5G Hat constant disconnection

Hello,
I’m experiencing a critical issue with the RM502Q-AE modem where it constantly
disconnects and reconnects over USB, causing all serial ports (ttyUSB0-3) and
the network interface to become unavailable periodically.
SYSTEM INFORMATION:

  • Device: Quectel RM502Q-AE

  • Host: NVIDIA Jetson Orin NX

  • OS: Linux (Jetson-specific build)

  • Kernel: 5.15.148-tegra

  • Firmware Version: RM502QAEAAR11A04M4G_01.202.01.202

  • SIM: AT&t BUSINESS SIM CARD

  • AT+QCFG="usbnet”,1 #this is ECM mode

PROBLEM:
The modem disconnects and reconnects over USB (period of a few seconds),
causing:

  • All serial ports (ttyUSB0-3) to disconnect/reconnect

  • Network interface (enx…) to unregister/reregister

  • USB transfer errors in kernel logs

  • “Enable of device-initiated U1/U2 failed” errors. I attached a log of the dmesg.

[  131.555675] option1 ttyUSB0: GSM modem (1-port) converter now disconnected from ttyUSB0
[  131.555726] option 2-1.4:1.0: device disconnected
[  131.555937] option1 ttyUSB1: GSM modem (1-port) converter now disconnected from ttyUSB1
[  131.555973] option 2-1.4:1.1: device disconnected
[  131.556113] option1 ttyUSB2: GSM modem (1-port) converter now disconnected from ttyUSB2
[  131.556144] option 2-1.4:1.2: device disconnected
[  131.556328] option1 ttyUSB3: GSM modem (1-port) converter now disconnected from ttyUSB3
[  131.556358] option 2-1.4:1.3: device disconnected
[  131.556602] cdc_ether 2-1.4:1.4 enx663433372948: unregister 'cdc_ether' usb-3610000.usb-1.4, CDC Ethernet Device
[  131.558739] tegra-xusb 3610000.usb: ERROR Transfer event TRB DMA ptr not part of current TD ep_index 28 comp_code 4
[  131.558747] tegra-xusb 3610000.usb: Looking for event-dma 0000007ffff938e0 trb-start 0000007ffff938f0 trb-end 0000000000000000 seg-start 0000007ffff93000 seg-end 0000007ffff93ff0
[  131.558754] tegra-xusb 3610000.usb: Looking for event-dma 0000007ffff938e0 trb-start 0000007fffd4c000 trb-end 0000007fffd4c9c0 seg-start 0000007fffd4c000 seg-end 0000007fffd4cff0
[  131.561830] tegra-xusb 3610000.usb: WARN Event TRB for slot 4 ep 28 with no TDs queued?
[  131.614822] usb 2-1.4: Set SEL for device-initiated U1 failed.
[  131.616809] usb 2-1.4: Set SEL for device-initiated U2 failed.
[  131.955627] usb 2-1.4: reset SuperSpeed Plus Gen 2x1 USB device number 3 using tegra-xusb
[  131.983300] usb 2-1.4: Enable of device-initiated U1 failed.
[  131.995433] usb 2-1.4: Enable of device-initiated U2 failed.
[  132.006058] option 2-1.4:1.0: GSM modem (1-port) converter detected
[  132.006267] usb 2-1.4: GSM modem (1-port) converter now attached to ttyUSB0
[  132.006349] option 2-1.4:1.1: GSM modem (1-port) converter detected
[  132.006465] usb 2-1.4: GSM modem (1-port) converter now attached to ttyUSB1
[  132.006529] option 2-1.4:1.2: GSM modem (1-port) converter detected
[  132.006736] usb 2-1.4: GSM modem (1-port) converter now attached to ttyUSB2
[  132.006800] option 2-1.4:1.3: GSM modem (1-port) converter detected
[  132.006948] usb 2-1.4: GSM modem (1-port) converter now attached to ttyUSB3
[  132.009027] cdc_ether 2-1.4:1.4 usb2: register 'cdc_ether' at usb-3610000.usb-1.4, CDC Ethernet Device, 66:34:33:37:29:48
[  132.010569] usb 2-1.4: Enable of device-initiated U1 failed.
[  132.022828] usb 2-1.4: Enable of device-initiated U2 failed.
[  132.043590] cdc_ether 2-1.4:1.4 enx663433372948: renamed from usb2
[  188.675874] option1 ttyUSB0: GSM modem (1-port) converter now disconnected from ttyUSB0
[  188.675928] option 2-1.4:1.0: device disconnected
[  188.676162] option1 ttyUSB1: GSM modem (1-port) converter now disconnected from ttyUSB1
[  188.676197] option 2-1.4:1.1: device disconnected
[  188.676349] option1 ttyUSB2: GSM modem (1-port) converter now disconnected from ttyUSB2
[  188.676381] option 2-1.4:1.2: device disconnected
[  188.678451] option1 ttyUSB3: GSM modem (1-port) converter now disconnected from ttyUSB3
