the drivers for the radeon hd 8790m are for some reason bugged.
i own a latidude e6540 and when ever i have gpu drivers downloaded from amd whenever i'm trying to use the gpu its stuck in its low power state
when i'm using the 2015 drivers from dell it works fine but i need updated drivers for software
If you haven't done so, I would update the Laptop's BIOS and CHIPSET. Especially the BIOS which the latest version is considered to be "Urgent".
For the latest AMD Graphics driver to work you must have the latest Intel APU Driver installed. There is are newer Drivers for the year 2018 & 2019 for your laptop. I would update at least all Intel Drivers and CHIPSET and BIOS to the latest versions. Then see if your laptop work better.
Here is the Dell Support Download page for your laptop: Support for Latitude E6540 | Drivers & downloads | Dell US
AMD Forum procedure to update an Intel APU Laptop with AMD Graphic Drivers: Laptop graphics update...How to
and how to configure your Intel Laptop: Configuring Laptop Switchable Graphics on a Windows® Based System | AMD