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
33u64 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
44void 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
69void 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
75unsigned 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}