Valve’s incoming Steam Machine gaming PC/console drew new attention to one long‑standing weakness of the Linux ecosystem: HDMI 2.1 support. It works with Nvidia hardware (thanks to closed‑source drivers and firmware), but the open‑source drivers used for Radeon GPUs could not support it because the HDMI Forum did not allow HDMI 2.1 support in open‑source code. However, it looks like this problem may finally be coming to an end.
The lack of HDMI 2.1 support for AMD GPUs on Linux has been a persistent issue ever since the Radeon RX 6000 series launched, and it continues with newer GPUs. The HDMI Forum, which develops and maintains HDMI, was unwilling to approve support in open‑source drivers (the specification itself is not open). AMD actually developed an implementation back in 2023 that the company believed could enable HDMI 2.1 features while complying with licensing requirements, but the solution was not accepted at the time.
Until now, AMD GPU users on Linux could only use HDMI ports in HDMI 2.0 mode—with lower maximum resolutions and refresh rates—and they also lacked HDMI 2.1 variable refresh rate support. The only workaround was using active DisplayPort 2.1 adapters, which often do not work perfectly.
But yesterday, Phoronix reported that the situation may be changing. AMD has begun publishing patches that add HDMI 2.1 implementation to Linux and the AMDGPU driver (the open‑source Radeon GPU driver).
The first kernel patches add support for the FRL transmission mode, the faster communication mode used by HDMI 2.1. It enables bandwidth up to 48 Gb/s and support for 8K displays. This is one of the key features that distinguishes HDMI 2.1 from HDMI 2.0.
The HDMI 2.1 implementation may include more than just FRL — potentially it could offer full or nearly full support (except for HDCP content protection, which likely cannot be included in open‑source code for technical reasons). According to AMD employees, more patches will be submitted as the code is finalized. FRL support is only the beginning.
According to AMD, the implementation in these patches has passed the HDMI compliance tests relevant to FRL support, and full certification across the entire test suite is underway. AMD says this code was prepared years ago—making it likely that the same implementation rejected in 2023 is now finally landing. It appears AMD has finally convinced the HDMI Forum that the solution complies with licensing requirements and can be added to Linux. Demand from Valve and other handheld manufacturers who want Linux on their devices may also have helped.
It seems that one of the long‑standing annoyances AMD GPU users on Linux faced—both in gaming and productivity—will finally be resolved. It took a long time, but better late than never. This should also mean that the Valve Steam Machine could eventually launch with HDMI 2.1 support, avoiding issues with connecting TVs at higher refresh rates and resolutions. However, it is possible that this support will arrive some time after launch and not be available on day one.
It’s hard to predict when these patches will land in the mainline kernel and when the functionality will make its way into the kernels used by mainstream Linux distributions. It may still take many months (and it will naturally depend on each distribution’s policy regarding how quickly they ship new kernels to users).
Sources: Phoronix (1, 2), Kernel.org
English translation and edit by Jozef Dudáš
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