Until now ttm stored a single pipelined eviction fence which means
drivers had to use a single entity for these evictions.
To lift this requirement, this commit allows up to 8 entities to
be used.
Ideally a dma_resv object would have been used as a container of
the eviction fences, but the locking rules makes it complex.
dma_resv all have the same ww_class, which means "Attempting to
lock more mutexes after ww_acquire_done." is an error.
One alternative considered was to introduced a 2nd ww_class for
specific resv to hold a single "transient" lock (= the resv lock
would only be held for a short period, without taking any other
locks).
The other option, is to statically reserve a fence array, and
extend the existing code to deal with N fences, instead of 1.
The driver is still responsible to reserve the correct number
of fence slots.
Signed-off-by: Pierre-Eric Pelloux-Prayer <pierre-eric.pelloux-prayer@amd.com>
Link: https://lore.kernel.org/r/20251121101315.3585-20-pierre-eric.pelloux-prayer@amd.com
Reviewed-by: Christian König <christian.koenig@amd.com>
Signed-off-by: Christian König <christian.koenig@amd.com>
ddf055b80a