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(rnd);
39	x <<= 32;
40	x |= prandom_u32_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(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(order, 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(state);
104		div64_u64_rem(addr, range, &addr);
105		start += addr;
106	}
107
108	return round_up(start, align);
109}
110