Subversion Repositories neorv32

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// # << NEORV32: neorv32_trng.c - True Random Number Generator (TRNG) HW Driver >>                 #

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// # BSD 3-Clause License                                                                          #

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// # Copyright (c) 2021, Stephan Nolting. All rights reserved.                                     #

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// # The NEORV32 Processor - https://github.com/stnolting/neorv32              (c) Stephan Nolting #

// #################################################################################################

/**********************************************************************//**

 * @file neorv32_trng.c

 * @author Stephan Nolting

 * @brief True Random Number Generator (TRNG) HW driver source file.

 *

 * @note These functions should only be used if the TRNG unit was synthesized (IO_TRNG_EN = true).

 **************************************************************************/

#include "neorv32.h"

#include "neorv32_trng.h"

/**********************************************************************//**

 * Check if TRNG unit was synthesized.

 *

 * @return 0 if TRNG was not synthesized, 1 if TRNG is available.

 **************************************************************************/

int neorv32_trng_available(void) {

  if (NEORV32_SYSINFO.SOC & (1 << SYSINFO_SOC_IO_TRNG)) {

    return 1;

  }

  else {

    return 0;

  }

}

/**********************************************************************//**

 * Enable true random number generator. The TRNG control register bits are listed in #NEORV32_TRNG_CTRL_enum.

 **************************************************************************/

void neorv32_trng_enable(void) {

  int i;

  NEORV32_TRNG.CTRL = 0; // reset

  for (i=0; i<256; i++) {

    asm volatile ("nop");

  }

  NEORV32_TRNG.CTRL = 1 << TRNG_CTRL_EN; // activate

  for (i=0; i<256; i++) {

    asm volatile ("nop");

  }

}

/**********************************************************************//**

 * Disable true random number generator.

 **************************************************************************/

void neorv32_trng_disable(void) {

  NEORV32_TRNG.CTRL = 0;

}

/**********************************************************************//**

 * Get random data byte from TRNG.

 *

 * @param[in,out] data uint8_t pointer for storing random data byte.

 * @return Data is valid when 0 and invalid otherwise.

 **************************************************************************/

int neorv32_trng_get(uint8_t *data) {

  const int retries = 3;

  int i;

  uint32_t ct_reg;

  for (i=0; i<retries; i++) {

    ct_reg = NEORV32_TRNG.CTRL;

    if ((ct_reg & (1<<TRNG_CTRL_VALID)) == 0) { // output data valid?

      continue;

    }

    *data = (uint8_t)(ct_reg >> TRNG_CTRL_DATA_LSB);

    return 0; // valid data

  }

  return -1; // no valid data available

}