Firmware update method having self-restoration mechanism

A firmware update method having a self-restoration mechanism and being performed by a server and a terminal device cooperatively, the firmware update method comprising:

• using the server to obtain to-be-upgraded firmware that is equal to or equivalent to current firmware of the terminal device, and obtain target firmware;
• using the server to perform a first differential operation to the to-be-upgraded firmware based on the target firmware, and thereby generating a differential upgrade package;
• using the server to perform a second differential operation to the target firmware based on the to-be-upgraded firmware, and thereby generating a differential restoration package;
• using the terminal device to download the differential upgrade package and the differential restoration package through a communication channel;
• using the terminal device to perform an upgrade operation to the current firmware of the terminal device with the differential upgrade package so as to upgrade the current firmware to the target firmware, wherein the current firmware is changed into incompletely-upgraded firmware after the upgrade operation starts and before the upgrade operation finishes successfully;
• and
• using the terminal device to verify whether the upgrade operation fails, and when the upgrade operation fails, using the terminal device to perform a restoration operation to the incompletely-upgraded firmware with backup of partial data of the current firmware and/or with the differential restoration package so as to restore the incompletely-upgraded firmware to the current firmware.