On Wed, Nov 24, 2021 at 11:46:06AM +1100, Jupiter wrote: > Hi, > > I connected a USB bus between an iMX6ULZ and an 4G LTE modem, it was > running well in kernel 4.19.75. I've just upgraded kernel to 5.10.59, > the USB is broken, the USB drivers were disconnected / connected > repeatedly: > > [12781.730889] usb 1-1: USB disconnect, device number 84 > [12781.808317] option1 ttyUSB0: GSM modem (1-port) converter now > disconnected from ttyUSB0 That is usually a hardware problem, the kernel can not disconnect a device from the bus through software. But, if 4.19 is working, can you use 'git bisect' between the two kernels to find what caused the problem? thanks, greg k-h
