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@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