Hi, I am running kernel LTS 4.19 in an i.MX6 board with a 4G LTE modem, it continually displayed following messages in a serial port tried and failed to connect to LTE modem, are there any problems in kernel 4.19 LTS to support usb qmi protocol and LTE modem connection? I did try the kernel version 5.1, it can connect to the modem, but failed in couple of hours or days, when it disconnected, it got the same following messages. Are there serious problems in kernel to support usb qmi LTE modem communication and connection? [ 43.837243] option1 ttyUSB0: GSM modem (1-port) converter now disconnected f0 [ 43.882941] option 1-1:1.0: device disconnected [ 43.942788] option1 ttyUSB1: GSM modem (1-port) converter now disconnected f1 [ 44.001445] option 1-1:1.2: device disconnected [ 44.011575] qmi_wwan 1-1:1.3: nonzero urb status received: -71 [ 44.017461] qmi_wwan 1-1:1.3: wdm_int_callback - 0 bytes [ 44.022801] qmi_wwan 1-1:1.3: wdm_int_callback - usb_submit_urb failed with 9 [ 44.059958] qmi_wwan 1-1:1.3 wwan0: unregister 'qmi_wwan' usb-ci_hdrc.1-1, We [ 47.675604] usb 1-1: new high-speed USB device number 5 using ci_hdrc [ 47.905246] usb 1-1: New USB device found, idVendor=05c6, idProduct=90b2, bc0 [ 47.913732] usb 1-1: New USB device strings: Mfr=3, Product=2, SerialNumber=4 [ 47.921099] usb 1-1: Product: Qualcomm CDMA Technologies MSM [ 47.927087] usb 1-1: Manufacturer: Qualcomm, Incorporated [ 47.932746] usb 1-1: SerialNumber: 5ff10299 [ 47.964528] option 1-1:1.0: GSM modem (1-port) converter detected [ 47.989484] usb 1-1: GSM modem (1-port) converter now attached to ttyUSB0 [ 48.014760] option 1-1:1.2: GSM modem (1-port) converter detected [ 48.026996] usb 1-1: GSM modem (1-port) converter now attached to ttyUSB1 [ 48.048810] qmi_wwan 1-1:1.3: cdc-wdm0: USB WDM device [ 48.082751] qmi_wwan 1-1:1.3 wwan0: register 'qmi_wwan' at usb-ci_hdrc.1-1, 8 [ 51.581595] usb 1-1: USB disconnect, device number 5 [ 51.613737] option1 ttyUSB0: GSM modem (1-port) converter now disconnected f0 [ 51.644564] option 1-1:1.0: device disconnected [ 51.713919] option1 ttyUSB1: GSM modem (1-port) converter now disconnected f1 [ 51.771139] option 1-1:1.2: device disconnected Thank you. Kind regards, - jh
