1/*
2 * Copyright © 2016 Intel Corporation
3 *
4 * Permission is hereby granted, free of charge, to any person obtaining a
5 * copy of this software and associated documentation files (the "Software"),
6 * to deal in the Software without restriction, including without limitation
7 * the rights to use, copy, modify, merge, publish, distribute, sublicense,
8 * and/or sell copies of the Software, and to permit persons to whom the
9 * Software is furnished to do so, subject to the following conditions:
10 *
11 * The above copyright notice and this permission notice (including the next
12 * paragraph) shall be included in all copies or substantial portions of the
13 * Software.
14 *
15 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
16 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
17 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
18 * THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
19 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
20 * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS
21 * IN THE SOFTWARE.
22 *
23 */
24
25#include <linux/bitops.h>
26#include <linux/kernel.h>
27#include <linux/random.h>
28#include <linux/slab.h>
29#include <linux/types.h>
30
31#include "i915_random.h"
32#include "i915_utils.h"
33
34u64 i915_prandom_u64_state(struct rnd_state *rnd)
35{
36 u64 x;
37
38 x = prandom_u32_state(state: rnd);
39 x <<= 32;
40 x |= prandom_u32_state(state: rnd);
41
42 return x;
43}
44
45void i915_prandom_shuffle(void *arr, size_t elsz, size_t count,
46 struct rnd_state *state)
47{
48 char stack[128];
49
50 if (WARN_ON(elsz > sizeof(stack) || count > U32_MAX))
51 return;
52
53 if (!elsz || !count)
54 return;
55
56 /* Fisher-Yates shuffle courtesy of Knuth */
57 while (--count) {
58 size_t swp;
59
60 swp = i915_prandom_u32_max_state(ep_ro: count + 1, state);
61 if (swp == count)
62 continue;
63
64 memcpy(stack, arr + count * elsz, elsz);
65 memcpy(arr + count * elsz, arr + swp * elsz, elsz);
66 memcpy(arr + swp * elsz, stack, elsz);
67 }
68}
69
70void i915_random_reorder(unsigned int *order, unsigned int count,
71 struct rnd_state *state)
72{
73 i915_prandom_shuffle(arr: order, elsz: sizeof(*order), count, state);
74}
75
76unsigned int *i915_random_order(unsigned int count, struct rnd_state *state)
77{
78 unsigned int *order, i;
79
80 order = kmalloc_array(count, sizeof(*order),
81 GFP_KERNEL | __GFP_RETRY_MAYFAIL | __GFP_NOWARN);
82 if (!order)
83 return order;
84
85 for (i = 0; i < count; i++)
86 order[i] = i;
87
88 i915_random_reorder(order, count, state);
89 return order;
90}
91
92u64 igt_random_offset(struct rnd_state *state,
93 u64 start, u64 end,
94 u64 len, u64 align)
95{
96 u64 range, addr;
97
98 BUG_ON(range_overflows(start, len, end));
99 BUG_ON(round_up(start, align) > round_down(end - len, align));
100
101 range = round_down(end - len, align) - round_up(start, align);
102 if (range) {
103 addr = i915_prandom_u64_state(rnd: state);
104 div64_u64_rem(dividend: addr, divisor: range, remainder: &addr);
105 start += addr;
106 }
107
108 return round_up(start, align);
109}
110

source code of linux/drivers/gpu/drm/i915/selftests/i915_random.c