[PATCH] drm/radeon: make 64bit fences more robust

[Dave Airlie]

>>>
>>>
>>>> It might be related to a hardware bug, or the algorithm is flawed in a
>>>> way I currently don't see. Anyway the old code we had wasn't so picky
>>>> about such problems and the patch just tries to make the current code as
>>>> robust as the old code was, which indeed seems to solve the problems we see.
>>>>
>>>> The wrap around detection still works (tested by setting the initial
>>>> fence value to 0xfffffff0 and letting it wrap around shortly after
>>>> start), so I think it we can safely commit this.

Can we start fences off so we wrap around after say 15-20 minutes?
that would ensure

a) its tested
b) we see failure in a lifetime.

Dave.