With AMDGPU DC Not Aligning For Linux 4.14, 120 More Display Code Patches
Written by Michael Larabel in AMD on 9 August 2017 at 11:49 AM EDT. 45 Comments
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It's looking almost certain that AMDGPU's display code (a.k.a. "DC" and "DAL") will not be merged for the next Linux 4.14 cycle, but work on this massive display code-base is progressing and 120 more patches were published today.

AMDGPU DC for Linux 4.14 is looking increasingly unlikely considering Linux 4.13-rc4 was released this past weekend and this display code is not yet queued in DRM-Next let alone AMD's -next tree. David Airlie cuts merging off new feature material for the next kernel cycle around ~RC6 of the previous series, thus new feature work will be cut off for Direct Rendering Manager drivers for Linux 4.14 within about two weeks. But with the display code not being queued yet and the massive patch-set not having been sent out for for a public review on dri-devel by other upstream kernel developers, given the size of the code-base it's almost impossible for it to be reviewed within two weeks.

AMDGPU DC is up to 600+ patches with around 160k lines of new code to show just how complex this new display code is for this modern AMD Linux kernel graphics driver. And now today it gets 120 more patches.

AMD developer Harry Wentland posted to amd-gfx a short time ago, "A whole lot of stuff this time around because it's Raven crunchtime and a bunch of us found time to keep massaging DC in DRM's image." Raven Ridge is the upcoming APU launch expected around year's end to feature a Zen CPU microarchitecture with Vega class graphics.

These 120 patches have more Raven Ridge work plus more DC code cleaning to better align the display code's concepts with those used by the DRM subsystem in the Linux kernel. There is more flattening (less abstractions) around core/DC objects, renaming of some code, and a ton of other code changes and more bug fixes for Raven. Reducing the abstractions in the code is certainly good as that was one of the original big complaints with the driver's code back when it was published as DAL.

They are certainly moving in the right direction, but it looks like we probably won't see this mainlined until at least Linux 4.15. If you want AMDGPU DC today for either HDMI/DP audio, Radeon RX Vega display support, or other sought-after modern display features, the easiest way is to install AMDGPU-PRO (assuming you are on a supported distribution) or build the current AMDGPU staging tree that is currently based against Linux 4.12.
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Michael Larabel is the principal author of Phoronix.com and founded the site in 2004 with a focus on enriching the Linux hardware experience. Michael has written more than 20,000 articles covering the state of Linux hardware support, Linux performance, graphics drivers, and other topics. Michael is also the lead developer of the Phoronix Test Suite, Phoromatic, and OpenBenchmarking.org automated benchmarking software. He can be followed via Twitter or contacted via MichaelLarabel.com.

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