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[/] [neorv32/] [trunk/] [sw/] [lib/] [source/] [neorv32_trng.c] - Blame information for rev 47

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// #################################################################################################
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// # << NEORV32: neorv32_trng.c - True Random Number Generator (TRNG) HW Driver >>                 #
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// # ********************************************************************************************* #
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// # BSD 3-Clause License                                                                          #
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// #                                                                                               #
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// # Copyright (c) 2021, Stephan Nolting. All rights reserved.                                     #
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// #                                                                                               #
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// # Redistribution and use in source and binary forms, with or without modification, are          #
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// # permitted provided that the following conditions are met:                                     #
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// #                                                                                               #
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// # 1. Redistributions of source code must retain the above copyright notice, this list of        #
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// #    conditions and the following disclaimer.                                                   #
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// #                                                                                               #
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// # 2. Redistributions in binary form must reproduce the above copyright notice, this list of     #
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// #    conditions and the following disclaimer in the documentation and/or other materials        #
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// #    provided with the distribution.                                                            #
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// #                                                                                               #
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// # 3. Neither the name of the copyright holder nor the names of its contributors may be used to  #
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// #    endorse or promote products derived from this software without specific prior written      #
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// #    permission.                                                                                #
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// #                                                                                               #
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// # THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND ANY EXPRESS   #
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// # OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF               #
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// # MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE    #
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// # COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,     #
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// # EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE #
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// # GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED    #
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// # AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING     #
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// # NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED  #
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// # OF THE POSSIBILITY OF SUCH DAMAGE.                                                            #
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// # ********************************************************************************************* #
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// # The NEORV32 Processor - https://github.com/stnolting/neorv32              (c) Stephan Nolting #
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// #################################################################################################
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/**********************************************************************//**
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 * @file neorv32_trng.c
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 * @author Stephan Nolting
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 * @brief True Random Number Generator (TRNG) HW driver source file.
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 *
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 * @note These functions should only be used if the TRNG unit was synthesized (IO_TRNG_EN = true).
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 **************************************************************************/
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#include "neorv32.h"
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#include "neorv32_trng.h"
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/**********************************************************************//**
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 * Check if TRNG unit was synthesized.
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 *
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 * @return 0 if TRNG was not synthesized, 1 if TRNG is available.
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 **************************************************************************/
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int neorv32_trng_available(void) {
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  if (SYSINFO_FEATURES & (1 << SYSINFO_FEATURES_IO_TRNG)) {
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    return 1;
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  }
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  else {
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    return 0;
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  }
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}
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/**********************************************************************//**
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 * Enable true random number generator. The TRNG control register bits are listed in #NEORV32_TRNG_CT_enum.
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 **************************************************************************/
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void neorv32_trng_enable(void) {
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  int i;
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  TRNG_CT = 0; // reset
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  for (i=0; i<256; i++) {
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    asm volatile ("nop");
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  }
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  TRNG_CT = 1 << TRNG_CT_EN; // activate
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  for (i=0; i<256; i++) {
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    asm volatile ("nop");
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  }
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}
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/**********************************************************************//**
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 * Disable true random number generator.
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 **************************************************************************/
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void neorv32_trng_disable(void) {
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  TRNG_CT = 0;
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}
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/**********************************************************************//**
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 * Get random data byte from TRNG.
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 *
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 * @param[in,out] data uint8_t pointer for storing random data byte.
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 * @return Data is valid when 0 and invalid otherwise.
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 **************************************************************************/
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int neorv32_trng_get(uint8_t *data) {
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  const int retries = 3;
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  int i;
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  uint32_t ct_reg;
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  for (i=0; i<retries; i++) {
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    ct_reg = TRNG_CT;
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    if ((ct_reg & (1<<TRNG_CT_VALID)) == 0) { // output data valid?
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      continue;
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    }
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    *data = (uint8_t)(ct_reg >> TRNG_CT_DATA_LSB);
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    return 0; // valid data
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  }
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  return -1; // no valid data available
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}

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