Last year, we noted how the long-standing vagaries of HDMI licensing and open source AMD driver development combined to prevent the upcoming Steam Machine from receiving official support for the HDMI 2.1 display standard. Now, though, it seems that AMD is making real progress on adding full HDMI 2.1 compliance to its Linux amdgpu driver in the near future.
In patch series notes for an amdgpu driver update posted on Friday (and noticed by Phoronix), AMD’s Harry Wentland says that the company is finally adding HDMI FRL (Fixed Rate Link) support to the popular Linux display driver. That’s the feature that allows for higher bandwidth on compatible HDMI cables compared to the TMDS standard found on HDMI 2.0 and earlier. That in turn enables direct support for higher resolutions, dynamic HDR, and features like Variable Refresh Rate that aren’t supported in HDMI 2.0.
Wentland notes that this update is still just “a representative subset of HDMI compliance,” in part because it is missing the code to support the Display Stream Compression (DSC) that allows for even higher resolutions and frame rates up to 10K at 100 Hz. But Wentland adds that DSC support “is still being tested and will be sent out later,” and that “a full compliance run” for HDMI 2.1 is “in the works.” An AMD driver developer with the handle agd5f also commented on Phoronix, noting that “a full implementation [of HDMI 2.1] will ultimately be available once the patches are ready and have completed compliance testing.”
This is all good news for Steam Machine buyers and other Linux gamers who want to finally make use of high-end display features that were first standardized in 2017. Valve says it has been using workarounds like chroma subsampling and AMD Freesync support to squeeze better Steam Machine performance out of the HDMI 2.0 bandwidth currently supported by AMD’s Linux drivers. The coming introduction of full HDMI 2.1 support in amdgpu should obviate the need for those workarounds, though.
It’s unclear whether the HDMI Forum’s original legal issues with any open source implementation of HDMI 2.1 have been resolved or if that organization will allow Linux devices to advertise as HDMI 2.1-compliant (we’ve reached out to the HDMI Forum for comment). For now, though, it seems clear that AMD is finally comfortable adding the HDMI 2.1 features it says have been ready and waiting to its Linux drivers for years now. In December, Valve said that “we’ve been working on trying to unblock things” regarding AMD drivers, and it’s nice to see those efforts finally bearing fruit on AMD’s side.
