Here you can download Spreadtrum SC7731 based PAC Stock Firmware for the Walton Primo EF4 device. The downloadable file High Compressed in an archive, You will get the Flash File after extraction. Included contains Flash Tool, USB Driver, and how-to Flash manual instructions.
[*] Chipset: Spreadtrum SC7731.
[*] Driver: SPD SCI Android USB Driver.
[*] Flash Tool: SPD Upgrade Tool.
Firmware for Walton EF4
Build Number: Primo_EF4_S007_05092016
Android Version: v6.0 (Marshmallow)
Download Size: 629 MB
Walton Primo EF4 Flash Tool & USB Driver
Flash Tool for Walton Primo EF4
Walton Primo EF4 USB Driver
[*] Backup: During the flashing process SPD Flash Tool will erase user data from the phone. So you need to backup for restoring those files on your device.
[*] Device Information: The Walton Primo EF4 phone powered by Spreadtrum SC7731 CPU. So you need to use SPD Flash Tools to and SPD USB Driver flash Firmware on this device.
[*] Flashing Information: You can try different types of SPD Flash Tools to flash this Pac file if you see any of them show interrupted in flashing. The following Tools are Upgrade Download, Research Download, and Factory Download.