Seems that hang handling wasn't implemented at all for some GPU's:
https://cgit.freedesktop.org/~agd5f/linux/commit/drivers/gpu/drm/amd?h=amd-staging-4.7&id=196cbffe7a4e23ad672b25a4226e53ea5479166c

I haven't yet tried playing TF2 with amd-staging-4.7 (though I have been using
it for a few days). I'll try it this morning.