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 
34 u64 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 
45 void 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 
70 void 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 
76 unsigned 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 
92 u64 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