drm/sched: Add scheduler unit testing infrastructure and some basic tests

Implement a mock scheduler backend and add some basic test to exercise the
core scheduler code paths.

Mock backend (kind of like a very simple mock GPU) can either process jobs
by tests manually advancing the "timeline" job at a time, or alternatively
jobs can be configured with a time duration in which case they get
completed asynchronously from the unit test code.

Core scheduler classes are subclassed to support this mock implementation.

The tests added are just a few simple submission patterns.

Signed-off-by: Tvrtko Ursulin <tvrtko.ursulin@igalia.com>
Suggested-by: Philipp Stanner <phasta@kernel.org>
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/20250324092633.49746-3-tvrtko.ursulin@igalia.com

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

@@ -0,0 +1,198 @@
+// SPDX-License-Identifier: GPL-2.0
+/* Copyright (c) 2025 Valve Corporation */
+
+#include "sched_tests.h"
+
+/*
+ * DRM scheduler basic tests should check the basic functional correctness of
+ * the scheduler, including some very light smoke testing. More targeted tests,
+ * for example focusing on testing specific bugs and other more complicated test
+ * scenarios, should be implemented in separate source units.
+ */
+
+static int drm_sched_basic_init(struct kunit *test)
+{
+	test->priv = drm_mock_sched_new(test);
+
+	return 0;
+}
+
+static void drm_sched_basic_exit(struct kunit *test)
+{
+	struct drm_mock_scheduler *sched = test->priv;
+
+	drm_mock_sched_fini(sched);
+}
+
+static void drm_sched_basic_submit(struct kunit *test)
+{
+	struct drm_mock_scheduler *sched = test->priv;
+	struct drm_mock_sched_entity *entity;
+	struct drm_mock_sched_job *job;
+	unsigned int i;
+	bool done;
+
+	/*
+	 * Submit one job to the scheduler and verify that it gets scheduled
+	 * and completed only when the mock hw backend processes it.
+	 */
+
+	entity = drm_mock_sched_entity_new(test,
+					   DRM_SCHED_PRIORITY_NORMAL,
+					   sched);
+	job = drm_mock_sched_job_new(test, entity);
+
+	drm_mock_sched_job_submit(job);
+
+	done = drm_mock_sched_job_wait_scheduled(job, HZ);
+	KUNIT_ASSERT_TRUE(test, done);
+
+	done = drm_mock_sched_job_wait_finished(job, HZ / 2);
+	KUNIT_ASSERT_FALSE(test, done);
+
+	i = drm_mock_sched_advance(sched, 1);
+	KUNIT_ASSERT_EQ(test, i, 1);
+
+	done = drm_mock_sched_job_wait_finished(job, HZ);
+	KUNIT_ASSERT_TRUE(test, done);
+
+	drm_mock_sched_entity_free(entity);
+}
+
+struct drm_sched_basic_params {
+	const char *description;
+	unsigned int queue_depth;
+	unsigned int num_entities;
+	unsigned int job_us;
+	bool dep_chain;
+};
+
+static const struct drm_sched_basic_params drm_sched_basic_cases[] = {
+	{
+		.description = "A queue of jobs in a single entity",
+		.queue_depth = 100,
+		.job_us = 1000,
+		.num_entities = 1,
+	},
+	{
+		.description = "A chain of dependent jobs across multiple entities",
+		.queue_depth = 100,
+		.job_us = 1000,
+		.num_entities = 1,
+		.dep_chain = true,
+	},
+	{
+		.description = "Multiple independent job queues",
+		.queue_depth = 100,
+		.job_us = 1000,
+		.num_entities = 4,
+	},
+	{
