USB shutdown issue

[manty kuma]

Hi,

I have a  USB modem connected to my Edison based board.
*The USB Modem is frequently disconnected and comes back again in sometime.*
Here are the corresponding logs

---------------------------------------------------------------------------------------------------------
[ 2054.590012] *hub 1-0:1.0: port 1 disabled by hub (EMI?), re-enabling...*
[ 2054.590129] usb 1-1: USB disconnect, device number 3
[ 2054.590610] cdc_ether 1-1:1.0 enp0s17u1: unregister 'cdc_ether'
usb-dwc3-host.2-1, CDC Ethernet Device
[ 2062.368706] usb 1-1: new high-speed USB device number 4 using dwc3-host
[ 2062.393589] usb 1-1: New USB device found, idVendor=12d1, idProduct=1f01
[ 2062.393621] usb 1-1: New USB device strings: Mfr=1, Product=2,
SerialNumber=3
[ 2062.393642] usb 1-1: Product: HUAWEI Mobile
[ 2062.393661] usb 1-1: Manufacturer: HUAWEI
....
[ 2063.629109] cdc_ether 1-1:1.0 eth0: register 'cdc_ether' at
usb-dwc3-host.2-1, CDC Ethernet Device, 00:1e:10:1f:00:00
---------------------------------------------------------------------------------------------------------

As i understand this log, due to some reason, the USB hub port 1 is
shutdown.
Detecting this, the USB hub driver is re-enabling the port.

I would like to know why exactky the USB hub's port is shutfown.
In short I am trying to find out the reason for this message - "port 1
disabled by hub (EMI?), re-enabling..."
The source code that is doing this is here -
http://androidxref.com/kernel_3.10/xref/drivers/usb/core/hub.c#4693

But I did not get much info from here. Someone who is proficient with USB
protocol might be able to asnwer this very quickly.

Looking forward for response.

My env :
Platform Intel Edison
Linux :  3.10 built using Yocto.
root at edison:~# uname -a
Linux edison 3.10.98-poky-edison+ #2 SMP PREEMPT Wed Feb 22 11:23:11 JST
2017 i686 GNU/Linux

Best Regards,
Manty
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