drm/nouveau: implement 1:1 scheduler - entity relationship

Recent patches to the DRM scheduler [1][2] allow for a variable number
of run-queues and add support for (shared) workqueues rather than
dedicated kthreads per scheduler. This allows us to create a 1:1
relationship between a GPU scheduler and a scheduler entity, in order to
properly support firmware schedulers being able to handle an arbitrary
amount of dynamically allocated command ring buffers. This perfectly
matches Nouveau's needs, hence make use of it.

Topology wise we create one scheduler instance per client (handling
VM_BIND jobs) and one scheduler instance per channel (handling EXEC
jobs).

All channel scheduler instances share a workqueue, but every client
scheduler instance has a dedicated workqueue. The latter is required to
ensure that for VM_BIND job's free_job() work and run_job() work can
always run concurrently and hence, free_job() work can never stall
run_job() work. For EXEC jobs we don't have this requirement, since EXEC
job's free_job() does not require to take any locks which indirectly or
directly are held for allocations elsewhere.

[1] https://lore.kernel.org/all/8f53f7ef-7621-4f0b-bdef-d8d20bc497ff@redhat.com/T/
[2] https://lore.kernel.org/all/20231031032439.1558703-1-matthew.brost@intel.com/T/

Signed-off-by: Danilo Krummrich <dakr@redhat.com>
Reviewed-by: Dave Airlie <airlied@redhat.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20231114002728.3491-1-dakr@redhat.com

1 files changed, 5 insertions, 13 deletions

diff --git a/drivers/gpu/drm/nouveau/nouveau_abi16.c b/drivers/gpu/drm/nouveau/nouveau_abi16.c
index 2edd7bb13fae..7542e1787183 100644
--- a/drivers/gpu/drm/nouveau/nouveau_abi16.c
+++ b/drivers/gpu/drm/nouveau/nouveau_abi16.c
@@ -127,21 +127,14 @@ nouveau_abi16_chan_fini(struct nouveau_abi16 *abi16,
 {
 	struct nouveau_abi16_ntfy *ntfy, *temp;
 
-	/* When a client exits without waiting for it's queued up jobs to
-	 * finish it might happen that we fault the channel. This is due to
-	 * drm_file_free() calling drm_gem_release() before the postclose()
-	 * callback. Hence, we can't tear down this scheduler entity before
-	 * uvmm mappings are unmapped. Currently, we can't detect this case.
-	 *
-	 * However, this should be rare and harmless, since the channel isn't
-	 * needed anymore.
-	 */
-	nouveau_sched_entity_fini(&chan->sched_entity);
+	/* Cancel all jobs from the entity's queue. */
+	drm_sched_entity_fini(&chan->sched.entity);
 
-	/* wait for all activity to stop before cleaning up */
 	if (chan->chan)
 		nouveau_channel_idle(chan->chan);
 
+	nouveau_sched_fini(&chan->sched);
+
 	/* cleanup notifier state */
 	list_for_each_entry_safe(ntfy, temp, &chan->notifiers, head) {
 		nouveau_abi16_ntfy_fini(chan, ntfy);
@@ -344,8 +337,7 @@ nouveau_abi16_ioctl_channel_alloc(ABI16_IOCTL_ARGS)
 	if (ret)
 		goto done;
 
-	ret = nouveau_sched_entity_init(&chan->sched_entity, &drm->sched,
-					drm->sched_wq);
+	ret = nouveau_sched_init(&chan->sched, drm, drm->sched_wq);
 	if (ret)
 		goto done;