Radeon Navi Support Pending For RadeonSI OpenGL Driver With 47k Line Worth Of Changes

Last week AMD posted more than 400 patches providing the AMD Navi support within their AMDGPU DRM kernel driver while this week has brought dozens of patches amounting to 4,293 lines as a patch for their RadeonSI Gallium3D driver in order to provide OpenGL support on these next-gen GPUs being introduced next month as the Radeon RX 5700 series.

Well known AMD open-source developer Marek Olšák posted the Mesa patches yesterday for providing this initial Navi (10) support to Mesa. As is the case, AMD's Navi enablement is focused on the RadeonSI Gallium3D driver and not the unofficial/community driven RADV Radeon Vulkan driver also within Mesa. The RADV Navi support will be left up to those "community" contributors from the likes of Red Hat, Google, and yes the independent community members.

With the MR for the AMD Navi support in RadeonSI, it was interesting to note some of the driver changes by Marek:

- The GS stage is used instead of VS. GS is now a merged ES-GS-VS and is more efficient. In this mode, API shaders VS, TES, and GS are said to be compiled as NGG.
- Transform feedback is completely emulated with the help of GDS ordered atomics. Transform feedback queries have to be emulated too. (it might still be faster than the previous hw)

As of writing, the merge request hasn't been honored but the code is expected to make it into Mesa 19.2 that won't be under feature freeze for another month. Mesa 19.2 should then debut as stable at the end of August or early September with this Navi support.

It's what I have been saying for a while now, but it's looking like Linux 5.3 + Mesa 19.2 + LLVM 9.0 all due to be released around September will be the versions to target for the initial Radeon Navi support. There's also a libdrm update that will also be part of the support matrix.

AMD can be congratulated for getting this code out ahead of their 7 July launch for the Radeon RX 5700/5700XT though unfortunate at the same time it won't be shipping in stable releases of those key components in time for launch day. As we've come to find out, Navi brings a fair amount of architectural changes and there's always the legal/IP reviews and other steps involved in the open-source code process.

Stay tuned on 7 July for our Linux benchmarks of the Radeon RX 5700 and RX 5700XT along with the new Ryzen products.