Fclkboostfreq - "Used for MALL performance boost"
I finally found what the acronym MALL stands for, from this article:
https://www.phoronix.com/scan.php?page=news_item&px=Radeon-Big-Navi-MALL-Linux
"One of these late feature additions for Sienna Cichlid is the "MALL" display feature. MALL in this context is the
Memory Access at Last Level. This Memory Access At Last Level is a DCN 3.0 feature for enhancing power savings with the screen contents coming from the "MALL" when certain conditions are met."
[..]
It appears that Fclkboostfreq is a threshold related to power savings. I
assume that below the threshold, power saving features are enabled, and above, power saving features are disabled. [..]