AMD Linux Graphics Driver Prepping "DMCUB" Support For Renoir APUs

While we have seen a lot of open-source AMD Linux graphics driver patches for Renoir and that initial support within the 5.4 kernel, support for this 2020 APU platform is still maturing. The newest work on the Linux upbringing for Renoir is enabling the "DMCUB" support.

DMCUB is short for the "Display MicroController Unit B" and is used with this next-gen APU for handling real-time display features like Panel Self Refresh and Adaptive Backlight Management as well as initializing the display hardware. From the software side, the DMCUB support is shortened to being "DMUB."

Bringing up this new display micro-controller within the AMDGPU kernel driver is over three thousand lines of code, but a good portion of that is header files.

Besides the kernel patches, there are also new firmware binaries required by the Display MicroController Unit B.

The patches for now are on amd-gfx while there's still time for potentially seeing this material land in DRM-Next ahead of the Linux 5.5 cycle. Renoir APUs are expected in 2020 with Zen 2 CPU cores while continuing to make use of Vega graphics but with a new display engine and other improvements compared to Raven 2 / Picasso.