[  188.678511] option 2-1.4:1.3: device disconnected
[  188.678737] cdc_ether 2-1.4:1.4 enx663433372948: unregister 'cdc_ether' usb-3610000.usb-1.4, CDC Ethernet Device
[  188.680890] tegra-xusb 3610000.usb: ERROR Transfer event TRB DMA ptr not part of current TD ep_index 28 comp_code 4
[  188.680898] tegra-xusb 3610000.usb: Looking for event-dma 0000007ffff98680 trb-start 0000007ffff98690 trb-end 0000000000000000 seg-start 0000007ffff98000 seg-end 0000007ffff98ff0
[  188.680906] tegra-xusb 3610000.usb: Looking for event-dma 0000007ffff98680 trb-start 0000007ffff9a000 trb-end 0000007ffff9a7f0 seg-start 0000007ffff9a000 seg-end 0000007ffff9aff0
[  188.682451] tegra-xusb 3610000.usb: WARN Event TRB for slot 4 ep 28 with no TDs queued?
[  188.742427] usb 2-1.4: Set SEL for device-initiated U1 failed.
[  188.744042] usb 2-1.4: Set SEL for device-initiated U2 failed.
[  189.071369] usb 2-1.4: reset SuperSpeed Plus Gen 2x1 USB device number 3 using tegra-xusb
[  189.103305] usb 2-1.4: Enable of device-initiated U1 failed.
[  189.115551] usb 2-1.4: Enable of device-initiated U2 failed.
[  189.126126] option 2-1.4:1.0: GSM modem (1-port) converter detected
[  189.126404] usb 2-1.4: GSM modem (1-port) converter now attached to ttyUSB0
[  189.126565] option 2-1.4:1.1: GSM modem (1-port) converter detected
[  189.126748] usb 2-1.4: GSM modem (1-port) converter now attached to ttyUSB1
[  189.126862] option 2-1.4:1.2: GSM modem (1-port) converter detected
[  189.127004] usb 2-1.4: GSM modem (1-port) converter now attached to ttyUSB2
[  189.127096] option 2-1.4:1.3: GSM modem (1-port) converter detected
[  189.127230] usb 2-1.4: GSM modem (1-port) converter now attached to ttyUSB3
[  189.129410] cdc_ether 2-1.4:1.4 usb2: register 'cdc_ether' at usb-3610000.usb-1.4, CDC Ethernet Device, 66:34:33:37:29:48
[  189.131237] usb 2-1.4: Enable of device-initiated U1 failed.
[  189.143179] usb 2-1.4: Enable of device-initiated U2 failed.
[  189.164434] cdc_ether 2-1.4:1.4 enx663433372948: renamed from usb2
[  261.587934] option1 ttyUSB0: GSM modem (1-port) converter now disconnected from ttyUSB0
[  261.587993] option 2-1.4:1.0: device disconnected
[  261.588169] option1 ttyUSB1: GSM modem (1-port) converter now disconnected from ttyUSB1
[  261.588257] option 2-1.4:1.1: device disconnected
[  261.588498] option1 ttyUSB2: GSM modem (1-port) converter now disconnected from ttyUSB2
[  261.588530] option 2-1.4:1.2: device disconnected
[  261.588715] option1 ttyUSB3: GSM modem (1-port) converter now disconnected from ttyUSB3
[  261.588747] option 2-1.4:1.3: device disconnected
[  261.588981] cdc_ether 2-1.4:1.4 enx663433372948: unregister 'cdc_ether' usb-3610000.usb-1.4, CDC Ethernet Device
[  261.591071] tegra-xusb 3610000.usb: ERROR Transfer event TRB DMA ptr not part of current TD ep_index 28 comp_code 4
[  261.591078] tegra-xusb 3610000.usb: Looking for event-dma 0000007ffff9c5c0 trb-start 0000007ffff9c5d0 trb-end 0000000000000000 seg-start 0000007ffff9c000 seg-end 0000007ffff9cff0
[  261.591085] tegra-xusb 3610000.usb: Looking for event-dma 0000007ffff9c5c0 trb-start 0000007ffff9b000 trb-end 0000007ffff9b680 seg-start 0000007ffff9b000 seg-end 0000007ffff9bff0
[  261.592856] tegra-xusb 3610000.usb: ERROR Transfer event TRB DMA ptr not part of current TD ep_index 28 comp_code 4
[  261.592865] tegra-xusb 3610000.usb: Looking for event-dma 0000007ffff9b680 trb-start 0000007ffff9b690 trb-end 0000007ffff9b6c0 seg-start 0000007ffff9b000 seg-end 0000007ffff9bff0
[  261.594041] tegra-xusb 3610000.usb: WARN Event TRB for slot 4 ep 28 with no TDs queued?
[  261.640302] usb 2-1.4: Set SEL for device-initiated U1 failed.
[  261.641919] usb 2-1.4: Set SEL for device-initiated U2 failed.
[  261.969254] usb 2-1.4: reset SuperSpeed Plus Gen 2x1 USB device number 3 using tegra-xusb
[  261.996680] usb 2-1.4: Enable of device-initiated U1 failed.
