https://bugs.freedesktop.org/show_bug.cgi?id=91880
--- Comment #58 from Julian jsbansen@gmail.com --- In case anyone is interested, I've hacked together a GNOME extension that adds a status icon showing the current DPM setting and a popup menu to easily switch: https://github.com/JuBan1/radeon-dpm-control.git
It only handles three combinations of settings: low/battery, auto/balanced, high/performance. I don't think the others are particularly useful.
It makes use of Thomas DEBESSE's dpm-query script a few comments earlier.