drm/sched: Reverse run-queue priority enumeration

Reverse run-queue priority enumeration such that the higest priority is now 0,
and for each consecutive integer the prioirty diminishes.

Run-queues correspond to priorities. To an external observer a scheduler
created with a single run-queue, and another created with
DRM_SCHED_PRIORITY_COUNT number of run-queues, should always schedule
sched->sched_rq[0] with the same "priority", as that index run-queue exists in
both schedulers, i.e. a scheduler with one run-queue or many. This patch makes
it so.

In other words, the "priority" of sched->sched_rq[n], n >= 0, is the same for
any scheduler created with any allowable number of run-queues (priorities), 0
to DRM_SCHED_PRIORITY_COUNT.

Cc: Rob Clark <robdclark@gmail.com>
Cc: Abhinav Kumar <quic_abhinavk@quicinc.com>
Cc: Dmitry Baryshkov <dmitry.baryshkov@linaro.org>
Cc: Danilo Krummrich <dakr@redhat.com>
Cc: Alex Deucher <alexander.deucher@amd.com>
Cc: Christian König <christian.koenig@amd.com>
Cc: linux-arm-msm@vger.kernel.org
Cc: freedreno@lists.freedesktop.org
Cc: dri-devel@lists.freedesktop.org
Signed-off-by: Luben Tuikov <ltuikov89@gmail.com>
Reviewed-by: Christian König <christian.koenig@amd.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20231124052752.6915-6-ltuikov89@gmail.com

1 files changed, 3 insertions, 2 deletions

diff --git a/drivers/gpu/drm/scheduler/sched_entity.c b/drivers/gpu/drm/scheduler/sched_entity.c
index dd2b8f777f51..3c4f5a392b06 100644
--- a/drivers/gpu/drm/scheduler/sched_entity.c
+++ b/drivers/gpu/drm/scheduler/sched_entity.c
@@ -82,13 +82,14 @@ int drm_sched_entity_init(struct drm_sched_entity *entity,
 		pr_warn("%s: called with uninitialized scheduler\n", __func__);
 	} else if (num_sched_list) {
 		/* The "priority" of an entity cannot exceed the number of run-queues of a
-		 * scheduler. Protect against num_rqs being 0, by converting to signed.
+		 * scheduler. Protect against num_rqs being 0, by converting to signed. Choose
+		 * the lowest priority available.
 		 */
 		if (entity->priority >= sched_list[0]->num_rqs) {
 			drm_err(sched_list[0], "entity with out-of-bounds priority:%u num_rqs:%u\n",
 				entity->priority, sched_list[0]->num_rqs);
 			entity->priority = max_t(s32, (s32) sched_list[0]->num_rqs - 1,
-						 (s32) DRM_SCHED_PRIORITY_LOW);
+						 (s32) DRM_SCHED_PRIORITY_KERNEL);
 		}
 		entity->rq = sched_list[0]->sched_rq[entity->priority];
 	}