drm/tests: Add a unit test for range bias allocation

Allocate cleared blocks in the bias range when the DRM
buddy's clear avail is zero. This will validate the bias
range allocation in scenarios like system boot when no
cleared blocks are available and exercise the fallback
path too. The resulting blocks should always be dirty.

v1:(Matthew)
  - move the size to the variable declaration section.
  - move the mm.clear_avail init to allocator init.

Signed-off-by: Arunpravin Paneer Selvam <Arunpravin.PaneerSelvam@amd.com>
Reviewed-by: Matthew Auld <matthew.auld@intel.com>
Signed-off-by: Dave Airlie <airlied@redhat.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20240514145636.16253-2-Arunpravin.PaneerSelvam@amd.com

Author: arunpravin24

drivers/gpu/drm/tests/drm_buddy_test.c

@@ -23,9 +23,11 @@ static inline u64 get_size(int order, u64 chunk_size)
 
 static void drm_test_buddy_alloc_range_bias(struct kunit *test)
 {
-	u32 mm_size, ps, bias_size, bias_start, bias_end, bias_rem;
+	u32 mm_size, size, ps, bias_size, bias_start, bias_end, bias_rem;
 	DRM_RND_STATE(prng, random_seed);
 	unsigned int i, count, *order;
+	struct drm_buddy_block *block;
+	unsigned long flags;
 	struct drm_buddy mm;
 	LIST_HEAD(allocated);
 
@@ -222,6 +224,38 @@ static void drm_test_buddy_alloc_range_bias(struct kunit *test)
 
 	drm_buddy_free_list(&mm, &allocated, 0);
 	drm_buddy_fini(&mm);
+
+	/*
+	 * Allocate cleared blocks in the bias range when the DRM buddy's clear avail is
+	 * zero. This will validate the bias range allocation in scenarios like system boot
+	 * when no cleared blocks are available and exercise the fallback path too. The resulting
+	 * blocks should always be dirty.
+	 */
+
+	KUNIT_ASSERT_FALSE_MSG(test, drm_buddy_init(&mm, mm_size, ps),
+			       "buddy_init failed\n");
+
+	bias_start = round_up(prandom_u32_state(&prng) % (mm_size - ps), ps);
+	bias_end = round_up(bias_start + prandom_u32_state(&prng) % (mm_size - bias_start), ps);
+	bias_end = max(bias_end, bias_start + ps);
+	bias_rem = bias_end - bias_start;
+
+	flags = DRM_BUDDY_CLEAR_ALLOCATION | DRM_BUDDY_RANGE_ALLOCATION;
+	size = max(round_up(prandom_u32_state(&prng) % bias_rem, ps), ps);
+
+	KUNIT_ASSERT_FALSE_MSG(test,
+			       drm_buddy_alloc_blocks(&mm, bias_start,
+						      bias_end, size, ps,
+						      &allocated,
+						      flags),
+			       "buddy_alloc failed with bias(%x-%x), size=%u, ps=%u\n",
+			       bias_start, bias_end, size, ps);
+
+	list_for_each_entry(block, &allocated, link)
+		KUNIT_EXPECT_EQ(test, drm_buddy_block_is_clear(block), false);
+
+	drm_buddy_free_list(&mm, &allocated, 0);
+	drm_buddy_fini(&mm);
 }
 
 static void drm_test_buddy_alloc_clear(struct kunit *test)