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
33 u64 i915_prandom_u64_state(struct rnd_state *rnd)
34 {
35 u64 x;
36
37 x = prandom_u32_state(rnd);
38 x <<= 32;
39 x |= prandom_u32_state(rnd);
40
41 return x;
42 }
43
44 void i915_prandom_shuffle(void *arr, size_t elsz, size_t count,
45 struct rnd_state *state)
46 {
47 char stack[128];
48
49 if (WARN_ON(elsz > sizeof(stack) || count > U32_MAX))
50 return;
51
52 if (!elsz || !count)
53 return;
54
55 /* Fisher-Yates shuffle courtesy of Knuth */
56 while (--count) {
57 size_t swp;
58
59 swp = i915_prandom_u32_max_state(count + 1, state);
60 if (swp == count)
61 continue;
62
63 memcpy(stack, arr + count * elsz, elsz);
64 memcpy(arr + count * elsz, arr + swp * elsz, elsz);
65 memcpy(arr + swp * elsz, stack, elsz);
66 }
67 }
68
69 void i915_random_reorder(unsigned int *order, unsigned int count,
70 struct rnd_state *state)
71 {
72 i915_prandom_shuffle(order, sizeof(*order), count, state);
73 }
74
75 unsigned int *i915_random_order(unsigned int count, struct rnd_state *state)
76 {
77 unsigned int *order, i;
78
79 order = kmalloc_array(count, sizeof(*order),
80 GFP_KERNEL | __GFP_RETRY_MAYFAIL | __GFP_NOWARN);
81 if (!order)
82 return order;
83
84 for (i = 0; i < count; i++)
85 order[i] = i;
86
87 i915_random_reorder(order, count, state);
88 return order;
89 }