" with AT+QENG="servingcell"

Any Guideline

Thanks

6

@khan, please note that the correct AT command to check for 5G SA registration would be AT+C5GREG?. However it would proably not show “registered” if AT+QENG="servingcell" shows SEARCHING.

If AT+COPS=? returns your network with <AcT> 12 and the SIM used is able to register to your 5G SA network when used with a non-5G RedCap device you might see a similar problem as observed by another RG255C-GL user here Missing enum? "Get RF Band Information" (0x0031) / "Bandwidth List" (0x12) -> Value 9 where the status was “LIMSRV” however.

You probably need the support of Quectel for obtaining Qualcomm logs like Catching logs from RG255C-GL with QLog to solve your problem.

Regards,
Reinhard

7

Hi Khan, I have the same issue, the UE which is RMU500-EV does not establish a PDU session. Would you tell me how you resolve the PDU issue?