xref: /dpdk/drivers/net/bnxt/tf_core/rand.c (revision e6e8f03e5459f25153f1e4cd3e9ac30d3e473a61) 
1 /* SPDX-License-Identifier: BSD-3-Clause
2  * Copyright(c) 2019-2023 Broadcom
3  * All rights reserved.
4  */
5 
6 /* Random Number Functions */
7 
8 #include <stdio.h>
9 #include <stdint.h>
10 #include "rand.h"
11 
12 #define TF_RAND_LFSR_INIT_VALUE 0xACE1u
13 
14 uint16_t lfsr = TF_RAND_LFSR_INIT_VALUE;
15 uint32_t bit;
16 
17 /**
18  * Generates a 16 bit pseudo random number
19  *
20  * Returns:
21  *   uint16_t number
22  */
rand16(void)23 uint16_t rand16(void)
24 {
25 	bit = ((lfsr >> 0) ^ (lfsr >> 2) ^ (lfsr >> 3) ^ (lfsr >> 5)) & 1;
26 	return lfsr = (lfsr >> 1) | (bit << 15);
27 }
28 
29 /**
30  * Generates a 32 bit pseudo random number
31  *
32  * Returns:
33  *   uint32_t number
34  */
rand32(void)35 uint32_t rand32(void)
36 {
37 	return (rand16() << 16) | rand16();
38 }
39 
40 /**
41  * Resets the seed used by the pseudo random number generator
42  */
rand_init(void)43 void rand_init(void)
44 {
45 	lfsr = TF_RAND_LFSR_INIT_VALUE;
46 	bit = 0;
47 }
48