Radeon In Linux 3.11 Is Fantastic With PM, Sea Islands
The pull request for the Radeon DRM graphics driver changes for the Linux 3.11 kernel has been submitted. The open-source Radeon Linux graphics driver changes in this next kernel development cycle include dynamic power management (including ASPM) and support for Radeon HD 8000 "Sea Islands" graphics processors as the most prominent changes.
The massive dynamic power management work supports from the Radeon HD 2000 "R600" GPUs up through the HD 7000 "Southern Islands" hardware. The massive work inflates the size of the open-source Radeon DRM driver by more than 52 thousand lines of code over the course of one kernel release.
On Wednesday, Phoronix was the first to report on this massive Radeon Linux work. Dynamic power management has been a long-awaited feature of the open-source AMD Linux graphics driver for being able to lower energy consumption of systems running this Catalyst alternative, reduce the temperature of laptops and desktop systems, and just be more efficient.
The dynamic power management support right now provides clockgating, dynamic engine clock scaling, dynamic memory clock scaling, dynamic voltage scaling, and dynamic PCI Express Gen1/Gen2 switching. While this is great, in the Linux 3.11 kernel "DPM" isn't enabled by default. The system needs to be booted with radeon.dpm=1 for enabling dynamic power management.
AMD's Alex Deucher says that it will be off by default until further testing has been completed. The dynamic power management is also reported to be problematic for the R600 (HD 2000) and Norther Islands (HD 6000) graphics cards while other g enerations should be in good shape. Updated Radeon microcode/firmware is also needed by the open-source driver for DPM to work.
Looking forward to the AMD graphics cards launching in a few months time, there's the initial kernel support for Radeon HD 8000 "Sea Islands" / "CIK" graphics cores. This initial support provides the kernel bits for 3D/OpenGL, GPGPU/Compute, and UVD video decoding. There's still Radeon HD 8000 Sea Islands Mesa/Gallium3D patches to be merged in user-space, which will extend the RadeonSI Gallium3D driver, but this is just the kernel bits. It's really great to see AMD finally getting in new hardware ASIC support prior to the public debut.
In between all of the exciting new features, there's also many bug-fixes to be found in the Radeon DRM code with hopefully not too many new regressions.
The Radeon DRM 3.11 changes for the drm-next tree pull request can be found on the dri-devel list.
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