sam4l_crypto_trng.c

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/**
 * @file sam4l_crypto_trng.c
 * @brief SAM4L true random number generator
 *
 * @section License
 *
 * SPDX-License-Identifier: GPL-2.0-or-later
 *
 * Copyright (C) 2010-2024 Oryx Embedded SARL. All rights reserved.
 *
 * This file is part of CycloneCRYPTO Open.
 *
 * This program is free software; you can redistribute it and/or
 * modify it under the terms of the GNU General Public License
 * as published by the Free Software Foundation; either version 2
 * of the License, or (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write to the Free Software Foundation,
 * Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301, USA.
 *
 * @author Oryx Embedded SARL (www.oryx-embedded.com)
 * @version 2.4.0
 **/
 
//Switch to the appropriate trace level
#define TRACE_LEVEL CRYPTO_TRACE_LEVEL
 
//Dependencies
#include "sam4l.h"
#include "core/crypto.h"
#include "hardware/sam4l/sam4l_crypto.h"
#include "hardware/sam4l/sam4l_crypto_trng.h"
#include "debug.h"
 
//Check crypto library configuration
#if (SAM4L_CRYPTO_TRNG_SUPPORT == ENABLED)
 
 
/**
 * @brief TRNG module initialization
 * @return Error code
 **/
 
error_t trngInit(void)
{
   //Disable write protect
   PM->PM_UNLOCK = PM_UNLOCK_KEY(0xAAU) |
      PM_UNLOCK_ADDR((uint32_t) &PM->PM_PBAMASK - (uint32_t) PM);
 
   //Enable TRNG peripheral clock
   PM->PM_PBAMASK |= PM_PBAMASK_TRNG;
 
   //Enable TRNG
   TRNG->TRNG_CR = TRNG_CR_KEY(0x524E47) | TRNG_CR_ENABLE;
 
   //Successful initialization
   return NO_ERROR;
}
 
 
/**
 * @brief Get random data from the TRNG module
 * @param[out] data Buffer where to store random data
 * @param[in] length Number of random bytes to generate
 **/
 
error_t trngGetRandomData(uint8_t *data, size_t length)
{
   size_t i;
   uint32_t value;
 
   //Initialize variable
   value = 0;
 
   //Acquire exclusive access to the TRNG module
   osAcquireMutex(&sam4lCryptoMutex);
 
   //Generate random data
   for(i = 0; i < length; i++)
   {
      //Generate a new 32-bit random value when necessary
      if((i % 4) == 0)
      {
         //Wait for the TRNG to contain a valid data
         while((TRNG->TRNG_ISR & TRNG_ISR_DATRDY) == 0)
         {
         }
 
         //Get the 32-bit random value
         value = TRNG->TRNG_ODATA;
      }
 
      //Copy random byte
      data[i] = value & 0xFF;
      //Shift the 32-bit random value
      value >>= 8;
   }
 
   //Release exclusive access to the TRNG module
   osReleaseMutex(&sam4lCryptoMutex);
 
   //Successful processing
   return NO_ERROR;
}
 
#endif