hi :
usb外接4g模块，出现如下log
...
[ 40.000151] usb 1-1: new high-speed USB device number 55 using musb-hdrc
[ 40.060145] hub 1-0:1.0: unable to enumerate USB device on port 1
[ 40.341129] usb 1-1: new high-speed USB device number 56 using musb-hdrc
[ 40.404164] hub 1-0:1.0: unable to enumerate USB device on port 1
[ 40.690269] usb 1-1: new high-speed USB device number 57 using musb-hdrc
[ 40.750153] hub 1-0:1.0: unable to enumerate USB device on port 1
[ 41.035855] usb 1-1: new high-speed USB device number 58 using musb-hdrc
[ 41.100144] hub 1-0:1.0: unable to enumerate USB device on port 1
[ 41.380140] usb 1-1: new high-speed USB device number 59 using musb-hdrc
[ 41.440156] hub 1-0:1.0: unable to enumerate USB device on port 1
[ 41.720114] usb 1-1: new high-speed USB device number 60 using musb-hdrc
[ 41.781243] hub 1-0:1.0: unable to enumerate USB device on port 1
[ 42.061840] usb 1-1: new high-speed USB device number 61 using musb-hdrc
[ 42.122857] hub 1-0:1.0: unable to enumerate USB device on port 1
[ 42.400093] usb 1-1: new high-speed USB device number 62 using musb-hdrc
[ 42.460209] hub 1-0:1.0: unable to enumerate USB device on port 1
[ 42.741528] usb 1-1: new high-speed USB device number 63 using musb-hdrc
[ 42.803306] hub 1-0:1.0: unable to enumerate USB device on port 1
[ 43.080245] usb 1-1: new high-speed USB device number 64 using musb-hdrc
[ 43.140152] hub 1-0:1.0: unable to enumerate USB device on port 1
[ 43.420092] usb 1-1: new high-speed USB device number 65 using musb-hdrc
[ 43.480123] hub 1-0:1.0: unable to enumerate USB device on port 1
[ 43.760098] usb 1-1: new high-speed USB device number 66 using musb-hdrc
[ 43.820200] hub 1-0:1.0: unable to enumerate USB device on port 1
[ 44.100148] usb 1-1: new high-speed USB device number 67 using musb-hdrc
[ 44.160201] hub 1-0:1.0: unable to enumerate USB device on port 1
[ 44.441314] usb 1-1: new high-speed USB device number 68 using musb-hdrc
[ 44.500171] hub 1-0:1.0: unable to enumerate USB device on port 1
[ 44.780226] usb 1-1: new high-speed USB device number 69 using musb-hdrc
[ 44.840297] hub 1-0:1.0: unable to enumerate USB device on port 1
[ 45.122931] usb 1-1: new high-speed USB device number 70 using musb-hdrc
....
对于usb这部分不是很了解，请帮忙分析一下这是什么原因导致的。
Thanks!
