On this model, that's done through software (the nVidia control panel) -- not firmware.  
I m looking for ways to disable GPU in bios for my dell G15 5520 laptop in order to save power consumption since I do not need GPU all the time ( typical usage - programming in python , web browsing , reading online books) . If any one knows a way to disable GPU in bios , please let me know
Dell g15 5520 gaming laptop - how to disable GPU in bios