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}