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---Setup---

1) We are evaluating using Raspberry Pi Compute Module CM3.
2) USB-HUB and USB-UART are boarded on the IO board.
3) USB-HUB is working in Self-power mode.
4) VBUS-detect of USB-HUB uses the same 3.3V power supply as CM3.
5) Two LTE modules are connected to USB-HUB via USB-SERIAL and each LTE module takes 2A

---Protocol---

AT commands

---Problem----

The LTE modules which are connected to USB-HUB are disconnecting.This problem occurs only sometimes not always

Following are kernel Logs.

Kerenl log:

19:47:58 raspberrypi kernel: [ 9301.001438] usb usb1-port1: disabled by hub (EMI?), re-enabling...
19:47:58 raspberrypi kernel: [ 9301.001457] usb 1-1: USB disconnect, device number 11
19:47:58 raspberrypi kernel: [ 9301.001463] usb 1-1.1: USB disconnect, device number 12
19:47:58 raspberrypi kernel: [ 9301.001668] ftdi_sio ttyUSB2: error from flowcontrol urb
19:47:58 raspberrypi kernel: [ 9301.001872] ftdi_sio ttyUSB2: FTDI USB Serial Device converter now disconnected from ttyUSB2
19:47:58 raspberrypi kernel: [ 9301.001906] ftdi_sio 1-1.1:1.0: device disconnected
19:47:58 raspberrypi kernel: [ 9301.002107] ftdi_sio ttyUSB3: error from flowcontrol urb
19:47:58 raspberrypi kernel: [ 9301.003371] ftdi_sio ttyUSB3: FTDI USB Serial Device converter now disconnected from ttyUSB3
19:47:58 raspberrypi kernel: [ 9301.003429] ftdi_sio 1-1.1:1.1: device disconnected
19:47:58 raspberrypi kernel: [ 9301.010150] ftdi_sio ttyUSB4: FTDI USB Serial Device converter now disconnected from ttyUSB4
19:47:58 raspberrypi kernel: [ 9301.010212] ftdi_sio 1-1.1:1.2: device disconnected
19:47:58 raspberrypi kernel: [ 9301.010430] ftdi_sio ttyUSB5: error from flowcontrol urb
19:47:58 raspberrypi kernel: [ 9301.018012] ftdi_sio ttyUSB5: FTDI USB Serial Device converter now disconnected from ttyUSB5

---Question---

Any investigation method and solution?

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