Most of you are probably already aware of AMD FreeSync, a variable refresh rate feature that is available in select AMD graphics cards. The technology eliminates screen tearing by synchronizing the monitor’s refresh rate with the output of frames produced by the graphics card, resulting in a tear-free and fluid experience. The technology comes with no performance costs, which V-SYNC on the other hand is known for.
Ever since its launch in March 2015, over 42 monitor models from a variety of monitor manufacturers, such as Acer, EIZO, LG and Samsung, are now supporting the technology. For Linux users however, the technology has yet to be supported by AMD’s Linux drivers. Fortunately, AMD has now stated that Linux will soon be supported too, when the company releases their new AMDGPU DAL driver. The news originate from AMD’s Senior Software Engineer, Harry Wentland, who described the architecture in details in a message posted here.
The goal with DAL is to provide a unified, full featured display stack to service all of our Linux offerings. This driver will have to support our full feature set beyond what’s supported by amdgpu, e.g.
– synchronzied timings across different displays
– solid support of 6 displays in any configuration (HDMI, DVI, DP, DP MST, etc)
– solid support of 4k at 60 timings on APUs
– power features, such as
– clock-accurate bandwidth formulas
– improved interaction with powerplay to maximize power savings
– Improved audio and other infoframe related features
– Improved stability with powerplay since display hw is involved in the SMC hw interactions and improper programming sequences can lead to GPU hangs, etc.
The current amdgpu display stack grew somewhat organically and as such is not well suited to handling all of the hardware dependencies involved especially in areas like audio. The drm abstractions used by the old code map less and less well to new hw pipelines. Atomic helps, but if we are going to convert, it seemed like a good time to start fresh.
This is certainly good news for Linux users, but let’s wait and see to check if AMDGPU DAL gives us a flawless FreeSync experience or not.