drm/nouveau/imem: support allocations not preserved across suspend

Will initially be used to tag some large grctx allocations which don't
need to be saved, to speedup suspend/resume.

Signed-off-by: Ben Skeggs <bskeggs@redhat.com>
Reviewed-by: Lyude Paul <lyude@redhat.com>
Acked-by: Danilo Krummrich <me@dakr.org>
Signed-off-by: Lyude Paul <lyude@redhat.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20230919220442.202488-3-lyude@redhat.com

drm/nouveau/fb: protect comptags with private mutex

nvkm_subdev.mutex is going away.

Signed-off-by: Ben Skeggs <bskeggs@redhat.com>
Reviewed-by: Lyude Paul <lyude@redhat.com>

drm/nouveau/core/memory: remove redundant assignments to variable ret

The variable ret is being initialized with a value that is never
read and it is being updated later with a new value. The initialization
is redundant and can be removed.

Addresses-Coverity: ("Unused value")
Signed-off-by: Colin Ian King <colin.king@canonical.com>
Signed-off-by: Ben Skeggs <bskeggs@redhat.com>

drm/nouveau/mmu: fix comptag memory leak

Signed-off-by: Ben Skeggs <bskeggs@redhat.com>

drm/nouveau/core/memory: fix missing mutex unlock

Signed-off-by: Ben Skeggs <bskeggs@redhat.com>

drm/nouveau/core/memory: add reference counting

We need to be able to prevent memory from being freed while it's still
mapped in a GPU's address-space.

Will be used by upcoming MMU changes.

Signed-off-by: Ben Skeggs <bskeggs@redhat.com>

drm/nouveau/core/memory: comptag allocation

nvkm_memory is going to be used by the upcoming mmu rework for the basic
representation of a memory allocation, as such, this commit adds support
for comptag allocation to nvkm_memory.

This is very simple for now, in that it requires comptags for the entire
memory allocation even if only certain ranges are compressed.

Support for tracking ranges will be added at a later date.

Signed-off-by: Ben Skeggs <bskeggs@redhat.com>

drm/nouveau/imem: convert to new-style nvkm_subdev

Signed-off-by: Ben Skeggs <bskeggs@redhat.com>

drm/nouveau/imem: improve management of instance memory

Signed-off-by: Ben Skeggs <bskeggs@redhat.com>