RTL8812EU USB disconnect loop when wifibroadcast@gs starts on RPi 4B

[nachikethkumar]

Environment:
Hardware: Raspberry Pi 4B
OS: Ubuntu 24.04 LTS (noble), kernel 6.8.0-1048-raspi aarch64
WiFi card: BL-M8812EU2
Driver: rtl88x2eu v5.15.0.1-249-g9245f8bd9.202412 (DKMS, module name 8812eu)

Issue:
When wifibroadcast@gs starts, the RTL8812EU card enters a continuous USB disconnect/reconnect loop approximately every 8–11 seconds. The card is stable with no cycling when the service is stopped.

Power setup: WiFi card is powered directly from a 5V 5A BEC (Mini 560, also tried 7Semi DC-DC Buck Converter 14V-60V Input to 5V 3A Output- AP66300). Ground is common between BEC and RPi USB ground.
This exact setup works well when connected with laptop, USB card is stable on laptop at wifi_txpower = 2500 with identical BEC setup. but when connected to Pi 4B USB, wifi card Frequently connects and disconnects.

[231.622670] usb 1-1.3: Product: 802.11ac NIC
[ 231.622677] usb 1-1.3: Manufacturer: Realtek
[ 231.622683] usb 1-1.3: SerialNumber: 123456
[ 231.894010] rtl88x2eu 1-1.3:1.0 wlx88492d21d9fb: renamed from wlan1
[ 239.948475] rtl88x2eu 1-1.3:1.0 wlx88492d21d9fb: entered promiscuous mode
[ 240.535028] usb 1-1.3: USB disconnect, device number 17
[ 240.754167] usb 1-1.3: new high-speed USB device number 18 using xhci_hcd
[ 240.830875] usb 1-1.3: New USB device found, idVendor=0bda, idProduct=a81a, bcdDevice= 0.00
[ 240.830905] usb 1-1.3: New USB device strings: Mfr=1, Product=2, SerialNumber=3
[ 240.830913] usb 1-1.3: Product: 802.11ac NIC
[ 240.830920] usb 1-1.3: Manufacturer: Realtek
[ 240.830927] usb 1-1.3: SerialNumber: 123456
[ 241.111534] rtl88x2eu 1-1.3:1.0 wlx88492d21d9fb: renamed from wlan1
[ 249.188111] rtl88x2eu 1-1.3:1.0 wlx88492d21d9fb: entered promiscuous mode
[ 249.496208] usb 1-1.3: USB disconnect, device number 18
[ 249.743435] usb 1-1.3: new high-speed USB device number 19 using xhci_hcd
[ 249.819969] usb 1-1.3: New USB device found, idVendor=0bda, idProduct=a81a, bcdDevice= 0.00
[ 249.820029] usb 1-1.3: New USB device strings: Mfr=1, Product=2, SerialNumber=3
[ 249.820038] usb 1-1.3: Product: 802.11ac NIC
[ 249.820046] usb 1-1.3: Manufacturer: Realtek
[ 249.820053] usb 1-1.3: SerialNumber: 123456
[ 250.106954] rtl88x2eu 1-1.3:1.0 wlx88492d21d9fb: renamed from wlan1
[ 258.047244] rtl88x2eu 1-1.3:1.0 wlx88492d21d9fb: entered promiscuous mode
[ 266.138785] usb 1-1.3: USB disconnect, device number 19
[ 266.346837] usb 1-1.3: new high-speed USB device number 20 using xhci_hcd
[ 266.423424] usb 1-1.3: New USB device found, idVendor=0bda, idProduct=a81a, bcdDevice= 0.00
[ 266.423459] usb 1-1.3: New USB device strings: Mfr=1, Product=2, SerialNumber=3
[ 266.423467] usb 1-1.3: Product: 802.11ac NIC
[ 266.423474] usb 1-1.3: Manufacturer: Realtek
[ 266.423481] usb 1-1.3: SerialNumber: 123456
[ 266.705900] rtl88x2eu 1-1.3:1.0 wlx88492d21d9fb: renamed from wlan1
[ 274.772655] rtl88x2eu 1-1.3:1.0 wlx88492d21d9fb: entered promiscuous mode
[ 279.964722] usb 1-1.3: USB disconnect, device number 20
[ 280.188862] usb 1-1.3: new high-speed USB device number 21 using xhci_hcd
[ 280.265442] usb 1-1.3: New USB device found, idVendor=0bda, idProduct=a81a, bcdDevice= 0.00
[ 280.265470] usb 1-1.3: New USB device strings: Mfr=1, Product=2, SerialNumber=3
[ 280.265479] usb 1-1.3: Product: 802.11ac NIC
[ 280.265485] usb 1-1.3: Manufacturer: Realtek
[ 280.265492] usb 1-1.3: SerialNumber: 123456
[ 280.549085] rtl88x2eu 1-1.3:1.0 wlx88492d21d9fb: renamed from wlan1
[ 288.603770] rtl88x2eu 1-1.3:1.0 wlx88492d21d9fb: entered promiscuous mode
[ 289.182011] usb 1-1.3: USB disconnect, device number 21
[ 289.407944] usb 1-1.3: new high-speed USB device number 22 using xhci_hcd
[ 289.485683] usb 1-1.3: New USB device found, idVendor=0bda, idProduct=a81a, bcdDevice= 0.00
[ 289.485725] usb 1-1.3: New USB device strings: Mfr=1, Product=2, SerialNumber=3
[ 289.485734] usb 1-1.3: Product: 802.11ac NIC
[ 289.485740] usb 1-1.3: Manufacturer: Realtek
[ 289.485747] usb 1-1.3: SerialNumber: 123456
[ 289.769243] rtl88x2eu 1-1.3:1.0 wlx88492d21d9fb: renamed from wlan1
[ 297.846964] rtl88x2eu 1-1.3:1.0 wlx88492d21d9fb: entered promiscuous mode

[svpcom]

Check usb wires and/or port connection. Maybe some EMI. Check that only one usb device connected to the one usb port.