AMD Finally Rolls Out New Linux Patches For Adaptive-Sync / VRR (FreeSync)
Written by Michael Larabel in Radeon on 11 September 2018 at 12:42 PM EDT. 64 Comments
RADEON --
While the open-source AMD Radeon Linux graphics stack has gotten into particularly good shape the past two years or so, one of the areas that has left the red Linux gamers unsatisfied is the lack of FreeSync support (or DisplayPort Adaptive-Sync / HDMI Variable Refresh Rate) when using the fully open-source stack. It looks like that could be changing soon with the new set of patches under review.

AMD has provided FreeSync support for a few years when using their AMDGPU-PRO hybrid driver, but not many gamers rely upon that packaged driver over the latest open-source drivers these days... There have been open-source FreeSync patches previously, which were once held up by the AMDGPU DAL/DC bits landing and enabled by default. But most recently the mainlining of this FreeSync/Adaptive-Sync/VRR functionality was held up on ensuring their proposed DRM (Direct Rendering Manager) API for handling the DisplayPort/HDMI standards were acceptable to the other driver developers, namely the open-source Intel driver developers.

In case you are late to the party, Adaptive-Sync / VRR are the industry standards now for variable refresh rates to reduce/avoid stuttering, tearing, and/or input lag. Supporting this by the open-source Linux graphics drivers needs bit in the kernel space (DRM) as well as within Mesa, the X.Org DDX driver, and Mesa.

AMD developer Nicholas Kazlauskas sent out the newest DRM API patches on Tuesday for supporting Adaptive-Sync / Variable Refresh Rate. The new API is added as atomic properties to the DRM connector and CRC for indicating if "variable refresh" is capable or enabled.

AMD has patches plumbed but not yet mainlined for getting this support going with their hardware and under an X.Org Server session (no Wayland). The properties can be set/queried using xrandr.


Yes, you do also need a supported display in order to enjoy this technology to reduce stuttering, input lag, and tearing.


These newest patches can be found on the dri-devel list. Let's cross our fingers that the kernel bits will happen for Linux 4.20~5.0 and that the user-space bits will all be aligned shortly thereafter for delivering on this long-awaited functionality.
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Michael Larabel is the principal author of Phoronix.com and founded the site in 2004 with a focus on enriching the Linux hardware experience. Michael has written more than 10,000 articles covering the state of Linux hardware support, Linux performance, graphics drivers, and other topics. Michael is also the lead developer of the Phoronix Test Suite, Phoromatic, and OpenBenchmarking.org automated benchmarking software. He can be followed via Twitter or contacted via MichaelLarabel.com.

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