Nouveau Can Do OpenCL Compute For Open-Source NVIDIA
This past weekend at FOSDEM 2012 in Brussels was a presentation by Francisco Jerez concerning OpenCL support for the reverse-engineered open-source NVIDIA graphics driver. Francisco is the developer that the X.Org Foundation has been paying to do some OpenCL work since none of the open-source Linux graphics drivers have supported this GPGPU technology yet.
At the end of last month Francisco reported on his OpenCL code nearing a working state while at FOSDEM he shared that the initial NV50 code for OpenCL is in fact working -- he then showed off the OpenCL-Nouveau support working with clinfo and then a few OpenCL demos on Linux with this unofficial graphics card driver.
The Nouveau NV50 driver is what handles the GeForce 8/9/100/200/300 series, but not the newer GeForce 400/500 "Fermi" graphics cards. OpenCL support there is still much more early on with the developers still working out other Fermi features and bugs.
The community-spawned OpenCL support within Nouveau takes advantage of the earlier work done by Zack Rusin on the Clover state tracker for Gallium3D in recent years and then this past year during the work done as part of Google's Summer of Code. With the Clover/OpenCL state tracker for Gallium3D, LLVM/Clang is used as the OpenCL compiler.
While AMD has been paying for open-source OpenCL love and the open-source Radeon OpenCL support is still behind and not ready for showing off OpenCL demos, Nouveau NV50 doing OpenCL is quite an achievement. Intel's Open-Source Technology Center team working on graphics also hasn't been up to anything with OpenCL since they don't use the Gallium3D driver architecture and another Intel group offers a CPU-based closed-source OpenCL SDK.
PathScale is also another company that's been playing around with open-source OpenCL GPU-based acceleration using their fork of the Nouveau driver.
Among the work that's still left for Francisco or others to do with the Nouveau OpenCL support beyond supporting the latest-generation Fermi or upcoming Kepler graphics processors is still the need for an LLVM back-end for TGSI (the LLVM back-end in Nouveau is still a ways off so TGSI is being relied upon as the IR), DRM authentication support without an X.Org Server, and inter-GPU synchronization and resource sharing support. This will take a considerable amount of kernel work to do, as talked about during the hour-long presentation.
Unfortunately this current Nouveau OpenCL work done by Francisco Jerez isn't in the upstream Nouveau code-base but rather a separate branched Git repository. This is still out-of-tree work and it's not clear when it will be merged, but is already out of the question for the soon-to-be-out Mesa 8.0. The next hope would be seeing Mesa 8.1 be more OpenCL compute friend when that arrives in the middle of 2012.
The Nouveau camp also still has other significant problems to worry about besides just implementing OpenCL support across the spectrum of NVIDIA hardware, but regardless seeing the OpenCL demos first-hand this weekend was quite impressive.
For those wanting to learn more about the ongoing OpenCL Nouveau work, embedded below is a video I recorded from the Brussels presentation.