The aforelinked article goes over all the basic AMD HSA Linux driver details while its the AMD-specific HSA driver that's being worked on the most and discussed. Version two of the "AMDKFD" driver came out on Thursday and lives under the DRM Radeon GPU driver as the "AMDKFD" to provide the "HSA kernel driver for AMD Radeon devices."
The "v2" batch of 25 patches that work towards the AMD Radeon implementation of the Heterogeneous System Architecture for the Linux kernel can be found on the dri-devel list. The AMDKFD driver has yet to be queued up in drm-next (or the staging area) so it's not yet known whether or not this open-source HSA driver will premier in time for the Linux 3.17 kernel.
Stay tuned for more updates and tests as the AMD HSA open-source implementation evolves.