Proprietary drivers 331.89 do not give me OpenCL. (tried both tested/updates)
for a while I had version 304.123 that worked - except I wanted the current drivers, and now are unable to downgrade.
Anyway - I could downgrade by workaround, but I wish 331.89 worked.
I used "darktable -d opencl" as test
alos added symbolic link to darktable, but that does not help with 331.89