1 files changed, 110 insertions, 0 deletions
diff --git a/drivers/gpu/drm/i915/gt/selftest_ring.c b/drivers/gpu/drm/i915/gt/selftest_ring.c
new file mode 100644
index 000000000000..2a8c534dc125
--- /dev/null
+++ b/drivers/gpu/drm/i915/gt/selftest_ring.c
@@ -0,0 +1,110 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Copyright © 2020 Intel Corporation
+ */
+
+static struct intel_ring *mock_ring(unsigned long sz)
+{
+	struct intel_ring *ring;
+
+	ring = kzalloc(sizeof(*ring) + sz, GFP_KERNEL);
+	if (!ring)
+		return NULL;
+
+	kref_init(&ring->ref);
+	ring->size = sz;
+	ring->wrap = BITS_PER_TYPE(ring->size) - ilog2(sz);
+	ring->effective_size = sz;
+	ring->vaddr = (void *)(ring + 1);
+	atomic_set(&ring->pin_count, 1);
+
+	intel_ring_update_space(ring);
+
+	return ring;
+}
+
+static void mock_ring_free(struct intel_ring *ring)
+{
+	kfree(ring);
+}
+
+static int check_ring_direction(struct intel_ring *ring,
+				u32 next, u32 prev,
+				int expected)
+{
+	int result;
+
+	result = intel_ring_direction(ring, next, prev);
+	if (result < 0)
+		result = -1;
+	else if (result > 0)
+		result = 1;
+
+	if (result != expected) {
+		pr_err("intel_ring_direction(%u, %u):%d != %d\n",
+		       next, prev, result, expected);
+		return -EINVAL;
+	}
+
+	return 0;
+}
+
+static int check_ring_step(struct intel_ring *ring, u32 x, u32 step)
+{
+	u32 prev = x, next = intel_ring_wrap(ring, x + step);
+	int err = 0;
+
+	err |= check_ring_direction(ring, next, next,  0);
+	err |= check_ring_direction(ring, prev, prev,  0);
+	err |= check_ring_direction(ring, next, prev,  1);
+	err |= check_ring_direction(ring, prev, next, -1);
+
+	return err;
+}
+
+static int check_ring_offset(struct intel_ring *ring, u32 x, u32 step)
+{
+	int err = 0;
+
+	err |= check_ring_step(ring, x, step);
+	err |= check_ring_step(ring, intel_ring_wrap(ring, x + 1), step);
+	err |= check_ring_step(ring, intel_ring_wrap(ring, x - 1), step);
+
+	return err;
+}
+
+static int igt_ring_direction(void *dummy)
+{
+	struct intel_ring *ring;
+	unsigned int half = 2048;
+	int step, err = 0;
+
+	ring = mock_ring(2 * half);
+	if (!ring)
+		return -ENOMEM;
+
+	GEM_BUG_ON(ring->size != 2 * half);
+
+	/* Precision of wrap detection is limited to ring->size / 2 */
+	for (step = 1; step < half; step <<= 1) {
+		err |= check_ring_offset(ring, 0, step);
+		err |= check_ring_offset(ring, half, step);
+	}
+	err |= check_ring_step(ring, 0, half - 64);
+
+	/* And check unwrapped handling for good measure */
+	err |= check_ring_offset(ring, 0, 2 * half + 64);
+	err |= check_ring_offset(ring, 3 * half, 1);
+
+	mock_ring_free(ring);
+	return err;
+}
+
+int intel_ring_mock_selftests(void)
+{
+	static const struct i915_subtest tests[] = {
+		SUBTEST(igt_ring_direction),
+	};
+
+	return i915_subtests(tests, NULL);
+}