drivers/gpu/drm/i915/selftests/i915_random.c

   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 }