AMD Developers Discuss Better Switching Of Radeon/AMDGPU CIK Support
Written by Michael Larabel in Radeon on 11 April 2017 at 01:02 PM EDT. 62 Comments
RADEON --
Open-source AMD developers have been discussing in recent days how to better deal with the experimental support of GCN 1.1 "Sea Islands" (and GCN 1.0 "Southern Islands") support in AMDGPU and making it easier to enable while ensuring the Radeon DRM driver with its mature GCN 1.0/1.1 support doesn't interfere.

The work up to now has been about trying to "harmonize CIK ASIC support in Radeon and AMDGPU." The main way to do this has been trying to unify the CIK (and SI could be done similarly, if approved) using Kconfig switches to decide which DRM driver (Radeon vs. AMDGPU) should default to for CIK hardware.

With the current Kconfig tunables at build time, you can enable the CIK/SI switches for AMDGPU, but the Radeon DRM driver might still end up claiming the cards before the AMDGPU driver. So to workaround that case right now, you usually have to blacklist the Radeon DRM driver or instead build the modified kernel without the Radeon DRM present. The new tunables would make it easier to select the desired behavior of which driver should be the default for the AMD GPUs supported by both drivers.

Alternative approaches being considered are always compiling CIK support in AMDGPU and then just have a Kconfig switch to choose the default Radeon vs. AMDGPU for the hardware, in order to reduce the number of exposed Kconfig switches. Another possibility would be having a kernel command-line switch to toggle the desired driver.

The discussion about this can be found in this amd-gfx thread among other discussions. So the matter is still very much up in the air right now, but we'll see what comes about. Regardless, the changes would be too late for Linux 4.12 DRM-Next so this is material likely ending up for Linux 4.13. Hopefully with these proposed changes is indication of some potential interest by AMD in pushing more CIK Radeon users onto AMDGPU.

In case you missed it, last week I posted some fresh AMDGPU vs. Radeon DRM With GCN 1.0/1.1 GPUs On Linux 4.11, Mesa 17.1-dev.
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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 10,000 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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