[  262.008927] usb 2-1.4: Enable of device-initiated U2 failed.
[  262.019477] option 2-1.4:1.0: GSM modem (1-port) converter detected
[  262.019694] usb 2-1.4: GSM modem (1-port) converter now attached to ttyUSB0
[  262.019816] option 2-1.4:1.1: GSM modem (1-port) converter detected
[  262.019953] usb 2-1.4: GSM modem (1-port) converter now attached to ttyUSB1
[  262.020057] option 2-1.4:1.2: GSM modem (1-port) converter detected
[  262.020178] usb 2-1.4: GSM modem (1-port) converter now attached to ttyUSB2
[  262.020346] option 2-1.4:1.3: GSM modem (1-port) converter detected
[  262.020500] usb 2-1.4: GSM modem (1-port) converter now attached to ttyUSB3
[  262.026483] cdc_ether 2-1.4:1.4 usb2: register 'cdc_ether' at usb-3610000.usb-1.4, CDC Ethernet Device, 66:34:33:37:29:48
[  262.028183] usb 2-1.4: Enable of device-initiated U1 failed.
[  262.040426] usb 2-1.4: Enable of device-initiated U2 failed.
[  262.061986] cdc_ether 2-1.4:1.4 enx663433372948: renamed from usb2
[  271.347808] option1 ttyUSB0: GSM modem (1-port) converter now disconnected from ttyUSB0
[  271.347859] option 2-1.4:1.0: device disconnected
[  271.348156] option1 ttyUSB1: GSM modem (1-port) converter now disconnected from ttyUSB1
[  271.348192] option 2-1.4:1.1: device disconnected
[  271.348444] option1 ttyUSB2: GSM modem (1-port) converter now disconnected from ttyUSB2
[  271.348475] option 2-1.4:1.2: device disconnected
[  271.348617] option1 ttyUSB3: GSM modem (1-port) converter now disconnected from ttyUSB3
[  271.348650] option 2-1.4:1.3: device disconnected
[  271.348860] cdc_ether 2-1.4:1.4 enx663433372948: unregister 'cdc_ether' usb-3610000.usb-1.4, CDC Ethernet Device
[  271.350983] tegra-xusb 3610000.usb: ERROR Transfer event TRB DMA ptr not part of current TD ep_index 28 comp_code 4
[  271.350994] tegra-xusb 3610000.usb: Looking for event-dma 0000007ffff9c180 trb-start 0000007ffff9c190 trb-end 0000000000000000 seg-start 0000007ffff9c000 seg-end 0000007ffff9cff0
[  271.351006] tegra-xusb 3610000.usb: Looking for event-dma 0000007ffff9c180 trb-start 0000007ffff9b000 trb-end 0000007ffff9b280 seg-start 0000007ffff9b000 seg-end 0000007ffff9bff0
[  271.397186] usb 2-1.4: Set SEL for device-initiated U1 failed.
[  271.398858] usb 2-1.4: Set SEL for device-initiated U2 failed.
[  271.729130] usb 2-1.4: reset SuperSpeed Plus Gen 2x1 USB device number 3 using tegra-xusb
[  271.757433] usb 2-1.4: Enable of device-initiated U1 failed.
[  271.769683] usb 2-1.4: Enable of device-initiated U2 failed.
[  271.780316] option 2-1.4:1.0: GSM modem (1-port) converter detected
[  271.780575] usb 2-1.4: GSM modem (1-port) converter now attached to ttyUSB0
[  271.780701] option 2-1.4:1.1: GSM modem (1-port) converter detected
[  271.780843] usb 2-1.4: GSM modem (1-port) converter now attached to ttyUSB1
[  271.780936] option 2-1.4:1.2: GSM modem (1-port) converter detected
[  271.781058] usb 2-1.4: GSM modem (1-port) converter now attached to ttyUSB2
[  271.781148] option 2-1.4:1.3: GSM modem (1-port) converter detected
[  271.781314] usb 2-1.4: GSM modem (1-port) converter now attached to ttyUSB3
[  271.783749] cdc_ether 2-1.4:1.4 usb2: register 'cdc_ether' at usb-3610000.usb-1.4, CDC Ethernet Device, 66:34:33:37:29:48
[  271.785686] usb 2-1.4: Enable of device-initiated U1 failed.
[  271.797931] usb 2-1.4: Enable of device-initiated U2 failed.
[  271.819654] cdc_ether 2-1.4:1.4 enx663433372948: renamed from usb2

Hello @DDa,

Thank you for sharing the detailed logs and explanation of the issue you are experiencing.

To better understand your setup and investigate the root cause of the USB disconnect/reconnect problem, could you please provide the following:

  1. A clear picture of your full hardware setup

  2. Information about the USB Cable/Bridge you are currently using?

Once we have this information, we will be able to guide you further.