DC dimming is often used to modulate LED brightness in professional or business environments. It involves switching a DC input from between 0 and 10 volts. OPPO claims to have integrated it into the display panel of the upcoming Reno range of phones, although it may be more software-based than the typical implementation.
https://www.notebookcheck.net/OPPO-claims-the-upcoming-Reno-will-have-a-DC-dimming-function.415647.0.html
This is peculiar, last time I checked it was hardware, supposedly an additional control chip on the motherboard because the DC complicated with individual subpixel control of an OLED screen overwhelms the IC. Even if this is ultimately implemented it should result in higher idle power draw, and if always on display remains available it should fall back to the IC for driving pixels in that mode.