drm/sched: Add a basic test for modifying entities scheduler list

Add a basic test for exercising modifying the entities scheduler list at
runtime.

Signed-off-by: Tvrtko Ursulin <tvrtko.ursulin@igalia.com>
Cc: Christian König <christian.koenig@amd.com>
Cc: Danilo Krummrich <dakr@kernel.org>
Cc: Matthew Brost <matthew.brost@intel.com>
Cc: Philipp Stanner <phasta@kernel.org>
Acked-by: Christian König <christian.koenig@amd.com>
Signed-off-by: Philipp Stanner <phasta@kernel.org>
Link: https://patchwork.freedesktop.org/patch/msgid/20250324092633.49746-6-tvrtko.ursulin@igalia.com

drivers/gpu/drm/scheduler/tests/tests_basic.c

@@ -346,6 +346,73 @@ static struct kunit_suite drm_sched_priority = {
 	.test_cases = drm_sched_priority_tests,
 };
 
+static void drm_sched_test_modify_sched(struct kunit *test)
+{
+	unsigned int i, cur_ent = 0, cur_sched = 0;
+	struct drm_mock_sched_entity *entity[13];
+	struct drm_mock_scheduler *sched[3];
+	struct drm_mock_sched_job *job;
+	const unsigned int qd = 1000;
+
+	/*
+	 * Submit a bunch of jobs against entities configured with different
+	 * schedulers and while waiting for them to complete, periodically keep
+	 * changing schedulers associated with each entity.
+	 *
+	 * We set up the queue-depth (qd) and job duration so the sched modify
+	 * loop has some time to interact with submissions to the backend and
+	 * job completions as they progress.
+	 *
+	 * For the number of schedulers and entities we use primes in order to
+	 * perturb the entity->sched assignments with less of a regular pattern.
+	 */
+
+	for (i = 0; i < ARRAY_SIZE(sched); i++)
+		sched[i] = drm_mock_sched_new(test, MAX_SCHEDULE_TIMEOUT);
+
+	for (i = 0; i < ARRAY_SIZE(entity); i++)
+		entity[i] = drm_mock_sched_entity_new(test,
+						      DRM_SCHED_PRIORITY_NORMAL,
+						      sched[i % ARRAY_SIZE(sched)]);
+
+	for (i = 0; i < qd; i++) {
+		job = drm_mock_sched_job_new(test, entity[cur_ent++]);
+		cur_ent %= ARRAY_SIZE(entity);
+		drm_mock_sched_job_set_duration_us(job, 1000);
+		drm_mock_sched_job_submit(job);
+	}
+
+	do {
+		struct drm_gpu_scheduler *modify;
+
+		usleep_range(200, 500);
+		cur_ent++;
+		cur_ent %= ARRAY_SIZE(entity);
+		cur_sched++;
+		cur_sched %= ARRAY_SIZE(sched);
+		modify = &sched[cur_sched]->base;
+		drm_sched_entity_modify_sched(&entity[cur_ent]->base, &modify,
+					      1);
+	} while (!drm_mock_sched_job_is_finished(job));
+
+	for (i = 0; i < ARRAY_SIZE(entity); i++)
+		drm_mock_sched_entity_free(entity[i]);
+
+	for (i = 0; i < ARRAY_SIZE(sched); i++)
+		drm_mock_sched_fini(sched[i]);
+}
+
+static struct kunit_case drm_sched_modify_sched_tests[] = {
+	KUNIT_CASE(drm_sched_test_modify_sched),
+	{}
+};
+
+static struct kunit_suite drm_sched_modify_sched = {
+	.name = "drm_sched_basic_modify_sched_tests",
+	.test_cases = drm_sched_modify_sched_tests,
+};
+
 kunit_test_suites(&drm_sched_basic,
 		  &drm_sched_timeout,
-		  &drm_sched_priority);
+		  &drm_sched_priority,
+		  &drm_sched_modify_sched);