Intel Lands Adaptive-Sync/VRR Into Modesetting X.Org Driver

Written by Michael Larabel in Intel on 8 September 2020 at 09:41 AM EDT. 1 Comment
With Intel Gen11 graphics and newer supporting Adaptive-Sync / Variable Refresh Rate for minimizing tearing and stuttering, their open-source developers have now added the necessary bits to the generic xf86-video-modesetting X.Org driver for supporting the VRR functionality.

Months ago they posted the VRR patches for xf86-video-modesetting while now the patches have been merged to X.Org Server Git. These patches in turn are based on AMD's FreeSync/VRR support they added to the xf86-video-amdgpu driver.

With xf86-video-intel effectively being dead and unmaintained, xf86-video-modesetting is the X.Org driver in use on Intel paired with their kernel mode-setting driver. While their kernel-side work is still being settled, the X.Org DDX bits are now merged. This can benefit AMD Radeon Linux users as well who want to enjoy VRR when using xf86-video-modesetting rather than the xf86-video-amdgpu DDX.

While the xf86-video-modesetting driver is "generic" to KMS drivers, this VRR support isn't magic and does require the hardware/drivers with the KMS/DRM kernel code as well as the Mesa driver to properly support variable refresh rate. If those pieces don't support VRR, xf86-video-modesetting's option won't work with a given system.

The support was merged today to xserver Git. Besides needing to be using the very latest Git code, a new VariableRefresh xorg.conf option is added for flipping on the VRR support for a given output.

But as for when this X.Org Server / xf86-video-modesetting code will actually ship in a released version is currently unknown... The Git code is still tracking X.Org Server 1.21 that has now been in development about two and a half years, well off their prior six month release schedule. So far no one has managed to step up to serve as the xorg-server 1.21 release manager given Red Hat's diminishing interest in X.Org Server duties in favor of a Wayland-focused Linux desktop. So at this stage X.Org Server 1.21 might not materialize until 2021 but we'll see if these VRR patches end up being back-ported to a 1.20.x point release in the interim.
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