USB port drop.

[kangjianwei]

imx7 usb host port connect to one external LTE modem, sometime the LTE USB CDC ethernet port can drop.  the dmesg  log as here:

usb 1-1: USB disconnect, device number 5
cdc_ether 1-1:1.0 wwan0: unregister 'cdc_ether' usb-ci_hdrc.1-1, Mobile Broadband Network Device
cdc_ether 1-1:1.4 wwan1: unregister 'cdc_ether' usb-ci_hdrc.1-1, Mobile Broadband Network Device
usb usb1-port1: cannot reset (err = -32)
usb usb1-port1: cannot reset (err = -32)
usb usb1-port1: cannot reset (err = -32)
usb usb1-port1: cannot reset (err = -32)
usb usb1-port1: cannot reset (err = -32)
usb usb1-port1: Cannot enable. Maybe the USB cable is bad?
usb usb1-port1: cannot reset (err = -32)
usb usb1-port1: cannot reset (err = -32)
usb usb1-port1: cannot reset (err = -32)
usb usb1-port1: cannot reset (err = -32)
usb usb1-port1: cannot reset (err = -32)
usb usb1-port1: Cannot enable. Maybe the USB cable is bad?
usb usb1-port1: cannot reset (err = -32)
usb usb1-port1: cannot reset (err = -32)
usb usb1-port1: cannot reset (err = -32)
usb usb1-port1: cannot reset (err = -32)
usb usb1-port1: cannot reset (err = -32)
usb usb1-port1: Cannot enable. Maybe the USB cable is bad?
usb usb1-port1: cannot reset (err = -32)
usb usb1-port1: cannot reset (err = -32)
usb usb1-port1: cannot reset (err = -32)
usb usb1-port1: cannot reset (err = -32)
usb usb1-port1: cannot reset (err = -32)
usb usb1-port1: Cannot enable. Maybe the USB cable is bad?
usb usb1-port1: unable to enumerate USB device

what the root cause the error?  

[lourdu_xavier]

Hi Kang,

We are also facing the same issue, can you please let us know how did you resolved this issue, any input can help us a lot.

Thanks in advance.

[igorpadykov]

Hi kang

in general your assumption may be correct, reason may be weak/noisy signal

due to cable or insufficient power supply. For modem one can check that usb cable

was not near antenna output and was sufficiently shielded. One can try to use

usb hub with external power supply.

Best regards
igor
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