OpenCores
URL https://opencores.org/ocsvn/neorv32/neorv32/trunk

Subversion Repositories neorv32

[/] [neorv32/] [trunk/] [sw/] [lib/] [source/] [neorv32_trng.c] - Blame information for rev 2

Go to most recent revision | Details | Compare with Previous | View Log

Line No. Rev Author Line
1 2 zero_gravi
// #################################################################################################
2
// # << NEORV32: neorv32_trng.c - True Random Number Generator (TRNG) HW Driver >>                 #
3
// # ********************************************************************************************* #
4
// # BSD 3-Clause License                                                                          #
5
// #                                                                                               #
6
// # Copyright (c) 2020, Stephan Nolting. All rights reserved.                                     #
7
// #                                                                                               #
8
// # Redistribution and use in source and binary forms, with or without modification, are          #
9
// # permitted provided that the following conditions are met:                                     #
10
// #                                                                                               #
11
// # 1. Redistributions of source code must retain the above copyright notice, this list of        #
12
// #    conditions and the following disclaimer.                                                   #
13
// #                                                                                               #
14
// # 2. Redistributions in binary form must reproduce the above copyright notice, this list of     #
15
// #    conditions and the following disclaimer in the documentation and/or other materials        #
16
// #    provided with the distribution.                                                            #
17
// #                                                                                               #
18
// # 3. Neither the name of the copyright holder nor the names of its contributors may be used to  #
19
// #    endorse or promote products derived from this software without specific prior written      #
20
// #    permission.                                                                                #
21
// #                                                                                               #
22
// # THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND ANY EXPRESS   #
23
// # OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF               #
24
// # MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE    #
25
// # COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,     #
26
// # EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE #
27
// # GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED    #
28
// # AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING     #
29
// # NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED  #
30
// # OF THE POSSIBILITY OF SUCH DAMAGE.                                                            #
31
// # ********************************************************************************************* #
32
// # The NEORV32 Processor - https://github.com/stnolting/neorv32              (c) Stephan Nolting #
33
// #################################################################################################
34
 
35
 
36
/**********************************************************************//**
37
 * @file neorv32_trng.c
38
 * @author Stephan Nolting
39
 * @brief True Random Number Generator (TRNG) HW driver source file.
40
 *
41
 * @note These functions should only be used if the TRNG unit was synthesized (IO_TRNG_USE = true).
42
 **************************************************************************/
43
 
44
#include "neorv32.h"
45
#include "neorv32_trng.h"
46
 
47
 
48
/**********************************************************************//**
49
 * Check if TRNG unit was synthesized.
50
 *
51
 * @return 0 if TRNG was not synthesized, 1 if TRNG is available.
52
 **************************************************************************/
53
int neorv32_trng_available(void) {
54
 
55
  if (neorv32_cpu_csr_read(CSR_MFEATURES) & (1 << CPU_MFEATURES_IO_TRNG)) {
56
    return 1;
57
  }
58
  else {
59
    return 0;
60
  }
61
}
62
 
63
 
64
/**********************************************************************//**
65
 * Enable and configure true random number generator. The TRNG control register bits are listed in #NEORV32_TRNG_CT_enum.
66
 *
67
 * @param[in] tap_mask 16-bit tap mask for GARO array.
68
 * @return Returns 0 if the provided tap_mask works correctly (GARO-array is oscillating), returns 1 otherwise.
69
 **************************************************************************/
70
int neorv32_trng_setup(uint16_t tap_mask) {
71
 
72
  TRNG_CT = 0; // reset
73
 
74
  // configure
75
  uint32_t tap_config = (uint32_t)(tap_mask);
76
  tap_config = tap_config << TRNG_CT_TAP_LSB;
77
  TRNG_CT = (1 << TRNG_CT_EN) | tap_config;
78
 
79
  neorv32_cpu_delay_ms(1);
80
 
81
  // check if TRNG is oscillating
82
  uint16_t trng_data;
83
  if (neorv32_trng_get(&trng_data) == 0) {
84
    return 0;
85
  }
86
  else {
87
    return 1;
88
  }
89
}
90
 
91
 
92
/**********************************************************************//**
93
 * Disable true random number generator.
94
 **************************************************************************/
95
void neorv32_trng_disable(void) {
96
 
97
  TRNG_CT &= ~((uint32_t)(1 << TRNG_CT_EN));
98
}
99
 
100
 
101
/**********************************************************************//**
102
 * Get random data from TRNG.
103
 *
104
 * @param[in,out] data uint16_t pointer for storing random data word
105
 * @return Valid data when 0, invalid data when 1
106
 **************************************************************************/
107
int neorv32_trng_get(uint16_t *data) {
108
 
109
  int i;
110
  const int max_try = 16;
111
  uint32_t trng_data;
112
  uint32_t rnd_data;
113
 
114
  for(i=0; i<max_try; i++) {
115
 
116
    trng_data = TRNG_DATA;
117
    rnd_data  = trng_data >> TRNG_DATA_LSB;
118
    *data = (uint16_t)rnd_data;
119
 
120
    if (trng_data & (1<<TRNG_DATA_VALID)) { // output data valid?
121
      return 0; // valid
122
    }
123
 
124
  }
125
 
126
  return 1; // invalid
127
}
128
 
129
 
130
/**********************************************************************//**
131
 * Try to find a valid TRNG tap configuration mask.
132
 *
133
 * @return Tap mask for configuring the TRNG. If return is zero, no valid tap mask was found.
134
 **************************************************************************/
135
uint16_t neorv32_trng_find_tap_mask(void) {
136
 
137
  int j;
138
  uint16_t tap_config16 = 0xfff0; // keep the lowest inverters without feedback
139
  uint16_t trng_data;
140
  int success = 0;
141
 
142
  // tap mask is zero, try to find a nice one
143
  while (1) {
144
 
145
    // good mask found?
146
    if ((success) || (tap_config16 <= 0x0008)) {
147
      break;
148
    }
149
 
150
    // generate a new tap
151
    tap_config16 -= 0x0008;
152
 
153
    // install it
154
    if (neorv32_trng_setup(tap_config16)) {
155
      continue;
156
    }
157
 
158
    // does it work?
159
    success = 1;
160
    for (j=0; j < 100; j++) {
161
      neorv32_cpu_delay_ms(1);
162
      if (neorv32_trng_get(&trng_data)) { // stop testing on fail
163
        success = 0;
164
        break;
165
      }
166
    }
167
  }
168
 
169
  return (uint16_t)tap_config16;
170
}
171
 

powered by: WebSVN 2.1.0

© copyright 1999-2024 OpenCores.org, equivalent to Oliscience, all rights reserved. OpenCores®, registered trademark.