Hey,
Den 2025-11-21 kl. 16:12, skrev Christian König:
On 11/21/25 11:12, Pierre-Eric Pelloux-Prayer wrote:
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.
v2:
- simplified code
- dropped n_fences
- name changes
v3: use ttm_resource_manager_cleanup
Signed-off-by: Pierre-Eric Pelloux-Prayer pierre-eric.pelloux-prayer@amd.com
Reviewed-by: Christian König christian.koenig@amd.com
Going to push separately to drm-misc-next on Monday.
Pushing this broke drm-tip, the amd driver fails to build, as it's not using the eviction_fences array.
Kind regards, ~Maarten Lankhorst