text: /*
   *  Hardware entropy collector for the K66F, using Freescale's RNGA
   *
   *  Copyright (C) 2006-2015, ARM Limited, All Rights Reserved
   *  SPDX-License-Identifier: Apache-2.0
   *
   *  Licensed under the Apache License, Version 2.0 (the "License"); you may
   *  not use this file except in compliance with the License.
   *  You may obtain a copy of the License at
   *
   *  http://www.apache.org/licenses/LICENSE-2.0
   *
   *  Unless required by applicable law or agreed to in writing, software
   *  distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
   *  WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
   *  See the License for the specific language governing permissions and
   *  limitations under the License.
   *
   */
  
  /*
   * Reference: "K66 Sub-Family Reference Manual, Rev. 2", chapter 38
   */
  
  #if defined(DEVICE_TRNG)
  
  #include <stdlib.h>
  #include "cmsis.h"
  #include "fsl_common.h"
  #include "fsl_clock.h"
  #include "trng_api.h"
  
  void trng_init(trng_t *obj)
  {
      (void)obj;
      CLOCK_EnableClock(kCLOCK_Rnga0);
      CLOCK_DisableClock(kCLOCK_Rnga0);
      CLOCK_EnableClock(kCLOCK_Rnga0);
  }
  
  void trng_free(trng_t *obj)
  {
      (void)obj;
      CLOCK_DisableClock(kCLOCK_Rnga0);
  }
  
  /*
   * Get one byte of entropy from the RNG, assuming it is up and running.
   * As recommended (34.1.1), get only one bit of each output.
   */
  static void trng_get_byte(unsigned char *byte)
  {
      *byte = 0;
      size_t bit;
  
      /* 34.5 Steps 3-4-5: poll SR and read from OR when ready */
      for( bit = 0; bit < 8; bit++ )
      {
          while((RNG->SR & RNG_SR_OREG_LVL_MASK) == 0 );
          *byte |= (RNG->OR & 1) << bit;
      }
  }
  
  int trng_get_bytes(trng_t *obj, uint8_t *output, size_t length, size_t *output_length)
  {
      (void)obj;
      size_t i;
  
      /* Set "Interrupt Mask", "High Assurance" and "Go",
       * unset "Clear interrupt" and "Sleep" */
      RNG->CR = RNG_CR_INTM_MASK | RNG_CR_HA_MASK | RNG_CR_GO_MASK;
  
      for (i = 0; i < length; i++) {
          trng_get_byte(output + i);
      }
  
      /* Just be extra sure that we didn't do it wrong */
      if ((RNG->SR & RNG_SR_SECV_MASK) != 0) {
          return -1;
      }
  
      *output_length = length;
  
      return 0;
  }
  
  #endif
  