1 /* $NetBSD: i915_random.c,v 1.2 2021/12/18 23:45:31 riastradh Exp $ */
2
3 /*
4 * Copyright © 2016 Intel Corporation
5 *
6 * Permission is hereby granted, free of charge, to any person obtaining a
7 * copy of this software and associated documentation files (the "Software"),
8 * to deal in the Software without restriction, including without limitation
9 * the rights to use, copy, modify, merge, publish, distribute, sublicense,
10 * and/or sell copies of the Software, and to permit persons to whom the
11 * Software is furnished to do so, subject to the following conditions:
12 *
13 * The above copyright notice and this permission notice (including the next
14 * paragraph) shall be included in all copies or substantial portions of the
15 * Software.
16 *
17 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
18 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
19 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
20 * THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
21 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
22 * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS
23 * IN THE SOFTWARE.
24 *
25 */
26
27 #include <sys/cdefs.h>
28 __KERNEL_RCSID(0, "$NetBSD: i915_random.c,v 1.2 2021/12/18 23:45:31 riastradh Exp $");
29
30 #include <linux/bitops.h>
31 #include <linux/kernel.h>
32 #include <linux/random.h>
33 #include <linux/slab.h>
34 #include <linux/types.h>
35
36 #include "i915_random.h"
37 #include "i915_utils.h"
38
i915_prandom_u64_state(struct rnd_state * rnd)39 u64 i915_prandom_u64_state(struct rnd_state *rnd)
40 {
41 u64 x;
42
43 x = prandom_u32_state(rnd);
44 x <<= 32;
45 x |= prandom_u32_state(rnd);
46
47 return x;
48 }
49
i915_prandom_shuffle(void * arr,size_t elsz,size_t count,struct rnd_state * state)50 void i915_prandom_shuffle(void *arr, size_t elsz, size_t count,
51 struct rnd_state *state)
52 {
53 char stack[128];
54
55 if (WARN_ON(elsz > sizeof(stack) || count > U32_MAX))
56 return;
57
58 if (!elsz || !count)
59 return;
60
61 /* Fisher-Yates shuffle courtesy of Knuth */
62 while (--count) {
63 size_t swp;
64
65 swp = i915_prandom_u32_max_state(count + 1, state);
66 if (swp == count)
67 continue;
68
69 memcpy(stack, arr + count * elsz, elsz);
70 memcpy(arr + count * elsz, arr + swp * elsz, elsz);
71 memcpy(arr + swp * elsz, stack, elsz);
72 }
73 }
74
i915_random_reorder(unsigned int * order,unsigned int count,struct rnd_state * state)75 void i915_random_reorder(unsigned int *order, unsigned int count,
76 struct rnd_state *state)
77 {
78 i915_prandom_shuffle(order, sizeof(*order), count, state);
79 }
80
i915_random_order(unsigned int count,struct rnd_state * state)81 unsigned int *i915_random_order(unsigned int count, struct rnd_state *state)
82 {
83 unsigned int *order, i;
84
85 order = kmalloc_array(count, sizeof(*order),
86 GFP_KERNEL | __GFP_RETRY_MAYFAIL | __GFP_NOWARN);
87 if (!order)
88 return order;
89
90 for (i = 0; i < count; i++)
91 order[i] = i;
92
93 i915_random_reorder(order, count, state);
94 return order;
95 }
96
igt_random_offset(struct rnd_state * state,u64 start,u64 end,u64 len,u64 align)97 u64 igt_random_offset(struct rnd_state *state,
98 u64 start, u64 end,
99 u64 len, u64 align)
100 {
101 u64 range, addr;
102
103 BUG_ON(range_overflows(start, len, end));
104 BUG_ON(round_up(start, align) > round_down(end - len, align));
105
106 range = round_down(end - len, align) - round_up(start, align);
107 if (range) {
108 addr = i915_prandom_u64_state(state);
109 div64_u64_rem(addr, range, &addr);
110 start += addr;
111 }
112
113 return round_up(start, align);
114 }
115