The application relates to the technical field of communication, in particular to a device debugging method, a terminal device and an upper computer, the method is applied to a terminal device, the terminal device comprises an AP subsystem and an SP subsystem, the method comprises the following steps: when the SP subsystem detects that the AP subsystem is hung, switching a
universal asynchronous receiver transmitter (UART) interface to a
USB channel; the SP subsystem performs
handshaking with the upper computer through the
USB channel; the SP subsystem performs command interaction with the upper computer through the
USB channel, so as to perform transmission of
system data between the SP subsystem and the upper computer. The embodiment of the application realizes efficient and complete transmission of
system data in the hung state.