xref: /netbsd-src/sys/external/bsd/drm2/dist/drm/i915/selftests/i915_random.c (revision 41ec02673d281bbb3d38e6c78504ce6e30c228c1)
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