On Tue, 14 Aug 2018, Muni Sekhar wrote: > On Mon, Aug 13, 2018 at 7:52 PM, Muni Sekhar <munisekharrms@xxxxxxxxx> wrote: > > On Mon, Aug 13, 2018 at 6:57 PM, Oliver Neukum <oneukum@xxxxxxxx> wrote: > >> On Mo, 2018-08-13 at 18:44 +0530, Muni Sekhar wrote: > >>> [ Please keep me in CC as I'm not subscribed to the list] > >>> > >>> Hello All, > >>> > >>> I’ve a FTDI serial device and it is not recognized if I connect > >>> directly to computer. However if I connect via an external USB hub > >>> it’s fine and I can see the FTDI serial device. What could be the > >>> issue and how to resolve this? > If I connect the FTDI device directly to computer I don't see any > dmesg log, but after enabling the dynamic debugging for usbcore and > hcd's driver then I see kernel log flooded with the below mentioned > logs. Is it a bug in the hcd's driver? The same device works fine if I > connect via an external USB hub. > > [14045.942047] hub 2-0:1.0: state 7 ports 6 chg 0000 evt 0004 > [14045.942156] usb usb2-port2: status 0100, change 0001, 12 Mb/s > [14046.102357] usb usb2-port2: debounce total 125ms stable 100ms status 0x101 > [14046.158579] hub 2-0:1.0: state 7 ports 6 chg 0000 evt 0004 > [14046.158692] usb usb2-port2: status 0100, change 0001, 12 Mb/s > [14046.318662] usb usb2-port2: debounce total 125ms stable 100ms status 0x101 > [14046.374689] hub 2-0:1.0: state 7 ports 6 chg 0000 evt 0004 > [14046.374798] usb usb2-port2: status 0100, change 0001, 12 Mb/s > [14046.535001] usb usb2-port2: debounce total 125ms stable 100ms status 0x101 > [14046.591050] hub 2-0:1.0: state 7 ports 6 chg 0000 evt 0004 > [14046.591161] usb usb2-port2: status 0100, change 0001, 12 Mb/s > [14046.751382] usb usb2-port2: debounce total 125ms stable 100ms status 0x101 > [14046.807415] hub 2-0:1.0: state 7 ports 6 chg 0000 evt 0004 > [14046.807527] usb usb2-port2: status 0100, change 0001, 12 Mb/s > [14046.967725] usb usb2-port2: debounce total 125ms stable 100ms status 0x101 > [14047.023761] hub 2-0:1.0: state 7 ports 6 chg 0000 evt 0004 > [14047.023872] usb usb2-port2: status 0100, change 0001, 12 Mb/s > [14047.184025] usb usb2-port2: debounce total 125ms stable 100ms status 0x101 > [14047.240078] hub 2-0:1.0: state 7 ports 6 chg 0000 evt 0004 These messages indicate the device is electronically detaching itself from the bus and then reattaching itself, over and over again, about four times per second. Have you tried using this device on another computer? Do you have another full-speed device you can try plugging into that port? Alan Stern
