When using a Dell U2412M, the screen flickers and appears black every 30 seconds to 15 minutes.
This has only been seen with designs using the 4-byte interface to the Video PHY.
The issue is due to M/Nvid values that are transferred to the monitor.
These values are slightly different than what the monitor will tolerate and it causes the screen to flicker.
This issue is fixed in Vivado 2019.1 and later versions.
To implement the fix, update register 0x94 using the driver. This is shown highlighted below.
Driver update to write register 0x94: