On 9/18/2019 04:38, JH wrote: ......
That was always my thought until I tried kernel 5.1 under the same platform (nothing changed except the kernel version), the kernel 5.1 can connect to the 4G modem, I could not tell the hardware engineer if it was hardware problem where kernel 5.1 can connect, kernel 4.19 could not, how would you explain it? Seems some differences between kernel 5.1 and kernel 4.19, what I could be missing?
Tell your hardware engineer to log the VBUS supply together with the current consumption of the 4G card. A glitch in the VBUS supply, often caused by an increase in current consumption is a common reason for a usb modem to reset and temporarily fall off the usb bus.
br Lars
