Running The Radeon Driver With GLAMOR
While the open-source ATI driver doesn't have some super fast 2D acceleration architecture equivalent to Intel's SNA or a developer making prolific contributions to the DDX, as of earlier this month the Radeon driver has support for GLAMOR.
GLAMOR is the OpenGL-based acceleration architecture that comes out of Intel as well, but namely the Intel China team. GLAMOR isn't some highly-optimized and large code-base within the DDX, but basically pipes the 2D calls over OpenGL with Mesa. There's a GLAMOR shared library that other 2D drivers can tap into with just a few hundred lines of code added into the respective driver's DDX. This is the approach that the AMD developers are using for 2D acceleration on the Radeon HD 7000 series rather than writing up a new EXA 2D implementation, but it also works just the same for previous generations of Radeon hardware.
Early Cairo-based benchmarks of Radeon GLAMOR by Chris Wilson have shown real promise for this open-source driver over Radeon EXA, since the Radeon driver's EXA implementation isn't the best. My tests on the Intel side of UXA vs. SNA vs. GLAMOR have shown that SNA is by far the best and usually GLAMOR is in a premature, shoddy state.
For those wishing to try out Radeon GLAMOR, it's unfortunately not as easy as just building the xf86-video-ati Git code with a special build switch for enabling the support.
The xf86-video-ati Git code must be built with the --enable-glamor switch and then at run-time within the xorg.conf there must be glamor set as the AccelMethod. However, prior to dealing with a Glamor'ized ATI driver, GLAMOR itself must first be setup.
For those wanting to know how to setup GLAMOR, there is documentation on its FreeDesktop.org web-site. Prior to building GLAMOR, at present Mesa must be rebuilt with certain parameters as well (enabling GBM, GLX TLS, and a shared GLAPI), which is covered on the page. Building and installing Glamor itself is quite straightforward and easy from its Git code.
When all of those components are setup, it should be possible to use the Radeon open-source Linux driver with the OpenGL-based GLAMOR rather than the conventional EXA. However, your mileage may vary. If you're a Radeon HD 7000 series owner, while this support is designed to be the default for these "Southern Islands" GPUs, that's not actually the case but ShadowFB is the default means of CPU-based acceleration since the RadeonSI driver isn't far enough along yet.
Radeon GLAMOR benchmarks will appear on Phoronix in the near future.
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