text: /*
   * Copyright (C) 2012 The Android Open Source Project
   *
   * 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.
   */
  #define ADK_INTERNAL
  #include "fwk.h"
  #include "Audio.h"
  #include "coop.h"
  
  #define DEFAULT_AUDIO_SAMPLERATE 44100
  
  static uint32_t sampleRates[AUDIO_MAX_SOURCE];
  static uint32_t audioActive; // bitmap of active audio sources
  
  static int highestPriAudio(void)
  {
      int i;
  
      if (audioActive == 0)
          return -1;
  
      return (31 - __builtin_clz(audioActive));
  }
  
  void audioInit(void)
  {
      PMC_EnablePeripheral(ID_PWM);
      PWMC_ConfigureClocks(0, 0, BOARD_MCK);
      PWMC_ConfigureChannel(PWM, 0, PWM_CMR_CPRE_MCK, 0, 0);
      PWMC_ConfigureEventLineMode(PWM, 0, 1);
  
      audioSetSample(AUDIO_NULL, DEFAULT_AUDIO_SAMPLERATE);
  
      PWMC_EnableChannel(PWM, 0);
      PMC_EnablePeripheral(ID_DACC);
      DACC_Initialize(DACC, ID_DACC, 1, 4, 0, 0, BOARD_MCK, 8, DACC_CHANNEL_0, 0, 16 );
      DACC_EnableChannel(DACC, DACC_CHANNEL_0);
  }
  
  void audioOn(int source, uint32_t samplerate)
  {
      audioActive |= (1 << source);
  
      audioSetSample(source, samplerate);
  }
  
  void audioOff(int source)
  {
      int resetsample = 0;
      if (source == highestPriAudio())
          resetsample = 1;
  
      audioActive &= ~(1 << source);
  
      // switch to the new highest priority audio's sample rate
      int highest = highestPriAudio();
      if (resetsample && highest >= 0) {
          audioSetSample(highest, sampleRates[highest]);
      }
  }
  
  void audioSetSample(int source, uint32_t samplerate)
  {
      sampleRates[source] = samplerate;
  
      // if we're not the highest priority audio source, dont set it
      if (source != highestPriAudio())
          return;
  
      samplerate = (BOARD_MCK + samplerate - 1) / samplerate; //err on the side of slower audio
  
      PWMC_SetPeriod(PWM, 0, samplerate);
      PWMC_ConfigureComparisonUnit(PWM, 0, (samplerate + 1) >> 1, 1);
  }
  
  void audioAddBuffer(int source, const uint16_t* samples, uint32_t numSamples)
  {
      // see if we're the highest priority audio, drop on the floor if we're not
      if (source != highestPriAudio())
          return;
  
      while(!DACC_WriteBuffer(DACC, samples, numSamples)) coopYield();
  }
  
  int audioTryAddBuffer(int source, const uint16_t* samples, uint32_t numSamples)
  {
      // see if we're the highest priority audio, drop on the floor if we're not
      if (source != highestPriAudio())
          return 1; // pretend we queued
  
      int first_free = (DACC->DACC_TCR == 0) && (DACC->DACC_TNCR == 0);
  
      uint32_t res = DACC_WriteBuffer(DACC, samples, numSamples);
  
      if (!res)
          return 0;
  
      if (first_free)
          return 1;
      else
          return DACC->DACC_TCR;
  }
  
  