1// SPDX-License-Identifier: GPL-2.0
  2/*
  3 * Copyright © 2020 Intel Corporation
  4 */
  5
  6static struct intel_ring *mock_ring(unsigned long sz)
  7{
  8	struct intel_ring *ring;
  9
 10	ring = kzalloc(sizeof(*ring) + sz, GFP_KERNEL);
 11	if (!ring)
 12		return NULL;
 13
 14	kref_init(&ring->ref);
 15	ring->size = sz;
 16	ring->wrap = BITS_PER_TYPE(ring->size) - ilog2(sz);
 17	ring->effective_size = sz;
 18	ring->vaddr = (void *)(ring + 1);
 19	atomic_set(&ring->pin_count, 1);
 20
 21	intel_ring_update_space(ring);
 22
 23	return ring;
 24}
 25
 26static void mock_ring_free(struct intel_ring *ring)
 27{
 28	kfree(ring);
 29}
 30
 31static int check_ring_direction(struct intel_ring *ring,
 32				u32 next, u32 prev,
 33				int expected)
 34{
 35	int result;
 36
 37	result = intel_ring_direction(ring, next, prev);
 38	if (result < 0)
 39		result = -1;
 40	else if (result > 0)
 41		result = 1;
 42
 43	if (result != expected) {
 44		pr_err("intel_ring_direction(%u, %u):%d != %d\n",
 45		       next, prev, result, expected);
 46		return -EINVAL;
 47	}
 48
 49	return 0;
 50}
 51
 52static int check_ring_step(struct intel_ring *ring, u32 x, u32 step)
 53{
 54	u32 prev = x, next = intel_ring_wrap(ring, x + step);
 55	int err = 0;
 56
 57	err |= check_ring_direction(ring, next, next,  0);
 58	err |= check_ring_direction(ring, prev, prev,  0);
 59	err |= check_ring_direction(ring, next, prev,  1);
 60	err |= check_ring_direction(ring, prev, next, -1);
 61
 62	return err;
 63}
 64
 65static int check_ring_offset(struct intel_ring *ring, u32 x, u32 step)
 66{
 67	int err = 0;
 68
 69	err |= check_ring_step(ring, x, step);
 70	err |= check_ring_step(ring, intel_ring_wrap(ring, x + 1), step);
 71	err |= check_ring_step(ring, intel_ring_wrap(ring, x - 1), step);
 72
 73	return err;
 74}
 75
 76static int igt_ring_direction(void *dummy)
 77{
 78	struct intel_ring *ring;
 79	unsigned int half = 2048;
 80	int step, err = 0;
 81
 82	ring = mock_ring(2 * half);
 83	if (!ring)
 84		return -ENOMEM;
 85
 86	GEM_BUG_ON(ring->size != 2 * half);
 87
 88	/* Precision of wrap detection is limited to ring->size / 2 */
 89	for (step = 1; step < half; step <<= 1) {
 90		err |= check_ring_offset(ring, 0, step);
 91		err |= check_ring_offset(ring, half, step);
 92	}
 93	err |= check_ring_step(ring, 0, half - 64);
 94
 95	/* And check unwrapped handling for good measure */
 96	err |= check_ring_offset(ring, 0, 2 * half + 64);
 97	err |= check_ring_offset(ring, 3 * half, 1);
 98
 99	mock_ring_free(ring);
100	return err;
101}
102
103int intel_ring_mock_selftests(void)
104{
105	static const struct i915_subtest tests[] = {
106		SUBTEST(igt_ring_direction),
107	};
108
109	return i915_subtests(tests, NULL);
110}