https://bugs.freedesktop.org/show_bug.cgi?id=73528
--- Comment #25 from Marek Olšák maraeo@gmail.com --- My explanations for this bug are:
1) CMASK allocation is wrong. We should try and overallocate it.
2) CMASK contains garbage, which can hang the hardware. Either the clear_buffer function isn't reliable (it uses CP DMA) or CMASK was corrupted by eviction. Or an out-of-bounds access from some other source corrupted it.