+		.description = "Multiple inter-dependent job queues",
+		.queue_depth = 100,
+		.job_us = 1000,
+		.num_entities = 4,
+		.dep_chain = true,
+	},
+};
+
+static void
+drm_sched_basic_desc(const struct drm_sched_basic_params *params, char *desc)
+{
+	strscpy(desc, params->description, KUNIT_PARAM_DESC_SIZE);
+}
+
+KUNIT_ARRAY_PARAM(drm_sched_basic, drm_sched_basic_cases, drm_sched_basic_desc);
+
+static void drm_sched_basic_test(struct kunit *test)
+{
+	const struct drm_sched_basic_params *params = test->param_value;
+	struct drm_mock_scheduler *sched = test->priv;
+	struct drm_mock_sched_job *job, *prev = NULL;
+	struct drm_mock_sched_entity **entity;
+	unsigned int i, cur_ent = 0;
+	bool done;
+
+	entity = kunit_kcalloc(test, params->num_entities, sizeof(*entity),
+			       GFP_KERNEL);
+	KUNIT_ASSERT_NOT_NULL(test, entity);
+
+	for (i = 0; i < params->num_entities; i++)
+		entity[i] = drm_mock_sched_entity_new(test,
+						      DRM_SCHED_PRIORITY_NORMAL,
+						      sched);
+
+	for (i = 0; i < params->queue_depth; i++) {
+		job = drm_mock_sched_job_new(test, entity[cur_ent++]);
+		cur_ent %= params->num_entities;
+		drm_mock_sched_job_set_duration_us(job, params->job_us);
+		if (params->dep_chain && prev)
+			drm_sched_job_add_dependency(&job->base,
+						     dma_fence_get(&prev->base.s_fence->finished));
+		drm_mock_sched_job_submit(job);
+		prev = job;
+	}
+
+	done = drm_mock_sched_job_wait_finished(job, HZ);
+	KUNIT_ASSERT_TRUE(test, done);
+
+	for (i = 0; i < params->num_entities; i++)
+		drm_mock_sched_entity_free(entity[i]);
+}
+
+static void drm_sched_basic_entity_cleanup(struct kunit *test)
+{
+	struct drm_mock_sched_job *job, *mid, *prev = NULL;
+	struct drm_mock_scheduler *sched = test->priv;
+	struct drm_mock_sched_entity *entity[4];
+	const unsigned int qd = 100;
+	unsigned int i, cur_ent = 0;
+	bool done;
+
+	/*
+	 * Submit a queue of jobs across different entities with an explicit
+	 * chain of dependencies between them and trigger entity cleanup while
+	 * the queue is still being processed.
+	 */
+
+	for (i = 0; i < ARRAY_SIZE(entity); i++)
+		entity[i] = drm_mock_sched_entity_new(test,
+						      DRM_SCHED_PRIORITY_NORMAL,
+						      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);
+		if (prev)
+			drm_sched_job_add_dependency(&job->base,
+						     dma_fence_get(&prev->base.s_fence->finished));
+		drm_mock_sched_job_submit(job);
+		if (i == qd / 2)
+			mid = job;
+		prev = job;
+	}
+
+	done = drm_mock_sched_job_wait_finished(mid, HZ);
+	KUNIT_ASSERT_TRUE(test, done);
+
+	/* Exit with half of the queue still pending to be executed. */
+	for (i = 0; i < ARRAY_SIZE(entity); i++)
+		drm_mock_sched_entity_free(entity[i]);
+}
+
+static struct kunit_case drm_sched_basic_tests[] = {
+	KUNIT_CASE(drm_sched_basic_submit),
+	KUNIT_CASE_PARAM(drm_sched_basic_test, drm_sched_basic_gen_params),
+	KUNIT_CASE(drm_sched_basic_entity_cleanup),
+	{}
+};
+
+static struct kunit_suite drm_sched_basic = {
+	.name = "drm_sched_basic_tests",
+	.init = drm_sched_basic_init,
+	.exit = drm_sched_basic_exit,
+	.test_cases = drm_sched_basic_tests,
+};
+
+kunit_test_suite(drm_sched_basic);